JPS59212710A - Displacement detector of electrostatic capacity type - Google Patents

Abstract

PURPOSE:To detect accurately the displacement of a moving object by providing an auxiliary electrode, which cancels the noise mixed into a receiving electrode from an input part, on the rear face of a fixed plate and relaxing and cancelling the noise with a correcting signal from this auxiliary electrode. CONSTITUTION:An auxiliary electrode 26 connected electrically to a receiving electrode 14 is provided in a position on the rear face of a fixed plate 10 corresponding to a one- side transmission electrode 12 forming each phase pair. That is, since the influence of noise components from a transmission electrode 12-4, where a connection pattern and the receiving electrode 14 approach each other most, is great in accordance with the positional relation between them, the auxiliary electrode 26 is provided in the position on the rear face corresponding to a transmission electrode 12-6 to which an AC voltage having a phase opposite to that of an AC voltage having 270 deg. phase shift, which is applied to the transmission electrode 12-4, is applied. As the result, a voltage signal having the same phase shift as the transmission electrode 12-6 is induced in the auxiliary electrode 26 and is connected and supplied to the receiving electrode 14, and thus, the noise mixed from the input part of the transmission electrode 12-4 to the receiving electrode 14 is cancelled effectively by the correcting signal from the auxiliary electrode 26.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a capacitive displacement detector, in particular, a device that detects the displacement of a moving body using both a moving electrode that moves in conjunction with the moving body and a fixed electrode that is fixed to the main body. The present invention relates to a capacitive displacement detector that detects based on a change in capacitance between electrodes.

BACKGROUND ART Displacement detectors that electrically convert the mechanical displacement of a measuring point or the displacement of a moving base and detect the amount of displacement have been well known, and this type of device is usually movably installed in the main body of the device. 1 encoder that detects the amount of movement of the moving body, converts it into electrical signal pulses, and counts the electrical signal pulses output by the encoder using 81 circuits, and converts the counted value into a digital signal. It is displayed digitally on the display.

Incidentally, photoelectric encoders, contact encoders, electrostatic encoders, and the like are conventionally known as encoders used in this type of apparatus.

A photoelectric encoder includes slits provided at equal intervals on the surface of a scale or rotating disk, and a light emitter and a light receiver that form an optical path through the slits of the scale or rotating disk. The scale or disk is moved or rotated according to the displacement, and the optical path formed between the light emitting and receiving devices is turned on and off to detect the displacement m of the moving body.

However, this photoelectric encoder has disadvantages in that the power consumption of the light emitter is large, the number of replacements of batteries increases, and when a large capacity battery is used, the entire device becomes large. Furthermore, in order to improve measurement accuracy, it is necessary to provide slits at intervals of several microns on a scale or rotating disk, which is difficult to manufacture and also causes miscounts due to clearance changes during operation. was there.

Furthermore, since contact type encoders use slits, brushes, etc. to detect the amount of displacement of a moving body, there is a problem that these slits and brushes are subject to rapid wear and that noise is easily mixed into the measurement signal.

On the other hand, electrostatic encoders do not consume as much power as photoelectric encoders, and do not have the problems of wear of brushes, slits, etc. and noise contamination like contact encoders. Widely used in equipment.

Conventional technology Conventionally, in an electrostatic encoder used in such a displacement detector, a capacitor is formed by arranging multiple pairs of electrode plates facing each other, and both electrode plates are moved relative to each other in accordance with the displacement of a moving object. The amount of mechanical displacement at this time was electrically detected as a change in capacitance of the capacitor.

For example, one electrode plate is arranged on a main scale at equal intervals, and the other electrode plate is arranged on an index scale that is placed facing the main scale at a certain interval, and the main scale or index scale is is slid parallel to the plate surface according to the displacement of the movable body, and the amount of displacement of the movable body is detected by the change in capacitance of the capacitor formed by the two electrode plates.

However, with conventional equipment (electrostatic encoders),
A voltage dividing circuit is formed using a capacitor made of the moving electrode plate, and the amount of displacement of the moving body is detected by detecting a voltage dividing ratio that changes depending on the capacitance of the capacitor. For this reason, in conventional devices, if the distance between the surfaces of the moving electrode plates that form the capacitor changes for some reason and the capacitance of the capacitor changes, or if the power supply voltage applied to the voltage divider circuit changes, In this case, the partial pressure output no longer corresponds accurately to the amount of displacement of the moving body, resulting in a drawback that accurate measurement cannot be performed.

