Micromotors, linear motors, micropumps, methods of using the same, microactuators, methods of controlling flow properties of fluids, and apparatuses for controlling flow properties of fluids

Abstract: The present invention provides a use of an electro-sensitive movable fluid, that is, a micromotor, a linear motor, a micropump and a method of using the micropump, a microactuator, and an apparatus which these devices are applied to, and a method and an apparatus of controlling flow properties of a fluid.

Description: The present invention relates to micromotors using electro-sensitive movable fluids (electro-conjugate fluid, ECF) which move between electrodes upon application of a voltage, and more particularly to extremely thin micromotors using the electro-sensitive movable fluids according to the generic clause of claim 1. From document EP-A-0 695 025 there is also already known such a micromotor having a container, a lid, a rotating shaft, born by a shaft hole, a bearing section, and electrodes arranged at the outer side of the cylindrical container, wherein a jet flow of an electro-sensitive moveable fluid is produced upon application of a voltage. Document EP-A-0 787 792 already describes a micromotor comprising a housing constituted of a container to be filled with an electro-sensitive movable fluid and a lid, a rotating shaft and a plurality of electrodes to produce a jet flow of the electro-sensitive moveable fluid, wherein the rotor is rotatably fitted with a housing through the rotating shaft and at least one bearing means. It is known that the characteristics of certain kinds of dielectric fluids vary when the dielectric fluids are subjected to electric fields. In case of liquid crystals, for example, when a voltage is applied to liquid crystal compounds, orientation properties of the compounds are varied to thereby vary light transmittance of the compounds. It is also known that, when a voltage is applied to heterogeneous fluids containing particles or the like, properties of the fluids such as viscosity are varied by Winslow Effect. There are, however, problems in the fluids whose properties are varied upon application of a voltage. For example, the liquid crystal compounds are very expensive, or the heterogeneous fluids show poor dispersion stability. The present inventors have found such a novel effect that some specific fluids move upon application of a voltage, and already applied for patents the specific fluids (electro-sensitive movable fluids) and micromotors using the electro-sensitive movable fluids (see: Japanese Patent applications No. 16871/1996, No. 16872/1996, No. 76259/1996, No. 248417/1996 and No. 241679/1996). The micromotors described in these publications show increased output power when they are miniaturized. In order to more efficiently drive the micromotors disclosed in the above publications, they should be improved for the miniaturization. The motors described in the publications are those of rotor rotation type, and any linear motor which is linearly driven is not described. Further, any pump using the electro-sensitive movable fluid is not described either. When a voltage is applied to an electro-rheological fluid (ER fluid), its hydrodynamic properties such as viscosity greatly vary reversibly at a high speed correspondingly to the applied voltage. The fluids showing these properties are broadly divided into heterogeneous type (particle dispersion type) and homogeneous type. As the heterogeneous ER fluid, a dispersion obtained by dispersing fine particles such as silica gel in an insulating oil is known. The heterogeneous ER fluids, however, have a problem in that sedimentation or flotation of particles takes place because of a difference in specific gravity between the particles and the medium. Even if the particles and the medium have the same specific gravity, the same problem of sedimentation or flotation of particles takes place with time because the temperature dependence of the specific gravity of the particles and that of the specific gravity of the medium are different from each other at low or high temperatures. Moreover, the dispersed particles of the heterogeneous ER fluid form a chain structure when a voltage is applied, and therefore, the hydrodynamic properties of the fluid are changed. With the formation of the chain structure, not only increase of viscosity but also development of elasticity takes place, and the fluid exhibits mechanical response approximate to a solid state. For this reason, linear control of the heterogeneous ER fluids is difficult, and in many cases, complicated control means such as feedback control is necessary. Of the homogeneous ER fluids, a liquid crystal is known as an ER fluid which exhibits no elasticity. The homogeneous ER fluids have ease of controlling because they exhibit no elasticity even when a voltage is applied, and they are free from problems of particle sedimentation and particle flotation because they are homogeneous. However, the homogeneous ER fluids such as liquid crystals are very expensive, so that they are not broadly employed for an industrial use, liquid crystals are only used for, for example, display devices of extremely high value added. Further, the liquid crystals which are the homogeneous ER fluids can be driven only in such a temperature range that the liquid crystals are in the liquid crystal state, so that the temperature range wherein the liquid crystals can be used as the ER fluids is extremely narrow. Though the estimated temperature range wherein the ER fluids are used is from about -30 °C to about 120 °C, the liquid crystals cannot be driven in such a wide temperature range. As described above, the homogeneous ER fluids are advantageous as the ER fluids from the control viewpoint, but they are very expensive and their working temperature range is narrow. On the other hand, the heterogeneous ER fluids are relatively inexpensive, but they are difficult to control and have a problem of fluid stability such as occurrence of particle sedimentation or particle flotation. In the paper No. 96-252, pp. 437-438, of the 8th symposium on "Dynamics relating to Electromagnetic Force", there is description about "Researches on Electrostatic Devices (New Stress-Transfer System Using Fibers)". The particles dispersed in the heterogeneous ER fluid form a chain structure when a voltage is applied to the heterogeneous ER fluid, as described above. This mechanism is applied to the electrostatic devices of the above paper. That is, instead of the particles, an electrode provided with woven fabric on its surface is used in a silicon oil, and a voltage is applied to the "woven fabric electrode", whereby a chain structure equivalent to the particle chain structure of the heterogeneous ER fluid containing particles is formed by the woven fabric to thereby develop hydrodynamic properties of the ER fluid. In other words, instead of using an ER fluid containing particles, using a silicon oil woven fabric free