U.S. patent application number 17/044621 was filed with the patent office on 2021-07-01 for bush.
This patent application is currently assigned to DTR VMS Limited. The applicant listed for this patent is DTR VMS Limited. Invention is credited to Jan Geisen, Hamid Mir, Jonathan Morton, Peter Simms.
Application Number | 20210199169 17/044621 |
Document ID | / |
Family ID | 1000005508079 |
Filed Date | 2021-07-01 |
United States Patent
Application |
20210199169 |
Kind Code |
A1 |
Morton; Jonathan ; et
al. |
July 1, 2021 |
BUSH
Abstract
Various embodiments provide a bush for isolating vibrations, the
bush comprising: a first anchor part defining a longitudinal axis;
a second anchor part disposed coaxially with respect to the first
anchor part; a first resilient body operably engaged with the first
anchor part; a second resilient body operably engaged with the
second anchor part; and an inertial mass element disposed between
the first anchor part and the second anchor part, wherein the
inertial mass element is independently connected to the first
resilient body and the second resilient body, wherein the first
resilient body, second resilient body and inertial mass element are
arrange to isolate vibrations between the first anchor part and the
second anchor part within a predetermined operational frequency
range, and wherein the inertial mass element is arranged to isolate
the first anchor part and second anchor part from dynamic stiffness
increases associated with eigenmodes of the inner resilient body
and the outer resilient body in the predetermined operational
frequency range.
Inventors: |
Morton; Jonathan; (Mendig,
DE) ; Geisen; Jan; (Mendig, DE) ; Simms;
Peter; (Trowbridge Wiltshire, GB) ; Mir; Hamid;
(Troy, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DTR VMS Limited |
Trowbridge Wiltshire |
|
GB |
|
|
Assignee: |
DTR VMS Limited
Trowbridge Wiltshire
GB
|
Family ID: |
1000005508079 |
Appl. No.: |
17/044621 |
Filed: |
April 5, 2019 |
PCT Filed: |
April 5, 2019 |
PCT NO: |
PCT/EP2019/058691 |
371 Date: |
October 1, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F16F 2224/025 20130101;
F16F 2224/0208 20130101; F16F 2230/007 20130101; F16F 2230/36
20130101; F16F 2222/08 20130101; B60K 5/1291 20130101; F16F
2228/007 20130101; F16F 7/108 20130101; F16F 2234/02 20130101; B60K
5/1208 20130101 |
International
Class: |
F16F 7/108 20060101
F16F007/108; B60K 5/12 20060101 B60K005/12 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 9, 2019 |
GB |
1805838.8 |
Claims
1. A bush for isolating vibrations, the bush comprising: a first
anchor part defining a longitudinal axis; a second anchor part
disposed coaxially with respect to the first anchor part; a first
resilient body operably engaged with the first anchor part; a
second resilient body operably engaged with the second anchor part;
and an inertial mass element disposed between the first anchor part
and the second anchor part, wherein the inertial mass element is
independently connected to the first resilient body and the second
resilient body, wherein the first resilient body, second resilient
body and inertial mass element are arranged to isolate vibrations
between the first anchor part and the second anchor part within a
predetermined operational frequency range, wherein the inertial
mass element is arranged to isolate the first anchor part and
second anchor part from dynamic stiffness increases associated with
eigenmodes of the first resilient body and the second resilient
body in the predetermined operational frequency range, and wherein
the bush includes one or more snubber portions to physically limit
an extent of relative radial movement between the first and second
anchor parts, and wherein at least one of the first and second
anchor parts includes the one or more snubber portions.
2. A bush according to claim 1, wherein the inertial mass element
occupies a non-resonant condition in the predetermined operational
frequency range.
3. A bush according to claim 1, wherein the inertial mass element
occupies a resonant condition at a frequency below the
predetermined operational frequency range.
4. A bush according to claim 1 having a dynamic stiffness
characteristic that exhibits a single peak at a resonant frequency
below the predetermined operational frequency range.
5. A bush according to claim 4, wherein the resonant frequency is
less than 1000 Hz.
6. A bush according to claim 1, wherein one of the first and second
resilient bodies includes axially extending passages therethrough
to facilitate relative movement between the first and second anchor
parts during loading.
7. A bush according to claim 6, wherein both of the first and
second resilient bodies include axially extending passages
therethrough to facilitate relative movement between the first and
second anchor parts during loading.
8. A bush according to claim 6, wherein the axially extending
passages include the one or more snubber portions which physically
limit an extent of relative radial movement between the first and
second anchor parts.
9. A bush according to claim I, wherein the first anchor part is a
rod extending along the longitudinal axis, and wherein the second
anchor part is a sleeve surrounding the rod.
10. A bush according to claim 9, wherein the inertial mass element
is a rigid tubular body disposed coaxially with respect to the rod
in between the rod and the sleeve.
11. A bush according to claim 10, wherein the first resilient body
extends radially between an outer surface of the rod and an inner
surface of the rigid tubular body, and the second resilient body
extends radially between an outer surface of the rigid tubular body
and an inner surface of the sleeve.
12. A bush according to claim 10, wherein the first resilient body
is a solid resilient member that fills an annular volume between
the rod and the rigid tubular body.
13. A bush according to claim 1, wherein the first anchor part is a
boss element and the second anchor part is a cup element arranged
to receive the boss element therein, and wherein the first
resilient body, second resilient body and inertial mass element
together form a frustoconical interconnection between the boss
element and the cup element.
14. A bush according to claim 13, wherein the inertial mass element
comprises a snubber portion for limiting relative axial movement
between the boss element and the cup element.
15. A bush according to claim 14, wherein the snubber portion
comprises a radially extending plate.
16. A bush according to claim 14, wherein the cup element comprises
a top flange arranged to abut the snubber portion to restrict an
axial distance by which the boss element is movable into the cup
element.
17. A bush according to claim 1, wherein the first anchor part is
connectable to a first machine component and the second anchor part
is connectable to a second machine component, whereby the bush is
operable to isolate vibrations between the first machine component
and second machine component.
