U.S. patent application number 09/826020 was filed with the patent office on 2002-10-10 for apparatus and method for a magneto-rheological (mr) damping device.
This patent application is currently assigned to Delphi Technologies, Inc.. Invention is credited to Ananthanarayanan, Venkatasubramanian, Hopkins, Patrick N., Lisenker, Ilya, Lonbani, Sohrab Sadri, Muhlenkamp, John H..
Application Number | 20020144870 09/826020 |
Document ID | / |
Family ID | 25245485 |
Filed Date | 2002-10-10 |
United States Patent
Application |
20020144870 |
Kind Code |
A1 |
Lonbani, Sohrab Sadri ; et
al. |
October 10, 2002 |
APPARATUS AND METHOD FOR A MAGNETO-RHEOLOGICAL (MR) DAMPING
DEVICE
Abstract
A magneto-rheological damping device comprises a core element
for carrying a magnetic flux and a magnetic flux generator
positioned adjacent to a portion of the core element and operable
to generate a magnetic flux in the core element. A sleeve is
positioned over the core element and magnetic flux generator and
includes a plurality of protrusions extending generally radially
outwardly from a center of the core element. A flux ring surrounds
the core element and sleeve and defining a passage between flux
ring and core element for the flow of a magneto-rheological fluid.
The sleeve protrusions are configured to engage the flux ring and
secure the flux ring in a concentric position around the core
element and sleeve.
Inventors: |
Lonbani, Sohrab Sadri;
(Xenia, OH) ; Muhlenkamp, John H.; (Dayton,
OH) ; Hopkins, Patrick N.; (West Carrollton, OH)
; Lisenker, Ilya; (Miamisburg, OH) ;
Ananthanarayanan, Venkatasubramanian; (Beaver Creek,
OH) |
Correspondence
Address: |
Scott A. McBain, Esq.
Delphi Technologies Inc.
Mail Code 480-414-420
P.O. Box 5052
Troy
MI
48007-5052
US
|
Assignee: |
Delphi Technologies, Inc.
|
Family ID: |
25245485 |
Appl. No.: |
09/826020 |
Filed: |
April 4, 2001 |
Current U.S.
Class: |
188/267 |
Current CPC
Class: |
Y10S 137/909 20130101;
F16F 9/535 20130101 |
Class at
Publication: |
188/267 |
International
Class: |
F16F 015/03 |
Claims
What is claimed is:
1. A magneto-rheological damping device comprising: a core element
for carrying a magnetic flux; a magnetic flux generator positioned
adjacent to a portion of the core element and operable to generate
a magnetic flux in the core element; a sleeve positioned over the
core element and magnetic flux generator, the sleeve including a
plurality of protrusions extending generally radially outwardly
from a center of the core element; a flux ring surrounding the core
element and sleeve and defining a passage between flux ring and
core element for the flow of a magneto-rheological fluid, the flux
ring operable for forming a magnetic circuit and confining a
portion of the magnetic flux proximate the core element and in the
passage; the sleeve protrusions configured to engage the flux ring
and secure the flux ring in a position around the core element and
sleeve.
2. The damping device of claim 1 wherein the sleeve with
protrusions is molded over the core element and magnetic flux
generator.
3. The damping device of claim 1 wherein the protrusions are formed
integrally with the sleeve.
4. The damping device of claim 1 wherein the sleeve and protrusions
are formed of one of a plastic and a ceramic.
5. The damping device of claim 1 wherein the protrusions extend
longitudinally along a portion of a length of the core element.
6. The damping device of claim 1 wherein the protrusions extend
longitudinally generally along the entire length of the core
element.
7. The damping device of claim 1 wherein said protrusions extend
radially outwardly generally an equal distance from the center of
the core element and are operable to secure the flux ring generally
concentrically around the core element and sleeve.
8. The damping device of claim 1 wherein the protrusions are
positioned concentrically around the core in at least three
positions for securing the flux ring.
9. The damping device of claim 1 wherein the flux ring is press fit
onto the sleeve protrusions.
