JPS6395864A - Electrostatic actuator - Google Patents

Abstract

PURPOSE:To exactly detect a position, by detecting the moving position of a rotor by the use of induced current due to the change of an electrostatic capacity due to similar detection electrodes to those of other positions. CONSTITUTION:An electrostatic actuator is composed by providing notched sections 1a at specified intervals radially from the axis of a rotation shaft 2 to the rotor 1 of a dielectric. The rotation shaft 2 is provided with upper and lower plates 5, 6, and is journaled rotatably by bearings 7, 8. Besides, on the lower surface of the upper plate 5 and the upper surface of the lower plate 6 which are confronted with the rotor, substrates 4 are laminated, and on the substrates, electrode pattern 3 are respectively arranged. In this case, a pair of detection electrodes 21-24 are arranged on both the surfaces of the substrates 4 confronted with each other. The other electrodes are used as drive electrodes, and four-phase voltage is applied to the electrodes in order from a drive circuit according to specified timing, and the rotor 1 is rotated. Then, induced current due to the change of an electrostatic capacity due to the detection electrodes 21-24 is detected, and the position of the rotor 1 can be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrostatic actuator that uses electrostatic force to move a mover eight times.

[Prior Art] Conventional actuators mainly utilize electromagnetic force, and due to their characteristics, they must be equipped with electromagnetic coils, permanent magnets, etc., and have a complicated structure. Furthermore, the power consumption was extremely high, and the amount of heat generated by the actuator was also large.

For this reason, electrostatic actuators are attracting attention because they have lower power consumption, higher efficiency, and can be made smaller than electromagnetic actuators.

[Problems to be solved by the invention] However, in general, electrostatic actuators have weaker driving force and torque than electromagnetic actuators, and when driven in pulses, they cannot be synchronized against load fluctuations or loads with large inertia. In extreme cases, the system could stop working.

Furthermore, for the same reason as mentioned above, when starting the actuator, it was necessary for a person to change and adjust the drive pulse frequency until it reaches a predetermined speed or rotational speed so as to be well synchronized.

In addition, for actuators that move in a straight line, it is more important to precisely control the stopping position than the speed, but conventional actuators suffer from positional deviation due to inertial loads, making it impossible to stop accurately. .

In order to solve the above-mentioned problems, attempts have been made to separately attach an optical encoder or the like to the actuator, but this has resulted in a larger mold and a more complicated configuration.

Means for Solving Problem C] The present invention has been made for the purpose of solving the problems of the above-mentioned conventional example, and as a means for achieving this purpose, the present embodiment has the following configuration.

That is, a stator in which a plurality of electrode patterns are arranged at predetermined intervals, a movable element that is movable relative to a surface of the stator on which the electrode patterns are arranged at a certain gap, and A moving means that sequentially applies a voltage to a part of the movable element and moves the movable element by electrostatic force generated between the applied electrode and the movable element, and an electrostatic charge between a specific electrode and the movable element that is generated when the movable element is moved by the moving means. and detection means for detecting the voltage or current induced in the specific electrode due to a change in capacitance.

[Operation] With the above configuration, there is no need for a special configuration to detect the moving position of the movable element, and it is possible to simply detect the galvanic current due to a change in capacitance from the same electrode, and to detect the current between the movable element and the electrode. The positional relationship between can be detected.

[Example] Hereinafter, an example according to the present invention will be described in detail with reference to the drawings.

[First Embodiment] FIG. 1 is an exploded perspective view of an embodiment according to the present invention, and FIG. 2 is a sectional view thereof.

In the figure, reference numeral 1 denotes a rotor made of a dielectric material, and the rotor 1 is provided with notches 1a radially extending from the axis of a rotating shaft 2 at predetermined intervals. In this embodiment, the rotor 1 is made of PZT (lead zirconate titanate). This rotor 1 is not limited to PZT, and for example, the specific electric current is ε
= 4 to 10,000, which is a high call rate material, and
Any dielectric material having weak conductivity of approximately x(+-12 to 1()-+3 Ωcm) may be used;
High dielectric constant ceramic materials such as lead titanate are suitable. Furthermore, it can also be formed from phenol resin, glass, or the like.

