JPH0555740B2 - - Google Patents

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a bush filled with viscous fluid, and more particularly to a new bush-type anti-vibration support for automobiles that utilizes viscous resistance due to shearing, so-called anti-vibration rubber for automobiles. be.

(Background technology) Anti-vibration characteristics required for automobile anti-vibration rubber, such as body mounts or cab mounts, member mounts, strut bar cushions, tension rod bushings, arm bushings, FF engine roll stoppers, etc., are required for sudden starts and sudden braking. , energy absorption using braking or damping during large inputs such as shakes, or reduction of vibration transmission force through damping in the case of resonance coupled vibration, and vibration transmission during high frequency minute inputs from engine rotation or road noise. This is a reduction in force. That is, the anti-vibration rubber must generally have both high damping characteristics at low frequencies and large amplitudes and low dynamic spring characteristics at high frequencies and small amplitudes.

However, normally, as long as a solid rubber material is used for vibration isolating rubber, if it can exhibit high damping characteristics, the dynamic spring characteristics at high frequencies will be high. If the damping force is made smaller without changing it, the damping force will also inevitably become smaller, and for this reason, it is difficult to realize a vibration isolating rubber that has both of the vibration damping properties at the same time using a rubber material.

In order to solve this problem, a fluid-filled vibration-proof rubber structure has been proposed in recent years (see Japanese Patent Publication No. 48-36151, Japanese Patent Publication No. 52-16554, etc.). Such a fluid-filled vibration isolator is equipped with two fluid chambers, and an orifice is provided in the part that separates the two fluid chambers, so that the volume of one fluid chamber can be reduced by vibration input. changes, and a structure is adopted in which the sealed fluid is forced to flow back and forth to the other fluid chamber through an orifice. As the fluid flows through the orifice, fluid viscous force and fluid inertia force are exerted as the fluid flows through the narrowed tube, and in a mechanical model, the mass equivalent to the fluid inertia force is This will be demonstrated by arranging a system supported by a spring and a damper in parallel.

And, the inertial force generated by this fluid movement,
In other words, the mass-spring system plays a major role in response to vibration input in the low frequency range, acting as a phase shifter. Therefore, unlike a normal mass-spring system, the flow of fluid is originally caused by the pressure between each chamber, and the pressure fluctuation is already deviated by 180 degrees from the beginning with respect to the input vibration. As a result, the mass-spring system resulting from the fluid flow in the orifice becomes a vibration system whose phase shifts as the frequency increases from 180° to 0°, and the point where the flow rate is the largest is the point where the flow rate is the largest. Exactly 90° to vibration input
It has become more advanced and has the characteristic of exhibiting an apparently extremely large damping force. Therefore, when the resonance point of the mass-spring system due to inertia caused by this fluid movement is passed, the movement of the mass part stops, as in a normal mass-spring system, that is, the fluid movement stops, and only the main chamber vibrates. In response to an input, the system transitions to a support system with nowhere for fluid to go, resulting in a very rigid mount.

In short, in the case of the above-mentioned fluid-filled mount structure, it is unavoidable that the mount becomes rigid in the high vibration frequency range after resonance due to the inertial force of the orifice. Effective attenuation could not be expected.

(Structure of the Invention) The present invention has been made in view of the above circumstances, and its purpose is to prevent the mount from becoming rigid in a high frequency range,
An object of the present invention is to provide a bush-type viscous fluid-filled vibration-proof support that exhibits flat transmission force characteristics with respect to vibration frequency.

In order to achieve such an object, the present invention provides an arrangement between the inner cylindrical metal fitting and the outer cylindrical metal fitting placed concentrically or eccentrically on the outside thereof.
A cylindrical rubber elastic body is interposed to connect the metal fittings, and the rubber elastic body has a pair of symmetrical openings opening to the outer circumferential surface in the axially intermediate part thereof, and has a predetermined width. An annular cavity extending continuously in the circumferential direction is provided, and the opening of this cavity is covered with the outer cylindrical fitting to form one sealed annular fluid chamber. While enclosing a highly viscous fluid with high kinematic viscosity, the annular fluid chamber portions located on both sides of the inner cylindrical fitting in the direction perpendicular to the vibration input direction to be vibration-isolated are each narrowed in the radial direction. The structure is configured as a narrow shear gap extending over a predetermined length in the vibration input direction, and viscous resistance is caused by the shearing action of the high viscosity fluid in the shear gap when vibration is input. .

