WO2022102217A1

WO2022102217A1 - Electroviscous fluid damper

Info

Publication number: WO2022102217A1
Application number: PCT/JP2021/031972
Authority: WO
Inventors: ソクチョル申; 裕一郎山本; 智弘岡田
Original assignee: 日立Astemo株式会社
Priority date: 2020-11-12
Filing date: 2021-08-31
Publication date: 2022-05-19

Abstract

[Problem] To provide: an electroviscous fluid which exhibits a satisfactory damping force and in which fluctuation is suppressed; and an electroviscous fluid damper in which the electroviscous fluid is used. [Solution] Provided are an electroviscous fluid in which polyurethane particles are dispersed in an electrically insulating medium, wherein the polyurethane particles contain at least one type of metal ion encapsulated in the particles or attached to the surface of the particles, and the metal ions include lithium ions and zinc ions at a lower quantity than the lithium ions; and an electroviscous fluid damper in which the electroviscous fluid is sealed.

Description

Electrorheological fluid damper

The present invention relates to an electrorheological fluid and an electrorheological fluid damper using the same.

An electrorheological fluid is a fluid whose apparent viscosity changes rapidly and reversibly in the presence of an applied electric field. Electrorheological fluids are roughly classified into uniform systems and particle dispersion systems, and the latter is generally dispersed in a hydrophobic and electrically non-conductive oil (dispersion medium) in which finely divided solids (particles, etc.) are dispersed. Has a body aspect. When an electrorheological fluid is exposed to an electric field, its flow resistance changes and generally becomes highly viscous, and when the electric field is removed, it returns to a normal liquid state. The electrorheological fluid is characterized in that the current density of the leakage current is small and the power consumption is small when a voltage is applied, and can be advantageously used in applications such as dampers in which it is desirable to control the transmission of force by a low power level.

The characteristics required for the electrorheological fluid mainly include damping force and responsiveness, and in addition to these, there are a plurality of characteristics including heat resistance, current density, damping force fluctuation characteristics, and the like. In electrorheological fluids, it is desired that these characteristics are balanced within their respective permissible ranges and that the overall effect is excellent. In particular, in consideration of braking force (damping force), power consumption, etc., an electrorheological fluid having a high maximum shear stress and a low current density is desired.

Patent Document 1 describes 1 selected from the group consisting of Al, Si, Ti, V, Cr, Mn, Fe, Co, Ga, Ge, Zr, In, Sn, and Hf in order to improve the induced shear stress. An electrically viscous fluid in which a zinc oxide powder containing a seed or two or more kinds of doped metal elements is dispersed in an electrically insulating oily medium is disclosed. However, this document does not disclose the Li—Zn mixed system containing Li as a doped metal element, and the dispersion (powder) in the medium disclosed in the same document is zinc oxide powder. Resin particles, especially polyurethane particles, are not disclosed.
Further, as an example of a system using particles doped with metal ions, Non-Patent Document 1 discloses that the Li ion concentration is 0.00306 mol / kg and the Zn ion concentration is 0.00614 mol / kg, which are dispersed in silicone oil. An electrically viscous fluid consisting of doped polyurethane particles is disclosed. However, this document does not disclose an electrorheological fluid using polyurethane particles whose doped Li ion concentration exceeds the Zn ion concentration.

Japanese Unexamined Patent Publication No. 10-36871

An electrically viscous fluid using polyurethane particles having a Zn ion concentration higher than the Li ion concentration disclosed in Non-Patent Document 1 cannot exhibit a sufficient damping force, and when this is applied to a damper, the damper is damped. The force cannot be kept constant. When the electrorheological fluid cannot sufficiently exert its damping force in the damper, a "fluctuation" phenomenon occurs in which the damping force fluctuates. This "fluctuation" phenomenon can be confirmed from the Lissajous waveform of the stroke (piston displacement) and damping force in the damper test.

An object of the present invention is to provide an electrorheological fluid that exhibits a sufficient damping force and suppresses a fluctuation phenomenon, and an electrorheological fluid damper using the electrorheological fluid.

One aspect of the present invention is an electrically viscous fluid in which polyurethane particles are dispersed in an electrically insulating medium, wherein the polyurethane particles are contained in the particles or adhered to the surface of the particles. It contains metal ions, and the metal ions are characterized by containing lithium ions and zinc ions in a smaller amount than the lithium ions.
In the electrorheological fluid of the present invention, the lithium ion is in the range of 0.001 to 0.006 mol / kg with respect to the polyurethane particles, and the zinc ion is in the range of 0.00004 to 0.0004 mol / kg. Can be done. Further, the polyurethane particles can be a reaction product of a mixture containing polyols, isocyanates and an emulsifier having an alkoxy group.
The present invention also relates to an electrorheological fluid damper having a piston, a cylinder in which the piston is housed, and the electrorheological fluid enclosed in the cylinder.

According to the present invention, it is possible to provide an electrorheological fluid that exhibits a sufficient damping force and suppresses a fluctuation phenomenon, and an electrorheological fluid damper using the electrorheological fluid.

FIG. 1 is a diagram showing an example of a flow chart of an electrorheological fluid synthesis process according to the present invention. FIG. 2 is a schematic diagram illustrating the structure of the electrorheological fluid damper according to the embodiment of the present invention. FIG. 3 is a diagram showing the relationship between the amount of lithium ions in the electrorheological fluid used for the electrorheological fluid damper and the standard deviation of the damping force when a voltage of 5 kV is applied to the damper. FIG. 4 is a diagram showing the relationship between the amount of lithium ions in the electrorheological fluid used for the electrorheological fluid damper and the current value when a voltage of 5 kV is applied to the damper. FIG. 5 is a diagram showing the relationship between the amount of zinc ions in the electrorheological fluid and the polyurethane particle size. FIG. 6 is a diagram showing the relationship between the amount of zinc ions in the electrorheological fluid and the rate of increase in viscosity of the electrorheological fluid after heat loading. FIG. 7 is a diagram showing Lissajous waveforms before and after the fluctuation improvement (comparative example) and after the improvement (example) using the actual damper. FIG. 8 is a diagram showing the relationship between the current value at 45 ° C. and the current value at 65 ° C. when a voltage of 5 kV is applied to the electrorheological fluid damper. FIG. 9 is a diagram showing a Lissajous waveform at 80 ° C. when a voltage of 5 kV is applied to an electrorheological fluid damper. FIG. 10 is a diagram showing the time variation of the damping force and the current value observed when the fluctuation of the damper damping force occurs. FIG. 11 is a schematic diagram showing the mechanism of the electrorheological fluid (ER) effect when a voltage is applied to the damper. FIG. 12 is a diagram showing a schematic diagram in which a capacitor is introduced into an electric circuit of an electrorheological fluid damper. FIG. 13 is a diagram showing a resage waveform using an actual damper, and as a result of using (a) an electrorheological fluid containing an emulsifier for improving redispersibility, (b) electricity without an emulsifier for improving redispersibility. It is a figure which shows the result using the viscous fluid respectively. FIG. 14 is a diagram showing the standard deviation of the damping force. As a result of using (a) an electrorheological fluid containing an emulsifier for improving redispersibility, (b) an electrorheological fluid not containing an emulsifier for improving redispersibility was used. It is a figure which shows each of the results used. FIG. 15 is a diagram showing measured values of current densities at measured temperatures: 10 ° C, 30 ° C, 50 ° C, and 80 ° C when a voltage of 5 kV is applied to an electrorheological fluid damper according to the amount of lithium ions.

