JP4440065B2 - Potential measuring apparatus and image forming apparatus - Google Patents

Description

The present invention relates to a non-contact type potential measuring device and an image forming apparatus having the potential measuring device.

Conventionally, for example, in an image forming apparatus having a photosensitive drum and forming an image by electrophotography, the potential distribution on the surface of the photosensitive drum is appropriately (typically) in any environment in order to always obtain stable image quality. It is necessary to charge the surface of the photosensitive drum so as to be uniform. For this reason, the potential on the surface of the photosensitive drum is measured using a potential measuring device, and feedback control is performed using the result to keep the potential on the surface of the photosensitive drum uniform.

One of the functions often required for the potential measuring device used for such a purpose has been to contact the surface of the photosensitive drum so that the potential measuring device itself does not change the potential distribution on the surface of the photosensitive drum. The function of measuring the electric potential of a measurement object without mentioning is mentioned. As a method of a potential measuring device having such a function, a method called a mechanical AC electric field induction type has been conventionally used.

The principle of potential measurement using a mechanical AC electric field induction type potential measuring device will be described below. Due to the electric field generated between the surface of the measurement object and the detection electrode built in the potential measuring device, an electric charge Q of an electric quantity proportional to the potential of the surface of the measurement object is induced in the detection electrode. The relationship between Q and V
Q = CV (1)
It is expressed by the formula. Here, C is a capacitance between the detection electrode and the measurement target surface. From equation (1), the electric quantity Q induced in the detection electrode can be measured to obtain the potential of the surface to be measured.

However, since it is difficult to directly and accurately measure the quantity of electricity Q induced in the detection electrode, as a practical method, the capacitance C between the detection electrode and the surface to be measured is set as a practical method. A method of obtaining a potential on the surface of a measurement object by measuring an alternating current signal generated at a detection electrode by periodically changing the current is often used.

It will be shown below that the potential of the surface to be measured can be obtained by the above method. Assuming that the capacitance C is a function of time t, the alternating current signal i generated at the detection electrode is a time differential value of the amount of electricity induced in the detection electrode, and from equation (1)
i = dQ / dt = d (CV) / dt (2)
It is expressed by the formula. Here, when the change rate of the potential V of the surface to be measured is sufficiently slow with respect to the change rate of the capacitance C, V can be regarded as being constant in the minute time dt.
i = V · dC / dt (3)
It is expressed by the formula. From the equation (3), the magnitude of the alternating current signal i generated at the detection electrode is a linear function of the potential V of the surface to be measured, so the potential of the surface of the measuring object can be determined by measuring the amplitude of the alternating current signal. It is possible to obtain.

As a method of periodically changing the capacitance C between the detection electrode and the measurement target surface, (a) a method of periodically changing the effective exposed area of the detection electrode, and (b) the detection electrode and the measurement target. There are three methods: a method of changing the relative permittivity between the surface and (c) a method of changing the distance between the detection electrode and the surface to be measured. The reason is that the capacitance C is approximately
C = A ・ S / x (4)
Because it is expressed by the formula. Here, A is a proportional constant related to the dielectric constant of the substance between the detection electrode and the measurement target surface, S is the area of the detection electrode, and x is the distance between the detection electrode and the measurement target surface.

In the state of the prior art as described above, the potential measuring device is required to be reduced in size and thickness as the diameter of the photosensitive drum in the recent image forming apparatus is reduced and the density around the drum is increased. In a conventional mechanical AC electric field induction type potential measuring device, most of the inside of the potential measuring device is occupied by cantilever beams or assembly parts such as a drive mechanism that vibrates them. Therefore, miniaturization of these drive mechanisms is essential for miniaturization of the potential measuring device.

However, when the drive mechanism is downsized, the amount of change in the area S of the detection electrode or the distance x between the surface to be measured and the detection electrode is reduced. Here, the magnitude of the current extracted as an output signal from the mechanical AC electric field induction type potential measuring device is based on the above-described equations (3) and (4).
i = V ・ d (A ・ S / x) / dt (5)
Therefore, when trying to reduce the size of the drive device, the time differential value in parentheses in equation (5) becomes small. As a result, the current signal i which is an output signal is easily affected by external noise, which is disadvantageous in terms of measurement accuracy. Further, the conventional mechanical AC electric field induction type potential measuring device has a structure in which individual components are assembled, and there remains a problem in miniaturization and cost reduction of the potential measuring device.

