U.S. patent application number 14/075034 was filed with the patent office on 2014-05-08 for hydroformed driveshaft tube with secondary shape.
The applicant listed for this patent is DANA AUTOMOTIVE SYSTEMS GROUP, LLC. Invention is credited to Jeffrey A. Dutkiewicz, Ryan W. Laskey.
Application Number | 20140128168 14/075034 |
Document ID | / |
Family ID | 49641871 |
Filed Date | 2014-05-08 |
United States Patent
Application |
20140128168 |
Kind Code |
A1 |
Laskey; Ryan W. ; et
al. |
May 8, 2014 |
HYDROFORMED DRIVESHAFT TUBE WITH SECONDARY SHAPE
Abstract
A hydroformed driveshaft tube formed using a hydroforming
process is provided. The hydroformed driveshaft tube comprises a
first end portion, a second end portion, and a middle portion. The
middle portion is at least partially defined by a circular arc
shaped surface of revolution. At least a portion of the middle
portion has a diameter greater than a diameter of the first end
portion and the second end portion. The middle portion is formed
between the first end portion and the second end portion. The
middle portion affects a critical speed and a breathing mode
frequency of the hydroformed driveshaft tube. The hydroformed
driveshaft tube reduces a cost of a driveshaft assembly.
Inventors: |
Laskey; Ryan W.;
(Lambertville, MI) ; Dutkiewicz; Jeffrey A.;
(Toledo, OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DANA AUTOMOTIVE SYSTEMS GROUP, LLC |
Maumee |
OH |
US |
|
|
Family ID: |
49641871 |
Appl. No.: |
14/075034 |
Filed: |
November 8, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61724154 |
Nov 8, 2012 |
|
|
|
Current U.S.
Class: |
464/183 |
Current CPC
Class: |
Y10T 464/50 20150115;
B21D 26/033 20130101; F16C 3/02 20130101; B21D 53/84 20130101; F16F
15/322 20130101 |
Class at
Publication: |
464/183 |
International
Class: |
F16C 3/02 20060101
F16C003/02 |
Claims
1. A hydroformed driveshaft tube, comprising: a first end portion;
a second end portion; and a middle portion at least partially
defined by a circular arc shaped surface of revolution and at least
a portion of the middle portion having a diameter greater than a
diameter of the first end portion and the second end portion,
wherein the middle portion is formed between the first end portion
and the second end portion and the middle portion affects a
critical speed and a breathing mode frequency of the hydroformed
driveshaft tube.
2. The hydroformed driveshaft tube according to claim 1, wherein
the middle portion comprises a first distension, a constriction,
and a second distension, the constriction formed between the first
distension and the second distension.
3. The hydroformed driveshaft tube according to claim 2, further
comprising a first tangential transition and a second tangential
transition, the first tangential transition formed between the
first end portion and the first distension and the second
tangential transition formed between the second end portion and the
second distension.
4. The hydroformed driveshaft tube according to claim 3, further
comprising a third tangential transition and a fourth tangential
transition, the third tangential transition formed between the
constriction and the first distension and the fourth tangential
transition formed between the constriction and the second
distension.
5. The hydroformed driveshaft tube according to claim 2, wherein at
least one of the first distension and the second distension is
defined by the circular arc shaped surface of revolution, the
circular arc shaped surface of revolution having a radius about 40
times greater than a radius of the first end portion and the second
end portion.
6. The hydroformed driveshaft tube according to claim 2, wherein a
concavity of the constriction is opposite a concavity of the first
distension and the second distension.
7. The hydroformed driveshaft tube according to claim 2, wherein
the constriction provides a datum to militate against tube buckling
which may occur during a hydroforming process used to form the
hydroformed driveshaft tube.
8. The hydroformed driveshaft tube according to claim 1, further
comprising a first transition portion, a first constriction
portion, a second constriction portion, and a second transition
portion, the middle portion formed between the first constriction
portion and the second constriction portion.
9. The hydroformed driveshaft tube according to claim 8, wherein
the circular arc shaped surface of revolution corresponds in shape
to the first transition portion, the middle portion, and the second
transition portion.
