JP2007298452A - Electric potential measuring apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric potential measuring apparatus capable of a performance improvement and a comparatively long time stable operation, with hardly attracting a magnetic fine particle by an electromagnetic driving means which is used in the apparatus. <P>SOLUTION: The electric potential measuring apparatus 100 comprises a substrate 105 having a film 104, the detection electrodes 111, 112 mounted on the film 104, the electromagnetic driving means 102, 124 for a deformation of the film 104, a signal detection means 120 which is connected with the detection electrodes 111, 112. The electromagnetic driving means includes at least one electromagnetic coil 124. The detection electrodes 111, 112 mounted on the film 104 are arranged oppositely to an object to be measured, then when the film 104 is deformed by the electromagnetic driving means, the electric potential of the object to be measured is measured by detecting the appeared signals at the detection electrodes 111, 112, using a signal detection means 120. The electromagnetic driving means 102, 124 are arranged so as not to expose to the object to be measured. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a potential measuring device that can measure the potential of an object to be measured (potential measurement target) in a non-contact manner, an image forming apparatus having the potential measuring device, and the like.

In an image forming apparatus having a photosensitive drum and performing image formation by electrophotography, in order to obtain a stable image quality at all times, the potential distribution on the surface of the photosensitive drum is appropriately (typically uniform) in any environment. ) So that the surface of the photosensitive drum is charged. For this reason, the image forming apparatus is conventionally equipped with a function for measuring the potential of the photosensitive drum surface with a potential measuring device and performing feedback control so as to keep the potential of the photosensitive drum surface uniform using the result. Often done.

As a potential measuring device used in an image forming apparatus, an apparatus having the following structure has been proposed (see Patent Document 1). FIG. 5 is a top view showing the structure of the potential measuring device 500. FIG. In this potential measuring device 500, an oscillating body 504 and two torsion springs 502 and 503 are formed integrally with the support substrate 501, and the oscillating body 504 has two detection electrodes 511 and 512. The shape of the oscillating body 504 is axisymmetric with respect to the center line A-A ′ connecting the center lines in the major axis direction of the torsion springs 502 and 503. The detection electrodes 511 and 512 are arranged symmetrically with respect to the center line A-A ′. The detection electrodes 511 and 512 are connected to extraction electrodes 515 and 516 installed on the support substrate 501 by electrode wirings 513 and 514, respectively. The extraction electrodes 515 and 516 are connected to the differential amplifier 520 by wirings 517 and 518, respectively.

An example of the potential measuring method of the potential measuring apparatus 500 will be described with reference to FIG. 5 (b) which is a cross-sectional view taken along the line BB ′ of FIG. 5 (a). Here, the potential measuring device 500 is installed facing the measurement target surface 521. The measurement target surface 521 is, for example, a photosensitive drum. The potential measuring device 500 is disposed in an electrically conductive case 522 that is electrically grounded. FIG. 5 (b) also shows a state in which the rocking body 504 is rocked by a rocking body drive mechanism (not shown) in broken lines. By periodically oscillating the oscillator 504, the distance and capacitance between the detection electrodes 511 and 512 and the measurement target surface 521 are periodically changed, and a signal current including potential information on the measurement target surface 521 is differentially changed. It can be taken out from the amplifier 520.
JP 2004-301555 A

However, in the electric potential measuring apparatus as described above, the space where the oscillator driving mechanism exists communicates with the space where the measurement object exists through the opening of the case, so that magnetic fine particles such as toner used for printing can be used. There is a concern that the magnetic field generating means of the oscillator driving mechanism will be attracted. Therefore, the stability of the operation of the oscillator driving mechanism may be impaired, and as a result, the stability of the potential measurement operation may be hindered. As the magnetic field generating means, there are a permanent magnet and an electromagnetic coil. The former always has a concern of attracting magnetic particles, and the latter has a concern of attracting magnetic particles during operation.

In view of the above problems, the potential measuring device of the present invention includes a substrate having a film, a detection electrode installed on the film, electromagnetic driving means for deforming the film, and a signal connected to the detection electrode. Detecting means. In the present invention, the electromagnetic driving means includes a first magnetic field generating portion installed on the surface of the film on which the detection electrode is not installed, and a first surface installed at a position facing the surface of the film. Includes two magnetic field generating parts. At least one of the first magnetic field generating portion and the second magnetic field generating portion is an electromagnetic coil.

