JP2011102837A - Image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of an abnormal image such as an image with irregularity and an image of low resolution, caused by a discharge product or the like such as ozone and nitrogen oxide (NOx) accumulated on a surface of a latent image carrier. <P>SOLUTION: The image forming apparatus includes: the latent image carrier; an electrifying means for electrifying the surface of the latent image carrier; an electrostatic latent image-forming means for forming an electrostatic latent image on the surface of the latent image carrier electrified by the electrifying means; a developing means for making the formed electrostatic latent image with toner to be a visible image; a transfer means for transferring, to a body to be transferred, the toner image made to be visible; and a toner cleaning means for cleaning toner remaining on the surface of the latent image carrier after transfer. The image forming apparatus has: an electric resistance detection means for detecting electric resistance of the surface of the latent image carrier; and a means for performing cleaning operation on the surface of the latent image carrier based on the result of detection by the electric resistance detection means. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a device for removing a deteriorated surface protective agent from a latent image carrier used for image formation by an electrostatic image forming process such as a copying machine, a facsimile machine, and a printer, and an image forming apparatus and an image forming method using the same.

In an image forming apparatus using an electrophotographic process, image formation is performed by subjecting a latent image carrier (hereinafter also referred to as an electrophotographic photosensitive member or a photosensitive member) to a charging step, an exposure step, a development step, and a transfer step. Is called. The discharge product generated in the charging process and remaining on the surface of the photoreceptor and the residual toner or toner component remaining on the surface of the photoreceptor after the transfer process are removed through a cleaning process.
The image forming apparatus is configured as a main means such as a facsimile, a printer, and a copying machine. For image formation, a charging device (such as corona charging, contact charging with a roller or a brush, or non-contact charging arranged at a distance of 30 to 250 μm) or an image exposure device (for example, an LD) is formed on the periphery of the photoreceptor. , Exposure means for irradiating a photosensitive member with a dot pattern using an LED array as a light source), developing device (developing means using a one-component or two-component developer magnet brush or flying method), transfer device (corona, roller, belt, etc.) Transfer device), a cleaning device (blade coating brush cleaning, a cleaning device combining the two cleaning members), a static eliminator (a static eliminator using corona discharge, brush, light, etc.) and the like. It is done in a form that works in sequence.

In image formation, charging (charging) is first performed on the photosensitive member by a charging device. As a charging device, a grid is provided, and a metal wire such as a tungsten wire or a nickel wire having a diameter of about 40 to 80 μm stretched in the length direction of the photoconductor in a shield case, or −4000 on a SUS sawtooth electrode plate. A DC voltage of -800 to -2000 V on a corona charging device for charging by applying a DC voltage of about --6500 V, or a charging member such as a roller or brush having a resistance of about 10 ⁵ to 10 ¹² Ω · cm, or A contact charging device that performs charging by applying a DC voltage in which an AC voltage of 1000 to 2500 V / 600 to 2500 Hz is superimposed on a DC voltage of −500 to −2000 V, or a charging member is disposed about 30 to 250 μm away from the photoreceptor. However, non-contact charging devices that charge by applying a DC voltage or a DC voltage superimposed with an AC voltage are used. It is. The surface of the photoreceptor is set to a surface potential necessary for image formation using these charging devices, for example, 400 to 1000 V in absolute value. Note that a function-separated organic photoreceptor formed in the order of a charge generation layer and a charge transport layer that are generally used is negatively charged.

All of the above-described charging devices are charging systems that involve discharge during charging, and therefore, by discharge, ozone (O ₃ ), nitrogen oxide (NOx), and the like are generated as a by-product in addition to charge (hereinafter, generated from the charging device). These materials are referred to as discharge products).
The chemical effect (image flow and electrophotographic characteristic deterioration) of the discharge product generated by the charging device on the photosensitive member is known in the conventional known examples, but the degree of influence varies depending on the charging method. . Looking at the degree of influence of the charging method due to image flow or the like, roughly, the non-contact charging method ≧ the contact charging method ≧ the corona charging method, the order is reverse to the generation amounts of ozone and nitrogen oxides.

In the case of the corona charging method, the charging efficiency (charging level with respect to the input voltage) greatly depends on the shape, size, discharge electrode used, and the like. In the corona charging method with good charging efficiency, ozone is obviously generated more than in the contact charging method, but the influence of chemical and physical hazards can be minimized as in the above order. Therefore, when a corona charging system charging device is used, the durability of the photoreceptor can be greatly extended.
When the corona charging method is used, the clear reason why the hazard to the photoconductor is low is unknown, but since it is away from the photoconductor, the substances that affect the process (halfway) disappear and decrease. This is presumably because the energy given to the photoconductor as a whole is low, the bonding force with the surface of the photoconductor becomes weak, and it is relatively easy to remove with a developer or the like.

In the case of a contact or non-contact charging device, the amount of pollutants generated is small, but the distance to the photoconductor is very close, so the energy is large and the adhesion of the pollutants to the photoconductor surface increases. It is estimated that it will be difficult to remove.
Ozone is known as a strong oxidizing substance, and when it acts on the surface of the photosensitive layer, it oxidizes the surface of the photosensitive member to lower the electrical resistance (lower resistance) and further cuts the molecular structure of the photosensitive layer. This reduces the charging characteristics and sensitivity of the photoreceptor. However, because ozone adheres to an object and decomposes into oxygen molecules and oxygen atoms (which eventually becomes oxygen), the action time as ozone is relatively short, and the continuous effect is less than that of nitrogen oxides. Low.

On the other hand, nitrogen oxides adhere to the surface of the photosensitive layer and penetrate into the photosensitive layer, thereby reducing the electrical resistance of the entire photoconductor, and the influence continues until the nitrogen oxides are removed.
If the discharge product adheres to the surface of the photoconductor and absorbs moisture and is rubbed with a blade or developer, the discharge product is stretched, so there is a range in which the electrical resistance on the surface of the photoconductor decreases (low resistance). It spreads and the resolution decreases, and the image flow area expands to the entire surface.

  Further, when toner components (resin, wax, colorant, etc.) or paper dust (binder resin, talc, etc.) are attached, a filming phenomenon occurs on the surface of the photoreceptor, and resolution and image flow are more likely to occur. In addition, background contamination and density unevenness are caused, and further, the wear of the photosensitive layer is promoted. Resin adhesion increases the resistance, the charging potential abnormally rises, and normal image formation may not be performed.

  Even if discharge products such as ozone and nitrogen oxides adhere, they do not penetrate immediately into the interior, but they gradually penetrate into the interior through repeated use, so the discharge products attached to the surface should be eliminated early. With the right treatment, damage can be kept to a minimum. However, since the discharge product is strongly adsorbed on the surface of the photosensitive member and cannot be scraped off by a normal cleaning process, it is not easy to remove only the discharge product.

