JP2005181941A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of obtaining a good image by suppressing sticking of magnetic particles and preventing the scratches of a photoreceptor. <P>SOLUTION: Regarding the image forming apparatus comprising an image carrier; an electrifying apparatus having an electrifying member coming in contact with the image carrier and for electrifying the image carrier by applying an electrification bias on the electrifying member; an image information writing apparatus for forming an electrostatic latent image on the electrified surface of the image carrier; a developing apparatus for developing the electrostatic latent image with the developer; and a transfer apparatus for transferring the developer image on the image carrier surface to a material to be transferred, and where such a system is introduced that the developer not shifted to the material to be transferred in the transfer apparatus, but, remaining on the image carrier surface is recovered by the electrifying member coming in contact with the image carrier once in the electrifying apparatus, and the recovered developer is discharged from the electrifying member, and then, recovered again by the developing apparatus, the image forming apparatus includes a means for detecting an image ratio in an image forming area, and the presence or absence and conditions of an electrifying operation, an exposure operation and a developing operation are decided on the basis of the value detected by the image ratio detecting means in a period when an image is not formed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a charging device that performs charging processing (including charge removal processing) on a member to be charged. More specifically, the present invention relates to a contact-type charging device (contact charging device, direct charging device) that charges a member to be charged by contacting a charging member to which a voltage is applied to the member to be charged.

  In addition, an image forming process including a process of charging the image carrier by bringing a charging member to which a voltage is applied into contact with the image carrier to perform image formation, an electrophotographic method, an electrostatic recording method, etc. The present invention relates to image forming apparatuses such as copying machines and printers.

  Conventionally, in an electrophotographic image forming apparatus or an electrostatic recording image forming apparatus, a corona charger has generally been used as a charging processing means for an image carrier such as an electrophotographic photosensitive member or an electrostatic recording dielectric. In recent years, since it has advantages such as low ozone and low power, there has been a practical use of a contact charging device, that is, a device for charging a charged object by contacting a charged member to which a voltage is applied to the charged object. Has been made. In particular, a roller charging apparatus using a conductive roller as a charging member is preferably used from the viewpoint of charging stability.

  However, in the roller charging method described above, since the charging is performed by discharging from the charging member to the member to be charged, some discharge products are generated.

  Therefore, recently, as a charging method that does not generate a discharge product, Patent Document 1 and the like apply a voltage to a conductive contact charging member and inject a charge into a trap level (charge injection layer) on the surface of the photoreceptor. A method of performing contact charging is disclosed. This injection charging system not only generates ozone that shortens the life of the photoconductor, but also does not use discharge. Therefore, the applied voltage is sufficient to be approximately the same as the photoconductor potential, and further reduction in power is possible.

  Also, by using injection charging, the transfer residual toner remaining on the photosensitive member without being transferred during image formation is scraped off by the conductive contact charging member (fur brush, magnetic brush, etc.) and charged at the same time. In addition, it is possible to realize a cleaner-less process in which the transfer residual toner accumulated on the contact charging member is discharged onto the photosensitive member at a time other than image formation, and the toner is collected again by the developing device. As a conductive contact charging member, the fur brush is used for a long time, and when the hair falls due to long-term standing, the charging property is deteriorated, whereas with a charged magnetic brush using magnetic particles, such development is not possible. It does not occur, and the density at which the magnetic particles come into contact with the photoconductor is higher than that of the fur brush, so that stable and uniform charging can be performed. In addition, the magnetic brush is more advantageous for cleaner-less processes because it retains a larger amount of transfer residual toner.

  In the cleaner-less process described above, when the charge polarity of the transfer residual toner is the same polarity as the charge polarity of the photoconductor (here, negative electrode), it becomes difficult to collect by the injection charger, and the transfer residual toner is charged by the charger. It slips through and appears in the next image of the photoreceptor (this phenomenon is hereinafter referred to as ghost). As a method for preventing this, a method is known in which a member for inverting the polarity of the residual toner (to the positive electrode here) is provided between the transfer and the charger. Examples of the member include a conductive brush and an elastic body, which are brought into contact with the photoconductor, and a positive voltage is applied to reverse the transfer residual toner to the positive electrode. In particular, when a brush is used, the toner of the negative electrode is temporarily taken into the brush, charged to the positive electrode, and then discharged onto the photoconductor, so that ghosting can be efficiently prevented. The toner taken into the injection charger is charged to the negative electrode again by frictional charging.