10. The hydroformed driveshaft tube according to claim 9, wherein
the circular arc shaped surface of revolution has a radius about
150 times greater than a radius of the first end portion and the
second end portion.
11. The hydroformed driveshaft tube according to claim 8, wherein a
concavity of the first constriction and the second constriction is
opposite a concavity of the first transition portion, the middle
portion, and the second transition portion.
12. The hydroformed driveshaft tube according to claim 8, wherein
the first constriction and the second constriction each provide a
datum to militate against tube buckling which may occur during a
hydroforming process used to form the hydroformed driveshaft
tube.
13. The hydroformed driveshaft tube according to claim 8, wherein a
diameter of the first constriction and the second constriction is
greater than the diameter of the first end portion and the second
end portion.
14. The hydroformed driveshaft tube according to claim 1, wherein
the circular arc shaped surface of revolution has a radius about
200 times greater than a radius of the first end portion and the
second end portion.
15. A hydroformed driveshaft tube, comprising: a first end portion;
a second end portion; and a middle portion at least partially
defined by a circular arc shaped surface of revolution and at least
a portion of the middle portion having a diameter greater than a
diameter of the first end portion and the second end portion, the
middle portion comprising a first distension, a constriction, and a
second distension, wherein the middle portion is formed between the
first end portion and the second end portion, the constriction is
formed between the first distension and the second distension, and
the middle portion affects a critical speed and a breathing mode
frequency of the hydroformed driveshaft tube.
16. The hydroformed driveshaft tube according to claim 15, further
comprising a first tangential transition and a second tangential
transition, the first tangential transition formed between the
first end portion and the first distension and the second
tangential transition formed between the second end portion and the
second distension.
17. The hydroformed driveshaft tube according to claim 16, further
comprising a third tangential transition and a fourth tangential
transition, the third tangential transition formed between the
constriction and the first distension and the fourth tangential
transition formed between the constriction and the second
distension.
18. The hydroformed driveshaft tube according to claim 15, wherein
at least one of the first distension and the second distension is
defined by the circular arc shaped surface of revolution, the
circular arc shaped surface of revolution having a radius about 40
times greater than a radius of the first end portion and the second
end portion.
19. A hydroformed driveshaft tube, comprising: a first end portion;
a second end portion; and a middle portion at least partially
defined by a circular arc shaped surface of revolution and at least
a portion of the middle portion having a diameter greater than a
diameter of the first end portion and the second end portion, the
middle portion comprising a first transition portion, a first
constriction portion, a second constriction portion, and a second
transition portion, wherein the middle portion is formed between
the first constriction portion and the second constriction portion
and the middle portion affects a critical speed and a breathing
mode frequency of the hydroformed driveshaft tube.
20. The hydroformed driveshaft tube according to claim 19, wherein
the circular arc shaped surface of revolution corresponds in shape
to the first transition portion, the middle portion, and the second
transition portion.
Description
CLAIM OF PRIORITY
[0001] The present application claims the benefit of priority to
U.S. Provisional Application No. 61/724,154 filed on Nov. 8, 2012,
which is incorporated herein in its entirety by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to driveshafts and more
specifically to driveshafts for vehicle formed using a hydroforming
process.
BACKGROUND OF THE INVENTION
[0003] Rotation of a driveshaft at or near a resonating frequency
of the driveshaft may lead to an undesired vibration of the
driveshaft. Further, rotation of a driveshaft which is unbalanced
may also lead to the undesired vibration of the driveshaft,
resulting in customer dissatisfaction. Rotation of the driveshaft
with the undesired vibration, regardless of its source, may also
lead to excessive wear of a plurality of components of the
driveshaft. Center bearings, shaft end components (such as yokes),
universal joint crosses, needle bearings, and a tubular portion of
the driveshaft may all be excessively worn by the undesired
vibration of the driveshaft.
[0004] Typically, as a length of the driveshaft increases, the
resonating frequency decreases. In vehicles having long lengths of
driveshaft between a vehicle powertrain and a drive axle, such as
commercial trucks, the resonating frequency of the driveshaft may
approach an operational speed of the driveshaft. To relieve the
undesired vibration, the driveshaft may comprise a plurality of
sections joined by joints. Unfortunately, adding joints to the
driveshaft greatly increases a cost and a weight of the driveshaft,
and thus a vehicle the driveshaft is incorporated in.
