JPH04347321A - Vibro-damper - Google Patents

Abstract

PURPOSE:To provide such a vibro-damper as capable of securing an optimum vibro-isolating characteristic over an extensive frequency band without entailing any damage to the strength and durable performance of a vibrator or the like. CONSTITUTION:An exhaust pipe support unit 1 is provided with an almost ringlike support member 6 which is composed of a first mounting part 7, a second mounting part 8 and a symmetrical pair of elastic arm parts 11, 12 connecting both ends of these mounting parts 7, 8. An exhaust pipe side bracket 5 is inserted into a first mounting hole 9 of the first mounting part 7, and a body side bracket 3 is inserted into a second mounting hole 10 of the second mounting part 8 into engagement as well. The elastic arm part 11 at the left constitutes a spring system K. In addition, a mass body 13 is embedded in an intermediate position in the upper direction of the elastic arm part 12 at the right, and these elements constitute a series of a spring-mass-spring system M.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration damping device, and more particularly, to a vibration damping device suitable as an exhaust pipe support device for suspending an automobile exhaust pipe or the like to cut off or damp vibration transmission to the vehicle body. It is.

0002

2. Description of the Related Art Conventionally, various structures have been employed in which a vibrating body is suspended by a rubber support device to isolate or attenuate the vibrations of the vibrating body. For example, in automobiles, an exhaust pipe support device is used when suspending an exhaust pipe through which exhaust gas from an engine passes from a vehicle body.

As shown in FIG. 6(a), this exhaust pipe support device 21 includes a ring-shaped support member 22 made of rubber elastic material. Attachment holes 23 and 24 are formed through the support member 22 at vertically opposing positions, respectively, and a vehicle body side bracket 25 and an exhaust pipe side bracket 26 are fitted into the attachment holes 23 and 24, respectively. Further, the portions of the support member 22 that face each other on the left and right sides are elastic arm portions 27 and 28.
8 constitutes a spring system.

FIG. 6(b) is a model of FIG. 6(a). In the figure, k is the spring constant of the elastic arm parts 27 and 28, F is the force transmitted to the vehicle body 31 side via the exhaust pipe support device 21 (reference transmission force), and x is the displacement when the exhaust pipe 32 vibrates in the vertical direction. There is a relationship F=kx between them. Here, since the exhaust pipe 32 vibrates with a constant displacement (x is constant), in order to reduce the reference transmission force F, the spring constant k
needs to be made smaller. However, if you do it like this,
The rubber elastic body constituting the exhaust pipe support device 21 becomes soft, and the durability of both the exhaust pipe support device 21 and the exhaust pipe 32 deteriorates.

[0005] Therefore, as shown in FIG. 7(a), an exhaust pipe support device 21 has been proposed in which mass bodies 29 and 30 are attached to approximately mid-positions in the vertical direction of each elastic arm portion 27 and 28 (in practice). Publication No. 64-11318). When these mass bodies 29 and 30 have the same mass, that is, are symmetrical, a system with one degree of freedom is constructed. Figure 7(b)
is a modeled version of FIG. 7(a). In the figure, Fb is the force transmitted to the vehicle body 31 side via the exhaust pipe support device 21 (
transmission force), m is the mass of the mass bodies 29, 30, k, x
is the same as that shown in FIG. 6(b) described above. The vibration damping characteristic of this exhaust pipe support device 21 is shown by a characteristic line L12 in FIG. The vertical axis in FIG. 8 is the ratio (Fb/F) of the transmission force Fb to the reference transmission force F, expressed in decibels. Therefore, if the characteristics of the exhaust pipe support device 21 in FIG. 6(a) are shown by the characteristic line L11 in FIG.
The ratio of transmitted forces is "0" regardless of frequency. Further, from FIG. 8, a portion of the characteristic line L12 smaller than the characteristic line L11, that is, a diagonally shaded portion in FIG. 8 is an area where the transmitted force can be reduced. Note that fb is the lowest frequency at which the transmitted force Fb can be reduced.

