JPH0764649A - Electrode - Google Patents

Abstract

PURPOSE:To ensure the utmost effect of electrical viscosity by roughening the surface of the electrode that is used for application of voltage to the electroviscous fluid where the solid particles are scattered and cones into contact with the electroviscous fluid. CONSTITUTION:This electrode is used to apply the voltage to the electroviscous fluid where the solid particles are scattered, and the surface of the electrode being in contact with the electroviscous fluid is roughened. This roughening degree is shown by the surface roughness, i.e., the average displacement from the average height of the electrode plane. It is desirable to set the roughening degree at a level equal to or larger than the diameter of the solid particle included in the electroviscous fluid, and it is enough to cause the slip friction to the solid particle. Meanwhile the resessing/ projecting pitches of the roughened surface are preferably set larger than the diameter of the solid particle and smaller than 100 or 50 times as much as the particle diameter. Furthermore the metallic electrode plates of copper, aluminum, etc., are used as electrodes, or a metallic electrode plate covered with an insulated layer of zirconium oxide, etc., is also used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode for applying a voltage to an electrorheological fluid whose viscosity can be controlled by applying a voltage, and can be used for electrical control of mechanical devices such as clutches, valves, shock absorbers and engine mounts. Regarding electrodes.

[0002]

2. Description of the Related Art Electro-Rheological Fluid, Electro-Viscous Fluid whose viscosity changes with the application of voltage
scous Fluid,) has been known for a long time (Duff, AWP
hysical Review Vol, 4, No.1 (1896) 23). Initial research on electrorheological fluids focused on liquid-only systems, and the effect was inadequate, but after that, we moved to research on electrorheological fluids in solid dispersion systems, and obtained considerable electrorheological effects. Came to be. For example, Winslow proposed an electrorheological fluid that uses paraffin and silica gel powder and water to make the system slightly conductive (Winsl
ow, WM, J. of Applied Physics, Vol.20 (1949) 113
7). According to this Winslow study, the electrorheological effect of the electrorheological fluid is called the ER effect or Winslow effect.

On the other hand, the thickening effect (E
Elucidation of the mechanism of expression of the R effect), such as Klass
Is a dispersoid in an electrorheological fluid.Each particle has an induced polarization of the Doubly polarization in the electric field.
le Layer), which is the main cause (Kla
ss, DL, et al., J. of Applied Physics, Vol.38, No
1 (1967) 67). This is an electric double layer
yer), the ions adsorbed around the dispersoid (solid particles such as silica gel) are uniformly arranged on the outer surface of the dispersoid when E (electric field) = 0. =
When the value is finite, the ion distribution is biased and each particle exerts an electrostatic action on each other in the electric field. In this way, each particle forms a bridge (crosslink) between the electrodes, and shear resistance against stress is exhibited, that is, a thickening effect is exhibited.

[0004]

As described above, the electrorheological fluid exerts its thickening effect because each particle forms a bridge (crosslink) between the electrodes, and the terminal particle electrically contacts the electrode surface. Although bonded and expresses shear resistance to stress, conventionally, the metal plate electrode surface of copper or the like is a smooth surface, and when the electrorheological fluid is subjected to shear force, the end particles in the bridge and the electrode surface are It was found that the friction was low and slippage occurred, and as a result, stress was not efficiently transmitted to the electrodes and the electrorheological effect was not maximized.

The present invention relates to an improvement of an electrode, and an object of the present invention is to provide an electrode for applying an electrorheological fluid that can maximize the electrorheological effect.

[0006]

The electrode of the present invention is an electrode used for applying a voltage to an electrorheological fluid in which solid particles are dispersed in a fluid, and the electrode surface in contact with the electrorheological fluid is rough. It is characterized by being faced.

The electrode of the present invention will be described below. Electrodes include copper, aluminum, gold, platinum, silver, iron, zinc, palladium, osmium, iridium, nickel,
It is a metal electrode plate made of lead, tantalum, or the like, or at least one electrode surface of which is coated with an insulating layer.