  The toner collected in the charger charged to the normal polarity is discharged to the surface of the photoreceptor due to the potential difference between the DC component value of the charging bias and the photoreceptor potential. The potential difference between the charging bias DC and the photoreceptor potential depends on the AC peak-to-peak voltage superimposed on the charging bias. The larger the peak-to-peak voltage, the better the convergence of the photoreceptor potential and the smaller the potential difference. Utilizing this property, the peak-to-peak voltage is increased during non-image formation such as between papers and after rotation, so that the peak-to-peak voltage is increased during image formation so as not to affect the image. The toner in the charger can be actively discharged by reducing the toner amount, and the amount of toner in the charger can be kept low.

Japanese Patent Application No. 05-0666150 Japanese Patent Application Laid-Open No. 2000-075602

  In the cleanerless image forming apparatus, if the surface property of the photoconductor changes due to discharge by a transfer charger or attachment of additives contained in paper due to image formation over a long period of time, the magnetic particles of the magnetic brush are changed. It becomes easy to adhere to the surface of the photoreceptor. Normally, when the magnetic brush charger rotates, the surface of the photoconductor is polished by an external additive contained in the transfer residual toner collected by the magnetic brush, and the surface of the photoconductor is kept constant. There is almost no adhesion.

  However, in the normal image where the image ratio is high, the toner is taken into the magnetic brush charger, and the photoconductor is polished by the particles externally added to the toner, so that magnetic particles are attached. However, the thrust end often has a small image ratio, and the toner concentration in the magnetic brush is also low, so that the polishing ability of the photoreceptor is lowered and magnetic particles tend to adhere. As a result, the magnetic particles easily adhere to the photoreceptor, and image defects such as spots occur at the edge of the image.

  Furthermore, when image formation is performed with a small width paper that uses only the center of the thrust area, the surface of the photoconductor changes due to the discharge of the transfer charger in the non-sheet passing area, but there is no toner consumption. The body is not polished, and similarly magnetic particles are likely to adhere.

  Magnetic particles adhering to the photosensitive member are sandwiched between the transfer belt and the photosensitive member and damage the photosensitive member. In the area where the surface of the photoreceptor is scratched, the contact property of the magnetic brush is deteriorated at the time of the next image formation, so that charging failure occurs and image defects such as spots occur.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus capable of preventing adhesion of magnetic particles to prevent photoconductor scratches and obtaining a good image. is there.

  In order to achieve the above object, the invention described in claim 1 has an image carrier and a charging member that contacts the image carrier, and charges the image carrier by applying a charging bias to the charging member. A charging device, an image information writing device for forming an electrostatic latent image on the charging surface of the image carrier, a developing device for developing the electrostatic latent image with a developer, and a developer on the surface of the image carrier A transfer device that moves an image to a transfer material is provided, and the developer remaining on the surface of the image carrier without being transferred to the transfer material by the transfer device is temporarily collected by a charging member that contacts the image carrier of the charging device. In the image forming apparatus of the type in which the collected developer is discharged from the charging member and recollected by the developing device, an image ratio detection unit for the image forming area is provided, and charging and exposure are performed during non-image forming according to the detected value. It is characterized by the presence or absence of development operations and conditions .

  According to a second aspect of the present invention, in the first aspect of the present invention, the image ratio detection means divides the thrust direction into a plurality of sections and individually detects the division.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the operation time for charging, image writing, and development during non-image formation is determined based on the detection value of the image ratio detection means. .

  A fourth aspect of the invention is characterized in that, in the invention according to any one of the first to third aspects, the image writing time of each section is determined by the detection value of each section of the image ratio detecting means.

  According to a fifth aspect of the present invention, there is provided an image bearing member, a charging member that contacts the image bearing member, and a charging device that charges the image bearing member by applying a charging bias to the charging member, and the image bearing member. An image information writing device for forming an electrostatic latent image on the charging surface of the body, a developing device for visualizing the electrostatic latent image with a developer, and a developer image on the surface of the image carrier are moved to a transfer material. The developer remaining on the surface of the image carrier without being transferred to the transfer material by the transfer device is temporarily collected by the charging member in contact with the image carrier of the charging device, and the collected developer is In an image forming apparatus of a type that is discharged from a charging member and recollected by a developing device, charging, exposure, and developing operations are performed during non-image formation on an area where the transfer material does not contact the image carrier. Features.

  According to a sixth aspect of the present invention, in the invention according to any one of the first to fifth aspects, the charging device is formed of magnetic particles.