from sedimentation or flotation is bonded to an electrode material and the woven fabric is used as an electrode. By the application of a voltage, fibers of the woven fabric are allowed to stand up, and dynamic resistance of the upstanding woven fibers is produced to control the fluid. Further, the manuscript collection (pp. 203-206) of the 39th automobile control association lecture meeting (Oct. 16, 17, 18, 1996) discloses "New Torque-Transfer System Using Fibers", and describes that, when fabric is adhesion bonded to a circular plate and the circular plate is rotated in an electric field, the shear stress is increased. In the above methods, it is explained that the woven fabric has a rigid structure upon application of a voltage and is orientated in the direction of the electric field thereby to increase the shear stress. In the methods, therefore, the woven fibers which are swayed by the fluid when no voltage is applied are made rigid and orientated by applying a voltage, so that the fibers can resist the relative motion of the fluid to the electrodes, whereby increase of shear stress during application of a voltage is accomplished. In the methods, accordingly, only a silicon oil is used, and hydraulic oil constituting a machine part or a working mechanism is never employed, further applicability of the methods to a mechanism. In the above methods, further, the conductive electrode material is not exposed out at all and is evenly covered with the woven fabric. Moreover, there is no report about production of a jet flow. It is described that the fibers of the woven fabric are swayed in the non-electric field according to the shear rate. Accordingly, flow property control mechanism of the above methods is different from the mechanism of the invention invented by the present inventors, that is, the shear stress is produced by virtue of formation of a jet flow. The shear stress produced in the present invention has hydrodynamic continuity, is free from yield stress which indicates solidification and has ease of controlling, while the above-mentioned fixed electrodes provided with woven fabric do not show these properties. It is an object of the present invention to provide an extremely small-sized rotary motor and linear motor each of which is driven by a jet flow of an electro-sensitive movable fluid produced upon application of a direct-current-voltage and to provide a micropump using the electro-sensitive movable fluid. This object is met by the features of claims 1. The thin micromotor of the invention is broadly divided into a SE type ECF motor (stator-electrode type electro-conjugate fluid motor) and a RE type ECF motor (rotor-electrode type electro-conjugate fluid motor) with respect to the position of the electrode provided therein. In the SE type ECF motor, the electrodes are provided on the upper surface of the bottom and/or the lower surface of the lid of the container (fluid container) and are in contact with the electro-sensitive movable fluid. In the RE type ECF motor, the electrodes are provided on the upper surface and/or the lower surface of the rotator. The housing of the micromotor of the invention generally has a maximum diameter of 50 mm and a maximum height of several mm, and the micromotor is extremely small and particularly thin. In spite of such small size, the micromotor of the invention rotates at a high rotational speed of about several hundreds to several tens of thousands rpm. By making the size of the micromotor of the invention smaller, the electric energy can be converted to rotational energy with much higher efficiency. For example, when a SE type ECF motor whose housing has an inner diameter of 4 mm is used, the efficiency indicated by the ratio of output energy/input energy has been confirmed to be at most 40 %. If a pair of electrodes capable of forming an ununiform electric field in a fluid are arranged in the fluid and if a voltage is applied between the electrodes, a new flow (jet flow) of the fluid, such as a circulating flow, is produced. When the shear direction of the original motion of the fluid is at right angles to the newly produced jet flow of the fluid, it is presumed that resistance to the relative motion of the fluid in the shear direction is produced, that is, shear stress is increased. When a certain kind of a dielectric fluid (i.e., "electro-sensitive movable fluid" referred to herein) is subjected to an electric field, an electric force is generated in the fluid owing to the ununiformity of electric conductivity and dielectric constant. In the direct-current electric field, the Coulomb force acting on space charge dominates the dielectrophoretic force. This Coulomb force causes hydrodynamic instability, resulting in occurrence of convection of the electro-sensitive movable fluid or a secondary motion of the fluid. These phenomena are called as "electrohydrodynamic (EHD) effects". The micromotor according to the invention use, as driving force, a motion (jet flow) of the electro-sensitive movable fluid produced upon application of a voltage to the fluid. These control the flow properties or a fluid by forming a new jet flow from at least one pair of electrodes capable of forming ununiform electric field in the fluid in a different direction, e.g. vertical and opposite direction, from that of the flowing fluid. The present inventors consider that the motion of the electro-sensitive movable fluid is probably by virtue of the EHD effects, but they do not conclude that the phenomenon occurring in the invention is owing to the "EHD effects". The micromotor according to the invention is advantageously used to take out the flow energy of the electro-sensitive movable fluid produced upon application of a voltage as driving force. That is, they are apparatuses to form a jet flow of the dielectric fluid by application of a voltage and to take out the jet flow as driving force. The micromotor of the invention is extremely small, and it can be made thin. Besides, the micromotor can be driven at a high speed. Fig. 1 is a graph showing a relation between conductivity and viscosity of the electro-sensitive movable fluid preferably used in the invention. Fig. 2(A) is a vertical sectional view of the SE type ECF motor of the invention, and Fig. 2(B) is a sectional view taken on line X-X of Fig. 2(A). Fig. 3(C) is a perspective view of the rotator, and Fig. 3(D) is a sectional view taken on line Y-Y of Fig. 2(A). Fig. 4(A) is a vertical sectional view of the RE type ECF motor of the invention, and Fig. 4(B) is a perspective view of the rotator. Fig. 5 is a view showing an embodiment of arrangement of the electrodes in the RE type ECF motor. Fig. 6(A) and Fig. 6(B) are each a sectional view showing another structure of the rotator. Fig. 7 is a view showing a complex type micromotor of the SE type ECF motor and the RE type ECF motor. Fig. 8 is a sectional view of the micromotor having plural rotators. The micropump according to the invention is described in detail