JP2005143177A - Actuator utilizing ehd phenomenon - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lightweight actuator capable of high speed driving by utilizing EHD phenomenon. <P>SOLUTION: Electric response gas is generated by dripping electric response fluid into a housing 20 and volatilizing the fluid and then the electric response gas is interposed between an annular electrode 30 and a rotary electrode 40. Subsequently, a voltage is applied between both electrodes 30 and 40 from a voltage applying section 50 to generate a nonuniform electric field between both electrodes 30 and 40. The rotary electrode 40 is rotated through reaction based on dynamic movement, i.e. EHD phenomenon of the electric response gas. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an actuator using a so-called EHD phenomenon (Electro Hydro Dynamics Phenomenon). Here, the EHD phenomenon means that when an electrode is inserted into some kind of electrically insulating fluid (electrically responsive fluid) such as xylene, chloroform, silicon oil, and machine oil, and a high voltage is applied thereto, the electrically responsive fluid is generated between the electrodes. This is a phenomenon in which mechanical phenomena such as diffusion and stirring occur.

  In recent years, research on small devices and biomedical devices intended for use in an environment where humans coexist, such as medical care and welfare, has been vigorously conducted. As actuators for driving these devices, recently, actuators that are friendly to humans, such as light weight, small size, and flexibility, have been required. An actuator that utilizes the so-called EHD phenomenon has attracted attention as a means that can meet such a demand (see, for example, Non-Patent Document 1). This Non-Patent Document 1 discloses an actuator in which a first electrode and a second electrode that is movable relative to the first electrode are immersed in an electrically responsive fluid as a liquid.

Akihiro Komiyama, Sumitaka Terasaka, Shin Inada, Kazuyuki Mitsui, Shinichi Kuroda, Hiroshi Abe, Atsuko Niizuma, Go Saito: “Development of Actuators Using EHD Phenomenon”, 21st Annual Conference of the Robotics Society of Japan (2003)

Any of the electrically responsive fluids used in the actuator utilizing the conventional EHD phenomenon is a liquid. In the case of a liquid, since the resistance during rotation is large, there is a problem that a sufficient number of rotations cannot be obtained. In addition, there is a problem that the weight of the actuator increases due to an increase in the amount of liquid.
An object of the present invention is to provide an actuator that utilizes the EHD phenomenon and is lightweight and capable of high-speed driving.

  In order to achieve the above object, the inventors of the present application considered to construct an actuator using the EHD phenomenon generated in a certain kind of insulating gas. As shown in FIG. 1, an electrical response fluid 12 was injected into the container 11, and an environment was prepared in which the interior of the container was filled with an electrical response gas 13 generated by volatilization of the electrical response fluid 12. The electrically responsive fluid 12 here is an electrically responsive liquid or the like which has an ether bond and has been subjected to a discharge treatment containing a halogen element as described in Japanese Patent Application No. 2002-227741 filed earlier by the applicant. Reference numeral 13 denotes a gas obtained by volatilizing the electric response fluid 12 as the liquid. Moreover, it is preferable that the electrical response gas 13 has fluorine or sulfur as a component and has a high electronegativity. Since these liquids have high volatility at normal temperature and normal pressure, the container 11 may be placed in normal temperature and normal pressure.

  A linear electrode 14 is arranged in the electric response gas 13 and a plate electrode 15 is arranged in the electric response fluid 12, and a high voltage (several [kV] or more) is applied between the linear electrode 14 and the plate electrode 15. As a result, an unequal electric field (referred to as an electric field having different intensities depending on the position between the electrodes, which is generated when electrodes having different shapes or different materials are arranged to face each other) is applied between the electrodes. An active air flow 16 of the electric response gas 13 is generated from the flat plate electrode 15 toward the flat electrode 15. The air flow 16 is such an active flow that the liquid level of the electrical response fluid 12 is recessed. Although the generation principle has not been fully elucidated, it is thought that ionic drag may be a cause. That is, it is considered that gas molecules in the vicinity of the anode are charged with a positive charge and attracted to the anode, thereby causing a flow between the electrodes. Moreover, it is thought that the magnitude | size and direction of the airflow 16 differ with the difference in the property of gas, or how to make an unequal electric field. Even if the gas in the container 11 is air, for example, the EHD phenomenon can be caused to some extent. However, in the case of air or the like, the insulation between the electrodes 14 and 15 is not sufficient, and a sufficiently strong air flow 16 cannot be obtained. Therefore, the electric response gas 13 is selected from materials that can obtain an air flow 16 having a desired strength.