Such an insulating layer is made of zirconium oxide,
Oxides of yttrium oxide, zirconium oxide / yttrium oxide, beryllium oxide, magnesium oxide, calcium oxide, silicon dioxide, silane coupling agents, alumina, titania, thorium oxide, silicon carbide, titanium carbide, tungsten carbide, boron carbide (B ₄ C), carbide such as zirconium carbide, vanadium carbide, tantalum carbide, nitride such as silicon nitride, diamond, i-C (a-Diam)
ond) and the like by the CVD (Chemical Vapor Deposition) method,
It can be formed by stacking by a plasma CVD method, an ion beam CVD method, or the like. Further, it may be an organic insulating layer, and in this case, it is an insulating polymer having oil resistance to an electrorheological fluid and may be operated at a high temperature of 150 ° C., so that heat resistance is required. To be done.
As such an organic insulating layer forming material, for example, polyamide, polyacetal, polybutylene terephthalate,
Thermoplastic engineering plastics such as polyethylene terephthalate and reinforced polyethylene terephthalate, non-crosslinked thermoplastic engineering plastics such as polyether sulfone, polyphenylene sulfide, polyarylate, polyamide imide, polyether imide and polyether ether ketone, polyimide, polyarylate , Non-crosslinking type compression molding engineering plastics such as fluororesin, polyamino bismaleimide, polytriazine, crosslinked polyamideimide, polyvinylphenol / epoxy, Friedel craft resin /
Cross-linking engineering plastics such as epoxy and heat-resistant epoxy, blends of these plastics (eg polymer alloys or copolymers), and those reinforced with glass fibers and whiskers of inorganic substances (eg carbon fibers) are used as forming materials. can do. In order to stack these insulating layers on the electrodes, they can be formed by a CVD method, a PVD method, a vapor deposition method, a spray method, a coating method or the like similarly to the inorganic insulating layer. In addition, it is formed by coating drying oil and baking it.
An insulating layer such as a so-called enamel coating or a formal coating coated with polyvinyl formal and baked may be used, and in this case as well, a spraying method, a coating method, a dipping method and the like may be used as the forming method. The thickness of both the inorganic insulating layer and the organic insulating layer laminated on the electrode may be 0.01 μm to 1000 μm, preferably 0.01 μm to 50 μm, and more preferably 0.1 μm to 20 μm.

In the electrode of the present invention, the surface may be roughened, and it is sufficient if it causes sliding friction with respect to the solid particles contained in the electrorheological fluid. The degree of roughening of the electrode surface is indicated by the surface roughness which is the average displacement from the average height of the electrode plane, but preferably,
The surface roughness may be equal to or larger than the particle diameter of solid particles in the electrorheological fluid described later. For example, 1
It is preferable that the thickness is 0 nm to 400 μm. The particle diameter has a distribution, and the surface roughness is preferably larger than the minimum particle diameter, preferably larger than the average particle diameter (x _av ), and most preferably larger than the maximum particle diameter. The uneven pitch on the rough surface is 100 times or less, preferably 50 times or less, and more preferably 10 times or less as large as or larger than the particle diameter of the solid particles.

The relationship between the particle size distribution and the roughness on the electrode surface is as follows:
If the proportion of particles having a particle diameter of 2 times or more of the average particle diameter (x _av ) exceeds 30%, the thickening effect decreases, so particles having a particle diameter of 2 times or more of the average particle diameter (x _av ) are preferable. By setting the proportion of particles having a diameter of 30% or less, preferably 10% or less, the case where the roughness on the electrode surface is finished to the same level as the average particle diameter (x _av ) of solid particles It has been found that a thickening effect can be obtained.

In order to roughen the surface of the electrode, it is advisable to control the polishing of the surface of the electrode, and it is also possible to use an etching means or a machining means. You may use the material which has.
When using an electrode having a groove-like rough surface, it is necessary to mount the electrode so that the direction of the groove is orthogonal to the movement of the fluid or the movement of the electrode.

The state of the rough surface can be measured by a surface roughness meter (for example, SEF-30D manufactured by Kosaka Laboratory Ltd.), and the particle size distribution of solid particles is manufactured by Shimadzu Corporation. , SALD-1100 etc. can be used for easy measurement.

The electrorheological fluid comprises a fluid, solid particles, a dispersant, a polyhydric alcohol component, and, if necessary, an acid, salt or base component, and various additives. As a fluid,
Examples of the electrically insulating fluid include, but are not limited to, mineral oils and synthetic lubricating oils, and specifically, paraffinic mineral oils, naphthenic mineral oils, poly-α-olefins, polyalkylene glycols, silicones, diesters, polyol esters. , Phosphoric acid ester, silicon compound, fluorine compound,
Examples include oils such as polyphenyl ether and synthetic hydrocarbons. The viscosity range of these electrically insulating fluids can be 5 to 300 cSt at 40 ° C.

Conventional solid particles are used as the dispersoid, and for example, silica gel, hydrous resin, diatomaceous earth, alumina, silica-alumina, zeolite, ion exchange resin, cellulose and the like can be used. These solid particles usually have a particle size of 10 nm to 200 μm and are 0.1
It is used in a proportion of 50% by weight to 50% by weight. 0.1% by weight
If the amount is less than 50%, the ER effect is small, and if it exceeds 50% by weight, the dispersibility is deteriorated.