Moreover, in the viscous fluid-filled bushing according to the present invention, the annular fluid chamber is located at both sides of the inner cylindrical metal fitting in the vibration input direction, and the outer cylindrical metal fitting and the outer cylindrical metal fitting are connected to each other.
a plateau-like protrusion that protrudes from the inner cylinder metal fitting side within the fluid chamber, and at least a portion facing the outer cylinder metal fitting is made of a rubber elastic material, and serves as a narrow second gap portion that expands to have a predetermined area; Even in this narrow gap, viscous resistance is caused by the shear shear action generated in the viscous fluid due to the fluid expulsion action based on the vibration input, thereby achieving effective damping. The effect will be brought to bear.

Regarding the annular fluid chamber of a predetermined width in the viscous fluid-filled bushing according to the present invention, the two types of gaps formed on both sides of the inner cylindrical fitting so as to be perpendicular to each other in the radial direction of the bushing are substantially as follows: A gap of 1 mm to 6 mm is set between the opposing working surfaces forming the narrow gap so as to induce a desired shear stress in the high viscosity fluid.

Furthermore, the highly viscous fluid having a high kinematic viscosity used in the highly viscous fluid-filled bushing according to the present invention is typically silicone oil, and at least 10,000 centistokes of such silicone oil is used. A material having a kinematic viscosity of 100,000 to 1,000,000 centistokes is preferably used.

(Examples) Hereinafter, in order to clarify the present invention more specifically, typical examples of the present invention will be described in detail based on the drawings.

First, FIG. 1 shows a cross-sectional view of an example of a viscous fluid-filled bushing assembly in which the present invention is applied to a tension rod bushing for an automobile, and FIG. A top view is shown.

In those figures, the viscous fluid-filled bushing assembly according to the present invention has a thick-walled cylindrical inner metal fitting 2.
, a cylindrical outer metal fitting 4 arranged concentrically on the outside thereof, and an overall cylindrical shape molded from a predetermined rubber material, which connects the inner cylinder metal fitting 2 and the outer cylinder metal fitting 4. The cylindrical attachment part at the end of the tension rod is press-fitted into the outer peripheral surface of the outer cylindrical fitting 4 and is attached to the inner cylindrical fitting 2. A pivot attached to the vehicle body side or the axle side is inserted through the shaft and used.

By the way, in the bush assembly having such a structure, the inner cylindrical metal fitting 2 and the rubber block 6 are
As shown in the figure and FIG. 4, it is generally constructed and used as an integrally vulcanized molded product 8. Here, a thick metal ring 10 is press-fitted and fixed to the outer circumferential surface of the inner cylindrical metal fitting 2 at approximately the center in the axial direction, while a rubber block 6
A metal sleeve 12 is fixed to the outer peripheral surface of the metal sleeve 12. The metal sleeve 12 is also symmetrically provided with two windows 14, which are formed by cutting out a large rectangular shape from the cylindrical wall. By vulcanizing the rubber block 6 in the presence of the metal ring 10, the press-fitted inner cylindrical fitting 2, and the metal sleeve 12, the desired integrally vulcanized molded product 8 is formed. Note that this integrally vulcanized molded product 8 is subjected to a drawing process such as an eight-way drawing process, if necessary, and is subjected to preliminary compression.

Furthermore, in the integrally vulcanized molded product 8, an annular space 16 is formed in the axially intermediate portion of the rubber block 6, and extends continuously in the circumferential direction with a predetermined width. Further, as is clear from FIG. 3, the metal sleeve 12 is structured to open into the outer circumferential surface of the rubber block 6 at portions corresponding to the respective windows 14, 14.

Then, so as to be located within such empty space 16,
A metal ring 10 press-fitted into the inner cylinder fitting 2 is arranged, and further on this metal ring 10,
Rubber of a predetermined thickness is molded integrally with the rubber block 6, thereby forming a terrace-like protrusion 18 at a predetermined height within the cavity 16. That is, the plateau-like protrusion 18 is composed of a metal ring 10 and a rubber layer 20 of a predetermined thickness that is integrally vulcanized and bonded thereon. It is thickened at a position corresponding to the area and bulges outward. On the other hand, the spaces 16, 16 located on both sides of the inner cylinder fitting 2 in the direction orthogonal to the direction in which the rubber layer 20 extends are narrowed in the radial direction due to the protrusion of the plateau-like protrusion 18. As a result, they are formed as shear gaps 22, 22 each extending a predetermined length in directions parallel to each other and having a narrow U-shaped or U-shaped cross section (FIG. 4). Note that this shear gap 22
is formed as a gap of 1 to 6 mm.