Therefore, in recent years, a small potential measuring device based on MEMS (micro electro mechanical mechanism) technology has been proposed (see Patent Document 1). The MEMS technology is a technology for manufacturing a micro mechanical mechanism or an electrical element by applying a semiconductor micromachining technology such as a large-scale integrated circuit. The micro mechanical mechanism or the like is integrated with an electrical element and manufactured in large quantities. Thus, it is possible to greatly reduce the size and cost of the measuring device.
US Pat. No. 6,177,800

One of the advantages of manufacturing a potential measuring device using MEMS technology is that the driving mechanism that is a component of the potential measuring device is miniaturized, a sensing electrode, and a signal generated by the sensing electrode is processed. By integrally forming the signal processing means on the substrate, there is a point that the potential measuring device can be greatly reduced in size and cost. In order to construct an electronic circuit for signal processing on the substrate, a semiconductor whose carrier concentration is intentionally increased is often used as the main material of the substrate.

However, it is known that a semiconductor with a high carrier concentration has a low resistivity. When a low resistivity material is used as the material of the substrate, the substrate, a sensing electrode formed on the substrate via an insulating thin film, Parasitic capacitance that cannot be ignored occurs between the electrical wiring and the like. As a result, a phenomenon occurs in which most of the AC signal generated at a certain detection electrode or electrical wiring flows into another detection electrode or electrical wiring via a parasitic capacitance. Since this phenomenon occurs in the same way between all the detection electrodes and the electrical wiring, for example, an AC signal generated at the detection electrode and a control signal for driving the drive mechanism are mixed, and an accurate potential measurement value is obtained. It will be an obstacle.

The difficulty in transmitting an AC signal having a frequency f between a certain sensing electrode or electrical wiring and another sensing electrode or electrical wiring, that is, the absolute value | Z | of the impedance Z is determined between the certain sensing electrode and the substrate. When the parasitic capacitance is C _h , the parasitic capacitance between another sensing electrode and the substrate is C _h ′, and the resistivity of the substrate is ρ, the following is obtained.

という式で表される（a：比例定数）。（６）式より、各検知電極或いは電気配線間における交流信号の混信を低減させるためには、各検知電極或いは電気配線間のインピーダンスの絶対値｜Ｚ｜を増大させる必要がある。すなわち、検知電極間の部分における基板の抵抗率ρを増大させること及び検知電極と基板との間の寄生容量Ｃ_ｈを減少させることのうち少なくとも一方を行う必要がある。

(A: proportionality constant). From equation (6), it is necessary to increase the absolute value | Z | of the impedance between each detection electrode or electrical wiring in order to reduce the interference of the AC signal between each detection electrode or electrical wiring. That is, it is necessary to perform at least one of reducing the parasitic capacitance C _h between and detection electrode and the substrate can increase the resistivity of the substrate ρ in the portion between the sensing electrodes.

From the above, for example, in order to produce a potential measuring device in which a drive mechanism, a detection electrode, and a signal processing means for processing a signal generated by the detection electrode are integrally formed on a substrate, a semiconductor having a low resistivity as a material of the substrate It is necessary to devise to increase the impedance between the detection electrodes while using a material or the like.

In view of the above-described problems, the potential measuring device of the present invention modulates a plurality of detection electrodes disposed via an insulator on a substrate mainly made of a semiconductor or a conductor, and a coupling capacitance between the measurement target and the detection electrodes. It has a capacitance modulation means and a detection means for detecting the potential of the object to be measured based on the signal detected by the detection electrode, and at least a part of the substrate is solid so as to increase the electrical resistivity between the detection electrodes. An insulator portion is formed, and the portion of the substrate on which the insulator portion is formed is a portion inside the swing plate between a plurality of detection electrodes and a portion below the detection electrodes. It includes a portion that does not extend (see the insulator 115 shown in FIG. 4 and the like) . The capacity modulation means is configured to modulate the distance between the detection electrode provided on the swing plate and the measurement target by swinging the swing plate supported by the torsion spring so as to be swingable with respect to the measurement target. And a configuration in which the exposure area of the detection electrode with respect to the measurement target is modulated by moving a shutter having an opening between the measurement target and the detection electrode on the fixed substrate.

