JP2005143223A - Electrostatic actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic actuator which can control the position of a mobile unit at current application even in case that the position of the mobile unit becomes unsettled at current nonapplication. <P>SOLUTION: This electrostatic actuator possesses a stator (1) which has a plurality of driving electrodes on its surface, a mobile unit (2) which can relatively shift to the stator and has a plurality of electret sections, a protecting member which is arranged to catch the mobile with the stator, a pulse generating circuit (12) which outputs a drive pulse signal for driving the mobile, a driving circuit (14) which applies polyphase AC voltage to the driving electrode, based on a drive pulse from the pulse generating circuit, and mechanical or electrical stoppers (36, 37) which are arranged in the positions on the stator corresponding to the initial position of the mobile unit. The pulse generating circuit outputs an initializing pulse signal for driving the mobile unit until it reaches the stopper after power ON. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electrostatic actuator using an electret as a moving element.

An electrostatic actuator using an electret as a mover can reduce the weight of the mover, and can move the mover at a high speed with a low voltage (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 4-112683

  In the electrostatic actuator described in Patent Document 1, if a voltage is applied between the electrodes, the movable element is held at that position even when an external force is applied. However, since no voltage is applied between the electrodes during non-energization, the position of the mover may become unstable when an external force is applied.

  For this reason, even if the power is turned on, it is difficult to start position control because it is uncertain where the moving element is. Therefore, when the electrostatic actuator is used as a shutter mechanism or a movable mirror of a camera, it cannot be put into practical use unless the above problems are solved.

  The present invention has been made in view of such circumstances, and is an electrostatic that can control the position of the mover when energized even when the position of the mover becomes indefinite when deenergized. An object is to provide an actuator.

  An electrostatic actuator according to a first aspect of the present invention includes a stator having a plurality of driving electrodes on the surface, and a plurality of electretized parts that are movable relative to the stator. A moving member; a protective member arranged to sandwich the moving member with the stator; a pulse generating circuit for outputting a driving pulse signal for driving the moving member; and a driving pulse signal from the pulse generating circuit A driving circuit for applying a polyphase AC voltage to the driving electrode, and a mechanical or electrical stopper disposed at a position on the stator corresponding to the initial position of the moving element; The pulse generation circuit outputs an initialization pulse signal for driving the movable element until it reaches the stopper after power is turned on.

  The electrostatic actuator according to a second aspect of the present invention is the electrostatic actuator according to the invention described above, wherein the mechanical stopper is a spacer fixed between the stator and the protective member. .

  The electrostatic actuator according to a third aspect of the present invention is the electrostatic actuator according to the above-described invention, wherein the electrical stopper is an electret member.

  The electrostatic actuator according to a fourth aspect of the present invention is the electrostatic actuator according to the above-described invention, wherein the pulse generation circuit has a predetermined value corresponding to a maximum movement amount of the moving element as the initialization pulse signal. Output a number of pulses.

  The electrostatic actuator according to claim 5 of the present invention is the electrostatic actuator according to the invention described above, wherein the pulse generation circuit outputs the initialization signal pulse for a predetermined time.

  The electrostatic actuator according to a sixth aspect of the present invention is the electrostatic actuator according to the above-described invention, wherein the driving circuit is configured to drive the driving element after the driving of the moving element to the initial position is completed. A constant voltage is applied to the electrode.

  An electrostatic actuator according to a seventh aspect of the present invention includes a stator having a plurality of driving electrodes on the surface, a relative movement with respect to the stator, and a plurality of electretized portions. A movable member having a movable member, a protective member disposed so as to sandwich the movable member with the stator, a pulse generating circuit for outputting a driving pulse signal for driving the movable member, and a driving pulse from the pulse generating circuit. A driving circuit for applying a polyphase AC voltage to the driving electrode based on a signal; and a detecting means for detecting that the moving element has reached an initial position. The pulse generating circuit is turned on. After that, an initialization pulse signal is output until it is detected by the detection means that the moving element has reached the initial position.

  An electrostatic actuator according to an eighth aspect of the present invention is the electrostatic actuator according to the above-described invention, wherein the pulse generation circuit outputs the initialization pulse signal according to the detection output of the detection means. To stop.

  The electrostatic actuator according to a ninth aspect of the present invention is the electrostatic actuator according to the above-described invention, wherein the detection means is a detection electrode provided at a position on the stator corresponding to the initial position. And a monitor circuit that is connected to the detection electrode and detects a change in capacitance when the electret portion of the moving element comes close to the detection electrode and supplies a trigger signal to the pulse generation circuit.

