Liquid sealed rubber mount

This invention relates to a liquid sealed rubber mount capable of displaying an excellent vibration isolating effect in intermediate and high frequency ranges, having a vibration isolating effect with no resonation occurring with respect to even the impact vibration of a wide frequency band, capable of obtaining a large attenuation force for large amplitude vibration, and capable of preventing the occurrence of lateral vibration. Accordingly, a case (11, 51) and a guide shaft (14) are joined to each other by a cylindrical rubber mounting element (17, 58), and a high attenuation liquid (21, 59) is sealed in a liquid sealing chamber housing (20, 53) fixed to a lower end of the case (11, 51), a damper plate (23, 28, 55) being held on a lower end of the guide shaft (14). An elastic member (24, 26, 34, 35, 36a, 36b, 39, 56), which is deformed finely by the distance a due to the resistance of the high attenuation liquid (21, 59) when vertical vibration occurs, is fixed the damper plate (23, 28, 55). When intermediate and high frequency vibration, the amplitude of which is not more than .+-.a, occurs, the elastic member (24, 26, 34, 35, 36a, 36b, 39, 56) is deformed and is not attenuated, and a vibration isolating action occurs owing to the rubber mounting element (17, 58). When low frequency vibration, the amplitude of which is in excess of .+-.a, occurs, the damper plate (23, 28, 55) and elastic member (24, 26, 34, 35, 36a, 36b, 39, 56) are moved unitarily, and an attenuation force occurs. The cylindrical rubber mounting element (58) can be a cylindrically laminated structure provided with one or more cylindrical laminate plates (57) positioned therein.

TECHNICAL FIELD 
This invention relates to a liquid sealed rubber mount for vibration 
isolating action and, in particular, to a liquid sealed rubber mount 
suitable for mounting an operating cabin or cab on a body for preventing 
the occurrence of vibration. 
BACKGROUND OP THE INVENTION 
A rubber mount includes a shock absorbing member, e.g., made of rubber, 
between a vibration source such as a car body and a vibration receiving 
object such as a cab, for reducing vibration of the cab with a vibration 
isolating effect. A description will be made at first with respect to a 
common dump truck with reference to FIG. 1, showing, a general structure 
of the dump truck on which the cab is mounted. In FIG. 1, brackets 3 and 4 
are fixed to a frame 2 of the dump truck 1, on which a floor 6 of the cab 
5 is mounted through a vibration isolating mount 10 so as to prevent the 
vibration from being directly transmitted to the cab 5 from a road surface 
or the like. FIG. 2 is a partial detail of the part P shown in FIG. 1, in 
which a case 11 of the vibration isolating mount 10 is fastened to the 
bracket 4 with bolts 12 and nuts 13. A guide shaft 14 of the vibration 
isolating mount 10 is then tightened to the floor 6 with a nut 15 so as to 
mount the cab 5 thereon for preventing the occurrence of vibration. 
FIG. 19 is a sectional side view of a conventional liquid sealed mount 
(e.g., see Japanese utility model laid-open publication No. 64-12946) 
which is often used in the art as a rubber mount. In the liquid sealed 
mount 60, a case 61 and a boss 63, having a bolt 62, are joined to each 
other by the rubber mounting element 64. A rubber diaphragm 65, having an 
orifice 66 therein, is held on a lower end of the boss 63, the 
circumference of which is fixed to the case 61. The rubber diaphragm 65 
divides the case 61 into a chamber 67 and a chamber 68. A liquid is then 
sealed in both the chamber 67 and the chamber 68 in communication with 
each other through the orifice 66. When a vertical vibration load is 
applied, the relative displacement of the case 61 and the boss 63 occurs 
while deforming the rubber mounting element 64. At this moment, the liquid 
69 moves between the chamber 67 and the chamber 68 through the orifice 66 
so that the vibration can be attenuated by the power of the resistance of 
the liquid passing through the orifice 66. 
The attenuation characteristics of such a liquid sealed mount 60, which 
depend upon the diameter or the passing flow rate of the orifice, are 
shown in FIG. 22. In that drawing, the solid lines indicate the 
characteristics of the liquid sealed mount 60, each exhibiting a 
relationship between frequency and loss factor for an input amplitude of 
.+-.0.2 mm or .+-.3.0 mm. As shown in FIG. 22, an excellent vibration 
isolating effect can be obtained in certain frequency ranges across a 
frequency of 10 Hz, whereas the loss factor values are small in the other 
frequency ranges, such that resonation is induced with respect to the 
input vibration, such as the impact vibration of a wide frequency band, 
with no vibration isolating effect. Further, lateral vibration can occur 
due to the lack of any lateral attenuation action. 