The electrorheological fluid of the present invention has an embodiment in which polyurethane particles containing specific metal ions are dispersed in an electrically insulating medium.
In order to solve the above-mentioned problem, that is, the problem of generation of fluctuation phenomenon due to insufficient development of damping force, the present inventions are in the process of doping the polyurethane particles in an electrorheological fluid containing the polyurethane particles as a dispersoid. The polarizability of the polyurethane particles was increased by controlling the amount of metal ions and improving the mobility of the ions. Then, they have found that by using the polyurethane particles in an electrorheological fluid, the damping force of the damper using the polyurethane particles can be strengthened, and as a result, the fluctuation of the damper damping force can be reduced. In detail, the inventors have found that the fluctuation reduction can be achieved by adjusting the amount of lithium ions having high ion mobility in the polyurethane particles in the electrorheological fluid to a state higher than the amount of zinc ions.
In addition, the present inventors use modified silicone containing an alkoxy group such as a methoxy group or an ethoxy group as an emulsifier in the production of an electrorheological fluid containing polyurethane particles as a dispersoid, whereby the alkoxy group is used. During the hydrolysis reaction, the water contained as an impurity in the raw material of the electrorheological fluid is consumed, so that the water content can be removed from the reaction system, that is, the electrorheological fluid in which the content of water content is suppressed can be obtained. And, it was found that in the obtained electrorheological fluid, in addition to the improvement of durability, the decrease of the current density at the time of applying a voltage can be achieved.
Hereinafter, each component of the electrorheological fluid according to the present invention and an electrorheological fluid damper in which the electrorheological fluid is enclosed will be described in detail.

[Electrical insulation medium]
Examples of the electrically insulating medium used in the present invention include paraffins (eg n-nonene), olefins (eg l-nonene, (cis, trans) -4-nonene) and aromatic hydrocarbons (eg xylene). Liquid hydrocarbons such as: Polydimethylsiloxane having a viscosity of 3 mPa · s to 300 mPa · s, silicone oil such as liquid methylphenylsiloxane, and the like. Silicone oil is used as the preferred electrically insulating medium. The electrically insulating medium can be used alone or in combination with other electrically insulating media. The freezing point of the electrically insulating medium is preferably less than −30 ° C., and the boiling point is preferably 150 ° C. or higher.

[Polyurethane particles]
The polyurethane particles according to the present invention contain at least one kind of metal ion described later, which is encapsulated in the form of a molecule or an ion or adheres to the surface of the particle.
In a preferred embodiment, the polyurethane particles according to the present invention are reaction products of a mixture containing polyols, isocyanates, and an emulsifier having an alkoxy group.
The amount of the polyurethane particles contained in the electrorheological fluid can be, for example, 30% by mass to 70% by mass based on the total mass of the electrorheological fluid.

<Polyols>
Examples of the polyols include polyether polyols, polyester polyols, polymer polyols and the like.
Examples of the polyether polyols include ethylene glycol, diethylene glycol, propylene glycol, 1,4-butylene glycol, dihydroxydiphenylpropane, glycerin, hexanetriol, trimethylolpropane, pentaerythritol, sorbitol, sucrose, dipropylene glycol and dihydroxy. Diphenylmethane, dihydroxydiphenyl ether, dihydroxybiphenyl, hydroquinone, resorcin, naphthalene diol, aminophenol, aminonaphthol, phenol formaldehyde condensate, fluoroglucolcin, methyldiethanolamine, ethyldiisopropanolamine, triethanolamine, ethylenediamine, hexamethylenediamine, bis (p- Examples thereof include polyether polyols obtained by adding one or more of ethylene oxide, propylene oxide, butylene oxide, styrene oxide and the like to aminocyclohexane), tolylene diamine, diphenylmethanediamine, naphthalene diamine and the like.
Examples of the polyester polyols include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, trimethylene glycol, 1,3- or 1,4-butylene glycol, neopentyl glycol, 1,6-hexamethylene glycol, and deca. Polyhydric alcohols such as methylene glycol, bisphenol A, bisphenol F, p-xylylene glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, glycerin, trimethylolpropane, hexanetriol, pentaerythlit, etc. One or two of polyvalent carboxylic acids such as malonic acid, maleic acid, succinic acid, adipic acid, glutaric acid, pimelli acid, sebacic acid, oxalic acid, phthalic acid, isophthalic acid, terephthalic acid, hexahydrophthalic acid, etc. Examples thereof include a polyester polyol which is a condensate of the above, or a polyester polyol obtained by ring-opening polymerization of a cyclic ester such as propiolactone, butyrolactone, and caprolactone. Further, polyester polyols produced from the above-mentioned polyols and cyclic esters, polyester polyols produced from the above-mentioned polyols, dibasic acids, and three types of cyclic esters can also be mentioned.
Examples of the polymer polyols include 1,2-polybutadiene polyol, 1,4-polybutadiene polyol, polychloroprene polyol, butadiene-acrylonitrile copolymer polyol, polydimethylsiloxane dicarbinol, polytetramethylene ether glycol and Himashi. Examples thereof include a ricinol acid ester such as oil, a polymer polyol obtained by graft-polymerizing an ethylenically unsaturated compound such as acrylonitrile, styrene, and methyl methacrylate with the polyether polyol or the polyester polyol.
Among these, polyether polyols are preferable.

<Isocyanates>
Examples of the isocyanates include toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI), diphenylmethane diisocyanate (MDI), polymethylene polyphenyl polyisocyanate (p-MDI), isophorone diisocyanate (IPDI), methyl isocyanate and the like. ..

For the above-mentioned polyols and isocyanates, the molar ratio [(NCO group) / (OH group)] of the hydroxy group (OH group) of the polyols and the isocyanate group (NCO group) of the isocyanates is 1 to 1.5. It is desirable to use it for.
By using a slightly excessive amount of isocyanates as a curing agent as compared with polyols, the water content in the reaction system is consumed by the reaction between the isocyanate groups of the curing agent and water, and it has an alkoxy group described later. In addition to the water removing effect of the emulsifier, the water removing effect from the electroviscous fluid can be enhanced.

<Emulsifier with alkoxy group>
The emulsifier (surfactant) having an alkoxy group is not particularly limited, and for example, a polysiloxane having an alkoxy group at the side chain and / or the terminal may be mentioned because of its affinity with silicone oil as an electrically insulating medium. Can be done.
As an example, polysiloxane represented by the following formula can be mentioned.

In the above formula, A represents an aminoalkyl group, for example, an aminoethyl group (-(CH ₂ ) ₂ NH ₂ ), an aminopropyl group (-(CH ₂ ) ₃ NH ₂ ), an aminoethyl aminopropyl group (-(CH)). ₂ ) ₃ NH (CH ₂ ) ₂ NH ₂ ) etc.
B represents an alkoxy group, for example, a methoxy group (CH _3O− ), an ethoxy group ₍ C2H _5O− ), or the like.

Examples of commercially available emulsifiers (surfactants) having an alkoxy group include reactive silicone oils manufactured by Shin-Etsu Silicone Co., Ltd. (trade names: KF-857, KF-8001, KF-862, KF-858) and the like. However, it is not limited to these.
The emulsifier having an alkoxy group may be used alone or in combination of two or more.
The emulsifier having an alkoxy group is preferably blended in a proportion of 1 to 2% by mass with respect to the mass of the above-mentioned electrically insulating medium. By setting the blending amount of the emulsifier having an alkoxy group to 1% by mass or more with respect to the mass of the electrorheological insulating medium, a sufficient dispersed state is ensured, and by setting it to 2% by mass or less, the particle size of the polyurethane particles is in a suitable range. The characteristics of the electrorheological fluid can be made suitable.