hereinafter. The electro-sensitive movable fluid for use in the invention is an organic compound capable of forming a jet flow between the electrodes correspondingly to the applied voltage, said organic compound being liquid at its working temperature. This organic compound is substantially dielectric. The organic compound generally has at least one ester linkage in the molecule. Listed below are examples of the compounds having the above properties and employable as the electro-sensitive movable fluid in the invention. (1) Dibutyl adipate (DBA) (2) Tributyl citrate (TBC) (3) Monobutyl maleate (MBM) (4) Diallyl maleate (DAM) (5) Dimethyl phthalate (DMP) (6) Triacetin (7) Ethyl cellosolve acetate (8) 2-(2-Ethoxyethoxy)ethyl acetate (9) 1,2-Diacetoxyethane (10) Triethylene glycol diacetate (11) Butyl cellosolve acetate (12) Butyl carbitol acetate (13) 3-Methoxy-3-methylbutyl acetate (Solfit AC) (14) Dibutyl fumarate (DBF) (15) 2-Ethylhexyl benzyl phthalate (trade name: Placizer B-8) (17) Propylene glycol methyl ether acetate (PMA) (18) Methyl acetyl ricinoleate (MAR-N) (19) 2-Ethylhexyl palmitate (trade name: Exepal EH-P) (20) Dibutyl itaconate (DBI) (21) Polyethylene glycol monooleate (trade name: Emanone 4110) (22) Butyl stearate (trade name: Exepal BS) (23) 2,2,4-Trimethyl-1,3-pentanediol diisobutyrate (trade name: Kyowanol D) (24) 2,2,4-Trimethyl-1,3-pentanediol monoisobutyrate (trade name: Kyowanol M) (25) Propylene glycol monoethyl ether (26) Propylene glycol ethyl ether acetate (trade name: BP-Ethoxypropyl Acetate) (27) 9,10-Epoxy butyl stearate (trade name: Sansocizer E-4030) (28) Tetrahydrophthalic acid dioctyl ester (trade name: Sansocizer DOTP) (29) Tributyl phosphate (TBP) (30) Tributoxyethyl phosphate (TBXP) (31) Tris(chloroethyl) phosphate (CLP) (32) Ethyl 2-methylacetoacetate (33) 1-Ethoxy-2-acetoxypropane (34) 2-(2,2-Dichlorovinyl)-3,3-dimethylcyclopropane carboxylic acid methyl ester (DCM-40) (35) Linalyl acetate (36) Dibutyl decanedioate (37) Mixture of Kyowanol M and Exepal EH-P in a mixing ratio of 1:4 by weight Kyowanol M (trade name): 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate Exepanl EH-P (trade name): 2-ethylhexyl palmitate (38) Mixture of DAM and Exepal BS in a mixing ratio of 1 : 4 by weight DAM (trade name): diallyl maleate Exepal BS (trade name): butyl stearate (39) Dibutyl dodecanedioate (DBDD) Bu-OCO-(CH 2 ) 5 -CH(Bu)-COO-Bu (40) Dobutyl docosanedioate Bu-OCO-(CH 2 ) 6 -CH(CH 3 )-(CH 2 ) 4 -CH(CH 3 )-(CH 2 ) 6 -COO-Bu (41) Daphne Super Hydraulic Fluid 32 (hydraulic oil) (Idemitsu Kosan Co., Ltd.) The compounds mentioned above can be used singly or in combination. The conductivity and the viscosity of the above compounds, as measured at 25 °C, are set forth in Table 1. Compound (™: trade name) Conductivity (S/m) Viscosity (Pa-s) (1) DBA 3.01×10 -9 3.5×10 -3 (2) TBC 5.71×10 -7 2.0×10 -2 (3) MBM 2.60×10 -5 2.0×10 -2 (4) DAM 7.80×10 -7 2.5×10 -3 (5) DMP 3.90×10 -7 1.2×10 -2 (6) Triacetin™ 3.64×10 -9 1.4×10 -2 (7) Ethyl cellosolve acetate 7.30×10 -5 9.0×10 -4 (8) 2-(2-Ethoxyethoxy)ethyl acetate 6.24×10 -7 1.4×10 -2 (9) 1,2-Diacetoxyethane 2.00×10 -6 1.5×10 -3 (10) Triethylene glyocl acetate 5.20×10 -7 8.1×10 -3 (11) Butyl cellosolve acetate 2.10×10 -8 7.0×10 -4 (12) Butyl carbitol acetate 5.20×10 -8 1.7×10 -3 (13) Solfit AC™ 8.30×10 -8 6.0×10 -4 (14) DBF 2.65×10 -9 . 3.5×10 -3 (15) Placizer B-8™ 1.10×10 -8 7.8×10 -2 (17) PMA 1.56×10 -7 6.0×10 -4 (18) MAR-N™ 1.30×10 -8 1.4×10 -2 (19) Exepal EH-P™ 2.60×10 -10 9.5×10 -3 (20) DBI 1.46×10 -8 3.5×10 -3 (21) Emanone 4110™ 3.75×10 -7 8.0×10 -2 (22) Expal BS™ 3.10×10 -10 8.5×10 -3 (23) Kyowanol D™ 6.24×10 -9 4.0×10 -3 (24) Kyowanol M™ 6.80×10 -8 1.2×10 -2 (25) MP-Ethoxypropanol™ 2.24×10 -5 8.0×10 -4 (26) BP-Ethoxypropyl Acetate™ 3.10×10 -8 6.0×10 -4 (27) Sansocizer E-4030™ 5.46×10 -9 2.0×10 -2 (28) Sansocizer DOTP™ 6.20×10 -10 4.0×10 -2 (29) TBP 2.20×10 -6 2.2×10 -3 (30) TBXP 1.10×10 -5 9.0×10 -3 (31) CLP 7.80×10 -6 3.0×10 -2 (32) Ethyl 2-methylacetoacetate 1.00×10 -4 5.0×10 -4 (33) 1-Ethoxy-2-acetoxypropane 4.41×10 -7 4.0×10 -4 (34) DCM-40™ 2.60×10 -5 5.5×10 -3 (35) Linalyl acetate 1.82×10 -9 1.3×10 -3 (36) Dibutyl decanedioate 1.40×10 -9 7.0×10 -3 (39) Dibutyl dodecanedioate 5.2×10 -9 9.3×10 -3 (40) Dibutyl docosanedioate 1.04×10 -9 2.5×10 -2 (41) Daphne Super Hydraulic Fluid 32 ™ 6.0×10 -10 5.9×10 -2 The electro-sensitive movable fluid used in the invention is preferably a compound or a mixture each having the following specific conductivity and the following specific viscosity. That is, when the conductivity σ and the viscosity η of the "dielectric fluids" including the above compounds are measured under the conditions of an electric field intensity of 2 kVmm -1 and a temperature of 25 °C, the dielectric fluids are distributed as shown in Fig. 1. The compound used as the electro-sensitive movable fluid in the invention is preferably a compound having, at its working temperature, a conductivity σ and a viscosity η located on or inside a triangle in a graph (Fig. 1) wherein the conductivity σ is plotted as abscissa and the viscosity η is plotted as ordinate, said triangle having the following points P, Q and R as vertexes. When a mixture of two or more kinds of compounds is used as the electro-sensitive movable fluid, the mixture is preferably such a mixture as adjusted to have a conductivity σ and a viscosity η located inside the above triangle. Conductivity (σ) Viscosity (η) Point P 4 × 10 -10 S/m 1 × 10° Pa·S (Point P 0 ) preferably 5 × 10 -10 S/m preferably 8 × 10 -1 Pa·S Point Q 4 × 10 -10 S/m 1 × 10 -4 Pa·S (Point Q 0 ) preferably 5 × 10 -10 S/m preferably 2 × 10 -4 Pa·S Point R 5 × 10 -6 S/m 1 × 10 -4 Pa·S (Point R 0 ) preferably 2.5 × 10 -6 S/m preferably 2 × 10 -4 Pa·S In Table 2, the points P 0 , Q 0 and R 0 are particularly preferable points as the vertexes of the triangle wherein the electro-sensitive movable fluid of the invention is located. Some examples of the compounds preferably used as the electro-sensitive movable fluid in the cooling method of the invention are given below. (1) Dibutyl adipate (DBA) (σ = 3.01 × 10 -9 S/m, η = 3.5 × 10 -3 Pa·s) (6) Triacetin (σ = 3.64 × 10 -9 S/m, η = 1.4 × 10 -2 Pa·s) (11) Butyl cellosolve acetate (σ = 2.10 × 10 -8 S/m, η = 7.0 × 10 -4 Pa·s) (12) Butyl carbitol acetate (σ = 5.20 × 10 -8 S/m, η = 1.7 × 10 -3 Pa·s) (13) 3-Methoxy-3-methylbutyl acetate (Solfit AC) (σ = 8.30 × 10 -8 S/m, η = 6.0 × 10 -4 Pa·s) (14) Dibutyl fumarate (DBF) (σ = 2.65 × 10 -9 S/m, η = 3.5 × 10 -3 Pa·s) (17) Propylene glycol methyl ether acetate (PMA) (σ = 1.56 × 10 -7 S/m, η = 6.0 × 10 -4 Pa·s) (18) Methyl acetyl ricinoleate (MAR-N) (σ = 1.30 × 10 -8 S/m, η = 1.3 × 10 -2 Pa·s) (20) Dibutyl itaconate (DBI) (σ = 1.46 × 10 -8 S/m, η = 3.5 × 10 -3 Pa·s) (23) 2,2,4-Trimethyl-1,3-pentanediol diisobutyrate (trade name: Kyowanol D) (σ = 6.24 × 10 -9 S/m, η = 4.0 × 10 -3 Pa·s) (26) Propylene glycol ethyl ether acetate (trade name: BP-Ethoxypropyl Acetate) (σ = 3.10 × 10 -8 S/m, η = 6.0 × 10 -4 