  As a result of deterioration of the polymer constituting the photoconductor due to the discharge for charging, the reduction in the film thickness of the photoconductor is facilitated, and toner components and the like are likely to adhere to the photoconductor, resulting in a long life of the photoconductor. A problem arises. To prevent such a problem, there is a method of supplying a protective agent to the surface of the photoconductor at least in the discharge region in order to prevent the photoconductor from being deteriorated due to the discharge. By supplying the protective agent, it is possible to prevent the photoreceptor from being deteriorated.

  However, when a protective agent is supplied, the protective agent will be discharged in the discharge region. When the protective agent is discharged, the protective agent itself deteriorates. Therefore, when the protective agent is accumulated on the surface of the photoreceptor, an abnormal image is formed. When the protective agent is deteriorated, the adhesiveness is increased, so that a load is imposed on cleaning or a transfer failure occurs. Further, the discharge product is easily adsorbed, and if the discharge product is adsorbed, the discharge product is easily affected by humidity, the resistance is reduced in a high humidity environment, the electric charge flows, and an abnormal image is formed. Therefore, the protective agent deteriorated in the discharge region needs to be removed from the surface of the photoreceptor immediately after passing through the discharge region.

  A part of the deteriorated protective agent is considered to be removed from the surface of the photoconductor in the normal image forming process together with the developer in the transfer process, the cleaning process, etc., but a part of it remains on the surface of the photoconductor. Then, it reaches the discharge area again. Such a deteriorated protective agent that could not be removed repeatedly passes through the discharge region, gradually accumulates on the surface of the photoreceptor, and may reach an amount that causes an abnormal image.

  An abnormal image when a deteriorated protective agent is attached means that a deteriorated protective agent is attached to the surface of the photosensitive member, and as a result, a toner image is not formed normally. An image cannot be obtained. As a mechanism in which a normal toner image is not formed, the surface energy on the surface of the photoconductor changes due to the attachment of a deteriorated protective agent, and even when the development conditions are the same, the toner adhesion amount changes or deteriorates. This is because the charging by the charging device is not correctly performed due to the adhesion of the protective agent, or the latent image is not correctly formed.

In addition, in the normal image forming process, a part of the deteriorated protective agent is removed, but the removal amount largely depends on the image pattern and the image area ratio. Will cause non-uniform accumulation of deteriorated protective agent.
Therefore, it is desirable to remove the deteriorated protective agent from the entire surface of the photosensitive member at once at an appropriate time before an abnormal image is obtained.

  As described above, when an unnecessary product such as a discharge product or a deteriorated protective agent adheres, the electric resistance of the photoconductor becomes inappropriate. If the surface resistivity is low, the charge formed on the surface of the photoreceptor spreads in all directions and the charge pattern is destroyed. Further, when the volume resistivity is low, a charge spread occurs in the photosensitive layer in the process of forming the electrostatic latent image, and a correct charge pattern cannot be formed. This phenomenon becomes worse as the resistivity is lower, and the image appears as a phenomenon such as character thickening, sharpness deterioration, and contrast reduction.

  In Patent Document 1, the relationship between the surface resistivity and volume resistivity of the photoreceptor and the image is described, and depending on the cleaning method, good surface resistivity and volume resistivity can be maintained, resulting in poor image quality. However, there is no description about cleaning while measuring and monitoring the surface resistivity and volume resistivity.

As a method for measuring surface resistivity and volume resistivity, a static measurement method as described in Patent Document 1 has been proposed. Create ring electrodes using flexible indium foil as an electrode material so that it can be easily attached to drum-shaped photoconductors and resin photoconductors such as organic photoconductors. As a circuit, a DC power source and an ammeter (for example, an electrometer 617 capable of measuring 10 ⁻¹⁴ A or less are connected), an applied voltage is set to 100 to 500 V, and 1 minute after voltage application The surface resistivity and volume resistance value are calculated by reading the current. In this method, the surface resistivity and the volume resistance value cannot be measured during image formation or during driving of the image forming apparatus.

  As a countermeasure for eliminating the influence of such unwanted substances adhering to the surface of the photoconductor and maintaining the image quality, as described in Patent Document 2, a reference toner image formed on the surface of the photoconductor is an optical image. There has been proposed a method for removing a deterioration product of a protective agent applied to prevent deterioration of a photoreceptor due to proximity discharge, which is detected by a density sensor and deposited on the surface of the photoreceptor based on the detection result.

  The present invention has been made in view of the above background, and an object of the present invention is to provide discharge products such as ozone and nitrogen oxide (NOx) generated by charging means or latent images in an image forming apparatus. Unnecessary materials such as a protective agent supplied to the surface of the latent image carrier to prevent the surface of the carrier from accumulating accumulate on the surface of the latent image carrier, and abnormal images such as image unevenness and low resolution images are generated. It is an object of the present invention to provide an image forming apparatus and a process cartridge capable of preventing the above-described problem.

In the image forming apparatus, the inventors prevent discharge products such as ozone and nitrogen oxide (NOx) generated by the charging means accumulated on the surface of the latent image carrier or deterioration of the surface of the latent image carrier. Therefore, before an unnecessary object such as a protective agent supplied to the surface of the latent image carrier generates an abnormal image, the electrical resistance of the surface of the latent image carrier is detected, and the latent image carrier is detected according to the detected electrical resistance. The present invention has been completed by finding that the generation of an abnormal image can be suppressed before the occurrence of an abnormal image by appropriately removing unnecessary materials that cause a decrease in the resistance of the body surface.
That is, the present invention relates to an image forming apparatus as described below.

