JP2010276524A - Electrode system of electrostatic proximity sensor having excellent noise resistance, and electrostatic proximity sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode system of an electrostatic proximity sensor, and the electrostatic proximity sensor, mountable easily on a curved mounted surface such as a vehicle bumper easily along the curve of the mounted surface without impeding its design, and without obstructing surface painting or the like, capable of detecting evenly detection objects at close range, having high environment resistance having small sensitivity reduction and stable operability even when having heavy rainfall or freezing, or adhesion of mud, a snow melting agent or the like, and operable stably without malfunction even under a noise environment wherein a strong electromagnetic wave such as car radio exists. <P>SOLUTION: A shield electrode film is formed on an insulating base, and the shield electrode film is covered with an insulating film, and a first belt-like electrode film A and a second belt-like electrode film B narrower than the first belt-like electrode film are arranged close in parallel on the insulating film. The shield electrode film surrounds the outer edge of the first and second belt-like electrode films from the surface direction, and the same voltage as the first and second belt-like electrode films is applied thereto, and further, a peripheral part of the shield electrode film is projected from the outer edge of the first and second belt-like electrode films. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electrode system of an electrostatic proximity sensor that is thin and can be mounted on a curved mounting surface and has excellent noise resistance, and a proximity sensor using this electrode system, for example, on the surface of an automobile bumper. It is effective for use in detecting a human body or the like that is mounted and close to the bumper.

  The electrostatic proximity sensor is disclosed in, for example, Japanese Patent Application Laid-Open No. 2003-202383 (Patent Document 1) and JPWO 2004/059343 (Patent Document 2).

  In Patent Document 1, an electrode made of a flat metal plate disposed in an object detection region, a charging system having a DC power source, a discharging system having a current detecting means, and the charging for the electrode are described. A proximity switch is disclosed that includes a switch that alternately switches a system and the discharge system at a predetermined switching frequency, and detects a capacitance between a detected object and the electrode as a current flowing through the discharge system. .

  Furthermore, in Patent Document 1, in order to detect an approaching object with high sensitivity, both are made of metal plates of the same size formed in a flat plate shape, and are arranged in parallel on substantially the same plane in the object detection region. The first and second electrodes, a charging system having a DC power source, a discharging system having a current detecting means, and the first and second electrodes are alternately switched between the charging system and the discharging system at a predetermined switching frequency. A configuration comprising switch means is also disclosed.

  In Patent Document 2, the first detection electrode and the second detection electrode, both of which are in the shape of strips, have heights of electrode surfaces in a U-shaped groove of a shield electrode (shield electrode) formed in a rail shape with a U-shaped cross section. An electrode system accommodated in a different state and a proximity sensor using the electrode system are disclosed. In this sensor, the opening direction of the U-shaped groove of the shield electrode is a detection region, and the other direction is surrounded by the shield electrode in a U shape to be a non-detection region.

  When the object to be detected is separated from the two detection electrodes by a sufficient distance, the capacitance generated by the object to be detected on the two detection electrodes is not so large, and the change due to the distance is slow. When it falls below a certain level, it suddenly increases. This sudden increase first occurs at the detection electrode closer to the detection target. As a result, the difference between the two capacitances increases rapidly.

  Therefore, if the two capacitances are measured and the difference output is taken out, the level state of the difference output changes greatly (abrupt increase) when the detected object comes close to a certain point. Due to this sudden increase, the approach of the detected object can be detected.

  The proximity sensor described above is used as a sensor for automatically preventing finger pinching in a sliding door type or door type automatic opening / closing door attached to a vehicle such as a wagon car.

JP 2003-202383 A JPWO 2004/059343 gazette

  For example, in automobiles, there is a particular demand for safety confirmation of the vehicle's front and rear close distance, which is a blind spot from the driver. For this reason, for example, a monitor camera that captures and displays a video at a close distance in the front-rear direction of the vehicle is provided. However, the monitor camera also has a blind spot, and for example, it was difficult to detect with high accuracy the existence of an infant bent in a narrow space under the bumper. The blind spot of the monitor camera can be reduced to some extent by widening the photographing lens. However, excessive widening is unsuitable for this kind of safety confirmation application because it increases the distortion of the image and lowers the visibility.