Establishment process of the present invention In order to eliminate the above-mentioned conventional drawbacks, AC voltages of different phases are applied to one electrode of the plurality of electrode pairs, and a resident signal induced in the other electrode is detected, A capacitive displacement detector has been proposed that detects a phase change with respect to a reference phase of an output signal that changes based on the relative movement of both electrodes, and obtains each relative movement.

1 and 2 are explanatory diagrams showing the electrode structure of this proposed capacitive displacement detector, in which a fixed plate 10 consisting of a stator or scale plate fixed to the main body of the device is shown.
A plurality of transmitting electrodes 12 are arranged at equal intervals on the surface side of the JZ shown in FIG.
A strip-shaped receiving electrode 14 is provided in parallel to the receiving electrode 14 . Then, AC voltage signals having different phases are applied to each of the transmitting electrodes 12 .

On the other hand, a movable plate 16 consisting of a rotor or a movable scale plate that interlocks with the movable body is provided opposite to the fixed plate 1o. a coupled electrode 18,
Ground electrodes 20, which are disposed opposite to each other across the transmitting electrodes 12 and the receiving electrodes 14, are arranged alternately in the moving direction of the movable plate 16.

On the other hand, a voltage signal corresponding to the voltage signal of each transmitting electrode 12 is induced in the receiving electrode 14 via the coupling electrode 18,
Therefore, if the moving body is displaced while applying alternating current voltages with different phases to each of the transmitting electrodes 12, a signal with a phase corresponding to the amount of displacement of the moving body can be obtained from the receiving electrodes 14, and this reception By processing the phase of the signal output from the electrode 14 in the integrator 15 and comparing it with a predetermined reference phase, the displacement of the moving body can be accurately measured without being affected by fluctuations in power supply voltage, etc. becomes possible.

In recent years, there has been a demand for miniaturization of devices in order to improve their portability and operability, and when miniaturizing the proposed device mentioned above, the electrode area of each electrode becomes smaller and the distance between the electrodes becomes narrower. becomes. For this reason, the signal output voltage of the receiving electrode 14 decreases, resulting in a phenomenon in which the signal-to-noise ratio decreases due to the so-called noise mixture. Due to the narrow distance between the electrodes, the particles enter the receiving electrode 14 from the input part of the transmitting electrode 12 without passing through the coupling electrode 18, which causes a problem in that the detection accuracy of the device deteriorates.

Purpose of the Invention The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to miniaturize the device and provide a capacitive displacement device that can accurately detect the amount of displacement of a moving body. The purpose is to provide a detector.

Structure of the Invention In order to achieve the above object, the present invention includes a fixed plate fixed to a main body, and a movable plate facing the fixed plate and movably provided to the main body, and the surface of the fixed plate has a A plurality of transmitting electrodes arranged at equal intervals and a band-shaped receiving electrode arranged in parallel with the transmitting electrodes are provided, and the movable plate faces the transmitting electrodes and the receiving electrodes and capacitively couples the two electrodes. A coupling electrode is provided, and an AC voltage having one or more pairs of phase differences having different phases and mutually opposite phases is applied to each of the transmitting electrodes, and displacement of the moving plate is detected based on the output signal of the receiving electrode. In a capacitive displacement detector, an auxiliary electrode is provided on the back surface of the fixed plate at a position corresponding to one of the transmitting electrodes of at least a pair of phase subtraction transmitting electrodes and is electrically connected to the receiving electrode. The noise mixed into the receiving electrode from the input part of the transmitting electrode on the other side is relaxed and canceled by the correction signal from the auxiliary electrode induced by the transmitting electrode on the other side.

Embodiment FIGS. 5 to 8 show the electrode +R structure formed on the fixed plate of the capacitive displacement detector according to the present invention, and in this embodiment, FIGS. As shown, the fixing plate 10
An example is shown in which a wiring pattern 22 for applying a voltage to each transmitting electrode and an auxiliary electrode for canceling the mixed noise mentioned above are provided on the back side of the device. and the explanation thereof will be omitted.

In this embodiment, when applying AC voltages with different phases to each transmitting electrode 12, it is also possible to sequentially apply AC voltages with the same phase and difference to each transmitting electrode 12, but as shown in FIG. In this way, it is also possible to apply alternating current voltages of mutually opposite phases to a pair of adjacent transmitting electrodes so that noise from one side is canceled out by noise from the other side.

In FIG. 5 of this embodiment, each transmitting electrode 12-1 to 12
A wiring pattern 22 for supplying a voltage of a common phase to each of the common phase electrodes 12-8 is formed, and this wiring pattern and each of the transmitting electrodes 12-1 to 12-8 are electrically connected by leads 24.