10. The damping device of claim 1 wherein said protrusions have a
triangular cross section.
11. The damping device of claim 1 wherein the magnetic flux
generator includes a wire coil wrapped around the core element.
12. A method of forming a magneto-rheological damping device, the
method comprising: providing a core element for carrying a magnetic
flux; positioning a magnetic flux generator adjacent to a portion
of the core element for generating a magnetic flux in the core
element; positioning a sleeve over the core element and magnetic
flux generator, the sleeve including a plurality of protrusions
extending generally radially outwardly from a center of the core
element; surrounding the core element and sleeve with a flux ring
and defining a passage between flux ring and core element for the
flow of a magneto-rheological fluid, the flux ring operable for
forming a magnetic circuit and confining a portion of the magnetic
flux proximate the core element and in the passage; engaging the
flux ring with the sleeve protrusions and securing the flux ring in
a position around the core element and sleeve.
13. The method of claim 12 further comprising molding the sleeve
and protrusions over the core element and magnetic flux
generator.
14. The method of claim 12 further comprising forming the
protrusions integrally with the sleeve.
15. The method of claim 12 further comprising forming the sleeve
and protrusions with one of a plastic and a ceramic.
16. The method of claim 12 wherein the protrusions extend
longitudinally along a portion of a length of the core.
17. The method of claim 12 wherein the protrusions extend
longitudinally generally along the entire length of the core.
18. The method of claim 12 further comprising wherein said
protrusions extend radially outwardly generally an equal distance
from the center of the core element, the method further comprising
securing the flux ring generally concentrically around the core
element and sleeve with the protrusions.
19. The method of claim 12 wherein the protrusions are positioned
concentrically around the core in at least three positions for
securing the flux ring.
20. The method of claim 12 further comprising press fitting the
flux ring onto the sleeve protrusions.
Description
FIELD OF INVENTION
[0001] This invention relates generally to Magneto-Rheological (MR)
devices and more particularly to an improved design for an MR
damping device.
BACKGROUND OF THE INVENTION
[0002] Devices for suspending parts and controlling or damping
their movement relative to one another, are known in the art. For
example, such devices are known and used in the automotive field in
vehicle suspension systems. The devices might take the form of
shocks, struts and other motion or vibration damping devices.
[0003] Generally, many such devices utilize fluids for controlling
the relative movement of the mechanical parts. For example,
hydraulic fluid may be utilized as a medium for creating damping
forces or torques or controlling motion, shock and vibrations. One
class of such movement control devices utilizes a fluid medium
which has characteristics which are controllable through the use of
magnetic fields and/or magnetic flux. Such magnetically controlled
fluid is referred to as magneto-rheological, or MR, fluid and is
comprised of small, soft magnetic particles dispersed within a
liquid carrier. The particles are often generally round, and the
suitable liquid carrier fluids include hydraulic oils and the like
for suspending the particles. MR fluids exhibit a thickening
behavior (a rheology change), often referred to as "apparent
viscosity change," upon being exposed to magnetic fields of
sufficient strength. The higher the magnetic field strength to
which the MR fluid is exposed, the higher the flow restriction or
damping force that can be achieved in the MR device, and vice
versa. That is, the flow properties of MR fluids may be selectively
altered by magnetic fields.
[0004] A typical MR damping device, for example, utilizes an iron
core structure disposed within or surrounded by a metal cylinder or
casing. MR fluid is positioned to flow between the core and the
metal cylinder. The damping effect of the device is due to the
relative movement of the core and cylinder with respect to the MR
fluid or vice versa. That is, depending upon the use and structure
of the MR damping device, the core and cylinder are dynamic and
move through the MR fluid or the MR fluid moves between a
stationary core and cylinder. To control the damping effects of the
device, a magnetic flux is formed in and around the core and the
metal cylinder, such that the core and cylinder create a magnetic
circuit. The metal cylinder or casing surrounding the core is often
referred to as a "flux ring" as it directs and provides a path for
the magnetic flux which exists in and around the core. Variation of
the flux in the device affects the flow of the MR fluid between and
around the core and flux ring and thus allows variation of the
damping effects of the MR device.