  The electrostatic actuator according to a tenth aspect of the present invention is the electrostatic actuator according to the above-described invention, wherein the detection means is disposed at a position corresponding to the initial position on the protection member and the stator. When the electretized portion of the moving element comes close between the two detection electrodes and the two detection electrodes, a change in capacitance between the two detection electrodes is detected and a trigger signal is supplied to the pulse generation circuit Monitoring circuit.

  An electrostatic actuator according to an eleventh aspect of the present invention is the electrostatic actuator according to the above-described invention, wherein the detection means includes a first conductive member provided at one end of the moving element, and the initial stage. A trigger signal to the pulse generation circuit when the first and second conductive members are in contact with the second and third conductive members provided at positions on the stator corresponding to the positions; And a monitor circuit for supplying

  The electrostatic actuator according to a twelfth aspect of the present invention is the electrostatic actuator according to the above-described invention, wherein the detection means is a detection element provided at a position on the stator corresponding to the initial position. And a monitor circuit that is connected to the detection element and detects a change in current when a magnetic body provided on the moving element comes close to the detection element and supplies a trigger signal to the pulse generation circuit.

  The electrostatic actuator according to a thirteenth aspect of the present invention is the electrostatic actuator according to the above-described invention, wherein the driving circuit is configured to drive the driving element after the driving of the moving element to the initial position is completed. A constant voltage is applied to the electrode.

  According to the electrostatic actuator of the present invention, it is possible to control the position of the mover during energization even when the position of the mover becomes indefinite during deenergization.

  FIG. 1 is a view showing a shutter mechanism of a shutter device to which an electrostatic actuator according to the present invention is applied. (1) in FIG. 1 shows a state in which the shutter is open, and (2) in FIG. 1 shows a state in which the shutter is closed.

  The shutter mechanism includes a stator 1 and a mover 2, and the mover 2 is configured to be movable in the left-right direction with respect to the stator 1. The stator 1 is provided with an opening 3 for guiding a light image from a subject to an image sensor (not shown), and a plurality of strip-like drive electrodes 4 are arranged at a predetermined interval.

  The mover 2 is a light-shielding member, has a part of a permanent polarized derivative (hereinafter referred to as “electret”), which will be described later, and receives a driving force from the charge of the drive electrode 4 to move relative to the stator 1. I do. The opening 3 is not necessarily required for the stator 1. The stator 1 is used as a transmissive member, and a region where the drive electrode 4 is not provided, that is, a transmissive region is formed as shown in FIG. You may do it. Hereinafter, the shutter mechanism according to this configuration is referred to as an “electret shutter”.

  FIG. 2 is a diagram showing a basic configuration of the electret shutter.

  The right side of FIG. 2 schematically shows a cross section of the electret shutter. A voltage signal line from the drive circuit 10 is connected to each drive electrode 4 arranged on the stator 1. A four-phase voltage signal is applied to the voltage signal line. Therefore, the same voltage signal is applied to the drive electrodes 4 every four lines. In FIG. 2, the voltage signals are distinguished by attaching the symbols A, B, C, and D to the drive electrode 4.

  The mover 2 is provided with a plurality of permanent-polarized derivatives (electrets) 5 on the surface facing the stator 1. The mover 2 itself may be electrets that are permanently polarized at equal pitch intervals.

  The left side of FIG. 2 shows the configuration of the drive circuit 10 that generates a voltage signal to be applied to the electret shutter. The rectangular wave train (drive pulse signal) generated by the pulse generation circuit 12 is supplied to the booster circuit 14 and the phase shifter 15. The booster circuit 14 boosts the input rectangular wave train to about 100 V, branches it into voltage signals having two polarities, and supplies them to the drive electrodes A and C.

  On the other hand, the rectangular wave train input to the phase shifter 15 has a waveform delayed by 90 °, and is then input to the booster circuit 14 to form two rectangular wave trains similar to those described above, and supplied to the drive electrodes B and D. Is done.