In the device shown in FIG. 5, each transmitting electrode 12-1 to 12
-8, voltages with different phases of 0 degrees, 180 degrees, 90 degrees, and 270 degrees are applied sequentially, and here the phase is 0 degrees.
A pair of phase difference is formed between the transmission type 44A12-4 to which a signal of 180 degrees is input, and the transmission electrode 12-5 to which a voltage signal with an opposite phase, that is, 180 degrees shifted, is applied. , transmitting electrode 12-2 and transmitting electrode 12-3
A phase difference is formed between the transmission electrode 12-6 and the transmission type tIIi 12-7.

The characteristic feature of the present invention is that an auxiliary electrode is provided on the back surface of the fixed plate to cancel out the noise that enters the receiving electrode from the input section, and the noise is mitigated and canceled by the correction signal from the auxiliary electrode. That's what I did.

C in this embodiment is that an auxiliary electrode 26 that is electrically connected to the receiving electrode 14 is provided at the back surface position of the fixed plate 10 corresponding to one side of the transmitting electrode forming each of these phase differences. That is, in FIGS. 5 to 8, due to the positional relationship between the tangential pattern and the receiving electrode 14, there is a phase shift of 270 degrees because the influence of the noise component from the transmitting electrode 12-7, which is closest to both, is large. An auxiliary electrode 26 is provided at a position on the back surface of the transmitting electrode 12-6 to which an AC voltage of opposite phase is applied to the transmitting electrode 12-7 to which an AC voltage is applied.

As a result, a voltage signal having the same phase shift as that of the transmitting electrode 12-6 is induced in the auxiliary electrode 26, and this induced voltage signal is electrically supplied to the receiving electrode 14, so that the other transmitting electrode for phase subtraction, i.e. It becomes possible to effectively cancel the noise that enters the receiving type 114 from the input part of the transmitting electrode 1277 to which a 270 degree AC voltage is applied by the correction signal from the auxiliary electrode 26.

When each transmitting electrode 12 has a plurality of phase subtractors, the auxiliary electrodes 26 are provided at desired intervals in accordance with the amount of noise mixed into the receiving electrode 14 from the input section of the transmitting electrode, and are particularly provided when the amount of mixed noise is large. In some cases, it is effective to provide each of the transmitter electrodes on the back side of one of the transmitter electrodes of all the phase difference boxes. In this case, the auxiliary electrode 26
It is also possible to change the size of the electrode area.

In this embodiment, noise that enters the receiving electrode 14 without passing through the regular route, that is, noise other than the voltage signal induced from the transmitting electrode 12 to the receiving electrode 14 via the coupling electrode 18, that is, In order to effectively remove noise directly mixed into the receiving electrode 14, a seventh electrode is provided between the transmitting electrode 12 and the receiving electrode 14 as an auxiliary means.
As shown in FIG. 8, an isolated ground electrode 28 is provided to electrically isolate the two.

Further, as shown in FIGS. 6 to 8, an auxiliary ground electrode 30 is provided on the back side of the fixed plate 10 at a position outside the input connection part of the transmitting electrode 12, and an input terminal for supplying voltage signals to each transmitting electrode. The receiving electrode 1 is detoured along the surface of the fixing plate 10 from the
It is possible to prevent noise from being mixed into 4.

Furthermore, as shown in FIGS. 8 and 9, by providing a ground layer 32 inside the fixed plate 10, the transmission type [i12
It is also possible to prevent noise from entering the receiving electrode 14 through the inside of the fixed plate 10 from the input section of the isolated ground electrode 28, the auxiliary ground electrode 30. By appropriately providing the ground layer 32, together with the effect of the auxiliary electrode 26, the effect of preventing noise from entering the receiving electrode 14 is further exhibited, and the amount of movement of the moving object can be detected with extremely high accuracy. .

Specific Example Next, a specific example in which the device of the present invention is applied to a micrometer will be described.

■ Equipment configuration 1) Arrangement of fixed plate and movable plate A moving plate is placed on the spindle side and a fixed plate is placed on the main body side.

(2) Arrangement of electrodes and method of driving the same One set consisted of eight transmitting electrodes, and five sets were arranged at equal intervals on the circumference of the stator. Then, alternating current voltages having phases of 0 degrees, 45 degrees, 90 degrees, 135 degrees, 180 degrees, 225 degrees, and 270 degrees were sequentially applied to each set of transmitting electrodes, resulting in a so-called 8-set drive system.

Further, the auxiliary electrode was provided at a position on the back surface of the transmitting electrode to which an AC voltage having a phase opposite to that of the voltage introduced by the patterned electrical path closest to the receiving electrode was applied.