Next, a description will be made with respect to another prior art. FIG. 20 
is a sectional side view of a viscous mount (e.g., see Japanese utility 
model laid-open publication No. 4-101835) which is used as another liquid 
sealed mount, and FIG. 21 is a sectional view taken on line X--X of FIG. 
20. In the viscous mount 70, a case 11 and a guide shaft 14, having a bolt 
16 therein, are joined to each other by a rubber mounting element 17 
having a hardness Hs of about 70.degree.. A housing 20 containing a liquid 
sealing chamber is fixed to one end of the case 11, while a damper plate 
23 having a rubber stopper element 32 is fastened by a bolt 22 to a lower 
end of the guide shaft 14 and is held in the liquid sealing chamber in the 
housing 20. A hole 72 is provided through the damper plate 23, and an 
injecting port 71 is provided in the liquid sealing chamber housing 20, 
whereby a high attenuation liquid 21 can be injected through the injecting 
port 71 into the liquid sealing chamber in the housing 20. On the other 
hand, the hole 72 is used to inject the high attenuation liquid 21 from 
the injecting port 71 into the portion of the chamber above the upper side 
of the damper plate 23, the high attenuation liquid 21 having a viscosity 
of about 50,000 to 100,000 cst. 
In such a viscous mount 70, when a vertical vibration load is applied to 
the guide shaft 14, the damper plate 23 stirs the high attenuation liquid 
21 and obtains an attenuation force to attenuate the vibration. The 
attenuation characteristics are indicated by the broken lines in FIG. 22, 
each of these lines exhibiting a relationship between frequency and loss 
factor for an input amplitude of .+-.0.2 mm or .+-.3.0 mm. As shown in the 
drawing, over a wide frequency band the loss factor of the viscous mount 
70 becomes larger than that of the liquid sealed mount 60, and a 
resonation does not occur with respect to even the impact vibration. 
However, an attenuation force of the viscous mount 70, necessary for 
reducing vibration and noise, is small for the large input amplitude and 
becomes large with respect to intermediate and high frequency vibration, 
causing no vibration isolating effect by the viscous mount 70. This 
description assumes the low frequency range to be 20 Hz or less, the 
intermediate frequency range to be about 20 Hz to several hundred Hz, and 
the high frequency range to be several hundred Hz or more. 
In consideration of the above drawback, even if the rubber mounting element 
17 is decreased in hardness and in spring constant to improve the 
vibration isolating effect in the intermediate and high frequency ranges, 
lateral vibration can occur because the deflection with respect to a 
lateral load becomes large. Further, the viscous mount 70 structurally has 
a small attenuation action with respect to the lateral direction such that 
the lateral vibration occurs. This is because the attenuation force with 
respect to the lateral displacement appears only on a projected area of 
the rubber stopper element 32 having a thickness b (see FIG. 20). On the 
contrary, the viscous mount 70 can obtain a large attenuation force with 
respect to the vertical displacement, because the force appears on an area 
of the damper plate 23 having a diameter d (see FIG. 20). In addition, as 
shown in the sectional view of FIG. 21 taken along the line X--X of FIG. 
20, the displacement of the damper plate 23 in a position 23a, indicated 
by a dotted circle, results in less attenuation force because the liquid 
moves smoothly along the circle from the part E to the part F as indicated 
by the arrows. For this reason, lateral vibration can occur more 
frequently; but nevertheless, in order to prevent an interference between 
the rubber stopper element 32 and the liquid sealing chamber housing 20, 
the space g cannot be made narrow. Thus, the full liquid passing area 
becomes large with a combination of the fully required space g and the 
hole 72, so that it would be further difficult to obtain a large 
attenuation force. 
Therefore, an object of the present invention is to solve the disadvantages 
in such prior art and to provide a liquid sealed rubber mount capable of 
displaying an excellent vibration isolating effect in intermediate and 
high frequency ranges required for reducing vibration and noise, having, a 
vibration isolating effect with no resonation occurring with respect to 
even the impact vibration of a wide frequency band during bad road driving 
or the like, capable of obtaining a large attenuation force when the 
vibration amplitude is large, and capable of preventing the occurrence of 
lateral vibration. 
