JPH06330078A - Method for preparing electrorheological fluid - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] An electrorheological fluid that can be easily and stably prepared according to the required characteristics and that has a small fluctuation in viscosity with time. A method of preparation is provided. [Configuration] excellent oily medium electrically insulating upon preparing electrorheological fluid obtained by dispersing dielectric particles, a plurality of kinds of electro-rheological fluid and / or carbonaceous powder having a specific relaxation frequency f _o To mix.

Description

Detailed Description of the Invention

[0001]

[Field of Industrial Application] An electrorheological fluid is a fluid whose apparent viscosity changes rapidly and reversibly by applying a voltage to the fluid, that is, a fluid showing the so-called Winslow effect.
Generally, it is obtained by dispersing dielectric particles in an oil medium having excellent electric insulation. The characteristics of this electrorheological fluid have been known for a long time, and are expected to be applied to clutches, valves, vibration absorbers and the like. The present invention relates to an electrorheological fluid that exhibits an excellent electrorheological effect by using a specific carbonaceous powder as dielectric fine particles.

[0002]

2. Description of the Related Art Generally, electrorheological fluids are required to have a large viscosity change at a low voltage in terms of energy efficiency when an electric field is applied, and at the same time, a small amount of current flows at the same time. Does not settle in an oily medium, and the characteristics do not deteriorate during long-term use (for example, decrease in viscosity change, increase in current value), small change in characteristics due to operating temperature, and excellent responsiveness to voltage application. The viscosity does not fluctuate over time during application of voltage, and the viscosity of the fluid when voltage is not applied (hereinafter referred to as initial viscosity) is as low as possible.

That is, if a large change in viscosity can be realized under an external electric field of low current, the energy efficiency of various devices using electrorheological fluid can be improved. Also,
Solid particles that can achieve electrorheological fluid with low initial viscosity are
In an electrorheological fluid that requires a predetermined initial viscosity, the amount of solid particles in the fluid can be increased as compared with the solid fine particles of the electrorheological fluid with a high initial viscosity, and as a result, a high electrorheological change can be realized. Furthermore, if the viscosity and current value fluctuate during voltage application, it becomes difficult to control a device (apparatus) that uses the electrorheological fluid, and a sufficient change in viscosity cannot be obtained, which poses a practical problem.

Conventionally, as such an electrorheological fluid, water such as silica gel, starch and cellulose, and highly dielectric liquid such as alcohol are absorbed in an oil medium having high electric insulation such as transformer oil, spindle oil and chlorinated paraffin. With dispersed solid particles (US Pat. No. 2,886,151,
Nos. 3047507 and JP-A-53-175
No. 85, No. 53-93186, No. 61-44998.
No. 61-259752, 62-95397,
JP-A-1-207396, etc.), or various polymers are coated on the surface in order to improve the deterioration of characteristics during long-term use and the deterioration of performance at high temperature, which are caused by using solid particles that have absorbed water. And the like (Japanese Patent Application Laid-Open Nos. 47-17674 and 63-97694) are disclosed. Despite these suggestions,
It is hard to say that an electrorheological fluid that is practical and has sufficient performance has been developed.

[0005]

On the other hand, as the dielectric particles which can satisfy the performance required for the electrorheological fluid, the degree of carbonization (carbon atoms and hydrogen in the elemental analysis, which does not require a high dielectric liquid such as water) is required. The use of carbonaceous powder in which the ratio of the number of atoms = C / H) is controlled is disclosed in JP-A-3-279206. Such a carbonaceous powder is basically
An organic compound such as coal-based tar, coal-based pitch, coal liquefaction, petroleum-based tar, petroleum-based pitch, and resins is used as a raw material, and the raw material is heated in an autoclave, kiln, electric furnace, etc. at a maximum temperature of 300 to 800 ° C. After the heat treatment, it is manufactured by crushing and classifying the product obtained by the heat treatment.

