JPH022498B2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a liquid-filled anti-vibration bushing that utilizes the elasticity of a rubber elastic body and the viscous resistance of a fluid. This invention relates to a vibration-proof bushing that provides soft spring characteristics in a high-frequency vibration range.

Conventional technology Traditionally, automobile suspension bushes,
The use of fluid-filled anti-vibration bushings as described above is progressing in differential gear mounts, engine mounts, tension rod bushes, and the like. The following is known as one type of such fluid-filled bushings.

It includes an inner cylindrical metal fitting and an outer cylindrical metal fitting that are arranged concentrically at a predetermined distance from each other, and a cylindrical rubber elastic body interposed between the inner cylindrical metal fitting and the outer cylindrical metal fitting. Further, a plurality of recesses are provided so as to open on the outer circumferential surface of the rubber elastic body, and a plurality of fluid chambers are formed by covering these recesses with an outer cylindrical metal fitting. A predetermined incompressible fluid is sealed in each of these fluid chambers. Further, the fluid chambers are interconnected by orifices to permit fluid communication between the fluid chambers.

Such an anti-vibration bushing is used by being attached to the inside of the inner cylindrical metal fitting and the outside of the outer cylindrical metal fitting, between objects to be vibration-isolated such as the suspension of an automobile. Therefore, in order to attenuate large vibrations at low frequencies, the size and length of the orifice are determined so that the attenuation peak occurs in the region of, for example, 5 to 20 Hz. For excitation input in the vibration region, an effective damping effect is produced by the viscous resistance generated when the fluid flows through the orifice.

Problems to be Solved by the Invention However, in such a vibration-proof bushing, as mentioned above, the orifice must be set so that the attenuation peak occurs in the low frequency range where attenuation is most needed; In response to a vibration input that exceeds 200 Hz, for example, the inertia of the fluid prevents the fluid from flowing through the orifice. As a result, the fluid confined in each fluid chamber becomes, so to speak, a rigid body, and the dynamic rigidity of the vibration-proof bushing increases. In other words, the dynamic spring constant increases and the transmission force increases, which reduces the vibration isolation characteristics in the high frequency range where fluid no longer passes through the orifice. There was a problem that vibration and noise could not be effectively prevented.

The purpose of this invention is to lower the dynamic stiffness of the bush and provide soft spring characteristics in such a high frequency vibration region where fluid does not pass through the orifice.

Means for Solving the Problems First, as a premise, the type of bush to which this invention is applied is, as described above, composed of an inner cylindrical metal fitting, an outer cylindrical metal fitting, a rubber elastic body between them, and the rubber elastic body. a plurality of fluid chambers formed by covering a plurality of recesses opening on the outer peripheral surface of the body with an outer cylinder fitting;
The structure includes an incompressible fluid sealed in each of the fluid chambers, and an orifice that allows the fluid chambers to communicate with each other.

And in a bush with such a structure,
The means taken to solve the above problem are as follows: (a) At a position corresponding to at least a part of the opening of the recess provided in the rubber elastic body, the rubber elastic membrane facing the fluid chamber is attached to the outer cylinder metal fitting. (b) Further, a cavity is formed in the outer cylindrical fitting opposite to the fluid chamber with respect to the rubber elastic body.

Here, the rubber elastic membrane may be directly fixed to the inner circumferential surface of the outer cylinder metal fitting, or may be indirectly fixed in position via another member. Further, in a preferred embodiment, the void space in the outer cylinder fitting is obtained by, for example, forming a hole in the outer cylinder fitting with a size that allows appropriate elastic deformation of the rubber elastic membrane. However,
It is also possible to interpose another member between the rubber elastic membrane and the outer cylindrical metal fitting to form a space therein.

Effect The vibration-proof bushing obtained by adopting such a method is similar to the conventional one in that the fluid does not pass through the orifice in the high-frequency vibration region, but in this state, it can be installed so as to face the fluid chamber. The rubber elastic membrane is elastically deformed between the cavity and the fluid chamber in response to fluctuations in the pressure of the fluid chamber based on the vibration input. That is, when the pressure in the fluid chamber increases, the rubber elastic membrane bulges and deforms toward the cavity, and when the pressure in the fluid chamber decreases,
It elastically deforms so as to enter the fluid chamber side, thereby allowing the volume of the fluid chamber to fluctuate, and playing the role of ensuring that the elastic deformation of the rubber elastic body is not hindered by the presence of fluid. .

