JP2011095021A - Electrostatic encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make constant the level of a signal subjected to electrostatic induction from a moving body electrode to a stator electrode even if a moving body is subjected to surface wobbling. <P>SOLUTION: An electrostatic encoder induces an electric signal indicating an amount of mechanical relative position displacement from a plurality of electrodes (moving electrodes) provided on a moving substrate 2 to an electrode (fixed electrode) provided on a fixed substrate 1 by static electricity following a change in the relative positions of the fixed substrate 1 and the moving substrate 1 both having electrodes on the mutually opposing surfaces. At least one fixed electrode is disposed at a position opposite to the moving electrode on the moving substrate 2 and at mutually symmetrical positions relative to a prescribed center of the moving substrate in the fixed substrate 1. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention includes an electrostatic encoder that includes a fixed substrate having electrodes on opposite surfaces and a moving substrate, and detects a moving amount, a moving speed, and the like by an electrostatic induction effect between the counter electrodes accompanying the relative movement. It is about.

  Among electrostatic encoders, for example, an electrostatic rotary encoder is an electrical encoder that exhibits a mechanical displacement of rotation due to a change in electrostatic induction between the electrodes on the opposing surfaces of the fixed substrate and the rotating substrate. In addition to obtaining a signal, the electrical signal can be processed to detect the amount of rotation and the rotation speed of the rotating shaft.

  A conventional example of this electrostatic rotary encoder will be described with reference to FIGS. FIG. 14A shows an arrangement configuration of the fixed substrate and the rotating substrate, and FIG. 14B shows a configuration of the fixed substrate and the rotating substrate viewed from the side. FIG. 15A shows the planar configuration of the rotating substrate, and FIG. 15B shows the planar configuration of the fixed substrate. FIG. 16 shows a state in which the rotating substrate is deviated from the fixed substrate, and FIG. 17 shows a state in which the rotating substrate is deviated in the opposite direction to the fixed substrate.

  First, referring to FIGS. 14 (a) and 14 (b) and FIGS. 15 (a) and 15 (b), 1 is a fixed substrate having a circular shape in plan view, and 2 is a rotating substrate having a circular shape in plan view. These two substrates 1 and 2 are opposed to each other with a certain distance therebetween. The fixed substrate 1 has a fixed electrode 4 on a part of a circumference with a constant radius around the rotation axis 3. Similarly, the rotating substrate 2 has a plurality of rotating electrodes 5 arranged at equal intervals over the entire circumference of the same radius centered on the rotating shaft 3. The fixed electrode 4 is capacitively coupled to the rotating electrode 5. As a result, when the rotating substrate 2 rotates around the rotation axis 3 with respect to the fixed substrate 1, the static electrode 4 of the fixed substrate 1 causes electrostatic capacitance caused by the capacitive coupling with the rotating electrode 5 of the rotating substrate 2. In accordance with the inductive action, an electric signal applied to the rotating electrode 5, for example, a carrier signal can be modulated and received. The modulation signal is input to a circuit (not shown) from the fixed electrode 4 and demodulated by the circuit so that it can be used for detecting the rotation of the rotating substrate 2.

JP 2005-221472 A

  In the electrostatic rotary encoder, as shown in FIG. 16, when the rotating substrate 2 is displaced relative to the rotating shaft 3 with respect to the fixed substrate 1, the rotating electrode 5 of the rotating substrate 2 fixes the fixed substrate 1. As a result of approaching the electrode 4, the electrostatic induction action between the fixed electrode 4 of the fixed substrate 1 and the rotating electrode 5 of the rotating substrate 2 is increased, thereby increasing the level of the electric signal received by the fixed electrode 4. . On the other hand, in FIG. 17, as a result of the rotating electrode 5 of the rotating substrate 2 being separated from the fixed electrode 4 of the fixed substrate 1, the static electricity between the fixed electrode 4 of the fixed substrate 1 and the rotating electrode 5 of the rotating substrate 2. As the inductive action is reduced, the level of the electric signal applied to the fixed electrode 4 is reduced.