  As a candidate means for reliably detecting an obstacle such as an infant existing at a very short distance in the front-rear direction of the vehicle, for example, use of a rail-shaped proximity sensor disclosed in Patent Document 2 can be considered. If this proximity sensor is mounted along the width of the bumper, the presence of an infant hidden in the blind spot space below the bumper will be detected with high accuracy.

  However, the proximity sensor of Patent Document 2 has a three-dimensional structure in which the first detection electrode and the second detection electrode body are housed in a shield electrode having a U-shaped groove with different heights. This three-dimensional structure is a structure that is necessary to shield the induced noise from outside the detection area, but mounting such a three-dimensional proximity sensor on, for example, an automobile bumper greatly hinders the design of the bumper, Moreover, the problem that it also becomes obstructive of surface coating arises.

  In addition, the vicinity of the bumper of an automobile is a part that is most severely exposed to a natural environment such as wind and rain, road conditions, and the like, and a sensor mounted on this part is required to have particularly high environmental resistance. Patent Documents 1 and 2 do not disclose effective means for solving these problems.

  The present invention has been made in view of the above problems, and its purpose is not to hinder the design of a curved mounting surface such as an automobile bumper, nor to obstruct surface coating or the like. In addition, it can be easily mounted along the curved surface of the mounting surface, can detect all objects to be detected at close range, and even if it is exposed to heavy rain, freezing, mud, snow melting agent, etc., the decrease in sensitivity is small. Providing an electrode system for an electrostatic proximity sensor that has high environmental resistance that can operate stably and that can operate stably without malfunction even in a noise environment where strong electromagnetic waves such as car radio waves exist, and a proximity sensor that uses this electrode system There is to do.

The electrode system of the electrostatic proximity sensor according to the present invention is specified by the following (11) to (18).
(11) Provide an insulating base that is a dielectric (12) Provide a shield electrode film disposed on the upper surface of the insulating base (13) Provide a first insulating film that is a dielectric covering the upper surface of the shield electrode film (14) Provide first and second strip electrode films disposed on the top surface of the first insulation film. (15) Provide a second insulation film that is a dielectric covering the top surfaces of the first and second strip electrode films. (16) The first strip electrode film and the second strip electrode film have substantially the same length and are arranged close to each other in parallel. (17) The width of the first strip electrode film is the width of the second strip electrode film. (18) The shield electrode film extends so as to surround the portion where the first and second strip electrode films are disposed.

The electrostatic proximity sensor according to the present invention is specified by the following (21) to (28).
(21) Electrostatic proximity sensor provided with an electrode system and a circuit system. (22) The electrode system includes a dielectric insulating base, a shield electrode film disposed on the top surface of the insulating base, and a shield electrode. A first insulating film that is a dielectric covering the upper surface of the film, first and second strip electrode films disposed on the upper surface of the first insulating film, and a dielectric covering the upper surfaces of the first and second strip electrode films (23) The first strip electrode film and the second strip electrode film have substantially the same length and are juxtaposed in parallel. (24) The width of the first strip electrode film is the first. It must be larger than the width of the two-band electrode film. (25) The shield electrode film should extend so as to surround the periphery of the portion where the first and second band-shaped electrode films are disposed. Application means and difference detection means are provided. (27) Voltage application The stage applies a substantially equal voltage to each of the first strip electrode film, the second strip electrode film, and the shield electrode film, and repeatedly changes the applied voltage. (28) The difference detecting means Output a voltage signal corresponding to the difference between the accumulated charge amount and the accumulated charge amount of the second strip electrode film.

  It can be easily mounted on the curved mounting surface of an automobile bumper or the like along the curved surface of the mounting surface without obstructing the design and without hindering surface coating. Detecting objects can be detected evenly, and even if there is heavy rain or freezing, mud or snow-melting agent, etc., it has high environmental resistance that can operate stably with little decrease in sensitivity, and there is strong electromagnetic waves such as car radio It is possible to realize an electrostatic proximity sensor electrode system and an electrostatic proximity sensor that can operate stably without malfunction even in a noisy environment.

