Note: Descriptions are shown in the official language in which they were submitted.
CA 02713695 2010-08-23
MULTI-STAGE SWITCHABLE INERTIA TRACK ASSEMBLY
Background of the Disclosure
[0001] This disclosure relates to a damper assembly and specifically a multi-
stage switchable inertia track assembly. More particularly, the multi-stage
switchable
inertia track assembly contains both a low frequency inertia track and a high
frequency
inertia track. The low frequency track is used to create damping to address
vehicle
smooth road shake. The high frequency track is used to create a high frequency
sympathetic resonance to reduce transmission of idle disturbance frequencies
from the
powertrain to a vehicle body or frame. Selected features may find application
in other
related environments and applications.
[0002] The basic technology for switchable hydraulic engine mounts has been
known in the industry for several years. Physical switching of a hydraulic
mount from a
fluid damped state to a non-damped state by way of opening and closing a port
is well
understood. However, there are multiple methods by which this can be achieved.
[0003] Most vacuum actuated hardware is mounted externally for ease of
manufacture. This external mounting tends to reduce the efficiency of the
mount
response, but it does allow for easier sealing of the hydraulic fluid in the
mount
assembly. A problem with most conventional designs is that they use a
diaphragm that
encloses a volume and forms an air spring under the diaphragm and attached to
an
external port. Opening and closing this external port is the method used to
"switch" the
mount state, i.e., the stiffness or damping response. In the switch "open"
state, air can
be pumped to atmosphere from the volume. For example, the hydraulic engine
mount
has a low bearing spring stiffness with the open switch (the volume is open to
atmosphere) and the engine mount damps or insulates idling vibrations (low
amplitude,
high frequency). In the switch "closed" state, the air in the volume acts as a
stiff spring
because the volume is closed or sealed and the damping fluid is transferred
back and
forth between a first or working fluid chamber and a second or compensating
fluid
chamber to damp high amplitude, low frequency vibrations. The air spring
(closed
volume) created by the closed port reduces the pressure of the fluid that
would
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otherwise be pumped through the inertia track, as some of the fluid pressure
is used to
compress the air spring.
[0004] Other designs also use a vacuum actuated diaphragm that seals on the
diaphragm cover and uses the diaphragm as a seal on the inertia track.
[0005] Still other designs use a rotary valve to open and close the port.
These
rotary valves can rotate either axially or radially with the mount. In either
case, sealing
of the valve can become an issue, where it is difficult to seal from either
the low
pressure side of the mount to high or from the high pressure side of the mount
to
atmosphere.
[0006] As with most switchable hydraulic engine mounts this mount is intended
to
suspend the powertrain, provide damping to powertrain motion, control the
powertrain
travel, and isolate the powertrain from the vehicle chassis. The switch
mechanisms in
multi-state mounts allow the mount to switch between four states. Two of the
states
allow the fluid effect of the mount to be decoupled from compliance
vibrations, and the
other two states adjust the damping and frequency response of the mount.
[0007] Neither an engine mount nor vacuum actuated switching of the states in
an engine mount is individually deemed novel per se. However, a need exists
for an
improved switchable inertia track assembly and associated method of packaging
same.
Summary of the Disclosure
[0008] A multistage switchable inertia track assembly includes a housing, an
inertia track received in the housing and having an elongated fluid damped
first path
that is adapted to communicate with an associated first fluid chamber on a
first side and
an associated second fluid chamber on a second side, and a non-damped second
path
that is adapted to communicate with the associated first and second fluid
chambers, a
decoupler received in the housing that selectively closes at least one of the
first and
second paths, an idle diaphragm in the housing that selectively controls
communication
between the first and second fluid chambers to selectively alter the damping,
and first
and second ports in the housing that communicate with the decoupler and the
idle
diaphragm, respectively.