(3) Outline of micrometer applicable to this device In this specific example, the electrical angle per rotation of the rotor is 360° x 5 =
18006 phase change. In this specific example, if it is applied to a micrometer with a 1 μm reading of 0.5n+n+bits, a signal of 500 pulses per rotation of the rotor will be output, and in this case, a mechanical angle of 360 °
1μ
The reading of o1 is realized.

(4) Specific design values for the detection unit Distance between the transmitting electrode and the coupling electrode: 141 f1 mm or less Distance between the receiving electrode and the closest wiring pattern circuit @: 2 mm Electrode area of one transmitting electrode 61111112 Applied voltage of the transmitting electrode :3v Distance between transmitting electrode and auxiliary electrode! 1ift: 1mm Electrode area of auxiliary electrode: 6mm2 As a result, in this specific example, an auxiliary electrode is provided to cancel out the mixed noise, and as a result, the adverse effect of noise mixing on the receiving electrode is lower than in the proposed device described above that does not have an auxiliary electrode. could be effectively resolved.

That is, according to the proposed device that does not have an auxiliary electrode, the noise that enters the receiving electrode from the wiring pattern is approximately 200...v <s/xx22 (IB),
The maximum phase error at this time is 11°, and the maximum nonlinear error is approximately 3
It becomes μm.

In contrast, an auxiliary electrode was installed (but according to a specific example, the noise entering the receiving electrode from the wiring pattern was 40 mV (S
/N; 36 dB>, the maximum error at this time was 2.2 degrees, and the maximum non-linear error was suppressed to an extremely small error of 0.6 μm using the micrometer mentioned above. .