It is also disclosed in Japanese Patent Laid-Open No. 3-279206 that the carbonaceous powder having the following characteristics is desirable. That is,
C / H is 1.70 to 3.50, or further the result of gravimetric analysis by a thermobalance (TGA) is 40 in a nitrogen atmosphere.
Weight loss in the range of 0 to 600 ° C is 0.5 to 1
It is desirable that the content is 3.0% by weight, the maximum particle size is 50 μm or less, and the average particle size is 0.5 to 40 μm. Therefore, the heat treatment step and the crushing / classifying step are adjusted so as to realize the above characteristics.

The electrorheological fluid prepared by using the above-mentioned carbonaceous powder is relatively excellent in that it exhibits a larger viscosity change at a low voltage and, at the same time, the current flowing therethrough is small and the response to voltage application is excellent. Although it exhibits excellent electrorheological properties, carbonaceous powder C may be present depending on the production lot.
The characteristics such as / H may vary, and it may not be possible to prepare an electrorheological fluid that meets the required characteristics.

An object of the present invention is to solve the above-mentioned problems of the prior art. The current value at the time of voltage application is small, the viscosity change is large, and the viscosity and current value during voltage application are stable as compared with the prior art. An object of the present invention is to provide a method of preparing an electrorheological fluid that can stably prepare an electrorheological fluid having electrorheological characteristics according to various required characteristics.

[0009]

[Means for Solving the Problems] The mechanism of manifestation of the electrorheological effect has not been fully clarified. However, it is generally considered that polarization is generated on the particle surface by the application of an external electric field, and the polarized particles attract each other by electrostatic attraction, resulting in an increase in apparent viscosity. Here, according to the study by the present inventors, the degree of this polarization depends on the electrical characteristics such as the dielectric constant and the electric conductivity of the dielectric particles. The electrical characteristics are C / H of the above-mentioned carbonaceous powder, weight reduction by TGA (content of low boiling point material),
It is closely related to the characteristics of carbonaceous powder such as particle size.

However, the characteristics of the dielectric particles, such as the above-mentioned carbonaceous powder, such as C / H (carbonization degree) and weight loss due to TGA, are subtle changes in the manufacturing environment and storage, and tar as a raw material. It easily changes depending on characteristics such as pitch, and it is currently difficult to stably manufacture dielectric particles having desired characteristics. Here, since the characteristics of the electrorheological fluid depend on the dielectric constant and the electric conductivity of the dielectric particles,
When an electrorheological fluid is prepared using dielectric particles having such different characteristics, it is not possible to obtain an electrorheological fluid that meets the required characteristics.

As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention mixed a plurality of types of electrorheological fluids and / or dielectric particles having different electrical characteristics to form an electrorheological fluid. It has been found that the characteristics can be adjusted to prepare an electrorheological fluid having the required characteristics. As described above, the electrorheological effect of the electrorheological fluid depends on the dielectric constant and the electrical conductivity of the dielectric particles dispersed in the electrically insulating fluid. Therefore, by mixing a plurality of types of electrorheological fluids having different electrical properties, that is, by mixing a plurality of types of dielectric particles having different electrical properties and using them, the electrical properties of the entire dielectric particles are adjusted. Thus, it becomes possible to prepare an electrorheological fluid having a desired electrorheological characteristic.

The frequency at which the dielectric loss curve of the electrorheological fluid exhibits a maximum value is called the relaxation frequency f ₀ .
Among the relaxation frequencies of a plurality of types of electrorheological fluids to be mixed and prepared, the relationship between the maximum relaxation frequency f _{0 .max} and the minimum relaxation frequency f _{0 .min} is 0 <log (f _{0 .max} / When f _{0 .min} ) ≦ 0.25, the properties of the electrorheological fluid to be mixed and prepared have very good additivity, and the properties of the electrorheological fluid can be adjusted easily and satisfactorily. Become.

The present invention has been made based on the above findings, and is a method for preparing an electrorheological fluid obtained by dispersing a plurality of types of dielectric particles in an oil medium having excellent electric insulation. Then, among the relaxation frequencies f ₀ of the respective electrorheological fluids when the electrorheological fluids are prepared by using one of each of the plurality of types of dielectric particles alone,
The maximum relaxation frequency f _{0 .max} and the minimum relaxation frequency f ₀ .
_A method for preparing an electrorheological fluid characterized by mixing an electrorheological fluid and / or dielectric particles satisfying the following equation: 0 <log (f _{0 .max} / f _{0 .min} ) ≦ 0.25 I will provide a.