  As described above, in the conventional electrostatic rotary encoder, when the rotating substrate 2 is displaced from the rotating shaft 3, the electric signal on the fixed electrode 4 side changes in level, so that the detection accuracy is greatly reduced. There is a problem. However, while it is difficult to easily prevent the surface of the rotating substrate 2 from being shaken, there is a problem that it is costly to adopt the surface shake preventing structure.

  The above problem is derived not only in the electrostatic rotary encoder but also in the electrostatic linear encoder in which the substrate facing the fixed substrate is a moving substrate that moves linearly.

  Therefore, the problem to be solved by the present invention is that, in an electrostatic encoder, even when a moving substrate such as a rotating substrate moves relative to the fixed substrate, it is generated by electrostatic induction at the fixed electrode of the fixed substrate. It is possible to make the level of the electric signal to be constant, thereby enabling a highly accurate detection operation without employing a costly anti-shake structure.

  The electrostatic encoder according to the first aspect of the present invention is configured to fix the fixed encoder from a plurality of electrodes (moving electrodes) provided on the moving substrate in accordance with a relative position change between the fixed substrate and the moving substrate both having electrodes on opposite surfaces. In an electrostatic encoder that electrostatically induces an electrical signal indicating a mechanical relative positional displacement amount to an electrode (fixed electrode) provided on a substrate, the fixed substrate has a position facing the moving electrode on the moving substrate. And at least 1 fixed electrode is arrange | positioned in the position symmetrical with respect to each other with respect to the predetermined center of the said moving substrate, It is characterized by the above-mentioned.

  According to the first aspect of the present invention, the average level of the signals that are electrostatically induced by the two fixed electrodes on the fixed substrate can be made constant even if the moving substrate is deviated from the predetermined center. It is possible to detect a movement amount, a movement speed, and the like from the signal. As a result, in the first aspect of the present invention, it is not necessary to adopt a costly surface blur prevention structure, and the cost can be reduced.

  In the first aspect of the present invention, a preferred embodiment is a rotary encoder configuration in which a moving substrate is rotatable about an axis with respect to a fixed substrate, and the moving electrodes on the rotating substrate are arranged at equal intervals in the circumferential direction with a predetermined radius. A plurality of them are arranged, and the at least both fixed electrodes on the fixed substrate are respectively arranged at rotationally symmetric positions on the circumference of a predetermined radius from the rotation center of the rotating substrate.

  In the first aspect of the present invention, a preferred aspect is a linear encoder configuration in which the moving substrate is linearly movable with respect to the fixed substrate, and the moving electrode on the moving substrate is linearly positioned in a line-symmetric position with respect to a predetermined center line. A plurality of them are arranged, and at least both of the fixed electrodes on the fixed substrate are arranged at positions symmetrical with respect to a predetermined center line of the movable substrate.

  The encoder according to the second aspect of the present invention is provided on the fixed substrate from a plurality of electrodes (moving electrodes) provided on the moving substrate in accordance with a change in relative position between the fixed substrate and the moving substrate both having electrodes on opposite surfaces. In the electrostatic encoder that electrostatically induces an electrical signal indicating a mechanical relative positional displacement amount to a fixed electrode (fixed electrode), a fixed substrate is arranged on both sides of the moving substrate, and both the fixed substrates are At least one fixed electrode is disposed at each position of the moving substrate facing the moving electrode.

  The moving electrodes on the moving substrate are not limited to the moving electrodes provided on both the front and back surfaces of the moving substrate, but also include at least one moving electrode disposed only on the front surface, only the back surface, or the inner layer of the moving substrate. be able to.

  The moving electrode is preferably provided at each symmetrical position that is equidistant from a predetermined center in a side view with respect to the moving substrate.

  According to the second aspect of the present invention, even if the moving substrate is deviated at the predetermined center, it is possible to equalize the addition level of the electrostatic induction signal to the fixed electrode on the fixed substrate that sandwiches the moving substrate from both sides thereof. Therefore, it is possible to detect a movement amount, a movement speed, and the like from this addition level signal. As a result, in the second aspect of the present invention, it is not necessary to adopt a costly surface blur prevention structure, and the cost can be reduced.

  According to the present invention, even if the moving substrate is faced, it is not necessary to employ a costly structure for preventing face shaking, so that the cost can be reduced.