The switch 13 switches the voltage applied to the electret shutter in accordance with a switching signal from the pulse generation circuit 12. The switch 13 includes a plurality of switches 13 a ₁ to 13 a ₄ and 13 b, and terminals c _{1 to} c ₄ of the switches 13 a _{1 to} 13 a ₄ supply power supply voltages to various circuits including the pulse generation circuit 13. The power supply Vc (for example, the voltage is 5V) is connected, the terminals a _{1 to} a ₄ are opened, and the terminals b _{1 to} b ₄ are connected to all the drive electrodes via the lines Lb _{1 to} Lb ₄ .

  The terminal c 'of the switch 13b is connected to the rectangular wave train output terminal Po of the pulse generating circuit 12, the terminal a' is connected to the booster circuit 14 and the phase shifter 15, and the terminal b 'is open.

When driving the mover 2 of the electret shutter, the pulse generation circuit 12 outputs a switching signal to the switch 13 to connect the terminals c of the switches 13a ₁ to 13a ₄ and the terminals a _{1 to} a _{4 and} to connect the terminals of the switch 13b. c ′ and terminal a ′ are connected. Thus, the rectangular wave signal output from the pulse generation circuit 12 can be supplied to the booster circuit 14 and the phase shifter 15.

On the other hand, when the electret shutter moving element is not driven (stopped on the spot), the pulse generation circuit 12 outputs a switching signal to the switch 13 and the terminals c _{1 to} c ₄ and the terminal b of the switches 13 a _{1 to} 13 a _4. to connect the ₁ ~b _4, to connect the 'terminal b and' terminal c of the switch 13b. As a result, all the drive electrodes are connected to the power supply voltage Vc.

  At this time, the electret site | part which has a polarity different from the voltage applied to the electrode will be in the state attracted | sucked by the electrode. That is, if a DC voltage is applied to the drive electrode when the mover 2 is not driven, the position of the mover 2 will not be shifted even if some external force is applied. Further, since the circuit power supply voltage is added to the drive electrode instead of the boosted voltage, the voltage may be a minimum voltage, and the power consumption can be reduced as compared with the case where the boosted voltage is added.

  FIG. 3 shows a voltage signal sequence created by the drive circuit 10 and applied to the drive electrode 4. As for the voltage state of the voltage electrode 4, the four states t1 to t4 change repeatedly corresponding to the passage of time.

  FIG. 4 is a diagram for explaining the operation of the electret shutter.

  (1) in FIG. 4 shows the voltage state of the electret and the drive electrode immediately after switching to t1. The electret 5 a receives a repulsive force from the drive electrode A and receives an attractive force from the drive electrode B. The electret 5 b receives a repulsive force from the drive electrode C and receives a suction force from the drive electrode D. For this reason, the movable element 2 receives a force in the right direction in the figure and moves by one drive electrode pitch d.

  (2) in FIG. 4 shows the voltage state of the electret and the drive electrode immediately after switching to t2. The electret 5 a receives a repulsive force from the drive electrode A and receives an attractive force from the drive electrode B. The electret 5 b receives a repulsive force from the drive electrode C and receives a suction force from the drive electrode D. For this reason, the movable element 2 receives a force in the right direction in the figure and moves by one drive electrode pitch d.

  (3) in FIG. 4 shows the state of the electret and drive electrode voltage immediately after switching to t3, and FIG. 4 (4) shows the state of the electret and drive electrode voltage immediately after switching to t4. Show. Similar to the above-described operation, the moving element 2 moves by one drive electrode pitch d. Then, by repeating this operation, the movable element 2 moves to the right in the figure. In order to move the movable element 2 in the left direction in the figure, the polarity of the voltage applied to the drive electrode 4 may be switched in reverse.

  FIG. 5 is a perspective view illustrating a configuration of an imaging module to which the electrostatic actuator according to the present invention is applied, and FIG. 6 is a cross-sectional view of the imaging module.

  The imaging module includes a shutter unit 21 and an imaging unit 22.

  The shutter unit 21 is a focal plane shutter having a light-shielding curtain (front curtain) 24a and a light-shielding curtain (rear curtain) 24b that run independently. The light shielding curtains 24a and 24b are provided with the above-described electret 5 (not shown). Further, stators 1a and 1b provided with a plurality of drive electrodes 4a and 4b and openings (or transmission parts) are arranged on the opposing surface side of each electret 5. Further, a protective member 25 having an opening (transmission portion) is fixed on the subject side of the shutter unit 21 so as to cover the front surface of the shutter unit 21 via spacers 31 to 34.