[0005] More specifically, during operation of the damping device,
the MR fluid flows through a restricted passage or gap formed
between the flux ring and the core. Magnetic flux exists within the
gap, and therefore, the characteristics of the MR fluid flow
through the gap are magnetically controlled by controlling the
magnetic flux. By controlling the characteristics of the MR fluid
flow, the movement of the core and flux ring relative to the fluid
is controlled, thus creating a damping effect to the physical
structures which are operably coupled to the MR damping device. To
form and vary the magnetic flux in and around the core and within
the gap between the core and the flux ring, a magnetic field
generator, such as a wire coil is wound around the core. The
magnetic flux in the core and in the fluid passage is varied by
variation of the electrical current through the coil. The
selectively variable magnetic flux dictates the characteristics of
the fluid flow in the restricted passage, and the relative movement
any mechanical parts and the damping of that movement is then
regulated by controlling the characteristics of the fluid flow.
[0006] When constructing and assembling a typical MR damping
device, as described above, the core and the wire coil which is
wound around the core are formed with an insulative material. The
material, which may be an insulative plastic material, is molded
flush around the coil to protect the coil from the MR fluid.
Thereafter, the flux ring, or other metal casing surrounding the
core and coil, is placed around the core and coil.
[0007] Generally, the flux ring is placed concentrically around the
core and coil combination to form a fixed annular gap between the
flux ring and the core. The MR fluid flows within the gap. As such,
it is important to ensure that the gap is generally consistently
formed and spaced with respect to the core for uniformity of the
damping forces created by the MR damping device. Therefore, the
flux ring must be properly located and aligned around the core and
coil. In conventional designs of MR damping devices, various
fasteners and structures are necessary to provide the proper
securement and alignment of the flux ring. For example,
non-magnetic hog-rings, needle bearings, and rivets are utilized
between the flux ring and the core at three or four positions along
the length of the device. Alternatively, two end plates are crimped
in place with the flux ring and core for alignment and
retention.
[0008] While current MR damping devices are suitable to provide the
damping forces required, their current design and construction
makes them difficult to assemble. Multiple steps are necessary for
proper positioning of the elements with respect to each other,
particularly with respect to placement of the flux ring. As may be
appreciated, multiple steps within a manufacturing and assembly
process increase the cost of such a process.
[0009] A further drawback to current MR damping device designs is
that special fasteners are necessary for locating and aligning the
flux ring with respect to the core and coil. Such fastening
structures increase the number of parts of the design, providing
additional handling and assembly steps and also increasing the cost
of the assembly process. Furthermore, using a design with
endplates, additional "dead" length occurs along the length of the
core and flux ring.
[0010] Another particular drawback of the current design is the
need for proper location and alignment of the flux ring with
respect to the core and coil. It is important that the annular gap
has a consistent spacing along the length of the flux ring and
core. As may be appreciated, such precise attention to location and
alignment of the elements of the MR damping device further
increases the assembly steps necessary and thus increases the
manufacturing and assembly costs for the device.
[0011] The above-mentioned drawbacks of conventional MR damping
devices and the manufacture and assembly of same, are further
exacerbated by the variations which occur in the assembly due to
variations in the various pieces which must be used and aligned.
Inconsistency is introduced as a result of batch-to-batch or
part-to-part variations of the multiple components which are
necessary for construction of the devices. Furthermore, such
differences make consistent alignment and location of the
components of the device difficult. Of course, all such factors
further increase the cost of manufacturing and assembling of the MR
damping devices.
[0012] Therefore, it is a general objective of this present
invention to improve existing MR damping devices, and specifically
to improve their design.
[0013] It is another objective of the present invention to make
such MR damping devices easier and more cost effective to assemble
by reducing the assembly steps and also reducing the complexity of
such assembly steps.