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, the fixing plate has a receiving electrode and a receiving electrode on the back side of the fixing plate corresponding to one transmitting electrode of at least a pair of phase-subtraction transmitting electrodes. As a result of providing a conductive auxiliary electrode, it is possible to effectively cancel out the noise entering the receiving electrode from the input section that applies AC voltage to the transmitting electrode. It becomes possible to detect displacement with extremely high precision.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the electrode structure of a capacitive displacement detector to which the present invention is applied; FIG. 2 is an explanatory diagram of each electrode provided on the fixed plate and moving plate of FIG. 1; The figure is an explanatory diagram showing input connections such as wiring patterns for applying AC voltage to each transmitting electrode, FIG. 4 is a side view of FIG. 3, and FIG. 5 is an illustration of a capacitive displacement detector according to the present invention. An explanatory diagram showing the electrode structure provided on the fixing plate side, FIG. 6 is a plane view of A=Ag7i in FIG. FIG. 3 is a diagram showing an embodiment of the structure. 10... Fixed plate, 12... Transmitting electrode, 14... Receiving electrode, 16... Moving plate, 18... Coupling electrode, 26... Auxiliary electrode, 28... Separated earth electrode, 30...Auxiliary earth electrode. Agent Patent attorney Yoshi 1) Kenji (1 idiot) Figure 1 I6 Figure 2 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Procedure amendment writing ability) Patent Office Mr. Commissioner, 1. Indication of the case 00W58 Patent Application No. 87218 2. Name of the invention Capacitive displacement detector (3. Person making the amendment. Relationship with the case. Patent applicant's office. 5, Shiba, Minato-ku, Tokyo. Chome 33-7 Name Sanso Seisakusho Co., Ltd. 4, Agent 5, Subject of amendment 1 [Detailed description of the invention in document 1, drawings. Written amendment to the above procedure (frog) July 29, 1982 1. Indication of the case 1982 Patent Application No. 87218 2. Name of the invention Capacitive displacement detector 3. Person making the amendment Relationship to the case Patent applicant Location 5-33-7 Shiba, Minato-ku, Tokyo Name Sanjo Seisakusho Co., Ltd. 4, Agent 5, Statement of the subject of the amendment 1 Document and drawing 6, Contents of the amendment Document 1, Name of the invention Capacitive displacement detector 2, Claims (1) ) It has a fixed plate fixed to the main body, and a movable plate facing the fixed plate and movably provided to the main body, and on the surface of the fixed plate, there are a plurality of transmitting electrodes arranged at equal intervals, and a plurality of transmitting electrodes arranged at equal intervals. and band-shaped receiving electrodes arranged in parallel with each other, and a coupling electrode facing across the transmitting electrode and the receiving electrode and capacitively coupling between the two electrodes is provided on the moving plate, and each of the transmitting electrodes has a different phase. In a capacitive displacement detector that applies an alternating current voltage and has one or more pairs of phase difference boxes that are in opposite phases to each other and detects the displacement of the moving plate based on the output signal of the receiving electrode, the back surface of the fixed plate is An auxiliary electrode that is electrically connected to the receiving electrode is provided at a position corresponding to at least one of the transmitting electrodes of the pair of phase difference boxes, and the auxiliary electrode is connected to the receiving electrode from the input part of the transmitting electrode on one side of the phase difference box. A capacitive displacement detector characterized in that the noise caused by the transmission is relaxed and canceled by the correction signal from the auxiliary electrode induced by the transmitting electrode on the other side. (2. The device according to claim (1) A capacitive displacement detector characterized in that auxiliary electrodes are provided corresponding to all transmitting electrodes forming a phase difference box in which applied voltage signals have opposite phases to each other. (3) Claims of Claims A capacitive displacement detector in the device according to scope (1) or (2), characterized in that an isolation ground electrode is provided between the transmitting electrode and the output electrode to electrically isolate them. 3 DETAILED DESCRIPTION OF THE INVENTION Industrial Field of Application The present invention relates to a capacitive displacement detector, and more particularly, to a capacitive displacement detector, which detects the displacement of a moving body by using both a moving electrode that moves in conjunction with the moving body and a fixed electrode that is fixed to the main body. The present invention relates to a capacitive displacement detector that detects based on changes in capacitance between electrodes. BACKGROUND ART Displacement detectors that electrically convert the mechanical displacement of a measuring point or the displacement of a moving base and detect the amount of displacement have been well known, and this type of device is usually installed in a movable manner in the main body of the device. The encoder detects the moving amount of the moving object and converts it into electrical signal pulses, and the electrical signal pulses output from the encoder are counted by a counting circuit, and the counted value is converted into a digital signal. It is displayed digitally on the display. Incidentally, photoelectric encoders, contact encoders, electrostatic encoders, and the like are conventionally known as encoders used in this type of apparatus. A photoelectric encoder includes slits provided at equal intervals on the surface of a scale or rotating disk, and a light emitter and a light receiver that form an optical path through the slits of the scale or rotating disk. The scale or disk is moved or rotated in accordance with the displacement ω to turn on and off the optical path formed between the light emitter and receiver, thereby detecting the amount of displacement of the moving body. However, with this rechargeable encoder, the light emitter is turned off.
There are disadvantages in that the electric power is large, the number of times the battery used is replaced increases, and if a battery with a large capacity is used, the entire device becomes large. Furthermore, in order to improve measurement accuracy, it is necessary to provide slits at intervals of several microns on a scale or rotating disk, which is difficult to manufacture and also causes problems such as miscounts due to clearance changes during operation. there were. Furthermore, since contact type encoders use slits, brushes, etc. to detect the amount of displacement of a moving body, there are problems in that these slits and brushes are subject to rapid wear and that noise is mixed into the measurement signal. On the other hand, electrostatic encoders do not consume as much power as photoelectric encoders, and do not have the problems of wear of brushes, slits, etc. and noise contamination like contact encoders. Widely used in equipment. Conventional technology Conventionally, in an electrostatic encoder used in such a displacement detector, a capacitor is formed by arranging multiple pairs of electrode plates facing each other, and both electrode plates are moved relative to each other in accordance with the amount of displacement of a moving object. The amount of mechanical displacement at this time was electrically detected as a change in the capacitor's static capacity. For example, one electrode plate is arranged on the main scale at equal intervals, and the electrode plate to be used is placed on the index scale, which is placed facing the main scale at a certain