In addition, in view of the above problems, a method for manufacturing a potential measuring device according to the present invention includes a step of preparing a substrate having a film, a step of forming an opening in the substrate, and a detection electrode on the film in a portion where the opening is formed. And a step of forming an electromagnetic coil or a magnetic body on the surface of the film having no detection electrode.

In view of the above problems, an image forming apparatus of the present invention includes the above-described potential measuring device, a signal processing device that processes an output signal obtained from the potential measuring device, and an image forming unit. Here, the portion where the detection electrode of the potential measuring device is formed is arranged to face the potential measurement target of the image forming means, and the image forming means uses the signal processing result of the signal processing device to perform image formation. Take control.

According to the electric potential measuring apparatus of the present invention, since the film is deformed using the electromagnetic driving means and the output signal appearing on the detection electrode on the film is detected, the electromagnetic driving is performed using the film. A structure in which the means is not substantially exposed to the potential measurement object can be easily realized. For this reason, the electromagnetic driving means is difficult to attract magnetic fine particles such as toner, which is a magnetic substance, and the performance of the potential measuring device can be improved and stable operation can be performed for a relatively long time.

Such a potential measuring device can be manufactured relatively easily and with high accuracy using a semiconductor process or the like by the above-described manufacturing method of preparing a substrate having a film. Furthermore, by using the potential measuring device in an image forming apparatus, it is possible to improve the performance of the image forming apparatus and to perform a stable operation for a relatively long time.

Hereinafter, embodiments of the present invention will be described. One embodiment of a potential measuring device includes a substrate having a film disposed opposite to a measurement target, at least one detection electrode disposed on the film, an electromagnetic coil for deforming the film, and the like. Electromagnetic drive means and signal detection means connected to the detection electrodes. The electromagnetic driving means includes a first magnetic field generating part installed on the surface of the film on which the detection electrode is not installed, and a second magnetic field generating installed at a position facing the film surface. Including parts. Here, the first magnetic field generating portion and the second magnetic field generating portion that exert attraction or repulsive force are respectively a permanent magnet and an electromagnetic coil, or vice versa, or a soft magnetic material and an electromagnetic coil, or vice versa, or electromagnetic. A coil and an electromagnetic coil. Then, when the detection electrode is disposed opposite to the potential measurement object and the film is deformed by the electromagnetic driving means in a secondary bending mode or a basic mode, which will be described later, a signal that appears on the detection electrode is the signal. The potential of the potential measurement object is measured by detection by the detection means. The signal detection means can include an amplification means, a current / voltage conversion means, and the like.

The film is stretched over the substrate through the film so that there is no spatial path from the potential measurement object to the electromagnetic driving means. That is, the film does not have openings such as holes. Thus, since the film does not have an opening where an end surface appears, the entire periphery of the film is supported by the substrate, and the detection electrode and the electromagnetic driving unit are spatially separated. Therefore, magnetic fine particles such as toner that may be present on the detection electrode side are less likely to be attracted to the electromagnetic driving means, and the performance of the potential measuring device can be improved and stable operation can be performed for a long time.

When a configuration using a permanent magnet in the electromagnetic driving means is provided, an electric potential measuring device capable of driving the deformation of the film with high energy efficiency can be provided. A soft magnetic material (iron, nickel, cobalt, permalloy (registered trademark), etc.) can be used instead of the permanent magnet. In this case, various film forming means such as vapor deposition, sputtering, plating, etc. can be used, making it easy to make and increasing the degree of design freedom.

One detection electrode is installed on the film with a rocking center axis in between, and the film is deformed so that a pair of detection electrodes are swung around the rocking center axis by the electromagnetic driving means. It is also possible to adopt a configuration to make it. In this case, signal currents having opposite phases can be generated from the respective detection electrodes, and the signal detection unit performs differential detection of signals using a difference between two signals output from the pair of detection electrodes. Can be configured. According to this configuration, it is possible to reduce noise at the deformation driving frequency of the film.

The film is made of an organic material, for example. When the film is made of an organic material, the film can have a small Young's modulus and can be easily deformed. Furthermore, the film can be formed of polyimide or polydimethylsiloxane (PDMS). Thereby, a film can be easily produced, and a relatively inexpensive potential measuring device can be provided.