  Here, the stators 1a and 1b are formed by using a polyimide film as a substrate and printing the driving electrodes 4a and 4b on the surface thereof by an etching method, and further providing an insulating film on the driving electrodes 4a and 4b. On the other hand, the light-shielding curtains 24a and 24b use Teflon as a substrate, and form electrets on one surface thereof by the corona discharge method (electretize).

  The imaging unit 22 is configured by housing and fixing an imaging element 27 and a signal line 28 in a storage container 26, and covering the subject side of the storage container 26 with a cover glass 29 having an incident light transmission region (opening). Yes.

  Since the present imaging module uses the electret shutter to form the shutter unit 21, the thickness thereof can be greatly reduced as compared with the conventional shutter unit, and the thickness can be reduced.

  In addition, since the electret shutter does not use the charges induced in the light shielding curtains 24a and 24b but uses the charges that are permanently polarized in the electret, it is possible to shorten the rise time and speed up the shutter operation. it can.

  In addition, since the electret charge amount can be arbitrarily given, an optimum charge amount that maximizes the driving force can be given, and an extremely large driving force can be obtained. Accordingly, it is possible to configure an optimal shutter unit 21 corresponding to the size of the imaging module.

  Furthermore, the stators 1a and 1b and the light-shielding curtains 24a and 24b are lightweight because resin materials can be used as materials. For example, the light shielding curtains 24a and 24b can be formed of a thin film of 10 to 20 μm. Therefore, the amount of power required for the operation is small, and a quiet operation can be realized.

[First Embodiment]
The electrostatic actuator according to the first embodiment of the present invention positions the mover 2 at the initial position using a stopper.

  FIG. 7 is a diagram showing a configuration of an electrostatic actuator provided with a mechanical stopper. This electrostatic actuator is provided with a mechanical stopper 36 at a predetermined position of the stator 1, and the movable element 2 is positioned at the initial position by bringing the movable element 2 into contact with the stopper. The mechanical stopper 36 may also be used as, for example, a spacer (not shown) arranged in parallel with the drive electrode without being provided on the stator 1.

  FIG. 8 is a diagram illustrating a configuration of an electrostatic actuator provided with an electrical stopper. In this electrostatic actuator, an electret member 37 is fixed at a predetermined position of the stator 1, and the movable element 2 is positioned at the initial position by repelling the electretized part of the same polarity on the movable element 2. In addition, the polarity of the electret member 37 on the stator 1 can be configured to be different from the same polarity. In other words, the mover 2 may be positioned at the initial position by sucking the electretized portion having a different polarity on the mover 2.

  Next, the operation of the electrostatic actuator according to the present embodiment will be described. FIG. 9 is a schematic flowchart showing the initialization operation of the electrostatic actuator.

  After the power supply to the drive circuit 10 is turned on, the following initialization operation is executed before actual drive control is performed.

Changeover signal to the switch 13 at step S01, switches the switch _13a 1 _{~13a 4} and 13b, respectively _a 1 ~a ₄ and a 'side. As a result, the rectangular wave output terminal Po of the pulse generation circuit 12 is connected to the booster circuit 14 and the phase shifter 15.

In step S02, output of rectangular wave output is started. After waiting for a predetermined number of pulses to be output in step S03, the rectangular wave output is stopped in step S04. In step S05, a switching signal is output to the switch 13, and the switches 13a _{1 to} 13a ₄ and 13b are switched to the b _{1 to} b ₄ and b ′ sides, respectively. As a result, all the drive electrodes 4 and the power source Vc are connected, and the movable element 2 is held at the initial position, so that drive control can be performed thereafter.

  In this embodiment, a mechanical stopper or an electrical stopper is disposed at the initial position, and when the power is turned on, an initialization pulse signal is output. That is, a predetermined number of pulses corresponding to the maximum movement amount of the moving element 2 are output to move the moving element 2. As a result, the movable element 2 always reaches the stopper regardless of the position (even at the end farthest from the stopper), so that the initial positioning can be easily performed.

[Variation of the first embodiment]
Next, variations of the first embodiment will be described. In the first embodiment, a predetermined number of pulse signals are output. In this variation, as shown in FIG. 10, the initialization pulse signal is continuously output for a predetermined time required to output a predetermined number of pulses. This is different from the first embodiment.

  FIG. 11 is a schematic flowchart showing an initialization operation of the electrostatic actuator according to the variation of the first embodiment.

  After the power supply to the drive circuit 10 is turned on, the following initialization operation is executed before actual drive control is performed.