Pa·s) (27) 9,10-Epoxy butyl stearate (trade name: Sansocizer E-4030) (σ = 5.46 × 10 -9 S/m, η = 2.0 × 10 -2 Pa·s) (28) Tetrahydrophthalic acid dioctyl ether (trade name: Sansocizer DOTP) (σ = 6.20 × 10 -10 S/m, η = 4.0 × 10 -2 Pa·s) (33) 1-Ethoxy-2-acetoxypropane (σ = 4.41 × 10 -7 S/m, η = 4.0 × 10 -4 Pa·s) (35) Linalyl acetate (σ = 1.82 × 10 -9 S/m, η = 1.3 × 10 -3 Pa·s) (36) Dibutyl decanedioate (σ = 1.40 × 10 -9 S/m, η = 7.0 × 10 -3 Pa·s) (39) Dibutyl dodecanedioate (DBDD) (σ = 5.2 × 10 -9 S/m, η = 9.3 × 10 -2 Pa·s) (40) Dobutyl docosanedioate (σ = 1.04 × 10 -9 S/m, η = 2.5 × 10 -3 Pa·s) (41) Daphne Super Hydraulic Fluid 32 σ = 6.0 × 10 -10 S/m, η = 5.9 × 10 -2 Pa·s) When a mixture of plural compounds is used as the electro-sensitive movable fluid in the invention, the conductivity and the viscosity of the mixture are made to be located inside the triangle defined by the points P, Q and R shown in Fig. 1, whereby the mixture can be preferably used in the invention. In other words, even if each of compounds has a conductivity and/or a viscosity out of the above range, a mixture of the compounds can be favorably used as the electro-sensitive movable fluid in the invention, as far as the conductivity and the viscosity of the mixture are within the above range, respectively. For example, a mixture (σ = 2.60 × 10 -9 S/m, η = 9.8 × 10 -3 Pa·s) of 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (trade name: Kyowanol M, σ = 6.80 × 10 -8 S/m, η = 1.2 × 10 -2 Pa·s) and 2-ethylhexyl palmitate (trade name: Exepal EH-P, σ = 2.60 × 10 -10 S/m, η = 9.5 × 10 -3 Pa·s) in a mixing ratio of 1:4 by weight, each having a conductivity and a viscosity out of the above range, can be favorably used as the electro-sensitive movable fluid in the invention. Also, a mixture (σ = 4.17 × 10 -9 S/m, η = 5.0 × 10 -3 Pa·s) of DAM (diallyl maleate, σ = 7.8 × 10 -7 S/m, η = 2.5 × 10 -3 Pa·s) and butyl stearate (trade name: Exepal BS, σ = 3.1 × 10 -10 S/m, η = 8.5 × 10 -3 Pa·s) in a mixing ratio of 1:4 by weight, each having a conductivity and a viscosity out of the above range, can be favorably used as the electro-sensitive movable fluid in the invention. The requisite of the electro-sensitive movable fluid is that the movable fluid has the above-defined conductivity and viscosity at its working temperature in the invention. That is, even the compounds having a conductivity and a viscosity out of the above range at 25 °C are employable as the electro-sensitive movable fluids, as far as the conductivity and the viscosity of the compounds are within the above range at their working temperatures. The electro-sensitive movable fluid does not particularly need to contain other substances, but additives such as stabilizer, high-molecular weight dispersant, surface active agent and high-molecular weight viscosity increasing agent may be added. Further, compounds having no ester linkage can be used as the electro-sensitive movable fluid, with the proviso that the conductivity and the viscosity of the compounds are located inside the above triangle. Next, the thin SE type ECF motor using the electro-sensitive movable fluid is described. Fig. 2(A) schematically shows a section of the thin SE type ECF motor of the invention. Fig. 2(B) is a sectional view taken on line X-X of Fig. 2(A). Fig. 3(D) is a sectional view taken on line Y-Y of Fig. 2(A). Fig. 3(C) is a schematic perspective view of a rotator. The thin SE type ECF motor of the invention has a container 44 (bottomed fluid container) to be filled with an electro-sensitive movable fluid and a lid 41 which is engaged with the open top to close the fluid container 44. When the lid 41 is engaged with the upper open part of the fluid container 44, the lid 41 and the fluid container 44 constitute a closed housing 40. The fluid container 44 for constituting the housing 40 has a bottom and is generally made of a material which is corrosion resistant to the electro-sensitive movable fluid filled therein. Examples of such materials include synthetic resins, such as polyolefins (e.g., polyethylene and polypropylene), Teflon™, polycarbonate, acrylic resin and other engineering plastics; ceramics; woods; metals; and glasses. The fluid container 44 can be formed from a conductive material such as metal (e.g., stainless steel). The fluid container 44 formed from a conductive material is preferably subjected to electrical insulation treatment so as not to mar the insulated state between the electrodes, or the fluid container 44 is preferably formed from an insulating material. The lid 41 is provided so as to close the open top of the medium container 44. The center of the lid 41 is provided with an upper bearing section 46 by which a rotating shaft 45 is rotatably borne. A lower bearing section 48 is provided at the center of a bottom 49 of the housing 40 to bear the lower end of the rotating shaft. In the housing 40, a rotator 30 is incorporated. The rotator 30 is arranged so as to be rotated in the housing 40 together with the rotating shaft 45. The rotator 30 is rotated by virtue of a jet flow of the electro-sensitive movable fluid 21 filled in the housing 40. In the present invention, the rotator 30 is formed from a material which is corrosion resistant to the electro-sensitive movable fluid filled in the fluid container. Examples of such materials include synthetic resins, such as polyolefins (e.g., polyethylene and polypropylene), Teflon™, polycarbonate, acrylic resin and other engineering plastics; ceramics; woods; metals; and glasses. In the SE type ECF motor, electrodes 50 a,b are provided on the lower surface of the lid 41 for constituting the housing 40 and/or the inner surface of the bottom of the fluid container 44. In Figs. 2(A), 2(B) and 3(D), a SE type ECF motor wherein the electrodes 50 a,b are provided on both of the lower surface of the lid 41 and the upper surface of the bottom of the medium container 44 is shown. The electrodes 50 a,b may be provided on both of those surfaces as described above, or they may be provided on one of the lower surface of the lid 41 and the upper surface of the bottom of the fluid container 44. When the electrodes are arranged in such a manner that an ununiform electric field is formed in the electro-sensitive movable fluid and a voltage is applied between the electrodes, a jet flow of the electro-sensitive movable fluid is produced. Each of Fig. 2(B) and Fig. 3(D) shows an embodiment wherein four positive electrodes 50a are arranged radially from the center of the housing in such a manner that the angle between the adjacent positive electrodes becomes 90° and four negative electrodes 50b are arranged in such a manner the angle between the negative electrode and the adjacent positive electrode becomes 22.5° The electrodes 50 a,b may be formed by stretching conductor wires, but it is preferable that the electrodes 50 a,b are formed by utilizing plating technique adopted in the preparation of printed circuit boards because the SE type ECF motor of the