The substrate is made of, for example, silicon. Since the substrate is made of silicon, an opening can be formed in the substrate with high accuracy by wet etching with a strong alkaline solution or dry etching with a fluorine-based gas.

The potential measuring apparatus as described above can be manufactured using a semiconductor process or the like. When a semiconductor process is used, high-precision processing is possible, and the film and the detection electrode can be formed with high precision.

Hereinafter, more specific embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
A potential measuring apparatus 100 according to the first embodiment of the present invention will be described with reference to FIG. FIG. 1 (a) is a top view, and FIG. 1 (b) is a cross-sectional view along AA ′ in FIG. 1 (a). As shown in FIG. 1, the potential measuring apparatus 100 has a structure in which a chip part 131 and an electromagnetic coil part 132 manufactured by MEMS technology using a semiconductor process or the like are installed in a jig 122. These sizes are, for example, about 5 mm in length, 5 mm in width, and about 3 mm in height.

The chip part 131 will be described with reference to FIGS. 1 (a) and 1 (b). Here, the chip portion 131 is formed so that the film 104 is supported on the upper surface of the support substrate 105. Here, the film 104 has a thickness t1 = 10 μm and a diameter d1 = 4 mm (the diameter of the opening 126 below) so that the film 104 can be deformed so as to swing around the central axis. The film 104 is made of an organic film such as polyimide or polydimethylsiloxane, and the material itself is ductile, so that it can be greatly deformed. The support substrate 105 has a circular opening 126 in the center thereof. The support substrate 105 is made of silicon, and silicon dioxide 106 is formed on the front and back surfaces to be electrically insulated. The thickness of the substrate 105 was t2 = 0.5 mm.

On the surface of the film 104, two detection electrodes 111 and 112 are provided symmetrically with respect to an axis B-B 'passing through the center of the opening 126. The sizes of the detection electrodes 111 and 112 are, for example, a = 1.4 mm and b = 0.7 mm. On the back surface at the center of the film 104, a permanent magnet 102, which is a rod-like magnetic body, is disposed along the axis A-A '. The magnetization direction of the permanent magnet 102 is a direction connecting the N pole and the S pole shown in FIG. 1B with the axis B-B ′ in between. In this direction, the positions of the N pole and the S pole may be reversed. The permanent magnet 102 is made of a material magnetized with a hard magnetic material such as samarium cobalt or neodymium iron boron. Although one permanent magnet 102 is shown here, a plurality of permanent magnets magnetized in the same direction can be installed in parallel. The detection electrodes 111 and 112 are connected to extraction electrodes 115 and 116 installed on the support substrate 105 by electrode wirings 113 and 114, respectively. The extraction electrodes 115 and 116 are connected to the differential amplifier 120 by wirings 117 and 118, respectively.

Next, the electromagnetic coil unit 132 will be described. The electromagnetic coil unit 132 includes an electromagnetic coil 124 and an electromagnetic coil substrate 123. The electromagnetic coil 124 has a wire (not shown) wound in a circular shape along the XY plane (a plane perpendicular to the z-axis and perpendicular to the paper surface). Therefore, the N pole or the S pole appears on the upper surface of the electromagnetic coil 124. The wiring of the electromagnetic coil 124 is made of a low resistance metal such as copper or aluminum, and the number of turns is from several tens to several hundreds. The electromagnetic coil 124 has a diameter d2 = 3 mm and a height t3 = 2 mm. The electromagnetic coil substrate 123 is made of a ferromagnetic material such as iron or Permalloy (registered trademark), and has a role of supporting the electromagnetic coil 124 and its strength by concentrating the magnetic field generated from the electromagnetic coil 124 at a necessary location. And has a role to increase.

The entire potential measuring apparatus 100 will be described. The chip part 131 and the electromagnetic coil part 132 are bonded to a metal jig 122 as shown in FIG. The center of the opening 126 and the center of the electromagnetic coil 124 are aligned so as to substantially coincide on the XY plane. The jig 122 is electrically grounded. Here, the permanent magnet 102 is structured not to be exposed by the film 104 and the jig 122. That is, in the space where the permanent magnet 102 is installed, the potential measurement target side is sealed with the membrane 104, and the side opposite to the potential measurement target and the four side surfaces are sealed with the jig 122. Therefore, the permanent magnet 102 has a structure that is difficult to attract magnetic fine particles such as toner used in printers and copiers. However, in a range where there is no hindrance to sealing, a minute penetration is made in a part of the wall (a part other than the film 104 of the potential measuring device) that seals the permanent magnet 102 so that the deformation operation of the film 104 is performed more smoothly. A hole may be opened. For example, a minute through hole can be formed in the jig 122 to form an air inlet / outlet port between a space such as the permanent magnet 102 and the outside thereof. Furthermore, instead of providing such a through-hole, or in combination with the through-hole, a part of the wall surface is made of a deformable material such as resin, so that the deformation operation of the film 104 can be performed more smoothly. it can.