Reference numeral 2 denotes a rotating shaft to which the rotor 1 is attached, and is rotatably supported by a bearing 7 provided on the upper plate 5 and a bearing 8 provided on the lower plate 6. Note that the rotor 1 has a thickness of 0.4 m.
m and a diameter of 66 mm, and the rotating shaft 2 has a diameter of 1.5 mm.

A substrate 4 is provided on the lower surface of the upper plate 5 and the upper surface of the lower plate 6 facing the rotor 1.
are laminated, and electrode patterns 3 are arranged on the rotor-paired inner surface of the substrate 4, respectively. Although the electrode pattern disposed on the substrate 4 of the upper plate 5 is not shown in FIG. 1, it is similar to the electrode pattern on the substrate 4 of the lower plate 6. However, 21 to 24 are detection electrodes a to d, which are arranged as a pair on both opposing surfaces of the substrate 4. Electrodes other than these serve as drive electrodes, and each drive electrode disposed on the substrate 4 of the lower plate 6 has φA, φ
Four phase voltages of B, φC1φD are sequentially applied at predetermined timings to generate a rotating magnetic field on the substrate 4 and rotate the rotor 1. On the other hand, the electrodes disposed on the substrate 4 of the upper plate 5 are held at ground potential. However, if a voltage of opposite polarity to the voltage applied to the counter electrode disposed on the substrate 4 of the lower plate 5 is applied here, a larger driving force can be obtained. These electrodes 3 are formed by vapor deposition at predetermined intervals radially with respect to the axis of the rotating shaft 2 of the rotor 1.

Note that various methods such as etching can be used for patterning this electrode. In this example, the electrode 3
Although Cr is used as the electrode, buttering may be performed using various conductive metals such as Ag, Au, A-based metal, and Cu. Ti or Ta (tantalum) may be used to prevent the electrode from melting due to discharge.
You may use high melting point metals such as.

In this embodiment, the upper plate 5, lower plate 6, and substrate 4 are made of glass. However, these materials are not limited to glass, and may be made of plastics, ceramics, or the like as long as they have insulation properties.

A predetermined gap is maintained between the rotor 1 and the substrate 4 by spacers and screws (not shown), and the rotor 1 is configured to be rotatable in the direction of arrow A or arrow B in the figure.

In this example, the average pattern width of the electrode 3 is 1 mm,
The pattern pitch is 2 mm, and the distances between the electrodes 3 and the rotor 1, and between the rotor 1 and the upper plate 5 are both 0.25 mm.

By making the electrode pattern pitch and gap smaller, the torque generated on the rotor 1 becomes larger.

A schematic diagram of the principle configuration of this embodiment is shown in FIG.

In the figure, 21 to 24 are detection electrodes ayd, and between each electrode there is a resistance r a% r d and a detection power supply Qa to
Qd are connected in series, and the notch 1 of the rotor 1
It is possible to detect the change in capacitance caused by the movement of a and the other current visiting body group (rotor part) between the detection electrodes. 11 to 14 indicate drive pulse outputs of φA to φD, and 31 to 34 are drive switches 31 to 34 schematically shown in the drive circuit (40). As shown in the figure, in this embodiment, the 6 pitches of the notch portion 1a and the 5 pitches of the electrode pattern 3 are exactly equal, as shown in the figure.

FIG. 3 shows the configuration of the electrode control section of this example.

In FIG. 3, 40 is a drive circuit that controls the application of drive voltage to the drive electrodes A to D, and 41 is the detection electrode A to D (21 to 2
4) A control circuit that amplifies the detection signal from the detection electrodes A to D, and generates drive timing for the drive electrodes A to D from the detection signal, and outputs it to the drive circuit 40;
This is a power supply circuit that supplies a detection DC voltage to 1 to 24).

The control of this embodiment having the above configuration will be explained below with reference to the timing chart of FIG.

Now, consider the case where mover 1 is moving in the direction of arrow A.
If the state shown in FIG. 2 is defined as time "O", the detection electrode 21
Since the dielectric portion 35 slides in, the capacitance between the electrodes increases, and current flows in the positive direction toward the upper electrode 21a. On the other hand, the capacitance is maximum in this instantaneous detection voltage g c 23 and the driving electrode C, and in order to maintain the driving torque in the six directions of the arrow, it is not preferable to output φC, and here φC13 It is desirable to turn it off. Therefore, the rise of the detection current Ia from the detection electrode a21 is used as the trigger signal.