It is the top view which shows 1st Embodiment of the electrode system of the electrostatic proximity sensor which concerns on this invention, and its partial sectional view. 1 is a circuit diagram showing a first embodiment of an electrostatic proximity sensor circuit system using an electrode system of the present invention. FIG. It is a figure which shows the proximity | contact thing detection range at the time of mounting | wearing the vehicle bumper with the proximity sensor of this invention. It is a top view which shows 2nd-4th embodiment of the electrode system of the electrostatic proximity sensor which concerns on this invention. It is a top view which shows 5-7 embodiment of the electrode system of the electrostatic proximity sensor which concerns on this invention. It is a top view which shows 8th Embodiment like the modification of the electrode system of the electrostatic proximity sensor which concerns on this invention. It is a circuit diagram which shows 2nd Embodiment of the electrostatic proximity sensor circuit system which concerns on this invention. It is a circuit diagram which shows 3rd Embodiment of the electrostatic proximity sensor circuit system which concerns on this invention. It is the top view and sectional drawing which show 9th Embodiment of the electrode system of the electrostatic proximity sensor which concerns on this invention. It is a top view which shows 10th Embodiment of the electrode system of the electrostatic proximity sensor which concerns on this invention.

=== First Embodiment of Electrode Proximity Sensor Electrode System According to the Invention ===
FIG. 1 shows a first embodiment of an electrode system of an electrostatic proximity sensor according to the present invention by a plan view and a partial sectional view with exaggerated thickness.

  The electrode system 20 of the electrostatic proximity sensor shown in the figure is used by being mounted on a mounting surface such as an automobile bumper, and a detection region is a spatial region on the side surface opposite to the mounting surface. . The mounting is performed using an adhesive, a pressure sensitive adhesive, or the like, but the entire electrode system 20 can be mounted in a plane along a curved mounting surface such as an automobile bumper by adopting a thin strip-like flexible configuration. Easy to do. Thereby, the electrode system 20 of the proximity sensor can be mounted across the entire width of the bumper without hindering the design of the bumper which is the mounting surface, and without forming a protrusion that hinders painting or the like. it can.

  The electrode system 20 of the proximity sensor includes a first strip electrode film A, a second strip electrode film B, a shield electrode film S, and the electrode films A, B, and S that are insulated from each other and insulated from the mounted body. The insulating base 30 and the insulating film 31 are isolated.

  The first strip electrode film A is formed to have a predetermined length and width. The second strip electrode film B has the same length as the first strip electrode film A, and is formed by narrowing only the width. The first strip electrode film A and the second strip electrode film B are arranged close to each other in parallel in a state of being aligned in the plane direction. The shield electrode film S is formed to protrude and spread so as to surround the periphery of the portion where the first and second strip electrode films A and B are disposed. The shield electrode film S is formed on the insulating base 30 and is insulated from a mounted body such as an automobile bumper.

  The upper surface of the shield electrode film S and the upper surfaces of the first and second strip electrode films A and B are each covered with an insulating film that is a dielectric. The shield electrode film S and the first and second strip electrode films A and B are insulated and separated by an insulating film 31 which is a dielectric. Each insulating film 31 is formed by laminating by attaching an insulating film or applying or printing an insulating material.

  The periphery of the shield electrode film S surrounds the outer edges of the first and second strip electrode films A and B from the surface direction. At this time, a creepage distance (protrusion width) d of a certain degree or more is secured between the outer edge of the first and second strip electrode films A and B and the outer edge of the shield electrode film S.

  Further, the proximity sensor electrode system 20 shown in FIG. 1 is provided with an annular shield electrode film 24 that surrounds the first and second strip electrode films A and B on the same plane from the surface direction. The annular shield electrode film 24 is formed on the same layer surface with respect to the first and second strip electrode films A and B, and is conductively connected to the shield electrode film S located below the first and second strip electrode films A and B through vias 25. Yes. The upper side surface of the annular shield electrode film 24 is covered with an insulating film 31 that is a dielectric, together with the first and second strip electrode films A and B.

=== Embodiment of Circuit System of Electrostatic Proximity Sensor ===
FIG. 2 shows a circuit system of an electrostatic proximity sensor using the electrode system 20 shown in FIG.
In the figure, SIA represents a connection terminal of the first strip electrode film A, SIB represents a connection terminal of the second strip electrode film B, and SIS represents a connection terminal of the shield electrode film S. Further, Ca represents a capacitance formed on the first strip-shaped electrode film A due to the proximity of the detected body, and Cb represents a capacitance formed on the second strip-shaped electrode film B due to the proximity of the detected body.