invention is extremely thin (e.g., height of housing: 2 mm or less). By the use of the plating technique, the thickness of the electrode 50 a,b can be made not more than 100 µm, preferably 0.1 to 50 µm. As described above, the electrodes 50 a,b are arranged in such a manner that an ununiform electric field is formed in the electro-sensitive movable fluid 21. There is no specific limitation on the number of the electrodes. The number thereof (total of positive electrodes and negative electrodes) is in the range of usually 2 to 48, preferably 2 to 36. The electrode 50 a,b is electrically connected to one end of a conductor 42 so that a voltage can be applied from the outside, and the other end of the conductor 42 is extended from the housing 40. When the electrodes 50 a,b are provided on both of the lower surface of the lid 41 and the upper surface of the bottom of the fluid container 44, a jet flow of the electro-sensitive movable fluid 21 is produced between the adjacent electrodes, because the rotator 30 is present between the upper electrode and the lower electrode and therefore a jet flow of the electro-sensitive movable fluid is hardly produced between the upper electrode and the lower electrode. That is, a jet flow of the electro-sensitive movable fluid is produced in the direction of an arrow as shown in each of Figs. 2(A), 2(B), 3(C) and 3(D). In the thin SE type ECF motor of the invention, the rotator 30 is rotated by the jet flow of the electro-sensitive movable fluid produced as above to thereby convert the electric energy applied to the electrodes to rotational energy which can be taken out. The rotator 30 is a circular plate fixed to the rotating shaft 45, and the surface of the circular plate is provided with a flow receiving member 31 to receive the jet flow of the electro-sensitive movable fluid and thereby rotate the circular plate. There is no specific limitation on the shape and the number of the flow receiving member 31, as far as the jet flow of the electro-sensitive movable fluid can be received. Each of Figs. 2(A), 2(B) and 3(C) shows an embodiment wherein six convex bars having a section of right-angled triangle are radially provided on each of the front and the back surfaces of the circular plate. In general, flow receiving members 31 of usually 2 to 30, preferably 3 to 20, are provided on the surface of the rotator 30, said surface facing the surface of the housing 40 where the electrodes 50 a,b are arranged. The convex bars each having a section of right-angled triangle are arranged in such a manner that a side of the triangle, which is at right angles to the jet flow of the electro-sensitive movable fluid 21, is at right angles to the rotator. The flow receiving member 31 can be provided so that this member protrudes from the circular plate (rotator 30) as described above, or it can be provided in the concave form if the circular plate has an appropriate thickness. The flow receiving member 31 functions as resistance to the jet flow of the electro-sensitive movable fluid 21 and rotates the rotator 30 together with the jet flow. Therefore, the flow receiving member 31 is not always a linear member such as the above-mentioned convex bar or concave line. For example, the member 31 may be a simple protrusion or a simple depression, or the surface of the circular plate can be processed to have high surface roughness. In each of Figs. 2(A), 2(B), 3(C) and 3(D), an embodiment wherein the rotator 30 is a flat circular plate is shown, but the rotator 30 can be modified to have a vertical section of any of various shapes such as inverse triangle, rhombus and circle. The center of the rotator 30 is fixed to the rotating shaft 45, and the rotating shaft 45 is rotatably fitted to housing 40. The rotator 30, the rotating shaft 45 and the optionally provided flow receiving member 31 are formed from materials which are corrosion resistant to the electro-sensitive movable fluid. Examples of such materials include synthetic resins, such as polyolefins (e.g., polyethylene and polypropylene), Teflon™, polycarbonate, acrylic resin and other engineering plastics; ceramics; woods; metals; and glasses. The rotator 30 is rotated in non-contact with the inner surface of the wall of the housing 40, and the ratio between the diameter of the housing 40 and the diameter of the rotator 30 can be appropriately determined. The electro-sensitive movable fluid between the outer periphery of the rotator 30 and the inner surface of the wall of the housing 40 is considered not to directly act on the rotational motion of the rotator 30, and hence the ratio between the diameter of the fluid container 44 for constituting the housing 40 and the diameter of the rotator 30 is in the range of preferably 100 : 99 to 100 : 50, particularly preferably 100 : 95 to 100 : 75. In Figs. 2(A) and 2(B), the diameter of the rotator is relatively small for convenience sake, but in the SE type ECF motor of extremely high efficiency, the diameter of the housing 40 and the diameter of the rotator 30 are so approximate that the rotator 30 is nearly in contact with the inner wall surface of the fluid container 41. The thickness of the rotator 30 (including a case where the flow receiving member is provided) is in the range of usually about 0.05 to 5 mm, preferably about 0.1 to 2 mm; the depth (i.e., distance between the upper surface of the bottom and the lower surface of the lid) of the housing 40 to be filled with the electro-sensitive movable fluid 21 is in the range of usually about 0.5 to 10 mm, preferably about 1 to 2 mm; and the ratio between the height of the fluid container 44 and the diameter of the rotator 30 is in the range of usually 1 : 1 to 1 : 500, preferably 1 : 2 to 1 : 50. The diameter of the housing 40 is in the range of usually about 3 to 50 mm, preferably about 5 to 25 mm, and the SE type ECF motor of the invention can be made extremely thin. Since the SE type ECF motor of the invention is extremely thin, the amount of the electro-sensitive movable fluid contained therein is about 0.05 to 10 ml and is very small. In the thin SE type ECF motor of the invention, the height of the housing can be made usually not more than 20 mm, preferably not more than 2 mm. In the thin SE type ECF motor, the height up to the tip of the rotating shaft can be made about 10 mm. Though the SE type ECF motor of the invention is extremely thin, the output power density represented by the ratio of torque/volume of the container is usually not less than 1 × 10 2 W/m 3 , and the SE type ECF motor can be driven with much higher efficiency by making the size smaller. Next, the thin RE type ECF motor is described. Fig. 4(A) is a sectional view of the RE type ECF motor, and Fig. 4(B) is a perspective view showing arrangement of the electrodes provided on the rotator. Fig. 5 shows another embodiment of the electrodes provided on the rotator. In the RE type ECF motor and the above-described SE type ECF motor, the elements in common are given the