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[0009] A method of manufacturing a multistage switchable inertia track
assembly
includes providing a housing, positioning an inertia track in the housing that
has an
elongated fluid damped first path that is adapted to communicate with an
associated
first fluid chamber on a first side and an associated second fluid chamber on
a second
side, and a non-damped second path that is adapted to communicate with the
associated first and second fluid chambers, securing a decoupler in the
housing to
selectively close at least one of the first and second paths, supplying an
idle diaphragm
in the housing to selectively control communication between the first and
second fluid
chambers and to selectively alter the damping state, and providing first and
second
ports in the housing to communicate with the decoupler and the idle diaphragm,
respectively.
[0010] Still other features and benefits will be found in the following
detailed
description.
Brief Description of the Drawings
[0011] Figure 1 is a perspective view of an assembled hydraulic engine mount
or
hydromount.
[0012] Figure 2 is an exploded view of various components of the mount
assembly of Figure 1.
[0013] Figure 3 is a longitudinal cross-sectional view of the assembled mount
of
Figures 1 and 2.
[0014] Figure 4 is an exploded view of a first embodiment of the inertia track
assembly.
[0015] Figure 5 is an exploded view similar to Figure 4 of an alternative
inertia
track assembly.
[0016] Figure 6 is a perspective view of the inertia track main.
[0017] Figure 7 is a cross-sectional view of the inertia track assembly
illustrating
a first flow path through the decoupler vacuum port.
[0018] Figure 8 is a cross-sectional view of the inertia track assembly and
illustrating a second flow path of the idle diaphragm vacuum port.
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[0019] Figures 9-14 are perspective views of another embodiment of the inertia
track assembly of an engine mount incorporating an integrated accumulator.
Detailed Description of the Preferred Embodiments
[0020] Turning first to Figures 1-3, a multi-state vacuum actuated inertia
track
assembly is shown within an engine mount or hydro-mount assembly 100. More
particularly, the mount assembly 100 includes a restrictor or external housing
102
dimensioned to receive a first or elastomeric component or main rubber element
104
that is generally shaped as a truncated cone, and primarily made of an
elastomeric
material, such as an elastic rubber as is conventional in the art. A fastener
or bolt 106
extends outwardly from the main rubber element for fastening to the power
train or
engine (not shown) in a manner generally known in the art. The fastener
cooperates
with a metal bearing member 108 that has at least a portion encapsulated
within the first
elastomeric member 104. In addition, a lower peripheral portion of the main
rubber
element may include a stiffener, such as metallic stiffener 110, molded within
the main
rubber element to add rigidity and support.
[0021] The main rubber element is received within the restrictor housing 102
so
that the fastener 106 extends through a central opening 112 in the restrictor.
An
internal shoulder 114 (Figure 3) of the restrictor abuttingly engages the
reinforced, lower
portion of the main rubber element. In addition, the lower portion of the main
rubber
element forms a portion of a first or upper fluid chamber 116, namely the high
pressure
side, of the engine mount. The remainder of the first fluid chamber 116 is
defined by
the inertia track assembly 120, more specific details of which will be
described below.
An outer radial portion of an upper surface of the inertia track assembly
denoted by
reference numeral 122 abuttingly and sealingly engages the main rubber element
104 in
order to seal the first fluid chamber 116. As particularly evident in Figure
3, at least a
portion of the inertia track assembly is received within the restrictor
housing 102. A
second outer radial portion along the lower surface denoted by reference
numeral 124
is sealingly engaged by a rubber boot or diaphragm 130, and particularly an
upper
peripheral portion 132 thereof. The diaphragm 130 is protected by a diaphragm
cover
140, preferably formed of a more rigid material than the elastomeric
diaphragm, and
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that matingly engages the restrictor housing 102. When the diaphragm cover 140
is
fastened to the restrictor, the lower peripheral edge of the main rubber
element 104 and
the peripheral portion 132 of the diaphragm sealingly engage opposite sides or
faces
122, 124, respectively, of the inertia track assembly 120. As vibrations or
displacements are received into the mount from the powertrain, fluid is pumped
from the
first fluid chamber 116 through the inertia track assembly 120 in different
ways.