[0005] Alternately, to relieve the undesired vibration, the
diameter of the driveshaft, and thus a diameter of the shaft end
components, may be increased. However, increasing the diameter of
the driveshaft and the diameter of the shaft end components also
greatly increases the cost of the driveshaft, and thus the vehicle
the driveshaft is incorporated in.
[0006] Following manufacture of the driveshaft but prior to
installation of the driveshaft in the vehicle, the driveshaft is
typically balanced. Through the use of a dynamic balancing machine,
a mass and a location of a balancing weight on the driveshaft is
determined. After application of the balancing weight, the
driveshaft is substantially balanced, reducing the undesired
vibration of the driveshaft during operation. However, balancing of
the driveshaft increases a time of manufacture of the driveshaft
and therefore increases the cost of the driveshaft, and thus the
vehicle the driveshaft is incorporated in.
[0007] The driveshaft formed from aluminum reduces the weight of
the driveshaft. Where formed using a hydroforming process, the
driveshaft has an increased resonating frequency and a decreased
manufacturing cost. Consequently, the driveshaft formed from
aluminum using the hydroforming process is advantageous over the
driveshaft formed from a steel using the hydroforming process.
However, conventional methods used to hydroform driveshafts as
applied to aluminum have been unsuccessful, as a maximum strain
limit for forming aluminum is less than a maximum strain limit for
forming steel.
[0008] It would be advantageous to develop a driveshaft that may be
formed using a hydroforming process, reduces a cost of the
driveshaft, and has an increased critical speed.
SUMMARY OF THE INVENTION
[0009] Presently provided by the invention, a driveshaft that may
be formed using a hydroforming process, reduces a cost of the
driveshaft, and has an increased critical speed, has surprisingly
been discovered.
[0010] In one embodiment, the present invention is directed to a
hydroformed driveshaft tube. The hydroformed driveshaft tube
comprises a first end portion, a second end portion, and a middle
portion. The middle portion is at least partially defined by a
circular arc shaped surface of revolution. At least a portion of
the middle portion has a diameter greater than a diameter of the
first end portion and the second end portion. The middle portion is
formed between the first end portion and the second end portion.
The middle portion affects a critical speed and a breathing mode
frequency of the hydroformed driveshaft tube.
[0011] In another embodiment, the present invention is directed to
a hydroformed driveshaft tube. The hydroformed driveshaft tube
comprises a first end portion, a second end portion, and a middle
portion. The middle portion is at least partially defined by a
circular arc shaped surface of revolution. At least a portion of
the middle portion has a diameter greater than a diameter of the
first end portion and the second end portion. The middle portion
comprises a first distension, a constriction, and a second
distension. The middle portion is formed between the first end
portion and the second end portion. The constriction is formed
between the first distension and the second distension. The middle
portion affects a critical speed and a breathing mode frequency of
the hydroformed driveshaft tube.
[0012] In another embodiment, the present invention is directed to
a hydroformed driveshaft tube. The hydroformed driveshaft tube
comprises a first end portion, a second end portion, and a middle
portion. The middle portion is at least partially defined by a
circular arc shaped surface of revolution. At least a portion of
the middle portion has a diameter greater than a diameter of the
first end portion and the second end portion. The middle portion
comprises a first transition portion, a first constriction portion,
a second constriction portion, and a second transition portion. The
middle portion is formed between the first constriction portion and
the second constriction portion. The middle portion affects a
critical speed and a breathing mode frequency of the hydroformed
driveshaft tube.