18. A bush according to claim 17, wherein the first machine
component and second machine component are the engine and chassis
of a vehicle.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a National Phase application of
International Application No. PCT/EP2019/058691, filed Apr. 25,
2019, which claims the benefit of British Application GB 1805838.8,
filed on Apr. 9, 2018, both of which are incorporated herein in
their entireties.
FIELD OF THE INVENTION
[0002] The invention relates to a bush for resisting vibrations
between two components, such as the engine and chassis of a
vehicle.
BACKGROUND TO THE INVENTION
[0003] Typically a bush for resisting vibration comprises two
anchor parts that are connected by resilient material, such as
rubber. One anchor part is attached to one component of the
vibrating machinery, and the other anchor part attached to another
component. As the two components vibrate relative to each other,
the resilient material to provide isolation between vibrating
component and anchor. Such bushes thus permit some relative
movement, but act to prevent excessive movement between
components.
[0004] GB 2 364 558 discloses an example of a bush, in which the
anchor part for one component of the vibrating machinery is in the
form of a hollow sleeve and the other anchor part in the form of a
rod or tube extending approximately centrally and coaxially of the
sleeve. A resilient body, e.g. of rubber or other suitable
elastomeric material, is disposed within an annular volume between
the sleeve and the rod. The resilient body can be secured in place,
e.g. by radial crimping of the sleeve towards the rod or by bonding
via a vulcanisation process.
[0005] The resilient body between the sleeve and the rod represents
a spring element for isolating vibration. The dynamic stiffness of
this spring element varies with vibration frequency depending on a
number of factors, including the resilient material used, and the
shape and configuration of the connection between the sleeve and
rod. However, in any given arrangement, the resilient body will
exhibit one or more eigenmodes where the dynamic stiffness
increases and the vibrational isolation between the interconnected
components is reduced.
[0006] It is desirable for the eigenmodes of the resilient body to
lie outside a frequency range associated with normal operation of
the components to be interconnected (e.g. engine and chassis in a
vehicle).
SUMMARY OF THE INVENTION
[0007] At its most general the present invention provides a bush
having an inertial mass within a resilient interconnection between
two anchor parts in order to provide a flat dynamic stiffness
profile within a predetermined operational vibration frequency
range. The predetermined operational vibration frequency range may
be a sensitive vibration frequency range, e.g. associated with
vibration frequency that may be expected to occur regularly or for
extending periods during operation. For example, where the bush is
connected in a vehicle, the predetermined operational vibration
frequency range may be associated with engine vibrations associated
with cruising across a range of conventional speeds.
[0008] The anchor parts are interconnected by two independent
spring elements (e.g. resilient bodies) which are separated by the
inertial mass. Properties of the inertial mass and spring elements
are selected to ensure that any resonance conditions associated
with either of the spring elements or the spring elements and
inertial mass in combination lie outside the predetermined
operational vibration frequency range, e.g. in a non-sensitive
operational vibration frequency range.
[0009] The bush may be used in many different applications or
environments, for example, the bush may be connected to an internal
combustion engine, an electric engine, a hybrid engine, a motor, an
electric motor, a gearbox, a differential, or the like.
[0010] According to the invention, there is provided a bush for
isolating vibrations, the bush comprising: a first anchor part
defining a longitudinal axis; a second anchor part disposed
coaxially with respect to the first anchor part; a first resilient
body operably engaged with the first anchor part; a second
resilient body operably engaged with the second anchor part; and an
inertial mass element disposed between the first anchor part and
the second anchor part, wherein the inertial mass element is
independently connected to the first resilient body and the second
resilient body, wherein the first resilient body, second resilient
body and inertial mass element are arrange to isolate vibrations
between the first anchor part and the second anchor part within a
predetermined operational frequency range, and wherein the inertial
mass element has a mass selected to isolate the first anchor part
and second anchor part from dynamic stiffness increases associated
with eigenmodes of the inner resilient body and the outer resilient
body in the predetermined operational frequency range. In use, the
bush may thus exhibit a flat or otherwise generally uniform dynamic
stiffness profile across the predetermined operational frequency
range.
[0011] The term "resilient" is used herein to indicate generally
the ability to recoil or spring back after application of a
deforming force.
[0012] Preferably the inertial mass element occupies a non-resonant
condition in the predetermined operational frequency range. In
other words, the relative movement of the inertial mass element
between the first anchor part and second anchor part may lie within
a range that is substantially uniform across the predetermined
operational frequency range. A combination of the inertial mass
element and first and second resilient bodies may form a system
that exhibits resonance. This resonance may be characterised by an
increase in the system's dynamic stiffness. This resonant condition
(which may be viewed as an oscillation resonance of the inertial
mass element) may be at a frequency below the predetermined
operational frequency range, e.g. in a non-sensitive operational
frequency range at or below 1000 Hz.
[0013] For example, if the bush is used in a vehicle, e.g. a
vehicle with an electric motor, a non-sensitive operational
frequency range that is below a threshold of 1000 Hz can be a good
area because electric motors typically generate vibrations at this
frequency at relatively low speeds. As such low speeds are not
normally maintained for any length of time, a driver would not
perceive any noise in this non-sensitive range. In contrast, a high
dynamic stiffness due to the resonant condition occurred at higher
frequency range, there is a risk of it coinciding with cruising of
times spent at a certain speed for long periods of time, which
would be noticeable. It is to be understood that in another
embodiment, a different threshold could be used, such as, for
example, below 500 Hz or between 200 Hz and 800 Hz.
[0014] The bush may exhibit a dynamic stiffness characteristic
having a single peak at a resonant frequency below the
predetermined operational frequency range. The dynamic stiffness
characteristic may include a plateau region across the
predetermined operational frequency range. The plateau region may
be characterised by a variation in dynamic stiffness of less than
1000 N/mm, preferably less than 500 N/mm.
[0015] The predetermined operational frequency range may be 500 to
2500 Hz or any sub-range thereof. The bush may be arranged to
exhibit a low dynamic stiffness, e.g. less than 100 N/mm, within
all or part of the predetermined operational frequency range, e.g.
within a range from 1000 to 2000 Hz.