[0014] It is a further objective of the invention to reduce the
cost of manufacturing an MR damping device by reducing the number
of separate parts which must be handled and utilized in the
manufacturing and assembly processes.
[0015] It is another objective of the invention to simplify the
location and alignment steps associated with certain components of
an MR damping device during assembly of such a device.
[0016] It is still another objective of the invention to reduce the
cost increase in the assembly process which is due to the
inconsistencies introduced into such a process by batch-to-batch or
part-to-part variations of the multiple necessary components.
[0017] These objectives and other objectives are addressed by the
present invention which is described in greater detail
hereinbelow.
[0018] The Magneto-Rheological (MR) damping device of this
application addresses the above objectives and utilizes a unique
construction for improved performance and enhanced fabrication and
manufacturing.
SUMMARY OF THE INVENTION
[0019] A magneto-rheological (MR) damping device of the invention
comprises a core element for carrying a magnetic flux, and a
magnetic flux generator, such as a conductive coil, positioned
adjacent to a portion of the core element and operable to generate
a magnetic flux in the core element. In one embodiment, the
conductive coil is wound around the core element. A flux ring
surrounds the core element and coil and defines a passage between
the flux ring and core element for the flow of an MR fluid. The
flux ring is operable for forming a magnetic circuit with the core
element and is further operable for confining a portion of the
magnetic flux proximate the core element and in the passage.
[0020] In accordance with one aspect of the present invention, an
insulative sleeve is positioned over the core element and magnetic
flux generator to electrically insulate the flux generator from the
MR fluid. For example, the sleeve might be press fit over the core
element and magnetic flux generator, or might be more loosely
positioned. The sleeve includes a plurality of protrusions which
extend generally radially outwardly from a center of the core
element. The protrusions are configured to engage the flux ring and
secure the flux ring in a proper position around the core element
and sleeve. More specifically, the protrusions are configured and
dimensioned to concentrically align the flux ring with the core
element and the center axis of the MR damping device when the flux
ring is pressed or placed in position. The protrusions extend
radially outwardly generally in equal distances from the center of
the core element and are operable to thereby secure the flux ring
generally concentrically around the core element and sleeve.
[0021] In one embodiment of the invention, the sleeve is molded,
such as utilizing a suitable moldable plastic or ceramic, and the
protrusions are formed or molded integrally with the sleeve. The
protrusions extend longitudinally along a portion of the length of
the core element, and may extend generally along the entire length
of the core element. Preferably, the protrusions will be positioned
annularly around the sleeve in at least three positions for
securing and centering the flux ring. For further centering and
securing the flux ring, a greater number of protrusions might also
be utilized around the sleeve. When the flux ring is pressed or
otherwise placed on the core element, the protrusions will hold it
in position.
[0022] The present invention improves the design of an MR damping
device and makes such devices easier and more cost effective to
assemble, while reducing the assembly steps and also reducing the
complexity of such assembly steps. Furthermore, the number of
separate parts which must be handled and utilized during
manufacture and assembly is reduced. This reduces inconsistencies
based on batch-to-batch or part-to-part variation of such
components, and also simplifies the location and alignment steps
associated with certain components of the MR damping device during
assembly. These advantages and other advantages will become more
apparent from the Detailed Description of the invention below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The accompanying drawings, which are incorporated in and
constitute a part of this specification, illustrate embodiments of
the invention and, together with a general description of the
invention given below, serve to explain the principles of the
invention.
[0024] FIG. 1A is a longitudinal cross-sectional view of a
conventional MR damping device.
[0025] FIG. 1B is a transverse cross-sectional view along line
1B-1B of a conventional MR damping device.
[0026] FIG. 2A is a longitudinal cross-sectional view of one
embodiment of the inventive MR damping device.
[0027] FIG. 2B is a transverse cross-sectional view along line
2B-2B of one embodiment of the inventive MR damping device.