[0013] Various aspects of this invention will become apparent to
those skilled in the art from the following detailed description of
the preferred embodiment, when read in light of the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The above, as well as other advantages of the present
invention will become readily apparent to those skilled in the art
from the following detailed description when considered in the
light of the accompanying drawings in which:
[0015] FIG. 1A is a perspective view of a driveshaft tube according
to an embodiment of the present invention;
[0016] FIG. 1B is a side plan view of the driveshaft tube
illustrated in FIG. 1A;
[0017] FIG. 2A is a perspective view of a driveshaft tube according
to another embodiment of the present invention;
[0018] FIG. 2B is a side plan view of the driveshaft tube
illustrated in FIG. 2A;
[0019] FIG. 3A is a perspective view of a driveshaft tube according
to another embodiment of the present invention;
[0020] FIG. 3B is a side plan view of the driveshaft tube
illustrated in FIG. 3A;
[0021] FIG. 4 is a table displaying experimental data collected
from straight tubing used as a control, the driveshaft tube
illustrated in FIG. 1A, the driveshaft tube illustrated in FIG. 2A,
and the driveshaft tube illustrated in FIG. 3A;
[0022] FIG. 5 is a bar style chart illustrating a portion of the
experimental data shown in FIG. 4, comparing a critical speed by a
length and a shape of straight tubing used as a control, the
driveshaft tube illustrated in FIG. 1A, the driveshaft tube
illustrated in FIG. 2A, and the driveshaft tube illustrated in FIG.
3A; and
[0023] FIG. 6 is a bar style chart illustrating a portion of the
experimental data shown in FIG. 4, comparing a breathing mode
frequency by a length and a shape of straight tubing used as a
control, the driveshaft tube illustrated in FIG. 1A, the driveshaft
tube illustrated in FIG. 2A, and the driveshaft tube illustrated in
FIG. 3A.
DETAILED DESCRIPTION OF THE INVENTION
[0024] It is to be understood that the invention may assume various
alternative orientations and step sequences, except where expressly
specified to the contrary. It is also to be understood that the
specific devices and processes illustrated in the attached
drawings, and described in the following specification are simply
exemplary embodiments of the inventive concepts defined in the
appended claims. Hence, specific dimensions, directions or other
physical characteristics relating to the embodiments disclosed are
not to be considered as limiting, unless the claims expressly state
otherwise.
[0025] FIGS. 1A and 1B illustrate a first driveshaft tube 100
formed using a hydroforming process. The first driveshaft tube 100
is formed from a 6061 aluminum alloy; however, it is understood
that other alloys may be used. A tubular aluminum blank (not
illustrated) used to form the first driveshaft tube 100 using the
hydroforming process may be formed using an extrusion process or a
seam welding process. The tubular aluminum blank is a cylindrical
aluminum tube.
[0026] The first driveshaft tube 100 includes a first end portion
102, a middle portion 104, and a second end portion 106. Once
fitted with a pair of shaft end components (not shown), the first
driveshaft tube 100 forms a portion of a driveshaft assembly (not
shown) for use with a vehicle.
[0027] The first end portion 102 and the second end portion 106 are
substantially cylindrical in shape and comprise about 13% of a
length of the first driveshaft tube 100, but it, is understood that
other ratios may also be used. A wall thickness of the first end
portion 102 and the second end portion 106 are substantially
constant. The first end portion 102 and the second end portion 106
respectively meet the middle portion 104 at a first tangential
transition 108 and a second tangential transition 110. A radius of
a substantially circular arc of a surface of revolution forming the
first tangential transition 108 and the second tangential
transition 110 is about four times greater than a radius of the
first end portion 102 and the second end portion 106. A shape of
the middle portion 104 is a surface of revolution formed by
rotating a substantially circular arc about an axis of the first
end portion 102 and the second end portion 106. As a non-limiting
example, the substantially circular arc of the surface of
revolution of the middle portion 104 may be defined by an acute
angle of about 4 degrees, but it is understood that other angle may
also be used. Further, a radius of the substantially circular arc
of the surface of revolution of the middle portion 104 is about 200
times greater than a radius of the first end portion 102 and the
second end portion 106, but it is understood that other ratios may
also be used. A wall thickness of the middle portion 104 is not
constant due to the hydroforming process used to form the first
driveshaft tube 100. A thickness of the middle portion 104 at a
thinnest point, at a midpoint of the first driveshaft tube 100, is
about 90% of a thickness of the first end portion 102 and the
second end portion 106, but it is understood that other ratios may
be used. The shape of the middle portion 104 of the first
driveshaft tube 100 may be commonly described as a barrel
shape.