[0016] In one example, the first anchor part may be a rod extending
along the longitudinal axis. The second anchor part may comprise a
sleeve surrounding the rod and defining an annular spacing
therebetween. In this example, the inertial mass element may
comprise a piece of material, such as a rigid tubular body,
disposed in the annular spacing, e.g. coaxially with respect to the
rod and the sleeve. The inertial mass element may be retained in
this position by the first and second resilient bodies. For
example, the first resilient body may extend radially between an
outer surface of the rod and an inner surface of the inertial mass
element. The second resilient body may extend radially between an
outer surface of the inertial mass element and an inner surface of
the sleeve.
[0017] The first resilient body may be a solid resilient member
that fills an annular volume between the rod and the rigid tubular
body. Alternatively, the first resilient body may be a moulded
resilient member having axially extending passages therethrough to
facilitate relative movement between the first and second anchor
parts during loading, for example, when the first and/or second
anchor parts are loaded during operation.
[0018] The second resilient body may be a moulded resilient member
having axially extending passages therethrough to facilitate
relative movement between the first and second anchor parts during
loading, for example, when the first and/or second anchor parts are
loaded during operation.
[0019] The bush may include one or more snubber portions to
physically limit an extent of relative radial movement between the
first and second anchor parts. For instance, the first resilient
body may include snubber portions formed within its axially
extending passages to physically limit the extent of relative
radial movement between the first and second anchor parts.
Additionally or alternatively, the second resilient body may
include snubber portions formed within its axially extending
passages to physically limit the extent of relative radial movement
between the first and second anchor parts. Additionally or
alternatively, at least one of the first and second anchor parts
may include a snubber portion which physically limits an extent of
relative radial movement between the first and second anchor parts.
For example, the first anchor part may include a protrusion
arranged to abut or impact the second anchor part when a spacing
(i.e. distance) between the first and second anchor parts falls
below a predefined amount which is defined by a shape/dimension
(e.g. radial length) of the protrusion. Alternatively, the second
anchor part may include the protrusion. Furthermore, the first
anchor part may include a first protrusion and the second anchor
part may include a second protrusion, and the first and second
protrusions may be arranged to abut or impact each other when a
spacing (i.e. distance) between the first and second anchor part
falls below a predefined amount which is defined by the combined
dimensions (e.g. radial lengths) of the first and second
protrusions.
[0020] In another example, the first anchor part may be a boss
element and the second anchor part may be a cup element arranged to
receive the boss element therein. The boss element may be an
elongate, e.g. rod-like, structure extending along the longitudinal
axis of the bush. The cup element may be a generally cylindrical
structure that defines a cavity within which the boss element is
receivable. In this example, the first resilient body, second
resilient body and inertial mass element may together form a
frustoconical interconnection between the boss element and the cup
element. The inertial mass element may comprise a rigid separating
portion, e.g. in the form or a plate or the like, which physically
separates the first resilient body from the second resilient body.
The rigid separating portion may be an annular planar element
extending circumferentially around the bush. A normal of the plane
of the planar element may be inclined to the longitudinal axis.
[0021] The inertial mass element may comprise a snubber portion for
limiting relative axial movement between the boss element and the
cup element. The snubber portion may comprise a radially extending
surface, e.g. plate, that is arranged to abut either the cup
element or boss element if relative movement therebetween exceeds a
threshold. For example, the cup element may comprise a top flange
arranged to abut the snubber portion to restrict an axial distance
by which the boss element is movable into the cup element.
[0022] In use, the first anchor part may be connected to a first
machine component and the second anchor part may be connected to a
second machine component, whereby the bush is operable to isolate
vibrations between the first machine component and second machine
component. In an embodiment, both the first and second machine
components may vibrate; however, in at least some other embodiments
either the first or the second machine component may be fixed (i.e.
cannot vibrate). The bush may be configured for use in any suitable
field. For example, the first machine component and second machine
component are the engine and chassis of a vehicle.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Embodiments of the invention are discussed in detail with
reference to the accompanying drawings, in which:
[0024] FIG. 1 is a perspective view of a bush that is an embodiment
of the present invention;
[0025] FIGS. 2A and 2B show cross-sectional views of the bush of
FIG. 1;
[0026] FIG. 3 is a graph showing dynamic stiffness against
frequency for a known bush and a bush that is an embodiment of the
present invention;
[0027] FIG. 4 is a cross-sectional view of a known vertically
mounted bush;
[0028] FIG. 5 is a cross-sectional view of a vertically mounted
bush that is another embodiment of the present invention;
[0029] FIG. 6 is a cross-sectional view of a vertically mounted
bush that is another embodiment of the present invention;
[0030] FIG. 7 is a perspective view of a bush that is a further
embodiment of the present invention;
[0031] FIGS. 8A and 8B show cross-sectional views of the bush of
FIG. 7;
[0032] FIG. 9 is a graph showing dynamic stiffness against
frequency for the bush of FIG. 7;
[0033] FIG. 10A is a perspective view of a first end of a bush that
is another further embodiment of the present invention;
[0034] FIG. 10B is a perspective view of a second end of the bush
of FIG. 10A;
[0035] FIGS. 10C and 10D show cross-sectional views of the bush of
FIG. 10A;
[0036] FIG. 11A is a perspective view of a first end of a bush that
is yet another further embodiment of the present invention;
[0037] FIG. 11B is a perspective view of a second end of the bush
of FIG. 11A; and
[0038] FIGS. 11C and 11D show cross-sectional views of the bush of
FIG. 11A.
DETAILED DESCRIPTION OF THE DRAWINGS
[0039] FIG. 1 is a perspective view of a bush 100 that is a first
embodiment of the present invention. The bush 100 is a generally
cylindrical structure that defines a longitudinal axis. FIG. 2A
shows a cross-section of the bush 100 perpendicular to the
longitudinal axis. FIG. 2B shows a cross-section of the bush 100
parallel to the longitudinal axis.
[0040] The bush 100 comprises a series of components arranged
coaxially around the longitudinal axis. The components include a
first anchor part 110 that is surrounded by and operably engaged
with an inner resilient body 114. The inner resilient body 114 is
surrounded by and operably engaged with an inertial mass element
118. The inertial mass element 118 is surrounded by and operably
engaged with an outer resilient body 116, which in turn is
surrounded by and operably engaged with a second anchor part 112.