In the electrorheological fluid, a dispersant may be used in order to uniformly and stably disperse solid particles in the electrically insulating fluid. Conventional dispersants are used, for example, sulfonates, phenates, phosphonates, succinimides, modified silicones, amines, nonionic dispersants, and the like, and specifically magnesium sulfonate. , Calcium sulfonate, calcium phosphonate, polybutenyl succinimide, amino-modified silicone, sorbitan monooleate, sorbitan sesquioleate and the like. These are usually used in an amount of 0.1% by weight to 30% by weight, but they may not be used if the dispersibility of solid particles is good.

The polyhydric alcohol is a dihydric alcohol,
Trihydric alcohols are effective, and ethylene glycol, triethylene glycol, tripropylene glycol, glycerin, propanediol, butanediol, hexanediol and the like may be used.

If desired, acids, bases and salts may be added. As the acid component, inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid, perchloric acid, chromic acid, phosphoric acid and boric acid, or acetic acid,
Organic acids such as formic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, oxalic acid and malonic acid are used.

The salt may be a metal or a basic group (NH
₄ ⁺ , N ₂ H ₅ ^+, etc.) and an acid group, and any of these can be used. Of these, those which are dissolved in a polyhydric alcohol to dissociate, for example, those which form typical ionic crystals such as halides of alkali metals and alkaline earth metals, and alkali metal salts of organic acids are preferable. As this kind of salt, LiCl,
NaCl, KCl, MgCl ₂ , CaCl ₂ , BaCl
₂ , LiBr, NaBr, KBr, MgBr ₂ , Li
_{I, NaI, KI, AgNO 3} , Ca (NO 3) 2, N
aNO ₂ , NH ₄ NO ₃ , K ₂ SO ₄ , Na ₂ SO _4,
There are NaHSO ₄ , (NH ₄ ) ₂ SO ₄ or alkali acid metal salts such as formic acid, acetic acid, oxalic acid and succinic acid.

The base is a hydroxide of an alkali metal or an alkaline earth metal, a carbonate of an alkali metal, an amine, etc., and a base which is dissolved in a polyhydric alcohol or a system of a polyhydric alcohol and water to dissociate. preferable. As this kind of base, NaOH, KOH, Ca (OH) ₂ , Na _{2
CO 3, NaHCO 3, K 3} PO 4, Na 3 PO 4, aniline, alkyl amines, such as ethanol amine. The above-mentioned salt and base can be used in combination.

Acids, salts and bases are usually used in a proportion of 5% by weight or less with respect to the entire electrorheological fluid. If it exceeds 5% by weight, it becomes undesirably easy to energize and power consumption increases.

When a polyhydric alcohol component, an acid, a salt, or a base component is added, it is preferable to use an insulating layer having alcohol resistance and acid resistance. The polyhydric alcohol component and the acid, salt, or base component can improve the ER effect even when used alone, but the polyhydric alcohol component can improve the ER effect in a high temperature range, and The acid component is capable of increasing the polarization effect. Further, these two components can be used in combination, and a synergistic effect of increasing the polarization effect as well as the ER effect in the high temperature region is exhibited.

An antioxidant may be added as an additive. The antioxidant is intended to prevent the oxidation of the polyhydric alcohol, which is a polarizing agent, as well as the oxidation of the electrically insulating liquid.

As the antioxidant, it is preferable to use a polarizing agent or one which is inactive to the solid particles, and a commonly used phenol type or amine type antioxidant can be used. 2,6-di-t-butylparacresol, 4,4'-methylenebis (2.6-di-t
-Butylphenol), 2,6-di-t-butylphenol and the like, and as the amine type, dioctyldiphenylamine, phenyl-α-naphthylamine, alkyldiphenylamine, N-nitrosodiphenylamine and the like can be used.

Of course, water may be used to the extent that it does not hinder the ER effect in the electrorheological fluid system.

[0025]

In the electrorheological fluid application device, for example, an electrorheological fluid containing solid particles is put between two electrodes, and when a voltage is applied between both electrodes, the solid particles are applied between the electrodes. Chain is formed, and in this state, when one electrode is displaced to give a strain to the electrorheological fluid, the stress is transmitted through the electrorheological fluid to the other electrode. It is considered that the particles in contact finally transmit stress, and if the frictional force of the solid particles against the electrode surface is increased, the solid particles are transferred by the solid particles without sliding on the electrode surface. All forces will be transmitted to the other electrode.

The present invention has been made based on such knowledge, and the surface of the electrode for applying an electrorheological fluid is roughened to the extent that it causes sliding friction with respect to the solid particles contained in the electrorheological fluid. Must have been done.
That is, whether the surface is roughened to be larger than the average particle size of the solid particles, or the relationship between the particle size distribution and the surface roughness of the electrode depends on the particle size distribution at the volume fraction of the solid particles in the electrorheological fluid. , And when the ratio of particles having a particle size that is at least twice the average particle size (x _av ) is 30% or less, the roughness on the electrode surface is about the same as the average particle size (x _av ) of solid particles. A thickening effect corresponding to the case of finishing can be obtained.