Further, in view of the above problems, the potential measuring method of the present invention uses a plurality of detection electrodes arranged via an insulator on a substrate mainly made of a semiconductor or a conductor, and a coupling capacitance between the measurement target and the detection electrodes. when detecting the potential of the measurement object based on the signals detected by the modulation to the sensing electrode, and further a portion of the substrate, an insulating body so as to increase the electrical impedance between the sensing electrodes It is characterized by that.

In view of the above problems, an image forming apparatus according to the present invention includes the above-described potential measuring device and an image forming unit, and a surface on which a detection electrode of the potential measuring device is formed is a target of potential measurement of the image forming unit. The image forming means controls image formation using the signal detection result of the potential measuring device.

According to the above-described configuration of the present invention, in the potential measuring apparatus or method using the detection electrode supporting substrate mainly made of a semiconductor or a conductor having a relatively low resistivity, an alternating current is generated between the detection electrodes due to the presence of the insulator portion. It is possible to prevent or reduce the phenomenon of signal interference. As a result, it is possible to obtain a relatively accurate potential measurement signal even when a detection electrode supporting substrate whose main material is a semiconductor or conductor having a relatively low resistivity is used.

Before describing the embodiment of the present invention, the principle of the present invention will be described. In the present invention, in a potential measurement device using an oscillator device, a shutter device, or the like as a drive mechanism, the impedance between the detection electrodes is increased to a configuration made mainly of a semiconductor or conductor having a relatively low resistivity. By providing the structure, the problem of alternating current signal interference between the detection electrodes is solved. As a policy for increasing the impedance between the detection electrodes, at least one of reducing the parasitic capacitance between the detection electrode and the low resistivity substrate and increasing the resistivity of the substrate is performed.

Parasitic capacitance C _h between the detection electrode and the substrate, the dielectric constant k _h between the detection electrode and the _substrate, and the detection electrode and the substrate to directly face area between the S _h, detection electrode and the substrate When you place the distance and d _h, approximately
C _h = ε ₀ · k _h · S _h / d _h (7)
(Ε ₀ : dielectric constant of vacuum). (7) from the equation, in order to reduce the parasitic capacitance C _h, (1) reducing the relative dielectric constant k _h of the insulator between the sensing electrode and the oscillating plate, (2) and the sensing electrode and the substrate directly facing reducing the area S _h, (3) increasing the distance d _h between the detection electrode and the substrate, such as it can be seen that it take the means. In the present invention, thereby reducing the parasitic capacitance C _h between the detection electrode and the substrate by using a means (2) or (3).

Further, the resistivity ρ of the substrate is determined by the material for producing the substrate. In the present invention, however, a semiconductor having a relatively high carrier concentration, that is, a material having a relatively low resistivity is used as the material for producing the substrate. As a premise, no means for directly increasing the resistivity of the entire substrate can be taken. However, by devising the structure of the substrate, an AC signal leaks to the substrate through the parasitic capacitance C _h from the sensing electrodes is possible to increase the resistance R to receive in the substrate.

Resistor R AC signal leaks to the substrate is subjected in the substrate, the length of the path through which electrical signals from the portion corresponding to just below the certain detection electrodes in the substrate to the portion corresponding to just below the other one sensing electrode L _s If we put the cross-sectional area of the path as S _s ,
R = ρ · L _s / S _s (8)
It is expressed by the formula. From equation (8), in order to increase the resistance R received in the substrate by the AC signal leaked from each detection electrode to the substrate via the parasitic capacitance, the resistance R is directly changed from a portion of the substrate directly below a certain detection electrode. Assuming that the path through which the electrical signal to the part directly below the detection electrode passes is P, (1) the resistance of path P is locally increased by replacing a certain part of P with an insulator part. (2) path It can be seen that measures such as increasing the length L _s of P and (3) decreasing the cross-sectional area S _s of the path P may be taken. Therefore, the present invention takes these measures.

