U.S. patent application number 11/294693 was filed with the patent office on 2006-04-20 for thermal expansion compensation shock absorber.
Invention is credited to Rudi Schurmans.
Application Number | 20060081428 11/294693 |
Document ID | / |
Family ID | 34376121 |
Filed Date | 2006-04-20 |
United States Patent
Application |
20060081428 |
Kind Code |
A1 |
Schurmans; Rudi |
April 20, 2006 |
Thermal expansion compensation shock absorber
Abstract
The present invention provides the art with a shock absorber
which is capable of compensating for the differing thermal
expansion between two materials. The shock absorber in its various
embodiments includes a free floating pressure tube that is able to
expand or contract axially without breaking a seal, a hybrid piston
rod with a shaft of one material that compensates for differing
thermal expansions and a cap of another material that absorbs axial
forces, a unique rod guide assembly with a biasing member that
compensates for differing thermal expansions, and a unique cylinder
end assembly with a biasing member made from springs, a rubber
block, or pressurized gas.
Inventors: |
Schurmans; Rudi;
(Woutervelo, BE) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Family ID: |
34376121 |
Appl. No.: |
11/294693 |
Filed: |
December 5, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10671354 |
Sep 25, 2003 |
7004293 |
|
|
11294693 |
Dec 5, 2005 |
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Current U.S.
Class: |
188/276 ;
188/322.19 |
Current CPC
Class: |
F16F 9/52 20130101; F16F
9/062 20130101; F16F 9/3242 20130101; F16F 9/366 20130101 |
Class at
Publication: |
188/276 ;
188/322.19 |
International
Class: |
F16F 9/52 20060101
F16F009/52 |
Claims
1. A shock absorber which compensates for thermal expansion, said
shock absorber comprising: a rod guide; a pressure tube forming a
compression chamber, said pressure tube slidingly engaging said rod
guide; a piston slidably disposed within said compression chamber;
a piston rod connected to said piston; a reserve tube disposed
around said pressure tube, said reserve tube and said pressure tube
defining a fluid reservoir; and a cylinder end assembly disposed
between said compression chamber and said fluid reservoir for
controlling the flow of fluid between said compression chamber and
said fluid reservoir, said pressure tube slidingly engaging said
cylinder end assembly: said floating pressure tube being able to
move freely relative to said rod guide and said cylinder between a
first position engaging said rod guide and a second position
engaging said cylinder end assembly.
2. The shock absorber according to claim 1, wherein said pressure
tube slidingly engages said cylinder end assembly.
3. The shock absorber according to claim 1, wherein said pressure
tube slidingly engages said rod guide assembly.
4. The shock absorber according to claim 3, wherein said pressure
tube slidingly engages said cylinder end assembly.
5. A shock absorber which compensates for thermal expansion, said
shock absorber comprising: a pressure tube forming a compression
chamber; a piston slidably disposed within said compression
chamber; a piston rod connected to said piston; a reserve tube
disposed around said pressure tube, said reserve tube and said
pressure tube defining a fluid reservoir; a base valve assembly
disposed between said compression chamber and said fluid reservoir
for controlling the flow of fluid between said compression chamber
and said fluid reservoir; and a biasing member disposed between
said pressure tube and said base valve assembly for urging said
pressure tube away from said base valve assembly.
6. The shock absorber according to claim 5, wherein said biasing
member is a Belleville spring.
7. The shock absorber according to claim 6, wherein said Belleville
spring is secured to said base valve assembly by a circle-clip.
8. The shock absorber according to claim 6, wherein said spring is
secured to said base valve assembly by a spring retainer.
9. The shock absorber according to claim 6, wherein said spring is
disposed between two radial retainers secured to the base valve
assembly.
10. The shock absorber according to claim 5, wherein said base
valve assembly has two portions, a top portion connected to said
pressure tube and a bottom portion connected to said reserve tube,
said top portion slidingly engaging said bottom portion.
11. The shock absorber according to claim 10, wherein said biasing
member is disposed between said top portion and said bottom
portion.
12. The shock absorber according to claim 5, wherein said biasing
member and one end of said pressure tube are disposed within said
base valve assembly.