In step S11, a switching signal is output to the switch 13, and the switches 13a _{1 to} 13a ₄ and 13b are switched to the a _{1 to} a ₄ and a ′ sides, respectively. As a result, the rectangular wave output terminal Po of the pulse generation circuit 12 is connected to the booster circuit 14 and the phase shifter 15.

In step S12, output of rectangular wave output is started. After waiting for a predetermined time in step S13, the rectangular wave output is stopped in step S14. In step S15, a switching signal is output to the switch 13, and the switches 13a _{1 to} 13a ₄ and 13b are switched to the b _{1 to} b ₄ and b ′ sides, respectively. As a result, all the drive electrodes 4 and the power source Vc are connected, and the movable element 2 is held at the initial position, so that drive control can be performed thereafter.

  According to the present embodiment, the moving element 2 is moved by outputting a pulse in a time corresponding to the maximum movement amount of the moving element 2. As a result, as in the first embodiment, since the movable element 2 always reaches the stopper regardless of the position (even at the end farthest from the stopper), the initial positioning can be easily performed. it can.

[Second Embodiment]
The electrostatic actuator according to the second embodiment of the present invention positions the moving element 2 at the initial position by detecting that the moving element 2 has reached the initial position and stopping it.

  FIG. 12 is a diagram illustrating a configuration of an electrostatic actuator including a detection electrode. In this electrostatic actuator, the detection electrode 40 is arranged at a position on the stator 1 corresponding to the initial position. The output of the detection electrode 40 is input to the monitor circuit 41.

  The monitor circuit 41 includes a current-voltage conversion circuit 41a, an amplifier 41b, and a determination circuit 41c. The monitor circuit 41 detects that the movable element 2 has approached the detection electrode 40 and outputs a trigger signal.

  Next, the operation of the electrostatic actuator according to the present embodiment will be described.

  13 and 14 are diagrams for explaining the detection operation by the detection electrodes. As shown in FIG. 13 (a), when the moving element 2 and the detection electrode 40 are separated, the output voltage of the amplifier 41b is a determination criterion of the determination circuit 41c, as shown in FIG. 13 (b). It is below the threshold. Accordingly, the trigger signal is not output from the monitor circuit 41 at this time.

  As shown in FIG. 14A, when the movable element 2 comes close to the detection electrode 40, an induced charge is generated in the detection electrode 40 by the electret 5 of the movable element 2. This induced charge increases as the mover 2 approaches the detection electrode 40. Therefore, a current due to the change of the induced charge is generated, and the current increases as the movable element 2 approaches the detection electrode 40.

  The generated current is converted into a voltage signal by the current-voltage conversion circuit 41a and amplified by the amplifier 41b. As a result, as shown in FIG. 14B, the output voltage of the amplifier 41b becomes equal to or higher than a threshold value that is a determination criterion of the determination circuit 41c. Accordingly, at this time, a trigger signal is output from the monitor circuit 41.

  FIG. 15 is a schematic flowchart showing the initialization operation of the electrostatic actuator. After the power supply to the drive circuit 10 is turned on, the following initialization operation is executed before actual drive control is performed.

In step S21, a switching signal is output to the switch 13, and the switches 13a _{1 to} 13a ₄ and 13b are switched to the a _{1 to} a ₄ and a ′ sides, respectively. As a result, the rectangular wave output terminal Po of the pulse generation circuit 12 is connected to the booster circuit 14 and the phase shifter 15.

In step S22, output of rectangular wave output is started. After waiting for the trigger signal to be output from the monitor circuit 41 in step S23, the rectangular wave output is stopped in step S24. That is, the determination circuit 41c outputs a trigger signal to the pulse generation circuit 12 when the output signal of the amplifier 41b exceeds a set threshold value. When the trigger signal is input, the pulse generation circuit stops outputting the initialization pulse signal. In step S25, a switching signal is output to the switch 13 to switch the switches 13a _{1 to} 13a ₄ and 13b to the b _{1 to} b ₄ and b ′ sides, respectively. Thereby, all the drive electrodes 4 and the power supply Vc are connected, and drive control is attained after this.

  In addition, since it is possible to change the timing which outputs a trigger signal by changing a threshold value, the detection distance of the slider 2 and the detection electrode 40 can be adjusted.