[0028] The first driveshaft tube 100 increases a critical speed or
a first bending mode of the driveshaft having a first length by an
average of approximately 26% when compared to straight tubing used
as a control, the straight tubing having an outer diameter
substantially equal to the diameter of the end portions 102, 106.
The first driveshaft tube 100 increases a critical speed or a first
bending mode of the driveshaft having a second length by an average
of approximately 23% when compared to straight tubing used as a
control, the straight tubing having an outer diameter substantially
equal to the diameter of the end portions 102, 106. The critical
speed of the first driveshaft tube 100 is highly dependent on the
average diameter of the tubing, so with adjustments to the shape of
the forming and percentage of straight tubing forming the first
driveshaft tube 100, this increase in critical speed can be
adjusted.
[0029] It has also been discovered through experimentation that a
breathing mode frequency of the first driveshaft tube 100 is
significantly increased when compared to straight tubing used as a
control, the straight tubing having an outer diameter substantially
equal to a greatest diameter of the middle portion 104. The first
driveshaft tube 100 having a first length offers an increase over
the straight tubing used as a control of about 67%. The first
driveshaft tube 100 having a second length offers an increase over
the straight tubing used as a control of about 72%. Breathing modes
are natural modes of tubing where the circumference of the tube is
bent to a non-perfect circle. As this occurs it acts as an
amplifying agent to any other noises in the vehicle, typically a
whine of a transmission or an axle gear.
[0030] FIGS. 2A and 2B illustrate a second driveshaft tube 200
formed using a hydroforming process. The second driveshaft tube 200
is formed from a 6061 aluminum alloy; however, it is understood
that other alloys may be used. A tubular aluminum blank (not
illustrated) used to form the second driveshaft tube 200 using the
hydroforming process may be formed using an extrusion process or a
seam welding process. The tubular aluminum blank is a cylindrical
aluminum tube.
[0031] The second driveshaft tube 200 includes a first end portion
202, a first transition portion 204, a first constriction portion
206, a middle portion 208, a second constriction portion 210, a
second transition portion 212, and a second end portion 214. Once
fitted with a pair of shaft end components (not shown), the second
driveshaft tube 200 forms a portion of a driveshaft assembly (not
shown) for use with a vehicle.
[0032] The first end portion 202 and the second end portion 214 are
substantially cylindrical in shape and each comprise about 11% of a
length of the second driveshaft tube 200, but it is understood that
other ratios may be used. A wall thickness of the first end portion
202 and the second end portion 214 are substantially constant. The
first end portion 202 and the second end portion 214 respectively
meet the first transition portion 204 and the second transition
portion 212 in a first tangential transition 216 and a second
tangential transition 218. A radius of a substantially circular arc
of a surface of revolution forming the first tangential transition
216 and the second tangential transition 218 is about 4.5 times
greater than a radius of the first end portion 202 and the second
end portion 214.
[0033] A shape of the first transition portion 204, the middle
portion 208, and the second transition portion 212 corresponds in
shape to a surface of revolution formed by rotating a substantially
circular arc about an axis of the first end portion 204 and the
second end portion 214. The first transition portion 204 and the
second transition 212 portion each comprise about 11% of a length
of the second driveshaft tube 200, but it is understood that other
ratios may be used. The middle portion 208 comprises about 40% of a
length of the second driveshaft tube 200, but it is understood that
other ratios may be used. As a non-limiting example, the
substantially circular arc of the surface of revolution
corresponding in shape to the first transition portion 204, the
middle portion 208, and the second transition portion 212 may be
defined by an acute angle of about 7 degrees, but it is understood
that other angles may be used. Further, a radius of the
substantially circular arc of the surface of revolution
corresponding in shape to the first transition portion 204, the
middle portion 208, and the second transition portion 212 is about
150 times greater than a radius of the first end portion 202 and
the second end portion 214, but it is understood that other ratios
may be used. A wall thickness of the middle portion 208 is not
constant due to the hydroforming process used to form the second
driveshaft tube 200. A thickness of the middle portion 208 at a
thinnest point, at a midpoint of the middle portion 208, is about
90% of a thickness of the first end portion 202 and the second end
portion 214, but it is understood that other ratios may be used.