(1) a latent image carrier;
Charging means for charging the surface of the latent image carrier;
An electrostatic latent image forming means for forming an electrostatic latent image on the surface of the latent image carrier charged by the charging means;
Developing means for visualizing the formed electrostatic latent image with toner;
Transfer means for transferring the visualized toner image to the transfer target;
Toner cleaning means for removing toner remaining on the surface of the latent image carrier after transfer;
In an image forming apparatus comprising:
Electrical resistance detection means for detecting electrical resistance of the latent image carrier surface;
Means for performing a cleaning operation on the surface of the latent image carrier based on a detection result by the electric resistance detection means;
An image forming apparatus comprising:
(2) The image forming apparatus according to (1), wherein the electric resistance detecting means detects an electric resistance of the surface of the latent image carrier being driven.
(3) The image forming apparatus according to (1) or (2), further comprising a protective agent supply unit that supplies a protective agent for the latent image carrier to the surface of the latent image carrier.
(4) The image forming apparatus according to any one of (1) to (3), wherein the electrical resistance detecting unit includes an electrode that contacts the latent image carrier, a DC power source, a resistor, and a potentiometer. apparatus.
(5) The developing means is a magnetic brush type developing means, and the means for performing the cleaning operation on the surface of the latent image carrier based on the detection result by the electric resistance detecting means is a magnetic brush of the developing device, The image forming apparatus according to any one of (1) to (4), wherein an operating condition of the magnetic brush is determined based on a relational expression: “I-Iref” (Iref is a normal photoconductor detection value). .
(6) The means for performing the cleaning operation on the surface of the latent image carrier based on the detection result by the electric resistance detection means is a toner cleaning means, and based on the relational expression “I-Iref”, the toner cleaning means The image forming apparatus according to any one of (1) to (4), wherein operating conditions are determined.
(7) The means for performing the cleaning operation on the surface of the latent image carrier based on the detection result by the electrical resistance detection means is a transfer means for mediating the movement of the toner from the latent image carrier to the paper. The image forming apparatus according to any one of (1) to (4), wherein an operation condition of the transfer unit is determined based on “I-Iref”.
(8) The means for performing the cleaning operation on the surface of the latent image carrier based on the detection result by the electric resistance detection means is a polishing means provided with a separation / contact mechanism with the latent image carrier, and the latent image carrier The polishing means comes into contact with the latent image carrier based on the output value P of the sensor for detecting the surface, and the contact time is determined based on the relational expression: “I-Iref” (1) (4) The image forming apparatus according to any one of (4).
(9) The means for performing the cleaning operation on the surface of the latent image carrier based on the detection result by the electric resistance detection means operates during non-image formation. The image forming apparatus according to any one of (3) to (9), wherein the protective agent is not supplied to the surface of the latent image carrier during the image forming apparatus (10) removing operation.
(11) The image forming apparatus according to any one of (3) to (10), wherein the protective agent includes zinc stearate and / or zinc palmitate.
(12) After charging the surface of the latent image carrier,
Forming an electrostatic latent image on the surface of the latent image carrier;
Supplying toner to the latent image on the surface of the latent image carrier to form a toner image;
Transfer the toner image formed on the surface of the latent image carrier to a non-transfer body,
Cleaning the toner remaining on the latent image carrier surface after transfer,
In an image forming method comprising a step of supplying a latent image carrier protective agent to the surface of the latent image carrier,
Detect the electrical resistance of the latent image carrier surface,
An image forming method comprising performing a cleaning operation on the surface of the latent image carrier based on the detected electrical resistance.

According to the present invention, the electrical resistance of the surface of the latent image carrier is detected, and the discharge product such as nitrogen oxide (NOx) generated by the charging means deposited on the surface of the latent image carrier based on the detection result. Can be formed, and high-quality images with good sharpness and high resolution can be formed over a long period of time without image unevenness.
Further, according to the present invention, the electrical resistance of the surface of the latent image carrier being driven is detected, and the removal device is driven based on the detection result to deposit on the surface of the latent image carrier before an abnormal image is generated. In addition, discharge products such as nitrogen oxide (NOx) generated by the charging means can be removed, and high-quality images with good sharpness and high resolution can be formed over a long period of time without image unevenness. .
According to the present invention, the electrical resistance of the surface of the latent image carrier is detected, and the discharge of ozone, nitrogen oxide (NOx), etc. generated by the charging means deposited on the surface of the latent image carrier based on the detection result. Remove unnecessary products such as deterioration of the product or the protective agent applied to prevent deterioration of the latent image carrier, and form high-quality images with good sharpness and high resolution without image unevenness over the long term can do.

1 is a diagram illustrating a schematic configuration of a tandem color printer that is an embodiment of the present invention. FIG. 1 is a diagram illustrating an example of a schematic configuration of an image forming apparatus using an indirect electrophotographic method. 1 is a diagram illustrating an example of a schematic configuration of an image forming apparatus using an indirect electrophotographic method. It is a figure which shows the method of performing the detection of the electric current of the circuit containing a photoconductor using an elastic body roller. It is a figure which shows the method of performing the detection of the electric current of the circuit containing a photoconductor using an elastic body roller. FIG. 6 is a diagram illustrating a relationship between a detected current value and resolution on a transfer sheet in the current detection method illustrated in FIG. 5. FIG. 6 is a diagram illustrating a relationship between a current detection value in the current detection method illustrated in FIG. 5 and a change in charge level measured by the surface electrometer S illustrated in FIG. 2. It is a figure which shows the method of performing the detection of the electric current of the circuit containing a photoconductor using a charging roller. It is a figure which shows the method of performing the detection of the electric current of the circuit containing a photoreceptor using a blade-shaped electrode. It is a figure which shows the flowchart for performing the removal operation | movement of an unnecessary object. It is a figure which shows schematic structure of the image forming apparatus at the time of providing the grinding | polishing means of a blade form as a means to remove an unnecessary thing. (A): It is a schematic block diagram of the experimental apparatus for confirming that photoreceptor deterioration is suppressed by proximity discharge. (B) It is a figure which shows the state which divided the photoreceptor surface into the protective agent presence part A and the non-existence part B. FIG. It is a figure which shows the method of removing the deteriorated zinc stearate by retaining toner as an abrasive particle in the contact part of a cleaning blade.

FIG. 1 is a schematic configuration diagram of a color copying apparatus showing an example of an image forming apparatus to which the present invention is applied. The copying apparatus main body is provided with an endless belt-like intermediate transfer member (intermediate transfer belt) 56 as a primary transfer medium in the center.
The intermediate transfer belt 56 is wound around three support rollers 52, 53, and 54 so as to be able to rotate and convey clockwise in the drawing. In the illustrated example, an intermediate transfer member cleaning device 57 that removes residual toner remaining on the intermediate transfer belt 10 after image transfer is provided on the left of the second support roller 53 among the three. Further, among the three, the intermediate transfer belt 56 stretched between the second support roller 53 and the third support roller 54 has yellow (Y), magenta (M), and cyan along the conveyance direction. (C) Four image forming units (image forming units for each color) 1Y, 1M, 1C, and 1K of black (K) are arranged side by side to constitute a tandem type image forming unit 9. However, these four color orders are merely examples, and the present invention is not limited to these.

  FIG. 2 shows a schematic configuration diagram of an image forming apparatus using the indirect electrophotographic method (basic configuration example). In the image forming apparatus of FIG. 2, a charging device 2, an image exposure device (not shown), a developing device 4, a transfer device 51, and a cleaning device 3 are arranged in this order on the periphery of the photoreceptor 1. Further, the fixing device 7 shown in FIG. 1 is arranged (based on the Carlson process), and an image is transferred to a transfer target P (transfer paper, OHP sheet, or the like). L is light for forming a latent image on the photoconductor, and S is a surface electrometer for measuring the potential of the surface of the photoconductor.

  The photoreceptor 1 used in the present invention has a configuration in which an undercoat layer and then a photosensitive layer are formed on a drum-like conductive support made of a material such as aluminum. The photosensitive layer is a function-separated type photoconductor further comprising a charge generation layer and a charge transport layer. The charging polarity when forming the electrostatic latent image is negative.