  The monitor circuit 41 may be provided on the stator 1 or may be installed separately from the electrostatic actuator. Further, even when a magnetized magnetic body is mounted on the movable element 2 and a Hall element is used as a detection electrode, the proximity of the movable element can be detected in the same manner.

[Third Embodiment]
Next, a third embodiment will be described. In the second embodiment, a change in induced charge generated in the detection electrode due to the proximity of the moving element 2 is detected. In the third embodiment, a change in capacitance (capacitance) due to the proximity of the moving element 2 is detected. The point is different. Accordingly, parts having the same functions as those in the second embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 16 is a diagram illustrating a configuration of the electrostatic actuator according to the third embodiment. In this electrostatic actuator, the detection electrode 45a is disposed at a position on the stator 1 corresponding to the initial position, and the detection electrode 45b is disposed at a position on the protection member 43 corresponding to the initial position.

  The monitor circuit 46 monitors the change in capacitance when the moving element 2 moves between the detection electrodes 45a and 45b.

  The monitor circuit 46 is a diode bridge (capacitance bridge) circuit 46a to which an AC signal supplied from the power supply 47 is applied, an amplifier 46b that amplifies the output of the diode bridge circuit 46a, and a determination that compares the output of the amplifier 46b with a predetermined threshold value. When the movable element 2 is close to the detection electrodes 45a and 45b and the capacitance between the detection electrodes 45a and 45b changes to a predetermined value or more, a trigger signal is sent to the pulse generation circuit 12. Is output.

  Since the initialization operation of the electrostatic actuator according to the third embodiment is the same as the initialization operation of the second embodiment shown in FIG. 15, detailed description thereof is omitted.

  According to the third embodiment, the structure of the electrostatic actuator is complicated as compared with the second embodiment, but the proximity of the moving element 2 can be detected with high accuracy and a trigger signal can be output. .

[Fourth Embodiment]
Next, a fourth embodiment will be described. In the second embodiment, a change in the induced charge generated in the detection electrode due to the proximity of the mover 2 is detected. However, the fourth embodiment is different in that the contact between the mover 2 and the detection electrode is detected. ing. Accordingly, parts having the same functions as those in the second embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 17A is a cross-sectional view showing the configuration of the electrostatic actuator according to the fourth embodiment, and FIG. 17B is the configuration of the electrostatic actuator according to the fourth embodiment. FIG.

  In this electrostatic actuator, a detection electrode 50 that constitutes an electrical contact with two electrodes is disposed at a position on the stator 1 corresponding to the initial position, and further, an electrical contact is made at a position facing the detection electrode 50 on the mover 2. A conductive conductor 51 is provided. A voltage is always applied to the detection electrode 50 from the DC power supply 53, and the monitor circuit 52 detects that the conductor 51 of the moving element 2 is in contact with the two electrodes and the two electrodes are conducted.

  The monitor circuit 52 includes an amplifier 52b that amplifies the voltage supplied from the DC power source 53, and a determination circuit 52c that compares the output of the amplifier 52b with a predetermined threshold. The conductor 51 of the moving element 2 contacts the detection electrode 50. Then, the determination circuit 52c detects that a closed circuit is configured and a voltage is generated in the amplifier 52b, and outputs a trigger signal to the pulse generation circuit 12.

  Since the initialization operation of the electrostatic actuator according to the fourth embodiment is the same as the initialization operation of the second embodiment shown in FIG. 15, detailed description thereof is omitted.

  According to the fourth embodiment, since the contact of the moving element 2 is detected by the electrical contact, a direct and reliable detection output can be obtained.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