  According to a seventh aspect of the invention, in the invention according to any one of the first to sixth aspects, the image information writing device for forming an electrostatic latent image on the charging surface of the image carrier is an exposure device. To do.

  The invention according to claim 8 is the invention according to any one of claims 1 to 7, wherein the image carrier is an electrophotographic photosensitive member.

  According to a ninth aspect of the invention, in the invention according to any one of the first to eighth aspects, the image carrier is charge injection charging.

  A tenth aspect of the present invention is the electrophotographic photosensitive member according to any one of the first to ninth aspects, wherein the image carrier has a charge injection layer in which conductive fine particles are dispersed in an insulating binder. It is characterized by that.

  According to the present invention, the toner is periodically collected in a charger in the area of the photoreceptor where the image ratio is small, and an external additive having an abrasive effect is mixed in the magnetic particles, thereby causing adhesion or discharge of paper dust or the like. The deteriorated photoreceptor surface is polished and returned to its original state. As a result, it is possible to suppress adhesion of magnetic particles used in the charger to the surface of the photoreceptor, and to prevent damage to the photoreceptor.

<Embodiment 1>
FIG. 1 is a schematic configuration diagram of an electrophotographic image forming apparatus according to the present invention. The image forming apparatus includes a photosensitive drum 1 that rotates in the direction of an arrow. Around the photosensitive drum 1, an image forming unit that includes a charger 2, a transfer discharger 5, a laser beam scanner disposed above the photosensitive drum, and the like. It is configured. A document reading apparatus having a photoelectric conversion element such as a CCD outputs an image signal corresponding to monochrome image information of the document. The semiconductor laser built in the laser beam scanner 3 is controlled according to the image signal and emits a laser beam L. An output signal from the electronic computer can also be printed out.

  In the sequence of the entire image forming apparatus, first, the photosensitive drum is uniformly charged by the charger. The photoreceptor rotates in the clockwise direction indicated by the arrow at a process speed (peripheral speed) of 100 mm / sec.

The photoreceptor used in the present embodiment is a negatively charged OPC photoreceptor, in which the following first to fifth functional layers are provided in order from the bottom on an aluminum drum base of φ30 mm. is there. The first layer is an undercoat layer, and has a thickness of about 4 mm, which is provided for leveling defects on an aluminum drum base (hereinafter referred to as an aluminum base) and preventing the occurrence of moire due to reflection of laser exposure. It is a 20 μm conductive layer. The second layer is a positive charge injection preventing layer, which serves to prevent the positive charge injected from the aluminum substrate from canceling the negative charge charged on the surface of the photoreceptor, and is 10 ⁶ by amylan resin and methoxymethylated nylon. It is a medium resistance layer with a thickness of about 1 μm, the resistance of which is adjusted to about Ω · cm. The third layer is a charge generation layer, which is a layer having a thickness of about 0.3 μm in which a disazo pigment is dispersed in a resin, and generates positive and negative charge pairs upon receiving laser exposure.

The fourth layer is a charge transport layer, which is a P-type semiconductor, in which hydrazone is dispersed in a polycarbonate resin. Accordingly, negative charges charged on the surface of the photoreceptor cannot move through this layer, and only positive charges generated in the charge generation layer can be transported to the surface of the photoreceptor. The fifth layer is a charge injection layer, and is made of tin oxide having a particle size of 0.03 μm, which is made low in resistance (conducting) by doping light-curing acrylic resin as a binder with antimony as a light-transmissive conductive filler. It is a coating layer of about 3 μm made of a material in which ultrafine particles are dispersed by 70 weight percent with respect to the resin. The electric resistance value of this electrification injection layer needs to be 1 × 10 ¹⁰ to 1 × 10 ¹⁴ Ω · cm, which is a sufficient charging property and does not cause image flow. In this embodiment, a photosensitive drum having a surface resistance of 1 × 10 ¹¹ Ω · cm is used.

  Next, scanning exposure is performed by the laser light L modulated by the image signal, an electrostatic latent image is formed on the photosensitive drum 1, and this electrostatic latent image is reversely developed by the developing device 4. In the present embodiment, a two-component contact development method using a developer in which a highly separated spherical non-magnetic toner with a small amount of transfer residual toner prepared by a polymerization method and a magnetic carrier is used is discharged from an injection charger. Toner recovery is improved. The development characteristics of this embodiment are that fogging occurs when the difference between the DC component value of the charging potential and the developing bias is 200 V or less, and that the developing carrier adheres to the photosensitive member when it is 350 V or more. The DC component value was −400V.