Particularly, and with continued reference to Figures 1-3, and additional
reference to
Figures 4 and 5, the inertia track assembly 120 is disposed between the first
or upper
fluid chamber 116 and the second or lower fluid chamber 150. Thus, the upper
side of
the inertia track assembly is associated with the high pressure side of the
mount. On
the other hand, the lower surface of the inertia track assembly is associated
with the
second or lower fluid chamber 150 and is sometimes referred to as the low
pressure
side of the mount. The fluid is pumped from the top to the bottom through the
inertia
track assembly. The path that the fluid takes through the inertia track
assembly
depends on a decoupler 160 and an idle diaphragm 170. More particularly, the
decoupler 160 is preferably a rubber disk or similar structural arrangement
received
over a portion of a first opening or path 180 through the high frequency
inertia track.
Thus, the rubber decoupler 160 is dimensioned for close receipt within a cup
shaped
recess 182 in an upper surface 184 of the housing, which has an opening or
path to the
high frequency inertia track 180 and particularly a central opening 186
(Figure 6) that is
selectively closed by a central portion 188 of the idle diaphragm 170. Thus, a
decoupler
cover 190 has a series of openings 192 that allow fluid from the first fluid
chamber to
pass therethrough, and around the decoupler 160 and into the high frequency
inertia
track 180, particularly through opening 182, in addition to passing through
opening 194.
This is the path of least resistance from the first/upper fluid chamber 116,
to the
second/lower fluid chamber 150 disposed above the idle diaphragm 170, i.e.,
the fluid
side of the idle diaphragm.
[0022] Alternatively, a second path, or elongated low frequency inertia track
has
an opening 196 radially outward of the decoupler cover in the decoupler
housing that
communicates with a serpentine low frequency inertia track 198 (Figure 6) that
ultimately communicates with opening 200 through a lower surface of the
inertia track
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housing in communication with the second/lower fluid chamber 150. Fluid only
flows
through this serpentine path 198, however, when the high frequency inertia
track path is
otherwise blocked. So, for example, where the idle diaphragm is shown in its
extended
position as shown in Figure 3, the high frequency inertia track is closed
since opening
186 is sealed by the central portion 188 of the idle diaphragm 170. Fluid must
then
proceed through the low frequency inertia track 198 to exit through opening
200 that
communicates with the low pressure side of the mount. As will be appreciated,
this
occurs when no vacuum is applied to the underside of the idle diaphragm. In
addition,
the decoupler 160 is allowed to freely oscillate creating a decoupled state
for low input
displacements. For higher input displacements, the fluid is forced through the
low
frequency inertia track.
[0023] In another state or mode of operation, vacuum is provided to the
underside 202 of the idle diaphragm. In this manner, the central port 186
opens and
fluid more easily passes from the first or upper fluid chamber 116 to the
second or lower
fluid chamber 150. Thus, by selective switching of vacuum or negative pressure
to the
underside 202 of the idle diaphragm, the mount is switched from the high
frequency
inertia track 180 (vacuum applied, port open) to the low frequency track 198
(vacuum
removed, port closed).
[0024] Port 210, as shown in Figure 7, is selectively supplied with negative
pressure or vacuum. An external valve such as a solenoid valve is connected to
the
port 210 and when vacuum is applied to the decoupler port, the decoupler 160
collapses, the decoupler can no longer oscillate.
[0025] The passage or particular path for the negative pressure or vacuum to
reach the underside of the idle diaphragm is more particularly illustrated in
Figure 8
where a valve (such as a solenoid valve, not shown) supplies negative pressure
to port
220.
[0026] Ultimately, four different states or modes of operation are achieved.
