JPH01210637A - Liquid enclosed bushing - Google Patents

Abstract

PURPOSE:To control a dynamic spring constant and damping force by filling a liquid chamber and communicating path with electric viscous fluid and making the outside surface of an intermediate tube and the inside surface of an outer tube conductive to apply an electric field to the communicating path and increase the viscosity of said fluid. CONSTITUTION:A recess is provided in a window 14 position of an intermediate tube 5 of an elastic body 3, and two liquid chambers 4 are formed symmetrically about the axis between said tube 5 and an outer tube 2. Electric viscous fluid in both liquid chambers 4 is capable of flowing through two communicating paths 7. Under this constitution, when voltage is applied to the bushing intermediate tube 5, an electric field is generated in the communicating paths 7 surrounded by said tube 5 and a bushing outer tube 2 to increase the viscosity of electric viscous fluid in said path 7, so that the fluid hardly smoothly flows in said paths 7 to load said paths and heighten a dynamic spring constant.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a liquid-filled bushing that can be used as an engine mount or body mount bushing for the purpose of improving automobile vibration, interior noise, riding comfort, etc. It is.

<Prior art> A liquid-filled bushing with high damping characteristics was devised to reduce vibration transmission from car suspension components (arms, ronds, links, etc.) and from the engine mount to the car body. 1 For example, as seen in Figure 15.16, German Patent No. 2841505 has an inner cylinder (1) and an outer cylinder (2) arranged concentrically or eccentrically with respect to the inner cylinder (2) and spaced apart from each other. It is composed of a rubber elastic body (3) inserted between them, and Hi
A fluid-damped rubber bearing is shown in which fluid chambers (4) are formed which are filled with f'f fluid and are in hydraulic communication with each other via a throttle position. Such a liquid-filled bushing has a rubber part (3) and an inner cylinder (1) arranged concentrically inside the outer cylinder (2), and is further fixed to the rubber part (3).
In addition, a groove (6) for connecting the liquid chambers (4) with each other is formed around the intermediate cylinder (5) provided with a window in the area of the liquid chamber (4), and this groove (6) is similar to the window. It has a structure that is sealed outwardly, and a high damping effect is created by the flow resistance generated when the buffer solution in one liquid chamber flows into the other liquid chamber through the groove during excitation vibration. . A bushing-type vibration isolator has also been devised in which an actuator controls the opening and closing of a communication path between liquid chambers for the purpose of switching the spring constant of such a liquid-filled bushing (Japanese Patent Laid-Open No. 62-10193).
No. 6).

<Problems to be Solved by the Invention> A conventional liquid-filled bushing, such as the former, in which a plurality of liquid chambers are provided and the liquid can flow through the liquid chambers through a communication path, has unchanged damping characteristics and spring characteristics; It suppresses only certain vibrations that are determined by the constituent members of the liquid-filled bushing, and furthermore, the dynamic spring constant becomes high in medium and high frequency vibrations (20Hz or more), making it easier to transmit vibrations. To solve this problem, it was necessary to be able to control the damping characteristics and spring constant characteristics of the liquid-filled bushing over a wide frequency range.

In addition, the structure of liquid-filled bushings such as the latter, which is equipped with a member that blocks the flow of the communication path and an actuator that drives it, makes it possible to control the flow and cutoff of the communication path and change the spring constant. The problem was that it was complicated and prone to failure. In order to solve this problem, it is necessary to simplify the structure without using such a mechanical switching means for circulating/blocking the communication path, and to keep the number of component parts to a minimum.

Measures to Solve Problem A> Therefore, as a result of various studies, we filled the liquid chamber and communication path with an electrorheological fluid whose viscosity changes depending on the electric field, and connected a power source to the intermediate cylinder and outer cylinder. By energizing the outer surface of the intermediate cylinder and the inner surface of the outer cylinder, an electric field is applied within the communication path, thereby solving the shortcomings of the conventional method.

The electrorheological fluid referred to here is a liquid in which a solid substance such as silica powder containing water is dispersed in a dispersion medium such as silicone oil, and when an @ field is applied, the apparent viscosity changes and changes with the electrolytic strength. Rise. When an electric field is applied, Binga 1
1. Has fluid-like properties.