  The charge transport layer is composed of a charge transport layer in which no filler is dispersed (referred to as charge transport layer A) and a charge transport layer in which an inorganic filler is dispersed (referred to as charge transport layer B). The reason why the filler is dispersed in the charge transport layer B is to prevent deterioration of electrophotographic characteristics (for example, charging characteristics, sensitivity, etc.) by suppressing the photoconductor from being worn more than necessary (electrical, mechanical) This is for the purpose of improving stability. In addition, when a cleaning blade is used, biting into the photosensitive layer is reduced to reduce edge distortion of the blade and to prevent toner cleaning failure. That is, it is a suitable means for maintaining a high-quality image over a long period of time.

The charge transport layer has a two-layer structure because the residual potential is increased by adding a filler having a high resistivity (10 ¹² to 10 ¹⁴ Ω · cm), and the image quality (image density, resolution) is increased by accumulation. This is to suppress the deterioration of the above as much as possible. However, it is desirable to change the amount of filler added depending on the charging means, and it is preferable to use a small amount in the corona charging method described later and to increase it in the contact charging method or the non-contact charging method. This is to cope with a difference in hazard given to the photoreceptor.
The filler dispersed in the charge transport layer B is preferably α-alumina, but may be metal oxide fine particles such as titanium oxide. However, it is not preferable from the viewpoint of resolution retention characteristics to disperse fillers that tend to be reduced in resistance by ozone, such as silica (SiO ₂ ).

  By using the charging device 2 (adopting any one of a corona charging method, a contact charging method, and a non-contact charging method arranged several tens of micrometers away from the photosensitive member 1), the photosensitive member 1 is necessary for image formation. Charged to surface potential. A high voltage power supply circuit (not shown) is connected to the charging member 2a in FIG. The high-voltage power supply circuit includes a circuit that generates either a DC voltage or a DC voltage on which an AC voltage is superimposed.

The roller-type charging member 2a shown in FIG. 2 is manufactured, for example, by covering a core bar of a SUS round bar having a diameter of 5 mm to 15 mm with an elastic member. The elastic member that charges the photosensitive member is added with a resistance control material such as conductive carbon, carbon fiber powder, or ionic conductive agent in epichlorohydrin rubber or urethane rubber, and if necessary, water repellent such as fluorine resin. The volume resistivity is adjusted to 10 ⁵ to 10 ¹⁴ Ω · cm by adding an agent, and the applied volume resistivity needs to be changed between the contact charging member and the non-contact charging member.

In the case of a non-contact charging member, the volume resistivity of the outermost surface is set to 10 ⁵ to 10 ⁸ Ω · cm, and in the case of a contact charging member, the volume resistivity of the outermost surface is set to 10 ¹² to 10 ¹⁴ Ω · cm. The This is because there is a gap between the charging member and the photosensitive member, so that the charging start voltage (Vth) is shifted to the higher side and the charging efficiency is different. In order to perform uniform charging, the volume resistivity of the charging member is Need to be low. However, if the volume resistivity is lowered too much, it causes discharge breakdown, so it is desirable to set it to 10 ⁵ Ω · cm or more.

  Although the final outer diameter of the charging member 2a is set according to the system conditions, it is usually about φ10 to φ20 (mm). In order to obtain good image forming properties, it is desirable that the contrast potential is at least 250 V or more, and the charging potential for this purpose is preferably -400 V to -800 V.

On the surface of the photosensitive member 1 that has been charged, an original image read by a CCD (charge coupled device) or a digital signal transmitted from a personal computer or the like is provided with one or a plurality of LD (Laser Diode) elements or LEDs (LEDs). A single-wavelength light image L, which is narrowed down to a dot diameter of about 60 to 20 μm, is irradiated by an image exposure device (not shown) composed of a laser emitting diode (array), a convex lens, a polygon mirror, a cylindrical lens, and the like. An electrostatic latent image is formed.
For the LD element or LED array (wavelength: 780 to 400 nm), an element having an oscillation wavelength at or near the highest sensitivity region of the photoreceptor is selected. Since the spot diameter can be narrowed as the oscillation wavelength becomes shorter, an LD element having an oscillation wavelength on the short wavelength side of about 400 to 450 nm is advantageous when obtaining a high resolution such as 1200 dpi or 2400 dpi.

The electrostatic latent image is visualized by the developing device 4. There are one-component and two-component developers. In the present invention, a two-component developer (carrier and toner) is used for development.
In the developing device 4 shown in FIG. 2, 4a is a developing roller, 4b is a toner supply roller, and 4c is a doctor blade.
Carriers used in two-component developers include, for example, polyfluorinated carbon to improve the charging properties, charging stability, durability, etc. of magnetic powders (magnetic powders) such as iron, ferrite and nickel A material coated with a resin such as polyvinyl chloride or polyvinylidene chloride is used. The particle size of the carrier is about 30 to 60 μm. The particle size of the carrier affects the resolution, and the smaller the resolution, the more the resolution tends to improve. For this reason, toner image transfer failure (transfer omission) occurs, or the blade is pressed against the photoconductor by being transported to the cleaning unit. As a result, the photoconductor surface is damaged and the surface roughness is increased, resulting in deterioration of image quality. In addition, the discharge product enters the uneven portion and causes the image to flow, which also contributes to shortening the durability of the photoreceptor.

On the other hand, as the toner, toner produced by a pulverization method and then spheroidized by scraping off the angular portions of the particles (average circularity of 0.9 to 0.94) or polymerization method (emulsion polymerization method, suspension weight) A spherical toner having a weight average particle diameter of 4 to 8 μm (average circularity of 0.95 to 1.0) manufactured by a legal method or the like, and 2 to 10% by weight based on the carrier as a two-component developer. Used by mixing.
The particle size of the toner affects the resolution as well as the carrier. However, if it is too small, it will easily scatter, and will float in the atmosphere for a long time. It is desirable to remove the fine particles of about 1 to 3 μm.

  Next, the toner image is transferred to the intermediate transfer belt 56 by a transfer device 51 (corona discharge type, roller, belt type, etc.) to which a plus voltage is applied, and further, the transfer target conveyed from the cassette from the intermediate transfer belt 56. The image is transferred to P (transfer paper, OHP sheet, etc.), and the transfer medium P is separated from the intermediate transfer belt 56 by the separating device 6 and sent to the fixing device 7. Residual powder such as toner on the photoreceptor 1 is cleaned by the cleaning device 3.