In this way, the capacitance between the detection electrodes a21 continues to increase, and at the next time Tc, the dielectric portion 1 completely enters between the detection electrodes a21.

At this time, the capacitance is at its maximum, and since the capacitance decreases thereafter, a current flows in the opposite direction (power supply charging direction) from the electrode 21a toward the power supply Qa. At this time φC13
The relationship between the drive electrode and the dielectric portion is the same as the relationship between the detection electrode a21 and the dielectric portion 1 at time “0”. That is,
The dielectric portion is now in a state of being drawn in, and if a voltage is applied to the drive electrode of φC13, a drive torque in the direction of arrow A is generated. Therefore, due to this current change (at Tc), φ
It is sufficient to output C13. In this way, the detection electrode a2
φC13 is generated by the change detection signal of Ia of 1, and φC
Controls voltage application to the drive electrode group.

Similarly, φ014 is generated by the Ib change detection signal of the detection electrode b22, voltage application to the φD drive electrode group is controlled, and φAi is generated by the Ic change detection signal of the detection electrode c23.
It is sufficient to generate l, control the voltage application to the φA drive electrode group, generate φB12 based on the Id change detection signal of the detection electrode d24, and control the voltage application to the φBIIK electrode group. In the configuration shown in FIG. 2, the control timing is shifted by 1/4 period of the period of the change detection signal of Ia of the detection electrode a21.

A change in current Ix can be easily detected by detecting a change in potential on the electrode side of resistor rx, and the control circuit 41 amplifies the signal from this electrode side with an amplifier (not shown) and inverts it. Each corresponding drive circuit has obtained a drive signal. The drive circuit 40 applies voltage to the electrodes 3 by applying a pulsed voltage of (OV/+V)V to each phase (each electrode).

φA11. φB12. When a pulsed voltage as shown in FIG. 4 is applied to each phase of φC13 and φD14, a moving electric field is generated in the direction of arrow A in FIG. 2. Then, rotor 1
This moving electric field induces charges in the dielectric part of the moving electric field, and a driving force that follows the moving electric field in the same direction of arrow A with a certain slip is applied.For example, when a "+" potential is applied to a certain electrode, the Near the surface of the dielectric part of the rotor 1 between the electrodes, a charge with a polarity opposite to the voltage applied to the electrode (in this case, a "-" charge) is locally generated due to the dielectric polarization or weak conductivity of the dielectric part. is charged. In this state, when the potential applied to the electrode changes (the phase changes) and a voltage is applied to the adjacent electrode part, the electric force lines from the applied electrode cause a force F = qE (q; dielectric part The surface charge accumulated on the surface (E: electric field strength in the direction of rotation of electric lines of force) acts to generate a moving torque.

Note that in order to move the rotor 1 in the opposite direction, the phase order of the applied voltages may be reversed.

[Second Embodiment] Also, the above explanation describes the case where the number of drive electrode phases is 4, but
The number of drive phases of the drive electrodes is not limited to this, and any number of phases may be used as long as a moving electric field can be generated.

FIG. 5 shows an example in which the total number of drive electrodes is six phases. As shown in the figure, the detection electrodes are axes (21 to 25), and the seven pitches of the cutout portion 1a and the six pitches of the electrode pattern 3 are exactly equal.

FIG. 7 shows the detection signal and drive timing of the drive electrode in the case of the above configuration. As shown in the figure, the difference from the four-phase drive case of the first embodiment is that the timing of change in the detection signal from the detection electrode and the output timing of the drive signal are not the same as in the above-mentioned four-phase case. , predetermined delay time Td
It is to have. This is because a drive potential is applied between the drive electrodes at the moment the dielectric material enters between the drive electrodes.

