JP2011007916A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus which stably forms a high-quality image by preventing the deterioration of image quality such as the crack of a tip of an image and suction from being caused.SOLUTION: An amount of a toner on an electrode in which the rearrangement of the toner for suppressing the crack of the tip of the image and the suction or the like is performed is detected by a toner sensor. Based on the result of detection, toner application to apply the toner to the electrode is performed.

Description

  The present invention relates to an image forming apparatus for forming an image on a recording material by an electrophotographic process.

  In the electrophotographic process, as is well known, an electrostatic latent image is formed on an image carrier, and the formed electrostatic latent image is developed to form a toner image. The formed toner image is transferred to a recording material such as paper.

  Higher image quality has progressed, and in particular, as a result of higher quality of color images, photographic images and pattern images can be expressed more precisely.

  However, when improving the image quality of a surface image such as a photographic image or a pattern image, particularly the image quality in the intermediate density portion of the surface image, there is a problem of image roughness that occurs in magnetic brush development.

  In Patent Documents 1 and 2, in order to suppress the image roughness, an electrode is disposed on the downstream side of the developing device so as to face the image carrier, and an alternating voltage is applied to the electrode, whereby the toner is carried on the image carrier. It has been proposed to reciprocate between the body and the electrodes.

  The image roughness is considered to be caused by non-uniform toner distribution in a portion where the density should be uniform. However, in Patent Documents 1 and 2, the toner distribution is made uniform by reciprocating the toner. Sag is suppressed.

JP-A-4-372964 JP-A-6-274040

  When a surface image such as a photographic image or a pattern image is developed by magnetic brush development, the density decreases and an insufficient density portion occurs at the edge of the surface image or at the boundary between the high density portion and the low density portion. There's a problem.

  In Patent Documents 1 and 2, the toner that forms the toner image is vibrated to prevent rattling and improve the image quality. Although this technique is to redistribute the toner adhering to the image carrier by development by virtue of the action of an alternating electric field, the toner is leveled and prevents rattling. It is not enough to correct.

  An object of the present invention is to provide an image forming apparatus capable of preventing a decrease in density at an image edge and stably forming a high-quality image.

  The object is achieved by the following invention.

1. An image carrier;
A latent image forming apparatus for forming an electrostatic latent image on the image carrier;
A developing device that develops an electrostatic latent image carried on the image carrier and forms a toner image on the image carrier;
An electrode located on the downstream side in the moving direction of the image carrier with respect to the developing device and disposed opposite the image carrier;
A power supply for applying at least an alternating voltage to the electrodes;
In an image forming apparatus comprising:
A toner applying unit for applying toner to the electrode;
A toner sensor for detecting toner on the electrode;
An image forming apparatus comprising: a control unit that controls the toner applying unit based on a detection result of the toner sensor to execute a toner applying process.

2. The toner applying unit includes the developing device and the image carrier.
2. The image forming apparatus according to item 1, wherein the toner in the developing device is moved to the image carrier, and the toner on the image carrier is moved to the electrode.

  3. The control unit executes the toner applying step of causing the electrode to carry toner when the toner sensor detects that the amount of toner on the electrode has become a predetermined value or less. Alternatively, the image forming apparatus described in 2 above.

  4). The control unit creates a profile of a toner layer on the electrode based on a detection result of the toner sensor, and executes the toner applying step based on the profile. The image forming apparatus according to claim 1.

  5. 5. The image forming apparatus according to claim 1, wherein the control unit executes an electrode condition adjusting step of adjusting an output of the power source in the image forming step.

  6). The electrode condition adjusting step includes: a toner discharging step for removing toner on the electrode; a step of applying toner on the electrode; a step of detecting the amount of toner on the electrode by the toner sensor; and a detection result And the step of setting the output of the power supply on the basis of the image forming apparatus.

  7. A temperature sensor, a humidity sensor, a coverage information generation unit, a number counter, and an information generation unit including at least one stop time information generation unit, and the control unit performs the electrode condition adjustment step. 7. The image forming apparatus as described in 5 or 6 above, wherein whether or not to execute is determined based on information from the information generation unit.

  In the present invention, the toner on the electrode on which the toner forming the toner image on the image carrier is rearranged is detected by the toner sensor, and the toner applying unit for applying the toner to the electrode based on the detection result is provided. I have control. Therefore, the electrode always carries an appropriate amount of toner, and toner rearrangement by the electrode is effectively performed. As a result, a decrease in density at the edge of the image or at the boundary between the high density part and the low density part is prevented, and a high-quality image is stably formed.