An embodiment of the potential measuring apparatus of the present invention configured based on the above principle will be described below.
First, the configuration and operation that are the premise of the embodiment of the potential measuring device using the oscillator device of FIGS. 2 to 12 will be described. This operation is essentially the same as these embodiments.

An overhead view of the structure of the potential measuring device using the oscillator device is shown in FIG.
FIG. 1B shows a cross-sectional view at. The oscillating body device 100 is located on the opposite side of the oscillating body of the oscillating body 110, the signal detecting means 120, the driving device 200, the torsion springs 101 and 102 that restrain the oscillating body except for one degree of freedom of rotation. A support member 103 made of a non-insulating material that restricts the degree of freedom of displacement of the end and provides a fixed end is provided. The oscillating body 110 includes an oscillating plate 111 and an insulator film 112 formed on the upper surface thereof. The signal detection unit 120 includes detection electrodes 121 and 122 disposed on the upper surface of the oscillator 110, a signal processing unit 123 that processes a signal generated at the detection electrode, and signal lines 124 and 125 that connect the detection electrode and the signal processing unit. Consists of. The signal processing means 123 can be built in the support member 103 made of a non-insulating material. Here, the oscillator device 100 has a structure that increases the impedance between the detection electrode 121 and the detection electrode 122 (refer to the following examples for specific structural examples). Various driving methods such as magnetic force, electrostatic force, and piezoelectricity can be applied to the driving device 200. In the following embodiments shown in FIGS. 2 to 12, the driving method using magnetic force using an electromagnetic coil and a permanent magnet is taken as an example. Use. That is, a magnetic field that changes periodically by passing an alternating current through the electromagnetic coil 201 is formed, and a torque around the center of the permanent magnet 202 disposed on the surface of the swing plate 111 that faces the electromagnetic coil 201. As a result, the oscillating body 110 is oscillated around the torsion springs 101 and 102 in the rotational direction indicated by the arrow in FIG.

As shown in FIG. 1C, the oscillating body 110 is periodically oscillated using the driving apparatus 200 in a state where the oscillating body apparatus 100 is installed so that the surface of the measurement object 300 and the detection electrodes 121 and 122 face each other. When moved, the distances x1 and x2 between the surface of the measurement object 300 and the detection electrodes 121 and 122 change periodically and in opposite phases to each other. An alternating current signal having an amplitude proportional to the surface potential of 300 is generated. These signals are transmitted to the signal processing unit 123 via the signal lines 124 and 125, and are converted into an AC voltage signal, differential amplification, detection, and rectification by the signal processing unit 123, so that the surface of the measurement object 300 is detected. A DC voltage signal having a magnitude proportional to the potential is obtained.

Example 1 of FIG. 2 will be described. The first embodiment relates to a potential measuring apparatus in which the capacitance between the detection electrode and the swing plate is reduced by forming an insulator portion below each detection electrode. Dashed line AA ′ in FIG.
FIG. 2 shows a cross-sectional view at the same location as FIG. In the oscillating plate 111, the insulating portions 115 and 116 are formed over the entire thickness direction of the oscillating body 111 in contact with the insulator film 112 at portions corresponding to the lower portions of the detecting electrodes 121 and 122. The area where 122 and the surface of the swing plate 111 itself face each other is almost zero. Therefore, the parasitic capacitance generated between them can be significantly reduced from the expression (7) as compared with the case where only the insulator film 112 is interposed. Furthermore, in the present embodiment, the electrical path between the detection electrode 121 and the detection electrode 122 is almost cut off, so that the resistance value of the equation (8) becomes very large. Thus, the impedance of the expression (6) between the detection electrode 121 and the detection electrode 122 can be greatly increased. In this way, the phenomenon of alternating current signal interference between the sensing electrodes 121 and 122 can be prevented or reduced, and a relatively accurate potential measurement signal can be obtained even when the semiconductor or conductor rocking plate 111 having a relatively low resistivity is used. . In this embodiment, since the insulator portions 115 and 116 are formed below the detection electrodes 121 and 122, the insulator film 112 can be omitted if it can be manufactured.