<Other emulsifiers>
Further, in the present invention, other emulsifiers other than the above-mentioned emulsifier having an alkoxy group may be used in combination as long as the effect of the present invention is not impaired.
Other emulsifiers include surfactants that are soluble in the electrical insulating medium and derived from, for example, amines, imidazolines, oxazolines, alcohols, glycols or sorbitol.
Polymers soluble in the electrical insulating medium can also be used, for example having a N (nitrogen atom) and / or OH (hydroxy group) content of 0.1-10% by weight and 25-83% by weight. Examples thereof include polymers containing% C _4-24 alkyl groups and having a weight average molecular weight of 5,000 to 1,000,000. Examples of the N and OH functional compounds in these polymers include amines, amides, imides, nitrilos, 5- to 6-membered N-containing heterocycles or alcohols, and C _4-24 alkyl esters of acrylic acid or methacrylic acid. be able to. Examples of the N and OH functional compounds are N, N-dimethylaminoethyl methacrylate, tert-butylacrylamide, maleic acidimide, acrylonitrile, N-vinylpyrrolidone, vinylpyridine, 2-hydroxyethylmethacrylate and the like. The polymer emulsifiers described above have the advantage that the systems prepared using them are generally more stable with respect to sedimentation dynamics compared to low molecular weight surfactants.
Modified silicone oils such as amino-modified silicone and fluorine-modified silicone can also be used.

<Metal ions>
The polyurethane particles according to the present invention contain metal ions in the particles. The inclusion of the metal ion may mean that the metal ion is dissolved or dispersed in the particle or is in a non-dispersed state (unevenly distributed), that is, in a form enclosed in the particle, or the particle surface. It may be an aspect attached to. In the electrorheological fluid of the present invention, metal ions dissolved or dispersed in the electrorheological insulating medium or in a non-dispersed (unevenly distributed) state may be present.
Examples of the metal ion include ions of metal elements such as lithium, zinc, chromium, copper, nickel, cobalt, iron, manganese, and tungsten, and in the present invention, lithium ion and zinc ion are essentially contained. do.
The present invention is characterized in that the amount of lithium ions is larger than that of zinc ions, for example, the lithium ions are in the range of 0.001 to 0.006 mol / kg in an electroviscous fluid, or 0. It is preferably in the range of .003 to 0.006 mol / kg or 0.001 to 0.003 mol / kg, and the zinc ion is preferably used in the range of 0.00004 to 0.0004 mol / kg. Is.
By setting the amount of lithium ions in the above range, it can be expected that the damping force of the obtained electrorheological fluid is enhanced, the generation of fluctuations is suppressed, and at the same time, the current value at the time of applying a voltage is suppressed within an allowable range.
Further, by setting the amount of zinc ions in the above range, the particle size of the polyurethane particles can be controlled, and it can be expected that the increase in viscosity can be suppressed even after the heat load of the electrorheological fluid. When zinc ions are not used, the particle size of the polyurethane particles may increase beyond a desired range (for example, 10 μm), and as a result, the contact area between the particles may decrease and the electrorheological effect may decrease.

In the present invention, only the emulsifier having the alkoxy group is used as the emulsifier, no other emulsifier is used, the lithium ion amount is in the range of 0.001 to 0.003 mol / kg, and the zinc ion amount is 0. When the range is in the range of 0.0004 to 0.0004 mol / kg, it can be expected that the damping force is increased in the obtained electroviscous fluid to suppress the occurrence of fluctuations, and at the same time, the current value when a voltage is applied is suppressed to an allowable range.
The other emulsifiers, particularly the above-mentioned polymer emulsifiers and modified silicone oils such as amino-modified silicones or fluorine-modified silicones, have the advantage that the systems prepared using them as described above are more stable with respect to sedimentation dynamics. This is because by preparing the polyurethane particles using the emulsifier, long molecular chains derived from the emulsifier are present on the surface of the obtained polyurethane particles, whereby the polyurethane particles are easily separated from each other. (Aggregation is suppressed). Therefore, these emulsifiers can be classified as emulsifiers for improving redispersibility. However, the presence of long molecular chains due to this emulsifier for improving redispersibility reduces the frictional force between the polyurethane particles and may be a factor that reduces the electrorheological effect.
On the other hand, the emulsifier having an alkoxy group has a large emulsifying ability and can impart a molecular chain having an appropriate length to the surface of the polyurethane particles. For example, a polysiloxane having an alkoxy group represented by the above formula as an emulsifying agent having an alkoxy group has an alkoxy group at both ends and an alkylamino group (NH ₂ R-) in the side chain. As the alkylamino group, an emulsifier having an alkoxy group to which a monoamino group having a relatively short chain length such as an aminoethyl group is bonded has good adhesion to polyurethane particles and improves dispersibility of polyurethane particles. , Does not excessively deprive particles of frictional force. Therefore, even without using an emulsifier for improving redispersibility, it is possible to achieve both the electrorheological viscosity effect and the improvement of redispersibility even in a range where the amount of ions is relatively small.

〔lubricant〕
Further, a lubricant may be further added to the electrorheological fluid of the present invention.
Examples of the lubricant include polydimethylsiloxane, polytrifluoropropylmethylsiloxane, and oil-based lubricants such as a copolymer of dimethylsiloxane and trifluoropropylmethylsiloxane.
When a lubricating oil is used, it can be blended in the electrorheological fluid in a proportion of 1% by mass to 2% by mass with respect to the electrorheological fluid.

<Particle diameter of polyurethane particles>
The polyurethane particles according to the present invention can be particles having an average particle diameter of, for example, about 2 μm to 5 μm. By setting the particle size of the polyurethane particles within the above numerical range, it can be expected that both the electrorheological effect and the dispersibility can be achieved, and that sedimentation and deterioration of redispersibility can be prevented.

<Manufacturing method of electrorheological fluid>
The electroviscosity fluid of the present invention disperses and emulsifies a mixture containing, for example, the above-mentioned electrically insulating medium, polyols, metal ions, emulsifiers, and optionally other additives (lubricant, catalyst for polyurethane synthesis, etc.), and is used therein. It can be produced by adding isocyanates as a curing agent.
Hereinafter, an example of the method for preparing the electrorheological fluid of the present invention will be described with reference to the manufacturing flowchart (outline) shown in FIG.

1. 1. Weighing and dissolution step This step is a step of separately preparing a solution containing polyols and metal ions (electrolyte-containing polyol solution) and a solution containing an electrically insulating medium and an emulsifier (electrically insulating medium-containing solution). ..
The prepared electrolyte-containing polyol solution and electrically insulating medium-containing solution are individually stored at room temperature and mixed in the next step (emulsification).
The preparation of each solution is described below.

1-1. Preparation of electrolyte-containing polyol solution Weigh the polyols and metal ions, add them to a compounding bottle (such as a bottle with a stopper) or a glass beaker / flask of an appropriate size, and add them to a magnetic stirrer and a magnetic stirrer, or a stirrer such as a homogenizer. Is used to mix and dissolve each material by heating and stirring.