Yield stress of shear? : It has a characteristic of flowing when it exceeds C.

In this electrorheological fluid, the yield cuff c increases with the electric field strength, and the shear stress of the flowing fluid increases. When an electric field is applied perpendicularly to the flow in the communication passage, pressure loss between the passages increases due to an increase in shear stress.

In order to use this fluid in a liquid-filled bushing and increase the apparent viscosity of the fluid to the extent that it can change the damping and spring constant characteristics of the bushing, an electric field strength of at least 500 V/+w+ is required in practice. become.

<Function> The liquid-filled bushing with this structure transfers voltage to the intermediate cylinder,
When no electric field is applied between the outer cylinders, no electric field is applied in the communication passage, the electrorheological fluid in the communication passage has a low viscosity, and the pressure loss of the fluid in the communication passage is small, so the spring constant changes from low frequency to high frequency. The value is low in a wide frequency range up to Although the spring constant becomes high in a frequency range above a certain value due to the clogging phenomenon of the fluid in the communication path, this frequency range is higher than the frequency range of the target vibration phenomenon, so this does not pose a problem.

When a voltage is applied, the viscosity of the electrorheological fluid in the communication path increases, and the pressure loss of the fluid in the communication path increases, so a peak of attenuation (loss factor) occurs in the low frequency region, and the applied voltage changes. As a result, the frequency at which the attenuation peak occurs can be controlled over a wide frequency range. Furthermore, the frequency at which the dynamic spring constant becomes the minimum value can be similarly moved.

<Example> Fig. 1 is a sectional view taken along line B-n in Fig. 2 of a liquid-filled bushing according to an embodiment of the present invention in a state where the outer cylinder is attached, and Fig. 2 is a side view of the same;
FIG. 3 is a cross-sectional view of the outer cylinder attached, corresponding to line A-A in FIG. 1. FIG. 4 is a diagram showing an example of an automobile power unit support device using the liquid-filled bushing. FIG. 5 is a perspective view of the liquid-filled bushing.

This liquid-filled bushing is located at the affected part of the middle cylinder (3) of the elastic body (3).
By providing a recess at the position 14) and forming a pocket between the outer cylinder (2) and the recess, two liquid chambers (4) are provided at symmetrical positions with respect to the axis. Liquid chamber (4
) The electrorheological fluid within the space is allowed to flow through two communication passages (7). One end of the outer cylinder (2) is caulked with the intermediate cylinder (5) and rubber elastic body (3) interposed therebetween. A lead wire (8) on the positive electrode side is connected to the metal intermediate cylinder (5) at the position shown in the figure. The bush outer cylinder (2) is press-fitted into the mounting bracket outer cylinder (10) and can be electrically connected to the mounting bracket outer cylinder (10), so by grounding the mounting bracket, the bush outer cylinder (2) becomes the ground side. There is.

The method of connecting the lead wire (8) to the intermediate cylinder (5) is as follows.
A connector (1) is provided with a protruding connection terminal (15) as shown in the figure, and the protrusion (5) can be inserted into the lead wire (8) side.
6) may be provided.

The electrical insulation between the bushing intermediate cylinder (5) and the bushing outer cylinder (2) is ensured by the rubber elastic body (
3) is maintained by turning. Further, if necessary, the inner peripheral surface of the outer cylinder (2) and/or the orifice surface of the intermediate cylinder (5) may be coated with an insulating film, such as Teflon.

When voltage is applied to the bushing intermediate cylinder (5), the communication path (7) surrounded by the bushing intermediate cylinder (5) and the bushing outer cylinder (2)
), and the viscosity of the electrorheological fluid in the communication path (7) increases. The distance between the bush intermediate cylinder (5) and the bush outer cylinder (2) is preferably 0.5w11 to 3III11.