When it is difficult to form the insulator portion over the entire thickness direction of the swing plate as in the first embodiment, the surface on the side where the detection electrodes 121 and 122 of the swing plate 111 are arranged as shown in FIG. Also, the impedance between the detection electrode 121 and the detection electrode 122 can be increased by forming the insulator portions 115 and 116 to a depth less than the thickness of the swing plate. Since the distance that the detection electrode 121 or 122 and the surface of the swing plate 111 are opposed to each other is larger than the thickness of the insulator film 112, the parasitic capacitance generated between them is calculated from the equation (7). This is because it decreases. As the insulator portions 115 and 116 are formed deeper, the impedance between the detection electrode 121 and the detection electrode 122 can be increased. Also in the second embodiment, a phenomenon in which an AC signal interferes between the detection electrodes 121 and 122 can be prevented or reduced, and a relatively accurate potential measurement signal can be obtained. Again, since the insulator portions 115 and 116 are formed below the detection electrodes 121 and 122, the insulator film 112 can be omitted if possible in terms of manufacturing.

Example 3 relates to a potential measuring device in which the resistance value of the swing plate is increased by forming an insulator portion in the portion between the detection electrodes of the swing plate. This top view is shown in FIG. 4A, and a cross-sectional view taken along the broken line B-B ′ is shown in FIG. In the oscillating plate 111, an insulating portion 115 is provided over the entire thickness direction of the oscillating body 111 at a portion between the detection electrode 121 and the detecting electrode 122, and the permanent magnet 202 is interposed through the insulating film 112. (The permanent magnet 202 is also conductive, so it is necessary to cut the electrical path through the permanent magnet 202), so that the electricity from directly below the detection electrode 121 to directly below the detection electrode 122 Since the typical path length is increased by the amount passing through the torsion springs 101 and 102, the resistance value between the position immediately below the detection electrode 121 and the position immediately below the detection electrode 122 is not formed from the equation (8). Compared to the case, it can be increased. As a result, the impedance between the detection electrodes 121 and 122 can be increased, and the phenomenon of alternating current signal interference between the detection electrodes 121 and 122 can be prevented or reduced, and a relatively accurate potential measurement signal can be obtained.

In the third embodiment, when it is difficult to form the insulator portion over the entire thickness direction of the swing plate, the detection electrodes 121 and 122 of the swing plate 111 are arranged as shown in FIG. The detection electrode 121 and the detection electrode can also be formed by forming the insulator 115 from the surface on the side or from the surface on the opposite side to the depth less than the thickness of the swing plate 111 as shown in FIG. The impedance between the two can be increased. Since the width of the low resistance region in this portion is narrowed by forming the insulator portion 115, the resistance value between the position immediately below the detection electrode 121 and the position immediately below the detection electrode 122 in the swing plate 111 from the equation (8). This is because of the increase. When the insulator 115 is formed deeper, the impedance between the detection electrode 121 and the detection electrode 122 can be further increased. Also here, the permanent magnet 202 is provided on the back surface of the swing plate 111 via the insulator film 112.

In Example 5, in the structure of Example 3, as shown in FIG. 6, the thickness of the swing plate 111 is measured from both the surface on the side where the detection electrodes 121 and 122 of the swing plate 111 are arranged and the surface on the opposite side. The insulator portions 115 and 116 are formed to a depth less than this. As a result, the width of the low resistance region in this portion is narrowed, so that the resistance value between the position immediately below the detection electrode 121 and the position immediately below the detection electrode 122 in the swing plate 111 can be increased from the equation (8). it can. This can also increase the impedance between the detection electrode 121 and the detection electrode 122. If the low resistance region between the insulator portions 115 and 116 is formed to be narrower, the impedance between the detection electrode 121 and the detection electrode 122 can be further increased. Also here, the permanent magnet 202 is provided on the back surface of the swing plate 111 via the insulator film 112.