[Third Embodiment] In the above two embodiments, the type in which the dielectric portion is drawn between the drive electrodes has been described, but the present invention is not limited to this.
), the movable element is made of an insulative member (glass, insulating plastics, ceramics, etc.), and electrode patterns are formed at a predetermined pitch on the surface of the substrate 4 of the movable element facing the electrode pattern. The movable element driving force may be obtained using an inter-electrode attractive force generated by a potential difference of opposite polarity between the child-side electrode and the substrate-side electrode.

The configuration in this case is shown in FIG.

Here, an example is shown in which the substrate 4 is disposed only on one side (for example, the lower plate 6 side) and the substrate side electrodes are disposed only on one side.

All the electrodes on the movable element side are set at ground potential, and each drive signal shown in FIG. 4 may be applied to the electrodes on the substrate 4 side.

[Fourth Embodiment] Although the above description has been made regarding an electrostatic actuator having a motor structure that performs circular motion around the drive shaft 2, the present invention is not limited to this. It can also be used for moving type electrostatic actuators. FIG. 8 shows a type of electrostatic actuator in which the movable element moves in parallel.

In the figure, 80 is a base made of a conductive material such as An,
81 is a stator disposed on the base 80 with φ
Each electrode of A to φD is formed. In this embodiment, the stator 81 is made of glass, and an electrode pattern is formed on its surface by vapor deposition. Various methods such as etching can be used for patterning the electrode. The stator 81 may be made of the same material as the substrate 4 of FIG.

Further, 83 is a movable element having an electrode 83a disposed on a surface facing the stator, and in this embodiment, glass is used as the movable element 83. The electrodes of the stator 81 and the movable element 85 may be made of the same material as the electrode 3 of FIG. 1.

The phases φA, φB, φC9φD are sequentially driven as shown in the timing chart of FIG.

Further, 82a and 82b are retainers disposed outside the stator 81, and hold non-conductive balls 85 at a constant gap within the retainers 82a and 82b. With the above configuration, the gap between the stator 1 and the movable element 3 can be narrowed while maintaining a good transfer state of the balls 85. In this example, the outer diameter of the ball 85 is 800 μm, and the thickness of the stator 1 is 790 μm.
A gap of 10 μm was achieved.

In this example, it is also possible to use the drive electrode as the detection electrode, but in order to avoid the influence of noise etc.
A detection mold F7186 is provided separately from the drive electrode.

[Other Embodiments] Although the above description has been made regarding an example in which all the detection signals from the detection electrodes are applied to drive timing control of the drive electrodes, the present invention is not limited to this, and the present invention is not limited to this. By measuring the period of the detection signal of rotor 1
It is also possible to detect the rotational speed of the movable element 83 or the moving speed of the movable element 83. An example of this case is shown in FIG.

In FIG. 9, the same components as in FIG. 3 are given the same numbers. As shown in the figure, a rotation speed detection circuit 4 is provided separately from the control circuit 41.
3. By providing the clock circuit 44, the rotation speed detection circuit 43 can easily detect the rotation speed by counting the detection signals from the detection electrodes per predetermined time specified by the clock circuit 44. By using this, φ to the drive electrode can be
The drive timing control for A to φD is performed up to the specific rotation speed detected by the above method, and thereafter the drive is controlled according to the drive signal from the drive signal generation circuit 45 that outputs a drive signal of a predetermined period, and the drive rotation speed etc. are controlled again. If the value deviates from a predetermined value, control may be performed as shown in FIG. 4, for example, according to the detection signal from the detection electrode.

In addition, in the case of FIG. 8, the moving position of the movable element 83 can be detected by checking the detection signal from the detection electrode, and the moving speed of the movable element 83 can be controlled by this detection signal even if the inertial load is large. , the vehicle can be reliably stopped at a desired stopping position.

As explained above, according to each of the embodiments, it is possible to prevent pulse drive asynchronousness due to load fluctuations or inertial loads, stopping at an incorrect position, etc. with an extremely simple configuration.

Further, there is no need for a person to change the drive frequency in synchronization with the rotation of the movable element etc. to reach the desired frequency at the time of startup, and the startup can be performed automatically and reliably.

Furthermore, even in the case of a straight-line type actuator that requires stop position control, it is possible to provide an actuator in which the stop position does not shift due to inertial load.