In a
first state of the hydromount, when no vacuum is applied to either the
decoupler 160 or
the idle diaphragm 170, the decoupler 160 is allowed to freely oscillate
creating a
decoupled state for low input displacements. For higher input displacements,
the fluid is
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forced through the low frequency inertia track 198 which exits into the low
pressure side
of the mount.
[0027] In a second state, when vacuum is applied to both the decoupler 160 and
the idle diaphragm 170, the decoupler can no longer oscillate and the high
frequency
inertia track is opened (i.e., the idle diaphragm central portion 188 is
retracted from
opening 186). This causes the fluid to flow through the high frequency inertia
track.
This creates the high frequency dynamic rate dip that can be used, for
example, to
reduce idle disturbances at the rate dip frequency.
[0028] In a third state, when vacuum is applied to the decoupler 160 only and
not
the idle diaphragm 170, the fluid from the first fluid chamber is again forced
through the
low frequency inertia track 198 in order to reach the second fluid chamber.
This is the
coupled state of the mount, which creates high levels of damping at low
frequencies that
can be used, for example, to damp road input vibrations.
[0029] In a fourth state of the switchable inertia track assembly of the
mount,
vacuum is applied to the idle diaphragm 170 only and not the decoupler 160.
This state
would allow the decoupler to oscillate freely for low displacement input, but
fluid will flow
through the high frequency inertia track at higher displacement inputs because
the high
frequency inertia track path is open.
[0030] The upper plate 184 (high pressure side of mount) is preferably made
from
metal, plastic, or composite material. The decoupler 160 is preferably made
from metal,
plastic, or composite material made from a metal, plastic, or composite
support ring, and
an elastomeric diaphragm material. The decoupler is retained and sealed to the
center
plate or housing 120 by the upper plate 184. The center plate is preferably
made from
metal, plastic, or composite material. The center housing contains most of the
inertia
track geometries and vacuum ports integrated into one part. The high frequency
vacuum diaphragm 170 is preferably made from a metal, plastic, or composite
support
ring and an elastomeric diaphragm material.
[0031] The inertia track assembly contains both vacuum switching diaphragms.
This makes it easier to assemble the switch into the remainder of the
hydromount. The
compact internal switches prevent potential shipping damage, as only the two
vacuum
ports are visible externally.
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[0032] The invention does not use the diaphragm as part of the switching
mechanism, thereby improving the durability and performance of the mount.
[0033] Again, when vacuum is applied to the decoupler port 210, the negative
pressure causes the decoupler 160 to collapse. When vacuum is removed, the
decoupler 160 is allowed to move freely. This vacuum switching mechanism,
changes
the mount from coupler (vacuum applied) to decoupled (vacuum removed). When
vacuum is applied or removed from the idle diaphragm port 220, this causes the
idle
diaphragm 170 to collapse or extend, respectively. This opens and closes the
high
frequency idle track. This vacuum switching mechanism switches the mount from
the
high frequency inertia track (vacuum applied - port open) to the low frequency
track
(vacuum removed - port closed).
[0034] In a preferred process of assembly, the decoupler 160 is pressed into
the
decoupler housing. The decoupler cover 190 is ultrasonically welded to the
decoupler
housing, and the decoupler housing 184 is ultrasonically welded to the inertia
track main
120. The decoupler port is ultrasonically welded into the inertia track main,
and the idle
diaphragm is pressed into the idle diaphragm housing 230. The idle diaphragm
housing
is ultrasonically welded to the idle diaphragm cover 232. Thereafter, the idle
diaphragm
housing assembly is ultrasonically welded to the inertia track main 120.
