JPH05149367A - Vibration isolating support structure - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a preventive support structure that achieves low dynamic springs in a wide frequency band. [Structure] Shock absorber rod 3 and vehicle body side member 2
8, a fluid insulator 15 in which a fluid is enclosed in an upper fluid chamber 10 formed in the elastic body 7 and a variable volume sub-fluid chamber 11 communicating with the upper fluid chamber 10 via an orifice 12; An insulator 25 with an intermediate mass, which sandwiches the ring mass 24 between the viscoelastic bodies 22 and 23, is interposed in series. In this case, insulator 2 with intermediate mass
The resonance frequency of 5 is set to be equal to or lower than the resonance frequency of the fluid insulator 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-vibration support structure for reducing vibration transmission, and particularly to an excellent anti-vibration property in a wide frequency band.

[0002]

2. Description of the Related Art A shock absorber, which is interposed between a coil spring and an unsprung portion of a vehicle, must be connected to a vehicle body in consideration of reduction of vibration transmission so that unsprung vibration is not transmitted to the spring. is there. For example, in what is called an input separation type strut, a spring support to which the upper end of a coil spring is fixed is fixed to an upper support via a spring insulator, and this upper support is rigidly coupled to a vehicle body via a bolt or the like.
The lower end of the coil spring is elastically or rigidly fixed to the outer cylinder of the shock absorber.

The shock absorber rod having a sliding portion penetrates through the central portion of the upper support and is elastically coupled to the upper support by sandwiching the upper support from above and below with a pair of strut insulators. The outer cylinder of the shock absorber is elastically or rigidly connected to a knuckle that supports a wheel. Therefore, in the input separation type strut, the coil spring is supported by the vehicle body in parallel through the spring insulator and the shock absorber is supported by the vehicle body in parallel through the strut insulator.

On the other hand, in a so-called input concentrated strut, a spring support fixed to an upper support via a spring insulator supports a coil spring and is rigidly connected to a shock absorber rod, and the shock absorber rod is It is coupled to the upper support via a strut insulator.

Therefore, in the input concentrated strut, both the coil spring and the shock absorber are supported by the vehicle body via the strut insulator.

[0006]

However, such a conventional support structure has the following problems. In other words, the input separation type strut uses a strut insulator having low rigidity in the vertical, front-rear, and left-right directions so that the input that has passed through the shock absorber does not propagate to the vehicle body with respect to low-frequency road surface input. The ride comfort is obtained, but on the other hand, in order to support the vehicle weight, the spring insulator is set to have a spring constant that is more than twice that of the strut insulator. When the up-and-down surge vibration is excited, the vibration is transmitted from the upper end of the coil spring to the vehicle body via the spring insulator having a large spring constant.

The surge vibration is also transmitted from the lower end of the coil spring to the outer cylinder of the shock absorber, but in the surge vibration frequency range, the shock absorber rod and the inner cylinder are affected by the flow resistance of the oil inside the shock absorber. Since it does not slide, surge vibration of the coil spring is directly transmitted to the shock absorber rod. At this time, since the strut insulator supporting the shock absorber has a low rigidity, the shock absorber vibrates in the vertical direction, and the vibration acts as a moment around the center of gravity of the knuckle portion, which causes rotational vibration of the knuckle portion. This vibration is transmitted to the vehicle body via suspension links that are elastically attached to the knuckle portion, and becomes a factor that worsens vehicle interior noise together with the vibration transmitted from the above coil spring to the vehicle body.

On the other hand, in the input concentration type strut,
The surge vibration excited in the coil spring is absorbed as an internal force acting on the shock absorber, so that the vehicle interior noise caused by this is reduced, but since the strut insulator supports the vehicle weight, the spring vibration of this spring It is necessary to increase the constant to some extent, and the spring constant becomes larger than the static spring constant in the high frequency region due to the frequency dependence of the rubber insulator, making it difficult to secure a good ride comfort. High frequency vibrations due to road surface input from the shock absorber and tire cavity resonance are easily transmitted to the vehicle body, and road noise is deteriorated.

The present invention has been made in view of the above-mentioned conventional problems, and can prevent deterioration of the vibration-proof characteristic at the time of high-frequency vibration input, particularly in the case of an input-concentrated strut. As described above, it is an object of the present invention to provide a vibration-proof support structure capable of achieving a low dynamic spring in a wide frequency range.

[0010]

In order to achieve the above object, a vibration isolating support structure according to a first aspect of the present invention is a main fluid chamber formed in an elastic body between a supporting side and a supported side. And a fluid insulator in which a fluid is enclosed in a variable volume sub-fluid chamber communicating with the main fluid chamber via an orifice,
An insulator with an intermediate mass having a mass sandwiched between a pair of viscoelastic bodies was interposed in series.

According to a second aspect of the invention, in the vibration isolating support structure according to the first aspect, the resonance frequency of the insulator with the intermediate mass is set to be equal to or lower than the resonance frequency of the fluid insulator.