FIG. 1 is a diagram showing a conceptual configuration of an electrostatic rotary encoder according to an embodiment of the present invention. FIG. 2A is a diagram illustrating a planar configuration of the rotating substrate, and FIG. 2B is a diagram illustrating a planar configuration of the fixed substrate. FIG. 3 is a diagram illustrating a state where the rotating substrate is out of plane. FIG. 4 is a diagram showing a state in which the rotating substrate is deviated in a direction opposite to the direction of deviating in FIG. FIG. 5 is a diagram showing a planar configuration of the electrostatic linear encoder according to the second embodiment of the present invention. FIG. 6 is a diagram showing a side configuration of the electrostatic linear encoder shown in FIG. FIG. 7 is a diagram showing a state in which the linear moving body is moving in the electrostatic linear encoder shown in FIG. FIG. 8 is a diagram showing a conceptual configuration of the electrostatic rotary encoder according to the third embodiment of the present invention. 9A is a diagram showing a planar configuration of an upper fixed substrate provided in the electrostatic rotary encoder of FIG. 8, and FIG. 9B is a diagram showing a planar configuration of a rotating substrate provided in the electrostatic rotary encoder of FIG. FIG. 9C is a diagram showing a planar configuration of the lower fixed substrate provided in the electrostatic rotary encoder of FIG. FIG. 10 is a diagram illustrating a state where the rotating substrate of the third embodiment is out of plane. FIG. 11 is a diagram showing a modification of the third embodiment. FIG. 12 is a diagram showing a planar configuration of the electrostatic linear encoder according to the fourth embodiment of the present invention. FIG. 13 is a diagram showing a side configuration of the electrostatic linear encoder shown in FIG. FIG. 14A is a diagram showing an external configuration of a fixed substrate and a rotating substrate in a conventional electrostatic rotary encoder, and FIG. 14B is a diagram showing a configuration of the fixed substrate and the rotating substrate viewed from the side. It is. FIG. 15A is a diagram illustrating a planar configuration of the rotating substrate, and FIG. 15B is a diagram illustrating a planar configuration of the fixed substrate. FIG. 16 is a diagram illustrating a state in which the rotating substrate is displaced from the fixed substrate. FIG. 17 is a view showing a state in which the rotating substrate is displaced in the direction opposite to the above with respect to the fixed substrate.

  Hereinafter, an electrostatic encoder according to an embodiment of the present invention will be described with reference to the accompanying drawings.

(Embodiment 1)
The first embodiment will be described with reference to FIGS. The electrostatic encoder according to the first embodiment is a rotary encoder, and includes a fixed substrate 1 that is circular and is non-rotatably fixed in a plan view, and a rotatable substrate 2 that is rotatable in a circular shape in plan view. The fixed substrate 1 is an electrode (fixed electrode) at a position where the substrate center O1 coincides with the rotation axis 3 and is opposed to the rotation center O1 at a position of 180 degrees on the circumference having a fixed radius, that is, a rotationally symmetric position with respect to the rotation center O1 4a and 4b are arranged at least one by one. Similarly, the rotation substrate 2 has a rotation center O2 coincident with the rotation axis 3, and a plurality of electrodes (rotation electrodes) 5 are arranged at equal intervals from the rotation center O2 to the entire circumference on the circumference having the same radius as the radius. The rotating substrate 2 rotates around the rotation center O2 together with the rotating shaft 3. The electrostatic rotary encoder further includes an averaging circuit that averages the output signals of both the fixed electrodes 4a and 4b.

  3 and 4, when the rotating substrate 2 is displaced relative to the rotating shaft 3 with respect to the fixed substrate 1, the rotating electrode 5 of the rotating substrate 2 is fixed to the fixed substrate in FIG. 3. 4, the rotating electrode 5 of the rotating substrate 2 moves away from the fixed electrode 4 b of the fixed substrate 1 and approaches the fixed electrode 4 a.