SUMMARY OF THE INVENTION 
A first aspect of the present invention is to provide a liquid sealed 
rubber mount of vibration isolating type which joins two separate members 
to each other through a cylindrical rubber mounting element and which 
contains a liquid sealing chamber housing, with an attenuation liquid 
therein, fixed to one member and a damper plate fixed to the other member, 
the liquid sealed rubber mount including an elastic member which can be 
deformed finely due to the resistance of the attenuation liquid when 
vertical vibration of the damper plate occurs, the elastic member being 
constituted by one of urethane foam having independent air bubbles 
therein, soft urethane-rubber, a rubber film with air sealed therein and a 
rubber film with a deformable, flexible material sealed therein. The 
elastic member can be fixed to upper and lower surfaces of the damper 
plate, positioned between two plates constituting the damper plate, or 
fixed to a surface of a rubber damper element provided under the surface 
of the damper plate. Alternatively, the elastic member may be fixed to 
surfaces formed by a combination of a rubber stopper element and a rubber 
damper element fixed to the upper and lower surfaces of the damper plate. 
In such a structure, when intermediate and high frequency vibration, the 
amplitude of which is small, is applied to the damper plate, the elastic 
member is deformed finely, so that the damper plate is independent of the 
attenuation liquid, and an excellent vibration isolating action can be 
obtained owing, to the rubber mounting element. When low frequency 
vibration, the amplitude of which is large, occurs, the damper plate and 
the elastic member are moved unitarily, so that the vibration is 
attenuated due to the attenuation liquid, with no resonation occurring. 
A second aspect of the present invention is to provide the liquid sealed 
rubber mount of vibration isolating type mentioned above in which the 
cylindrical rubber mounting element includes cylindrical plates positioned 
therein to form a laminate structure, said rubber mounting element having 
a hardness Hs in excess of 45.degree. but not more than 70.degree.. The 
attenuation liquid sealed in the liquid sealing chamber can have a 
viscosity in excess of 50,000 cst but not more than 150,000 cst. 
In such a structure, the laminate type rubber mounting element has a larger 
spring constant in the horizontal direction so that the occurrence of 
lateral vibration can be prevented. The spring constant of the rubber 
mounting element in the vertical direction is decreased by selecting its 
hardness, and the rubber mounting element displays an excellent vibration 
isolating effect in intermediate and high frequency ranges necessary to 
prevent vibration and noise. Furthermore, the attenuation liquid falls in 
the above range of viscosity, and this makes it possible to obtain a high 
attenuation action in a wide frequency range with no resonation occurring 
with respect to even the input vibration, such as the impact vibration of 
a wide frequency band.

BEST NODE FOR CARRYING OUT THE INVENTION 
A description will be made hereinbelow with respect to the preferred 
embodiments of a liquid sealed rubber mount according to the first aspect 
of the present invention, with reference to the accompanying drawings. 
FIG. 3 is a sectional side view of the first embodiment of a liquid sealed 
rubber mount, in which the rubber mount 40 comprises a case 11 fastened to 
a bracket 4 (see FIG. 2), a liquid sealing chamber housing 20 fixed to the 
lower end of the case 11, a rubber mounting element 17 fixed inwardly of 
the case 11, and a guide shaft 14 fixed inwardly of the rubber mounting 
element 17. A high attenuation liquid 21 is sealed in the liquid sealing 
chamber housing 20. The guide shaft 14 is provided with a bolt 16 at one 
end for fixing to a floor 6 of a cab 5 (see FIG. 2) by tightening the bolt 
16 with a nut 15, a damper plate 23 being fastened with a bolt 22 to the 
other end. An elastic member 24, such as urethane foam with independent 
air bubbles sealed therein, is fixed to the circumference of the damper 
plate 23 and is immersed in the high attenuation liquid 21. When vertical 
vibration of the damper plate 23 occurs within the liquid sealing chamber 
housing 20, the elastic member 24 is deformed into the elastic member 24a, 
shown by a dotted line, due to the resistance of the high attenuation 
liquid 21, with such hardness as deformed finely by the distance a. 