[0035] The embodiment of Figure 5 is substantially identical to the Figure 4
embodiment, except that many of the components include a metal such as
aluminum
and are not simply plastic. The assembly process includes pressing the
decoupler 160
into the decoupler housing, and the decoupler cover 190 is crimped to the
decoupler
housing 182. The decoupler housing is pressed onto the inertia track main 120,
and the
decoupler port 210 is pressed into the inertia track main. The idle diaphragm
170 is
pressed into the idle diaphragm housing 230, and the idle diaphragm housing is
ultrasonically welded to the idle diaphragm cover 232. The idle diaphragm
housing
assembly is then ultrasonically welded to the inertia track main 120.
[0036] The invention is intended to function properly with little degradation
to
performance in the -40C to +120C temperature range.
[0037] Figures 9-14 illustrate another embodiment and for purposes of
consistency and brevity like components will be identified by like reference
numerals,
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and new components will be identified by new numerals. More particularly, an
inertia
track assembly 122 integrates an accumulator or buffering means 300 into the
inertia
track assembly. The accumulator 300 is added to the existing multi-state
inertia track
design to prevent vacuum line resonance in the "drive-away" or default state
of the
mount. In the default state, i.e., when no vacuum is being applied to either
port 210,
220, movement of the rubber decoupler 160, for example, will pump air in and
out of the
bounce port or decoupler port 210. This oscillation will cause the air in any
tube or
passage attached to that port to go into resonance. The magnitude and
frequency of
this resonance will be effected by the inside diameter, stiffness, and length
of the
attached tube. This air resonance will increase the stiffness of the mount
when forced
vibrations are applied at post-resonant frequencies to the mount 100. This
negatively
effects the isolation of the mount at these frequencies.
[0038] The accumulator 300 effectively reduces or eliminates this air
resonance
response as the accumulator is preferably located in-line between the
decoupler 160
and the port 210, buffering the pumping effect of the decoupler. This is
believed to be
the first known application of an air accumulator in a vacuum actuated
hydraulic mount.
[0039] The larger the accumulator 300, the greater the effect. Thus, as
evident in
Figures 9-14, and particularly Figures 11 and 12, the accumulator is
physically
integrated into the inertia track assembly 122. This arrangement is in direct
contrast to
the current state of the art where an external accumulator must be used which
adds
undesirable cost and mass, as well as difficulties in packaging the external
accumulator.
In Figure 7, the port 210 is shown as continuing in size/dimension as the port
communicates with internal passage 302 that leads from the port to the
decoupler 160.
As described above, when vacuum is applied to the vacuum port 210 and then
proceeds through passage 302 to the decoupler 160 collapses and can no longer
oscillate. However in the default state, e.g., when no vacuum is applied to
either port
210, 220, movement of the rubber decoupler 160 will pump air in and out of the
bounce
port or decoupler port 210 whci results in the undesired pumping and air
resonance
response described above. By incorporating the enlarged accumulator chamber
300
between the port and the decoupler, the pumping/resonance response is reduced
or
eliminated. In the exemplary embodiment, the accumulator 300 has a volume on
the
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order of 18 to 20 cc, although these dimensions are exemplary only and should
not be
deemed limiting. Thus, the communication of the substantially constant
dimension
passage 302 with the enlarged cross-section and volume provided by the
integrated
accumulator 300 provides the desired buffering of any potential pumping effect
that
could result from the freely oscillating decoupler in the decoupled state.
Incorporating
the integrated accumulator into the inertia track assembly 120 is accomplished
with a
corresponding reduction in the size of the first path 180 (compare Figure 6
with Figure
12) but this reduction in the dimension of path 180 does not adversely impact
operation/communication through the high frequency inertia track. Likewise,
integrating
the accumulator 300 into the structure does not adversely impact other
functions or
states of the mount. The accumulator can be enlarged by extending from a lower
surface 304 of the inertia track assembly housing (Figures 13-14) if
additional volume is
desired.
[0040] The invention has been described with reference to the preferred
embodiment. Modifications and alterations will occur to others upon reading
and
understanding this specification. It is intended to include all such
modifications and
alterations in so far as they come within the scope of the appended claims or
the
equivalents thereof.