Moreover, it is not necessary to provide a special encoder mechanism, and a low-cost actuator with a simple configuration can be provided.

A special material such as electret is not required for the mover, and an inexpensive current reading material such as glass or phenol resin may be used.

Since it is driven by electrostatic force, power consumption is extremely low and there is no risk of generating heat due to Joule heat.

[Effects of the Invention] As described above, according to the present invention, an electrostatic actuator with high configuration and low power consumption can be provided using inexpensive materials instead of special materials.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of an embodiment according to the present invention, Fig. 2 is a diagram explaining the operation of the embodiment, Fig. 3 is a block diagram of the control section of the embodiment, and Fig. 4 is a diagram of the embodiment. 5 is a diagram explaining the operation of another embodiment according to the present invention. FIG. 6 is a control timing chart of the embodiment shown in FIG. 5. FIG. 7 is a control timing chart of another embodiment according to the present invention. FIG. 8 is a perspective view of another embodiment according to the present invention, and FIG. 9 is a block diagram of a control section of another embodiment. In the figure, 1...rotor, 2...rotating shaft, 3...electrode, 4...substrate, 5...upper plate, 6...lower plate, 7.8
...Bearing, 21-25.86...Detection electrode, 40
... Drive circuit, 41 ... Control circuit, 42 ... Power supply circuit, 43 Rotation speed detection circuit, 44 ... Timing circuit, 45
... Drive signal generation circuit, 80... Base, 81...
- Stator, 82a. 82b...retainer, 85...ball, 86. Patent Applicant: Canon Co., Ltd. No. 1, Figure 3, Figure 4, Figure 5, Figure 6, Procedure Nei City Official Letter (Spontaneous), December 1, 1986, Patent Office Director General, 1, Patent application for indication of the incident. No. 61-241247 No. 2, Name of the invention Electrostatic actuator 3, Relationship to the amended person case Patent applicant 3-30-2 Shimomaruko, Ota-ku, Tokyo (Zoo) Canon Co., Ltd. Representative Ryu Kaku Sanbe 4; Agent 1-2-12 Toranomon, Minato-ku, Tokyo 105 5. Column for detailed explanation of the invention and drawing 6 in the specification subject to amendment, Contents of amendment (1) From line 14 on page 6 of the specification Correct the 17th line as follows. Any material with a high dielectric constant of about r may be used, and high dielectric constant ceramic materials such as barium titanate and lead titanate are suitable. Furthermore, dielectric materials having weak conductivity with a surface resistivity of about 1011 to 10130 can also be used, ”
and correct it. (3) "Drive electrode" on page 10, line 14 of the specification is corrected to "drive electrode." (4) "Figure 7" in the second line of page 16 of the specification is corrected to "Figure 6." (5) "85" on the bottom line of page 18 of the specification is corrected to "83". (6) "Encoder" on page 22, line 5 of the specification is corrected to "encoder." (7) Correct Figure 9 as shown in the attached sheet.

Claims (4)

[Claims] (1) A stator in which a plurality of electrode patterns are arranged at predetermined intervals, a movable element that is movable relative to the electrode pattern arrangement surface of the stator at a constant gap, and electrodes of the stator. A moving means that sequentially applies a voltage to a part of the pattern and moves the movable element by electrostatic force generated between the applied electrode and the movable element, and a specific electrode and the movable element generated by the movement of the movable element by the moving means. An electrostatic actuator comprising: a detection means for detecting a voltage or current induced in the specific electrode due to a change in capacitance between the electrodes. (2) The movable element is formed by alternately arranging high-permittivity parts and low-permittivity parts at predetermined intervals, and the detection means is induced by the sliding of the low or high permittivity part into and out of the connecting electrode. 2. The electrostatic actuator according to claim 1, wherein the electrostatic actuator detects a voltage or current. (3) Electrode patterns are arranged at predetermined intervals on the surface of the mover facing the stator electrode, and the detection means detects the voltage or current induced in the electrode when the mover electrode slides into and out of a specific electrode. An electrostatic actuator according to claim 1, characterized in that: (4) The electrostatic actuator according to any one of claims 1 to 3, wherein the moving means controls the timing of voltage application to the electrodes according to the detection result of the detection means.