In such a structure, the liquid sealed rubber mount 40 operates as follows: 
the elastic member 24 is deformed finely by the distance a, as shown by 
the dotted line in FIG. 3, due to the resistance of the high attenuation 
liquid 21 when vertical vibration of the guide shaft 14 occurs due to an 
external force. Accordingly, when intermediate and high frequency 
vibration, the amplitude of which is not more than .+-.a, occurs, the 
damper plate 23 is independent of the high attenuation liquid 21 and an 
excellent vibration isolating action occurs, owing to the rubber mounting 
element 17. On the other hand, when low frequency vibration, the amplitude 
of which is in excess of .+-.a, occurs, the damper plate 23 and the 
elastic member 24 are moved unitarily such that the high attenuation 
liquid 21 generates a resistance force with respect to a stirring action 
of the damper plate 23, thus obtaining an attenuation force with no 
resonation occurring. 
A relationship between frequency and vibration transmission rate for each 
of the liquid sealed rubber mount 40 and the conventional rubber mounts is 
shown in FIG. 4. In the drawing, the solid line L1 represents the liquid 
sealed rubber mount 40 according to the present invention; the broken line 
L2 represents a common conventional rubber mount; and the one dot 
chain-line L3 represents the conventional viscous mount 70 (see FIG. 20). 
As shown in FIG. 4, with the liquid sealed rubber mount 40 according to 
the present invention, such a resonant phenomenon as appears in the 
conventional rubber mount does not occur with respect to low frequency 
vibration, while a large vibration isolating action, the vibration 
transmission rate of which is low, occurs with respect to intermediate and 
high frequency vibration, compared with that of the viscous mount, thus 
displaying an excellent vibration isolating action. 
Next, with the liquid sealed rubber mount 40 and the common conventional 
rubber mount, the results of measuring vertical acceleration of the cab 
floor with respect to an axis of time is shown in FIG. 5. The measurement 
of the vertical acceleration of the cab floor was carried out by setting 
the floor 6 of the cab 5 (see FIG. 2) on a vibration applying stand, not 
shown, through each of the liquid sealed rubber mounts processed as 
measured objects, and then actuating the vibration applying stand such 
that vibration occurs with predetermined vertical acceleration. As a 
result, the conventional rubber mount exhibited a maximum value of 
.alpha.1 on the vertical acceleration, whereas the liquid sealed rubber 
mount 40 of the present invention was .alpha.2 and a sharp fall in the 
maximum value appeared. It will be apparent from the results that the 
liquid sealed rubber mount 40 of the present invention can display an 
considerably excellent vibration isolating effect with respect to a sudden 
load change. 
Next, a description will be made hereinbelow with respect to a second 
embodiment according to the first aspect of the present invention with 
reference to the accompanying drawings. 
FIG. 6 shows the second embodiment of a liquid sealed rubber mount, the 
base structure of which is the same as that of the first embodiment but 
with the structure of the damper plate part being different. In FIG. 6, a 
liquid sealed rubber mount 41 is provided with a damper plate 28 at a low 
end of the guide shaft 14, the damper plate 28 being formed such that an 
elastic member 26, such as urethane foam, is positioned between two plates 
25 and the rubber stopper element 27 is fixed to the upper surface of one 
plate 25. The damper plate 28 is fastened to the guide shaft 14 by a bolt 
31 through a spring plate 30 and is held in the liquid sealing chamber in 
the housing 20. As an aside, like elements having shapes or functions 
identical to those of the first embodiment shown in FIG. 3 have identical 
reference numerals and the respective descriptions are omitted. 
In such a structure, when vertical vibration is applied to the guide shaft 
14, if intermediate and high frequency vibration the amplitude of which is 
small occurs, as similar to the first embodiment, the elastic member 26 is 
deformed finely due to the resistance of the high attenuation liquid 21 
and is not attenuated, and an excellent vibration isolating action occurs 
owing to the rubber mounting element 17. On the other hand, when low 
frequency vibration the amplitude of which is large occurs, the plates 25 
and the elastic member 26 are moved unitarily, an attenuation force of the 
high attenuation liquid 21 acts on the damper plate 28, resulting in the 
same effect as that of the first embodiment. 