  The toner image on the photosensitive drum is taken out from the paper feed cassette 6 and transferred to a transfer material P such as paper that has advanced via a paper feed roller and a paper feed guide by a transfer charger (transfer belt and conductive blade) 5. Transcribed. In the present embodiment, transfer was performed with constant current control of 10 μA. The transfer charger may use a charging roller. Further, it is also possible to adopt a configuration in which the image is not directly transferred to the transfer material, but is transferred to the intermediate transfer body and then transferred to the transfer material in a lump.

  The toner that is not transferred and remains on the surface of the photosensitive drum 1 is applied with a positive DC voltage and passes through the conductive brush 12 that is in contact with the photosensitive member, whereby the negative toner is collected in the conductive brush. The positive toner passes and is temporarily collected by the injection charger 2. The toner collected on the conductive brush is discharged or charged on the positive electrode and comes out again on the photoreceptor.

As the conductive brush, a brush length of 1 to 10 mm, a brush density of 1 to 500,000 / inch ² , a brush diameter of 2 to 12 denier, and a brush resistance of 10 ⁻² to 10 ¹² Ω · cm are preferable. In this embodiment, A brush having a brush length of 5 mm, a brush density of 100,000 / inch ² , a brush diameter of 6 denier, and a brush resistance of 10 ⁵ Ω · cm was used.

  The applied bias is preferably 200V to 1500V, more preferably 400V to 800V. If it is less than that, it will be difficult to prevent ghosting due to the charge removal and charging effect of the negative transfer residual toner, and if it is more than that, it will give a strong positive charge to the photoconductor. It becomes easy to cause a defect. In this embodiment, a DC bias of 500V is used.

  On the other hand, the transfer material onto which the toner has been transferred is separated from the belt and then sent to a fixing device (heat roller fixing device) 11 to fix the image.

  Next, the charger used in the present invention will be described with reference to FIG.

  The charger 2 includes a container 21, a sleeve 23 made of a nonmagnetic material having a fixed magnet 22 inside, a magnetic particle 24 that injects a charge in contact with the photosensitive member, and a uniform thickness of the magnetic particle on the sleeve surface. Further, it is composed of a regulation blade 25 that coats it.

  The non-magnetic stainless steel sleeve 12 rotates in the same clockwise direction as the photosensitive drum 1. The regulation blade 24 made of non-magnetic stainless steel is arranged so that the gap with the sleeve surface is 900 μm.

  The magnet fixedly arranged in the sleeve has a magnetic pole (main pole) of about 900 G arranged at 10 ° upstream of the photosensitive drum rotating direction from the closest position of the sleeve and the photosensitive drum. It is desirable for this main pole to have an angle (θ in the figure) with the closest position within the range of 20 ° upstream to 10 ° downstream of the photosensitive drum rotation direction (more preferably 15 ° to 0 ° upstream). ). If it is downstream, the magnetic particles are attracted to the main pole position, and magnetic particles are likely to stay on the downstream side of the charging nip in the photosensitive drum rotation direction. If it is too upstream, the magnetic particles that have passed through the charging nip are transported. The property becomes worse and retention is likely to occur. In addition, when there is no magnetic pole in the charging nip portion, it is clear that the binding force acting on the sleeve acting on the magnetic particles becomes weak and the magnetic particles are likely to adhere to the photosensitive drum. The charging nip described here indicates a region where the magnetic particles are in contact with the photosensitive drum during charging.

  The charging bias is applied to the sleeve and the regulating blade. DC was set to the same value as the required surface potential of the photosensitive drum (in this embodiment, −700 V). The AC peak-to-peak voltage (hereinafter Vpp) is preferably 100 V or more and 2000 V or less, particularly 300 V or more and 1200 V or less. Below Vpp, the effect of improving charging uniformity and potential rise is small, and above that, the retention of magnetic particles and adhesion to the photosensitive drum deteriorate.

  The frequency is preferably 100 Hz to 5000 Hz, particularly preferably 500 Hz to 2000 Hz. Below that, the effect of improving the adhesion of magnetic particles to the photosensitive drum and improving the charging uniformity and potential rise properties become diminished, and the effect of improving the charging uniformity and potential rise properties becomes difficult to obtain even more. The AC waveform is preferably a rectangular wave, a triangular wave, a sin wave, or the like. In the present embodiment, charging is performed at 700 Vpp at the time of image formation, 0 Vpp at the time of non-image formation, that is, only DC (−700 V) is charged.