Effects of the Invention Therefore, even if the fluid becomes confined within each fluid chamber in a high frequency range, the rubber elastic membrane allows the volume of the fluid chamber to fluctuate, so the fluid no longer exhibits rigid behavior. Therefore, a low dynamic spring constant can be obtained. In other words, soft spring characteristics are obtained against high-frequency excitation input, and as a result, the isolation performance against high-frequency vibrations is improved, and vibration and noise characteristics can be improved, for example by reducing muffled noise in the cabin of a car. This makes it possible to improve effectively.

EXAMPLES Hereinafter, in order to clarify the present invention more specifically, examples thereof will be described in detail based on the drawings.

First, FIGS. 1 and 2 show that a vibration-proof bushing 10, which is a specific example of the present invention, is attached to one vibration-proof object 1.
2 is shown fitted into the cylindrical mounting portion 14 of No. 2. This anti-vibration bushing 10 includes an inner cylindrical metal fitting 16 and an outer cylindrical metal fitting 18, both of which are cylindrical in shape, which are arranged concentrically at a predetermined distance apart. A cylindrical rubber elastic body 20 is interposed between the inner cylindrical metal fitting 16 and the outer cylindrical metal fitting 18. As is clear from FIG. 2, this rubber elastic body 20 is vulcanized and bonded at its inner circumferential surface to the inner cylindrical metal fitting 16 and at its outer circumferential surface to the cylindrical outer circumferential sleeve 22. It is fixed inside the outer cylindrical metal fitting 18 via.

As is clear from FIG. 1, the rubber elastic body 20 has two symmetrical recesses 2 with the inner cylinder fitting 16 in between.
4 extends in the circumferential direction, and the rubber elastic body 20
They are each formed to open on the outer circumferential surface of each. Furthermore, windows 26 corresponding to the openings of these recesses 24 are formed in the outer sleeve 22 . The openings of these recesses 24 are covered by the outer cylindrical fitting 18, thereby forming two fluid chambers 28 and 30 that face each other in the diametrical direction of the inner cylindrical fitting 16. In these fluid chambers 28 and 30, predetermined incompressible fluids such as alkylene glycol, polyalkylene glycol, silicone oil, low molecular weight polymers, water, etc., or a suitable combination thereof, are respectively sealed. has been done.

These fluid chambers 28 and 30 are communicated with each other by an orifice 32, and fluid is allowed to flow between both fluid chambers 28 and 30 through this orifice 32. In order to obtain such an orifice 32, an orifice forming block 34 is press-fitted into the middle part of the inner cylindrical fitting 16, and an annular groove with a narrow cross-sectional area is formed on the boundary surface between two of the orifice forming blocks 34 provided in the block 34. The orifice 3 is communicated with each of the fluid chambers 28 and 30 through the communication hole 36.
2 is formed.

The orifice forming block 34 is shaped to protrude toward each of the fluid chambers 28 and 30, and works together with the outer cylindrical metal fitting 16 to prevent excessive deformation of the rubber elastic body 20, that is, the inner cylindrical metal fitting 16. It also serves as a stopper to prevent excessive displacement between the outer cylindrical fitting 18 and the outer cylindrical fitting 18.

Now, a thin rubber layer 38 is vulcanized and adhered to the inner circumferential surface of the outer cylindrical fitting 18 so as to form a cylindrical shape over the entire surface thereof. Two holes 40 are formed in the outer cylindrical fitting 18 at both end portions in the circumferential direction of the fluid chamber 28 and penetrate in the thickness direction. Corresponding parts are rubber elastic membranes 42, 42. these holes 4
0 is formed in a rectangular shape and has a somewhat large opening area, and is an opening that allows appropriate elastic deformation in the thickness direction with respect to the rubber elastic membranes 42, 42, as is clear from FIG. It fulfills its role.

That is, the rubber elastic membranes 42, 42 are provided at positions corresponding to both ends in the circumferential direction of the opening of the recess 24 forming the main body of the fluid chamber 28,
They are integrally held by the outer cylindrical fitting 18 by vulcanization adhesion, and, as is clear from FIG. -ing On the opposite side of the rubber elastic membrane 42 from the fluid chamber 28, holes 40 functioning as voids are provided in the outer cylinder fitting 18, respectively.

As a result, each rubber elastic membrane 42 can be elastically deformed to expand toward the hole 40 side or to be depressed toward the fluid chamber 28 side in response to fluctuations in the pressure in the fluid chamber 28. The elastic deformation toward the hole 40 allows the volume of the fluid chamber 28 to increase, and the elastic deformation toward the fluid chamber 28 allows the volume to decrease.