An example of a specific operation procedure is shown below. The following operations can be performed in the glove box as needed.
First, the polyols are weighed in a bottle with a stopper.
The metal ion can be prepared as a salt of the above metal element, for example, a halide, preferably as a chloride, and in the present invention, lithium chloride and zinc chloride can be preferably used as a source of lithium ion and zinc ion.
Therefore, lithium chloride and zinc chloride are preferably weighed, and if used, a synthetic catalyst for polyurethane is weighed. Since salts of metal elements have deliquescent properties depending on the type, care must be taken when handling them.
Next, the polyols are heated and stirred to, for example, 50 ° C. to 80 ° C., and after confirming that the desired temperature has been reached, salts of metal elements are sequentially added thereto. Specifically, first, lithium chloride is added to the polyols. While maintaining the desired temperature, lithium chloride is mixed and stirred, and the mixture is stirred and dissolved until no undissolved matter or precipitate can be visually confirmed from the appearance. Next, zinc chloride is added, and the mixture is mixed and stirred while maintaining the desired temperature, and the mixture is stirred and dissolved until no undissolved matter or precipitate can be visually confirmed from the appearance. When a synthetic catalyst for polyurethane is used, it is added after the salt of the metal element is dissolved, and the mixture is mixed and stirred while maintaining the desired temperature to obtain an electrolyte-containing polyol solution.
The stirring time can be appropriately set until no undissolved substance or precipitate is confirmed in the electrolyte and each component is dissolved or dispersed, and can be, for example, 8 hours or more in total.

As shown in the specific operating procedure, since at least two kinds of salts of metal elements are used as sources of metal ions, it is preferable to dissolve them step by step. That is, it is preferable to perform an operation such as adding a salt of one kind of metal element and completely dissolving it, and then adding a salt of the next one kind of metal element and completely dissolving it.
In the present invention, lithium ions are present in a larger amount than zinc ions, and in a preferred embodiment, the lithium ions are in the range of 0.001 to 0.006 mol / kg in the electrically viscous fluid. The amount of the salt of the above-mentioned metal element can be adjusted so that the zinc ion is in the range of 0.00004 to 0.0004 mol / kg.

When a polyurethane synthesis catalyst is used, it is preferably added into the system after the metal ions (that is, salts of metal elements) are completely dissolved, as shown in the above specific operating procedure.
Examples of the catalyst include amine-based catalysts, and specific examples thereof include triethylamine, benzyldiethylamine, 1,4-diazabicyclo [2,2,2] octane, and 1,8-diazabicyclo [5,4,0]. Examples thereof include undecene, N, N, N', N'-tetramethyl-1,3-butanediamine, N-ethylmorpholine and the like. When the catalyst is used, it can be blended in a proportion of up to about 0.2% by mass with respect to the amount of polyurethane finally obtained. However, if a large amount is added, a decomposition reaction may occur due to the catalyst, so caution is required.

1-2. Preparation of solution containing electrically insulating medium Weigh the electrically insulating medium, the emulsifier having an alkoxy group (emulsifier 1), and if desired, the other emulsifier (emulsifier 2), and if desired, weigh the lubricant. Add to a glass beaker / flask of appropriate size (such as a bottle) or, if necessary, mix each material at room temperature using a magnetic stirrer and a stirrer such as a magnetic stirrer or a homogenizer.

An example of a specific operation procedure is shown below.
First, an electrically insulating medium (silicone oil, etc.) is weighed in a bottle with a stopper. On the other hand, an emulsifier having an alkoxy group (emulsifier 1), another emulsifier (emulsifier 2) if desired, and a lubricant if desired are weighed, and these emulsifiers / lubricants are added / mixed to the electrically insulating medium to be added / mixed to the electrically insulating medium. Obtain the containing solution.
It is preferable to add the emulsifier having an alkoxy group (emulsifier 1) in an amount of 1% by mass to 2.0% by mass with respect to the amount of the electrically insulating medium used.
In the above mixing and dissolution, the temperature at the time of stirring can be set to room temperature (20 ± 10 ° C.).

2. 2. Synthesis preparation step This step will be described later in 4. Temporary curing process and 5. This is a step of preparing a curing agent used in the main curing step, that is, isocyanates.
The above-mentioned isocyanates as a curing agent can be used in combination of two or more, and for example, toluene diisocyanate (TDI) and polymethylene polyphenyl polyisocyanate (p-MDI) can be used in combination.
When the isocyanates are weighed in a bottle with a stopper and two or more kinds of isocyanates are used, another kind of isocyanates can be added thereto to prepare a mixed solution.
The weighing and prepared curing agents (isocyanates) will be described later in 4. Temporary curing process and 5. Since it is used separately in the main curing step in two steps, for example, 4. A 10% to 20% amount can be set aside in advance for use in the temporary curing step.
Since the curing agent (isocyanate) is designated as a specific chemical substance depending on its type, it should be operated under sufficient ventilation, and since it is a highly reactive substance, the equipment used is isocyanate. It is desirable to neutralize with a neutralizing solution (eg, a mixed solution of a 5% sodium carbonate aqueous solution and a neutral detergent), and then use the mixture for washing.

3. 3. Emulsification process This process is described in 1. above. The electrolyte-containing polyol solution and the electrically insulating medium-containing solution obtained in the preparation step of the above are dispersed and mixed by a stirrer such as a homogenizer or a disperser to obtain an electrolyte-containing polyol solution / an electrically insulating medium-containing solution mixture, and then the mixture is obtained. Is an emulsion (emulsion solution) in which a polyol is dispersed in an electrically insulating medium. The average particle size of the polyurethane particles formed in the subsequent process is adjusted according to the type of agitator and disperser used in this process, the type of shear blades in the disperser, the number of rotations (speed), and the stirring (rotation) time. can do.

An example of a specific operation procedure is shown below.
First, 1-1. The electrolyte-containing polyol solution obtained in the step is weighed in a flask, and here, 1-2. The solution containing the electrically insulating medium obtained in the step is weighed and added.
The flask is set in a constant temperature device such as a water bath, and the mixture is stirred and mixed with a homogenizer to obtain an emulsion.
In the above stirring and mixing, the rotation speed at the time of stirring can be about 10,000 rpm to 20,000 rpm, the temperature at the time of stirring can be, for example, about 40 ° C., and the stirring time can be about 0.5 hours. Yes, but not limited to these conditions.

4. Temporary curing (hardener addition (1)) step This step is described in 3. above. This is a step of curing the emulsion (uncured emulsion particles) produced in the emulsification step to obtain semi-cured polyurethane particles. In this step, about 10% to 20% of the total amount of the curing agent (isocyanates) used to form the polyurethane particles is used.

An example of a specific operation procedure is shown below.
Above 3. In the emulsion prepared in the emulsification step, for example, the above 3. While continuing the same stirring as in the step (eg, stirring / mixing with a homogenizer), a curing agent (isocyanate) in an amount of about 10% to 20% of the total addition amount is added dropwise using a tube pump or the like.
When adding the above-mentioned curing agent, the emulsion is set in a constant temperature device such as a mantle heater so that the temperature becomes a predetermined temperature (for example, 50 ° C. or higher), stirring is continued, and after reaching the predetermined temperature, the curing agent (partly). ) Can be added. The stirring time can be about 0.5 hours, but is not limited to such addition / stirring conditions. At the initial stage of adding the curing agent, several drops can be dropped (about 5 times) in order to confirm that the stirring does not stop.