The figure which shows the shutter mechanism of the shutter apparatus to which the electrostatic actuator which concerns on this invention is applied. The figure which shows the basic composition of an electret shutter. The figure which shows the voltage signal sequence added to a drive electrode. The figure explaining operation | movement of an electret shutter. The perspective view which shows the structure of the imaging module to which the electrostatic actuator which concerns on this invention is applied. Sectional drawing which shows the structure of an imaging module. The figure which shows the structure of the electrostatic actuator provided with the mechanical stopper. The figure which shows the structure of the electrostatic actuator provided with the electrical stopper. 4 is a schematic flowchart showing an initialization operation of the electrostatic actuator. The figure which shows the state which outputs the initialization pulse signal continuously only for predetermined time. 4 is a schematic flowchart showing an initialization operation of the electrostatic actuator. The figure which shows the structure of the electrostatic actuator provided with the detection electrode. The figure explaining the detection operation by a detection electrode. The figure explaining the detection operation by a detection electrode. 4 is a schematic flowchart showing an initialization operation of the electrostatic actuator. The figure which shows the structure of an electrostatic actuator. The figure which shows the structure of an electrostatic actuator.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Stator, 2 ... Moving element, 3 ... Opening part (transmission part), 4 ... Drive electrode, 5 ... Electret, 10 ... Drive circuit, 21 ... Shutter unit, 24 ... Light-shielding curtain, 25 ... Protection member, 31 ... Spacer, 32 ... Spacer, 33 ... Spacer, 34 ... Spacer, 36 ... Mechanical stopper, 37 ... Electretized member, 40 ... Detection electrode, 41 ... Monitor circuit, 45 ... Detection electrode, 46 ... Monitor circuit, 50 ... Detection electrode , 51 ... conductor, 52 ... monitor circuit.

Claims (13)

A stator having a plurality of driving electrodes on the surface;
A mover that is movable relative to the stator and has a plurality of electretized parts;
A protective member arranged so as to sandwich the moving element with the stator;
A pulse generation circuit that outputs a drive pulse signal for driving the moving element;
A driving circuit for applying a multiphase AC voltage to the driving electrode based on a driving pulse signal from the pulse generating circuit;
A mechanical or electrical stopper disposed at a position on the stator corresponding to the initial position of the mover,
The electrostatic actuator characterized in that the pulse generation circuit outputs an initialization pulse signal for driving the moving element until it reaches the stopper after power is turned on.   The electrostatic actuator according to claim 1, wherein the mechanical stopper is a spacer fixed between the stator and the protective member.   The electrostatic actuator according to claim 1, wherein the electrical stopper is an electret member.   2. The electrostatic actuator according to claim 1, wherein the pulse generation circuit outputs a predetermined number of pulses corresponding to a maximum movement amount of the moving element as the initialization pulse signal.   2. The electrostatic actuator according to claim 1, wherein the pulse generation circuit outputs the initialization signal pulse for a predetermined time.   6. The drive circuit according to claim 1, wherein the drive circuit applies a constant voltage to the drive electrode after the drive of the movable element to the initial position is completed. Electrostatic actuator. A stator having a plurality of driving electrodes on the surface;
A mover that is movable relative to the stator and has a plurality of electretized parts;
A protective member arranged so as to sandwich the moving element with the stator;
A pulse generation circuit that outputs a drive pulse signal for driving the moving element;
A driving circuit for applying a multiphase AC voltage to the driving electrode based on a driving pulse signal from the pulse generating circuit;
Detecting means for detecting that the moving element has reached the initial position;
The electrostatic actuator characterized in that the pulse generating circuit outputs an initialization pulse signal after the power is turned on until the detecting means detects that the moving element has reached the initial position.   8. The electrostatic actuator according to claim 7, wherein the pulse generation circuit stops outputting the initialization pulse signal in accordance with a detection output of the detection means.   The detection means includes a detection electrode provided at a position on the stator corresponding to the initial position, and a capacitance change when the electretized portion of the movable element is connected to the detection electrode and close to the detection electrode. The electrostatic actuator according to claim 7, further comprising: a monitor circuit that detects a signal and supplies a trigger signal to the pulse generation circuit.   The detection means includes two detection electrodes arranged at positions corresponding to the initial position on the protection member and the stator, and when the electretized portion of the mover is in proximity between the two detection electrodes. The electrostatic actuator according to claim 7, further comprising: a monitor circuit that detects a capacitance change between the two detection electrodes and supplies a trigger signal to the pulse generation circuit.   The detection means includes a first conductive member provided at one end of the moving element, second and third conductive members provided at positions on the stator corresponding to the initial position, and a first The electrostatic actuator according to claim 7, further comprising a monitor circuit that supplies a trigger signal to the pulse generation circuit when the conductive member comes into contact with the second and third conductive members.   The detection means is connected to a detection element provided at a position on the stator corresponding to the initial position, and a magnetic body connected to the detection element and provided to the moving element in proximity to the detection element. The electrostatic actuator according to claim 7, further comprising a monitor circuit that detects a current change and supplies a trigger signal to the pulse generation circuit.   13. The drive circuit according to claim 7, wherein the drive circuit applies a constant voltage to the drive electrode after the drive of the movable element to the initial position is completed. Electrostatic actuator.

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