  When a detection object approaches the detection region of the proximity sensor electrode system 20, capacitances Ca and Cb are generated in the first and second strip electrode films A and B, respectively, by the detection object. The capacitances Ca and Cb increase as the detected object approaches the strip electrode films A and B. Capacitances Ca and Cb when approached are such that the first strip electrode film A has the same length as the second strip electrode film B but is formed wider and the electrode area is relatively large. Becomes relatively larger than Cb. By approaching the level of the difference in capacitance (Ca−cb) with a predetermined threshold, the approach of the detected object can be detected.

  In order to perform this detection, the illustrated circuit system includes a charge / discharge circuit, first and second charge-voltage conversion circuits, a differential circuit, and voltage application means (active shield drive means).

  In the charging / discharging circuit, two predetermined voltages Vs1, Vs2 (Vs1> Vs2) having different potentials are periodically and alternately applied to the connection terminals SIA, SIB of the first and second strip electrode films A, B by the switching circuit Sas. To charge and discharge the electrostatic capacitances Ca and Cb formed by the first and second strip electrode films A and B, respectively. This charging / discharging circuit may be formed independently, but in the illustrated embodiment, it is configured with voltage applying means described later.

  The first and second charge-voltage conversion circuits are configured by using operational amplifiers (operational amplifiers) 51 and 52, and charge charges (accumulated charges charged by voltage application) of the first and second strip electrode films A and B are used. Voltage conversion is performed for each of the electrode films A and B.

  The differential circuit is configured by using an operational amplifier 53, resistors R1 and R2, and a capacitive element C2, and extracts a difference (Va−Vb) between the output voltages Va and Vb of the first and second charge voltage conversion circuits. Output. This difference output (Va−Vb) is output through an active low-pass filter (LPF) 54. Based on this output voltage Vo (= Va−Vb), the presence / absence of the object to be detected is determined.

  In the above-described configuration, the operational amplifiers 51 and 52 constituting the first and second charge-voltage conversion circuits have negative feedback capacitance elements Cfa and Cfb and discharge reset switching circuits Sa and Sb between the output and the inverting input (−). Are connected, and the first potential Vs1 and the second potential Vs2 having different potentials are periodically switched by the switching circuit Sas and applied to the non-inverting input (+). Then, the first potential Vs1 and the second potential Vs2 applied by switching to the non-inverting input (+) are also applied to the shield electrode film S.

=== Charging / Discharging Circuit and Voltage Application Unit (Active Shield Driving Unit) ====
In FIG. 2, the first potential Vs1 and the second potential Vs2 are periodically switched and applied to the non-inverting input (+) of the operational amplifiers 51 and 52 by the switching circuit Sas. The operational amplifiers 51 and 52 perform a negative feedback operation by the negative feedback capacitance elements Cfa and Cfb and the discharge reset switching circuits Sa and Sb so that the inverting input (−) becomes the same potential as the non-inverting input (+). That is, the negative feedback operation is performed so that the inverting input (−) is virtually short-circuited to the non-inverting input (+).

  Here, when the first potential Vs1 is applied to the non-inverting input (+) of the operational amplifiers 51 and 52, the inverting input (−) becomes the first potential Vs1 following this. Similarly, when the second potential Vs1 is applied to the non-inverting input (+) of the operational amplifiers 51 and 52, the inverting input (−) also becomes the second potential Vs2.

  Therefore, when the first and second strip electrode films A and B are connected to the inverting inputs (−) of the operational amplifiers 51 and 52 through the connection terminals SIA and SIB, the first and second strip electrode films A and B are connected to the first and second strip electrode films A and B. The first potential Vs1 and the second potential Vs2 are periodically switched and applied to the difference voltage (Vs1−Vs2) between the potentials Vs1 and Vs2 and the capacitances Ca and Cb formed by the strip electrode films A and B. Charge / discharge of the corresponding charge is performed for each. The charge and discharge charges of Ca and Cb are converted into voltages Va and Vb by charge-voltage conversion circuits formed by operational amplifiers 51 and 52, respectively.

  The discharge reset switching circuits Sa and Sb of the operational amplifiers 51 and 52 are turned on and off in a constant synchronous relationship with the switching circuit Sas, and are turned on each time the first potential Vs1 and the second potential Vs2 are switched, and the negative feedback capacitance element Cfa. , Cfb is reset to discharge. As a result, every time the first potential Vs1 and the second potential Vs2 are switched, the charges charged in the Ca and Cb change in voltage.