13. A shock absorber which compensates for thermal expansion, said
shock absorber comprising: a pressure tube forming a compression
chamber; a piston slidably disposed within said compression
chamber; a piston rod connected to said piston; a reserve tube
disposed around said pressure tube, said reserve tube and said
pressure tube defining a fluid reservoir; a base valve assembly
disposed between said compression chamber and said fluid reservoir
for controlling the flow of fluid between said compression chamber
and said fluid reservoir; a base plate slidingly engaging said
reserve tube adjacent said base valve assembly; and a biasing
member disposed between said base plate and an end of said reserve
tube for urging said base plate away from said end of said reserve
tube.
14. The shock absorber according to claim 13, wherein said biasing
member is a Belleville spring.
15. The shock absorber according to claim 13, wherein said biasing
member is an elastomeric block.
16. The shock absorber according to claim 13, wherein said biasing
member is a pressurized gas.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 10/671,354 filed on Sep. 25, 2003. The disclosure of the
above application is incorporated herein by reference.
FIELD OF THE INVENTION
[0002] Hydraulic dampers, such as shock absorbers, are used in
connection with motor vehicle suspension systems to absorb unwanted
vibrations which occur during the operation of the motor vehicle.
The unwanted vibrations are dampened by shock absorbers which are
generally connected between the sprung portion (i.e., the vehicle
body) and the unsprung portion (i.e., the suspension) of the motor
vehicle. A piston assembly is located within the compression
chamber of the shock absorber and is usually connected to the body
of the motor vehicle through a piston rod. The piston assembly
includes a valving arrangement that is able to limit the flow of
damping fluid within the compression chamber when the shock
absorber is compressed or extended. As such, the shock absorber is
able to generate a damping force which "smooths" or "dampens" the
vibrations transmitted between the suspension and the vehicle
body.
[0003] A prior art thermal expansion compensating twin tube shock
absorber 100 is shown in FIG. 1. Shock absorber 100 comprises an
elongated pressure tube 102 provided for defining a hydraulic fluid
containing compression chamber 104 and an elongated reserve tube
106 provided for defining a hydraulic fluid containing reservoir
108.
[0004] Disposed within compression chamber 104 is a reciprocal
piston assembly 110 that is secured to one end of an axially
extending piston rod 112. Piston rod 112 is supported and guided
for movement within pressure tube 102 by means of a combination
seal and rod guide assembly 114 located at the upper end of
pressure tube 102 and having a centrally extending bore 116 through
which piston rod 112 is reciprocally movable. Disposed within bore
116 between rod guide assembly 114 and piston rod 112 is a bushing
118 which is used to facilitate movement of piston rod 112 with
respect to rod guide assembly 114.
[0005] A compliant cylinder end assembly, generally designated at
120, is located at the lower end of pressure tube 102. The
compliant cylinder end assembly 120 includes a base valve assembly
122 that functions to control the flow of hydraulic fluid between
compression chamber 104 and fluid reservoir 108 as well as biasing
member 124 that compensates for the differing axial thermal
expansion between the various components of shock absorber 100.
Fluid reservoir 108 is defined as the space between the outer
peripheral surface of pressure tube 102 and the inner peripheral
surface of reserve tube 106.
[0006] The upper and lower ends of shock absorber 100 are adapted
for assembly into a motor vehicle. Piston rod 112 is shown having a
threaded portion 126 for securing the upper end of shock absorber
100 to the motor vehicle while reserve tube 106 is shown
incorporating a flange 128 having a pair of mounting holes 130 for
securing the lower end of shock absorber 100 to the motor vehicle
(McPherson strut configuration). While shock absorber 100 is shown
in a McPherson strut configuration having threaded portion 126 and
flange 128 for securing it between the sprung and unsprung portions
of the motor vehicle, it is to be understood that this is merely
exemplary in nature and is only intended to illustrate one type of
system for securing shock absorber 100 to the motor vehicle. As
will be appreciated by those skilled in the art, upon reciprocal
movement of piston rod 112 and piston assembly 110, hydraulic fluid
with compression chamber 104 will be transferred between an upper
portion 132 and a lower portion 134 of compression chamber 104 as
well as between compression chamber 104 and fluid reservoir 108
through valve assembly 122 for damping relative movement between
the sprung portion and the unsprung portion of the motor
vehicle.
