JPH0320137A - Viscous fluid sealed bush - Google Patents

Abstract

PURPOSE:To secure a flat transfer force characteristic by installing a tubular rubber elastic body interposingly between an inner cylinder and an outer cylinder concentric with the former, sealing a high viscous fluid in an annular liquid chamber installed in an axial intermediate part of this rubber elastic body, and forming a shearing clearance part there. CONSTITUTION:An annular fluid chamber 26 is constituted as circular, fine clearance parts 28, 28 in a gap with an outer cylinder fitting 4 by a trapezoidal projection 18 being projected from the side of respective fittings 2 at a part to be situated at both sides of these inner cylinder fittings 2 in the vibration input direction P. At time of vibration input, pressing force works on a high viscous fluid existing therein works at these fine clearance parts 28, 28, whereby such an action as eliminating the high viscous fluid in the circumferential direction to be shown in an arrow is added from this space. Therefore a flow is produced in the high viscous fluid and thereby shearing force proportionate to a velocity gradient of the flow is generated there, through which effective damping force is also produced and an effective vibro-damping action is securable as the whole bush owing to viscosity resistance force and synergistic effect in shearing clearance parts 22, 22.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a viscous fluid-filled bushing, and more particularly to a novel bush-type anti-vibration support for automobiles that utilizes viscous resistance due to shearing, so-called anti-vibration rubber for automobiles. It is.

(Background technology) The anti-vibration properties required for automotive anti-vibration rubber, such as body mounts or cab mounts, member mounts, strut bar cushions, tensile rond bushes, arm bushes, FF engine roll stoppers, etc. , energy absorption using braking or damping during large inputs such as sudden braking or shaking,
Furthermore, in the case of resonant rapid vibration, the vibration transmission force is reduced by damping, and the vibration transmission force is reduced at the time of a small high frequency input from engine rotation or road noise. In other words, anti-vibration rubber generally must 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 vibration-isolating properties at the same time using rubber materials. To solve this problem, a fluid-filled vibration-proof rubber structure has been proposed in recent years (Japanese Patent Publication No. 48-36151, Japanese Patent Publication No. 52
-Refer to Publication No. 16554, etc.).

Such a fluid-filled vibration isolator is equipped with two fluid chambers, and an orifice is provided at the part that separates the two fluid chambers, so that the volume of one fluid chamber is reduced by vibration input. A structure is adopted in which the sealed fluid is forced to pass through the orifice to the other fluid chamber. The flow of fluid through the orifice exerts fluid viscous force and fluid inertia force due to the fluid flowing inside the narrowed tube, and in a mechanical model, the mass equivalent to the fluid inertia force is equivalent to a spring. This will be demonstrated by arranging systems supported by damping in parallel.

The inertial force generated by this fluid movement, that is, 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, fluid movement is originally caused by pressure between each chamber, and the pressure fluctuation is already deviated by 180 degrees from the beginning with respect to the input vibration. , the mass-spring system resulting from the fluid flow in the orifice part is 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 exactly where the vibration occurs. It is advanced by 90 degrees relative to the input, and has the characteristic of exerting an apparently extremely large damping force. Therefore, after passing the resonance point of the mass-spring system due to inertia caused by this fluid movement, the movement of the mass part stops, as in a normal mass-spring system, that is, the fluid movement stops, and vibration input only to the main chamber. On the other hand, the system transitions to a support system with nowhere for fluid to go, resulting in a highly rigid mount.

In short, in the fluid-filled mount structure as described above, it is unavoidable that the mount becomes rigid in the high vibration frequency range after resonance due to the inertial force of the orifice, and as a result, the mount becomes rigid in the high frequency range. Effective attenuation could not be expected. (Structure of the Invention) The present invention has been made in view of the above-mentioned circumstances, and its purpose is to prevent the mount from becoming a rigid body in a high frequency region, and to It is an object of the present invention to provide a bush-type viscous fluid-filled vibration-proof support that exhibits flat transmission force characteristics.