  At this time, since the first potential Vs1 and the second potential Vs2 are also applied to the shield electrode film S, the first and second strip electrode films A and B are held at the same potential as the shield electrode film S. As a result, charge is not charged or discharged between the first and second strip electrode films A and B and the shield electrode film S, and the apparent capacitance between them is equivalently zero.

  In this manner, a charge / discharge circuit for charging / discharging the electrostatic capacitances Ca and Cb formed by the first and second strip electrode films A and B is formed, and the first and second strip electrode films A are formed. , B and the shield electrode film S are formed with voltage applying means (active shield driving means) for reducing the equivalent capacitance to zero.

  The shield electrode film S on which the active shield drive is performed is interposed between the first and second strip electrode films A and B and the mounting surface to electrically shield the first and second electrodes. The detection operation by the two strip electrode films A and B can be accurately performed without being affected by the mounted body.

=== Noise resistance ===
The electrostatic proximity sensor using the electrostatic electrode system has a problem that it is likely to malfunction due to the influence of environmental noise such as car radio. However, in the proximity sensor electrode system 20 of the present invention, the first belt-shaped sensor is used. By arranging the electrode film A and the second strip-shaped electrode film B in parallel in a state of being aligned in the plane direction, it is possible to obtain high environmental noise resistance.

  That is, electromagnetic noise having the same phase, amplitude, and the like is induced in the strip-shaped electrode films A and B that are close to each other and have the same length. Such noise can be canceled and removed easily and with high efficiency by differential cancellation. This makes it possible to operate stably without malfunction even in a noise environment where strong electromagnetic waves such as car radio exist.

=== Environmental resistance ===
As a main usage pattern of the proximity sensor electrode system 20 according to the present invention, it is assumed that the proximity sensor electrode system 20 is used by being mounted on an automobile bumper. However, the vicinity of the bumper of an automobile is a part that is most severely exposed to a natural environment such as wind and rain, road conditions, and the like, and particularly high environmental resistance is required for a sensor attached to this part. When the proximity sensor electrode system 20 described above is mounted on a bumper, heavy rainfall, freezing, adhesion of mud, snow melting agent, or the like is expected.

  For this reason, in the proximity sensor electrode system 20 of the present invention, as shown in FIG. 1, the surfaces of the shield electrode film S and the first and second strip electrode films A and B are covered with an insulating film 31 that is a dielectric. A certain creeping distance (protrusion width) d is secured between the outer edge of the first and second strip electrode films A and B and the outer edge of the shield electrode film S.

  First, by covering the surfaces of the shield electrode film S and the first and second strip electrode films A and B with an insulating film 31 that is a dielectric, rainwater, mud, snow melting agent, etc. are in direct contact with the electrodes A and B. Erosion can be prevented.

  Next, by securing a creepage distance d of a certain extent or more between the outer edge of the first and second strip electrode films A and B and the outer edge of the shield electrode film S, the first and second strip electrode films A and B are secured. It is possible to avoid that the detection operation by is hindered by the resistive conductive water film.

  The surfaces of the first and second strip electrode films A and B are protected by the insulating film 31. If the surface of the insulating film 31 is wetted with rainwater or water containing a snow melting agent to form a water film, The film covers the first and second strip electrode films A and B as a resistive conductive film.

  Since this resistive conductive film covers the electrode system 20 and the mounted body, the first and second strip electrode films A and B are covered with the conductive film conductively connected to the mounted body. As a result, the normal detection operation is hindered.

  However, in the electrode system 20 of the present invention, the first and second creeping distances d are secured between the outer edge of the first and second strip electrode films A and B and the outer edge of the shield electrode film S to some extent. The resistive conductive film covering the two-band electrode films A and B can be separated from the mounted body in an alternating manner at the creeping distance d. Thereby, the influence on the detection operation by the resistive conductive film can be avoided.