The potential measuring operation of the potential measuring apparatus 100 of the present embodiment will be described with reference to FIG. 1 (a), FIG. 1 (b), and FIG. 2 which is a cross-sectional view taken along the line A-A 'of FIG. In FIG. 2, the potential measuring device 100 is installed facing the surface of the measuring object 121. The measurement target 121 is, for example, a photosensitive drum used for a printer or a copying machine. Here, first, the potential that can be detected by one detection electrode 111 will be described.

The potential measuring apparatus 100 of the present embodiment is a so-called mechanical AC electric field induction type. In this method, the potential of the surface of the measurement target 121 is a function of the magnitude of the current extracted from the detection electrode 111, and is given by the following equation.
i = dQ / dt = d [CV] / dt (1)
Here, Q is the amount of charge appearing on the detection electrode 111, C is the electrostatic coupling capacitance between the detection electrode 111 and the surface of the measurement target 121, and V is the potential of the surface of the measurement target 121. The capacity C is given by the following equation.
C = AS / x (2)
Here, A is a proportional constant related to the dielectric constant of the substance between the surface of the detection electrode 111 and the measurement target 121, S is the area of the detection electrode 111, and x is the distance between the surface of the detection electrode 111 and the measurement target 121. is there.

Using these relationships, the potential V of the surface of the measuring object 121 is measured. To accurately measure the amount of charge Q appearing on the detecting electrode 111, the sensing electrode 111 and the surface of the measuring object 121 are It is necessary to periodically modulate the size of the capacitance C between them. Here, the capacitance C is periodically changed by periodically changing the distance x between the detection electrode 111 and the surface of the measurement object 121. For example, the detection electrode 111 is arranged at the center of the circular film 104, and the film 104 is deformed to periodically change the distance x between the surface of the measurement target 121 and the detection electrode 111, thereby modulating the capacitance C. Suppose you do.

Here, if the rate of change of the surface potential V of the measurement object 121 is sufficiently slow with respect to the rate of change of the capacitance C, V can be regarded as being constant in the minute time dt, so that the equation (1) Is represented by the following equation.
i (t) = dQ (t) / dt = V · dC (t) / dt (3)

From the equation (3), the magnitude of the alternating current signal i generated at the sensing electrode 111 is a linear function of the surface potential V of the measuring object 121. Therefore, by measuring the amplitude of the alternating current signal, The surface potential V can be obtained. However, the surface potential of the measurement object can also be measured by a method using a feedback processing circuit unit or the like. In this method, a voltage is applied to an appropriate member (for example, a shield case 522 as shown in FIG. 5), and the voltage output signal by the AC current signal is adjusted to be zero, and the applied voltage at that time is adjusted. This is the potential to be measured.

Next, a deformation driving method for the film 104 will be described. When a current is passed from the current source 125 to the electromagnetic coil 124, magnetic poles corresponding to the direction of the current flowing through the electromagnetic coil 124 are generated on the upper and lower surfaces of the electromagnetic coil 124. In FIG. 2, the upper surface is an N pole and the lower surface is an S pole. The generated magnetic field H is proportional to the product of the current I flowing through the electromagnetic coil 124 and the number N of turns of the electromagnetic coil 124. The magnetic field H acts on each magnetic pole of the permanent magnet 102 to exert an attractive force and a repulsive force on each magnetic pole, and the film 104 is deformed around the axis B-B '. The generated torque T is expressed as the product of the magnetization m of the permanent magnet 102 and the magnetic field H. Therefore, it can be seen that the generated torque T is proportional to the current I flowing through the electromagnetic coil 124. The permanent magnet 102 can be replaced with a soft magnetic material. However, in this case, since the force generated between the soft magnetic material and the electromagnetic coil 124 is only the attractive force, it is necessary to arrange the film 104 in consideration of the deformation state of the film 104. For example, the soft magnetic material can be disposed only on the left or right side of the axis B-B ′ in FIG. Further, in the case where the soft magnetic body is provided on both the left and right sides with respect to the axis BB ′ in FIG. 1, the soft magnetic body and the soft magnetic body driving means so that each soft magnetic body can be driven independently. It is necessary to determine the number and arrangement of electromagnetic coils.