The function of each part will be described in more detail below.
The bush 100 may have open end faces, as depicted in FIG. 1, or the
end faces of the bush 100 may be partially or entirely covered. The
bush may include fluid, e.g. hydraulic fluid, within voids defined
in one or both of the resilient bodies.
[0041] The first anchor part 110 comprises a rigid rod, which may
be a hollow tube, made from any suitable material, e.g. a metal
such as steel. The first anchor part 110 is configured to be
attached to a first component of vibrating machinery (not shown) in
any conventional manner. In one example, the first anchor part 110
may have an inner diameter of 12 mm and an outer diameter of 25 mm,
although the invention may be applicable to bushes having any
dimensions.
[0042] The second anchor part 112 comprises a rigid sleeve, e.g.
formed from metal or the like, disposed coaxially with the first
anchor part 110 to define an annular space therebetween. The second
anchor part 112 is configured to be attached to a second component
of vibrating machinery (not shown). In one example, the second
anchor part 112 may have an inner diameter of 105 mm and an outer
diameter of 110 mm. The bush 100 may thereby be used as a mounting
device between two components. For example, the first component may
be an engine or motor and the second component may be the chassis
of a vehicle. The bush 100 may be particularly suitable for use
between the drive unit and chassis in an electric vehicle.
[0043] Concentric with the first anchor part 110 and the second
anchor part 112 in the annular space therebetween, an inner
resilient body 114 and an outer resilient body 116 are provided.
The inner resilient body 114 and outer resilient body 116 may each
be made of a resiliently deformable material such as rubber. The
inner resilient body 114 and outer resilient body 116 may be formed
from the same or different materials. In one example, the resilient
material may be rubber having a hardness of between 45 and 50 as
measured with a Shore A durometer.
[0044] The inner resilient body 114 and outer resilient body 116
are separated from each other by an inertial mass element 118,
which in this example is a rigid annular element mounted between an
outer surface of the inner resilient body 114 and an inner surface
of the outer resilient body 116.
[0045] The inner resilient body 114, the inertial mass element 118,
and the outer resilient body 116 may operate together to isolate
vibrations between the first anchor part 110 and the second anchor
part 112. In this way, the first component may be isolated from
vibrations of the second component, and vice versa, by
interconnecting the two components using the bush 100.
[0046] The inner resilient body 114 and the outer resilient body
116 may operate as independent springs on either side of the
inertial mass element 118. The shape, material and configuration of
the inner resilient body 114 may be selected so that the bush 100
exhibits a desirable dynamic stiffness characteristic, as discussed
below. The outer resilient body 116 may be configured as a movement
limiter to provide a level of control for significant relative
movement events between the first and second anchor parts 110, 112,
e.g. due to acceleration loads, pot hole events, cornering, crash,
etc. In combination, the outer resilient body 116 combined with the
snubbers 120 define a static stiffness curve which is tuned to give
certain stiffness for a given force applied.
[0047] The inner resilient body 114 may comprise a solid rubber
element filling the annular volume between the first anchor part
110 and the inertial mass element 118. The inner resilient body 114
may be directly moulded between these two components.
[0048] In some examples, the inner resilient body 114 may be bonded
to one or both of the first anchor part 110 and the inertial mass
element 118. For example, an inner bush formed by first anchor part
110 bonded to inner resilient body 114 may be push-fitted into
inertial mass element 118 to increase durability. Similarly it
could be desirable to push fit the first anchor part 110 into a
bush sub-assembly formed by the inertial mass element 118 bonded to
the outer resilient body 116 to increase durability. The increase
in durability comes from pre-compressing the rubber to remove
residual stresses caused by the rubber shrinking following
moulding.
[0049] One or both of the inner resilient body 114 and outer
resilient body 116 could either have voids/passageways or be solid
rubber, as required by the desired stiffness characteristic.
[0050] The outer resilient body 116 made have one or more axial
passageways or voids extending therethrough. In other words it need
not completely fill the annular volume between an outer surface of
the inertial mass element 118 and an inner surface of the second
anchor part 112. The passageways or voids in the outer resilient
body 116 may operate as buffers or snubbers 120, 122 arranged to
cushion large relative movements of the first component and/or the
second component.
[0051] In this embodiment, the inertial mass element 118 is a rigid
cylinder, e.g. made of a metal such as steel. The material and/or
dimensions of the inertial mass element 118 may be selected in
conjunction with the spring properties of the inner and outer
resilient bodies 114, 116 so that the inertial mass exhibits a
resonance condition at a vibration frequency outside (e.g. below)
the intended usage range of the bush. Under normal use of the bush,
the inertial mass element 118 thus occupies a non-resonant
condition in which it isolates the dynamic stiffness increases
associated with the eigenmodes of the inner and outer resilient
bodies 114, 116. That is, each of the inner resilient body 114 and
outer resilient body 116 have independent resonant frequencies, or
eigenmodes, at which their dynamic stiffness increases. At
vibration frequencies corresponding to these eigenmodes, the
isolating effect provided by the inner resilient body 114 or the
outer resilient body 166 is normal decreased. However, the presence
of inertial mass element 118 acts to reduce or remove these
stiffness increases from the overall dynamic stiffness
characteristic of the bush 100 to provide a substantially flat
dynamic stiffness characteristic for the bush as a whole. The
inertial mass element 118 therefore ensures that the bush 100
effectively isolates vibrations of a first component of vibrating
machinery from a second component of vibrating machinery across an
operating frequency range of each component.
[0052] In one non-limiting example, the inertial mass element may
have a mass of around 400 g. For example, the inner diameter of the
inertial mass element 118 may be 55 mm and the outer diameter may
be 65 mm.
[0053] FIG. 3 shows a graph of dynamic stiffness against frequency
for a known bush and a bush according to the present invention,
such as bush 100 shown in FIGS. 1 and 2A-2B.
[0054] As can been seen in FIG. 3, a dynamic stiffness
characteristic 140 for a known bush exhibit stiffness peaks 150,
152 corresponding to eigenmodes at approximately 1000 Hz and 2000
Hz. These peaks represent reduced vibrational isolation between two
components interconnected by the bush. Where the bush is used to
mount an engine or motor to the chassis of a vehicle, in one
example, this may result in an uncomfortable ride for passengers.