The present invention will be described below based on examples, but the present invention is not limited to these examples.

[0028]

Example 1 The composition of an electrorheological fluid is shown.

Alkylbenzene (40 ° C., 17 cSt) 83% by weight Silica gel (average particle size 1.4 μm, 10% of particles having a particle size of 2.8 μm or more in the particle size distribution in volume fraction) 7 Wt% triethylene glycol 2 wt% polybutenyl succinimide 8 wt% The viscosity of the resulting electrorheological fluid is 30 cSt at 40 ° C. As the electrode material, SUS (No. 304, surface roughness = 0.1 μm) is used, and the surface is machined to have an average roughness of 20 μm. The size of the electrode is 20 mm wide × length The electro-rheological fluid application device was 50 mm in length, and two electrodes having the same surface treatment were opposed to each other with an electrode interval of 1 mm.

In this device, a constant flow rate (90 ml / min.) Of electrorheological fluid is flown between both electrodes while
An electric field of KV / mm (AC 60 HZ AC) was applied, and the differential pressure (Kg / cm ² ) to the electrorheological fluid required to maintain the flow rate of the electrorheological fluid at the above value was measured. The results are shown in Table 1 below.

[0031]

[Embodiment 2] A fluid necessary for flowing a constant flow rate of electrorheological fluid, except that the electrorheological fluid applying apparatus in Example 1 having a surface roughness of the electrode surface of 1.5 μm was used. The pressure was measured. Similarly, the results are shown in Table 1 below.

[0032]

[Embodiment 3] In the same manner as in Embodiment 1, except that an electrorheological fluid applying device having a surface roughness of the electrode surface of 1.0 μm was used, a fluid necessary for flowing a constant flow rate of electrorheological fluid. The pressure was measured. Similarly, the results are shown in Table 1 below.

[0033]

Example 4 A fluid necessary for preparing an electrorheological fluid in the same manner as in Example 2 except that the electrorheological fluid in Example 2 has the following composition and flowing a constant flow rate of the electrorheological fluid. The pressure was measured. Similarly, the results are shown in Table 1 below.

Alkylbenzene (40 ° C., 17 cSt) 83% by weight Silica gel (average particle size 1.4 μm, 20% of particles having a particle size of 2.8 μm or more in the particle size distribution in volume fraction) 7 Wt% triethylene glycol 2 wt% polybutenyl succinimide 8 wt% The viscosity of the resulting electrorheological fluid is 30 cSt at 40 ° C.

[0035]

Example 5 As silica gel in the electrorheological fluid of Example 4, the average particle size is 1.4 μm, and the ratio of particles having a particle size of 2.8 μm or more in the particle size distribution in volume fraction is 30.
An electrorheological fluid was prepared in the same manner except that the same amount of 0.1% was used, and the fluid pressure required to flow a constant flow rate of the electrorheological fluid was measured as in Example 4. Similarly, the results are shown in Table 1 below.

[0036]

Example 6 As silica gel in the electrorheological fluid of Example 4, the average particle size was 1.4 μm, and the ratio of particles having a particle size of 2.8 μm or more in the particle size distribution in volume fraction was 40.
An electrorheological fluid was prepared in the same manner except that the same amount of 0.1% was used, and the fluid pressure required to flow a constant flow rate of the electrorheological fluid was measured as in Example 4. Similarly, the results are shown in Table 1 below.

[0037]

Example 7 As silica gel in the electrorheological fluid of Example 4, the average particle size was 1.4 μm, and the ratio of particles having a particle size of 2.8 μm or more in the particle size distribution in volume fraction was 50.
An electrorheological fluid was prepared in the same manner except that the same amount of 0.1% was used, and the fluid pressure required to flow a constant flow rate of the electrorheological fluid was measured as in Example 4. Similarly, the results are shown in Table 1 below.

[0038]

Comparative Example 1 In the electrorheological fluid application device of Example 1, the surface was untreated and used as an electrode.
Similarly, the fluid pressure required to flow a constant flow rate of the electrorheological fluid was measured. Similarly, the results are shown in Table 1 below.

[0039]

[Table 1]

As can be seen from Table 1, it is recognized that the thickening effect is increased by roughening the electrode surface.

Claims (1)

[Claims] 1. An electrode used for applying a voltage to an electrorheological fluid in which solid particles are dispersed in a fluid, wherein the electrode surface in contact with the electrorheological fluid is roughened. .