The shape of the first transition portion 204, the middle portion
208, and the second transition portion 212 is divided by the first
constriction portion 206 and the second constriction portion
210.
[0034] The first constriction portion 206 and the second
constriction portion 210 are each a surface of revolution formed by
rotating a substantially circular arc about an axis of the first
end portion 202 and the second end portion 214. As a non-limiting
example, the substantially circular arc of the surface of
revolution of the first constriction portion 206 and the second
constriction portion 210 may each be defined by an acute angle of
about 20 degrees, but it is understood that other angles may be
used. Further, a radius of the substantially circular arc of the
surface of revolution of the first constriction portion 206 and the
second constriction portion 210 is about 4.5 times greater than a
radius of the first end portion 202 and the second end portion 214,
but it is understood that other ratios may be used. A concavity of
the first constriction portion 206 and the second constriction
portion 210 is opposite a concavity of the first transition portion
204, the middle portion 208, and the second transition portion 212.
A wall thickness of the first constriction portion 206 and the
second constriction portion 210 are substantially equal to a
thickness of the first end portion 202 and the second end portion
214. A diameter of the first constriction portion 206 and the
second constriction portion 210 is about 16% greater than a
diameter of the first end portion 202 and the second end portion
214. The first constriction portion 206 respectively tangentially
meets the first transition portion 204 and the middle portion 208
in a third tangential transition 220 and a fourth tangential
transition 222. A radius of a substantially circular arc of a
surface of revolution forming the third tangential transition 220
and the fourth tangential transition 222 is about 4.5 times greater
than a radius of the first end portion 202 and the second end
portion 214. The second constriction portion 210 respectively
tangentially meets the second transition portion 212 and the middle
portion 208 in a fifth tangential transition 224 and a sixth
tangential transition 226. A radius of a substantially circular arc
of a surface of revolution forming the fifth tangential transition
224 and the sixth tangential transition 226 is about 4.5 times
greater than a radius of the first end portion 202 and the second
end portion 214.
[0035] The first constriction portion 206 and the second
constriction portion 210 of the second driveshaft tube 200
respectively provide a tertiary datum 226 and a quaternary datum
228 (in addition to the first end portion 202 and the second end
portion 214) to militate against tube buckling which may occur
during the hydroforming process. As a result, the first
constriction portion 206 and the second constriction portion 210 of
the second driveshaft tube 200 reduce an amount of axial runout
that is generated in the second driveshaft tube 200 during the
hydroforming process. The first constriction portion 206 and the
second constriction portion 210 of the second driveshaft tube 200
are created by a shape of a hydroforming die. The diameter of the
second driveshaft tube 200 at the first constriction portion 206
and the second constriction portion 210 is greater than the
diameter of the first end portion 202 and the second end portion
214, which allow the hydroforming die to secure the second
driveshaft tube 200 with respect to the first end portion 202 and
the second end portion 214 during the hydroforming process.
[0036] The second driveshaft tube 200 increases a critical speed or
a first bending mode of the driveshaft having a first length by an
average of approximately 29% when compared to straight tubing used
as a control, the straight tubing having an outer diameter
substantially equal to the diameter of the end portions 202, 214.
The critical speed of the second driveshaft tube 200 is highly
dependent on the average diameter of the tubing, so with
adjustments to the shape of the forming and percentage of straight
tubing forming the second driveshaft tube 200, this increase in
critical speed can be adjusted.
[0037] It has also been discovered through experimentation that a
breathing mode frequency of the second driveshaft tube 200 is
significantly increased when compared to straight tubing used as a
control, the straight tubing having an outer diameter substantially
equal to a greatest diameter of the middle portion 208. The second
driveshaft tube 200 having a first length offers an increase over
the straight tubing used as a control of about 52%.
[0038] FIGS. 3A and 3B illustrate a third driveshaft tube 300
formed using a hydroforming process. The third driveshaft tube 300
is formed from a 6061 aluminum alloy; however, it is understood
that other alloys may be used. A tubular aluminum blank (not
illustrated) used to form the third driveshaft tube 300 using the
hydroforming process may be formed using an extrusion process or a
seam welding process. The tubular aluminum blank is a cylindrical
aluminum tube.