Then, using the integrally vulcanized molded article 8 having such a structure, it is heated with a predetermined high-viscosity fluid, such as silicone having a kinematic viscosity of 10,000 centistokes or more, preferably 100,000 to 1 million centistokes.
In a fluid such as oil, if the outer cylindrical fitting 4, which has a sealing rubber layer 24 integrally provided on its inner circumferential surface, is press-fitted, the hollow 1 formed in the rubber block 6 will be closed.
By covering the opening of 6 with the outer cylindrical fitting 4, as shown in FIGS. 1 and 2,
An annular fluid chamber 26 having a predetermined width and filled with a highly viscous fluid is formed around the inner cylindrical fitting 2 . In addition, by covering the cavity 16 with the outer cylindrical fitting 4, a predetermined area is formed between the plateau-like protrusion 18 protruding at the opening portion and the outer cylindrical fitting 4 in the axial and circumferential directions. A second gap portion 28 having a narrow arc shape expanding in the direction is formed. Note that, like the shearing gap 22, this gap 28 is also formed at a gap of 1 to 6 mm.

Note that after the outer cylindrical fitting 4 is press-fitted into the integrally vulcanized molded product 8, the outer cylindrical fitting 4 may be placed in the high-viscosity fluid in which it was press-fitted, or after being taken out from such a fluid. A drawing process such as eight-sided drawing process is performed, and further a drawing process such as passing through a predetermined die is performed to reduce the diameter, so that in addition to the seal rubber layer 24, the outer cylinder fitting 4 and the metal sleeve 12 will be improved. In addition, both ends of the outer cylinder fitting 4 are
The integrally vulcanized molded product 8 is crimped and fixed to the metal sleeve 12 on the outer periphery by roll crimping.

Therefore, in a viscous fluid-filled bushing assembly having such a structure, the input direction of vibration is the direction indicated by the arrow (broken line) P in FIG. 1, that is, the vibration is generated in the vertical direction in FIG. 2, the shear gaps 22, 22 extend in the direction parallel to the input direction of such vibrations, and the narrow shear gaps 22, 22 are located on both sides of the inner cylinder fitting 2, respectively. Due to the relative movement of the forming opposed working surfaces (rubber block 6; rubber layer 20), an effective shearing action is induced in the highly viscous fluid present therein, so that due to the shearing of such viscous fluid, A predetermined viscous resistance will be generated. That is, here, the viscosity coefficient of the high viscosity fluid: μ, the area of the shear gap 22: A,
Assuming that the size (distance) of the shear gap 22 is h and the speed of vibration is v, the resistance force F due to shearing of the viscous fluid is given by the following formula: F = (μA/h)v. Therefore, an effective viscous resistance is generated substantially independent of the frequency of the input vibration. Then, the damping force is caused by the resistance force F based on the viscous resistance due to this shearing, in proportion to the size of the area A that is subjected to such shearing action.

Incidentally, FIG. 5 shows the results of a comparison of the vibration damping characteristics of the high viscosity fluid filled bushing assembly according to the present invention as exemplified above with a conventional orifice type fluid filled bushing assembly. The graph in Figure 5 shows the transmission force characteristics and phase angle of each bushing with respect to the vibration frequency when constant vibration is applied with an amplitude of ±0.05 mm. As the transmission force increases, in other words, the transmission force becomes extremely large in the high frequency region after resonance, whereas the bushing assembly according to the present invention exhibits flat transmission force characteristics, especially in the high frequency region. It exhibits excellent dynamic characteristics in transmitting force, especially vibration damping power.

In addition, in this exemplary bushing assembly, the annular fluid chambers 26 are located on both sides of the inner cylindrical metal fitting 2 in the vibration input direction P (upper and lower parts in FIG. 1), respectively. 2
The plateau-like protrusion 18 protruding from the side forms the arc-shaped second gap 28 between the outer cylinder fitting 4 and the narrow gap 28. , 28, when the vibration is input, a pressing force acts on the high viscosity fluid existing there, and the high viscosity fluid is expelled from the space in the left and right direction (circumferential direction) as shown by the arrow in FIG. From the point where the action is applied, a flow is induced in such a highly viscous fluid, and a shear shear stress proportional to the velocity gradient of the flow is generated, whereby an effective damping force can also be conceived, and the shear gap This acts synergistically with the viscous resistance in the parts 22, 22, and an effective vibration damping effect is exerted on the bush as a whole.