[0006] Also, in the prior art publication, the mass body 29,
A technique in which the masses m of 30 are made different from each other (left-right asymmetric) is also disclosed. In this case, the exhaust pipe support device 21
Letting the force transmitted to the vehicle body 31 side via Fc be the transmission force Fc,
The ratio of the transmission force Fc to the reference transmission force F (Fc /
The relationship between F) and frequency is represented by a characteristic line L13 in FIG. The characteristic in this case has two peaks, and each peak value is lower than the peak value in the symmetric case.

[0007]

[Problem to be Solved by the Invention] However, when the masses m of the mass bodies 29 and 30 are the same (symmetrical) on the left and right sides, as is clear from FIG. 8, the transmitted force Fb is reduced in the high frequency range. However, such an effect is not seen in the low frequency range. Therefore, in order to reduce the transmitted force from the low frequency range, it is necessary to increase the mass m of the mass bodies 29 and 30 or to decrease the spring constant k of the elastic arm sections 27 and 28. That is, as mentioned above, the same mass m
Let f0b be the resonance frequency in the structure in which the mass bodies 29 and 30 are attached to the elastic arms 27 and 28, f0b is as follows: f0b=(1/2π)・(k/m)1/2
...It is expressed as (1). Also, the transmission force Fb is fb = 21/2・f0
It is reduced in the frequency range equal to or higher than the frequency fb expressed by b. Therefore, in order to lower this frequency fb, the above (1
), it is necessary to increase the mass m and decrease the spring constant k. However, such measures conflict with the strength and durability of the exhaust pipe system, and therefore have practical limitations.

Furthermore, even if the masses m of the mass bodies 29 and 30 are different on the left and right sides, since the vibration system has a spring-mass-spring configuration, the resonant frequency of the higher peak is as shown in FIG.
As shown by the arrow in , the transmission force Fc cannot be reduced in the low frequency range by simply moving to the high frequency side. Therefore, in order to reduce the vibration in this case as well, it is necessary to increase the mass m of the mass bodies 29 and 30 or to decrease the spring constant k, as in the above case.

The present invention was made in view of the above-mentioned circumstances, and its purpose is to obtain optimal vibration isolation characteristics over a wide frequency range without impairing the strength and durability of non-vibrating bodies such as exhaust pipes. The object of the present invention is to provide a vibration damping device capable of

0010

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a first mounting part to which a vibrating body is mounted, and a second mounting part to which a non-vibrating body is mounted spaced apart from the first mounting part. and a pair of elastic arm sections that connect the first and second attachment sections while being spaced apart from each other, one of the elastic arm sections is a spring system K, and the other is A mass body is provided in the middle part of the elastic arm part to form a spring-mass-spring system M.

[0011]

[Operation] By adopting the above configuration, when vibrations from the vibrating body are transmitted to the vibration damping device, one elastic arm portion acts as a spring system K, and the other elastic arm portion having a mass body acts as a spring-mass system. - acts as a spring system M; and,
Both of these systems damp vibrations from the vibrating body and suppress transmission of the vibrations to non-vibrating bodies in the following manner.

That is, the force transmitted from the vibrating body to the non-vibrating body via the spring system K is the transmission force FK, and the force transmitted from the vibrating body to the spring -
The force transmitted to the non-vibrating body via the mass-spring system M is the transmission force FM
In this case, both transmission forces FK and FM have different characteristics from each other. If the transmission force transmitted from the vibrating body to the non-vibrating body via the vibration damping device is Fa, both transmission forces F
The combined value of K and FM becomes this transmission force Fa.