  The present invention provides an actuator using such a mechanical motion based on the EHD phenomenon of an electrically responsive gas. That is, the actuator using the EHD phenomenon according to the present invention is configured to generate an unequal electric field between the first electrode and the first electrode, and to move relative to the first electrode. A voltage is applied between the second electrode, a container that houses the first and second electrodes, an electrically responsive gas housed in the container, and the first and second electrodes And a voltage applying means.

  According to the present invention, the electrically responsive gas is supplied between the first electrode and the second electrode, and the second electrode moves relative to the first electrode by the mechanical movement of the electrically responsive gas. . For this reason, the weight of the actuator is light, the resistance to the relatively moving electrode is small, and high-speed driving is possible.

Next, embodiments of the present invention will be described in detail with reference to the drawings.
Here, as an actuator, a rotary actuator in which the second electrode is rotationally driven with respect to the first electrode will be described as an example.
As shown in a plan view (a) and a side sectional view (b) in FIG. 2, the rotary actuator includes a housing 20, an annular electrode 30, a rotary electrode 40, a voltage applying unit 50, and an electric response fluid supply. Part 60. The housing 20 is for confining an electrically responsive gas that generates an EHD phenomenon and supplying the electrically responsive gas between the annular electrode 30 and the rotating electrode 40. Here, the housing 20 is formed using acrylic as a material, and the size thereof is 100 [mm] in diameter and 60 [mm] in height.
The annular electrode 30 is provided on the inner wall side surface 20b of the housing 20 using, for example, aluminum or the like as a material.

  On the other hand, the rotating electrode 40 includes a rotating shaft 41 penetrating through the vicinity of the center position of the annular electrode 30 of the upper lid 20 u of the housing 20. The rotating shaft 41 is rotatably held by the upper lid 20 u by the bearing 21. Yes. Here, the length and shaft diameter of the rotating shaft 41 are 50 [mm] and φ3 [mm], respectively. The diameter of the bearing 21 is φ3 [mm]. An arm portion 42 is attached to the rotating shaft 41 so as to extend in the horizontal direction, and a boom portion 43 that extends at a right angle to the arm portion 42 is extended at the tip of the arm portion 42. Here, it is assumed that the arm part 42 and the boom part 43 are made of stainless steel, and their lengths are 10 [mm] and 20 [mm], respectively.

  The voltage application unit 50 applies a DC voltage between the annular electrode 30 and the rotating electrode 40, and the voltage generated by the voltage generation unit 51 is supplied to both electrodes 30 and 40 by connection lines 52 and 53. Is done. The magnitude of the voltage generated from the voltage generator 51 is controlled by the controller 54.

  The electrical response fluid supply unit 60 is for dropping the electrical response fluid as described above into the housing 20. The dropped electrically responsive fluid volatilizes and is provided between the electrodes 30 and 40 in the housing 20 as an electrically responsive gas. In the present embodiment, since the electrical response gas leaks from the gaps of the bearing 21 and the like little by little, it is assumed that a predetermined amount of electrical response fluid is dropped at regular intervals.

In such a configuration, when the electrical response fluid dropped from the electrical response fluid 50 is volatilized and a voltage is applied to the electrodes 30 and 40 from the voltage application unit 50, an electrical response is generated from the rotating electrode 40 toward the annular electrode 30. An active gas flow A is generated, and the reaction causes the rotating electrode 40 to rotate in a direction opposite to the air flow A (in the direction of arrow B). By taking out this rotational force as external power, a rotary actuator can be configured.
Such an air flow A is generated somewhat regardless of the gas in the housing 20, for example, a certain amount of air flow is generated even with air. However, in the case of air or the like, when the voltage between the electrodes 30 and 40 reaches about 10 [kV], discharge starts to occur, and sufficient rotation speed and torque for practical use cannot be obtained. Therefore, in order to obtain a sufficient rotational speed and torque, it is necessary to select an appropriate electric response gas and keep its concentration in an appropriate state.

    In the rotary actuator configured as described above, the electric response fluid was dropped and volatilized in the housing 20 maintained at normal temperature and normal pressure, and then the voltage applied by the voltage application unit 50 was gradually changed. And the change of the rotation speed of the rotating electrode 40 at that time (no load) and the change of the current value between the electrodes 30 and 40 were measured. The result is shown in the graph of FIG. The rotating electrode 40 was grounded, and 0 to 24 [kV] or 0 to −24 [kV] was applied from the voltage applying unit 50 to the annular electrode 30 side. The figure (a) is a graph when the applied voltage is a positive voltage of 0 to 24 [kV], and the figure (b) is a negative voltage of 0 to -24 [kV]. It is a graph of the case. The rotational speed was measured using a reflector (not shown) attached to the rotary shaft 41 and an optical tachometer.