[0007] This quick exchange of hydraulic fluid through valve
assembly 122 and piston assembly 110 as well as the friction
between piston assembly 110 and pressure tube 102 and the friction
between piston rod 112 and rode guide 114 generates heat which is
undesirable during prolonged operating conditions.
[0008] In addition to absorbing the heat generated while providing
the damping function for the motor vehicle, shock absorber 100 is
also required to operate over a broad range of temperatures ranging
from severe cold temperatures of the winter months to the extremely
hot temperatures of the summer months. Prior art shock absorbers
are manufactured using steel for pressure tube 102 and reserve tube
106. While steel has been proven to be an acceptable material for
these components, tubes manufactured from aluminum offer the
advantages of weight savings as well as improved heat dissipation.
If the typical pressure tube 102 were manufactured from steel while
reservoir tube 106 were manufactured from aluminum, the difference
in their relative axial thermal expansion rates may present
problems for the shock absorber when operating over the necessary
temperature extremes. Specifically, structural failure may occur
under extreme cold temperatures or loss of pressure tube preload
and sealing may occur under extreme hot temperatures.
[0009] Accordingly, continued development of shock absorbers with
aluminum tubes includes the further development of methods to
compensate for differing thermal expansion between aluminum and
steel as well as the differing thermal expansion between any other
two materials.
SUMMARY OF THE INVENTION
[0010] The present invention provides the art with a shock absorber
which is capable of compensating for the differing thermal
expansion between two materials and thus eliminating the
possibility of structural failure due to extreme cold temperatures
as well as the possibility of pressure tube preload loss and
sealing failure under extreme hot temperatures.
[0011] In one embodiment of the present invention, the shock
absorber includes a free floating pressure tube that is capable of
compensating for differing thermal expansion by freely moving
between the rod guide assembly and the valve assembly.
[0012] In another embodiment of the present invention, a unique
piston rod is provided that includes an aluminum rod that
eliminates the difference in thermal expansions. The rod has a
steel cap that absorbs compression forces.
[0013] In another embodiment of the present invention, a unique
compensating rod guide assembly is provided that includes a thermal
compensation element capable of compensating for the differing
thermal expansion between the pressure tube and the reserve
tube.
[0014] In still another embodiment of the present invention, a
unique compensating cylinder end assembly is provided that includes
a thermal compensation element, and the means for securing the
element to the valve assembly. This compensating element is either
a spring, an elastomeric block, or gas pressure.
[0015] Other advantages and objects of the present invention will
become apparent to those skilled in the art from the subsequent
detailed description, appended claims and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] In the drawings which illustrate the best mode presently
contemplated for carrying out the present invention:
[0017] FIG. 1 is a longitudinal cross-sectional view through a
prior art thermal expansion compensating shock absorber;
[0018] FIG. 2 is a longitudinal cross-sectional view of a shock
absorber incorporating a floating pressure tube;
[0019] FIG. 3 is a side view of a unique aluminum piston rod with a
steel cap;
[0020] FIG. 4 is an enlarged side view of a threaded steel cap;
[0021] FIG. 5 is an enlarged side view of a bonded steel cap;
[0022] FIG. 6 is an enlarged cross-sectional view of a compensating
rod guide assembly with Belleville springs;
[0023] FIG. 7 is an enlarged cross-sectional view of a compensating
rod guide assembly with a bearing bush retainer;
[0024] FIG. 8 is an enlarged cross-sectional view of an alternate
compensating rod guide assembly with a bearing bush retainer;
[0025] FIG. 9 is an enlarged cross-sectional view of a compensating
rod guide assembly with a retainer;
[0026] FIG. 10 is an enlarged cross-sectional view of a
compensating cylinder end assembly with Belleville springs;
[0027] FIG. 11 is an enlarged cross-sectional view of the
compensating cylinder end assembly of FIG. 10 illustrating a
circle-clip and retainer support for the compensating member;