Here, if the transmission force to the non-vibrating body when no mass body is provided in any of the elastic arm parts is the reference transmission force F, then the transmission force FK from the spring system K with respect to this standard transmission force F is The relationship between the ratio (FK/F) and frequency is expressed by the characteristic line LK in FIG. In addition, the reference transmission force F
The relationship between the frequency and the ratio of the transmission force FM from the spring-mass-spring system M to the frequency is shown by the characteristic line LM in Fig. 3.
It is expressed as The resonant frequency f0a in this characteristic line LM is lower than the resonant frequency when both elastic arm sections are provided with mass bodies. Furthermore, the relationship between the phase and frequency of the vibration of the spring system K is represented by the characteristic line NK in Figure 3, and the relationship between the phase and frequency of the vibration of the spring-mass-spring system M is represented by the characteristic line NM in Figure 3.
It is expressed as

[0014] Then, the characteristic lines NK and NM of both phases are
By combining both the characteristic lines Lk and LM in consideration of the above, a characteristic line L1 is obtained which shows the relationship between the frequency and the ratio of the transmission force Fa from the entire vibration damping device to the reference transmission force F (Fa/F). . In other words, the spring-mass-spring system M
In the frequency range lower than the resonance frequency f0a, the phase of the spring system K and the phase of the spring-mass-spring system M are the same, so the characteristic line L1 is the characteristic line Lk plus the characteristic line LM. Since the phase is reversed around the resonance frequency f0a, the characteristic line L1 changes from the characteristic line Lk to the characteristic line LM.
The characteristics are obtained by subtracting . As a result, the characteristic line L1 has a characteristic that sharply decreases around the resonance frequency f0a.

In this way, the vibration phases of the spring system K and the spring-mass-spring system M are reversed, and the transmitted force FK and the transmitted force FM are
By canceling each other out, even in the low frequency range, the transmission force Fa from the entire vibration damping device against the reference transmission force F
The ratio (Fa/F) decreases. As a result, the lowest frequency at which vibration can be damped becomes lower than when mass bodies are provided on both elastic arms.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the vibration damping device of the present invention is applied to an automobile exhaust pipe support device will be described below with reference to FIGS. 1 to 5. As shown in FIG. 2, this exhaust pipe support device 1 includes a vehicle body side bracket 3 that hangs down from the lower surface of a vehicle body 2 as a non-vibrating body, and an exhaust pipe side bracket 5 that projects upward from an exhaust pipe 4 that serves as a vibrating body. Connect the exhaust pipe 4
is suspended from the vehicle body 2.

As shown in FIG. 1(a), the exhaust pipe support device 1 includes a substantially ring-shaped support member 6 made of a rubber elastic body with a predetermined thickness, and the lower part of the support member 6 is connected to a first attachment point. 7, and the upper part is also a second mounting part 8.
It consists of A first mounting hole 9 is transparently provided in the first mounting portion 7, and the exhaust pipe side bracket 5 is inserted through the first mounting hole 9.
is inserted and locked. Further, the second mounting portion 8 has a second
A mounting hole 10 is provided therethrough, into which the vehicle body side bracket 3 is inserted and locked.

The left and right sides of the support member 6 are elastic arm portions 11 and 12 that connect the first and second mounting portions 7 and 8, of which the left elastic arm portion 11 is It constitutes a spring system K. Further, a mass body 13 made of a metal piece or the like is buried in an intermediate position in the vertical direction of the right elastic arm part 12, and these bodies are supported by springs.
It constitutes a mass-spring system M.

FIG. 1(b) is a model of FIG. 1(a). In the figure, k is the spring constant of the elastic arm parts 11 and 12, m is the mass of the mass body 13, and FK is the spring constant from the spring system K to the vehicle body 2.
The force transmitted to, FM is the spring-mass-spring system M to the vehicle body 2
The transmission force, Fa, is from the exhaust pipe support device 1 to the vehicle body 2.
x is the amount of displacement when the exhaust pipe 4 vibrates in the vertical direction. Note that in this embodiment, the static spring constant is the same as that of the prior art.