In the preparation method of the present invention, it is preferable that the dielectric particles are carbonaceous powder containing carbon as a main component.

[0015]

[Structure] The method for preparing an electrorheological fluid of the present invention will be described in detail below. The method for preparing an electrorheological fluid of the present invention is a method for preparing an electrorheological fluid obtained by dispersing dielectric particles in an insulating oily medium, which comprises mixing a plurality of electrorheological fluids having different electric characteristics. By preparing an electrorheological fluid, that is, by mixing dielectric particles having different electrical characteristics to prepare an electrorheological fluid, it is possible to obtain an electrorheological fluid with required characteristics.

As described above, the electrorheological characteristics of the electrorheological fluid are largely influenced mainly by the electrical characteristics of the dielectric particles dispersed in the insulating oily medium, that is, the electric conductivity and the dielectric constant of the dielectric particles. . Therefore, if the dielectric particles do not have predetermined electric characteristics, it is not possible to prepare the electrorheological fluid having the required characteristics.

As a result of intensive studies, the inventors of the present invention prepared an electrorheological fluid by mixing a plurality of electrorheological fluids having different electrical characteristics to adjust the electrorheological characteristics of the electrorheological fluid. Have found that an electrorheological fluid having required characteristics can be prepared.

Mixing a plurality of electrorheological fluids having different electrical characteristics means mixing a plurality of types of dielectric particles having different electrical characteristics to prepare an electrorheological fluid. As described above, by mixing and using a plurality of types of dielectric particles having different electric characteristics, the electric characteristics of the entire dielectric particles can be adjusted. As described above, the electrorheological characteristics of the electrorheological fluid are due to the electrical characteristics of the dielectric particles used. Therefore, by appropriately selecting the characteristics and mixing ratio of the electrorheological fluid (dielectric particles) to be mixed, it is possible to prepare the electrorheological fluid that satisfies the required characteristics.

The electrical characteristics, mixing ratio, etc. of the electrorheological fluid to be used may be appropriately selected according to the characteristics of the target electrorheological fluid, but are preferably carried out as follows.

The present inventors have measured the dielectric behavior of an electrorheological fluid in which various dielectric particles are dispersed in an electrically insulating oil, and as a result, in the relationship between the dielectric loss of the fluid and the frequency, the dielectric loss depends on the dielectric dispersion. It has been found that there is a peak and the frequency at the maximum value, that is, the relaxation frequency f _0, depends on the conductivity of the dielectric particles. Furthermore, the peak of the dielectric loss of a fluid composed of dielectric particles with a single conductivity has a small spread, but some dielectric particles with different conductivity are mixed in the fluid. The peak in this case is the sum of the dielectric loss peaks at each conductivity, and there is a spread of the peaks, and when dielectric particles with a large difference in conductivity are mixed, the peaks appear in separate form. I found that.

As a result of further studies on the relationship between the relaxation frequency f ₀ and the characteristic of the electrorheological fluid (conductivity of the dielectric particles), the present inventors have found that each relaxation frequency of a plurality of types of electrorheological fluids to be mixed. of, the relaxation frequency f ₀ of the maximum value. relaxation frequency f of the minimum value _{max 0.} logarithm for the value defined by the _min 2.5
In the following, that is, when both satisfy the following formula 0 <log (f _{0 .max} / f _{0 .min} ) ≦ 0.25, the characteristics of the electrorheological fluid obtained when a plurality of types of electrorheological fluids are mixed It has been found that good additivity is generated, and the temporal fluctuation of the viscosity of the obtained electrorheological fluid can be made extremely small.