  As a result, in FIG. 3, the electrostatic capacity between the rotating electrode 5 and the fixed electrode 4b is C1, the electrostatic capacity between the rotating electrode 5 and the fixed electrode 4a is C2 (<C1), and in FIG. Between the rotating electrode 5 and the fixed electrode 4a is C3 (> C3). With respect to these capacitance changes, the opposing capacitances of the fixed electrodes 4a and 4b of the fixed substrate 1 and the rotating electrode 5 of the rotating substrate 2 when the rotating substrate 2 is not shaken as shown in FIG. It is.

  In FIG. 1, the distance between the rotating electrode 5 and the fixed electrode 4a is d0, the distance between the rotating electrode 5 and the fixed electrode 4b is d0, and the total distance is 2d0. In addition, the distance between the rotating electrode 5 and the fixed electrode 4a in FIG. 3 is d2, and the distance between the rotating electrode 5 and the fixed electrode 4b is d1, and the distance between approach and separation is offset, so that the total distance is uneven. (D1 + d2) = 2d0, which is the same as the distance that is not. In FIG. 4, the distance between the rotating electrode 5 and the fixed electrode 4a is d4, and the distance between the rotating electrode 5 and the fixed electrode 4b is d3. As with no distance, (d3 + d4) = 2d0.

  Therefore, the total distance is the same even when the surface is not shaken as shown in FIG. 1 or when the surface is shaken as shown in FIGS. 3 and 4. Therefore, the average capacitance in FIG. (C1 + C2) / 2 = C0, and the average capacitance in FIG. 4 is (C3 + C4) / 2 = C0. In other words, in the embodiment, even if the rotating substrate 2 is fluctuated, the capacitances of the two fixed electrodes 4a and 4b and the two rotating electrodes 5 facing the fixed electrodes 4a and 4b are the same on average.

  Thereby, the level of the electric signal received by both the fixed electrodes 4a and 4b by the electrostatic induction action between the fixed electrodes 4a and 4b of the fixed substrate 1 and the rotating electrode 5 of the rotating substrate 2 is determined by the averaging circuit. When averaged, in the case of FIG. 1, the case of FIG. 3 and the case of FIG. 4 all become the same level. Therefore, in this embodiment, even if the rotating substrate 2 is shaken, the level of the electric signal received by the fixed electrodes 4a and 4b of the fixed substrate 1 can be averaged to be constant.

(Embodiment 2)
An electrostatic encoder according to a second embodiment of the present invention will be described with reference to FIGS. Parts corresponding or similar to those in FIGS. 1 to 4 are denoted by the same reference numerals. The encoder according to the second embodiment is an electrostatic linear encoder. This electrostatic linear encoder includes a fixed substrate 1 and a moving substrate 2 that linearly moves in the directions of arrows P and Q in the drawing. The fixed substrate 1 is provided with fixed electrodes 4 a and 4 b at symmetrical positions with respect to the horizontal center line 3 of the moving substrate 2. The movable substrate 2 is a substrate having a belt-like configuration in the directions of arrows P and Q, and is a position symmetrical with respect to the center line 3, that is, a position symmetrical with respect to the center line 3 and facing the fixed electrodes 4a and 4b, respectively. In addition, the movable electrodes 5a and 5b are provided.

  In the above configuration, when the moving substrate 2 is not shaken, the capacitance between the fixed electrode 4a and the linear moving electrode 5a and the capacitance between the fixed electrode 4b and the moving electrode 5b are both C0. It is. The average of the total capacity is C0.

  When the moving substrate 2 is displaced as shown in FIG. 7, the capacitance between the fixed electrode 4a and the moving electrode 5a is C2, and the capacitance between the fixed electrode 4b and the moving electrode 5b is both C1. In this case, the sum of the first distance between the fixed electrode 4a and the movable electrode 5a and the second distance between the fixed electrode 4b and the movable electrode 5b is the first and second distances when the surface is not shaken. Therefore, the average (C1 + C2) / 2 of the total capacity is C0, which is the same as the average of the total capacity when the moving substrate 2 is not shaken.

  Therefore, also in the second embodiment, even if the moving substrate 2 fluctuates, the level of the electrical signal electrostatically induced in the fixed electrodes 4a and 4b of the fixed substrate 1 can be made constant by averaging.