[0028] FIG. 12 is an enlarged cross-sectional view of the
compensating cylinder end assembly of FIG. 10 illustrating a spring
retainer for the compensating member;
[0029] FIG. 13 is an enlarged cross-sectional view of the
compensating cylinder end assembly of FIG. 10 illustrating a double
ring retainer for a compensating member;
[0030] FIG. 14 is an enlarged cross-sectional view of an alternate
compensating cylinder end assembly having a two piece end assembly
that sandwiches the compensating member;
[0031] FIG. 15 is an enlarged cross-sectional view of an alternate
compensating cylinder end assembly illustrating the pressure tube
and compensating member disposed within the valve assembly;
[0032] FIG. 16 is an enlarged cross-sectional view of a
compensating cylinder end assembly with Belleville springs at the
base;
[0033] FIG. 17 is an enlarged cross-sectional view of a
compensating cylinder end assembly with an elastomeric block at the
base;
[0034] FIG. 18 is an enlarged cross-sectional view of a
compensating cylinder end assembly with gas pressure at the base;
and
[0035] FIG. 19 is an enlarged cross-sectional view of an alternate
compensating cylinder end assembly with gas pressure at the
base.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0036] Continued reference is made generally to FIG. 1 and
specifically to the components of shock absorber 100 throughout the
subsequent description. It is to be understood that the
construction of shock absorber 100 is merely exemplary in nature
and is only intended to illustrate one type of hydraulic damping
apparatus within which the compensating elements of the present
invention can be utilized.
[0037] Referring now to the drawings in which like reference
numerals designate like or corresponding parts throughout the
several views, there is shown in FIG. 2 a unique compensating shock
absorber 200 having a floating pressure tube 202 and a base valve
assembly 222. Rod guide assembly 114 and base valve assembly 222
are mechanically secured to reserve tube 106. As the relative
length of reserve tube 106 changes due to thermal conditions, the
relative distance between rod guide assembly 114 and base valve
assembly 222 changes. In the prior art, pressure tube 102 is fixed
at one end to one portion of rod guide assembly 114 and at the
other end to base valve assembly 122, such that changes in the
length of pressure tube 102 due to thermal conditions were
compensated for using a multi-piece valve assembly 122. In this
embodiment of the present invention, a floating pressure tube 202
replaces pressure tube 102 of the prior art in order to compensate
for the different thermal expansions of reserve tube 106 and
floating pressure tube 202. Floating pressure tube 202 is sealed to
rod guide assembly 114 and base valve assembly 222 using O-rings
204. Floating pressure tube 202 is able to move freely between rod
guide assembly 114 and base valve assembly 222 as the relative
length of reserve tube 106 changes. Thus, both a standard valve
guide assembly and a standard base valve assembly can be easily
modified to accept floating pressure tube 202.
[0038] In another embodiment of prior art shock absorber 100, a
hybrid piston rod 312 replaces the prior art piston rod 112 as
shown in FIGS. 3-5. Typically the prior art piston rod 112 is made
from steel while rod guide assembly 114 is made from aluminum.
Under extreme thermal conditions the seal between piston rod 112
and rod guide 114 can be broken by the different thermal expansion
of the two materials. Hybrid piston rod 312 includes an aluminum
piston shaft 314 and a steel piston post 316. As shown in FIG. 4,
piston post 316 includes an internal bore 318 which slidingly
receives the end of piston shaft 314. A circle-clip 320 retains the
assembly of piston post 316 and piston shaft 316. As shown in an
alternative embodiment in FIG. 4, piston post 316 has an open
threaded bore 322 for receiving a threaded end of piston shaft 314.
Piston post 316 may be threaded on to piston shaft 314.
Alternatively, as seen in FIG. 5, a modified steel piston post 330
with a flat end 332 may be adhesively secured to the end of piston
shaft 314. In operation, aluminum piston shaft 314 expands and
contracts at the same rate as aluminum rod guide assembly 114 and
thus prevents a break in the seal between the two. Steel piston
post 316, or alternately modified steel piston post 320, absorbs
the axial force on piston rod 312 when shock absorber 100 is in
compression.
[0039] In still another embodiment of prior art shock absorber 100,
various compensating piston rod guide assemblies are shown in FIGS.