2, the cleaning device 3 includes a protective agent coating device 8 (8a: application brush, 8b: protective agent, 8c) for the purpose of reducing the surface friction coefficient of the photoconductor 1 and protecting the photoconductor from hazards such as discharge. : A pressure spring) and a cleaning blade 3a. In FIG. 2, reference numeral 3b denotes a member constituting a part of the cleaning blade 3a, a support member (metal or the like) for supporting a blade (elastic body) constituting an end of the cleaning blade 3a, and 3d a pressure spring. It is.
FIG. 3 shows another example of the cleaning device. For the purpose of applying a protective agent to the photoreceptor after passing through the cleaning blade and then extending the protective agent, the cleaning blade 3 a is used to make the protective agent applying device 8. The protective agent coating blade 8 d is disposed on the upstream side of the image process, and the protective agent coating blade 8 d is disposed on the downstream side of the image forming process of the protective agent coating device 8. 8f is a pressure spring of the protective agent application blade 8d. In FIG. 3, 8e is a member constituting a part of the protective agent coating blade 8d, and a blade (elastic body) support member (metal or the like) constituting the end of the protective agent coating blade 8d.
Various effects other than the above can be obtained by applying the protective agent. For example, improved cleaning performance (especially effective for spherical toner with a circularity of nearly 1.0), suppression of deformation (distortion) of the cleaning member, relaxation of toner adhesion to the photoreceptor, prevention of sharpness degradation, For example, wear suppression. However, if the friction coefficient is too low, faithful development with respect to the electrostatic latent image is hindered, and the grinding force of the discharge product adhering to the photoreceptor is lacking, which causes a reduction in resolution and image flow. The protective agent will be further described later.

A series of image forming cycles is completed by the above-described charging-cleaning- (protecting agent application), and the next image forming process is repeated again.
The image forming process described with reference to FIG. 2 can also be applied to a full-color image forming apparatus as shown in FIG. In a full-color electrophotographic copying machine or printer, one drum in which four systems (colors) of magenta (M), cyan (C), yellow (Y), and black (Bk) are arranged on one photosensitive member. Type image forming apparatus or four photoconductors and magenta (M), cyan (C), yellow (Y), and black (Bk) developing systems (color) as shown in the schematic diagram of FIG. There is an image forming apparatus of a quadruple tandem type image forming system in which is provided.
Further, by combining two or more of the photosensitive member 1, the charging device 2, the developing device 4, the cleaning device 3 including the coating brush 8a and the cleaning blade 3a shown in FIG. The process cartridge can be detachably attached to the apparatus main body.

  Hereinafter, a first embodiment of an image forming apparatus to which the present invention is applied will be described. In the image forming apparatus to which the present invention is applied, the electrical resistance (hereinafter also referred to as resistance) of the photoconductor is detected by a detection unit, and is accumulated on the surface of the photoconductor before an abnormal image is generated according to the detection result. It has a removal operation for removing unnecessary materials that cause abnormal images. Hereinafter, a resistance measurement method and a method for removing unnecessary substances attached on the surface of the photoreceptor will be described.

  The resistance detection means comprises a voltage application means, a current detection resistor, an electrometer, etc., and is provided with a control means having a CPU, detects the current flowing through the photosensitive member, and the current value is input to the control means. In accordance with a program set in advance corresponding to this input, a removal operation for removing unnecessary substances adhering to the surface of the photoreceptor is determined. In order to measure the resistance of the photoconductor, it is necessary to convert it from the detected current and other conditions, but since there is a relationship between the current value detected by this circuit and the abnormal image, it is converted here to resistivity. Not done. The surface resistivity / volume resistivity may be calculated, the relationship between the resistivity and the abnormal image may be grasped, and the removal operation may be determined according to the change in resistivity.

  The current (Iref) that flows when a normal photoconductor is used is detected in advance and recorded in the program of the control means. Thereafter, the current (I) flowing through the photosensitive member is detected in the same manner, for example, after the prints are overlaid, and the relationship between each current difference “I-Iref” and the abnormal image is grasped in advance so that the abnormal image can be viewed. The accumulation state of the deteriorating substance on the surface of the photoreceptor is detected depending on whether or not the current difference is greater.

A current detection method A for a circuit including a photoreceptor in the present invention will be described with reference to FIG. In FIG. 5, the cleaning device 3 and the developing device 4 are omitted, but FIG. 4 also shows the cleaning device 3 and the developing device 4 together.
As shown in FIG. 5, the elastic roller 100 is brought into contact with the photosensitive member at an appropriate linear pressure, for example, 40 g / cm so that both axes are parallel, and a DC power source 102, a current detecting resistor 101, The potentiometer 103 is connected. A voltage is applied from the DC power supply to the circuit, and the value of the potential difference Vr at each voltage of the resistance having an appropriate resistance value inserted downstream of the photosensitive element tube is sent to the control CPU via the AD converter. By inputting, the current value I flowing in the circuit is detected. At the time of current measurement, it is desirable that the photoconductor is in a cleaned state and all members in contact with the photoconductor other than the cleaning blade 3a are separated from the photoconductor. Any member that does not leak current from the current detection circuit, such as the protective agent application brush 8a that is not grounded, may remain in contact with the photosensitive member. When the protective agent application brush is also grounded, it is desirable to separate it.

To the elastic roller, add resistance control material such as conductive carbon, carbon fiber powder, ionic conductive agent to epichlorohydrin rubber or urethane rubber, and further add water repellent such as fluorine resin if necessary. The volume resistivity adjusted to 10 ¹ to 10 ⁵ Ω · cm is used. The volume resistivity should be as low as possible. The diameter of the elastic roller is not particularly limited, and may be any size that can be laid out, such as φ5 mm to φ15 mm. A larger diameter can widen the contact nip with the photoconductor, which is advantageous for detection because more current is detected. The length of the elastic roller can be the highest in detection accuracy over the entire width of the photoconductor, but may be a length that does not affect the image and touches only outside the image forming area of the photoconductor. The elastic roller is driven and rotated so that the surface speed is the same as that of the photosensitive member. Further, the photosensitive member may be driven. If necessary, an elastic roller cleaning device may be provided.

  Since the measured current is very small, it is preferable to use a current detection resistor having a very low resistance of about several tens of mΩ such as a shunt resistor so that the influence of the resistance can be reduced as much as possible during detection. Since the photoconductor is an insulator in a dark place, it is necessary to detect a current in the state of a conductor in a bright place. For example, the current value at the time of the entire exposure by the exposure means is detected by a current detection resistor. At the time of image formation, the current detecting elastic roller 100 is separated from the photosensitive member.

  FIG. 6 is a diagram showing the relationship between the detected current value and the resolution on the transfer paper in the current detection method A of the circuit. The measurement environment is 23 ° C./65% RH. The voltage applied from the DC power supply is 2 KV. If the current value (I) is too large or too small than the current (Iref) that flows when a normal photoconductor is used, the resolution will deteriorate. The allowable resolution is 6 lines / mm.