If this interval is larger than this, the electric field will be weaker for the same applied voltage, and the viscosity change of the fluid will be smaller. On the other hand, the narrower the distance, the stronger the electric field becomes, but the bushing intermediate cylinder (
5) and the outer bush fJ(2) are maintained insulated. Insulation is maintained between the bushing intermediate cylinder (5) and the bushing outer cylinder (2).
), but in order to further improve the insulation, the intermediate bushing cylinder (5) is made of electrically insulating synthetic resin, etc., as shown in Figure 8-9. It is also possible to apply a voltage by metal plating the outer surface and connecting a lead wire (8) to the metal plating portion (11). In this case, the metal plating portion (11) is the minimum area including the lead wire connection portion and the communication path forming portion. Furthermore, the inner surface of the outer cylinder of the bushing can be coated with an insulating material (Teflon, fluororesin, etc.) to improve insulation.

The voltage applied to the bush outer cylinder (2) is supplied by a DC power supply type ffl (12) as shown in FIG. The voltage level is Ov~5KV. Application and cutoff of voltage and voltage level are controlled by a controller (13) connected to DC power supply type a (12). Controller (13
) is a detector (engine u
It receives signals from engine speed, vehicle speed, accelerator opening, gear shift position), identifies the state of the vehicle (idling state, steady running state, etc.), and controls voltage application/cutoff and voltage level based on the signals.

When no voltage is applied to the bush intermediate cylinder (5), the electrorheological fluid in the communication passage has a low viscosity and has the dynamic spring characteristics shown in FIG. 10. The dynamic spring constant remains low up to a certain frequency and is at or below disaster. The dead body is the shear spring constant of the rubber elastic body, and the dynamic spring constant of the liquid-filled bushing becomes -Lt,
Asymptotes to . If the frequency is higher than that, the fluid in the communication path will no longer flow smoothly, resulting in a clogging condition and an increase in the dynamic spring constant. Let us express the rising frequency of the dynamic spring constant by the inflection point frequency f inf of the graph.

This frequency f inf is determined by the length of the communication passage, the cross-sectional area, the shape of the entrance and exit, the roughness of the inner surface of the communication passage, the volume compliance of the liquid chamber (bulging rigidity of the elastic wall), the compressibility of the liquid, the viscosity, etc. By appropriately selecting these, f inf is set to at least 50011z or more. Therefore, the dynamic spring constant is low at least up to 30011 z, and vibration transmission in a wide frequency range of 20 Hy to 300 Hz can be suppressed.

In this way, f inf can be set to a sufficiently high frequency by increasing the cross-sectional area of the communicating path and lowering the volume compliance of the liquid chamber (making the elastic wall difficult to swell). The viscosity should also be as low as possible. This can also be explained from the following theoretical analysis result, which assumes that the pressure loss in the communicating path is proportional to the flow velocity in a Newtonian fluid.

In the following explanation, the viscosity μ is assumed to be the inherent viscosity of an electrorheological fluid when no electric field is applied or the apparent viscosity when an electric field is applied.

The inflection point frequency f inf is expressed by the following equation.

■f 1nf= f no 1-4/3ζ” -16
/81ζ'-64/729(' +-... fno is the natural vibration determined by the amount of fluid JR within the effective flow path length of the communication path, the volume compliance of the liquid chamber, and the compressibility of the fluid, ■ f n □ = 1/2π, 4a/p Qe ・1/
(CV+VX) a: Communication passage cross-sectional area Qe: Effective passage length Cv: Volume compliance of liquid chamber (ΔV/ΔP, ΔV
, ΔP is the change in volume of the liquid chamber, and the change in pressure. ζ is the damping ratio, ■ ζ=K·μ/(4πρf n□) K: constant determined by the cross-sectional dimension of the communication passage μ: liquid viscosity.

According to formulas ■, ■, and ■, the inflection point frequency f inf depends on the natural frequency fn□ and damping ratio ζ of the reciprocating vibration of the fluid mass in the communication passage, and the cross-sectional area a of the communication passage is increased. Alternatively, the inflection point frequency f inf can be set to a desired high frequency by reducing the volume compliance Cv to make the elastic wall surrounding the liquid chamber difficult to swell, or by using a fluid with low viscosity. It is also possible to increase the inflection point frequency f inf by shortening the communication path length (small effective flow path length Qe), but if such a method is adopted, the loss factor peak value of the liquid-filled bushing will decrease and it will not be sufficient. A proper damping effect cannot be obtained.