Similarly, there is a hole 4 on the other fluid chamber 30 side.
4 and 44 are formed on the outer cylindrical fitting 18, and the corresponding portions are made of rubber elastic membranes 46 and 46, which can be elastically deformed in the thickness direction in response to fluctuations in pressure in the fluid chamber 30. The rubber elastic membrane 46 is adapted to allow variations in the volume of the fluid chamber 30.

Note that the elastic membranes 42 and 46 are connected to the fluid chamber 28,
The orifice forming block 34 is provided at positions corresponding to both ends of the outer cylinder 18 in the circumferential direction when the orifice forming block 34 acts as a stopper with the outer cylinder fitting 18.
This is to prevent contact between them. Furthermore, the portions corresponding to the holes 40 and 44 are made of a rubber layer 38 that functions as a rubber elastic membrane.
In other parts, the outer sleeve 2
2 and the outer cylindrical metal fitting 18, and also serves as a sealing rubber layer that seals the openings of the respective recesses 24, 24 formed in the rubber elastic body 20. Furthermore, the portions of the rubber layer 38 corresponding to both protruding portions of the orifice forming block 34 also act as a cushioning material that cushions the impact upon contact when the above-mentioned stopper action is performed.

Further, as described above, the outer cylindrical metal fitting 18 of the bush 10 is fitted inside the cylindrical mounting portion 14 of the vibration-isolating object 12, but as shown in FIG. Its cylindrical mounting portion 14
An annular circumferential groove 48 is formed along the circumferential direction on the inner circumferential surface of the
As is clear from FIG. 3, the holes 40 and 44 formed in the outer cylindrical fitting 18 are positioned along this circumferential groove 48. As a result, as shown in FIG. 1, the holes 40, 40 on the fluid chamber 28 side and the holes 44 on the fluid chamber 30 side,
44 can be communicated with each other by the circumferential groove 48.

By the way, the anti-vibration bushing 10 as described above is
For example, it can be manufactured as follows.

First, as shown in FIGS. 5 and 6, holes 40 and 44 as described above are formed in the outer cylindrical fitting 18 in advance, and the outer cylindrical fitting 18 with the holes machined is placed in a predetermined mold. A thin rubber layer 38 is vulcanized and molded on the inner circumferential surface thereof, and is vulcanized and bonded to the inner circumferential surface of the outer cylindrical metal fitting 18. Note that each of the holes 40 and 44 is closed in advance with an appropriate closing member to prevent the rubber material from entering them.

On the other hand, in order to manufacture the bush main body as shown in FIG. 7, the inner cylindrical metal fitting 16 into which the orifice forming block 34 is press-fitted and the outer sleeve 22 having the window 26 are placed in a predetermined mold. They are set concentrically, a rubber material is injected between them, and the rubber elastic body 20 is vulcanized and molded.
6 and the outer peripheral side sleeve 22, respectively, to obtain a bush main body.

Then, in the fluid tank containing the above-mentioned fluid, a sixth
As shown in the figure, by fitting the outer cylinder fitting 18 to which the rubber layer 38 is vulcanized and bonded, each fluid chamber 2
8 and 30, sealing fluid inside them, and then performing a narrowing operation on the outer cylindrical fitting 18 in the direction of diameter reduction, the prevention as shown in FIGS. 1 and 2 can be achieved. A shaker bush 10 is obtained.

The anti-vibration bushing 10 is fitted into the mounting portion 14 of one of the objects 12 to be vibration-proofed in the outer cylindrical metal fitting 18, while being fitted into the inner cylindrical metal fitting 16.
Although not shown, the shaft portion of the other vibration-proofing object is inserted, and the two liquid chambers 28 and 30 are used in a state where the main load is applied in opposing directions.

Therefore, when a low-frequency, large-amplitude vibration input acts in that direction, the volume of one of the liquid chambers 28 and 30 decreases, and the volume of the other increases, based on the elastic deformation of the rubber elastic body 20. As a result, the fluid flows through the orifice 32 from one side to the other, and due to the viscous resistance generated during the flow,
Vibration input in the low frequency range can be effectively damped.