In addition to these illustrative specific examples, the present invention may be modified in various ways based on the knowledge of those skilled in the art without departing from the spirit of the present invention. It should also be understood that such embodiments are also included.

For example, in the previous example, the inner cylindrical metal fitting 2 and the outer cylindrical metal fitting 4 were arranged concentrically, but these metal fittings may be arranged eccentrically as necessary, and the outer cylindrical fitting 4 and the plateau-like protrusion 18 There is no problem with the shape of the gap 28 formed between the shear gap 22 and the shear gap 22, in addition to the circular arc shape.

In addition, in the present invention, the length and width (circumferential and axial lengths) of the shear gap 22 and the second gap 28, in other words, the area of the gaps 22 and 28, are determined to achieve the desired viscosity. It will be appropriately selected depending on the magnitude of the resistance or shear stress and, ultimately, the damping effect.

In addition to the tension rod bushing shown in the example, the vibration damping support of the bushing structure to which the present invention is applied includes many automobile damping supports such as body mounts, strut mounts, arm bushings, and FF engine roll stoppers. For example, a swinging rubber can be mentioned, and it can be advantageously applied to any of them.

(Effects of the Invention) As is clear from the above description, the viscous fluid-filled bushing according to the present invention effectively attracts fluid in two types of narrow gaps formed in a part of the annular fluid chamber. , which induces an effective vibration damping effect based on viscous resistance caused by shear stress, exhibits flat transmission force characteristics with respect to vibration frequency, and exhibits excellent damping force against high-frequency vibrations. It has great industrial significance because it exhibits unique transmission force characteristics that are different from those of various conventional fluid-filled bushes.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a viscous fluid-filled bushing assembly according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view taken from FIG. 1. Also, the third
The figure is a cross-sectional view of an integrally vulcanized molded product used in such a viscous fluid-filled bushing assembly.
The figure is a - sectional view in FIG. 3. FIG. 5 is a graph showing transmission force characteristics and phase angle with respect to vibration frequency in the viscous fluid-filled bush assembly according to the present invention and a conventional orifice-type fluid-filled bush. 2...Inner cylinder metal fitting, 4...Outer cylinder metal fitting, 6...Rubber block, 8...Integrated vulcanized molded product, 10...Metal ring, 12...Metal sleeve, 14...Window part,
16...Vacancy, 18...Plateau-shaped protrusion, 20...Rubber layer, 22...Shear gap, 24...Seal rubber layer, 26...Fluid chamber, 28...Second gap.

Claims (1)

[Scope of Claims] 1. A cylindrical rubber elastic body is interposed between an inner cylindrical metal fitting and an outer cylindrical metal fitting placed concentrically or eccentrically on the outside of the inner cylindrical metal fitting, and these metal fittings are connected. , in the axially intermediate part of such a rubber elastic body,
An annular space having a pair of symmetrical openings opening on the outer peripheral surface and extending continuously in the circumferential direction with a predetermined width is provided, and the opening of this space is covered with the outer cylindrical metal fitting. A high viscosity fluid with high kinematic viscosity is sealed in the fluid chamber, and on both sides of the inner cylindrical fitting in the direction perpendicular to the direction of vibration input to be vibration-proofed. The annular fluid chamber portions located therein are each narrowed in the radial direction to form a narrow shear gap portion with a gap of 1 mm to 6 mm extending over a predetermined length in the vibration input direction, and the vibration In the portions located on both sides of the inner cylindrical metal fitting in the input direction, the outer cylindrical metal fitting and a plateau-like protrusion protruding from the inner cylindrical metal fitting within the fluid chamber, at least the outer cylindrical metal opposing portion are made of a rubber elastic material. The annular fluid chamber is configured as a narrow second gap section with a gap of 1 mm to 6 mm that expands with a predetermined area, and when vibration is input, the shear gap section and the second A viscous fluid-filled bushing characterized in that viscous resistance is induced in the gap by shear stress of the high viscosity fluid. 2. The viscous fluid-filled bushing of claim 1, wherein the highly viscous fluid is silicone oil having a kinematic viscosity of at least 10,000 centistokes.