6-9. The compensating piston rod guide assembly 414, as shown in
FIG. 6, supports and guides the movement of piston rod 112 and also
compensates for the different thermal expansion of pressure tube
102 and reserve tube 106. Compensating piston rod guide assembly
414 includes bore 116 and bushing 118, as well as a plurality, an
even number in the preferred embodiment, of Belleville springs 424
disposed between rod guide 414 and pressure tube 102. The
difference in thermal expansion between steel pressure tube 102 and
aluminum reserve tube 106 is compensated for by the increase or
decrease in the compensation of Belleville springs 424.
[0040] On the left side of FIG. 7, an alternate compensating piston
rod guide 414' is shown. Alternate piston rod guide 414' includes a
bearing bush retainer 450 disposed between Belleville springs 424
and rod guide 414'. Bearing bush retainer 450 seals rod guide 414'
and pressure tube 102 and retains bushing 118, and is further
designed to support Belleville springs 424. The thermal expansion
of pressure tube 102 is directly compensated for by Belleville
springs 424. On the right side of FIG. 7, piston rod guide 414' is
shown with bearing bush retainer 450 being replaced by compensation
retainer 450'. Compensation retainer 450' functions the same as
bearing bush retainer 450 in that it retains bushing 118 and it is
designed to support Belleville springs 424. The thermal expansion
is directly compensated for by Belleville springs 424.
[0041] In another embodiment, a compensating piston rod guide 414''
is shown on the left side of FIG. 8, wherein bearing bush retainer
452 is disposed between the pressure tube 102 and Belleville
springs 424. Bearing bush retainer 452 is similar to bearing bush
retainer 450 in that it seals rod guide 414'' and pressure tube 102
and it supports Belleville springs 424. The difference between
bearing bush retainer 452 and 450 is that Belleville springs 424
are disposed between rod guide 414'' and bearing bush 452 instead
of between bearing bush retainer 450 and pressure tube 102 as shown
in FIG. 7. The thermal expansion is directly compensated for by
Belleville springs 424. On the right side of FIG. 8, piston rod
guide 414'' is shown with bearing bush retainer 452 being replaced
by compensation retainer 452'. Compensation retainer 450' functions
the same as bearing bush retainer 452' in that it retains bushing
118 and it is designed to support Belleville springs 424 with
Belleville springs 424 being disposed between rod guide 414'' and
bush retainer 452'. The thermal expansion is directly compensated
for by Belleville springs 424.
[0042] In still another embodiment, a compensating piston rod guide
414''' is shown in FIG. 9, wherein bearing bush retainer 452 has
been replaced by a compensation spring support 460. Spring support
460 acts to support Belleville springs 424 but it does not retain
bushing 118. Belleville springs 424 are disposed between rod guide
414''' and spring support 460. The thermal expansion is directly
compensated for by Belleville springs 424.
[0043] In yet further embodiments of prior art shock absorber 100,
various compensating cylinder end assemblies are shown in FIGS.
10-19. In FIG. 10, a compensating cylinder end assembly, generally
designated as 520, is located at the lower end of pressure tube 102
and functions to control the flow of hydraulic fluid between
compression chamber 104 and fluid reservoir 108. Compensating end
assembly 520 further acts to compensate for the differing axial
thermal expansion between the various components of shock absorber
100.
[0044] In FIG. 10, compensating cylinder end assembly 520 includes
a base valve assembly 522 and a plurality, an even number in the
preferred embodiment, of Belleville springs 524 disposed between
pressure tube 102 and base valve assembly 522. The difference in
thermal expansion between the steel pressure tube 102 and the
aluminum reserve tube 106 is compensated for by the increase or
decrease in the compression of Belleville springs 524. This
embodiment differs from the prior art shown in FIG. 1 by
eliminating the need for the multi-piece base valve assembly 122
shown in FIG. 1.
[0045] Various methods for securing Belleville springs 524 to an
end assembly are shown in FIGS. 11-14. In FIG. 11, the compensating
cylinder end assembly 520' includes a reaction ring 550. Reaction
ring 550 is retained to the outside of pressure tube 102 by a
circle-clip 552. Belleville springs 524 are disposed between ring
550 and compression valve assembly 522.