FIG. 7 is a diagram showing the relationship between the detected current value in the current detection method A of the circuit and the change in charge level measured by the surface electrometer S in FIG. The measurement conditions were the same as in the case of FIG. The amount of change in the charging potential on the vertical axis indicates the difference (V−Vref) between the charging potential (Vref) when a normal photosensitive member is used and the photosensitive member charging potential (V) when each current is detected. Yes. When the current value (I) is close to the current (Iref) that flows when a normal photoconductor is used, the difference in charging potential is small. However, as the current (I) increases, the amount of decrease in charge level increases. As the current (I) decreases, the charging potential increases.
The resolution and charging potential vary depending on the discharge product attached to the surface of the photoreceptor and the accumulated protective agent, but the allowable range of current that does not cause the resolution and charging potential to be abnormal is “I−Iref” ≦ α × Iref Predetermined by (0 <α <1). The allowable range is determined by a constant α, and it is desirable that the allowable range is set so as not to cause an abnormal image even when “I−Iref” = αIref.

  Next, a current detection method B, which is another method for detecting the current of the circuit including the photoreceptor in the present invention, will be described. As shown in FIG. 8, in the case of an image forming apparatus using contact roller charging, the circuit current can be measured using the charging roller 2a. As the DC power source 102, a charging power source can be used.

  FIG. 9 shows a current detection method C which is another method for detecting the current of the circuit including the photosensitive member in the present invention. For example, a metal foil (thickness of about 0.1 mm) such as aluminum, copper, or indium is cut out so that there is no burr at the end, and two blade-shaped electrodes having a width of 10 mm and a length of 20 mm are produced. Attached and brought into contact with the photosensitive member surface so as to apply an appropriate pressure at intervals, and the current flowing through the circuit is measured. In FIG. 9, the current between almost the entire widths of the photoconductor width is measured so that the influence of partial adhesion of the protective agent can be detected.

In the operation of removing unnecessary products such as discharge products and deteriorated protective agents, the output value I of the current detection means is input to the control means, and the presence or absence of the removal operation is determined according to the flowchart shown in FIG.
As described above, when an unnecessary object is present on the surface of the photoconductor, the current value I flowing through the circuit is different from Iref. By using such a relationship, it is possible to determine the necessity of the removal operation from the difference between the current values I and Iref flowing in the circuit, instead of directly detecting the amount of unnecessary matter. In the current value detection operation of the circuit, for example, image formation is performed at the time when image formation is forcibly paused for each number of prints or every continuous print, or when the power is turned on or at the end of the print operation. It may be performed at a time that is not available, but may be set as appropriate depending on the model configuration.

Next, an operation for removing unnecessary substances on the surface of the photoreceptor will be described based on the detection result obtained by the detection means.
As a first method for removing unnecessary products such as a discharge product and a deteriorated protective agent on the surface of the photoreceptor, a method using a magnetic brush of a developing device can be mentioned.

  The removal operation is performed during non-image formation. During the removal operation, only the photoconductor, the charging device, and the developing device are in a movable state, and an unnecessary object that adheres to and accumulates on the surface of the photoconductor by rubbing the charged photoconductor surface by the rotation of the magnetic brush of the developing device. Remove. In order to perform a removal operation according to the amount of unwanted matter on the surface of the photoreceptor, a removal operation condition is determined based on the sensor output value “I-Iref”. Specifically, there is a method of making the linear velocity difference between the developing roller and the photosensitive member larger than that during the image forming operation based on “I-Iref”. Alternatively, when the rotation direction of the developing roller and the photosensitive member during image formation is the trailing direction, there is a method in which the rotating direction of the developing roller and the photosensitive member is set to the counter direction during the removal operation. As another removal operation, there is a method of adjusting the removal operation time based on “I-Iref” while keeping the rotation speeds of the developing roller and the photosensitive member constant. As described above, by determining the removal operation condition according to the surface state of the photoconductor, it is possible to prevent the occurrence of an abnormal image due to insufficient removal and excessive shaving of the surface of the photoconductor.

As a second method for removing unnecessary substances, a method using toner removing means can be mentioned.
The removal operation is performed during non-image formation. A cleaning blade is usually used as the toner removing means. There is a method in which abrasive particles for polishing the surface of the photoreceptor are retained between the cleaning blade and the photoreceptor during the removal operation, and unnecessary substances are removed from the surface of the photoreceptor by the abrasive particles. Specifically, there are the following removal methods. During the removal operation, only the photosensitive member and the developing device are in a movable state, and transfer is not performed. During the removing operation, a toner image is formed on the surface of the photoreceptor by the developing device. The toner image reaches the cleaning blade as it is without being transferred, stays between the cleaning blade and the rotating photoconductor, acts as an abrasive, and removes unnecessary materials on the surface of the photoconductor. In order to perform a removal operation according to the amount of unwanted matter on the surface of the photoreceptor, a removal condition is determined based on the sensor output value “I-Iref”. The removal amount can be adjusted based on “I-Iref” by adjusting the toner developing amount on the surface of the photosensitive member by the developing bias and adjusting the amount of toner reaching the cleaning unit. When the removal operation time is constant, the amount of abrasion on the surface of the photoreceptor increases as the amount of toner in the cleaning unit increases.
As another adjustment method, there is a method in which the toner image developed on the surface of the photoreceptor during the removal operation is made constant, and the removal operation time is set based on “I-Iref”.

As a third method for removing unnecessary substances, a method using an intermediate transfer member can be exemplified.
The removal operation is performed during non-image formation. At the time of the removal operation, only the photosensitive member and the intermediate transfer member are in a movable state, and the intermediate transfer member rubs the surface of the photosensitive member to remove unnecessary substances attached and accumulated on the surface of the photosensitive member. In order to perform a removal operation in accordance with the amount of unwanted matter, a removal condition is determined based on the sensor output value “I-Iref”.
By making the difference between the rotation speed of the intermediate transfer member and the rotation speed of the photosensitive member larger than that during the image forming operation based on “I-Iref”, the rubbing force between the intermediate transfer member and the photosensitive member is changed. There is a way to do it. As another method, there is a method of determining the removal operation time, that is, the rotation time of the intermediate transfer member based on “I-Iref”. As described above, by determining the removal operation condition according to the surface state of the photoconductor, it is possible to prevent the occurrence of an abnormal image due to insufficient removal and excessive shaving of the surface of the photoconductor.

As a fourth method for removing unnecessary materials, a method using a polishing means can be mentioned.
Examples of the polishing means include a roller form and a blade form. FIG. 11 shows a polishing blade 9a in the form of a blade as an example of the polishing means.
In FIG. 11, reference numeral 9b denotes a member constituting a part of the polishing blade 9a, and a support material (metal or the like) for supporting the blade (elastic body) constituting the end of the polishing blade 9a. After the unnecessary material is removed by the polishing blade 9a, the protective agent is applied thinly by the protective agent applying devices 8a to 8c, and the protective agent is extended by the cleaning blade 3a, and most of the residual powder. A process for cleaning is performed. Reference numeral 9d denotes a pressure spring of the polishing blade 9a.
In the removing operation, the surface of the photosensitive member is polished by bringing a polishing blade into contact with the surface of the photosensitive member during non-image formation. At the time of image formation, a separation / contact mechanism is provided so that the polishing blade is not in contact with the surface of the photoreceptor. The polishing amount is adjusted by the contact time determined by “I-Iref”. As described above, by determining the removal operation condition according to the surface state of the photoconductor, it is possible to prevent the occurrence of an abnormal image due to insufficient removal and excessive shaving of the surface of the photoconductor.