In addition, as shown in Fig. 10, the dynamic spring constant becomes the minimum at the frequency f win, and if this frequency f + iin is made to match a specific frequency such as a muffled sound (mainly the second-order component of the engine speed), Vibration transmission to the vehicle body can be further suppressed. It is known that fmin moves to the lower frequency side when the viscosity of the fluid increases (Fig. 11), and according to the theoretical analysis mentioned above, ■ f m1n = f no 1
-2 different things. Since μ is related by Equation 0, f win can be set to the frequency in question by adjusting the viscosity μ according to Equation 0. When a voltage is applied to the bush intermediate cylinder, the viscosity of the fluid in the communication path increases, making it possible to shift fIlin to the lower frequency side. In this way, f win can be controlled by adjusting the applied voltage,
f tain can be easily adjusted to the frequency of the muffled sound. Furthermore, if there are multiple problematic frequencies such as muffled noise, the transmission of problematic vibrations can be suppressed by adjusting the applied voltage so that f win matches each frequency according to changes in engine rotation.

Note that the depth of the valley at the minimum dynamic spring constant Δ−twi
The larger n is, the more effective it is in reducing vibration transmission.

If the liquid viscosity is kept low so as not to bring f min too much to the low frequency side (without increasing the applied voltage level), the pressure loss in the communication path will be reduced, and the Δ hole + win will become deeper. Therefore, the closer f win is to the high frequency, the greater the effect of reducing vibration transmission due to the minimum dynamic spring constant. The relationship between Δ-1w1n and liquid viscosity fwin described here is as follows:
This can also be explained from the theoretical analysis mentioned above.

Δ-IL win is expressed by the following formula.

064. m1n=2aAtAc/ p Q c” (2
/CV+V d)” (1/4?Cf n □)”・
1/ζ (ζ+1) AtS Equivalent pressure receiving area Ac of liquid chamber: Equivalent piston cross-sectional area of liquid chamber (ΔV/ΔXa, ΔX
c: Relative displacement between the inner cylinder and the outer cylinder) According to this formula, the lower the liquid viscosity, the smaller the damping ratio ζ, so Δi win becomes larger and the valley of the minimum dynamic spring constant can be deepened. At this time, since ζ becomes small, f win shifts to the high frequency side according to equation 0. The damping ratio ζ is controlled by adjusting the applied voltage through changes in the viscosity of the liquid.

When the applied voltage is increased to a large value of around 5KV, the fluid in the communication path becomes highly viscous, and the inflection point frequency f inf where the dynamic spring constant increases moves to a low frequency region of 1511z or less (
12, 13). What's important here is this.

As f inf moves, the frequency fp at which the loss factor is maximum also moves to the same low frequency region, and the resonance vibration in that frequency band is damped by its large damping force. It is highly effective in suppressing vibrations such as shake that occur during normal vehicle operation. Since the frequency fP is changed by adjusting the applied voltage level (?1 press-in → fluid viscosity → fp decrease), it is easy to tune the shake to the resonance frequency.

With the structure described above, it is possible to act as shown below in response to vibrations caused by various vehicle driving conditions.

(El) Effect on shake during steady running The controller (13) receives a signal from the detection means, determines the occurrence of shake, and issues a control signal to the DC power supply (12). At this time, 5K from the DC power supply (12)
A high voltage around V is applied to the bush intermediate cylinder (5), and the fluid in the communication path becomes highly viscous.

Frequency fP of loss factor peak of liquid-filled bushing
has a shake frequency of 101-1z to 1311z, so it is possible to attenuate the shake vibration of the engine and reduce the vibration level transmitted to the vehicle body.

Since the frequency fp of the loss factor peak is adjusted by the applied voltage, tuning of fp is easy.

(b) Effect on idling vibration and muffled noise during running The controller receives the signal from the detection means, determines the occurrence of idling vibration or muffled sound, and controls 43 to turn off the voltage application to the DC power supply unit Fi (12). issue a number. In this case, no voltage is applied to the bushing intermediate cylinder (5) and no electric field is applied within the communication path.