[0046] In FIG. 12, a compensating cylinder end assembly 520''
includes an S-shaped spring retainer 560. Spring retainer 560 is
positioned between the bottom of pressure tube 102 and the top of
Belleville springs 524, and acts to retain Belleville springs 524
between spring retainer 560 and valve assembly 522.
[0047] In FIG. 13, the compensating cylinder end assembly 520'''
includes a first retaining ring 570 and a second retaining ring
572. First retaining ring 570 is positioned such that it is in
contact with the bottom of pressure tube 102. Second retaining ring
572 is secured to valve assembly 522. Belleville springs 524 are
disposed between first retaining ring 570 and second retaining ring
572.
[0048] In FIG. 14, an alternate compensating cylinder end base
valve assembly is designated at 620. Compensating end base valve
assembly 620 is divided into two portions, an upper portion 650 and
a lower portion 652, and includes a plurality of Belleville springs
624 disposed between the two portions 650 and 652. Upper portion
650 is connected to pressure tube 102 and lower portion 652 is
connected to or abuts reserve tube 106. Upper portion 650 fits
within lower portion 652 and is sealed by an O-ring 654. Belleville
springs 624 are disposed between the two portions 650, 652 and act
to compensate for the different thermal expansion of pressure tube
102 and reserve tube 106 by moving upper portion 650 and lower
portion 652 towards or away from each other.
[0049] In FIG. 15, an alternate compensating cylinder end assembly
is designated at 720. Cylinder end assembly 720 includes a base
valve assembly 722 having a cylindrical wall 750 and a plurality of
Belleville springs 724. Cylindrical wall 750 is connected to and
surrounds a base valve assembly 722 and further extends towards the
opposite end of shock absorber 100. Pressure tube 102 slides within
cylindrical wall 750, and is sealed by an O-ring 752. Belleville
springs 724 are disposed between pressure tube 102 and valve
assembly 722 within cylindrical wall 750.
[0050] In another embodiment of shock absorber 100, compensating
cylinder end assembly 820 is shown in FIG. 16. Compensating end
assembly 820 includes a base valve assembly 822, a plurality of
Belleville springs 824, a base plate 850, an O-ring 852, and a
bottom retainer 854. Base plate 850 is capable of moving axially
and is sealed to reserve tube 106 by O-ring 852. Bottom retainer
854 is fixed to reserve tube 106 using a retaining ring 856 and
provides a flat, stable bottom for cylinder end assembly 820.
Belleville springs 824, an even number in the preferred embodiment,
are disposed between base plate 850 and bottom retainer 854.
Belleville springs 824 act to compensate for the different thermal
expansion of the various components of shock absorber 100 through
base plate 850 and bottom retainer 854. In an alternate cylinder
end assembly 820', as shown in FIG. 17, Belleville springs 824 are
replaced with an elastomeric block 860. Elastomeric block 860 is
disposed between base plate 850 and bottom retainer 854 and
compensates for the different thermal expansion of pressure tube
102 and reserve tube 106 by expanding or compressing as
necessary.
[0051] In compressing cylinder end assembly 920, which includes a
base valve assembly 922 as shown in FIG. 18, pressurized gas 950,
for example compressed air, is disposed between a base plate 952
and a bottom retainer 954. Bottom retainer 954 is sealed to reserve
tube 106 by a weld 956 or other means known in the art such that
the gas 950 remains pressurized. Pressurized gas 950 compensates
for the different thermal expansion of pressure tube 102 and
reserve tube 106 by expanding or compressing as necessary, and also
reduces the weight of the shock absorber. In alternate cylinder end
assembly 920' as shown in FIG. 19, bottom retainer 954 has been
removed. Pressurized gas 950 is disposed between base plate 952 and
reserve tube 106 and compensates directly for the different thermal
expansion of the pressure tube 102 and the reserve tube 106.
[0052] While the above detailed description describes the preferred
embodiment of the present invention, it should be understood that
the present invention is susceptible to modification, variation and
alteration without deviating from the scope and fair meaning of the
subjoined claims.
* * * * *