In this embodiment configured as described above, when the vibration of the exhaust pipe 4 is transmitted to the exhaust pipe support device 1,
The left elastic arm 11 acts as a spring system K, and the right elastic arm 12 and mass body 13 act as a spring system.
It acts as a mass-spring system M. Then, the left and right elastic arm sections 11 and 12 expand and contract, respectively, and the mass body 13 is displaced in the vertical direction. These vibrations and displacements attenuate the vibrations of the exhaust pipe 4 in the following manner, making it difficult for the same vibrations to be transmitted to the vehicle body 2.

That is, in the exhaust pipe support device 1, the transmission force FK from the spring system K and the spring-mass-
The transmission force FM from the spring system M has different characteristics from each other. The combined value of both transmission forces FK and FM becomes the transmission force Fa transmitted from the exhaust pipe 4 to the vehicle body 2 via the exhaust pipe support device 1. Here, if the transmission force in the case where no mass body is provided in any of the elastic arm parts (see FIG. 6) is the reference transmission force F, then the ratio of the transmission force FK from the spring system K to this reference transmission force F is ( The relationship between FK /F) and frequency is expressed by the characteristic line LK in FIG. The reason why the characteristic line Lk is 6 dB lower than the characteristic line L11 is because the transmission force FK from the spring system K is half of the reference transmission force F.

Further, the relationship between the frequency and the ratio (FM/F) of the transmission force FM from the spring-mass-spring system M to the reference transmission force F is expressed by the characteristic line LM in FIG. The resonant frequency f0a in this characteristic line LM is the characteristic line L
12 (see FIG. 8). This is due to the following reason. In other words, if the total mass of the mass bodies 29 and 30 in the exhaust pipe support device 21 in FIG. 7(b) is the same as the mass of the mass body 13 in the exhaust pipe support device 1 in FIG. The mass of the mass body 13 of the spring-mass-spring system M in 1(b) is shown in FIG.
The mass is twice the mass of the mass body 30 on the right side in b). Therefore, if the mass m in equation (1) for calculating the resonance frequency f0b mentioned above is doubled, the spring-mass-spring system M
The resonant frequency f0a is lower than the resonant frequency f0b.

Furthermore, the relationship between the phase and frequency of the vibration of the spring system K is represented by the characteristic line NK in FIG. 3, and the relationship between the phase and frequency of the vibration of the spring-mass-spring system M is represented by the characteristic line NK in FIG. N
It is represented by M. The phase of the spring system K is constant regardless of frequency. If this phase is used as a reference (0°), the phase of the spring-mass-spring system M is the same as the phase of the spring system K (0°) in a frequency range lower than the resonance frequency f0a. Also, the phase of the spring-mass-spring system M is at the resonance frequency f0
In the frequency range around a, it is inverted from 0° to 180° in a lower frequency range.

[0024] Then, the characteristic line NK of both vibration phases,
When both the characteristic lines Lk and LM are combined in consideration of NM, a characteristic line L1 is obtained which shows the relationship between the ratio of the transmission force Fa from the exhaust pipe support device 1 to the reference transmission force F (Fa/F) and the frequency. . In other words, in the frequency range lower than the resonance frequency f0a, both phases are the same, so the characteristic line L
1 is the value obtained by adding the characteristic line Lk to the characteristic line LM, and since the phase is reversed around the resonance frequency f0a, the characteristic line L
1 is the value obtained by subtracting the characteristic line LM from the characteristic line Lk. As a result, the characteristic line L1 is 0 dB in the low frequency range, increases as it approaches the resonant frequency f0a, and sharply decreases around the resonant frequency f0a. Note that in a frequency range higher than the resonant frequency f0a by a predetermined value or more, the level difference between both characteristic lines Lk and LM becomes large (
(the level of the characteristic line LM becomes smaller), the characteristic line L
1 approaches the characteristic line Lk because the influence of phase inversion disappears.