The fluid in the communication path has low viscosity. Therefore, the inflection point frequency at which the dynamic spring constant increases is 500117. As a result, the dynamic spring constant is low over a wide frequency range from low frequency to 50011z, and transmission of engine vibrations is suppressed. In particular, when a muffled sound occurs, the muffled sound frequency (mainly the two components of the engine speed) is determined by detecting the engine speed, and the frequency f win at which the dynamic spring constant is minimized is matched to this muffled sound frequency. Apply voltage and adjust its level. In this way, crowded rows can be further reduced. f w
Since changing in simply changes the applied voltage level, even if the engine speed changes and several muffled sounds with different frequencies are generated, they can be easily reduced.

In this example, two communication paths are provided, but there may be only one or three or more communication paths.

Although the embodiment shows an example of reducing shake, engine idling vibration, and muffled running, this liquid injection bushing can also be used as a suspension arm bushing or a trailing link bushing.

<Effects of the Invention> By applying an electric field within the communication passage to increase the apparent viscosity of the electrorheological fluid, the pressure loss in the communication passage can be changed and the dynamic spring constant and damping force of the liquid-filled bushing can be controlled.

Idle vibration and muffled noise can be reduced by lowering the spring constant. In addition, shake can be reduced by the damping effect.

Since the bushing intermediate cylinder and outer cylinder are used as electrodes, there is no need for new electrode members, and the dynamic spring constant and damping force can be changed with a simple structure (same as the structure of conventional liquid-filled bushings).

By adjusting the applied voltage level, the pressure loss in the communication path is changed and the frequency of the loss factor peak and the minimum frequency of the dynamic spring constant are controlled, so variations in these frequencies during the manufacturing stage can be absorbed by adjusting the applied voltage.

[Brief explanation of the drawing]

FIG. 1 is a sectional view taken at 1 (-B) in FIG. 2 of the liquid-filled bushing of the present invention in a state where the outer cylinder is not attached, FIG. 2 is a side view of the same, and FIG. Fig. 4 is a sectional view of the corresponding outer cylinder mounted state. Fig. 4 is a schematic diagram showing an example of an automobile power unit support device using the same liquid-filled bushing. Fig. 5
The figure is a perspective view of the liquid-filled bushing. Figure 6 is the 5th
It is a cross-sectional perspective view of the P part in the figure. 7 to 9 are perspective views of an intermediate cylinder in another embodiment of the present invention. FIG. 1O, FIG. 11, and FIG. 13 are graphs showing changes in dynamic spring constant with respect to frequency. FIG. 12 is a graph showing the frequency at which the loss factor is maximum. FIG. 14 is a graph showing the relationship between shear stress and deformation rate. FIG. 15 is a partially cutaway side view of a conventional product, and FIG. 16 is a partially cutaway side view of the same essential part. (1) Inner cylinder (2) Outer cylinder (3) Elastic body
(4) Liquid chamber (5) Intermediate cylinder
(6) Groove (7) Communication path (8) Lead wire (
10) Mounting bracket outer cylinder (11) Metal plating part (1
2) DC power supply (13) Controller (1)
4) Window of intermediate tube (15) Connection terminal or above

Claims (1)

[Claims] 1. An inner cylinder (1) and an outer cylinder (2) arranged concentrically or eccentrically.
) between the intermediate cylinder (5) and the inner cylinder (1) and between the intermediate cylinder (5) and the inner cylinder (1).
5) and the outer cylinder (2), an elastic body (3) is provided between the elastic body (3) and the intermediate cylinder window (14), and a recess is provided between the outer cylinder and the recess. A pocket liquid chamber (4) is formed to seal in fluid, and a groove is provided in the elastic layer fixed to the outer periphery of the intermediate cylinder to provide a communication path (7) between the plurality of liquid chambers (4). A liquid-filled bushing characterized in that an electrorheological fluid is used as the fluid, and at least the outer surface of the intermediate cylinder (5) and at least the inner surface of the outer cylinder are electrically conductive. 2. The liquid-filled bushing according to claim 1, wherein the intermediate portion (5) and the outer cylinder (2) are electrically insulated from each other and connected to a positive or negative power source. 3. The liquid-filled bush according to claim 1, wherein the outer cylinder (2) has an insulating film formed on its inner surface.