Referring next to drawings attached, descriptions will be made with respect 
to third and fourth embodiments both of which can be also applied as 
preferred embodiments to the first aspect of the present invention. Both 
embodiments have the same basic structure as the first embodiment but 
differ in the structure of the damper plate part. In addition, like 
elements having shapes or functions identical to those of the first 
embodiment shown in FIG. 3 have identical reference numerals and the 
respective descriptions are omitted. 
FIG. 7 shows a liquid sealed rubber mount 42 according to the third 
embodiment, in which an elastic member 35, such as urethane foam, is fixed 
to a lower end of the rubber damper element 33 fixed to the damper plate 
23. Further, FIG. 8 shows a liquid sealed rubber mount 43 according to the 
fourth embodiment, in which the rubber stopper element 32 and the rubber 
damper element 33 are fixed to the upper and lower surfaces of the damper 
plate 23 and, in turn, elastic members 34 and 35 are held thereon. 
Although the rubber stopper element 32 and the rubber damper element 33 
are integrally formed into one rubber part, individual names are given, 
respectively, because they are slightly different in action from each 
other during the operating time. 
In such a structure, both of the third and fourth embodiments display a 
vibration isolating effect with respect to the vibration from the outside 
during the operating time, making use of such a characteristic as the 
elastic members 34 and 35 are deformed finely, resulting in the same 
effect as that of the first embodiment. 
As such above, while the first aspect of the present invention was 
described in detail with respect to the preferred embodiments, the elastic 
members 24, 26, 34 and 35 are not limited to urethane foam with 
independent air bubbles sealed therein. Any other materials or forming 
processes can be used to provide the elastic member as long as it can be 
deformed by a predetermined amount. For example, soft urethane-rubber type 
elastic members 36a and 36b can be cured and bonded to the surfaces of the 
rubber stopper element 32 and the rubber damper element 33 as shown in 
FIG. 9. A rubber film 38 with air 37 sealed therein can also be used to 
form another elastic member 39, as shown in FIG. 10, the air 37 being 
contained in a deformable soft material such as sponge rubber or a liquid. 
Further, elastomers and plastics other than rubber can be used as the 
material of the rubber stopper element (rubber damper element). 
Furthermore, the damper plate and the rubber stopper element can be 
integrated in one part. 
Next, a description will be made hereinbelow with respect to preferred 
embodiments of a liquid sealed rubber mount according to the second aspect 
of the present invention with reference to the accompanying drawings. 
FIG. 11 is a sectional side view showing a liquid sealed rubber mount 
according to a fifth embodiment, and FIG. 12 is a plan view of the liquid 
sealed rubber mount of FIG. 11. In the liquid sealed rubber mount 50, a 
liquid sealing chamber housing 53, having a rubber stopper element 52 
therein, is fixed to a lower end of a case 51. A damper plate 55, having a 
rubber stopper element 54 on part of its upper surface and a rubber damper 
element 54a on part of its lower surface, is held in the liquid sealing 
chamber housing 53 with a space c between the circumferences of the damper 
plate 55 and the liquid sealing chamber housing 53. An elastic member 56, 
such as urethane foam, is then fixed to the rubber damper element 54a. 
While the rubber stopper element 54 and rubber damper element 54a have 
been separately identified, they can be in the form of a single rubber 
element, as illustrated each of FIGS. 7-11. The guide shaft 14, having the 
bolt 16, is tightened with the nut 22 to the damper plate 55 and is joined 
to the case 51 by the rubber mounting element 58 having cylindrical 
laminate plates 57 therein, the rubber mounting element 58 having a 
hardness Hs of 45.degree. to 70.degree.. The hardness was obtained from 
the results of characteristic tests in which the liquid sealed rubber 
mount 50 is fabricated to measure values of loss factor and spring 
constant with respect to all kinds of load levels, the hardness having the 
effect of the conventional liquid sealed mount. Since rubber's hardness 
data generally vary to a degree (e.g., .+-.5.degree.), the determination 
of a precise hardness range is difficult, but it would be considered that 
the hardness Hs of 45.degree. to 60.degree. preferably exhibits a larger 
effect. On the other hand, the liquid sealing chamber housing 53 seals 
therein a high attenuation liquid 59, such as a silicon liquid having a 
viscosity in the range of 100,000 to 150,000 cst. The viscosity was also 
obtained from the results of characteristic tests in the same manner as 
the hardness determination. It is noted that the viscosity is preferably 
determined in a range of 50,000 to 150,000 cst for required performance 
with respect to a vibration isolating or controlling action. It is also 
considered that a viscosity exceeding 150,000 cst is preferably used to 
obtain an excellent loss factor with respect to low frequency vibration 
described later. 