interval. The scale is slid parallel to the plate surface according to the displacement of the moving body, and at this time, the amount of displacement of the moving body is detected by the change in capacitance of the capacitor formed by both electrode plates. However, in the electrostatic encoder in the conventional device, a voltage dividing circuit is formed using a capacitor made of the moving electrode plate, and the displacement amount of the moving object is detected by detecting the voltage dividing ratio that changes according to the capacitance of the capacitor. was detected. For this reason, in conventional devices, when the distance between the surfaces of the movable electrode plates that form the capacitor changes for some reason and the capacitance of the capacitor changes, or when the power supply voltage applied to the voltage divider circuit changes, In this case, the partial pressure output no longer corresponds accurately to the amount of displacement of the moving body, resulting in a drawback that accurate measurement cannot be performed. Establishment process of the present invention In order to solve the above-mentioned conventional drawbacks, alternating current voltages of different phases are applied to one electrode of the plurality of electrode pairs, and the voltage signal induced in the other electrode is detected. A capacitive displacement detector has been proposed that detects a phase change with respect to a reference phase of an output signal that changes based on the relative movement of both electrodes to determine the relative movement amount. 1 and 2 are explanatory diagrams without showing the electrode structure of this proposed capacitive displacement detector, and a fixed plate 10 consisting of a stator or scale plate fixed to the device main body side.
As shown in FIG. 2, a plurality of transmitting electrodes 12 are arranged at equal intervals on the front side of the transmitting electrode 12, and a band-shaped receiving electrode 14 is provided in parallel with the transmitting electrodes 12. Then, AC voltage signals having different phases are applied to each of the transmitting electrodes 12. On the other hand, a movable plate 16 consisting of a rotor or a movable scale plate is provided opposite to the fixed plate 10 and which is interlocked with the movable body.
The movable plate 16 has a coupling electrode 18 disposed facing each other across the transmitting electrode 12 and the receiving electrode 14;
Ground electrodes 20 facing each other between the transmitting electrodes 12 and the receiving electrodes 14 are alternately arranged along the moving direction of the moving plate 16. On the other hand, a voltage signal corresponding to the voltage signal of each transmitting electrode 12 is induced in the receiving electrode 14 via the coupling electrode 18,
Therefore, if the moving body is displaced while applying alternating current voltages with different phases to each of the transmitting electrodes 12, an output signal with a phase corresponding to the amount of displacement of the moving body can be obtained from the receiving electrodes 14, and this reception quality 4 By processing the phase of the signal output from the cell 14 in the integrator 15 and comparing it with a predetermined reference phase, the amount of displacement of the moving object is accurately measured without being affected by fluctuations in power supply voltage, etc. becomes possible. In recent years, there has been a demand for miniaturization of devices in order to improve their portability and operability, and when miniaturizing the proposed device mentioned above, the electrode area of each electrode becomes smaller and the distance between the electrodes becomes narrower. becomes. Therefore, the signal output voltage of the receiving electrode 14 decreases, resulting in a phenomenon in which the S/N ratio decreases due to the so-called noise mixture. Due to the narrow distance between the electrodes, the particles enter the receiving electrode 14 from the input part of the transmitting electrode 12 without passing through the coupling electrode 18, which causes a problem in that the detection accuracy of the device deteriorates. Purpose of the Invention The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to miniaturize the device and provide a capacitive displacement device that can accurately detect the amount of displacement of a moving object. The purpose is to provide a detector. Structure of the Invention In order to achieve the above object, the present invention includes a fixed plate fixed to a main body, and a movable plate facing the fixed plate and movably provided to the main body, and having a movable plate on the surface of the fixed plate. is provided with a plurality of transmitting electrodes arranged at equal intervals and a band-shaped receiving electrode parallel to the transmitting electrodes, and the moving plate has transmitting electrodes and receiving type 4M.
coupling electrodes facing each other across the electrodes and capacitively coupling the two electrodes are provided, and applying an alternating current voltage having one or more pairs of phase differences having different phases and opposite phases to each other to each of the transmitting electrodes, In a capacitive displacement detector that detects the displacement of a moving plate based on the output signal of a receiving electrode, the back surface of the fixed plate corresponds to one of at least a pair of transmitting electrodes for phase difference. An auxiliary electrode that conducts with the receiving electrode is provided at a position where the noise is mixed into the receiving electrode from the input horn of the transmitting electrode on one side for phase difference, and a correction signal from the auxiliary electrode is induced by the transmitting electrode on the other side. It is characterized by relaxing and canceling out. Embodiment FIGS. 5 to 8 show the electrode structure formed on the fixing plate of the capacitive displacement detector according to the present invention, and in this embodiment, FIGS. As shown, the fixing plate 10
An example is shown in which a wiring pattern 22 for applying a voltage to each transmitting electrode and an auxiliary electrode for canceling the mixed noise mentioned above are provided on the back side of the device. It is attached and the explanation is omitted. In this embodiment, when applying alternating current voltages with different phases to each transmitting electrode 12, alternating current voltages having the same phase difference are sequentially applied to each transmitting electrode 12. In FIG. 5 of this embodiment, each transmitting electrode 12-1 to 12
A wiring pattern 22 for supplying a voltage of a common phase to each of the common phase electrodes 12-8 is formed, and this wiring pattern and each of the transmitting electrodes 12-1 to 12-8 are electrically connected by leads 24. In the apparatus shown in FIG. 5, each transmitting electrode 12-1 to 1
Voltages with different phases of 0 degrees, 90 degrees, 180 degrees, and 270 degrees are sequentially applied to the transmitter electrode 12-8, and the transmitter electrode 12-5 receives a signal with a phase of 0 degrees. On the other hand, a pair of phase difference electrodes are formed with the transmitting electrode 12-7 to which a voltage signal of opposite phase, that is, 180 degrees shifted, is applied, and similarly, the transmitting electrode 12-2 and the transmitting electrode 12-4
The transmitting electrode 12-1 and the transmitting electrode 12-3 each form an out-of-phase phase. The characteristic feature of the present invention is that an auxiliary electrode is provided at the center of the fixing plate to cancel out the noise that enters the receiving electrode from the human power section (B). This is because +j cancels out and i becomes 1.
In this embodiment (well, at the back side position of the fixed plate 10 corresponding to the transmitting electrode on one side forming each of these phase differences,