[0012]

The fluid insulator has a low dynamic spring constant below the resonance frequency, but has a characteristic that the dynamic spring constant increases above the resonance frequency. On the other hand, the insulator with the intermediate mass has a characteristic that the dynamic spring constant increases at the resonance frequency of the vibration system including the mass and the viscoelastic body, but the spring constant decreases in a region higher than the resonance frequency.

Since the combined spring constant of the fluid insulator and the insulator with the intermediate mass connected in series does not exceed the individual spring constant,
It shows a low value in a wide frequency band. Particularly, when the resonance frequency of the insulator with an intermediate mass is equal to or lower than the resonance frequency of the fluid insulator, the frequency with which the insulator with an intermediate mass exhibits a high dynamic spring constant and the fluid insulator with a low dynamic frequency are low. Since they exist in the frequency region showing the spring constant, these combined spring constants will surely show a low value in a wide frequency band.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing the structure of one embodiment of the present invention. This embodiment shows a vibration-proof support structure according to the present invention.
Vehicle shock absorber (input-concentrated strut)
It is applied to the upper mounting structure of.

First, the structure will be described. That is, the coil spring 1 is interposed between the upper and lower springs so as to cover a shock absorber (not shown), the upper portion of which is fixed to the outer peripheral side of the spring support 2, and the lower portion of which is a shock (not shown). It is fixed to the outer cylinder of the absorber.

The threaded portion 3a formed on the upper end of the shock absorber rod 3 is attached to the spring support 2
Through the through hole 2a formed on the inner peripheral side of the bracket 6 and the through hole 6a formed on the inner peripheral side of the bracket 6 whose outer peripheral surface extends in a U-shaped cross section, and the nut 4 is attached to the threaded portion 3a. The spring support 2 and the bracket 6 are rigidly coupled to the upper end of the shock absorber rod 3 by fastening.

The inner peripheral surface of a ring-shaped elastic body 7 is vulcanized and adhered to the outer peripheral surface of the bracket 6 having a U-shaped cross section, and the outer peripheral surface of the elastic body 7 is a cylindrical body 8. Has been pressed into. The outer peripheral surface of the ring-shaped orifice structure 9 is fixed to the inner peripheral surface of the cylindrical body 8 so as to be covered by the elastic body 7. The orifice structure 9 has an elastic body 7 on the inner peripheral surface.
The upper surface and the lower surface are separated from the elastic body 7 by vulcanization adhesion to the upper surface of the orifice forming body 9 and the elastic body 7.
And an upper fluid chamber 10 as a main fluid chamber is defined between them and a lower fluid chamber 11 as a sub fluid chamber is defined between the lower surface of the orifice constituting body 9 and the elastic body 7.

In the elastic body 7, the part that defines the upper fluid chamber 10 and the part that defines the lower fluid chamber 11 are
For example, the thickness of each portion of the elastic body 7 is adjusted so that the latter has lower rigidity than the former. Then, in the orifice structure 9, the upper fluid chamber 10 and the lower fluid chamber 1
An orifice 12 that communicates with each other is formed, and these upper fluid chamber 10, lower fluid chamber 11 and orifice 12 are formed.
A fluid is enclosed in the inside.

Here, the bracket 6, the elastic body 7, the cylindrical body 8, the orifice forming body 9, the upper fluid chamber 10, the lower fluid chamber 11, the orifice 12 and the enclosed fluid form a fluid insulator 15. Furthermore, the cylindrical body 8
The outer peripheral surface of the mount support 20 is press-fitted into the lower part of the cylindrical mount support 20, and the upper part of the mount support 20 formed to have a smaller diameter than the lower part is press-fitted into the cylindrical body 21.

The cylindrical body 21 is fixed to an upper support 26 via an insulator 25 with an intermediate mass in which a cylindrical ring mass 24 is sandwiched between a pair of cylindrical viscoelastic bodies 22 and 23. The upper support 26 is provided with a body-side member 28 via bolts and nuts 27.
It is fixed to. Therefore, the vehicle body side member 28 as the supporting side and the shock absorber rod 3 as the supported side.
The fluid insulator 15 and the insulator with intermediate mass 25 are interposed in series between and.

Next, the operation of this embodiment will be described. When surge vibration is excited in the coil spring 1 by an input from the road surface, the surge vibration is transmitted from the lower end portion of the coil spring 1 to the outer cylinder of the shock absorber, and in the surge vibration frequency range, the shock absorber rod 3 and the shock absorber. The inner cylinder does not slide due to the flow resistance of the oil inside the shock absorber, and the surge vibration is directly transmitted to the shock absorber rod 3, but the upper end of the shock absorber rod 3 has a spring support 2
Since it is connected to the upper end of the coil spring 1 via, the surge vibration is absorbed as an internal force of the shock absorber.

As a result, no moment is input to the knuckle to which the lower end portion of the shock absorber is connected, so that the vehicle interior noise caused by the surge vibration of the coil spring 1 is reduced. Here, the fluid insulator 1
In No. 5, the lower fluid chamber 11 expands and contracts with vibration in the frequency region where the fluid can move between the upper fluid chamber 10 and the lower fluid chamber 11 via the orifice 12, but when the frequency increases, the lower fluid chamber 11 expands through the orifice 12. since movement of the fluid is impossible follow, the dynamic spring constant, as shown by a characteristic a of Fig. 2 shows a low value in the following areas resonant frequency theta _a fluid insulator 15, the resonance frequency theta _a In the above range, it increases as the frequency increases.