However, the cross-sectional area and length of this orifice 32 are determined so that the peak of attenuation (loss factor) occurs in the low frequency range (for example, about 5 to 10 Hz) where attenuation is most needed.
When a high-frequency vibration input of 200 Hz or higher, or even 400 Hz or higher is applied, the fluid does not pass through the orifice 32 due to the inertia of the fluid. In this state, fluid is confined in each fluid chamber 28, 30, and if the volume of these fluid chambers 28, 30 is hardly allowed to change, this will impede the elastic deformation of the fluid rubber elastic body 20, so dynamic As the spring constant increases,
The spring characteristics become hard, and the transmitted force becomes large.

However, as described above, in this anti-vibration bushing 10, rubber elastic membranes 40 and 44, which can be elastically deformed in response to fluctuations in pressure in each fluid chamber 28 and 30, are provided facing each fluid chamber 28 and 30, respectively. Therefore, even in a high frequency range where fluid no longer passes through the orifice 30, the rubber elastic membranes 40, 4
The elastic deformation action of 4 allows the volume of each fluid chamber 28, 30 to vary. For example, when a high-frequency vibration input acts to relatively displace the inner cylinder fitting 16 upward in FIG. 1, the fluid chamber 2
8 increases, but due to the increase in pressure, the rubber elastic membranes 42, 42 are elastically deformed to swell toward the holes 40, 40, respectively, absorbing the pressure in the fluid chamber 28, and increasing its volume. Allow. At this time, the pressure in the fluid chamber 30 on the opposite side decreases to a negative pressure state, but each rubber elastic membrane 46, 46
The fluid chamber 30 is elastically deformed so as to be concave toward the 0 side.
Balance the pressure. Therefore, each fluid chamber 28,3
Since the fluid confined within 0 does not produce a rigid action and does not hinder the elastic deformation of the rubber elastic body 20, the dynamic spring constant is suppressed to a low level against excitation input in the high frequency range, making it soft. Spring characteristics can be obtained. As a result, the transmission force can be reduced, and the vibration isolation performance against high frequency vibrations and noises such as gear noise and road noise of automobiles can be improved.

In addition, the holes 40, 40 on the fluid chamber 28 side and the fluid chamber 3
Since the holes 44, 44 on the 0 side are communicated with each other by the circumferential groove 48 formed on the inner peripheral surface of the cylindrical mounting portion 16, each hole 40, 44 of the outer cylinder fitting 18
Although this alone allows the rubber elastic membranes 42, 46 to bulge and deform to the outside, such communication through the circumferential groove 48 makes it easier for each rubber elastic membrane 42, 46 to elastically deform. Moreover, the rubber elastic membranes 42, 4
2 expands outward, the air in the holes 40, 40 moves toward the fluid chamber 30 through the circumferential groove 48, acting to assist the elastic deformation of the rubber elastic membranes 46, 46 inward. Furthermore, by the movement of air through the circumferential groove 48, a kind of air damper-like effect can be expected to absorb and reduce high frequency vibrations to some extent.

Note that these rubber elastic membranes 42 and 46 are elastically deformed outward and inward even when low-frequency, large-amplitude vibration input is applied, but changes in the volumes of the fluid chambers 28 and 30 due to these elastic deformations are as follows. Rubber elastic body 2
This is much smaller than the change in volume caused by the elastic deformation of zero, so it does not pose a problem in flowing the fluid through the orifice 32 between the fluid chambers 28 and 30 during low-frequency, large-amplitude vibration input. It's not what it is. In other words, each rubber elastic membrane 4
The amount of elastic deformation of the fluid chamber 2 in the high frequency range where no fluid flows through the orifice 34 is
It is said to be suitable for absorbing pressure fluctuations of 8.30 degrees, thereby making it possible to soften the dynamic spring characteristics against high frequency vibrations while maintaining high damping characteristics against low frequency vibrations. It is.

In addition, as another aspect of the present invention, as shown in FIG. A smaller hole 52 is formed at a corresponding position to penetrate through the hole 5.
It is also possible to communicate the hole 40 with the circumferential groove 48 via the groove 2 . In this way, excessive outward elastic deformation of the rubber elastic membrane 42 is prevented by the inner peripheral surface of the holding sleeve 50 of the bush itself. However, even with the above structure without the retaining sleeve 50, as is clear from FIG. The amount of elastic deformation will be defined.

Further, as shown in FIG. 9, the rubber layer 3
A holding plate 54 is provided on the inner peripheral side of the outer cylinder fitting 18 and is sandwiched between the holding plate 54 and the outer cylinder fitting 18. By forming the holes 56 at the sides, the rubber elastic membrane 42 faces the fluid chamber 28 side, and the structure allows elastic deformation of the rubber elastic membrane 42 between these holes 40 and 56. Also good.