As described above, in this embodiment, the left elastic arm 11 of the left and right elastic arm sections 11 and 12 constitutes the spring system K, and the right elastic arm 12
Since the mass body 13 is provided in the spring-mass-spring system M to configure the spring-mass-spring system M, the vibration phases of the spring system K and the spring-mass-spring system M are reversed around the resonance frequency f0a, and the transmitted force FK and the transmitted force FM are By canceling each other out, the transmission force ratio (Fa /F
) also decreases in the low frequency range. As a result, as shown in FIG.
The frequency is lower than the frequency fb when 0 is provided (see FIG. 7). As a result, without increasing the mass m of the mass body 13 or decreasing the spring constant k of the elastic arm portions 11 and 12,
It becomes possible to reduce the transmission force from the low frequency range. Therefore, in this embodiment, optimum vibration damping characteristics can be obtained over a wide frequency range without impairing the strength or durability of the exhaust pipe 4.

FIG. 5 is a graph for confirming the effect of the exhaust pipe support device 1 of this embodiment, and the vertical axis indicates the lowest frequency that can be attenuated. A comparative example is a case where mass bodies are provided on both the left and right elastic arm sections. As is clear from this figure, in this example, vibrations can be damped from the low frequency range with a small mass m. It should be noted that the present invention is not limited to the configuration of the embodiments described above, and may be modified as desired without departing from the spirit of the invention, for example, as described below. (1) The shape, material, etc. of the mass body 13 in the above embodiment may be changed as appropriate. (2) The attachment position of the mass body 13 to the elastic arm part 12 may be slightly shifted from the intermediate position of the elastic arm part 12. (3) In addition to the exhaust pipe support device, the present invention can be applied to various vibration damping devices for supporting a vibrating body on a non-vibrating body.

[0027]

Effects of the Invention As described in detail above, the vibration damping device of the present invention has one elastic arm part of a spring system, and a mass body provided in the middle part of the other elastic arm part, so that the vibration damping device of the present invention has a spring-mass-spring structure. system, it has the excellent effect of being able to obtain optimal vibration damping characteristics over a wide frequency range without impairing the strength or durability of the vibrating body or the like.

[Brief explanation of drawings]

FIG. 1 shows an example in which the vibration damping device of the present invention is embodied in an automobile exhaust pipe support device, in which (a) is a partially cutaway front view of the exhaust pipe support device, and (b) is a partially cutaway front view of the exhaust pipe support device. It is a diagram modeling an exhaust pipe support device.

FIG. 2 is a side view of an exhaust pipe supported on a vehicle body by an exhaust pipe support device according to an embodiment.

FIG. 3 is a graph showing the relationship between frequency and transmission force ratio and the relationship between frequency and phase when using the exhaust pipe support device of one embodiment.

FIG. 4 is a graph showing the relationship between frequency and transmission force ratio when using the exhaust pipe support device of one embodiment.

FIG. 5 is a graph showing the relationship between the mass of a mass body and frequency.

FIG. 6(a) is a front view of a conventional exhaust pipe support device;
(b) is a diagram similarly modeling the exhaust pipe support device.

FIG. 7(a) is a partially cutaway front view of a conventional exhaust pipe support device, and FIG. 7(b) is a modeled view of the exhaust pipe support device.

FIG. 8 is a graph showing the relationship between frequency and transmission force ratio when a conventional exhaust pipe support device is used.

[Explanation of symbols]

2... Vehicle body as a non-vibrating body, 4... Exhaust pipe as a vibrating body, 7... First mounting part, 8... Second mounting part, 11, 12...
Elastic arm portion, 13...mass body, K...spring system, M...spring-
Mass-spring system

Claims (1)

[Claims] 1. A first mounting part to which a vibrating body is mounted, a second mounting part to which a non-vibrating body is mounted while being spaced from the first mounting part, and the first and second mounting parts. It is formed from a pair of elastic arms that are connected to each other while being spaced apart from each other, one of the elastic arms is a spring system, and a mass body is provided in the middle part of the other elastic arm to create a spring. A vibration damping device characterized by having a spring system.