[0039] The third driveshaft tube 300 includes a first end portion
302, a first distension 304, a constriction 306, a second
distension 308, and a second end portion 310. Once fitted with a
pair of shaft end components (not shown), the third driveshaft tube
300 forms a portion of a driveshaft assembly (not shown) for use
with a vehicle.
[0040] The first end portion 302 and the second end portion 310 are
substantially cylindrical in shape and each comprise about 7% of a
length of the third driveshaft tube 300, but it is understood that
other ratios may be used. A wall thickness of the first end portion
302 and the second end portion 310 are substantially constant. The
first end portion 302 and the second end portion 310 respectively
meets the first distension 304 and the second distension 308 at a
first tangential transition 312 and a second tangential transition
314. A radius of a substantially circular arc of a surface of
revolution forming the first tangential transition 312 and the
second tangential transition 314 is about four times greater than a
radius of the first end portion 302 and the second end portion
310.
[0041] A shape of the first distension 304 is a surface of
revolution formed by rotating a substantially circular arc about an
axis of the first end portion 302 and the second end portion 310.
As a non-limiting example, the substantially circular arc of the
surface of revolution of the first distension 304 may be defined by
an acute angle of about 10 degrees, but it is understood that other
angles may be used. Further, a radius of the substantially circular
arc of the surface of revolution of the first distension 304 is
about 40 times greater than a radius of the first end portion 302
and the second end portion 310, but it is understood that other
ratios may be used. A wall thickness of the first distension 304 is
not constant due to the hydroforming process used to form the third
driveshaft tube 300. A thickness of the first distension 304 at a
thinnest point, at a midpoint of the first distension 304, is about
90% of a thickness of the first end portion 302 and the second end
portion 310, but it is understood that other ratios may be used.
The shape of the first distension 304 of the third driveshaft tube
300 may be commonly described as a barrel shape.
[0042] The constriction 306 is a surface of revolution formed by
rotating a substantially circular arc about an axis of the first
end portion 302 and the second end portion 310. As a non-limiting
example, the substantially circular arc of the surface of
revolution of the constriction 306 may be defined by an acute angle
of about 6 degrees, but it is understood that other angles may be
used. Further, a radius of the substantially circular arc of the
surface of revolution of the constriction 306 is about four times
greater than a radius of the first end portion 302 and the second
end portion 310, but it is understood that other ratios may be
used. A concavity of the constriction 306 is opposite a concavity
of the first distension 304 and the second distension 308. A wall
thickness and a diameter of the constriction 306 are substantially
equal to a thickness and a diameter of the first end portion 302
and the second end portion 310. The constriction 306 respectively
meets the first distension 304 and the second distension 308 at a
third tangential transition 316 and a fourth tangential transition
318. A radius of a substantially circular arc of a surface of
revolution forming each of the third tangential transition 316 and
the fourth tangential transition 318 is about 4 times greater than
a radius of the first end portion 302 and the second end portion
310.
[0043] A shape of the second distension 308 is a surface of
revolution formed by rotating a substantially circular arc about an
axis of the first end portion 302 and the second end portion 310.
As a non-limiting example, the substantially circular arc of the
surface of revolution of the second distension 308 may be defined
by an acute angle of about 10 degrees, but it is understood that
other angles may be used. Further, a radius of the substantially
circular arc of the surface of revolution of the second distension
308 is about 40 times greater than a radius of the first end
portion 302 and the second end portion 310, but it is understood
that other ratios may be used. A wall thickness of the second
distension 308 is not constant due to the hydroforming process used
to form the third driveshaft tube 300. A thickness of the second
distension 308 at a thinnest point, at a midpoint of the second
distension 308, is about 90% of a thickness of the first end
portion 302 and the second end portion 310, but it is understood
that other ratios may be used. The shape of the second distension
308 of the third driveshaft tube 300 may be commonly described as a
barrel shape.