5. Main curing (hardener addition (2)) step This step is described in 4. above. This is a step of further curing the semi-cured polyurethane particles (emulsion particles) formed by the temporary curing step. In this step, of the total amount of the curing agent (isocyanates) used for forming the polyurethane particles, the remaining amount of the one consumed in the previous step, that is, 80% to 90% of the total amount is used.

An example of a specific operation procedure is shown below.
4. above. After the operation of the temporary curing step is completed, the remaining amount of the curing agent (isocyanates) is applied to the emulsion of the semi-cured polyurethane particles stored in the container (flask, etc.) in a stirred state while stirring is continued. That is, 80% to 90% of the total amount is added dropwise using a tube pump or the like.
When the remaining curing agent is added, the semi-cured emulsion is adjusted to a predetermined temperature (for example, 80 ° C. or lower) and stirring is continued in order to prevent an excessive temperature rise due to the reaction heat (isocyanate reaction). After reaching a predetermined temperature, the remaining curing agent can be added. The stirring time can be about 1.0 hour, but is not limited to such addition / stirring conditions. After the addition and stirring, the liquid temperature drops to about 70 ° C., and then the stirring device (homogenizer or the like) is stopped to obtain a fluid that can be said to be a crude product.

6. Filtration process 5. After the operation of this curing step is completed, the obtained fluid is filtered to obtain an electrorheological fluid. Here, in order to prevent scattering to the inner wall of the container and remove dry debris and impurities, filtration treatment may be performed in two steps.

[Electrorheological fluid damper]
The present invention also covers an electrorheological fluid damper having a piston, a cylinder in which the piston is housed, and the above-mentioned electrorheological fluid which is enclosed in the cylinder and whose viscosity is changed by applying a voltage.
Hereinafter, preferred embodiments of the electrorheological fluid damper according to the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the following embodiments are not intended to limit the electrorheological fluid damper targeted by the present invention.

The electrorheological fluid damper is a damping force adjusting shock absorber that uses an electrorheological fluid as a working fluid.
FIG. 2 is a sectional view taken along a plane including an axis of the electrorheological fluid damper 11 of the preferred embodiment of the present invention.
Referring to FIG. 2, the electrorheological fluid damper 11 has an inner cylinder 12 (cylinder), an outer cylinder 13, and an intermediate cylinder 14. For convenience, the vertical direction in FIG. 2 is the vertical direction in the electrorheological fluid damper 11.

The lower end of the outer cylinder 13 is closed by the bottom cap 15. The lower end of the inner cylinder 12 is fitted to the valve body 17 of the bottom valve 16, and the upper end is fitted to the rod guide 18. An annular reservoir chamber 19 is formed between the inner cylinder 12 and the outer cylinder 13. The electrorheological fluid and gas according to the present invention are sealed in the reservoir chamber 19. The gas in the reservoir chamber 19 is, for example, nitrogen gas or air.

A piston 20 is slidably provided inside the inner cylinder 12. The lower end of the piston rod 23 is connected to the piston 20. The upper end of the piston rod 23 extends to the outside of the outer cylinder 13 via the rod guide 18. The piston 20 divides the inside of the inner cylinder 12 into two chambers, a cylinder upper chamber 21 and a cylinder lower chamber 22. The piston 20 is provided with a contraction-side passage 24 and an extension-side passage 25 for communicating the cylinder upper chamber 21 and the cylinder lower chamber 22.

Here, the electrorheological fluid damper 11 has a uniflow structure, and as an example, a double-cylinder uniflow structure is shown. The electrorheological fluid damper may have a biflow structure or a single cylinder type, but the case where the electrorheological fluid damper 11 has a uniflow structure will be described below with reference to FIG.
That is, the electrorheological fluid damper 11 transfers the electrorheological fluid from the cylinder upper chamber 21 through the passage 26 provided in the inner cylinder 12 in both the contraction stroke and the expansion stroke of the piston rod 23. It is circulated to the annular flow path 27 formed between the intermediate cylinder 14 and the intermediate cylinder 14. In order to form the uniflow structure, a contraction-side check valve 28 is provided on the upper end surface of the piston 20, and a disc valve 32 is provided on the lower end surface of the piston 20.

The contraction-side check valve 28 opens during the contraction stroke of the piston rod 23, and allows the flow of electrorheological fluid from the cylinder lower chamber 22 to the cylinder upper chamber 21 via the contraction-side passage 24. On the other hand, the disc valve 32 opens when the pressure in the cylinder upper chamber 21 reaches a predetermined pressure during the extension stroke of the piston rod 23, and the pressure in the cylinder upper chamber 21 is applied to the extension side passage 25. Relieve to the cylinder lower chamber 22 through.

Referring to FIG. 2, the valve body 17 separates the reservoir chamber 19 and the cylinder lower chamber 22. An annular holding member 29 is fitted to the outer periphery of the inner cylinder 12 fitted to the small diameter portion of the valve body 17. The holding member 29 positions the lower end portion of the intermediate cylinder 14 in the axial direction (vertical direction) and the radial direction. The holding member 29 is made of an electrically insulating material and electrically insulates the inner cylinder 12, the bottom cap 15, and the valve body 17 from the intermediate cylinder 14. The holding member 29 is formed with a passage 30 for communicating an annular flow path 27 formed between the inner cylinder 12 and the intermediate cylinder 14 to the reservoir chamber 19.

Further, the check valve 33 opens during the extension stroke of the piston rod 23, and allows the flow of the electrorheological fluid from the reservoir chamber 19 to the cylinder lower chamber 22 via the extension side passage 34. On the other hand, the disc valve (relief valve) 35 opens when the pressure in the cylinder lower chamber 22 reaches a predetermined pressure during the contraction stroke of the piston rod 23, and the pressure in the cylinder lower chamber 22 is contracted. Relief to the reservoir chamber 19 via the side passage 36.

On the other hand, the intermediate cylinder 14 is made of a conductive material. The upper end portion of the intermediate cylinder 14 is radially positioned by the rod guide 18 via the holding member 31 fitted to the outer peripheral surface of the upper end portion of the inner cylinder 12. The holding member 31 is made of an electrically insulating material and electrically insulates the intermediate cylinder 14 from the inner cylinder 12. Further, the intermediate cylinder 14 is connected to the positive electrode of the battery (not shown) via a high voltage driver (voltage generation unit, not shown). That is, the intermediate cylinder 14 constitutes a positive electrode (electrode) that applies an electric field (voltage) to the electrorheological fluid flowing in the flow path 27. On the other hand, the inner cylinder 12 used as the negative electrode (ground electrode) is connected to the ground via the valve body 17, the bottom cap 15, the outer cylinder 13, and the high voltage driver 10.

In FIG. 2, the intermediate cylinder 14 is provided with an electrode connection portion with a positive electrode, and the inner cylinder 12 is provided with a first ground connection portion with a negative electrode (ground electrode). A first ground connection portion with the electrode (ground electrode) may be provided, and the inner cylinder 12 may be provided with an electrode connection portion with the positive electrode. Similarly, the electrode connection portion with the positive electrode is the inner cylinder 12 and the outer cylinder. It may be provided in 13.