The protective agent for the photoreceptor surface will be described.
Various substances can be used as the protective agent 8b for protecting the photoreceptor from deterioration against electric discharge. In the image forming apparatus of the present embodiment, zinc stearate is used as the protective agent 8b, but zinc stearate is an example of the protective agent 8b, and other substances such as various fatty acid salts, waxes, silicone oils, and the like are used as the protective agent. It can also be used as 8b. Examples of fatty acids include undecyl acid, lauric acid, tridecyl acid, myristic acid, palmitic acid, pendadecyl acid, stearic acid, heptadecyl acid, arachidic acid, montanic acid, oleic acid, arachidonic acid, caprylic acid, capric acid, caproic acid, etc. Examples of the metal salt include salts with metals such as zinc, iron, copper, magnesium, aluminum, and calcium.

It is preferable to use a lamellar crystal powder such as zinc stearate as the protective agent.
A lamellar crystal has a layered structure in which amphiphilic molecules are self-organized, and when a shearing force is applied, the crystal breaks along the layers and is slippery. This action is effective for lowering the coefficient of friction, but also from the viewpoint of protecting the photoreceptor surface from discharge, the characteristics of the lamellar crystal that uniformly covers the surface of the object to be charged under shear force Is desirable as a protective agent because it can effectively cover the surface of the photoreceptor with a small amount of protective agent. In order to fully protect the surface of the photoreceptor from electric discharge by fully utilizing the properties of the lamellar crystals, the protective agent coating device 8 has a linear velocity difference from the surface of the photoreceptor, and the protective agent while acting a shearing force. It is desirable to apply.

Next, a method for supplying the protective agent will be described.
As shown in FIG. 2, the image forming apparatus of the present embodiment is provided with a protective agent coating device 8 as a protective agent supply means for supplying the protective agent 8b to the surface of the photoreceptor. The protective agent application device 8 includes an application brush 8a, a protective agent 8b, and a pressure spring 8c for pressing the protective agent in the fur brush direction. The protective agent 8b is a solid molded into a bar shape. The application brush 8a has a brush tip abutting on the surface of the photosensitive member. By rotating about the shaft, the protective agent 8b is pumped up to one end of the brush, and is carried and conveyed on the brush to a contact position with the surface of the photosensitive member. Apply to body surface.
Further, even if the protective agent 8b is scraped off by the application brush 8a with time and decreases, the protective agent 8b is pressed against the application brush 8a with a predetermined pressure by the pressurizing spring 8c so as not to come into contact with the application brush 8a. Has been. As a result, even a small amount of the protective agent 8b is always uniformly pumped up to the application brush 8a.

  In addition, there is a method of transferring the protective agent 8b to the surface of the photosensitive member by adding or externally adding the protective agent 8b to the toner. Unevenness is likely to occur, and it may be necessary to apply more protective agent 8b than necessary to compensate for this. Since the protective agent 8b is directly applied to the surface of the photoreceptor as in this embodiment, the protective agent can be stably distributed on the surface of the photoreceptor without changing depending on various conditions such as image density and image pattern. . Further, as described later, it is important that the protective agent is present in an appropriate state on the surface of the photoreceptor, and means for transferring the protective agent to the surface of the photoreceptor is not limited to coating.

Next, protection of photoreceptor deterioration will be described.
An experimental result showing that the protective agent 8b functions to suppress deterioration of the photoreceptor due to discharge will be described.
FIG. 12A is a schematic configuration diagram of an experimental apparatus for confirming that deterioration of the photoreceptor due to proximity discharge is suppressed by the presence of the protective agent 8b on the photoreceptor. FIG. 12B is an explanatory diagram of a state in which the surface of the photosensitive member is divided into a protective agent existing portion A and a non-existing portion B.
In order to perform this experiment, all members other than the charging roller 2a and the protective agent application device 8 were removed in advance, and the protective agent application device 8 was configured to apply the protective agent 8b to the half surface area of the photoreceptor 1 in the axial direction. . Then, the charging device 2 and the protective agent coating device 8 were continuously driven together with the photoconductor 1, and the deterioration state of the surface of the photoconductor was examined. The experimental conditions are as follows.

(Charging conditions)
Vpp (peak-to-peak voltage value of AC voltage) = 2.12 [kV]
f (frequency of AC voltage) = 877.2 [Hz]
DC voltage value = −660 [V]
Moving speed of photoreceptor surface v = 125 [mm / s]
Protective agent: Zinc stearate
Line speed of coating brush 8a = 216 [mm / sec]

As shown in FIG. 12B, zinc stearate as a protective agent is applied to the surface of the half area A in the longitudinal direction of the photoreceptor 1, and the surface of the photoreceptor 1 is exposed as it is in the remaining half area B. It has become. Further, the film abrasion amount of the photosensitive layer was measured as an index of the surface degradation of the photoreceptor 1.
In the region B where the protective agent 8b is not present, the film scraping amount increased with the passage of time, and after 200 hours, the film thickness decreased by about 2.5 [μm]. On the other hand, in the region A where the protective agent 8b is present, the decrease in film thickness was suppressed to 1/8 or less. Further, when the surface of the photoreceptor used in the experiment was visually observed after 200 hours, in the region B where the protective agent 8b was not present, the surface of the member to be charged turned white and deteriorated, whereas the protective agent 8b was present. In the area A, the mirror surface was kept in the same manner as the new photoreceptor 1.

In addition, the remnants of molecules constituting the photoconductor are detected from the analysis from the surface of the photoconductor in the region B without the protective agent 8b, whereas in the region A where the protective agent 8b is present, the molecules constituting the photoconductor are detected. No debris was detected, and the photoreceptor surface under the protective agent 8b was not deteriorated. And in the area | region A, the zinc stearate supplied as a protective agent in this experiment chemically changed, and the decomposed | disassembled substance was detected.
From the above experimental results, it has been clarified that the presence of the protective agent 8b suppresses deterioration of the surface of the photoreceptor due to discharge.