[0044] The constriction 306 of the third driveshaft tube 300
provides a tertiary datum 320 (in addition to the first end portion
302 and the second end portion 310) to militate against tube
buckling which may occur during the hydroforming process. As a
result, the constriction 306 of the third driveshaft tube 300
reduces an amount of axial runout that is generated in the third
driveshaft tube 300 during the hydroforming process. The
constriction 306 of the third driveshaft tube 300 is created by a
shape of a hydroforming die. The diameter of the third driveshaft
tube 300 at the constriction 306 is the same diameter as the first
end portion 302 and the second end portion 310, which allows the
hydroforming die to secure a center of the third driveshaft tube
300 with respect to the first end portion 302 and the second end
portion 310 during the hydroforming process.
[0045] The third driveshaft tube 300 increases a critical speed or
a first bending mode of the driveshaft having a first length by an
average of approximately 22% when compared to straight tubing used
as a control, the straight tubing having an outer diameter
substantially equal to the diameter of the end portions 302, 310.
The third driveshaft tube 300 also increases a critical speed or a
first bending mode of the driveshaft having a second length by an
average of approximately 20% when compared to straight tubing used
as a control, the straight tubing having an outer diameter
substantially equal to the diameter of the end portions 302, 310.
The critical speed of the third driveshaft tube 300 is highly
dependent on the average diameter of the tubing, so with
adjustments to the shape of the forming and percentage of straight
tubing forming the third driveshaft tube 300, this increase in
critical speed can be adjusted.
[0046] It has also been discovered through experimentation that a
breathing mode frequency of the third driveshaft tube 300 is
significantly increased when compared to straight tubing used as a
control, the straight tubing having an outer diameter substantially
equal to a greatest diameter of the distensions 304, 308. The third
driveshaft tube 300 having a first length offers an increase over
the straight tubing used as a control of about 105%. The third
driveshaft tube 300 having a second length offers an increase over
the straight tubing used as a control of about 112%.
[0047] FIG. 4 is a table which includes experimental data collected
from straight tubing used as a control, the first driveshaft tube
100, the second driveshaft tube 200, and the third driveshaft tube
300. The aforementioned results are shown and based upon the
experimental data shown in FIG. 4.
[0048] FIG. 5 is a bar style chart comparing the critical speed by
a length and a shape of straight tubing used as a control (in three
instances), the first driveshaft tube 100, the second driveshaft
tube 200, and the third driveshaft tube 300. The bar style chart
display the experimental data shown in FIG. 4.
[0049] FIG. 6 is a bar style chart comparing the breathing mode by
a length and a shape of straight tubing used as a control (in three
instances), the first driveshaft tube 100, the second driveshaft
tube 200, and the third driveshaft tube 300. The bar style chart
display the experimental data shown in FIG. 4.
[0050] As can be appreciated from FIGS. 4-6, the driveshaft tube
100, 200, 300 has an increased critical speed when compared to
straight tubing used as a control, the straight tubing having an
outer diameter substantially equal to the diameter of the end
portions 102, 106, 202, 214, 302, 310. Such a benefit allows the
driveshaft assembly including the driveshaft tube 100, 200, 300 to
have critical speed characteristics of a driveshaft tube having a
greater diameter than a driveshaft formed from straight tubing
having an outer diameter substantially equal to the diameter of the
end portions 102, 106, 202, 214, 302, 310. The driveshaft assembly
including the driveshaft tube 100, 200, 300 is compatible with
driveshaft end fittings having a reduced diameter, which greatly
reduces a cost of the driveshaft assembly including the driveshaft
tube 100, 200, 300.
[0051] As can be appreciated from FIGS. 4-6, the driveshaft tube
100, 200, 300 has an increased breathing mode frequency when
compared to straight tubing used as a control, the straight tubing
having an outer diameter substantially equal to a greatest diameter
of the middle portion 104, 208 or the distensions 304, 308. Such a
benefit allows the driveshaft assembly including the driveshaft
tube 100, 200, 300 to have breathing mode frequency characteristics
of a driveshaft tube having a reduced diameter, while still
obtaining the critical speed benefits of a driveshaft tube having
an increased diameter.
[0052] In accordance with the provisions of the patent statutes,
the present invention has been described in what is considered to
represent its preferred embodiments. However, it should be noted
that the invention can be practiced otherwise than as specifically
illustrated and described without departing from its spirit or
scope.
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