It is therefore desirable to reduce or eliminate the stiffness
increases in the bush at these frequencies, and provide a bush
having eigenmodes which lie outside a frequency range associated
with normal operation of interconnected components.
[0055] A bush such as that shown in FIGS. 1 and 2A-2B, may have a
dynamic stiffness characteristic 142 that exhibits a single peak
154 at a lower frequency, e.g. less than 500 Hz. Preferably this
peak occurs at a frequency below 400 Hz. This peak is the
eigenmode, or resonance peak, of the inertial mass between the
inner resilient body and the outer resilient body. Preferably this
eigenmode is at a frequency below the operating frequency range of
the first component or the second component which are
interconnected by the bush. The resonant frequency of the inertial
mass element is dependent on the mass of that element, and also on
the size or material of the inner resilient body and the outer
resilient body. By adjusting these parameters, the eigenmode of the
inertial mass element may be `tuned` to a desired frequency.
[0056] The presence of the inertial mass element in the bush
reduces or eliminates increases dynamic stiffness above the
resonant frequency of the inertial mass element itself. That is,
there are no peaks in dynamic stiffness of the bush due to either
the inner resilient body or the outer resilient body. Vibrations
are therefore effectively isolated by a bush according to the
present invention across a broad range of vibration frequencies.
Preferably this broad range covers the operating frequency range of
a first component and a second component to be interconnected. For
example, where a bush is used to interconnect an engine or motor
and a chassis of a vehicle, use of a bush according to the present
invention ensures passenger comfort.
[0057] FIG. 4 shows a cross-sectional view of a known vertically
mounted bush 200. The bush 200 is generally cylindrical and
comprises a first anchor part 210 and a second anchor part 212. The
first anchor part 210 comprises a rigid boss element configured for
attachment to a first component of vibrating machinery, and the
second anchor part 212 comprises a cup element for receiving the
boss element. The second anchor part 212 has an attachment region
such as flange 213 configured for attachment to a second component
of vibrating machinery. The second anchor part 212 is concentric
with, and spaced apart from, the first anchor part 210 to define a
generally annular region between the first anchor part 210 and the
second anchor part 212. A ring of resiliently deformable material
214, such as rubber is disposed within this annular region to
connect the first anchor part 210 and the second anchor part
212.
[0058] As the two components affixed to the bush 200 vibrate
relative to each other, the ring of resilient material 214 deforms
to isolate the vibration. However, the resilient material 214 has
one or more eigenmodes at which the dynamic stiffness of the
resilient material 214 increases, reducing vibrational isolation
between the interconnected components.
[0059] Relative movement between two interconnected components is
limited in the vertical (Z) direction, as viewed in FIG. 4, by an
upper snubber plate 216 and a lower snubber plate 218.
[0060] The upper snubber plate 216 is connected to an upper end of
the first anchor part 210, and limits the range of movement of the
first anchor part 210 relative to the second anchor part 212 in a
first direction (downwards as viewed in FIG. 4). The upper snubber
plate 216 is sized to abut a snubbing surface 220 on the second
anchor part 212 if relative movement in the first direction exceeds
a threshold.
[0061] The lower snubber plate 218 is connected to a bottom end of
the first anchor part 210, and limits the range of movement of the
first anchor part 210 relative to the second anchor part 212 in a
second direction that is opposite to the first direction (i.e.
upwards as viewed in FIG. 4). The lower snubber plate 218 is sized
to abut an interior wall of the second anchor part 212 if relative
movement between the first anchor part 210 and second anchor part
212 in the second direction exceeds a threshold.
[0062] FIG. 5 shows a cross-sectional view of a vertically mounted
bush 300 that is another embodiment of the present invention.
[0063] Similarly to the embodiment discussed above with reference
to FIGS. 1 to 3, the anchor elements in bush 300 are connected to
each other via a first resilient body 314 and second resilient body
316 with an inertial mass element 318 disposed between the first
resilient body 314 and second resilient body 316. In this example,
the first resilient body 314 is an annular element formed around,
e.g. bonded to, a surface of the first anchor part 310. The first
resilient body 314 may be bonded to an inclined surface of the
first anchor part 310. The inclined surface may be in the form of a
frustocone. The second resilient body 316 may be an annular element
formed on, e.g. bonded to, a surface of the second anchor part 312.
The second resilient body 316 may be bonded to an inclined surface
of the second anchor part 312. The inclined surface may be angled
in a similar manner to the frustoconical surface of the first
anchor part 310, whereby the first resilient body 314 and second
resilient body 316 cooperate to bridge a gap between the first
anchor part 310 and second anchor part 312. The angled nature of
the first and second resilient bodies may enable the bush to
isolate vibrations having a radial and axial components.
[0064] The inertial mass element 318 in this example comprises a
rigid annular plate portion 320 that separates the first resilient
body 314 from the second resilient body 316. The rigid annular
plate portion may by inclined such that a normal to its plane lies
at an acute angle to an axis of the bush 300 and in line with a
direction in which the first resilient body 314 and second
resilient body 316 bridge a gap between the first anchor part 310
and second anchor part 312.
[0065] The inertial mass element 318 may also comprise a snubber
portion 322 for restricting the extent of relative axial movement
between the first anchor part 310 and second anchor part 312. In
this example, the snubber portion is an annular flange that extends
in a radial direction from an outer circumferential edge of the
rigid annular plate portion away from the first and second
resilient bodies. The second anchor part 312 may have a top flange
324 that extends in a radial direction. The annular flange may abut
the top flange to restrict the distance by which the first anchor
part 310 can move into the second anchor part 312.
[0066] In this example, the inertial mass element 318 may thus
perform two functions. Firstly it can operate to reduce or remove
dynamic stiffness increases in the bush 300 due to eigenmodes of
the first resilient body 314 and second resilient body 316, in a
similar manner as the inertial mass element 118 of bush 100
described above with respect to FIGS. 1 to 3. Secondly, it can
operate to restrict relative axial movement between the first and
second anchor parts 310, 312 in a similar manner to the upper
snubber part 216 discussed above with reference to FIG. 4.