FIG. 2 shows a state in which the film 104 is deformed by the method described above. The distance and capacitance between the detection electrodes 111 and 112 and the surface of the measurement target 121 are periodically changed by periodically deforming the film 104, and the signal current including the potential of the surface of the measurement target 121 is detected by the detection electrode 111, 112 can be generated. Here, the signal current generated by the detection electrode 111 and the detection electrode 112 is a signal including the surface potential of the surface of the measurement target 121 and having a phase difference of 180 degrees. Therefore, by processing the two signals using the differential amplifier 120, the output signal can be doubled and noise that affects the detection electrode 111 and the detection electrode 112 can be removed.

Here, the membrane 104 can be continuously deformed by passing alternating current through the electromagnetic coil 124 using the current source 125. Further, by driving at the resonance frequency of the film 104, the deformation amount of the film 104 can be increased. That is, the change in the coupling capacitance increases, and the amplitude of the signal current including the potential of the surface of the measurement target 121 can be increased. The resonance frequency is about 40 kHz, for example. Here, as shown in FIG. 2, the case where the film 104 is deformed in the secondary bending mode is shown, but other deformation modes may be used. In this case, however, it is necessary to optimize the number and arrangement of the detection electrodes 111 and 112. For example, it is possible to adopt a basic mode in which the entire central portion of the film 104 is simply moved closer to or away from the measurement target 121. In this case, one detection electrode may be arranged at the center of the film 104 (this is a structure premised on the description of the potential measurement operation that can be detected by the one detection electrode 111).

Next, a manufacturing process of the chip portion 131 will be described with reference to FIG. 3 showing an A-A ′ cross section in FIG. However, the dimensions are exaggerated for easy understanding of the process.

(1) First, about 1 μm of silicon dioxide 106 is formed on both surfaces of a support substrate 105 (thickness: about 500 μm) made of single crystal silicon using a thermal oxidation furnace or the like. The back surface is patterned using wet etching with hydrofluoric acid or the like, or reactive ion etching with a fluorine-based gas. (Figure 3 (a))

(2) A polyimide film is formed on the surface silicon dioxide 106 to a thickness of about 10 μm to form a film 104. As a film forming method, spin coating or pasting is used. The thickness of the membrane 104 is an important factor that determines the resonance frequency of the membrane 104. (Figure 3 (b))

(3) After forming about 50 mm of titanium on the surface film 104 as a detection electrode, about 1000 mm of gold is deposited by vapor deposition, sputtering, or the like. Next, patterning is performed using wet etching using an iodine solution, reactive ion etching, or ion milling to form detection electrodes 111 and 112. (Figure 3 (c))

(4) A novolac resist (not shown) is applied to the back surface of the support substrate 105 to a thickness of about 8 μm, and photolithography is performed to form a dry etching mask. Next, RIE using an inductively coupled plasma and a BOSCH process is performed on the support substrate 105 which is silicon to expose the silicon dioxide 106 on the surface functioning as an etching stopper, thereby forming an opening 126. Thereafter, the resist is removed. (Fig. 3 (d))

Here, the BOSCH process is a method of selectively etching silicon with good anisotropy by alternately supplying an etching gas and a side wall protection gas and switching between etching and side wall protection. By using this type of RIE, an opening 126 having a vertical sidewall can be formed. Specifically, SF ₆ (sulfur hexafluoride) is used as an etching gas, and C ₄ F ₈ (tetrafluorocarbon ₈ ) is used as a side wall protecting gas. Then, RF power: 1800W, bias power: 30 W, gas flow rate: SF ₆ = 300sccm (Standard
Cubic Centimeter) and C ₄ F ₈ = 150 sccm. Etching is preferably performed under the conditions of SF ₆ / C ₄ F ₈ gas switching time: 7 seconds / 2 seconds, substrate temperature: 10 ° C., etching time: 100 minutes.