On the other hand, when comparing the flow path cross-sectional areas between the inner cylinder 12 and the intermediate cylinder 14 and between the intermediate cylinder 14 and the outer cylinder 13, the damping force generated when a voltage is applied to the electrorheological fluid is between the electrodes. Since it is determined by the amount of electrorheological fluid (cross-sectional area), it is better to provide the electrodes so that the voltage is applied between the inner cylinder 12 and the intermediate cylinder 14, because the cross-sectional area between the electrodes is smaller, the applied voltage is smaller, and by extension, more. The same damping force (braking force) can be obtained with a small current consumption. Further, even if the energization amount increases due to an increase in the liquid temperature, the energization amount is suppressed to be smaller, the load applied to the power supply is suppressed to be smaller, and the power supply is prevented from being overloaded. be able to. Further, the ground may be ground, a frame ground, a signal ground, or the like. Finally, the current from the positive electrode may be connected to the reference potential point.

According to the present invention, in an electroviscoud fluid containing polyurethane particles, the amount of metal ions doped in the particles is controlled, specifically, lithium ions and zinc ions in a smaller amount than the lithium ions are contained or adhered to the particle surface. By adopting the above-mentioned polyurethane particles, it is possible to increase the polarization rate of the particles and realize a strong damping force in an electroviscous fluid using the particles. Then, the damping force in the electrorheological fluid using the fluid can be increased, and the fluctuation of the damping force generated in the conventional damper can be reduced.
In a preferred embodiment, in the present invention, by adopting a reaction product of a mixture containing polyols, isocyanates and an emulsifier containing an alkoxy group as polyurethane particles, the amount of water present as impurities in the reaction system is reduced, for example. The water content can be reduced from the order of more than 1,000 ppm to the level of several hundred ppm to several tens of ppm. This leads to the suppression of side reactions between the residual water remaining in the system and the isoialates, and the efficient progress of the curing reaction of the polyurethane improves the degree of curing of the polyurethane, resulting in the durability of the electrorheological fluid. This leads to improved properties (heat resistance). Deterioration of heat resistance in an electrorheological fluid can lead to an accelerated decrease in damping force, and can also affect the viscosity and current value, so it can be said to be one of the important solutions. Further, the reduction of the water content can lead to the suppression of the amount of current flowing in the electrorheological fluid when a voltage is applied to the electrorheological fluid, and particularly in the case of the present invention, it also suppresses the increase in the amount of current that can occur due to the increase in lithium ions. It can be expected to connect and reduce energy consumption. By using the electrorheological fluid having a reduced amount of water, the electrorheological fluid damper of the present invention can suppress an increase in the amount of current even when the operating temperature rises, and the damper can be operated in a higher temperature range. Become.

In the analysis of the cause of the fluctuation of the damper damping force, the present inventors have found that the current flowing when a voltage is applied between the electrodes changes with the movement of the piston of the damper in conjunction with the fluctuation of the damper damping force. It was confirmed.
FIG. 10 shows the time variation of the damping force and the current value observed when the fluctuation of the damper damping force occurs. As shown in FIG. 10, it can be confirmed that the current value increases several milliseconds after the damping force decreases, and then the damping force recovers.
As shown in FIG. 11, this phenomenon is caused by the column of polyurethane particles (polarizing particles) formed when the damping force is high (FIG. 11 (a)) collapses when the damping force decreases (FIG. 11 (b)). ), After that, it seems that this is a phenomenon that reflects the fact that the column was regenerated when the damping force was restored (FIG. 11 (c)). That is, it is considered that a so-called inrush current flows through the electrode in order to repolarize the polyurethane particles after the column collapse, and this is observed as an increase in the current value. This inrush current has a problem of raising the upper limit of the power supply capacity, so countermeasures are required.
As a countermeasure against inrush current, for example, as shown in FIG. 12 (1), a resistor is inserted in series between the power supply and the electrodes, and a capacitor is connected in parallel between the electrodes to connect the column shown in FIG. 11 (b). Although a current flows as shown in FIG. 12 (2) at the time of collapse, the magnitude of the inrush current can be reduced.
Further, as shown in the present invention, the electrorheological fluid is a fluid in which the fluctuation of the damping force itself is suppressed by adjusting the blending amount of the metal ions doped in the polyurethane particles, thereby suppressing the generation of the inrush power itself. Even if the inrush power is generated, its magnitude can be suppressed. That is, the suppression of the fluctuation phenomenon of the damping force in the electrorheological fluid of the present invention also leads to the suppression of the inrush current.

Next, examples will be given to explain the present invention in more detail, but the present invention is not limited thereto.
The electrorheological fluid of the example was prepared according to the flow chart for producing the electrorheological fluid shown in FIG.

Lithium chloride and zinc chloride were used as raw materials for metal ions (lithium ion and zinc ion), and an electrolyte-containing polyol solution (polyol: Polyol3165 manufactured by Perstop) in which this and a catalyst for polyurethane synthesis were dissolved was prepared.
The amount of lithium ions in the finally obtained electrorheological fluid is 0.0007 mol / kg to 0.007 mol / kg, and the amount of zinc ions is 0 mol / kg to 0.005 mol / kg. Adjustment was made to prepare an electrolyte-containing polyol solution.

On the other hand, for silicone oil (KT-5 manufactured by Momentive) used as an electrically insulating medium, emulsifier 1 (KF-862 manufactured by Shinetsu Chemical Industry Co., Ltd. or OF7747 manufactured by Momentive) and emulsifier 2 (Fludicon) having an alkoxy group. Fluorinated amino-modified polysiloxane (manufactured by Momentive) and a lubricant (GPW2233 manufactured by Momentive) were dissolved to prepare a silicone solution (solution containing an electrically insulating medium). The emulsifier 1 having an alkoxy group was used in an amount of 1.5% by mass with respect to the silicone oil which is an electrically insulating medium.
In addition, a silicone solution (solution containing an electrically insulating medium) under the same conditions except that emulsifier 2 was not used was also prepared.

A predetermined amount of the electrolyte-containing polyol solution and the electrically insulating medium-containing solution (silicone solution) were weighed and filled in the container of the disperser. The concentration and amount of each solution were variously adjusted so that the amount of polyurethane particles in the finally obtained electrorheological fluid was 50% by mass.
Then, as shown in the flow chart of FIG. 1, the electrolyte-containing polyol solution was dispersed in the electrically insulating medium-containing solution in the emulsification step.
Next, about 20% of the total amount of the curing agent isocyanates (a mixture of 2,4-diisocyanate toluene (TDI) manufactured by Tosoh Corporation and the multimer diphenylmethane diisocyanate (p-MDI)) is added to the system. And temporarily cured. Then, in the main curing step, the remaining 80% of the curing agent was added. The total amount of the curing agent added here is the molar ratio of the hydroxy group (OH group) of the polyol and the isocyanate group (NCO group) of the curing agent (isocyanates): (NCO group) / (OH group) of 1 to 1. It was adjusted to be .5. By making the amount of the curing agent larger than the equal amount of the polyol amount, in addition to the water removing effect of the emulsifier 1 having an alkoxy group, water removal by the reaction with the water content by the isocyanate group of the curing agent can be expected.
After the completion of the main curing step, the obtained fluid was filtered using a filter having a mesh of 125 μm to obtain an electrorheological viscous fluid.

[Test Example 1: Electrorheological fluid performance test using an actual damper]
The electrorheological fluid performance test was carried out with the electrorheological fluid damper 11 shown in FIG.
The electrorheological fluid used in this test was prepared by using emulsifier 1 and emulsifier 2 in combination.
The equipment and measurement conditions of the damper tester are as follows.
・ Measuring device: Vertical vibration machine (Tokyo Koki Co., Ltd.)
・ Amplitude type: sine wave ・ Frequency: 1Hz
・ Amplitude width: ± 40 mm
・ Applied voltage: 5kV
-Measurement temperature: 45 ° C
-Temperature measurement: Sheath thermocouple K type In the electrorheological fluid damper system used in the examples, a power supply of 50 W is used and a maximum of 5,000 V is applied, so 10 mA is set as the upper limit current value.