Therefore, if a plurality of types of electrorheological fluids satisfying the above conditions (that is, a plurality of types of dielectric particles satisfying the above conditions) are selected and mixed, the characteristics of the respective electrorheological fluids are Since it can be predicted that the sum is a characteristic of the mixed electrorheological fluid, the characteristic of the obtained electrorheological fluid by mixing in this way to prepare the electrorheological fluid is According to the additivity according to the characteristics of 1), it becomes possible to easily and surely prepare an electrorheological fluid having desired desired characteristics. Further, when the above-mentioned conditions are satisfied and the preparation is performed, the obtained electrorheological fluid can have excellent electrorheological characteristics in which the viscosity and the current value do not change when a voltage is applied.

The relaxation frequency f ₀ is measured, for example, by the following method. Dielectric particles are dispersed in an insulating oily medium at a predetermined volume fraction, and the frequency is changed from 10 Hz to 10 ⁷ Hz for measurement. With ordinary dielectric particles, dielectric dispersion due to interfacial polarization occurs in this frequency range, the dielectric constant of the fluid in which the powder is dispersed changes, and a relaxation frequency f ₀ at which the dielectric loss is maximized is obtained.

Therefore, the relaxation frequency f ₀ of each of various kinds of electrorheological fluids (dielectric particles) that can be used is measured,
Select an electrorheological fluid (dielectric particles) that satisfies the above formula and has characteristics that meet the required characteristics of the electrorheological fluid,
By mixing, it is possible to prepare an electrorheological fluid that preferably satisfies the required characteristics.

The types of electrorheological fluids and dielectric particles used in the present invention are not limited to two types, and three or more types of electrorheological fluids and dielectric particles may be used.
The type and mixing ratio of the electrorheological fluid and the dielectric particles to be used may be appropriately determined according to the characteristics of the target electrorheological fluid. In addition, it is preferable that the oily mediums in the plurality of kinds of electrorheological fluids to be mixed are the same. Further, not only a method of mixing plural kinds of electrorheological fluids, but also another dielectric particle is added to the previously prepared electrorheological fluid. As described above, the electrorheological fluid may be prepared by a method such as preparing.

In the method for preparing an electrorheological fluid of the present invention, the dielectric particles used in the electrorheological fluid used for the preparation are not particularly limited, and various kinds of known dielectric particles used in the electrorheological fluid can be used. Available, but preferably
Carbonaceous powder containing carbon as a main component is preferably used.

Such a carbonaceous powder contains carbon as a main component, which is obtained by subjecting tar pitch or the like to heat treatment, and then pulverizing and classifying. Above all, the value of C / H (ratio of the number of carbon atoms and hydrogen atoms in elemental analysis) indicating the degree of carbonization is 1.70 to 3.50, more preferably 2.00 to 3.50, and particularly 2. 20 to 3.00 and / or 40 under nitrogen atmosphere by TGA
Weight loss in the temperature range of 0 to 600 ° C is 0.5 to
A carbonaceous powder in the range of 13.0% by weight, preferably 0.5 to 6.0% by weight is used. This can be achieved by appropriately setting the temperature and time of each heat treatment in the carbonaceous powder manufacturing process.

By using a carbonaceous powder having a C / H in the range of 1.70 to 3.50, sufficient electrorheological characteristics can be obtained when an electrorheological fluid is prepared, and
It is possible to realize an electrorheological fluid having a small current value when a voltage is applied and having good energy efficiency. Also, C
/ H in the range of 2.00 to 3.50, and further 2.20 to
By setting the range to 3.00, this characteristic becomes more remarkable.

The average particle size of the carbonaceous powder used is preferably 0.5 to 40 μm, more preferably the average particle size 2
It is preferable to use a carbonaceous powder having a particle size of ˜40 μm, and particularly an average particle size of 2 to 10 μm. By using the carbonaceous powder having an average particle size in the above range, the carbonaceous powder can be uniformly and satisfactorily dispersed in an oil medium without settling when the electrorheological fluid is prepared, and the electrorheological fluid Better results can be obtained in that the initial viscosity can be suitably reduced.