In the sixth embodiment, in the structure of the third embodiment, as shown in FIG. 7, the insulator 115 and the insulator are formed from both the surface on the side where the detection electrodes 121 and 122 of the swing plate 111 are arranged and the surface on the opposite side. The portions 116 and the insulator portions 117 are formed alternately. As a result, the low resistance region in this portion can be narrowed and lengthened, so that the resistance value between the position immediately below the detection electrode 121 and the position immediately below the detection electrode 122 in the swing plate 111 is further increased from the equation (8). Can be increased. When the number of insulator portions formed deeper or alternately is increased, the impedance between the detection electrode 121 and the detection electrode 122 can be further increased. Also here, the permanent magnet 202 is provided on the back surface of the swing plate 111 via the insulator film 112.

In the seventh embodiment, as shown in FIG. 8 or FIG. 9, the insulator 115 and 116 surround each of the detection electrodes 121 and 122 as viewed from the upper surface of the swing plate 111 over the entire thickness direction of the swing plate 111. Is formed. As a result, the electrical path from directly below the detection electrode 121 to directly below the detection electrode 122 can be insulated, so that the impedance between the detection electrode 121 and the detection electrode 122 can be greatly increased. Again, for the reasons described above, the permanent magnet 202 is provided on the back surface of the swinging plate 111 via the insulator film 112.

In the seventh embodiment, when it is difficult to form the insulator portions 115 and 116 over the entire thickness direction of the swing plate 111, as shown in FIG. 10, the insulator portion 115 is the same as in the fourth to sixth embodiments. And 116, or the insulators 115 to 118 may be formed to a depth less than the thickness of the swing plate 111. As a result, the electrical path from directly below the detection electrode 121 to directly below the detection electrode 122 can be narrowed and lengthened. Therefore, the resistance from directly below the detection electrode 121 to directly below the detection electrode 122 from the equation (8). The value can be increased. Again, for the reasons described above, the permanent magnet 202 is provided on the back surface of the swinging plate 111 via the insulator film 112. Thereby, the impedance between the detection electrode 121 and the detection electrode 122 can be increased. As in the fourth embodiment, a sectional view of an example in which the insulator portions 115 and 116 are formed from the side where the detection electrodes 121 and 122 of the swing plate 111 are arranged is shown in FIG. FIG. 10B shows a cross-sectional view of an example in which the insulator portions 115 to 118 are formed from both surfaces of the swing plate 111.

In the ninth embodiment, as shown in FIG. 11A, the insulator 115 is formed across the swing plate 111, the torsion springs 101 and 102, and the support member 103. As a result, the resistance value of the electrical path that reaches the detection electrode 122 from directly below the detection electrode 121 via the torsion springs 101 and 102 and the support member 103 can be increased. Thus, the impedance between the detection electrode 121 and the detection electrode 122 can be increased. In each of the swing plate 111, the torsion springs 101 and 102, and the support member 103, the form of the insulator portion can be selected from any of the forms of the fourth to sixth embodiments. In this embodiment, in each part of the swing plate 111, the torsion springs 101 and 102, and the support member 103, the insulator 115 is formed over the entire thickness direction as shown in FIGS. 11 (b) to 11 (d). As a result, the resistance value of the electrical path that reaches the detection electrode 122 from directly below the detection electrode 121 is significantly increased. Again, for the reasons described above, the permanent magnet 202 is provided on the back surface of the swinging plate 111 via the insulator film 112.

In the tenth embodiment, the means for reducing the parasitic capacitance between the swing plate 111 and the detection electrodes 121 and 122, the swing plate 111, the torsion springs 101 and 102, and the support member 103 from directly below the detection electrode 121. Together with means for increasing the resistance value of the electrical path to the position immediately below the detection electrode 122. Thereby, compared with the case where each means is implemented independently, the impedance between the detection electrodes 121 and 122 can be increased more. In the present embodiment, the insulator portions 115 to 118 are formed inside the swing plate 111 as shown in FIG. 12 by combining the forms of the insulator portions, so that the gap between the detection electrodes 121 and 122 and the swing plate 111 is increased. The reduction of the parasitic capacitance and the increase of the resistance value immediately below the detection electrode 121 to immediately below the detection electrode 122 in the swing plate 111 are realized at the same time.