(5) A permanent magnet 102 is bonded to a surface of the film 104 opposite to the surface on which the detection electrodes 111 and 112 are bonded by adhering a hard magnetic material rod having a diameter of 0.2 mm and a length of 1.8 mm, and further magnetizing it. To do. Alternatively, the permanent magnet 102 may be formed by a method in which a rare earth magnet powder mixed with a paste adhesive is applied and solidified. (Figure 3 (e)).

According to the configuration of the present embodiment, the space where the permanent magnet 102 and the electromagnetic coil 124, which are magnetic field generators, are not exposed to the surface to be the potential measurement target 121 (that is, this space is substantially outside the space). Sealed). Therefore, it is difficult to attract magnetic fine particles such as toner, and it becomes possible to improve the performance of the potential measuring device and to operate stably for a long time.

(Second embodiment)
A second embodiment of the present invention will be described. The structure of the potential measuring apparatus 200 of this example will be described with reference to FIG. 4 (a) is a top view of the potential measuring device 200, and FIG. 4 (b) is a cross-sectional view along AA ′ in FIG. 4 (a).

In FIG. 4, the potential measuring device 200 includes a tip part 131 and an electromagnetic coil part 132. The basic configuration, driving method, and manufacturing method of the chip portion 131 are the same as those in the first embodiment described above, and a description thereof will be omitted. The present embodiment is characterized in that the electromagnetic coil section 132 is manufactured by the MEMS technology in the same manner as the chip section 131. The electromagnetic coil unit 132 may be manufactured integrally with the chip unit 131, or the electromagnetic coil unit 132 may be manufactured and joined to the chip unit 131 separately.

Here, in the electromagnetic coil section 132, the coil wiring 128 circulates around the opening 126 via the insulator 127. In FIG. 4 (b), the coil wiring 128 only shows four turns for the sake of simplicity, but actually, for example, it wraps around several tens of times. By manufacturing the electromagnetic coil unit 132 using the MEMS technology, the permanent magnet 102 and the electromagnetic coil unit 132 can be disposed close to each other, and the degree of design freedom can be increased. Further, the magnetic flux generated from the electromagnetic coil section 132 can be effectively applied to the permanent magnet 102, and energy efficiency is good. Furthermore, the electromagnetic coil part 132 and the permanent magnet 102 can be positioned precisely, which can lead to energy saving.

Also in this embodiment, the electromagnetic coil substrate 123 plays the same role as that described in the first embodiment, but can be easily made thin here. In FIG. 4 (b), the lower part of the apparatus is open to the outside. However, since this portion is placed at an appropriate installation location, the opening is closed (sealed) with the installation surface of the installation location. Other points are the same as in the first embodiment.

(Third embodiment)
As a third embodiment of the present invention, a configuration example of an image forming apparatus using the potential measuring device of the present invention will be described. An image forming apparatus of this embodiment is shown in FIG. Around the photosensitive drum 21, a charger 16, a potential measuring device 15, an exposure device 18, and a toner supplier 19 that can be controlled by the charger controller 17 are installed.

The mechanism for controlling the charge amount of the photosensitive drum 21 includes a charger controller 17, a charger 16, and the potential measuring device 15 of the present invention. A charger controller 17 is connected to the charger 16, and a potential measuring device 15 of the present invention is connected to the charger controller 17.

The basic operation principle of the image forming apparatus of this embodiment will be described below.
A latent image is obtained by charging the surface of the photosensitive drum 21 with the charger 16 and exposing the surface of the photosensitive drum 21 with the exposure device 18. By attaching toner to the latent image by the toner supplier 19, a toner image in which the latent image is developed is obtained. This toner image is transferred to a printing object 22 sandwiched between a feeding roller 20 serving as a printing object feeding device and a photosensitive drum 21, and the toner on the printing object 22 is fixed. Image formation is achieved through these steps. The charger control device 17 constitutes a signal processing device, and the charger 16, the exposure device 18, the photosensitive drum 21, and the like constitute image forming means.

In the image forming apparatus of this embodiment, the operating principle of the mechanism for controlling the charge amount of the photosensitive drum 21 is as follows. The potential measuring device 15 of the present invention measures the surface potential of the photosensitive drum 21 after charging, and outputs a measurement signal of the surface potential of the photosensitive drum 21 to the charger controller 17. The charger controller 17 receives the measurement signal of the surface potential of the photosensitive drum 21 and feedback-controls the charging voltage of the charger 16 so that the surface potential of the photosensitive drum 21 after charging becomes a desired value. Thereby, stable charging of the photosensitive drum 21 is realized, and stable image formation can be achieved. At this time, the measurement signal of the potential measuring device 15 of the present invention can be used so as to be fed back to the exposure unit 18 and controlled, for example.