(Embodiment 3)
An electrostatic encoder according to a third embodiment of the present invention will be described with reference to FIGS. The encoder of the third embodiment is a rotary encoder. As shown in FIG. 8, fixed substrates 1 a and 1 b are arranged on both sides of the rotating substrate 2. The fixed substrates 1a and 1b are fixed in a non-rotating state, with their substrate surfaces perpendicular to the rotation axis 3 and parallel to each other. The rotation centers O 1 and O 2 of the fixed substrates 1 a and 1 b and the rotation center O 3 of the rotation substrate 2 coincide on the rotation axis 3. The rotary substrate 2 is attached so as to be rotatable around the rotation center O3.

  As shown in FIG. 8 and FIG. 9A, the fixed substrate 1a has fixed electrodes 4a and 4b opposed to the center of the rotation center O1 at a predetermined radius of 180 degrees in the circumferential direction, as shown in FIG. ), Fixed electrodes 4c and 4d are arranged on the fixed substrate 1b so as to face the center of rotation O2 at 180 degrees in the circumferential direction at the same radius as the above radius. Further, as shown in FIGS. 8 and 9B, a plurality of rotating electrodes 5a are fixed to the rotating substrate 2 on the surface facing the fixed substrate 1a from the rotation center O3 in the circumferential direction at the same radius as the radius. A plurality of rotating electrodes 5b are arranged on the surface facing the substrate 1b in the circumferential direction at the same radius as the radius from the rotation center O3.

  First, as shown in FIG. 8, when the rotating substrate 2 is not shaken, the facing distance between the fixed electrode 4b of the fixed substrate 1a and the rotating electrode 5a of the rotating substrate 2 is d0, and the corresponding capacitance is C0. The facing distance between the fixed electrode 4d of the fixed substrate 1b and the rotating electrode 5b of the rotating substrate 2 is d0, and the corresponding capacitance is C0. The total capacitance of these capacitances is 2C0. Further, the opposing distance between the fixed electrode 4a of the fixed substrate 1a and the rotating electrode 5a of the rotating substrate 2 is d0 and the corresponding capacitance C0. The fixed electrode 4c of the fixed substrate 1b and the rotating electrode 5b of the rotating substrate 2 are The opposing distance is d0, the corresponding capacitance is C0, and the total capacitance of these capacitances is 2C0.

  In the above description, the opposing distance between the fixed electrode 4d of the fixed substrate 1b and the rotating electrode 5b of the rotating substrate 2 and the opposing distance between the fixed electrode 4a of the fixed substrate 1a and the rotating electrode 5a of the rotating substrate 2 are both d0. As described above, although both the capacitances are set to C0, the present invention is not limited to this, and the two opposing distances may be different, and thus the capacitances may be different.

  Then, as shown in FIG. 10, when the rotating substrate 2 is shaken, the opposing distance between the fixed electrode 4b of the fixed substrate 1a and the rotating electrode 5a of the rotating substrate 2 approaches, and the electrostatic capacitance between the electrodes 4b and 5a approaches. The capacitance is C4 (> C0), the facing distance between the fixed electrode 4d of the fixed substrate 1b and the rotating electrode 5b of the rotating substrate 2 is separated, and the capacitance between the electrodes 4d and 5b is C2 (<C0). Yes, the total capacity of these capacitances is 2C0 as a result of each opposing distance being totally offset by approach and separation. The total capacitance of the counter capacitance C3 between the fixed electrode 4a of the fixed substrate 1a and the rotary electrode 5a of the rotary substrate 2, and the counter capacitance C1 of the fixed electrode 4c of the fixed substrate 1b and the rotary electrode 5b of the rotary substrate 2 Is 2C0 as well.

  As described above, if the projected area of the counter electrode is the same, the capacitance changes in inverse proportion to the distance between the counter electrodes, but the counter distance between the fixed substrates 1a and 1b is constant. Therefore, since the rotating substrate 2 is interposed between the fixed substrates 1a and 1b, no matter how the rotating substrate 2 deviates and the opposing distance of the fixed substrates 1a and 1b changes with respect to the rotating substrate 2, This is because the total capacitance between the rotating substrate 2 and the fixed substrates 1a and 1b facing the upper and lower sides is constant.