On the other hand, the dynamic spring constant of the insulator with the intermediate mass 25 is, as shown in the characteristic B of Figure 2, it becomes extremely large at the resonance frequency theta _B of the insulator with the intermediate mass 25, above its resonance frequency theta _B It shows a low value in the region.
Further, the synthetic spring constant K of the spring K _1, K ₂ which are coupled in series, since represented by _{K = K 1 K 2 / (} K 1 + K 2), as shown in FIG. 3, K ₁ and K ₂
Of the _two , it will never be greater than the lower value (K _{2 in} this case).

Therefore, the resonance frequency θ _B of the insulator 25 with an intermediate mass is set lower than the resonance frequency θ _A of the fluid insulator 15. Further, if the fluid insulator 15 and the insulator with intermediate mass 25 are tuned so that the fluid insulator 15 and the insulator with intermediate mass 25 have substantially the same dynamic spring constant at the resonance frequency θ _B of the insulator with intermediate mass 25, optimum characteristics can be obtained.

Further, the resonance frequency θ _B of the insulator 25 with the intermediate mass is determined by the insulator 25 with the intermediate mass.
Dynamic spring constant of the tire cavity resonance frequency θ _W (for example, 2
A value smaller than the tire cavity resonance frequency θ _W (for example, 200 Hz) so as to show a low value at about 50 Hz.
Set to about). As a result of such tuning, the resonance frequency θ _{B at} which the insulator 25 with an intermediate mass exhibits a high dynamic spring constant exists in the frequency region where the fluid insulator 15 exhibits a low dynamic spring constant, so that the fluid insulator is present. 15 and the combined dynamic spring constant of the intermediate mass-equipped insulator 25, as shown in the characteristic C of FIG. 2, the intermediate mass-equipped insulator 25 exhibits a low dynamic spring constant in a high frequency region including the tire cavity resonance frequency θ _W. The high dynamic spring constant of the insulator 25 with the intermediate mass at the resonance frequency θ _B is canceled by the fluid insulator 15 exhibiting the low dynamic spring constant, so that it shows a low value in a wide frequency band and in the entire road noise region. Noise reduction is achieved.

The composite dynamic spring constant has a low value even in the high frequency region, as is apparent from comparison with the characteristic D indicating the dynamic spring constant of solid rubber. Also, the vehicle interior noise can be reduced without increasing the vibration transmissibility from the lower spring side to the upper spring side. Furthermore, if the increase in the dynamic spring constant in the high frequency range is suppressed, it is not necessary to set the dynamic spring constant in the low frequency range to an extremely low value, and even if the spring constant required to support the vehicle weight is set, it will be high. The deterioration of riding comfort in the frequency domain can be avoided.

In this embodiment, the case where the anti-vibration support structure according to the present invention is applied to the upper mounting structure of the shock absorber has been described, but the application target of the present invention is not limited to this. Other supporting structures such as a supporting structure between the suspension subframe and the main frame may be used.

[0028]

As described above, according to the present invention,
Since the fluid insulator and the insulator with the intermediate mass are interposed in series between the supporting side and the supported side,
There is an effect that a low dynamic spring can be realized in a wide frequency band. Particularly, in the invention according to claim 2, since the frequency at which the insulator with an intermediate mass exhibits a high dynamic spring constant exists in the frequency region at which the fluid insulator exhibits a low dynamic spring constant, the intermediate mass at the resonance frequency is present. Even if the insulator with a high dynamic spring has a high dynamic spring, that is offset by the low dynamic spring constant of the fluid insulator, and the combined dynamic spring constant of the fluid insulator and the insulator with the intermediate mass shows a low value in a wide frequency band. can get.

[Brief description of drawings]

FIG. 1 is a sectional view showing the configuration of an embodiment of the present invention.

FIG. 2 is a graph showing a frequency characteristic of a dynamic spring constant.

FIG. 3 is a graph showing a combined spring constant when two springs are connected in series.

[Explanation of symbols]

 1 Coil Spring 3 Shock Absorber Rod (Supported Side) 6 Bracket 7 Elastic Body 8 Cylindrical Body 9 Orifice Body 10 Upper Fluid Chamber (Main Fluid Chamber) 11 Lower Fluid Chamber (Sub Fluid Chamber) 12 Orifice 15 Fluid Insulators 22, 23 Viscoelastic body 24 Ring mass 25 Insulator with intermediate mass 28 Body side member (support side)

Claims (2)

[Claims] 1. A fluid comprising a main fluid chamber formed in an elastic body and a sub-fluid chamber of variable volume communicating with the main fluid chamber through an orifice between a supporting side and a supported side. An anti-vibration support structure characterized in that an insulator and an insulator with an intermediate mass in which a mass is sandwiched by a pair of viscoelastic bodies are interposed in series. 2. The anti-vibration support structure according to claim 1, wherein the resonance frequency of the insulator with the intermediate mass is set to be equal to or lower than the resonance frequency of the fluid insulator.