The method for producing such a carbonaceous powder will be described below. Usually, as the raw material of the carbonaceous powder used in the present invention, coal-based tar, coal-based pitch, coal liquefaction, petroleum-based tar, petroleum-based pitch and the like, polyvinyl chloride, thermoplastic resins such as polyvinyl alcohol and the like. Organic compounds such as thermosetting resins such as phenol resin can be used. In addition, examples of other raw materials include polymers of condensed polycyclic aromatic compounds such as acenaphthylene, naphthalene, methylnaphthalene, anthracene, and phenanthrene, and monomers and polymers such as naphthacene. Also,
A compound obtained by polymerizing acenaphthylene, hydrogenated pyrene or the like by heat treatment can also be used. Examples of these polymers include polymers produced by using an acid catalyst such as HF-BF ₃ . These raw materials may be used alone as a starting material for the carbonaceous powder, or may be used as a mixture of two or more kinds.

When free carbon and ash are contained in the tar, it is preferable to remove them if necessary. Specifically, a generally industrially practiced removal method such as centrifugal separation or static separation by adding various solvents can be applied. Furthermore, coal tar pitches
Although it contains impurities such as silica and alumina, it is preferable to remove such impurities in advance.

Then, the above-mentioned raw materials are autoclaved,
Kiln, fluidized bed, electric furnace, etc. alone or in combination,
Maximum temperature 300-800 ° C, preferably 300-500
C / H value, TG of carbonaceous powder obtained by heat treatment at ℃
The amount of weight loss of 400 to 600 ° C. in A under a nitrogen atmosphere is adjusted to the above-mentioned target value.

The heat treatment may be performed once or plural times. In addition, during a plurality of heat treatments, a solvent extraction step for dissolving and removing unnecessary components, and / or
Alternatively, a particle size adjusting step may be provided. The heat treatment may be carried out by either a batch method or a continuous method.

Next, the carbonaceous powder thus obtained is pulverized and classified to bring the average particle diameter of the carbonaceous powder to the above-mentioned target value. This crushing / classifying step can be carried out by using a usual crushing and classifying apparatus. For example, a jet mill, a ball mill, an air classifier, a sieving apparatus and a method generally used industrially can be used.

Further, if necessary, the carbonaceous powder obtained by pulverizing and classifying may be reheated and / or depressurized. By performing this reheating treatment / decompression treatment, the low boiling point components existing on the powder surface can be effectively controlled and removed, and the surface of the powder particles can be homogenized while maintaining the main characteristics such as C / H. Thus, it becomes possible to manufacture a carbonaceous powder capable of realizing an electrorheological fluid having more excellent electrorheological characteristics.

If the reheating treatment and / or the depressurizing treatment is carried out at an excessively high temperature, the main characteristics of the carbonaceous powder may be changed, or the current value when a voltage is applied when using an electrorheological fluid may increase. Therefore, the reheat treatment and / or the depressurization treatment is usually performed at a temperature equal to or lower than the maximum temperature during the heat treatment before pulverization / classification.

The carbonaceous powder thus obtained is dispersed in an electrically insulating oily medium such as transformer oil, spindle oil, chlorinated paraffin, or silicone oil to prepare an electrorheological fluid.

When the carbonaceous powder is used as the dielectric particles in the method for preparing an electrorheological fluid of the present invention, the content of the carbonaceous powder in the finally prepared electrorheological fluid is 1 to 60% by weight. %, Preferably 20 to 50% by weight, and the content of the electrically insulating oil is 99 to 40% by weight, preferably 80 to 50% by weight. If the amount of carbonaceous powder is less than 1% by weight, the electrorheological effect is small, and if it exceeds 60% by weight, the initial viscosity in the absence of an electric field is remarkably increased and the fluidity is lowered.

[0039]

EXAMPLES The present invention will be described in more detail with reference to specific examples of the present invention. The present invention is not limited to the examples below.

Example 1 Coal tar pitch containing no free carbon was subjected to a primary heat treatment in a 20 liter autoclave at 510 ° C. for 3 hours under a nitrogen stream of 3 liter / min. Then, the obtained heat-treated product,
It was washed with tar medium oil (boiling range: 120 to 250 ° C.).