In order to achieve this objective, the present invention provides a cylindrical rubber elastic body between the inner cylindrical metal fitting and the outer cylindrical metal fitting that is positioned concentrically or eccentrically on the outside of the inner cylindrical metal fitting. An annular space having a predetermined width and extending continuously in the circumferential direction is provided in the axially intermediate portion of the rubber elastic body to connect the metal fittings. The opening of this space is covered with the outer cylindrical metal fitting to form one sealed annular fluid chamber, and a highly viscous fluid with high kinematic viscosity is sealed in the fluid chamber. The annular fluid chamber portions located on both sides of the inner cylindrical fitting in a direction perpendicular to the vibration input direction to be vibration-isolated are each narrowed in the radial direction and each extends over a predetermined length in the vibration input direction. The structure is configured as a narrow shear gap so that viscous resistance due to shear of the high viscosity fluid is induced in the shear gap when vibration is input. In the viscous fluid-filled bushing according to the present invention, preferably, the annular fluid chamber is located at both sides of the inner cylindrical metal fitting in the vibration input direction, respectively. and a center-like protrusion that protrudes from the inner cylinder fitting side within the fluid chamber and is formed of a rubber elastic material at least in the portion facing the outer cylinder metal fitting, and is configured as a narrow gap portion that expands with a predetermined area. Even in narrow gaps, the viscous fluid induces viscous resistance due to the fluid expulsion action based on the vibration input, thereby exerting an effective damping action. Furthermore, 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 cylinder fitting so as to be perpendicular to each other in the radial direction of the bushing are substantially , are suitably determined at a narrow enough interval to induce the desired shear stress in the highly viscous fluid between the opposing working surfaces forming the slit, but in practice, lllllll The gap will be set to approximately 6ms+. Further, 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 the amount of such silicone oil is at least 10,000 centistokes or more. A material having a kinematic viscosity of 100,000 to 1,000,000 centistokes is preferably used. (Example) In order to clarify the present invention more specifically, typical examples of the present invention will be described in detail below 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. 2 shows its cross-sectional view. A longitudinal section is shown.

In those figures, the viscous fluid-filled bushing assembly according to the present invention includes a thick-walled inner cylindrical inner cylindrical metal fitting 2, an inner cylindrical outer cylindrical metal fitting 4 disposed concentrically on the outside thereof, and It is configured to include a rubber block (rubber elastic body) 6 made of a predetermined rubber material and having an inner cylinder shape as a whole, which connects the cylinder metal fitting 2 and the outer cylinder metal fitting 4. The inner cylindrical attachment part of the end of the tension rod is press-fitted into the outer circumferential surface of the metal fitting 4 and attached, while the pivot shaft attached to the vehicle body side or the axle side is inserted into the inner cylindrical metal fitting 2 and is not used. It has become so.

By the way, in a bush assembly with such a structure,
As shown in FIGS. 3 and 4, the inner cylinder fitting 2 and the rubber block 6 are generally used as an integrally vulcanized product 8. There, the inner cylinder fitting 2
A thick metal ring 10 is press-fitted and fixed to the outer circumferential surface of the substantially central portion in the axial direction, while a metal sleeve 12 is fixed to the outer circumferential surface of the rubber block 6. Further, the metal sleeve 12 is symmetrically provided with two windows 14 and 14 formed by cutting out a large rectangular shape from the cylinder 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 intended integrally vulcanized impressive product 8 is formed. Note that this integrally vulcanized shaped product 8 is subjected to drawing processing such as eight-way drawing processing as necessary.
Preliminary compression will be added. In addition, in the integrally vulcanized molded product 8, an annular cavity 16 having a predetermined width and extending continuously in the circumferential direction is formed in the axially intermediate portion of the rubber block 6.
6 also includes a metal sleeve l, as is clear from FIG.
The structure is such that openings are formed in the outer circumferential surface of the rubber block 6 at portions corresponding to the respective windows l4 and l4 of the rubber block 6.