DETAILED DESCRIPTION
[0028] FIG. 1A illustrates, in longitudinal cross-sectional view,
one embodiment of an existing magneto-rheological (MR) damping
device for comparison to the present invention for purposes of
illustrating the features of the present invention. Throughout this
application, the magneto-rheological characteristics of the device
and fluid used therein will be referred to as "MR." The MR damping
device 10 comprises a core element 12 utilized in combination with
a magnetic flux generator 14. The core element 12 will usually be a
magnetizable material, such as a ferrous material, which is capable
of carrying a magnetic flux therein. The magnetic flux within the
core element 12, and contained proximate the core element, affects
the flow of MR fluid within a passage 16 according to well-known MR
principles.
[0029] Forming passage 16 with the core element 12 and magnetic
flux generator 14 is a metal casing 18, often referred to as a flux
ring. The flux ring 18 is formed of a material which is also
capable of carrying a magnetic flux. The core element 12, magnetic
flux generator 14, and flux ring 18, act as a magnetic circuit,
thereby confining a portion of the magnetic flux within and
proximate to the core element 12, and therefore within passage 16
to affect any MR fluid flowing in the passage 16. To that end, the
flux ring 18 will generally be made of a magnetizable material,
such as a ferrous material. In accordance with one embodiment of
the invention, the core element and flux ring are generally
cylindrical, and the magnetic flux generator 14 is a conductive
coil, such as a wire coil, which is wound around the core element
12 to generate a magnetic flux in the core element. Of course, the
MR damping device 10 may take other shapes as well, although a
cylindrical shape is conventional.
[0030] Referring to FIGS. 1A and 1B, in order to electrically
insulate the magnetic flux generator 14, such as a conductive coil,
from the MR fluid 20, a layer of plastic material 24 is molded over
the coil 14, generally flush with an outer diameter 25 of the core
element 12. The coil 14 includes a plurality of inner turns 14b and
outer turns 14a and is wound around core element 12 until the coil
is generally flush with outer surface 25 of the core element.
[0031] As is generally known with MR devices, magnetic flux
generated within the coil 14 and confined proximate the core
element 12 by the flux ring 18 crosses the passage 16 and affects
the flow of MR fluid within the passage. The MR fluid and its flow
is indicated by the reference arrow 20 within FIG. 1A. Various
different suitable MR fluids are known in the art.
[0032] In accordance with MR damping device operation, increasing
the magnetic flux in the core element 12 and flux ring 18 allows
for selective variation in the flow characteristics of the MR fluid
20 within the passage 16. More specifically, the magnetic flux
affects the rheology of the fluid and, therefore, its flow
characteristics. The fluid flow characteristics, in turn, determine
the damping effect of the device.
[0033] The MR damping device 10 is utilized to dampen the movement
of mechanical components. In some forms, the MR damping device 10
utilizes a generally stationary core element 12 and flux ring 18,
and the MR fluid 20 flows within the passage. One such damping
device is a damping valve wherein fluid flows into and out of the
valve based upon the MR characteristics of the valve. In another
form, the damping device utilizes a core element 12 and a flux ring
18 which are dynamic and are physically coupled to a moving
mechanical part, such as a piston shaft 22, as illustrated in FIG.
1A. For example, the MR damping device 10 might be utilized as part
of a shock absorber assembly, wherein the core element 12 and flux
ring 18 act as the head of the piston and move within a casing of a
shock absorber containing the MR fluid. In that way, the core
element 12 and flux ring 18 move within the MR fluid 20 to make the
MR fluid flow within the passage 16. Damping the movement of the
core element and flux ring dampens the movement of the shaft
22.
[0034] As noted above, core element 12 and flux ring 18 are
generally physically coupled together to define the annular passage
16. To that end, in prior art MR damping devices, the flux ring 18
is secured to the core element 12 by suitable fasteners. In FIGS.