[0067] FIG. 6 shows a cross-sectional view of a vertically mounted
bush 400 that is another embodiment of the present invention.
[0068] In this embodiment, a first anchor part 402 is connected to
a vibrating element (e.g. motor) and a second anchor part 404 is
connected to a chassis. The second anchor part 404 is a central rod
member of a hydraulically damped vertical travel limiter. The
second anchor part 404 is secured within a housing 410 by a first
resilient body 408, which is disposed between the second anchor
part 404 and rigid rings 412, 414 that are fixed within the housing
410.
[0069] The housing 410 is secured to the first anchor part 402 by a
second resilient body 406, e.g. a rubber sleeve or the like.
[0070] The inertial mass element in this example comprises a
combination of the components of the hydraulically damped vertical
travel limiter disposed between the first resilient body 408 and
the second resilient body 406, i.e. the housing 410, rigid rings
412, 414 and hydraulic fluid 416 within the housing 410. Thus, in
additional to performing its normal function to limit vertical
travel, the hydraulically damped device in FIG. 6 also provides an
inertial mass to isolate the engine from the chassis
[0071] FIG. 7 is a perspective view of a bush 500 that is a further
embodiment of the present invention. The bush 500 is a generally
cylindrical structure that defines a longitudinal axis. FIG. 8A
shows a cross-section of the bush 500 perpendicular to the
longitudinal axis. FIG. 8B shows a cross-section of the bush 500
parallel to the longitudinal axis.
[0072] The bush 500 is a modified version of the bush 100 shown in
FIG. 1. Therefore, in the following, a description of the bush 500
is provided which focusses on the aspects of bush 500 which differ
from the bush 100 of FIG. 1. Unless otherwise stated, it is to be
understood that the structure and operation of the bush 500 is the
same as the structure and operation of the bush 100 of FIG. 1.
[0073] The bush 500 has an inner resilient body 514 which includes
one or more axial passageways or voids extending therethrough. In
other words, the material of the inner resilient body 514 may not
completely fill the annular volume between an inner surface of the
inertial mass element 118 and an outer surface of the first anchor
part 110. The portions of the inner resilient body 514
circumferentially in-between the passageways may be referred to as
"legs". The passageways facilitate relative movement between the
first and second anchor parts during loading.
[0074] The passageways in the inner resilient body 514 may include
buffers or snubbers 520 to physically limit the extent of relative
radial movement between the first and second anchor parts.
Specifically, the snubbers 520 are arranged to restrict and cushion
large relative movements (e.g. radial movements) of the first
component (coupled to the first anchor 110) and/or the second
component (coupled to the second anchor 112). For instance, the
snubbers 520 restrict and cushion movements so as to protect the
legs from becoming over-compressed and/or over-extended, which
would otherwise reduce the lifespan of the bush 500. In the
embodiment shown in FIG. 7, the snubbers 520 have a substantially
"u" or "n" shaped cross section. Also, the passageways are
substantially "u" or "n" in cross-section. However, it is to be
understood that in some other embodiments, the snubbers or
passageways could have a different shaped cross-section.
[0075] In view of the above-described structure, the inner
resilient body 514 may be configured as a movement limiter to
provide a level of control for significant relative movement (e.g.
radial movement) events between the first and second anchor parts
110, 112, e.g. due to acceleration loads, pot hole events,
cornering, crash, etc. In combination, the inner resilient body 514
combined with the snubbers 520 define a static stiffness curve
which is tuned to give certain stiffness for a given force
applied.
[0076] The inner resilient body 514 and the outer resilient body
116 may operate as independent springs. Since the inner and outer
resilient bodies have corresponding structures, e.g. they both
include passageways with snubber portions, the bush 500 is balanced
and provides balanced vibration isolation because the inner and
outer resilient bodies have substantially the same spring
characteristics. For example, the passageways with snubber portions
mean that both the inner and outer resilient bodies (514, 116) have
a relatively soft spring characteristic, compared to the embodiment
of FIG. 1 in which the outer resilient body 116 (with passages) is
relatively soft but the inner resilient body 114 (without passages)
is relatively hard.
[0077] It is to be understood that the spring characteristics of a
resilient body will depend on the number of passages and the number
of snubber portions that the resilient body has. Therefore, in
order that the bush 500 remains balanced, the inner and outer
resilient bodies may have the same number of passageways and
snubber portions. Also, the general shape of the passages and
snubber portions may be same in the inner resilient body 514 and
the outer resilient body 116, although the dimensions of the inner
resilient body 514 will be less than those of the outer resilient
body 116.
[0078] For example, under normal operating conditions, loading on
the bush 500 at the first and second anchor parts causes the
passageways to distort to permit relative radial movement between
the first and second anchor parts so as to isolate vibrations.
Under these normal conditions, the distortion of the passageways
may be insufficient to cause the snubbers 520 to physically limit
the extent of relative radial movement between the first and second
anchors. For instance, the number of passageways and/or snubbers,
and/or the dimensions/shape of the passageways and/or snubbers may
be chosen so that, under normal operating conditions, the
passageways distort without using the snubbers 520. However, under
abnormal operating conditions, loading on the bush 500 at the first
and second anchor parts causes the passageways to distort to such
an extent that the snubbers 520 physically limit the extent of
relative radial movement between the first and second anchor parts.
Under these abnormal conditions, the snubbers 520 protect the
resilient bodies from over-compression and over-extension to
prolong the operational life of the bush 500. Also, the snubbers
520 control a maximum displacement of the first and second anchor
parts to reduce the chance that they (and the components to which
they are fixed) will hit neighbouring components and cause damage.
For instance, the number of passageways and/or snubbers, and/or the
dimensions/shape of the passageways and/or snubbers may be chosen
so that, under abnormal operating conditions, the passageways
distort to such an extent that the snubbers 520 are used. In an
example, the bush 500 may be used in an electric vehicle (e.g.
car), and the normal operating conditions may include maintaining a
cruising speed (e.g. 50 km/h to 100 km/h) on a motorway. On the
other hand, the abnormal operating conditions may include:
accelerating the car from a stationary start with maximum
acceleration, performing an emergency stop, or driving over rough
surfaces (e.g. pot holes, cobble stones).