Then, a metal ring 10 press-fitted into the inner cylindrical fitting 2 is placed so as to be located in the space 16, and a rubber of a predetermined thickness is further placed on this metal ring 10, integrally with the rubber block 6. It is shaped like this, so that
A terrace-like protrusion l8 is formed at a predetermined height within the space l6. That is, the plateau-like protrusion 18 is composed of a metal ring lO and a rubber layer 20 of a predetermined thickness that is integrally vulcanized and bonded thereon. It is thickened at the position corresponding to the area and bulges outward. On the other hand, the spaces l6 and 16 located on both sides of the inner cylinder fitting 2 in the direction perpendicular to the direction in which the rubber layer 20 extends are narrowed in the radial direction by the protrusion of the plateau-like protrusion 18, respectively. The cross-sections have a narrow U-shape or U-shape (
This is in the form of shear gaps 22, 22 in Fig. 4). Note that this shear gap 22 is generally 1 to 6
It is formed as a gap of about InII1.

Then, using the integrally vulcanized molded article 8 having such a structure,
The sealing rubber layer 24 is integrally formed on the inner circumferential surface in a predetermined high viscosity fluid such as silicone oil having a kinematic viscosity of 10,000 centistokes or more, preferably 100,000 to 1,000,000 centistokes. When the outer cylindrical metal fitting 4 is press-fitted, the opening of the space l6 formed in the rubber block 6 is covered by the outer cylindrical metal fitting 4, and as shown in FIGS. 1 and 2. As shown in FIG. 2, one annular fluid chamber 26 having a predetermined width and filled with and sealed with a highly viscous fluid is formed around the inner cylindrical fitting 2. Moreover, by covering the space l6 with such an outer cylindrical metal fitting 4, an arc extending in the axial and circumferential directions with a predetermined area is formed between the plateau-like protrusion 18 protruding at the opening portion and the outer cylindrical metal fitting 4. A gap 28 having a narrow shape is formed. Note that, like the shearing gap 22, this gap 28 is also formed with a gap of about 1 to 6a+m. In addition, after the outer cylindrical fitting 4 is press-fitted into the integrally vulcanized crystal 8, the outer cylindrical fitting 4 is placed in the high viscosity fluid into 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. Further, both ends of the outer cylindrical metal fitting 4 are crimped and fixed to the metal sleeve 12 on the outer periphery of the integrally vulcanized molded article 8 by roll crimping. Therefore, in a viscous fluid-filled bushing assembly having such a structure, the input direction of vibration is indicated by the arrow in FIG.
Break! I) When vibration is input in the direction indicated by P, that is, in the vertical direction in FIG. In the narrow shear gaps 22, 22, the height existing there is An effective shearing action is induced in the viscous fluid, and a predetermined viscous resistance is generated due to the shearing of the viscous fluid. That is, if the viscosity coefficient of the high viscosity fluid is 2 μ, the area of the shear gap 22 is A, the gap size (distance) of the shear gap 22 is h, and the vibration speed is V, then the viscous fluid The resistance force due to shearing, F, is given by the following formula: F = (μA/h)v. Therefore, an effective viscous resistance is generated without being substantially affected by the frequency of the input vibration. It becomes. 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, regarding the vibration damping characteristics of the high viscosity fluid filled bushing assembly according to the present invention as exemplified above, the results of comparison with the conventional orifice type fluid filled bushing assembly are as follows.
As shown in the figure. The graph in Figure 5 is ±0.05
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 ++u++ are shown, but as the vibration frequency becomes higher, the bush assembly of the comparative example has the following characteristics: In contrast, the bushing assembly according to the present invention exhibits flat transmission force characteristics, and has excellent dynamic characteristics, especially vibration damping, in the transmission force in the high frequency region. It is demonstrating its power.