FIG. 3 shows the relationship between the amount of lithium ions in the electrorheological fluid used for the electrorheological fluid damper and the standard deviation of the damping force when a voltage of 5 kV is applied to the damper (N number: about 500 in this example). It is a figure which shows. The standard deviation of the damping force is an index that quantitatively expresses the fluctuation. At the measurement points shown in this figure, the amount of zinc ions in the electroviscous fluid is 0.005 mol / kg in the region where the lithium ion amount is less than 0.003 mol / kg, and 0.003 mol / kg or more in the region where the lithium ion amount is 0.003 mol / kg or more. Then, it is about 0.00035 mol / kg.
As shown in FIG. 3, it was confirmed that the standard deviation sharply increased in the region where the lithium ion amount was less than 0.003 mol / kg. The reason for this is that although the dispersibility was improved by the combined use of emulsifier 2 (embroidery for improving redispersibility), the frictional force between the polyurethane particles was considered to be reduced, and on top of that, lithium ions were required to obtain a sufficient electrorheological effect. It is probable that the amount was insufficient, and therefore the electrorheological effect when the voltage was applied was small and the damping force was insufficient.
From the results of this figure, it was confirmed that, for example, in a system using an electrorheological fluid prepared by using emulsifier 1 and emulsifier 2 in combination, the lithium ion amount is preferably 0.003 mol / kg or more.

FIG. 4 shows the relationship between the amount of lithium ions (0.0007 mol / kg to 0.007 mol / kg) in the electrorheological fluid used for the electrorheological fluid damper and the current value when a voltage of 5 kV is applied to the damper. It is a figure which shows. At the measurement points shown in this figure, the amount of zinc ions in the electrorheological fluid is about 0.00035 mol / kg.
As shown in FIG. 4, it was confirmed that the damper current value increased as the amount of lithium ions increased. In particular, from the approximate curve (see the broken line), it was confirmed that the damper current value increased sharply when the lithium ion amount exceeded 0.006 mol / kg. In the electrorheological fluid damper, it is desirable that the current value at 45 ° C. is 1.0 mA or less.
From the results in this figure, it can be judged that it is preferable that the amount of lithium ions is 0.006 mol / kg or less.

[Test Example 2]
In the obtained electrorheological fluid, the particle size of the polyurethane particles was measured, the viscosity before and after the heat load was measured, and the viscosity increase rate was calculated.
The electrorheological fluid used in this test was prepared by using emulsifier 1 and emulsifier 2 in combination.
<Average particle size>
・ Measuring device: Laser diffraction / scattering type particle size distribution measuring device LA-350 (HORIBA, Ltd.)
<Viscosity before and after heat load>
・ Heat load device: Natural convection constant temperature bath SH400 (Yamato Scientific Co., Ltd.)
-Heat load conditions: heating at 120 ° C. for 100 hours Based on the above measurement results, in the electroviscosity fluid prepared in the example, the measured particle size value (vertical axis) of the polyurethane particles with respect to the amount of zinc ions used (horizontal axis). (Axis) is shown in FIG. 5, and the rate of increase in viscosity (vertical axis) of the electroviscosity fluid after heat loading with respect to the amount of zinc ions used (horizontal axis) is shown in FIG.

FIG. 5 is a diagram showing the relationship between the amount of zinc ions in the electrorheological fluid and the particle size of the obtained polyurethane particles. As shown in FIG. 5, it was confirmed that the particle size of the polyurethane particles increased as the amount of zinc ions decreased. In particular, from the approximate curve (see the broken line), it was confirmed that the polyurethane particle size dramatically increased when the zinc ion content was less than 0.00004 mol / kg. At the measurement points shown in this figure, the amount of lithium ions at the zinc ion amount: 0 mol / kg is 0.003 mol / kg, and the amount of lithium ions in the region where the zinc ion amount exceeds 0 mol / kg is 0.004 mol / kg. ..
As described above, the surface area of particles having a large polyurethane particle size is reduced, and the contact area between the particles is reduced, so that the electrorheological effect is reduced. Further, particles having a large polyurethane particle size also have a problem that their sedimentation is accelerated. As described above, it is desirable that the particle size of the polyurethane particles is 5 μm or less in consideration of the electrorheological effect and the dispersion / sedimentation phenomenon.
From the results shown in this figure, it can be judged that it is preferable that the zinc ion amount is 0.0004 mol / kg or more.

FIG. 6 is a diagram showing the relationship between the amount of zinc ions and the rate of increase in viscosity of the electrorheological fluid after heat loading. As shown in FIG. 6, it was confirmed that the viscosity increase rate increased as the amount of zinc ions increased. An increase in the viscosity of the electrorheological fluid affects the damping force of the damper, and when the viscosity increases, the ride quality becomes worse in the vehicle body to which the damper is applied. Therefore, it is desirable that the amount of zinc ions is in a range in which the viscosity change rate is approximately ± 5% or less, that is, 0.0004 mol / kg or less, where it can be judged that there is almost no change in viscosity.

[Test Example 3: Electrorheological fluid performance test using an actual damper]
An electrorheological fluid performance test was carried out using the electrorheological fluid damper 11 shown in FIG. 2 under the same conditions as in Test Example 1, but at measurement temperatures of 45 ° C., 60 ° C., and 80 ° C.
The electrorheological fluid used in this test was prepared by using emulsifier 1 and emulsifier 2 in combination.

FIG. 7 shows a Lissajous waveform (45 ° C.) of the stroke (piston displacement) and damping force using the actual damper machine before and after the fluctuation improvement (comparative example) and after the improvement (example).
The amount of lithium ions and the amount of zinc ions in the electrorheological fluid used in the electrorheological fluid damper 11 obtained from the resage waveform of FIG. 7 are as follows.
・ Example (after improvement of fluctuation)
Lithium ion amount: 0.00375 mol / kg
Zinc ion amount: 0.00035mol / kg
・ Comparative example (before improvement of fluctuation)
Lithium ion amount: 0.0007 mol / kg
Zinc ion amount: 0.005 mol / kg
As shown in FIG. 7, in the Lissajous waveform of the comparative example, the damping force is not kept constant, and fluctuations that fluctuate up and down can be confirmed. On the other hand, in the Lissajous waveform of the example in which the amount of lithium ion and the amount of zinc ion were adjusted, it was confirmed that the fluctuation was improved.

FIG. 8 is a diagram showing the relationship between the current value at 45 ° C. and the current value at 65 ° C. when a voltage of 5 kV is applied to the electrorheological fluid damper. In this figure, the horizontal axis and the vertical axis are current values measured at 45 ° C. and 65 ° C., respectively. The results of Example (◇) or Comparative Example (◯) shown in FIG. 8 were obtained by using the electrorheological fluid having the lithium ion amount and the zinc ion amount shown in Formulations 1 to 7. In FIG. 8, the comparative example group shows the results of prescriptions 1 to 5 in order from the result with the smallest damper current value (horizontal axis) at 45 ° C., and the example group has the damper current value (vertical axis) at 65 ° C. A slightly higher result is the result of Formulation 6.