[0079] FIG. 9 shows a graph of dynamic stiffness against frequency
for the bush 500 shown in FIGS. 7 and 8A-8B. The graph of FIG. 9
corresponds with that of FIG. 3.
[0080] As seen on FIG. 9, the bush 500 may have a dynamic stiffness
characteristic 550 that exhibits a single peak 552 at a lower
frequency, e.g. less than 500 Hz. Preferably this peak occurs at a
frequency below 400 Hz. This peak is the eigenmode, or resonance
peak, of the inertial mass between the inner resilient body and the
outer resilient body. Preferably this eigenmode is at a frequency
below the operating frequency range of the first component or the
second component which are interconnected by the bush. The resonant
frequency of the inertial mass element is dependent on the mass of
that element, and also on the size, shape or material of the inner
resilient body and the outer resilient body. By adjusting these
parameters, the eigenmode of the inertial mass element may be
`tuned` to a desired frequency.
[0081] The presence of the inertial mass element in the bush
reduces or eliminates increases in dynamic stiffness above the
resonant frequency of the inertial mass element itself. That is,
there are no peaks in dynamic stiffness of the bush due to either
the inner resilient body or the outer resilient body. More
specifically, the modifications to bush 500, i.e. the introduction
of passages with snubber portions 520 into the inner resilient body
514 has improved the vibration isolation performance, as can be
seen by comparing the higher frequency portion of dynamic stiffness
characteristic 550 of FIG. 9 with the higher frequency portion of
dynamic stiffness characteristic 142 of FIG. 3. It is clearly
visible that the characteristic 550 maintains a more consistent and
reduced dynamic stiffness over higher frequencies compared to the
characteristic 142. For example, see the region of characteristic
550 highlighted by the reference sign 554.
[0082] In view of the above, vibrations are therefore effectively
isolated by the bush 500 across a broad range of vibration
frequencies. Preferably this broad range covers the operating
frequency range of a first component and a second component to be
interconnected. For example, where the bush 500 is used to
interconnect an engine or motor and a chassis of a vehicle, use of
the bush 500 ensures passenger comfort.
[0083] FIG. 10A is a perspective view of a bush 600 that is a
further embodiment of the present invention. The bush 600 is a
generally cylindrical structure that defines a longitudinal axis.
FIG. 10A shows a first end of the bush 600, whereas FIG. 10B shows
a second, opposite end of the bush 600. FIG. 10C shows a
cross-section of the bush 600 perpendicular to the longitudinal
axis. FIG. 10D shows a cross-section of the bush 600 parallel to
the longitudinal axis.
[0084] The bush 600 is a modified version of the bush 100 shown in
FIG. 1. Therefore, in the following, a description of the bush 600
is provided which focusses on the aspects of bush 600 which differ
from the bush 100 of FIG. 1. Unless otherwise stated, it is to be
understood that the structure and operation of the bush 600 is the
same as the structure and operation of the bush 100 of FIG. 1.
[0085] The bush 600 has an inner resilient body 614 which includes
one or more axial passageways or voids extending therethrough. In
other words, the material of the inner resilient body 614 may not
completely fill the annular volume between an inner surface of the
inertial mass element 118 and an outer surface of the first anchor
part 110. The portions of the inner resilient body 614
circumferentially in-between the passageways may be referred to as
"legs". The passageways facilitate relative movement between the
first and second anchor parts during loading.
[0086] The bush 600 has an outer resilient body 616 having a
structure similar to that of the inner resilient body 614. That is,
the outer resilient body 616 has one or more axial passageways or
voids extending therethrough.
[0087] In contrast to the bush 500, the passageways or voids of the
bush 600 may not include any buffers or snubbers. Instead, as seen
more particularly on FIG. 10A and 10D, the second anchor part 112
includes a snubber portion 620 which is arranged to physically
limit an extent of relative radial movement between the first
anchor part 110 and the second anchor part 112. Specifically, the
snubber portion 620 may be formed from a protrusion which extends
radially towards the first anchor part 110. The snubber portion 620
may have a substantially annular or ring-shaped form, as seen most
clearly on FIG. 10A. The protrusion extends only part way towards
the first anchor part 110 so as to permit some radial movement
between the first and second anchor parts. That is, a radial length
of the snubber 620 may be selected so as to permit radial movement
up to a predetermined amount. As seen on FIG. 10D, a tip portion of
the protrusion may be constructed from a different material than
the rest of the snubber 620. For example, the tip portion may be
made from a resilient material (e.g. rubber) whereas the rest of
the snubber 620 may be made from a rigid material (e.g. metal).
Alternatively, the whole snubber 620 may be made from a single
material, such as a resilient material, like rubber.
[0088] In use, the snubber 620 is arranged to restrict and cushion
large relative movements (e.g. radial movements) of the first
component (coupled to the first anchor 110) and/or the second
component (coupled to the second anchor 112). For instance, the
snubber 620 restricts and cushions movements so as to protect the
legs of the first and second resilient bodies from becoming
over-compressed and/or over-extended, which would otherwise reduce
the lifespan of the bush 600.
[0089] In view of the above-described structure, the snubber 620 is
configured as a movement limiter to provide a level of control for
significant relative movement (e.g. radial movement) events between
the first and second anchor parts 110, 112, e.g. due to
acceleration loads, pot hole events, cornering, crash, etc. In
combination, the snubber 620, the inner resilient body 614, and the
outer resilient body 616 define a static stiffness curve which is
tuned to give certain stiffness for a given force applied.
[0090] The inner resilient body 614 and the outer resilient body
616 may operate as independent springs. Since the inner and outer
resilient bodies have corresponding structures, e.g. they both
include passageways without snubber portions, the bush 600 is
balanced and provides balanced vibration isolation because the
inner and outer resilient bodies have substantially the same spring
characteristics.
[0091] It is to be understood that the spring characteristics of a
resilient body will depend on the number of passages that the
resilient body has. Therefore, in order that the bush 600 remains
balanced, the inner and outer resilient bodies may have the same
number of passageways. Also, the general shape of the passages may
be same in the inner resilient body 614 and the outer resilient
body 616, although the dimensions of the inner resilient body 614
will be less than those of the outer resilient body 616.