same reference numerals. In the thin RE type ECF motor of the invention, the basic constituents are the same as those of the SE type ECF motor, but in the RE type ECF motor, the electrodes are arranged on the rotator, differently from the SE type ECF motor. When a voltage is applied between the electrodes, a jet flow of the electro-sensitive movable fluid is produced, and by virtue of the reaction of the jet flow, the rotator is rotated. In the RE type ECF motor, a housing 40 is constituted of a fluid container 44 to be filled with an electro-sensitive movable fluid 21 and a lid 41. In the housing 40, a rotator 30 is arranged. The rotator 30 is fixed to a rotating shaft 45, and the rotating shaft 45 is rotatably fitted to the housing 40. In the RE type ECF motor, the electrodes are not provided on the inner surface of the housing 40 but provided on the surface of the rotator 30 as shown in Fig. 4(B). In more detail, in the RE type ECF motor, the rotating shaft 45 and the rotator 30 are united in one body, and the rotating shaft above the rotator 30 is coated with a conductive film 45a of a conductive metal. The conductive film 45a continues to the joint to the rotator 30 and is further extended radially and linearly on an upper surface 30a of the rotator 30 toward a rim 33 of the rotator 30 to form electrode 50a on the upper surface 30a of the rotator 30. The electrode 50a which has reached the rim 33 of the rotator 30 is then extended downward along the rim wall and reaches the lower surface (back surface) 30b of the rotator 30. The electrode 50a is further extended along the circumferential direction, then is bent before an electrode 50b on the back surface and is linearly extended in the axial direction, to form electrode 50a on the lower surface (back surface) 30b. On the other hand, the rotating shaft below the rotator 30 is coated with a conductive film 45b. The conductive film 45b continues to the joint to the rotator 30 and is further extended radially and linearly on the lower surface 30b of the rotator 30 toward a rim 33 of the rotator 30 to form electrode 50b on the lower surface 30b of the rotator 30. The electrode 50b which has reached the rim 33 of the rotator 30 is then extended upward along the rim wall and reaches the upper surface 30a of the rotator 30. The electrode 50b is further extended along the circumferential direction, then is bent before the linear electrode 50a on the upper surface and is linearly extended in the axial direction, to form electrode 50b on the upper surface 30a. The electrodes 50a and 50b are a positive electrode and a negative electrode, respectively, and they are electrically insulated from each other. Fig. 4(B) shows an embodiment wherein the positive electrodes 50a and the negative electrodes 50b are extended radially from the center of the rotator. In this RE type ECF motor, the electrodes are arranged in such a manner that an ununiform electric field is formed in the electro-sensitive movable fluid, whereby a jet flow of the fluid is produced. Therefore, there is no specific limitation on the arrangement of the electrodes and the shape thereof, as far as an ununiform electric field can be formed in the electro-sensitive movable fluid. For example, the positive electrodes 50a and the negative electrodes 50b can be arranged so that a pair of the electrodes 50a, 50b are nearly in parallel to each other as shown in Fig. 5. In this case, if a fluid which forms a jet flow in the direction of one electrode to the other electrode (direction of the positive electrode 50a to the negative electrode 50b in Fig. 5) is used as the electro-sensitive movable fluid, the electro-sensitive movable fluid forms a jet flow in the circumferential direction on the upper surface or the lower surface of the rotator 30 in the RE type ECF motor, and the'rotator 30 is rotated in the direction of the reaction of the jet flow (i.e., opposite direction to the direction of the jet flow). In the housing 40 of the RE type ECF motor of the invention, the rotating shaft 45 is borne by the upper bearing section 46 and the lower bearing section 48. Portions of the upper bearing section and the lower bearing section, which are brought into contact with the conductive film 45a and the conductive film 45b provided on the surface of the rotating shaft 45, are formed from a conductive material. These conductive material portions are connected to the conductors 42, 42 so that a voltage can be applied from the outside. Though the electrodes 50a, 50b and the conductive films 45a, 45b can be formed from various conductive materials, it is preferable that they are formed by utilizing plating technique adopted in the preparation of printed circuit boards in view of the RE type ECF motor of the invention being extremely thin and small. The electrodes 50a, 50b and the conductive film 45a, 45b are all extremely thin, and they have a thickness of usually 0.01 to 30 µm, preferably 0.1 to 15 µm. The upper bearing section 46 and the lower bearing section 48 both can be formed by bonding a conductive metal, or can be formed by utilizing plating technique similarly to the above. The bearing sections 46, 48 and the conductive films 45a, 45b formed on the surface of the rotational shaft 45 serve as contact points to supply a voltage. The bearing sections also serve as sliding points to rotate the rotator 30, and therefore they are preferably provided with friction reducing means such as ball bearing to inhibit decrease of rotational speed caused by friction between the bearing sections and the rotating shaft. In case of using plating technique, solid components such as graphite, molybdenum disulfide particles, Teflon™ particles and boron nitride (BN) particles, particularly solid lubricating components, are preferably added to the conductive materials containing gold, silver, copper or nickel, to reduce friction therebetween. When the conductive material has lubricating function or the solid lubricating component has conductivity, both of conducting properties and lubricating properties can be obtained by plating only one component out of the above. In Figs. 4(A) and 4(B), the rotator 30 is in the shape of a flat plate. However, the shape of the rotator is not specifically limited and can be appropriately determined. For example, the rotator may have a vertical section of inverse triangle as shown in Fig. 6(A), a vertical section of rhombus as shown in Fig. 6(B), or a vertical section of circle. The rotator 30 is rotated in non-contact with the inner wall surface of the housing 40, and the diametric ratio between the housing 40 and the rotator 30 can be appropriately determined. The electro-sensitive movable fluid 21 present between the outer periphery of the rotator 30 and the inner wall surface of the housing 40 is considered not to directly act on the rotational motion of the rotator 30, and hence the ratio between the diameter of the fluid container 44 for constituting the housing 40 and the diameter of