An auxiliary electrode 26 is provided which is electrically connected to the receiving 7R pole 1/I. In other words, in Figure 5 and J3 in Figure 7158, the positional relationship between the wiring pattern and the receiving power 14 (1) + r is the closest transmitting power (~12-/
Since the influence of the nose r component from I is large, the transmitting electrode 12- to which an AC voltage is applied that shifts the phase shift of the mark 270[to the right]
4, a transmitting electrode 12 to which an AC voltage of opposite phase is applied.
The auxiliary iG1 sub 26 is stepped on the back side (fr) of the auxiliary electrode 26. As a result, a voltage signal having the same phase shift as that of the transmitting electrode 12-6 is induced in the auxiliary electrode 26, and this induced voltage signal is electrically supplied to the receiving electrode 14, and as a result, noise mixed into the receiving electrode 1/I from the input part of the other transmitting electrode for phase difference, that is, the transmitting electrode 12-4 to which a 270 degree AC voltage is applied, is assisted. This can be effectively canceled out by the correction signal from the electrode 26. This auxiliary electrode 26 (if each transmitting electrode 12 has a plurality of phase difference signals, the signal from the input part of the transmitting electrode to the receiving electrode 14) They are provided as desired in response to the amount of mixed noise, and especially when the amount of mixed noise is large, it is effective to provide them at the back side of one of the transmitting electrodes for all phase differences.
In this case, the auxiliary electrode 2
It is also possible to change the size of the electrode surface phase of G. In this embodiment, noise that enters the receiving electrode 14 without going through the normal route, that is, noise other than the voltage signal induced from the transmitting electrode 12 to the receiving electrode 14 via the coupling electrode 18, that is, the noise that enters the receiving electrode 14 without passing through the normal route, In order to effectively remove noise that directly enters the receiving electrode 14 from the transmitting electrode 12, a seventh
As shown in FIG. 8, an isolation ground electrode 28 is provided to electrically isolate the two. Further, as shown in FIGS. 6 to 8, an auxiliary ground electrode 30 is provided on the back side of the fixed plate 10 at a position outside the input connection part of the transmitting electrode 12, and supplies a voltage signal to each transmitting electrode. The receiving electrode 1 is detoured along the surface of the fixed plate 10 from the input section
It is possible to prevent noise from being mixed into 4. Furthermore, as shown in FIG. 8 and FIG.
It is also possible to prevent noise from entering the receiving electrode 14 from the input part of the i12 through the inside of the fixed plate 10, and the isolated ground electrode 28, the auxiliary ground electrode 30. By appropriately stepping the ground layer 32, combined with the effect of the auxiliary electrode 26, the effect of preventing noise from entering the receiving electrode 14 is further exerted, and the movement M of the moving body can be detected with extremely high precision. Specific Example Next, a specific example in which the device of the present invention is applied to a micrometer will be explained. ■ Device configuration (1) Arrangement of fixed plate and movable plate The movable plate is on the spindle side and the fixed plate is on the main body side. Arrangement. (2) Arrangement of electrodes and their driving method Eight transmitting electrodes were made of one dark blue color and five sets were arranged at equal intervals on the circumference of the stator. degrees, 135 degrees, 180 degrees, 225 degrees, 2
An alternating current voltage having a phase of 70 degrees was applied, resulting in a so-called 8-set drive system. Further, the auxiliary electrode was provided at a position on the back surface of the transmitting electrode to which an AC voltage having a phase opposite to that of the voltage introduced by the patterned electrical path closest to the receiving electrode was applied. (3) Outline of the micrometer applicable to this device In this specific example, the electrical angle per rotation of the rotor is 360' x 5
= 18006 phase 7 - In this specific example, when applied to a micrometer of only 1 μm VA with 0.5 mm pitch, a signal of 500 pulses per rotation of the rotor will be output, and in this case, 1 Geomechanical angle 36
The phase of o° is 360°1500÷5=360'/
100. That is, by dividing the 360° phase by 100, a reading of 1 μm is achieved. (/I) Specific design values for the detection unit Distance between the transmitting electrode and the coupling electrode Ni: 1 mm J:I. Distance between the lower receiving electrode and the closest wiring pattern circuit: 2 mm Electrode area of one transmitting electrode: 6 mm + 2 Applied voltage of transmitting electrode: 3 V Distance between transmitting electrode and auxiliary electrode: 1 mm Electrode area of auxiliary electrode: 6 mm 2 Results In this specific example, as a result of providing an auxiliary electrode for canceling mixed noise, it was possible to effectively eliminate the adverse effects of noise mixed into the receiving electrode, compared to the above-mentioned proposed device that does not have an auxiliary electrode. In other words, according to the proposed device that does not have an auxiliary electrode, the noise that enters the receiving electrode from the wiring pattern is approximately 200mv (S/N = 22dB>), and the maximum phase error at this time is 11°, which is equivalent to the above 1μm reading. For micrometers, the maximum nonlinear error is approximately 3μ
Become a river. On the other hand, according to a specific example in which an auxiliary electrode is provided, the noise that enters the receiving electrode from the wiring pattern is reduced to 40 v v (S / N = 36 dB), and the maximum error in this case is 2.2 °, and the micrometer above has iJ3, and its maximum nonlinear error is 0.
．． We were able to suppress the error to an extremely small error of 6 μm. As described in detail, according to the present invention, on the back surface of the fixing plate, at a position on the back surface of the fixing plate corresponding to one of the transmitting electrodes of at least a pair of phase-subtraction transmitting electrodes, As a result of providing an auxiliary electrode that conducts with the receiving electrode, it is possible to effectively cancel out the noise that enters the receiving electrode from the input section that applies alternating voltage to the transmitting electrode, which allows for easy movement even though the device is smaller. It becomes possible to detect the displacement of the body with extremely high precision. 4. Brief description of the drawings Figure 1 shows and explains the electrode structure of a capacitive displacement detector to which the present invention is applied. Figure 2 is an explanatory diagram of each electrode installed on the fixed plate and moving plate in Figure 1. Figure 3 is an illustration of the AC voltage applied to each transmitting electrode - twist + j pattern and its input connection. 4 is a side view of FIG. 3, FIG. 5 is an explanatory diagram showing the electrode structure provided on the fixed plate side of the capacitive displacement detector according to the present invention, and FIG. 6 is a side view of FIG. A sectional view taken along line A in FIG. 5, and FIGS. 7, 8, and 9 are views of other embodiments that do not show the electrode structure provided on the fixing plate of the device of the present invention. 10... Fixing plate, 12... Transmitting electrode, ]4... Receiving electrode, 16... Moving plate, 18... Coupling electrode, 26... Auxiliary electrode, 28... Isolated earth electrode, 330... Auxiliary earth Electrode. Agent: Patent attorney Furu 1) Kenji (and 1 other person)