1A and 1B, fasteners 30 are shown coupled between core element 12
and flux ring 18 at various positions along the length of the core
element. The fasteners 30 may be non-magnetic hog-rings, needle
bearings, or rivets which are pressed between the flux ring 18 and
the core element 12. Generally, the fasteners 30 are coupled
between the core element and flux ring at various annular positions
around the core element, as shown in FIG. 1B. In the embodiment
illustrated in FIGS. 1A and 1B, sets of individual fasteners 30 are
shown at various positions along the length of the damping device
10. The fasteners 30 are shown in sets of 3 positioned annularly
around the core element. The fasteners are preferably equally
spaced around the core element to concentrically align the flux
ring 18. Of course, a greater number of fasteners might also be
utilized at each position for proper securement and alignment of
the flux ring. The fasteners 30 are shown grouped proximate either
end of the core element. As noted above, there are various
drawbacks associated with conventional damping device assemblies as
similar to those illustrated in FIGS. 1A and 1B. The additional
fastener parts associated with the assembly, as well as the need to
concentrically align the core element and flux ring with multiple
fasteners increases the complexity of the manufacturing and
assembly process and thus increases the cost of such process. The
present invention addresses such drawbacks, as noted further
hereinbelow.
[0035] Turning now to FIGS. 2A and 2B, one embodiment of the
invention is illustrated. FIG. 2A illustrates a damping device 40
in longitudinal cross-section, whereas FIG. 2B illustrates the
embodiment in transverse cross-section. The inventive MR damping
device 40 utilizes some similar elements as the conventional
damping device 10 and, therefore, some similar reference numerals
will be utilized. For example, damping device 40 utilizes a core
element 12, magnetic flux generator 14, flux ring 18. The MR
damping device defines a passage 16 between the core element and
flux ring, and may include a piston rod 22 coupled thereto,
depending upon the use of the damping device 40. However, the
inventive damping device eliminates the need for multiple separate
fasteners 30 which must be precisely and specifically aligned
between the flux ring and core element to provide for concentric
positioning of the flux ring and self-centering of the ring around
the center, or center axis 42, as illustrated in FIGS. 2A and 2B.
As discussed hereinabove, the magnetic flux generator may be a
conductive coil with a plurality of coil turns 14a, 14b, as
illustrated in the Figures.
[0036] In accordance with one aspect of the present invention, a
sleeve 44 is positioned over the core element 12 and magnetic flux
generator 14. The sleeve is formed of an electrically insulative
material and includes a plurality of protrusions or projections 46
which extend radially outwardly from the center or center axis 42
of the core element. As will be appreciated, the center or center
axis 42 of the core element also defines the center or center axis
of the damping device 40. The sleeve protrusions 46 are configured
to extend outwardly and engage an inner surface 45 of the flux ring
18 and secure the flux ring 18 in position around the core element
12, the magnetic flux generator 14, and the sleeve 44. In that way,
individual fasteners 30 are eliminated from the damping device 40
and the assembly thereof.
[0037] In one embodiment of the invention, the plurality of
protrusions 46 are integrally formed with the sleeve, and are
thereby secured in place with the sleeve around the core element 12
and magnetic flux generator 14. The sleeve and protrusions may be
formed out of a suitable insulative plastic or ceramic material. In
accordance with one aspect of the present invention, the
protrusions extend radially outwardly, generally in equal distance
from the sleeve and center axis 42 of the core element 12 and are
operable to secure the flux ring 18 generally concentrically around
the core element and the sleeve 44. Generally, for MR damping
devices, it is important for the flux ring to be concentric and/or
self-centered with respect to the core element to provide a passage
16 which has similar annular dimensions around the damping device
40. In that way, the magneto-rheological effect on the fluid
flowing in passages 16 is consistent annularly around the MR
damping device.
[0038] In accordance with another aspect of the present invention,
not only do the protrusions eliminate the need for separate
fasteners and the additional assembly steps associated therewith,
but also the inventive protrusions add a self-centering aspect to
the flux ring with respect to the core element, without any
additional assembly steps. When the flux ring is pressed onto or
otherwise positioned on the sleeve, the flux ring will be
automatically centered around the device. Accordingly, the
invention reduces parts and labor costs and the complexities
associated with manufacturing and assembling an MR damping device.