Further, in this exemplary bushing assembly, the annular fluid chamber 26 is connected to the inner cylinder fitting 2 in the vibration input direction (P).
In the portions located on both sides (the upper and lower portions in FIG. 1), plateau-like protrusions l8 protruding from the inner tube fitting 2 side create a narrow arc-shaped gap 28 between the outer tube fitting 4 and the plate-like protrusions l8. , 28,
In these narrow gaps 28, 28, when a vibration is input, a pressing force acts on the high viscosity fluid existing there, and the high viscosity fluid is drawn from the space in the left-right direction (as shown by the arrow in FIG. 1). When an expelling action is applied in the circumferential direction, a flow is induced in the highly viscous fluid, and a shear stress proportional to the velocity gradient of the flow is generated, which also produces an effective damping force. This acts synergistically with the viscous resistance force in the shear gaps 22, 22, so that an effective vibration damping effect is exerted on the bush as a whole. In addition to these specific examples, the present invention can be modified in various ways based on the knowledge of those skilled in the art without departing from the spirit thereof.
It is to be understood that the invention also includes such embodiments. 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 l8 Even if the shape of the gap 28 is formed between
In addition to the circular arc shape, a straight shape such as the shear gap 22 may be used without any problem. Of course,
Such a gap 28 is not essential to the present invention, and even if it is not formed, it is possible to achieve the object of the present invention.

In addition, in the present invention, the length and width (circumferential and axial lengths) of the shear gap 22 and the gap 28, in other words, the area of the gap 22 and the gap 28, are determined based on the desired viscous resistance or is appropriately selected depending on the magnitude of shear stress and, in turn, the damping effect.

Furthermore, in addition to the tension rods and bushes as illustrated, vibration-proof supports for bush structures to which the present invention is applied include body mounts, strut mounts, arm bushes, FF engine roll stoppers, and many other vibration-proof supports for automobiles. 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 is effective against viscous resistance due to shearing caused in the narrow gap formed in a part of the annular fluid chamber. Based on this, it induces an effective vibration damping effect, and exhibits flat transmission force characteristics with respect to the vibration frequency,
It has great industrial significance because it exhibits excellent damping force against high-frequency vibrations and exhibits unique transmission force characteristics that are different from the various conventional fluid bushings.

[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 along line 1 in FIG. Further, FIG. 3 is a cross-sectional view of an integrally vulcanized article used in such a viscous fluid-filled bushing assembly, and FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. FIG. 5 is a graph showing transmission force characteristics and phase angle with respect to vibration frequency in the viscous fluid filled bushing assembly according to the present invention and the conventional orifice type fluid filled bushing. Inner tube metal fitting Rubber block Metal ring Window section Terrace-like protrusion Shear gap Fluid chamber Outer tube fitting Integral vulcanized molded product Metal sleeve Cavity Rubber layer Seal Rubber layer Two gaps

Claims (3)

[Claims] (1) A cylindrical rubber elastic body is interposed between the inner cylindrical metal fitting and the outer cylindrical metal fitting placed concentrically or eccentrically on the outside thereof to connect these metal fittings, and the rubber elastic body An annular cavity having a predetermined width and extending continuously in the circumferential direction having an opening opening to the outer circumferential surface is provided in the axially intermediate part of the body, and the opening of this cavity is connected to the outer cylindrical fitting. A sealed annular fluid chamber is formed by covering the fluid chamber with a lid.
In addition, a highly viscous fluid with high kinematic viscosity is sealed in the fluid chamber, and 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 radially The narrow shear gaps are narrowed and extend over a predetermined length in the vibration input direction, so that viscous resistance due to shear of the high viscosity fluid is induced in these shear gaps when vibration is input. A viscous fluid-filled bushing characterized by: (2) The annular fluid chamber is located on both sides of the inner cylindrical metal fitting in the vibration input direction, and the outer cylindrical metal fitting and at least the outer cylindrical metal fitting that protrudes from the inner cylindrical metal side within the fluid chamber. 2. The viscous fluid-filled bushing according to claim 1, wherein the cylindrical metal fitting facing portion is configured as a narrow gap portion expanding over a predetermined area by a plateau-like protrusion made of a rubber elastic material. (3) The viscous fluid-filled bushing according to claim 1 or 2, wherein the highly viscous fluid is silicone oil having a kinematic viscosity of at least 10,000 centistokes.