Although the embodiments so far have been the potential measuring device using the oscillator device, the present invention provides a plurality of detection electrodes provided on a semiconductor or conductor substrate via an insulator, and between the measurement object and the detection electrodes. Any type of potential measuring device can be applied as long as the potential measuring device includes a capacitance modulating means for modulating the coupling capacitance of the sensor and a detecting means for detecting the potential of the measurement object based on the signal detected by the sensing electrode. . In Example 11, a substrate mainly composed of a semiconductor or a conductor in which a plurality of detection electrodes are provided via an insulator is fixed, and a shutter that reciprocally vibrates in parallel with the substrate is used as a capacity modulation unit. Involved in potential measurement equipment.

The potential measuring apparatus according to the present embodiment will be described with reference to FIGS. In FIG. 13, reference numeral 325 denotes a shutter having a line-shaped or strip-shaped opening 326, and the shutter 325 has two detection electrodes 321 arranged in parallel on the substrate 311 with an interval therebetween via an insulating film 312. And 322 on the substrate 311 at intervals. The shutter 325 is reciprocated in the direction of the arrow in FIG. 13 by an electrostatic force generated between the electrodes by applying an AC voltage between the movable electrode integrated with the shutter 325 and the fixed electrode, for example. FIGS. 14A and 14B show how the reciprocal motion modulates the degree of exposure of the detection electrodes 321 and 322 with respect to the measurement object in the opposite phase. Thus, charges are induced in the detection electrodes 321 and 322 in the opposite phase. The processing of signals from the detection electrodes 321 and 322 and the detection of the potential of the measurement object are the same as in the above embodiment.

In this embodiment, the resistance value of the substrate 311 is increased by forming the insulator portion 315 over the entire thickness direction of the substrate 311 in the portion between the detection electrodes 321 and 322 of the substrate 311. The reason why the impedance between the detection electrode 321 and the detection electrode 322 can be increased is almost the same as that described in the ninth embodiment (FIG. 11). Also with respect to the aspect of forming the insulator portion on the substrate of the potential measuring device of the type of this embodiment, the aspects described in the above Examples 1 to 10 can be used alone or in appropriate combination.

FIG. 15 illustrates an image forming apparatus according to the twelfth embodiment. FIG. 15 is a schematic view around the photosensitive drum of the electrophotographic developing apparatus using the potential measuring apparatus according to the present invention. A charger 2102, a potential sensor 2101, an exposure device 2105, and a toner supply device 2106 are installed around the photosensitive drum 2108. A latent image is obtained by charging the surface of the drum 2108 with the charger 2102 and exposing the surface of the photosensitive drum 2108 with the exposure device 2105. Toner is attached to the latent image by a toner supplier 2106 to obtain a toner image. The toner image is transferred to a transfer material 2109 sandwiched between the transfer material feed roller 2107 and the photosensitive drum 2108, and the toner on the transfer material is fixed. Image formation is achieved through these steps.

In this configuration, the charged state of the drum 2108 is measured by the high-performance potential measuring device 2101 of the present invention as described in the above embodiment, the signal is processed by the signal processing device 2103, and fed back to the high voltage generator 2104. By controlling the charger 2102 over time, stable drum charging is realized, and stable image formation is realized.