Furthermore, by eliminating the parts, the effects of
batch-to-batch and part-to-part variations within the assembly can
be reduced.
[0039] In accordance with still another aspect of the present
invention, the protrusions are preferably positioned concentrically
around the core in at least three positions for providing the
desired concentricity between the flux ring and the core element
12. For concentricity, the protrusions should be equally spaced
around the circumference of the sleeve. As will be readily
understood by a person of ordinary skill in the art, additional
numbers of protrusions might be utilized as well.
[0040] Referring to FIG. 2A, in accordance with another aspect of
the present invention, the protrusions extend longitudinally along
a portion of a length of the core. Protrusion 46a illustrated on
the left side of FIG. 2A is shown to extend generally along the
length of the core corresponding to the indentation 47 formed in
the core for receiving the wire coil forming magnetic flux
generator 14. Alternatively, as illustrated on the right side of
FIG. 2A, protrusion 46b may extend longitudinally generally along
the entire length of the core element. Still further, the
protrusions may extend as multiple protrusion sections along the
length of the core which are aligned with spaces in between. The
protrusions are shown as a single set of protrusions. However,
multiple sets might be utilized and might be angularly offset from
each other around the circumference of the sleeve.
[0041] To form the MR damping device of the present invention, the
flux ring is press fit onto the sleeve protrusions. Therefore, in
one embodiment, the protrusions are configured and dimensioned to
have an outwardly radial dimension which is at least slightly
greater than the inner diameter, or inner dimension of the flux
ring 18. The protrusions may be formed to be slightly flexible so
that they will deform to allow the flux ring to be pressed onto the
sleeve. By press fitting the flux ring into position, the
protrusions hold the flux ring both axially and radially in
position, and concentrically aligned with the center axis 42 and
core element 12. For example, shrink fitting or thermal press
fitting might be used where the flux ring is heated above room
temperature for expansion and the sleeve is cooled to shrink. The
flux ring is then easily slid over the sleeve, and when both parts
reach an equilibrium temperature, they stay in position with a snug
fit. Alternatively, the protrusions might be dimensioned close to
or the same as the inner diameter of the flux ring, wherein the
flux ring may be more easily slid over the sleeve and protrusions.
In such a case, the flux ring may have to be secured axially while
the protrusions 46 keep the flux ring generally concentric with
respect to the MR damping device. Again, the utilization of the
protrusions, rather than separate fasteners for securing the flux
ring, provides a self-centering feature without additional assembly
steps, therefore reducing assembly costs.
[0042] In the embodiment of the invention wherein the sleeve or
protrusions are molded over the core element and magnetic flux
generator 14, the protrusions might be positioned concentrically
around the sleeve 44 such that they are in line with the mold
parting lines. Such a construction will further potentially
eliminate excess flash associated with the molding process, and
thus further result in an improvement in cost effectiveness in the
assembly process. As noted above, suitable plastic or a moldable
ceramic might be utilized to form or mold the sleeve 44 and
protrusions 46. Illustrated in FIG. 2B, the protrusions are shown
to have generally a triangular cross-section wherein one point of
the triangle contacts the inner surface of the flux ring 18.
However, other such shapes, such as a semi-circular shape, might
also be utilized wherein a tangential radial point engages the
inside surface of the flux ring. Still further, other protrusion
shapes might also be utilized in accordance with the principles of
the present invention.
[0043] While the present invention has been illustrated by the
description of the embodiments thereof, and while the embodiments
have been described in considerable detail, it is not the intention
of the applicant to restrict or in any way limit the scope of the
appended claims to such detail. Additional advantages and
modifications will readily appear to those skilled in the art.
Therefore, the invention in its broader aspects is not limited to
the specific details representative apparatus and method, and
illustrative examples shown and described. Accordingly, departures
may be made from such details without departure from the spirit or
scope of applicant's general inventive concept.
* * * * *