  A water film such as rainwater or water containing a snow melting agent forms a resistive conductive film of several hundred K ohms to several M ohms per 1 cm 2, but the resistive conductive film of the portion covering the shield electrode film S is A distributed capacitance is formed between the shield electrode film S and the insulating film 31. By forming this distributed capacity over a certain creepage distance d, a low-pass filter separation band that interrupts the inside and outside of the annular portions surrounding the strip electrode films A and B in an alternating manner is distributed. Thereby, even if there is intense rain or freezing, adhesion of mud, snow melting agent, etc., high environmental resistance that can be stably operated with small sensitivity reduction can be obtained.

=== Creepage distance (protruding width) d ===
The creepage distance d is the resistivity of the resistive conductive film formed by a water film such as rain water or water containing a snow melting agent, the charge / discharge drive frequency of the first and second strip electrode films A and B, and the creepage distance d portion. The thickness of the insulator covering the shield electrode film S and the dielectric constant can be determined. Specifically, the creeping distance d may be set so that low-pass filters having a cut-off frequency lower than the charge / discharge driving frequency of the strip electrode films A and B are distributed. In a general structure, the creepage distance d is preferably 1 cm or more, more preferably 2 cm or more.

=== Use status of proximity sensor electrode system ===
FIG. 3 shows an example of use in which the proximity sensor electrode system 20 of the present invention is mounted on the bumper 11 of the automobile 10. In the figure, (a) shows a top view and (b) shows a side view.
As shown in the figure, the electrode system 20 of the proximity sensor of the present invention conforms to the curved surface shape of the bumper 11 without making a protrusion that obstructs the design and painting along almost the entire width of the automobile bumper 11. Can be mounted in a planar shape.

  The electrode system 20 of the proximity sensor thus mounted can uniformly detect an object approaching a space of 40 to 50 cm around the periphery including the lower side of the bumper 11 as indicated by hatching in the drawing. it can. For example, even if an infant or the like is hidden in the blind spot space below the bumper 11, it can be reliably detected.

=== Second to Fourth Embodiments of Proximity Sensor Electrode System ===
FIG. 4 shows second to fourth embodiments of the electrode system of the electrostatic proximity sensor according to the present invention.
In the electrode system 20 shown in FIG. 6A, the first and second strip electrode films A and B are provided on the shield electrode film S via the insulating film 31, and the first and second strip electrode films A are provided. , B are surrounded by a peripheral portion of the shield electrode film S located thereunder in an annular shape from substantially the surface direction.
In the electrode system 20 shown in FIG. 5B, the second strip electrode films B and B are arranged in parallel and in close proximity to both widths of the first strip electrode film A, respectively.
In the electrode system 20 shown in (c) of the same figure, the first strip electrode films A and A are arranged close to each other in parallel to both widths of the second strip electrode film B, respectively.

=== Fifth to Seventh Embodiments of Proximity Sensor Electrode System ===
FIG. 5 shows fifth to seventh embodiments of the electrode system of the electrostatic proximity sensor according to the present invention.
In the electrode system 20 shown in FIG. 6A, the high-resistance conductive coating 26 is annular along the peripheral edge of the shield electrode film S that surrounds the outer edges of the first and second strip electrode films A and B from the surface direction. Is provided. The upper surface of the conductive coating 26 is exposed and is connected to the shield electrode film S. The conductive coating 26 is effective in further reliably separating the first and second strip electrode films A and B and the mounted body when a resistive conductive film is formed by rainwater or the like.
In the electrode system 20 shown in FIG. 6B, a part of the width of the periphery of the shield electrode film S that surrounds the outer edges of the first and second strip electrode films A and B from the surface direction is exposed.
In the electrode system 20 shown in FIG. 5C, the entire width of the periphery of the shield electrode film S that surrounds the outer edges of the first and second strip electrode films A and B from the surface direction is exposed.

  As described above, the removal of the dielectric layer on the protruding portion of the shield electrode film S or the reduction of the thickness of the shield electrode film S is an alternating current between the first and second strip electrode films A and B and the mounted body. This is effective in further ensuring the target separation, whereby the width of the protruding portion (creeping distance d) can be reduced.

=== Eighth Embodiment of Proximity Sensor Electrode System ===
FIG. 6 shows an eighth embodiment of the electrode system of the electrostatic proximity sensor according to the present invention by a sectional view exaggerating the thickness.
In the electrode system 20 shown in the figure, the second strip electrode film B is disposed on the first strip electrode film A via the insulating film 31. In this case, of the area of the first strip electrode film A, the area of the portion where the second strip electrode film B overlaps is an invalid area that does not function as a sensor electrode. Therefore, the width of the first strip electrode film A is formed so that at least the width of the portion where the second strip electrode film B overlaps is larger than the width of the second strip electrode film B.