The heat-treated product was subjected to a secondary heat treatment in a batch type rotary calcination furnace at 480 ° C. for 3 hours under a nitrogen stream of 10 l / min to obtain a carbonaceous powder. The carbonaceous powder was crushed and classified using a jet mill and an air classifier to obtain a carbonaceous powder A having an average particle size of 3.5 μm. The average particle size of carbonaceous powder is 5 using a Coulter counter.
The measurement was performed using an aperture tube having a diameter of 0 μm. The C / H of the obtained carbonaceous powder was 2.8.

On the other hand, the manufacturing condition is that the temperature of the secondary heat treatment is 51.
A carbonaceous powder B was obtained in the same manner as the carbonaceous powder A except that the temperature was changed to 0 ° C. The obtained carbonaceous powder B had an average particle diameter of 3.4 μm and C / H of 2.39.

The carbonaceous powders A and B were uniformly dispersed in a silicone oil having a viscosity of 10 cP (centipoise) at room temperature in an amount of about 36% by weight to obtain electrorheological fluids A and B. The obtained electrorheological fluid was filled in a cell composed of parallel plate type electrode plates, and a voltage was applied to adjust the frequency to 10
The dielectric loss was measured by changing from Hz to 10 ⁷ Hz to obtain the relaxation frequencies f _0A and f _0B of the electrorheological fluids A and B, respectively. The relationship between the relaxation frequencies f _0A and f _0B was f _0A <f _0B , and log (f _0B / f _0A ) = 0.15.

Two such electrorheological fluids A and B
Various electrorheological fluids were prepared by changing the mixing ratio [wt%] of the above, and a voltage of 2 kV / mm was applied at room temperature using a double cylinder type rotational viscometer, and a shear rate of 366 / sec was applied for 5 minutes. The fluid viscosity was measured. In addition, in this viscosity measurement, a measurement value is taken every 12 seconds, a single regression line is calculated, and the deviation from the regression of each measurement point, that is, the sum of squares of deviations (σ _E ) is obtained, so that the viscosity changes with time. Variation was measured.

FIG. 1 shows the relationship between the mixing ratio of the electrorheological fluid A in the prepared electrorheological fluid and the change in viscosity and the change in viscosity. The dotted line in FIG. 1 is the viscosity change assumed from the additivity of the characteristics of the electrorheological fluids A and B.

As shown in FIG. 1, the electrorheological characteristics of the electrorheological fluid can be adjusted by changing the mixing ratio of the electrorheological fluids A and B. Further, in the present embodiment, log (f _0B / f _0A ) = 0.15 and 0 <log (f _{0 .max} / f _{0 .min} ) ≦ 0.25, so that the electroviscosity is achieved. Since good additivity is established according to the characteristics of the fluids A and B, by adjusting the mixing ratio of the electrorheological fluids A and B, an electrorheological fluid having desired viscosity characteristics can be easily realized. It is possible to achieve good electrorheological characteristics with little fluctuation in viscosity.

[Comparative Example 1] The temperature of the secondary heat treatment was 490 ° C.
A carbonaceous powder C was obtained in the same manner as the carbonaceous powder A of Example 1 except that the above was changed to. The average particle diameter of the obtained carbonaceous powder C was 3.5 μm, and C / H was 2.30.

Further, a carbonaceous powder D was obtained in the same manner as the carbonaceous powder A except that the secondary heat treatment condition was changed to 510 ° C. for 6 hours. The obtained carbonaceous powder D had an average particle diameter of 3.3 μm and C / H of 2.51.

Using the carbonaceous powders C and D, the electrorheological fluids C and D were prepared in the same manner as in Example 1.
Got Further, the respective dielectric losses were measured in the same manner to obtain the relaxation frequency f _0C of the electrorheological fluid _C and the relaxation frequency f _0D of the electrorheological fluid D. Relaxation frequencies f _0C and f
The relationship of _0D was f _0C <f _0D , and log (f _0D / f _0C ) = 0.75.