It is the bird's-eye view (a) of the potential measuring device using the oscillator device, the sectional view (b) at the broken line portion A-A ′, and the sectional view (c) showing the potential measuring method. It is sectional drawing in the same location as the broken-line part A-A 'of Fig.1 (a) about Example 1 of this invention. It is sectional drawing in the same location as the broken-line part A-A 'of Fig.1 (a) about Example 2 of this invention. It is the top view (a) about Example 3 of this invention, and sectional drawing (b) in broken-line part B-B '. It is sectional drawing in the same location as the broken-line part BB 'of Fig.4 (a) about Example 4 of this invention, Comprising: The example (a) which formed the insulator part from the surface where the detection electrode is arrange | positioned, It is a figure which shows the example (b) which formed the insulator part from the surface on the opposite side. It is sectional drawing in the same location as the broken line part B-B 'of Fig.4 (a) about Example 5 of this invention. It is sectional drawing in the same location as the broken-line part B-B 'of Fig.4 (a) about Example 6 of this invention. FIG. 10A is a top view of an example in which the periphery of a detection electrode is surrounded by an insulator portion in Example 7 of the present invention, and FIG. FIG. 10 is a top view (a) of an example in which the periphery of the detection electrode is surrounded by the end of the insulator and the swing plate and a sectional view (b) taken along a broken line D-D ′ in Example 7 of the present invention. It is sectional drawing in the same location as the broken-line part CC 'of Fig.8 (a) about Example 8 of this invention, Comprising: Example (a) which formed the insulator part from the surface where the detection electrode is arrange | positioned, and its It is a figure which shows the example (b) which formed the insulator part from both the surface on the opposite side. Example 9 of the present invention is a top view (a), a sectional view (b) at a broken line portion II ′, a sectional view (c) at a broken line portion II-II ′, and a sectional view at a broken line portion III-III ′ (d) ). It is sectional drawing (b) in the top view (a) and broken-line part E-E 'about Example 10 of this invention. It is a perspective view explaining Example 11 of this invention of the electric potential measuring apparatus using a shutter. It is sectional drawing explaining operation | movement of Example 11 of this invention. It is a figure explaining the image forming apparatus of Example 12 of this invention.

Explanation of symbols

111, 311... Substrate (swing plate)
112, 312, ... Insulator (insulator thin film)
115, 116, 117, 118, 315... Insulator part 121, 122, 321, 322... Sensing electrode 120. 326... Capacity modulation means 300, 2108... Measurement object (photosensitive drum)

Claims (7)

A plurality of sensing electrodes arranged via an insulator on a substrate mainly made of a semiconductor or a conductor, capacitance modulation means for modulating the coupling capacitance between the measurement object and the sensing electrodes, and detected by the sensing electrodes A detecting unit configured to detect a potential of a measurement target based on a signal, and an insulating unit made of a solid is formed on at least a part of the substrate so as to increase an electrical resistivity between the detection electrodes, and the insulating unit The portion of the substrate on which is formed includes a portion inside the substrate between a plurality of detection electrodes and not extending to a portion below the detection electrodes. Of the substrate, both the portion corresponding to the lower portion of the detection electrode and the portion inside the substrate corresponding to a plurality of detection electrodes and not extending to the portion corresponding to the lower portion of the detection electrode The potential measuring device according to claim 1, wherein: The potential measuring apparatus according to claim 1 , wherein the insulator portion is formed over the entire thickness direction of the substrate. The potential measuring device according to claim 1, wherein the insulator portion is formed over a depth less than a thickness of the substrate. A plurality of sensing electrodes arranged on an oscillating plate made of a semiconductor or a conductor as a main material via an insulator, capacitance modulation means for modulating the coupling capacitance between the measurement object and the sensing electrode, and detection by the sensing electrode And a detecting means for detecting the potential of the measurement object based on the received signal, and an insulator portion made of a solid is formed on at least a part of the swing plate so as to increase the electrical resistivity between the detection electrodes. An electric potential measuring device. The portion of the swing plate where the insulator portion is formed includes a portion inside the swing plate that is between a plurality of detection electrodes and a portion that does not extend to a portion that is below the detection electrode. Item 6. The potential measuring device according to Item 5. 7. The electric potential measuring device according to claim 1 and an image forming unit, wherein the surface on which the detection electrode of the electric potential measuring device is formed is arranged to face the surface of the image forming unit that is a potential measurement target. An image forming apparatus, wherein the image forming means controls image formation using a signal detection result of the potential measuring device.

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