  As shown in FIG. 3A, when the applied voltage was a positive voltage, the rotating electrode 40 started rotating and the current began to flow when the applied voltage became around 6 [kV]. As the applied voltage increased, both the rotation speed and current increased. However, the increase rate (gradient of the graph) started to decrease when the applied voltage exceeded 18 [kV], and the rotation number hardly increased when the applied voltage exceeded 20 [kV]. The rotation speed when the applied voltage reached 24 [kV] at maximum was 4100 [rpm]. On the other hand, the increase in the current value did not decrease even when the applied voltage was 20 [kV] or higher, but rather increased, and the current value when the applied voltage was 24 [kV] was about 200 [μA].

  As shown in FIG. 3B, when the applied voltage was a negative voltage, the rotating electrode 40 started rotating and the current began to flow when the applied voltage became around −8 [kV]. As the applied voltage increased, both the rotation speed and current increased. As in the case where the applied voltage is positive, the rate of increase in the rotation speed (gradient of the graph) started to decrease when the applied voltage exceeded −18 [kV]. The degree of decrease was not as pronounced as in the case of a positive applied voltage, and the rotational speed continued to increase. The number of rotations when the applied voltage reached a maximum of −24 [kV] was 5100 [rpm], which was larger than in the case of the positive applied voltage. On the other hand, the increase rate of the current value hardly decreased even when the applied voltage became −20 [kV] or more, and the current value continued to increase. The current value when the applied voltage was −24 [kV] was about 200 [μA].

Further, in the rotary actuator configured as described above, after the electric response fluid is dropped and volatilized in the housing 20 maintained at room temperature and normal pressure, the voltage applied by the voltage application unit 50 is gradually changed. . Then, the maximum torque change (at the maximum load) of the rotating electrode 40 and the current value change between the electrodes 30 and 40 were measured. The result is shown in the graph of FIG.
The voltage applied from the voltage application unit 50 was such that the rotating electrode 40 was grounded, and the voltage applied to the annular electrode 30 was changed between 0 to 24 [kV] and 0 to −24 [kV]. FIG. 4 (a) is a graph when the applied voltage is a positive voltage of 0 to 24 [kV], and FIG. 4 (b) is a negative voltage of 0 to −24 [kV]. It is a graph of the case.

As shown in FIG. 4A, when the applied voltage is a positive voltage, the rotating electrode 40 starts to generate torque and the current starts to flow when the applied voltage is in the vicinity of 8 [kV]. . As the applied voltage increased, both torque and current increased. However, the increase rate (gradient of the graph) of the torque became almost zero after the applied voltage became around 20 [kV]. The torque when the applied voltage reached a maximum of 24 [kV] was 0.3 [μNm]. On the other hand, the increase rate of the current value did not decrease even when the applied voltage was 20 [kV] or more, and the current value when the applied voltage was 24 [kV] was about 140 [μA].
Further, as shown in FIG. 4B, when the applied voltage is a negative voltage, the rotating electrode 40 starts generating torque and the current is also generated when the applied voltage is in the vicinity of −9 [kV]. Began to flow. As the applied voltage increased, both torque and current increased. Unlike the case where the applied voltage was positive, the increase rate (gradient of the graph) did not decrease even when the applied voltage exceeded −20 [kV], and the torque continued to increase. Even when the applied voltage exceeded −20 [kV], the increase rate did not decrease and the current value continued to increase. The torque when the applied voltage reached a maximum of −24 [kV] was 0.5 [μNm], which was slightly larger than in the case of the positive applied voltage. On the other hand, the current value was about 150 [μA] when the applied voltage was −24 [kV].