As shown in FIG. 8, it can be confirmed that the behavior of the result of the example shown by the square point (◇) is completely different from the result of the comparative example shown by the round point (◯).
In the amount of metal ions specified in the present invention, the ratio of the 65 ° C. current value to the 45 ° C. current value is high, because the ion mobility at 65 ° C. is high, the polarization of the polyurethane particles is large, that is, the damper damping force is strong. The fluctuation of the damping force under high temperature is also improved.
In general, since the electrorheological fluid decreases in viscosity at high temperature, the electrorheological effect, that is, the damping force decreases, and in order to prevent this, it is necessary to further improve the ion mobility at high temperature. The electrorheological fluid of the present invention has achieved improved ion mobility and damping force at high temperatures, and as shown in FIG. 9 (using the electrorheological fluid of Formulation 7), the damping force fluctuates even at 80 ° C. A non-resage waveform is obtained.

[Test Example 4: Electrorheological fluid performance test using an actual damper]
An electrorheological fluid performance test was carried out on the electrorheological fluid damper 11 shown in FIG. 2 under the same conditions as in Test Example 1, but at a measurement temperature of 45 ° C.
The electroviscous fluid used in this test is an electroviscous fluid prepared by using emulsifier 1 and emulsifier 2 in combination (containing an emulsifier for improving redispersibility) and an electroviscous fluid prepared by using only emulsifier 1. No emulsifier for improving dispersibility).

FIG. 13 shows the stroke (piston displacement) and damping using an actual damper machine using (a) an electrorheological fluid containing an emulsifier for improving redispersibility and (b) an electrorheological fluid not containing an emulsifier for improving redispersibility. The force resage waveform (45 ° C.) is shown (piston speed of the resage waveform shown in FIGS. 13 (a) and 13 (b): 0.02 m / s, 0.05 m / s, 0.1 m / s, 0.13 m / s, 0.15 m / s, 0.3 m / s, 0.6 m / s, 0.9 m / s).
The amount of lithium ions and the amount of zinc ions in the electrorheological fluid (both containing the emulsifier for improving redispersibility and not containing the emulsifier for improving redispersibility) used in the electrorheological fluid damper 11 obtained with the resage waveform of FIG. 13 It is as follows.
(A) Electrorheological fluid containing an emulsifier for improving redispersibility Lithium ion content: 0.0014 mol / kg
Zinc ion amount: 0.005 mol / kg
(B) Electrorheological fluid without emulsifier for improving redispersibility Lithium ion amount: 0.0014 mol / kg
Zinc ion amount: 0.00035mol / kg
As shown in FIG. 13, in the Lissajous waveform using (a) an electrorheological fluid containing an emulsifier for improving redispersibility, the damping force is not kept constant, and fluctuations that fluctuate up and down can be confirmed. On the other hand, it was confirmed that (b) the fluctuation was improved in the Lissajous waveform using the electrorheological fluid containing no emulsifier for improving redispersibility.
This result shows that it is possible to achieve both the electrorheological viscosity effect and the improvement of the redispersibility by using the emulsifier 1 having an alkoxy group without using the emulsifier for improving the redispersibility.

Further, FIG. 14 shows the standard deviation of the damping force calculated from the resage waveform shown in FIG. 13 (calculated from the region where the piston speed is 0.1 m / s, the damping force is 0 kN or more, and the stroke is ± 20 mm). As described above, the standard deviation of the damping force is an index that quantitatively expresses the fluctuation, and under this condition, (a) the redispersibility is improved as compared with (a) the standard deviation of the emulsifier for improving the redispersibility. The results were obtained that the standard deviation of the electroviscous fluid containing no emulsifier was small.

[Test Example 5: Current density measurement using a rheometer]
The current densities of the prepared various electrorheological fluids were measured using a rheometer while changing the measurement temperature. The equipment and measurement conditions used for the measurement are shown below.
The electrorheological fluid used in this test is an electrorheological fluid prepared by using only emulsifier 1 (without emulsifier for improving redispersibility).
<Current density>
The current density (μA / cm ² ) when a voltage was applied to the obtained electrorheological fluid was measured.
-Measuring device: Rheometer MCR302 (Anton Pair)
・ Jig: CC27
-Measurement temperature: 10 ° C, 30 ° C, 50 ° C, 80 ° C
・ Applied voltage: 5kV
・ Sample volume: 15 mL
・ Measurement program: Current value 1 minute after the start of strain dispersion measurement (frequency: 0.2Hz)
-Lithium ion amount in electrorheological fluid: 0.002 mol / kg, 0.0023 mol / kg, or 0.0038 mol / kg; Zinc ion amount: 0.00035 mol / kg (constant)
Based on the above measurement results, FIG. 15 shows the current density values (vertical axis) when a voltage of 5 kV is applied to the leometer with respect to the measured temperature (horizontal axis) for each lithium ion amount of the electrorheological fluid.
The upper limit of the damper test current value is 10 mA (current density conversion value: 15 μA / cm ² ) at 80 ° C.

As shown in FIG. 15, in the case of an electrorheological fluid containing no emulsifier for improving redispersibility, an electrorheological fluid having a lithium ion amount of 0.0038 mol / kg has a current density of 15 μA / cm ² at 80 ° C. The result was much higher. From this result, it was determined that the upper limit of the amount of lithium ions was 0.003 mol / kg in the case of the electrorheological fluid containing no emulsifier for improving redispersibility.

11 ERF damper (electrorheological fluid damper), 12 inner cylinder (cylinder), 13 outer cylinder, 20 piston, 23 piston rod, 14 intermediate cylinder (electrode)

Claims

An electrorheological fluid in which polyurethane particles are dispersed in an electrically insulating medium.
The polyurethane particles contain at least one type of metal ion contained in the particles or adhered to the surface of the particles.
The metal ion is an electrorheological fluid containing lithium ion and zinc ion in a smaller amount than the lithium ion.
The lithium ion is in the range of 0.001 to 0.006 mol / kg, and is in the range of 0.001 to 0.006 mol / kg.
The electrorheological fluid according to claim 1, wherein the zinc ion is in the range of 0.00004 to 0.0004 mol / kg.
The lithium ion is in the range of 0.003 to 0.006 mol / kg, and is in the range of 0.003 to 0.006 mol / kg.
The electrorheological fluid according to claim 2, wherein the zinc ion is in the range of 0.00004 to 0.0004 mol / kg.
The electrorheological fluid according to any one of claims 1 to 3, wherein the polyurethane particles are a reaction product of a mixture containing polyols, isocyanates, and an emulsifier having an alkoxy group.
The lithium ion is in the range of 0.001 to 0.003 mol / kg.
The zinc ion is in the range of 0.00004 to 0.0004 mol / kg.
The electrorheological fluid according to claim 1 or 2, wherein the polyurethane particles are a reaction product of a mixture containing polyols, isocyanates, and only an emulsifier having an alkoxy group as an emulsifier.
With the piston
The cylinder in which the piston is stored and
An electrorheological fluid damper enclosed in the cylinder and having an electrorheological fluid whose viscosity is changed by applying a voltage.
In the electroviscous fluid, polyurethane particles are dispersed in an electrically insulating medium, and the polyurethane particles contain at least one kind of metal ion contained in the particles or adhered to the surface of the particles, and the metal thereof. Ions are electroviscous fluids containing lithium ions and zinc ions in smaller amounts than the lithium ions.
Electrorheological fluid damper.