In this embodiment, magnetic particles obtained by reducing sintered ferromagnetic material (ferrite) are used. Alternatively, resin and ferromagnetic powder are kneaded and formed into particles, or this. In addition, those obtained by mixing conductive carbon or the like for adjusting the resistance value, or those subjected to surface treatment can be used in the same manner. These magnetic particles have a role of injecting charges well into the trap level on the surface of the photosensitive member, and charging members and photosensitive members generated due to concentration of charging currents on defects such as pinholes generated on the photosensitive member. It must also have the role of preventing the body from being energized. Accordingly, the resistance value of the charging member is preferably ^{1 × 10 4 Ω~1 × 10 9} Ω, and particularly preferably from ^{1 × 10 4 Ω~1 × 10 7} Ω. If the resistance value of the charging member is less than 1 × 10 ⁴ Ω, pinhole leakage tends to occur, and if it exceeds 1 × 10 ⁹ Ω, good charge injection tends to be difficult. In order to control the resistance value within the above range, the volume resistance value of the magnetic particles of the present invention is preferably 1 × 10 ⁴ Ω · cm to 1 × 10 ⁹ Ω · cm, particularly 1 ×. It is preferably 10 ⁴ Ω · cm to 1 × 10 ⁷ Ω · cm.

The volume resistance value of the magnetic particles was measured using the cell shown in FIG. That is, it was obtained by filling the cell A with magnetic particles, arranging the electrodes 31 and 32 so as to be in contact with the filled magnetic particles, applying a voltage between the electrodes, and measuring the current flowing at that time. The measurement conditions are a contact area S = 2 cm ² with a filled magnetic particle cell in an environment of 23 ° C. and 65%, a thickness d = 1 mm, an upper electrode load of 10 kg, and an applied voltage of 100V. In FIG. 3, 31 is a main electrode, 32 is an upper electrode, 33 is an insulator, 34 is an ammeter, 35 is a voltmeter, 36 is a constant voltage device, 37 is a magnetic particle, and 38 is a guide ring.

  The average particle diameter and the peak in the particle size distribution measurement of the magnetic particles of the present invention are preferably in the range of 5 to 100 μm from the viewpoint of preventing charging deterioration due to contamination of the particle surface.

The resistance value of the charging member used in this embodiment is 1 × 10 ⁶ Ω · cm, and by applying −700 V as the DC component of the charging bias, the surface potential of the photosensitive drum is also −700 V.

  In the image forming apparatus described above, a horizontal band corresponding to an image ratio of 1, 2 or 3% (a band image in the entire thrust direction) is formed on the A4 transfer material, and the amount of magnetic particles adhering to the photosensitive member at that time is determined. It was measured. The result is shown in FIG. When the image ratio is 2% or more, the adhesion amount of magnetic particles does not increase rapidly during image formation of up to 3000 sheets. However, if it is less than 2%, the adhesion amount of magnetic particles rapidly increases at about 1500 sheets. This is because the transfer residual toner is taken into the magnetic brush, and the silica particles, which are a kind of external additive contained in the toner, polish the surface of the photoreceptor, and the paper additive adheres when the paper or the like comes into contact with it. This is because the surface of the photoreceptor is restored.

  Even in the general image creation, even if the average image ratio is 2% or more, the image ratio is locally low due to a margin or the like at the edge of the image. As a result, the magnetic particles easily adhere to the photoconductor at the edge of the image, and the photoconductor is scratched to form a potty image.

  Therefore, in the present embodiment, the image ratio is integrated in the thrust direction, and toner is developed in a low-ratio area during non-image formation and transferred directly to the charger without being transferred, thereby suppressing the occurrence of photoconductor scratches. .

  In this embodiment, the image ratio is integrated (A4 conversion) from every video count integrated value every 100 sheets and the image ratio is compared with 200% (for 100 sheets of 2% images at A4), and less than 200%. Only in the section, the horizontal band was imaged between the papers or after rotation and was collected by the charger.

  The partition width in the longitudinal direction of the video count was 20 mm.

  The width of the horizontal band was calculated by the following formula.

The amount of toner per unit area on the photoreceptor after development is M (mg / cm ² ).
Transfer efficiency is T (%)
The area of A4 paper is S (cm ² )
Then, the transfer residual A for 100 A4 size 2% images is
A = 2 × 100 × S × 1/100 × M × (100−T) / 100
= 2SM (100-T) / 100
The toner amount B contained in 1% of the horizontal band is
1/100 x S x M
It is.