Furthermore, as shown in FIG.
The hole 40 may be wide enough to correspond to the size of the hole 40 formed in the hole 8. However, there is a circumferential groove 4 on the mounting part 14 side.
8 is not an essential requirement and can be omitted. 8th as above
The explanations in FIGS. 10 to 10 also apply to the rubber elastic membrane 46 and holes 44 on the fluid chamber 30 side.

Further, each elastic membrane 42, 46 is covered with a cylindrical rubber layer 3.
8, each hole 40,4
The rubber elastic membranes 42 and 46 may be provided in fixed positions only in the portions corresponding to 4. Further, the position and number of the elastic membranes 42, 46 relative to the fluid chambers 28, 30 can be changed as appropriate depending on the structure of the bush. Although not illustrated in detail, it goes without saying that the present invention includes various modifications and improvements based on the knowledge of those skilled in the art.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a vibration-proof bushing according to an embodiment of the present invention and its installed state. 2 is a cross-sectional view taken from FIG. 1, and FIG. 3 is a cross-sectional view taken from FIG. 1. FIG. 4 is a partially cutaway perspective view of one of the anti-vibration objects shown in FIG. 1. FIG. FIG. 5 is a partially cutaway front view of the outer bushing assembly obtained in the manufacturing process of the anti-vibration bushing shown in FIG. 1, etc., and FIG. 6 is a cross-sectional view thereof. FIG. 7 is a longitudinal sectional view of the bush main body obtained in the same manufacturing process. Figures 8, 9 and 1
FIG. 0 is a partial cross-sectional view showing the main parts of another embodiment of the present invention, and both correspond to FIG. 3. 10: Anti-vibration bushing, 12: Anti-vibration object, 1
4: Cylindrical mounting portion, 16: Inner tube fitting, 18: Outer tube fitting, 20: Rubber elastic body, 22: Outer sleeve, 24: Recess, 26: Window portion, 30: Fluid chamber, 3
2: Orifice, 34: Orifice forming block, 36: Communication hole, 38: Thin rubber layer, 40,4
4, 56: Hole, 42, 46: Rubber elastic membrane, 48:
Circumferential groove, 50, 54: holding sleeve.

Claims (1)

[Scope of Claims] 1. An inner cylindrical fitting and an outer cylindrical fitting arranged concentrically at a predetermined distance from each other, and a cylindrical rubber elastic body interposed between the inner cylindrical fitting and the outer cylindrical fitting. , a plurality of fluid chambers each filled with a predetermined incompressible fluid, formed by covering a plurality of recesses opening in the outer peripheral surface of the rubber elastic body with the outer cylindrical fitting; It is provided with an orifice that communicates with each other and allows fluid to flow between the fluid chambers, and is used by being attached between the intended vibration-isolating objects on the inside of the inner cylindrical fitting and the outside of the outer cylindrical fitting. In the structural bush, a rubber elastic membrane facing the fluid chamber is fixedly provided on the outer cylindrical fitting side at a position corresponding to at least a part of the opening of the recess provided in the rubber elastic body, and A cavity is formed in the rubber elastic membrane on the side of the outer cylindrical fitting opposite to the fluid chamber, and the rubber elastic membrane is made elastically deformable between the cavity and the fluid chamber, and A fluid-filled anti-vibration bushing characterized in that the rubber elastic membrane can be elastically deformed in response to fluctuations in pressure in a fluid chamber. 2. The rubber elastic membrane is formed of a part of a thin rubber layer vulcanized and bonded over the entire inner circumferential surface of the outer cylindrical fitting, and on the other hand, the void space is formed by the rubber elastic membrane. The hole is formed by penetrating the outer cylindrical fitting in the thickness direction at a position corresponding to A window portion corresponding to each opening of the recess is formed in the outer peripheral sleeve, and the rubber elastic membrane faces a part of the window portion, and the outer peripheral sleeve has a window portion corresponding to each opening of the recess. 2. The bush according to claim 1, wherein the bush is held in the outer cylindrical fitting in a state in which the bush is in close contact with the layer. 3. Each of the holes forming the cavity can communicate with each other by a circumferential groove formed on the inner circumferential surface of the vibration-isolating object into which the outer cylindrical metal fitting is fitted. Bushes as described in Range 1 and 2.