  In this embodiment, the effective width of the first strip electrode film A is reduced by the width of the second strip electrode film B, but the effective width of the first strip electrode film A reduced by the width is the second strip shape. If it is larger than the width of the electrode film B, it can operate as the electrostatic proximity sensor electrode system of the present invention.

=== Other Embodiments of Proximity Sensor Circuit System ===
FIG. 7 shows a second embodiment of the electrostatic proximity sensor circuit system according to the present invention.
Description will be made by paying attention to the difference from the first embodiment shown in FIG. 2. In the second embodiment shown in FIG. 2, the connection terminal SIA of the first strip electrode film A and the connection terminal SIB of the second strip electrode film B are used. The voltage application to the connection terminal SIS of the shield electrode film S is switched between the two potentials Vs1, Vs2 (Vs1> Vs2) by the switching circuits Scb-Stb, Sca-Sta, Scr-Ssr that operate in synchronization with each other. .
Further, in the circuit system of the embodiment shown in the figure, the output Vd of the differential circuit formed by the operational amplifier 53 is sampled by the switching circuit Ssh and output to the subsequent circuit (not shown).

FIG. 8 shows a third embodiment of the electrostatic proximity sensor circuit system according to the present invention.
When focusing attention on the difference from the second embodiment shown in FIG. 7, in the third embodiment shown in FIG. 7, the capacitance Ca and the second strip electrode film B formed by the first strip electrode film A are the same. A capacitive element Cc for reducing and correcting the difference (Ca−Cb) from the capacitance Cb to be formed is provided.

  The correcting capacitive element Cc is added in parallel to the electrostatic capacitance Cb of the second strip electrode film B via the switching circuits Ssb and Ssc, so that the electrostatic capacitance Cb of the second strip electrode film B and the first strip The difference (Ca−Cb) from the capacitance Ca formed by the electrode film A can be reduced. Thereby, it is possible to easily detect the approach of the detection object based on the capacity difference (Ca−Cb).

  In the circuit system of the embodiment shown in the figure, as shown in the figure, a timing chart of on / off of each switching circuit Ssc, Ssb, Ssa, Sss, Sa, Sb and voltages Vd, Ssh, Vo at the main parts is shown. A predetermined voltage Vr and GND (Vr> GND) are periodically and alternately applied to the electrode films A, B, and S, so that Ca, Cb, and Cc are charged and discharged, and the shield electrode film S is Active shield driving is performed so as to have the same potential as that of the first and second electrode films A and B.

=== Ninth and Tenth Embodiments of Proximity Sensor Electrode System ===
FIG. 9 shows a ninth embodiment of an electrode system for an electrostatic proximity sensor according to the present invention by a plan view and a sectional view. As shown in the figure, when the second strip electrode film B is disposed on the first strip electrode film A, the cider electrode film S is disposed on the film-like insulating base 30, and each electrode film S, An insulating film is disposed between A and B and on the uppermost electrode film A. Although it is theoretically desirable that the first strip electrode film A and the second strip electrode film B are disposed so as to be completely overlapped in the longitudinal direction, a slight offset may occur as shown in FIG.

  FIG. 10 is a plan view showing a tenth embodiment of an electrode system for an electrostatic proximity sensor according to the present invention. As shown in the figure, when the second strip electrode film B is disposed on the first strip electrode film A, the portion of the first strip electrode film A that overlaps the second strip electrode film B is the sensor electrode. Invalid area that does not work. Therefore, as shown in the figure, while the pattern of the second strip electrode film B is deformed, the sensor can be provided with a dead band or the sensitivity range of the sensor can be controlled by the deformation pattern.