FIG. 5 shows the relationship between the torque and the rotational speed of the rotary actuator shown in FIG. 2 (FIG. 5A) and the torque and current using the data at the applied voltage 24 [kV] shown in FIGS. The relationship (FIG. 5B) was expressed. 5 (a) and 5 (b), only the values at both ends are measured in each graph, but in both graphs, the graph is descending to the right. This indicates that the rotary actuator of FIG. 2 has a characteristic that the number of rotations decreases when the torque increases, and a characteristic that the current between the electrodes 30 and 40 decreases when the torque increases. The former characteristic is the same as that of a general electromagnetic motor, but the latter characteristic is different from that of a general electromagnetic motor.
In a general electromagnetic motor, the current increases when the load increases, and further, when the overload state continues, heat is generated and the motor may be destroyed. For this reason, motor control to avoid this is necessary. On the other hand, the rotary actuator of FIG. 2 has a characteristic that the current decreases as the load increases, so that no special control is required even if an overload condition occurs. This point is considered to be a great advantage when designing a drive system.
Further, since the rotary actuator shown in FIG. 2 uses the gas EHD phenomenon in the housing 20, the installation direction and position of the actuator can be selected relatively freely as compared with the conventional actuator using the liquid EHD phenomenon. Can do.
When the gas in the housing 20 is only air, the rotational speed does not increase as shown in FIG. 3, and discharge starts when the applied voltage reaches around 10 [kV], and the current value increases rapidly. I stopped working as an actuator. 6 and 7 are graphs showing the state. 6 (a) and 7 (a) show the rotation speed and current when the applied voltage is positive, respectively, and FIGS. 6 (b) and 7 (b) show the case where the applied voltage is negative. The rotation speed and current at are shown.

As mentioned above, although embodiment of invention was described, this invention is not limited to these. For example, the shape of the rotary electrode 40 of the rotary actuator may be a shape as shown in FIG. In the rotary actuator shown in FIG. 8, the rotary electrode 40 includes arm portions 44 and 45 connected to the rotary shaft 41, and a blade electrode 46 attached to the tips of the arm portions 44 and 45.
Further, as shown in FIG. 9, a large number of linear electrodes 31 are provided so as to protrude from the inner wall side surface 20 b of the housing 20 instead of the annular electrode 30, and a flat plate electrode 48 is provided at the tip of the arm portion 47 of the rotating electrode 40. May be provided. With such a configuration, an air flow from the linear electrode 31 toward the flat plate electrode 48 is generated, and the rotating electrode 40 is rotated by the reaction of the air flow.
In the above-described embodiment, the rotating electrode as the second electrode rotates with respect to the annular electrode 30 as the first electrode. However, the second electrode may be anything that moves relative to the annular electrode 30. In addition to rotation, parallel movement or the like may be performed.

It is a principle figure explaining the EHD phenomenon by gas. 1 shows a rotary actuator according to an embodiment of the present invention. The relationship between the applied voltage of the rotary actuator shown in FIG. 2, the number of rotations of the rotating electrode 40 (at the time of no load), and the current value between the electrodes 30 and 40 is shown. The relationship between the applied voltage of the rotary actuator shown in FIG. 2, the maximum torque (at the maximum load) of the rotating electrode 40, and the current value between the electrodes 30 and 40 is shown. The relationship between the torque and rotation speed of the rotary actuator shown in FIG. 2 and the relationship between torque and current are shown. In the rotary actuator shown in FIG. 2, the change in the number of rotations of the rotary electrode 40 when the gas in the housing 20 is only air is shown. In the rotary actuator shown in FIG. 2, a change in the current value when the gas in the housing 20 is only air is shown. The modification of the rotary actuator which concerns on embodiment of this invention is shown. The modification of the rotary actuator which concerns on embodiment of this invention is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Container, 12 ... Electrical response fluid, 13 ... Electrical response gas, 14 ... Linear electrode, 15 ... Flat plate electrode, 14 ... Linear electrode, 15 ... Flat plate Electrode 16 ... Airflow 20 ... Housing 21 ... Bearing 30 ... Ring electrode 31 ... Linear electrode 40 ... Rotating electrode 41 ... Rotating shaft 42 ... Arm part, 43 ... Boom part, 44, 45, 47 ... Arm part, 46 ... Blade electrode, 48 ... Open electrode, 50 ... Voltage application part, 51 ...・ Voltage generator, 52, 53... Connection line, 54... Controller, 60.

Claims (4)

A first electrode;
A second electrode configured to generate an unequal electric field between the first electrode and move relative to the first electrode;
A container that houses the first and second electrodes;
An electrically responsive gas contained within the container;
An actuator using an EHD phenomenon, comprising: voltage applying means for applying a voltage between the first and second electrodes.   The actuator using the EHD phenomenon according to claim 1, wherein the electric response gas is generated by volatilizing an electric response fluid having volatility and insulation. The first electrode is an annular electrode;
3. The actuator using the EHD phenomenon according to claim 1, wherein the second electrode is a linear electrode configured to rotate around a central position of the annular electrode as a rotation axis.   The actuator using the EHD phenomenon according to claim 1, wherein the electrically responsive gas includes at least one of fluorine and sulfur.

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