In such a structure, while the relative displacement of the case 51 and the 
guide shaft 14 occurs due to the vibration from the road surface or the 
like when the vehicle starts driving, a vibration isolating action is 
displayed with respect to the intermediate and high frequency vibration, 
since the hardness of the rubber mounting element 58 is set low such that 
the spring constant becomes small in the vertical direction. Further, the 
rubber mounting element 58, having a cylindrically laminated structure 
with the laminate plates 57 as shown in FIG. 12, has a large spring 
constant in the horizontal direction so that the lateral vibration of the 
cab 5 (see FIG. 1) can be reduced. Furthermore, when the relative 
displacement of the case 51 and the guide shaft 14 occurs in the vertical 
direction, the damper plate 55 stirs the attenuation liquid 59 up and down 
within the liquid sealing chamber housing 53. The stirred attenuation 
liquid 59, having a high viscosity, is moved through a narrow space c, and 
a large attenuation force occurs. Accordingly, this liquid sealed rubber 
mount can display an attenuation force higher than that of the 
conventional viscous mount (see FIG. 20) with no resonation occurring with 
respect to even the input vibration such as the impact vibration of a wide 
frequency band. 
A description will be made next with respect to characteristics of the 
liquid sealed rubber mount 50 according to this embodiment, with reference 
to FIGS. 13 to 18. FIG. 13 shows a relationship between frequency and 
vertical vibration transmission rate, and FIG. 14 shows a relationship 
between frequency and lateral vibration transmission rate. Both indicate 
the liquid sealed rubber mount 50 of this embodiment with solid lines and 
the conventional viscous mount with broken lines. In both cases, the 
liquid sealed rubber mount of the present invention exhibits a 
substantially low value in vibration transmission rate across all ranges 
of frequency (covering low frequency through high frequency) compared with 
the conventional viscous mount, thereby displaying a vibration isolating 
effect as well as a vertical vibration reducing effect. FIG. 15 shows a 
vibration wave form for each frequency variation when resonation occurs; 
wherein the vertical axis expresses time and the horizontal axis is 
acceleration. This test was performed in the same manner as the 
measurement illustrated in FIG. 5. As a result, as shown in the drawing, 
the conventional viscous mount takes a maximum value of .alpha.3 on 
acceleration when resonation occurs, whereas the liquid sealed rubber 
mount 50 of the present invention takes a maximum value of .alpha.4, 
resulting in drastic reduction of vibration peaks when resonation occurs. 
It is apparent that the liquid sealed rubber mount 50 of the present 
invention has an excellent vibration isolating action. 
Next, a comparison will be made with respect to static spring 
characteristics; FIG. 16 shows static spring characteristics in the axial 
direction, and FIG. 17 shows the characteristics in the radial direction. 
The liquid sealed rubber mount 50 of the present invention, compared with 
the conventional viscous mount, has a flexible spring characteristic in 
the vertical direction, but static in the lateral direction so that the 
lateral vibration can be prevented. FIG. 18 shows attenuation performance 
of the liquid sealed rubber mount 50 of the present invention, 
illustrating a relationship between frequency and loss factor with respect 
to five levels, the input amplitude for each level being in a range of 
.+-.0.2 mm to .+-.5.0 mm. As compared with the conventional viscous mount, 
the present inventive mount has a small loss factor for performance 
required with respect to reduction of noise or vibration the amplitude of 
which is small, so that an excellent vibration isolating action can be 
displayed. On the other hand, it has a large loss factor required for 
comfortable driving with respect to low frequency vibration, the amplitude 
of which is large, so that an excellent vibration controlling action can 
be also displayed. 
INDUSTRIAL APPLICABILITY 
The present invention can be effectively applied to a liquid sealed rubber 
mount which is used as a device for reducing vibration or noise, for 
example, to mount a cab on a vehicle for business use, capable of 
displaying an excellent vibration isolating effect in intermediate and 
high frequency ranges, having a vibration isolating effect with no 
resonation occurring with respect to even the impact vibration of a wide 
frequency band, capable of obtaining a large attenuation force for large 
amplitude vibration, and capable of preventing the occurrence of lateral 
vibration.