[0092] For example, under normal operating conditions, loading on
the bush 600 at the first and second anchor parts causes the
passageways to distort to permit relative radial movement between
the first and second anchor parts so as to isolate vibrations.
Under these normal conditions, the distortion of the passageways
may be insufficient to cause the snubber 620 to impact the first
anchor part 110. As such, the snubber 620 does not physically limit
the extent of relative radial movement between the first and second
anchors. For instance, the number of passageways, and/or the
dimensions/shape of the passageways and snubber 620 may be chosen
so that, under normal operating conditions, the passageways distort
without using the snubber 620. However, under abnormal operating
conditions, loading on the bush 600 at the first and second anchor
parts causes the passageways to distort to such an extent that the
snubber 620 physically limits the extent of relative radial
movement between the first and second anchor parts (i.e. the
snubber 620 hits the first anchor 110). Under these abnormal
conditions, the snubber 620 protects the resilient bodies from
over-compression and over-extension to prolong the operational life
of the bush 600. Also, the snubber 620 controls a maximum
displacement of the first and second anchor parts to reduce the
chance that they (and the components to which they are fixed) will
hit neighbouring components and cause damage. For instance, the
number of passageways, and/or the dimensions/shape of the
passageways and snubber 620 may be chosen so that, under abnormal
operating conditions, the passageways distort to such an extent
that the snubber 620 is used. In an example, the bush 600 may be
used in an electric vehicle (e.g. car), and the normal operating
conditions may include maintaining a cruising speed (e.g. 50 km/h
to 100 km/h) on a motorway. On the other hand, the abnormal
operating conditions may include: accelerating the car from a
stationary start with maximum acceleration, performing an emergency
stop, or driving over rough surfaces (e.g. pot holes, cobble
stones).
[0093] An advantage of the snubber 620 compared to the snubbers 120
and 520, is that the snubber 620 directly acts on the anchor parts
because the snubber 620 is directly attached to the second anchor
part 112 and directly impacts the first anchor part 110. On the
other hand, the snubbers 120 and 520 are located in passages of the
resilient bodies and so their snubbing effect is indirect because
these snubbers do not attach to or impact the anchor parts
directly. Also, the snubbers 120 and 520 perform their snubbing
effect through the inertial mass element 118. Conversely, the
snubbing effect of the snubber 620 is independent of the inertial
mass element 118. Accordingly, when using the snubber 620, the
inertial mass element 118 has minimal or no major stiffness rise
(as in the embodiment of FIGS. 1, 2A and 2B) allowing the frequency
peak to remain stable under normal as well as abnormal operating
conditions.
[0094] FIG. 11A is a perspective view of a bush 700 that is a
further embodiment of the present invention. The bush 700 is a
generally cylindrical structure that defines a longitudinal axis.
FIG. 11A shows a first end of the bush 700, whereas FIG. 11B shows
a second, opposite end of the bush 700. FIG. 11C shows a
cross-section of the bush 700 perpendicular to the longitudinal
axis. FIG. 11D shows a cross-section of the bush 700 parallel to
the longitudinal axis.
[0095] The bush 700 is a modified version of the bush 600 shown in
FIGS. 10A-D. Therefore, in the following, a description of the bush
700 is provided which focusses on the aspects of bush 700 which
differ from the bush 600 of FIGS. 10A-D. Unless otherwise stated,
it is to be understood that the structure and operation of the bush
700 is the same as the structure and operation of the bush 600 of
FIGS. 10A-D.
[0096] As seen on FIGS. 11A and 11D, the first anchor part 110
includes a snubber portion 720 which is arranged to physically
limit an extent of relative radial movement between the first
anchor part 110 and the second anchor part 112. Specifically, the
snubber portion 720 may be formed from a protrusion which extends
radially towards the second anchor part 112. The snubber portion
720 may have a substantially annular or ring-shaped form, as seen
most clearly on FIG. 11A. The protrusion extends only part way
towards the second anchor part 112 so as to permit some radial
movement between the first and second anchor parts. That is, a
radial length of the snubber 720 may be selected so as to permit
radial movement up to a predetermined amount. As seen on FIG. 11D,
a tip portion of the protrusion may be constructed from a different
material that the rest of the snubber 720. For example, the tip
portion may be made from a resilient material (e.g. rubber) whereas
the rest of the snubber 720 may be made from a rigid material (e.g.
metal). Alternatively, the whole snubber 720 may be made from a
single material, such as a resilient material, like rubber.
[0097] In use, the snubber 720 is arranged to restrict and cushion
large relative movements (e.g. radial movements) of the first
component (coupled to the first anchor 110) and/or the second
component (coupled to the second anchor 112). For instance, the
snubber 720 restricts and cushions movements so as to protect the
legs of the first and second resilient bodies from becoming
over-compressed and/or over-extended, which would otherwise reduce
the lifespan of the bush 700.
[0098] It is to be understood that in some other embodiments, the
bush may include both snubbers within passageways, as per FIGS. 2A
or 8A, and snubbers outside of passageways, as per FIGS. 10D or
11D.
[0099] Additionally, in some other embodiments, the bush may
include both the snubber 620 of FIG. 10D and the snubber 720 of
FIG. 11D. Specifically, each snubber 620, 720 may extend towards
each other but be dimensioned such that, under normal operating
conditions, a gap or space is maintained between the snubbers 620,
720. Then, under abnormal operating conditions, the snubber 620 may
impact the snubber 720 so as to physically limit an extent of
relative radial movement between the first and second anchor parts.
Of course, the snubbers 620, 720 may have the same or different
radial lengths.
[0100] Further, in some other embodiments, the snubber 620 or 720
may be positioned at or near a middle of the bush. For instance,
taking the example of FIG. 11D, the snubber 620 may be attached to
the first anchor 110 half way along its length. Also, the inner
resilient body 614, the inertial mass element 118, and the outer
resilient body 616 may be split into two halves (e.g. via a cut
perpendicular to a longitudinal axis of the first anchor 110) with
the first half being positioned on the left side of the snubber
620, and the second half being positioned on the right side of the
snubber 620. A similar modification could be made to the example of
FIG. 10D.
* * * * *