The tandem color image forming apparatus imagio MP C3500 has been modified to have the entire configuration shown in FIG. 1 and the configuration around the photoconductor as shown in FIG. 2. The photoconductor 1 has a diameter of 40 mm, a photosensitive layer length of 326 mm, and a linear velocity of 280 mm / s. did.
First, as shown in FIG. 5, a new photoconductor was used, the elastic roller 100 was brought into contact with the photoconductor, and the current value I flowing through the circuit was detected. The elastic roller 100 is prepared by adding conductive carbon to epichlorohydrin rubber and adjusting the volume resistivity to 10 ⁵ Ω · cm. The diameter is 10 mm, the length is 320 mm, and the hardness is 60 (measured with a durometer type A corresponding to JIS K 6253). On-axis hardness). This was brought into contact with the photoreceptor 1 at 40 g / cm so that both axes were parallel to each other, and rotated so that the surface speed was the same as that of the photoreceptor. The measurement environment is 23 ° C./65% RH. A voltage of 2 KV was applied from the DC power source 102. At this time, when the current value I flowing through the circuit was detected, it was 6.0 × 10 ¹⁶ . This value is Iref. When the resolution was evaluated at this time, it was 7 lines / mm.
Thereafter, as shown in FIG. 12A, all members other than the charging roller 2 a and the protective agent application device 8 are removed in advance, and the protective agent application device 8 is configured to apply the protective agent 8 b to the surface area of the photoreceptor 1. did. Then, the driving of the charging device 2 and the protective agent coating device 8 together with the photoreceptor 1 was continued for about 5 hours under the following conditions.
(Charging conditions)
Vpp (peak-to-peak voltage value of AC voltage) = 2.20 [kV]
f (frequency of AC voltage) = 900 [Hz]
DC voltage value = −660 [V]
Moving speed of photoreceptor surface v = 125 [mm / sec]
Protective agent: Zinc stearate
Line speed of coating brush 8a = 216 [mm / sec]
As a result, deposits adhered to the surface of the photoreceptor. The photoconductor was attached to the modified imgio MP C3500, and the current value I flowing through the circuit was detected in the same manner as in the Iref measurement. As a result, it was 8.0 × 10 ¹³ . In this state, a resolution pattern was output and the resolution was measured and found to be 2 lines / mm. The removal operation is performed when it becomes out of the range of 8.0 × 10 ¹⁷ <“I-Iref” <3.0 × 10 ¹⁵ . In this case, since “I−Iref” = 8.0 × 10 ¹³ , the removal operation was performed.
By using the second method for removing the unnecessary substances, the substances adhering to the surface of the photoreceptor were removed. During the removal operation, only the photosensitive member and the developing device are moved, and no transfer is performed. During the removing operation, a toner image is formed on the surface of the photoreceptor by the developing device. The toner image reached the cleaning blade as it was without being transferred, stayed between the cleaning blade and the rotating photoconductor, and acted as an abrasive to remove unnecessary material on the surface of the photoconductor.
When I after removal was measured, it was 2.0 × 10 ¹⁵ . When the resolution was measured, it was 6 / mm.

  The image forming apparatus of the present invention efficiently removes discharge products such as nitrogen oxide (NOx) generated by the charging means deposited on the surface of the latent image carrier, and has good image sharpness without image unevenness over the long term. Therefore, it can be suitably used as an image forming apparatus using an electrostatic image forming process such as a copying machine, a facsimile, or a printer.

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging apparatus 2a Charging member (charging roller)
3 cleaning device 3a cleaning blade 4 developing device 4a developing roller 4b toner supply roller 4c doctor blade 6 separating device 7 fixing device 8 protective agent coating device 8a coating brush 8b protective agent 8c pressure spring 9a polishing blade 51 primary transfer devices 51Y, 51M , 51C, 51K Transfer rollers 52, 53, 54 Support roller 56 Intermediate transfer belt 57 Intermediate transfer body cleaning device 100 Elastic roller 101 Current detection resistor 102 DC power source 103 Potentiometer L Optical image P Transfer object S Surface potential meter

Japanese Patent No. 4138515 JP 2005-30201 A

Claims (12)

A latent image carrier;
Charging means for charging the surface of the latent image carrier;
An electrostatic latent image forming means for forming an electrostatic latent image on the surface of the latent image carrier charged by the charging means;
Developing means for visualizing the formed electrostatic latent image with toner;
Transfer means for transferring the visualized toner image to the transfer target;
Toner cleaning means for removing toner remaining on the surface of the latent image carrier after transfer;
In an image forming apparatus comprising:
Electrical resistance detection means for detecting electrical resistance of the latent image carrier surface;
Means for performing a cleaning operation on the surface of the latent image carrier based on a detection result by the electric resistance detection means;
An image forming apparatus comprising: The image forming apparatus according to claim 1, wherein the electric resistance detection unit detects an electric resistance of the surface of the driving latent image carrier. The image forming apparatus according to claim 1, further comprising a protective agent supplying unit that supplies a protective agent for the latent image carrier to the surface of the latent image carrier. The image forming apparatus according to claim 1, wherein the electrical resistance detection unit includes an electrode that contacts the latent image carrier, a DC power source, a resistor, and a potentiometer. The developing means is a magnetic brush type developing means, and the means for performing the cleaning operation of the surface of the latent image carrier based on the detection result by the electric resistance detecting means is a magnetic brush of the developing device, and the relational expression: The image forming apparatus according to claim 1, wherein an operation condition of the magnetic brush is determined based on “I-Iref” (Iref is a normal photoconductor detection value). The means for performing the cleaning operation on the surface of the latent image carrier based on the detection result by the electrical resistance detection means is a toner cleaning means, and the operation condition of the toner cleaning means is determined based on the relational expression “I-Iref”. The image forming apparatus according to claim 1, wherein the image forming apparatus is determined. The means for performing the cleaning operation on the surface of the latent image carrier based on the detection result by the electrical resistance detection means is a transfer means for mediating the movement of the toner from the latent image carrier to the paper. The image forming apparatus according to claim 1, wherein an operation condition of the transfer unit is determined based on “−Iref”. The means for cleaning the surface of the latent image carrier based on the detection result by the electrical resistance detection means is a polishing means provided with a separation / contact mechanism for the latent image carrier, and detects the surface of the latent image carrier. The polishing means is brought into contact with the latent image carrier based on the output value P of the sensor to determine the contact time based on the relational expression "I-Iref". The image forming apparatus according to any one of the above. 9. The image forming apparatus according to claim 5, wherein the means for performing a cleaning operation on the surface of the latent image carrier based on a detection result by the electric resistance detection means operates during non-image formation. The image forming apparatus according to claim 3, wherein the protective agent is not supplied to the surface of the latent image carrier during the removing operation. The image forming apparatus according to claim 3, wherein the protective agent includes zinc stearate and / or zinc palmitate. After charging the latent image carrier surface,
Forming an electrostatic latent image on the surface of the latent image carrier;
Supplying toner to the latent image on the surface of the latent image carrier to form a toner image;
Transfer the toner image formed on the surface of the latent image carrier to a non-transfer body,
Cleaning the toner remaining on the latent image carrier surface after transfer,
In an image forming method comprising a step of supplying a latent image carrier protective agent to the surface of the latent image carrier,
Detect the electrical resistance of the latent image carrier surface,
An image forming method comprising performing a cleaning operation on the surface of the latent image carrier based on the detected electrical resistance.

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