DESCRIPTION OF SYMBOLS 10 Automobile 11 Bumper 20 Electrostatic proximity sensor electrode system A 1st strip electrode film B 2nd strip electrode film S Shield electrode film 24 Annular shield electrode film 25 Via 26 High resistance conductive coating 30 Insulation base 31 Insulation film 51 Operational amplifier constituting the first charge-voltage conversion circuit 52 Operational amplifier constituting the second charge-voltage conversion circuit 53 Operational amplifier constituting the differential circuit 54 Active low-pass filter (LPF)
d Creepage distance (extrusion width)
SIA connection terminal of the first strip electrode film A SIB connection terminal of the second strip electrode film B SIS connection terminal of the shield electrode film S Ca capacitance formed on the first strip electrode film A Cb on the second strip electrode film B Capacitance formed Cfa, Cfb Negative feedback capacitance element Sa, Sb Discharge reset switching circuit Vs1 First potential Vs2 Second potential Sas Switching circuit for switching between first potential Vs1 and second potential Vs2 Vo Output voltage

Claims (9)

An insulating base that is a dielectric;
A shield electrode film disposed on the upper surface of the insulating base;
A first insulating film that is a dielectric covering the upper surface of the shield electrode film;
First and second strip electrode films disposed on the upper surface of the first insulating film;
A second insulating film that is a dielectric covering the upper surfaces of the first and second strip electrode films,
The first strip electrode film and the second strip electrode film are substantially the same in length and are arranged close to each other in parallel,
The width of the first strip electrode film is larger than the width of the second strip electrode film,
The shield electrode film extends and extends so as to surround the periphery of the portion where the first and second strip electrode films are disposed.   2. The annular shield electrode film is provided on the same plane so as to surround the first and second strip electrode films from the surface direction, and the annular shield electrode film is formed on the same layer surface with respect to the first and second strip electrode films. And the conductive film is conductively connected to the shield electrode film located on the lower side thereof, and the upper side surface thereof is covered with an insulating film as a dielectric together with the first and second strip electrode films. Electrostatic proximity sensor electrode system.   3. The electrode system for an electrostatic proximity sensor according to claim 1, wherein a second strip electrode film is disposed in parallel and close to both widths of the first strip electrode film.   3. The electrode system for an electrostatic proximity sensor according to claim 1, wherein the first strip electrode film is disposed in parallel and close to both widths of the second strip electrode film.   5. The electrostatic method according to claim 1, wherein a high-resistance conductive coating is provided in an annular shape along a peripheral edge portion of the shield electrode film that surrounds the outer edges of the first and second strip electrode films from the surface direction. Proximity sensor electrode system.   5. The electrode of an electrostatic proximity sensor according to claim 1, wherein a part or all of the width of the peripheral edge of the shield electrode film surrounding the outer edges of the first and second strip electrode films from the surface direction is exposed. system.   7. The electrode system for an electrostatic proximity sensor according to claim 1, wherein a second strip electrode film is disposed on the first strip electrode film via an insulating film. An electrostatic proximity sensor comprising an electrode system and a circuit system,
The electrode system includes an insulating base that is a dielectric, a shield electrode film disposed on an upper surface of the insulating base, a first insulating film that is a dielectric covering the upper surface of the shield electrode film, and an upper surface of the first insulating film. The first and second strip electrode films, and a second insulating film that is a dielectric covering the top surfaces of the first and second strip electrode films,
The first strip electrode film and the second strip electrode film are substantially the same in length and are juxtaposed in parallel,
The width of the first strip electrode film is larger than the width of the second strip electrode film,
The shield electrode film extends so as to surround the periphery of the portion where the first and second strip electrode films are disposed,
The circuit system includes a voltage application unit and a difference detection unit,
The voltage application means applies a substantially equal voltage to each of the first strip electrode film, the second strip electrode film, and the shield electrode film, and repeatedly changes the applied voltage,
The difference detecting means outputs a voltage signal corresponding to the difference between the accumulated charge amount of the first strip electrode film and the accumulated charge amount of the second strip electrode film. 9. The difference detecting means according to claim 8, wherein the difference detecting means converts the accumulated charge amount of the first strip electrode film into a voltage, and the second charge voltage converts the accumulated charge amount of the second strip electrode film into a voltage. A conversion circuit, and a differential circuit for extracting a difference between the output voltages of the first and second charge-voltage conversion circuits. The first and second charge-voltage conversion circuits are each configured using an operational amplifier,
In each operational amplifier, a negative feedback capacitive element and a discharge reset switching circuit are connected between the output and the inverting input, and a first potential and a second potential having different potentials are periodically switched and applied to the non-inverting input. The electrostatic electrostatic proximity sensor, wherein the first potential and the second potential applied by switching to the non-inverting input are also applied to the shield electrode film.