Two such electrorheological fluids C and D
Various electrorheological fluids were prepared by changing the mixing ratio of, and the change in viscosity and the change in viscosity at the time of voltage application were measured in the same manner as in Example 1.

FIG. 2 shows the relationship between the mixing ratio [wt%] of the electrorheological fluid C in the prepared electrorheological fluid and the change in viscosity and the change in viscosity. The dotted line in FIG. 2 is
It is a viscosity change assumed from the additivity due to the characteristics of the electrorheological fluids C and D.

As shown in FIG. 2, by changing the mixing ratio of the electrorheological fluids C and D, the electrorheological characteristic of the electrorheological fluid changes, but in this example, log (f _0D / f _0C ) = 0.75, and 0 <log (f _{0 .max} / f _{0 .min} ) ≤0.25 is not realized, so the additivity according to the characteristics of the electrorheological fluids C and D cannot be established. However, it has become difficult to prepare an electrorheological fluid having the required characteristics.

[Example 2] The carbonaceous powders A and B obtained in Example 1 were changed in various mixing ratios to obtain Example 1
36% by weight of carbonaceous powder in the same silicone oil
Were dispersed so as to obtain various electrorheological fluids. With respect to each of the obtained electrorheological fluids, the change in viscosity and the change in viscosity when a voltage was applied were measured in the same manner as in Example 1. As a result, also in this example, as in the case of Example 1, good additivity was established, and an electrorheological fluid having excellent characteristics with large viscosity change and small viscosity fluctuation could be prepared. It was From the above results, the effect of the present invention is clear.

[0054]

As described in detail above, according to the method for preparing an electrorheological fluid of the present invention, a plurality of kinds of electrorheological fluids having different electric characteristics are mixed, that is, a plurality of kinds of electrorheological fluids having different electric characteristics are mixed. By mixing and using the dielectric particles of, the electric characteristics of the entire dielectric particles are adjusted to obtain the desired electro-viscous characteristics, and the viscosity changes greatly and the viscosity does not change with time. A fluid can be prepared.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between a mixing ratio of one electrorheological fluid, a viscosity change, and a viscosity fluctuation in an electrorheological fluid prepared by mixing two electrorheological fluids.

FIG. 2 is a graph showing the relationship between the mixing ratio of one electrorheological fluid and the viscosity change and the viscosity fluctuation in the electrorheological fluid prepared by mixing two electrorheological fluids.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C10M 107: 50) C10N 20:06 Z 8217-4H 30:02 40:14 (72) Inventor Hara Takuka Oka 1 Kawasaki-cho, Chuo-ku, Chiba, Chiba Prefecture Technical Research Division, Kawasaki Steel Co., Ltd. (72) In Hitomi Hatano, 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Technical Research Division, Kawasaki Steel Co., Ltd. (72) Inventor Noriyoshi Fukuda No. 1 Kawasaki-cho, Chuo-ku, Chiba, Chiba Prefecture Technical Research Division, Kawasaki Steel Co., Ltd. (72) Inventor Takayuki Maruyama 3-1-1 Ogawahigashi-cho, Kodaira-shi, Tokyo (72 ) Saito Tsubasa Tsubasa Sai 3-3-1 Ogawahigashi-cho, Kodaira-shi, Tokyo (72) Inventor Takao Ogino 3-1-1 Ogawa-higashi-cho, Kodaira-shi, Tokyo

Claims (2)

[Claims] 1. An oil-based medium excellent in electrical insulation, containing a plurality of types of materials.
Electrorheological flow obtained by dispersing electric particles
A method for preparing a body, comprising using one type of each of the plurality of types of dielectric particles independently.
When preparing the viscous fluid,
Relaxation frequency f₀Of the maximum relaxation frequency f ₀._maxWhen
The minimum relaxation frequency f₀._minThe relation with the following equation is 0 <log (f₀._max/ F₀._min) Mixing electrorheological fluid and / or dielectric particles satisfying ≦ 0.25
A method for preparing an electrorheological fluid, comprising: 2. The method for preparing an electrorheological fluid according to claim 1, wherein the dielectric particles are carbonaceous powder containing carbon as a main component.