In the above configuration, since the permanent magnets (not shown) of the potential measuring device 15 are not exposed to the photosensitive drum 21, the permanent magnets are difficult to attract magnetic fine particles such as toner, which is a magnetic material, and the potential measurement is performed. The performance of the device 15 can be improved and stable operation can be performed for a long time. Accordingly, the performance improvement of the image forming apparatus and stable image formation are realized.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram for explaining a first embodiment of a potential measuring device according to the present invention, where (a) is a top view and (b) is a cross-sectional view along A-A ′ in (a). FIG. 2 is a cross-sectional view taken along the line A-A ′ in FIG. FIG. 5 is a diagram for explaining an example of a manufacturing method of the first embodiment of the potential measuring device of the present invention. FIG. 4 is a diagram for explaining a second embodiment of the potential measuring apparatus of the present invention, where (a) is a top view and (b) is a cross-sectional view taken along line A-A ′ in (a). FIG. 6 is a diagram illustrating a third embodiment of the image forming apparatus of the present invention. It is a figure explaining the background art of this invention.

Explanation of symbols

15, 100, 200: Potential measuring device
17: Signal processing device (charger controller)
21, 121: Measurement target (measurement target surface, photosensitive drum)
102: Electromagnetic drive means (magnetic field generating part, permanent magnet)
104: membrane
105: Board
111, 112: Detection electrode
120: Signal detection means (differential amplifier)
124, 128: Electromagnetic drive means (magnetic field generating part, electromagnetic coil, coil wiring)
126: Opening

Claims (12)

A substrate having a film, a detection electrode installed on the film, an electromagnetic driving means for deforming the film, and a signal detection means connected to the detection electrode,
The electromagnetic driving means includes a first magnetic field generation portion installed on the surface of the film on which the detection electrode is not installed, and a second magnetic field generation installed at a position facing the surface of the film A potential measuring device, wherein at least one of the first magnetic field generating portion and the second magnetic field generating portion is an electromagnetic coil. 2. The potential measuring apparatus according to claim 1, wherein the film is provided on the substrate so that there is no space path from the potential measurement object to the electromagnetic driving unit via the film. The first magnetic field generating portion and the second magnetic field generating portion are a permanent magnet and an electromagnetic coil, or vice versa, or a soft magnetic material and an electromagnetic coil, or vice versa, or an electromagnetic coil and an electromagnetic coil, respectively. 3. The potential measuring device according to claim 1 or 2, characterized in that One detection electrode is installed on the film with a swinging central axis in between, and the electromagnetic driving means is configured to swing the pair of detection electrodes about the swinging central axis. 4. The potential measuring device according to claim 1, wherein the potential measuring device is deformed. 5. The potential measuring apparatus according to claim 4, wherein the signal detection unit performs differential detection of a signal using a difference between two signals output from the pair of detection electrodes. 6. The potential measuring device according to claim 1, wherein the film is made of an organic material. 7. The potential measuring device according to claim 6, wherein the film is made of polyimide or polydimethylsiloxane (PDMS). 8. The potential measuring device according to claim 1, wherein the substrate is made of silicon. 9. The electric potential measuring device according to claim 1, further comprising a through hole in a part of a wall surface that shields the electromagnetic driving means and the outside, other than the membrane. Potential measurement device. 10. The portion of the potential measuring device other than the film, wherein a part of a wall surface that shields the electromagnetic driving means and the outside is a deformable material. The potential measuring apparatus described. A method for producing a potential measuring device according to any one of claims 1 to 10,
Preparing a substrate having the film and forming an opening in the substrate;
Forming a detection electrode on the film in the portion where the opening is formed;
Forming an electromagnetic coil or a magnetic body on the surface of the film on which the detection electrode is not formed;
A method for manufacturing a potential measuring device, comprising: The potential measuring device according to any one of claims 1 to 10, a signal processing device that processes an output signal obtained from the potential measuring device, and an image forming unit,
A portion where the detection electrode of the potential measuring device is formed is disposed opposite to a potential measurement target of the image forming means, and the image forming means controls image formation using the signal processing result of the signal processing device. An image forming apparatus.

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