the rotator 30 is in the range of preferably 100 : 99 to 100 : 50, particularly preferably 100 : 95 to 100 : 75. In Fig. 4(A), the diameter of the rotator 30 is relatively small for convenience sake, but in the RE type ECF motor of extremely high efficiency, the inner diameter of the fluid container 44 and the diameter of the rotator 30 are so approximate that the rotator 30 is nearly in contact with the inner wall surface of the fluid container 44. The thickness of the rotator 30 is in the range of usually about 0.05 to 5.0 mm, preferably about 0.1 to 1.0 mm, and the depth (i.e., distance between the upper surface of the bottom and the lower surface of the lid) of the housing 40 to be filled with the electro-sensitive movable fluid 21 is in the range of usually about 0.05 to 5.0 mm, preferably about 0.1 to 1.0 mm. In the thin RE type ECF motor of the invention, the ratio between the height of the rotator and the diameter of the rotator can be appropriately determined, and the ratio therebetween is in the range of usually 1 : 1 to 1 : 500, preferably 1 : 2 to 1 : 50. The RE type ECF motor of the invention can be made extremely thin. In the thin RE type ECF motor of the invention, the height of the housing 40 can be made usually not more than 20 mm, preferably not more than 2 mm, and the height up to the tip of the rotating shaft can be made about 10 mm. Though the RE type ECF motor of the invention is extremely thin, the output power density represented by the ratio of torque/volume of the container is usually not less than 1 × 10 2 W/m 3 , and the RE type ECF motor can be driven with much higher efficiency by making the size smaller. The thin micromotor of the invention may be the SE type ECF motor wherein the electrodes are arranged on the housing 40, the RE type ECF motor wherein the electrodes are arranged on the rotator 30, or a complex type thereof. As shown in Figs. 7(A), 7(B), 7(C), 7(D) and 7(E), the lower surface of the lid 41 of the housing 40 is provided with positive electrodes 50c and negative electrodes 50d, and the surface of the bottom of the housing 40 is provided with positive electrodes 50e and negative electrodes 50f. When the electrodes 50 c,d,e,f are arranged in the above way, a jet flow of the electro-sensitive movable fluid is produced predominantly between the adjacent positive and negative electrodes having a smaller distance. For example, if four positive electrodes are provided at an angle of 90° and if negative electrodes are each provided at an angle of 22.5° to the adjacent positive electrode, a jet flow of the electro-sensitive movable fluid 21 in the direction of the positive electrode to the negative electrode is generally produced. In this micromotor, a conductive film 45a is formed on the surface of the rotating shaft 45 above the upper surface 30a of the rotator 30 and a conductive film 45b is formed on the surface of the rotating shaft below the lower surface 30b of the rotator 30, similarly in the above-mentioned RE type ECF motor. Further, positive electrodes 50g and negative electrodes 50h extending from the rotating shaft 45 to the rim 33 are provided on the surfaces of the rotator 30, similarly in the above-mentioned RE type ECF motor. Since the angle between the positive electrode 50g and its negative electrode 50h is 22.5°, a jet flow of the electro-sensitive movable fluid 21 in the direction of the positive electrode 50g to the negative electrode 51h is produced between those electrodes. The thickness of the rotator 30 is relatively large, and rim electrodes 50j to connect the upper surface 30a of the rotator 30 to the lower surface 30b thereof are provided obliquely on the surface of the rim wall of the roator 30. Therefore, a jet flow of the electro-sensitive movable fluid is produced also by the rim electrodes 50j. In this micromotor, electrodes 50m and 50n which are adjacent to each other are provided also on the inner wall surface of the housing 40, so that a jet flow of the electro-sensitive movable fluid is produced also by the electrodes 50m and 50n. When the polarities of these electrodes are set in such a manner that the resulting jet flows of the electro-sensitive movable fluid are in one direction, the fluid can be moved at a higher velocity because of the resulting jet flows in one direction, and thereby the rotator 30 may be rotated at a higher rotational speed. As shown in Fig. 8, the micromotor of the invention can include plural rotators 30 in the fluid container 44. Fig. 8 shows an embodiment of the RE type ECF motor wherein three rotators 30 are fixed to the rotating shaft 45 and are rotatable in the housing 44. The micromotor of the invention has a housing height of usually not more than 20 mm and is extremely thin. By properly selecting arrangement of the electrodes, a material of the rotator, etc., the height of the housing can be decreased to not more than 2 mm. Though the micromotor of the invention is extremely thin, it can be stably driven at a high rotational speed of about several hundreds to several tens of thousands rpm. The micromotor according to the invention are driven by filling an electro-sensitive movable fluid in a fluid container and applying a direct-current-voltage of usually 50 V to 15 kV, preferably 100 V to 10 kV, more preferably 100 V to 6 kV. The current given by application of a voltage is usually not more than 100 µA, preferably 0.1 to 50 µA, particularly preferably 0.5 to 10 µA, so that the power consumption is extremely small. Further, since the current is extremely small, heat is hardly generated from the micromotor. Furthermore, since the micromotor do not utilize magnetic force or magnetic field but utilize a jet flow of the electro-sensitive movable fluid produced in an electric field, they are normally driven even in a strong magnetic field and generate none of magnetism, driving noise and electromagnetic noise. EFFECT OF THE INVENTION The micromotor of the invention is extremely small, and the thin micromotor of the invention is extremely thin. In spite of the small or thin micromotor, it can be driven at a high rotational speed of several hundreds to several tens of thousands rpm. The micromotor of the invention hardly generates heat even when it rotates at a high speed. The micromotor of the invention utilize jet flow of an electro-sensitive movable fluid produced in an electric field, not but magnetic force or magnetic field, and therefore they are normally driven even in a strong magnetic field and generate none of magnetism, driving noise and electromagnetic noise. EXAMPLE The present invention is further described with reference to the following examples, but it should be construed that the invention is in no way limited to those examples. Example 1 A SE type ECF motor having a structure shown in Fig. 2(A) was fabricated. That is, as a fluid container of the SE type ECF motor, a cylinder having an inner diameter of 16 mm and a depth of 3.5 mm was used. The bottom surface of the cylinder and