  From the above, in the third embodiment, the total value obtained by adding the signals for electrostatic induction to the fixed electrodes of the fixed substrates 1a and 1b by the adder circuit 7 is constant even when the rotating substrate 2 fluctuates. It is possible to detect a movement amount, a movement speed, and the like from the signal. As a result, in this embodiment, it is not necessary to adopt a costly anti-shake structure, and the cost can be reduced.

  In the third embodiment, the rotating electrodes 5a and 5b are arranged on the rotating substrate 2 on both the front and back surfaces. However, as shown in FIG. 11, only the surface of the rotating substrate 2 has the rotating electrodes 5a1 at the positions indicated by the dotted lines. Alternatively, the case where the rotating electrode 5a2 is disposed only on the back surface of the rotating substrate 2 or the rotating electrode 5a3 is disposed only on the inner layer of the rotating substrate 2 can be included.

(Embodiment 4)
An electrostatic encoder according to the fourth embodiment of the present invention will be described with reference to FIGS. Parts corresponding or similar to those in FIGS. 1 to 4 are denoted by the same reference numerals. The encoder of the fourth embodiment is an electrostatic linear encoder. This electrostatic linear encoder has a configuration in which a movable substrate 2 that moves linearly in the directions of arrows P and Q in the figure is interposed between a pair of upper and lower fixed substrates 1a and 1b. The fixed substrates 1a and 1b are provided with fixed electrodes 4a and 4b; The moving substrate 2 is provided with moving electrodes 5a and 5b at positions symmetrical to the center line 3 and facing the fixed electrodes 4a and 4b, respectively. In addition, moving electrodes 5c and 5d are provided at positions facing the fixed electrodes 4c and 4d, respectively.

  Also in the fourth embodiment having the above configuration, as in the third embodiment, the total value obtained by adding the signals for electrostatic induction to the fixed electrodes of the fixed substrates 1a and 1b is constant even if the moving substrate 2 fluctuates. It becomes.

1 Fixed substrate 2 Rotating substrate (moving substrate)
3 Rotating shaft 4 Fixed electrode 5 Rotating electrode

Claims (5)

The machine moves from a plurality of electrodes (moving electrodes) provided on the moving substrate to an electrode (fixed electrode) provided on the fixed substrate in accordance with a relative position change between the fixed substrate and the moving substrate provided with electrodes on opposite surfaces. In an electrostatic encoder that electrostatically induces an electrical signal indicating a relative amount of relative position displacement,
The fixed substrate has at least one fixed electrode disposed at a position opposite to the moving electrode on the moving substrate and symmetrical to a predetermined center of the moving substrate. Type encoder. With a rotary encoder configuration in which a moving substrate is rotatable about an axis with respect to a fixed substrate, a plurality of moving electrodes on the rotating substrate are arranged at equal intervals in the circumferential direction of a predetermined radius, and
2. The electrostatic type according to claim 1, wherein the at least both fixed electrodes on the fixed substrate are respectively arranged at rotationally symmetric positions on a circumference having the same radius as the rotation center of the rotating substrate. Encoder.   The linear encoder configuration is such that the movable substrate is linearly movable with respect to the fixed substrate, and a plurality of the movable electrodes on the movable substrate are arranged in a linear direction at line-symmetrical positions with respect to a predetermined center line, and on the fixed substrate. 2. The electrostatic encoder according to claim 1, wherein the at least both fixed electrodes are arranged at positions symmetrical with respect to a predetermined center line of the movable substrate. The machine moves from a plurality of electrodes (moving electrodes) provided on the moving substrate to an electrode (fixed electrode) provided on the fixed substrate in accordance with a relative position change between the fixed substrate and the moving substrate provided with electrodes on opposite surfaces. In an electrostatic encoder that statically induces an electrical signal indicating a relative amount of relative position displacement,
A fixed substrate is disposed on each side of the movable substrate, and at least one fixed electrode is disposed on each of the fixed substrates at a position facing the movable electrode of the movable substrate. Type encoder.   The electrostatic encoder according to claim 4, wherein the moving electrode is provided at a symmetrical position that is equidistant from a predetermined center in a side view with respect to the moving substrate.

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