Claims (1)

[Claims] <1) It has a fixed plate fixed to the main body and a movable plate facing the fixed plate and movably provided on the main body, and the movable plate is arranged at equal intervals on the surface of the fixed plate. A plurality of transmitting electrodes and a band-shaped receiving electrode are provided in parallel with the transmitting electrodes, and a coupling electrode is provided on the moving plate to face the transmitting electrodes and the receiving electrodes and to capacitively couple the two electrodes. , a capacitive displacement detection method in which alternating current voltages having one or more pairs of phase differences having different phases and mutually opposite phases are applied to each of the transmitting electrodes, and displacement of the moving plate is detected based on the output signal of the receiving electrode. In the device, an auxiliary electrode is provided on the back surface of the fixed plate at a position corresponding to one of the transmitting electrodes of at least a pair of phase subtraction transmitting electrodes and is electrically connected to the receiving electrode. A capacitive displacement detector characterized in that noise mixed into a receiving electrode from an input section of the sensor is relaxed and canceled by a correction signal from an auxiliary electrode induced by a transmitting electrode on the other side. (2. The device according to claim (1), characterized in that the auxiliary electrode is provided corresponding to all the transmitting electrodes forming a phase subtraction in which the applied voltage signals have opposite phases to each other. Mold displacement detector. (3) The device according to claim (1) or (2), characterized in that an isolation ground electrode is provided between the transmitting electrode and the output electrode to electrically isolate them. Capacitive displacement detector.