Therefore, the width of the horizontal band derived from the toner amount corresponding to the difference X (%) between the image ratio of 100 sheets calculated from the video count and 200% is:
2 (100-T) ・ (200-X) /200×2.1mm
It becomes.

  Under this condition, the horizontal belt is imaged and collected by the charger, and then the photoconductor and the charger are rotated for about 20 seconds. As a result, the surface of the photoconductor can be polished even in a thrust region where the image ratio is small. The adhesion of magnetic particles could be prevented.

<Embodiment 2>
In this embodiment, when 5000 sheets of A4 vertical feed (thrust direction width 210 mm) are passed through an image forming apparatus having a maximum sheet passing width of 305 mm, the non-sheet passing portion of the photoconductor is damaged, and thereafter A3 When paper such as paper was passed through, a pop was generated.

  Therefore, as derived from the first embodiment, a horizontal band of 2 (100-T) × 2.1 mm was formed between papers or after rotation for every 100 sheets of A4 vertical feeding. As a result, the photoconductor was not damaged even after the image formation of 5000 sheets, and good image formation was possible even with image formation on a wide paper after that.

  The present invention relates to an electrophotographic system / electrostatic recording that performs image formation by applying an image forming process including a step of charging a charge member to which an image carrier is applied by applying a voltage to the image carrier. The present invention can be applied to an image forming apparatus such as a copying machine or printer of the type.

1 is a configuration diagram of an electrophotographic image forming apparatus according to the present invention. It is a block diagram of a charging device. It is a figure which shows the measuring method of the electrical resistance of the magnetic particle in this invention. It is a figure which shows the adhesion amount of a magnetic particle when image formation is performed with a fixed image ratio.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging device 3 Laser beam scanner 5 Charging device 6 Paper feed cassette 11 Fixing device 12 Sleeve 24 Regulating blade L Laser beam P Transfer material

Claims (10)

An image carrier, a charging device having a charging member in contact with the image carrier, and charging the image carrier by applying a charging bias to the charging member; and an electrostatic treatment on the charge processing surface of the image carrier. An image information writing device for forming a latent image, a developing device for developing the electrostatic latent image with a developer, and a transfer device for moving the developer image on the surface of the image carrier to a transfer material. The developer remaining on the surface of the image carrier without moving to the transfer material by the apparatus is temporarily collected by the charging member that contacts the image carrier of the charging device, and the collected developer is discharged from the charging member to develop the developing device. In the image forming apparatus of the method of recollecting in
An image forming apparatus comprising: an image ratio detection unit for an image forming region; and the presence / absence and conditions of charging, exposure, and development operations are determined during non-image formation based on the detection value.   The image forming apparatus according to claim 1, wherein the image ratio detection unit divides the thrust direction into a plurality of sections and individually detects the division.   3. The image forming apparatus according to claim 1, wherein the operation time of charging, image writing, and development at the time of non-image formation is determined based on a detection value of the image ratio detection unit.   The image forming apparatus according to claim 1, wherein an image writing time for each section is determined based on a detection value of each section of the image ratio detection unit. An image carrier, a charging device having a charging member in contact with the image carrier, and charging the image carrier by applying a charging bias to the charging member; and an electrostatic treatment on the charge processing surface of the image carrier. An image information writing device for forming a latent image, a developing device for developing the electrostatic latent image with a developer, and a transfer device for moving the developer image on the surface of the image carrier to a transfer material. The developer remaining on the surface of the image carrier without moving to the transfer material by the apparatus is temporarily collected by the charging member that contacts the image carrier of the charging device, and the collected developer is discharged from the charging member to develop the developing device. In the image forming apparatus of the method of recollecting in
An image forming apparatus, wherein charging, exposure, and development operations are performed during non-image formation on an area where a transfer material does not contact an image carrier.   The image forming apparatus according to claim 1, wherein the charging device is formed of magnetic particles.   7. The image forming apparatus according to claim 1, wherein the image information writing device for forming an electrostatic latent image on the charging surface of the image carrier is an exposure device.   8. The image forming apparatus according to claim 1, wherein the image bearing member is an electrophotographic photosensitive member.   The image forming apparatus according to claim 1, wherein the image carrier is charge injection chargeable.   10. The image forming apparatus according to claim 1, wherein the image bearing member is an electrophotographic photosensitive member having a charge injection layer in which conductive fine particles are dispersed in an insulating binder.

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