the lower surface of alid each was provided with four pairs of electrodes in such a manner that the angle between a pair of electrodes (positive electrode and negative electrode) was 22.5° and the angle between the adjacent positive electrodes was 90°. A circular film having a rotating shaft at its center and having a diameter of 15 mm was used as a rotator. As the flow receiving members, 8 convex bars each having a section of right-angled triangle were attached to the upper surface of the circular film, and 8 convex bars having the same section as above were attached to the lower surface of the circular film (total number of bars: 16). The fluid container was filled with 16 ml of dibutyl decanedioate (DBD). Then, a direct-current-voltage of 6.0 kV was applied between the electrodes of the thus fabricated SE type ECF motor. As a result, the rotator of the SE type ECF motor underwent steady rotation at 510 rpm, and the rotator (SE type ECF motor) continued to rotate stably during the application of a voltage. The intensity of the current in DBD was 2.0 µA, and the rotational direction was the same as the flow direction of DBD (i.e., direction of the positive electrode to the negative electrode). When the polarities of the electrodes between which the voltage was applied were reversed, the rotator 30 rotated at the same rotational speed in the opposite direction, and the intensity of the current was the same as above. Example 2 The SE type ECF motor was driven in the same manner as in Example 1, except that the rotator having a flow receiving member consisting of 16 convex bars was replaced with a rotator having a flow receiving member consisting of 8 convex bars (4 convex bars each having a section of right-angled triangle attached to the upper surface and 4 convex bars having the same section attached on the lower surface). As a result, the SE type ECF motor underwent steady rotation at 340 rpm, and the rotational direction was the same as in Example 1. Example 3 The SE type ECF motor was driven in the same manner as in Example 1, except that linalyl acetate was used in place of the dibutyl decanedioate (DBD). As a result, the SE type ECF motor underwent steady rotation at 740 rpm, the intensity of the current was 1.8 µA, and the rotational direction was the same as the flow direction of the linalyl acetate (i.e., direction of the positive electrode to the negative electrode). Example 4 The SE type ECF motor was driven in the same manner as in Example 1, except that dibutyl dodecanedioate was used in place of the dibutyl decanedioate (DBD). As a result, the SE type ECF motor underwent steady rotation at 480 rpm, the intensity of the current was 1.8 µA, and the rotational direction was the same as the flow direction of the dibutyl dodecanedioate (i.e., direction of the positive electrode to the negative electrode). Example 5 An engineering plastic (insulating material) was cut to prepare a rotator having a diameter of 19 mm and a thickness of 1.0 mm. The rotator had at its center a rotating shaft (diameter: 1.0 mm) united to the rotator in one body. The united product of the rotator and the rotating shaft was provided with electrodes by means of electroless nickel plating, as shown in Fig. 5. The electrodes had a thickness of 5 µm. The united product consisting of the rotator and the rotating shaft and provided with the electrodes was incorporated in a housing having an inner diameter of 22 mm and a depth of 4 mm, as shown in Fig. 4(A), and the housing was filled with 1 ml of dibutyl decanedioate (DBD). Then, a direct-current-voltage of 6.0 kV was applied between the electrodes of the thus fabricated RE type ECF motor. As a result, the rotator of the RE type ECF motor underwent steady rotation at 320 rpm, and the rotator (RE type ECF motor) continued to rotate stably during the application of a voltage. The intensity of the current in DBD was 1.5 µA, and the rotational direction was a direction of the reaction of the jet flow produced between the electrodes provided on the rotator. When the polarities of the electrodes between which the voltage was applied were reversed, the rotator rotated at the same rotational speed in the opposite direction, and the intensity of the current was the same as the above. Example 6 The RE type ECF motor was driven in the same manner as in Example 5, except that linalyl acetate was used in place of the dibutyl decanedioate (DBD). As a result, the RE type ECF motor underwent steady rotation at 440 rpm, and the intensity of the current was 1.4 µA. Example 7 The RE type ECF motor was driven in the same manner as in Example 5, except that dibutyl dodecanedioate was used in place of the dibutyl decanedioate (DBD). As a result, the RE type ECF motor underwent steady rotation at 300 rpm, and the intensity of the current was 1.5 µA.

Claims: A micromotor (40) comprising a container (44) to be filled with an electro-sensitive movable fluid, a lid (41) to close the container (44) by being engaged with the open top of the container (44), a rotating shaft (45) borne by a shaft hole provided at the center of the lid (41) and a bearing section (48) provided at the center of the bottom of the container (44), a rotator (30) fixed to the rotating shaft (45) and rotatable together with the rotating shaft (45), and electrodes (50a, b) which produce a jet flow of the electro-sensitive movable fluid upon application of a voltage, wherein the diameter of the rotator is larger than the maximum thickness of the rotator, characterized in that the electrodes (50a, b) are arranged on the upper surface of the bottom of the container (44) and/or the lower surface of the lid (41) of the container (44) in such a manner that the electrodes are in contact with the electro-sensitive movable fluid, or wherein the electrodes are arranged on the upper surface of the rotator (30) and/or the lower surface of the rotator (30). The micromotor as claimed in claim 1, wherein the electrodes (50a, b) are arranged in such a manner that an ununiform electric field is formed in the electro-sensitive movable fluid. The micromotor as claimed in claim 1, wherein the electrodes (50a, b) are at least one pair of electrodes which are different in the polarity and are parallel to each other. The micromotor as claimed in claim 1, wherein the ratio between the height of the container (44) and the diameter of the rotator (30) is in the range of 1 : 1 to 1 : 500. The micromotor as claimed in claim 1, wherein the output power density indicated by the ratio of torque of the micromotor/volume of the container is not less than 1 x 10 2 W/m 3 .

Inventors: EDAMURA KAZUYA, NAKADA TAKESHI, OTSUBO JASAFUMI, YOKOTA SHINICHI, EDAMURA, KAZUYA, NAKADA, TAKESHI, OTSUBO, JASAFUMI, YOKOTA, SHINICHI, Nakada, Takeshi 461-11-503 Eda-cho, Yokota, Shinichi 1941-B1-301
Applicants: NEW TECHNOLOGY MAN CO LTD, NEW TECHNOLOGY MANAGEMENT CO., LTD.
Application year: 1998
Main classification: F15B21
IPC codes: F15C1, F15B21, H02N11, F15C5, H01J41, F16K99