1 is a diagram illustrating an overall configuration of an image forming apparatus according to an embodiment of the present invention. It is a figure for demonstrating a chip | tip chip | tip and suction | inhalation. 2 is a block diagram of a control system of the image forming apparatus according to the embodiment of the present invention. FIG. 2 is a diagram illustrating a configuration of a toner sensor 21. FIG. 3 is a graph showing the output of a toner sensor 21. It is a figure which shows a toner provision process. 4 is a flowchart of control for applying toner to the toner rearrangement electrode 10 according to the first embodiment of the present invention. 4 is a flowchart of an electrode condition adjustment process for optimizing the electrode conditions of the toner rearrangement electrode 10. It is a flowchart of control in Embodiment 2 of the present invention. It is a figure for demonstrating the toner provision process in Embodiment 2 of this invention. In an Example, it is a figure which shows the pattern used for image quality evaluation.

  FIG. 1 is a diagram showing an overall configuration of an image forming apparatus according to an embodiment of the present invention.

  A photoconductor 1 as an image carrier for carrying an electrostatic latent image and a toner image is made of an OPC photoconductor, and has an organic photosensitive layer formed on a conductive drum base on the surface.

  Reference numeral 2 denotes a charging device composed of a scorotron charger, and 3 denotes an exposure device using a laser, a light emitting diode array or the like as a light source, and emits light based on image data to expose the photosensitive member 1. The charging device 2 and the exposure device 3 constitute a latent image forming device that forms an electrostatic latent image on the photoreceptor 1.

  A developing device 4 forms a magnetic brush with a two-component developer containing toner and a magnetic carrier and performs reversal development. Reference numeral 4A denotes a developing roller as a developer carrying member that conveys the developer to the developing area and supports the magnetic brush of the developer in the developing area.

  Reference numeral 4B denotes a magnet roll as a magnetic field forming unit having a plurality of magnetic poles such as a developing magnetic pole and a developer conveying magnetic pole, and is fixedly disposed in the developing roller 4A.

  A developing bias in which an alternating voltage is superimposed on a DC voltage is applied to the developing roller 4A.

  The developing roller 4A rotates to convey the developer to the developing area. In the developing region where the photoreceptor 1 and the developing roller 4A face each other, a magnetic brush is formed by the developing magnetic pole of the magnet roller 4B, and the ears of the magnetic brush come into contact with the photoreceptor 1, and contact development is performed. In the illustrated example, the developing roller 4A moves in the direction opposite to the photosensitive member 1 in the developing region, but a developing method in which the developing roller 4A is moved in the same direction as the photosensitive member 1 may be employed.

  The former development method is called a reverse rotation development method, and the latter development method is called a forward rotation development method.

  In the illustrated developing device 4, reverse development is performed in which a negatively charged toner is used to develop an electrostatic latent image having a negative charge.

  A transfer device 5 includes a roller 5A, and a transfer voltage having a polarity opposite to that of the toner is applied to the roller 5A. Reference numeral 6 denotes a cleaning device that cleans the photoreceptor 1, and 7 denotes a fixing device that heats and fixes the toner image. The photosensitive member 1 rotates clockwise as indicated by an arrow, and an electrostatic latent image is formed on the photosensitive member 1 by charging by the charging device 2 and exposure by the exposure device 3. In the embodiment, the photosensitive member 1 is negatively charged, and a latent electrostatic image composed of negative charges is formed on the photosensitive member 1. In the developing device 4, the latent image is developed with negatively charged toner. The toner image formed on the photoreceptor 1 by development is transferred to the recording material P by the transfer device 5.

  The toner image on the recording material P is heated and fixed by the fixing device 7. The transferred photoreceptor 1 is cleaned by a cleaning device 6.

  An electrode 10 is disposed downstream of the developing device 4 with respect to the moving direction of the photoreceptor 1. A voltage in which a DC voltage is superimposed on an alternating voltage is applied to the electrode 10 by a power source 10A made of an AC power source and a power source 10B made of a DC power source.

  The electrode 10, the power source 10 </ b> A, and the power source 10 </ b> B constitute a toner rearrangement unit that rearranges the toner constituting the toner image formed on the photoreceptor 1. Hereinafter, the electrode 10 is referred to as a toner rearrangement electrode.

  As will be described below, the toner rearrangement unit suppresses chipping, suction, and the like, and prevents deterioration in image quality due to these.

  These image quality degradations will be described with reference to FIG. These deteriorations in image quality do not occur in line images such as character images, but occur in the case of plane images such as photographic images and pattern images.

  FIG. 2 shows a toner image developed by performing image writing using test pattern image data in which low density portions are arranged at both ends of a central high density portion.

  2A shows a correct image, that is, an image in which the density of the image data is faithfully reproduced, FIG. 2B shows a toner image in which the leading edge is missing, and FIG. 2C shows suction. The toner image is shown. In the downstream part of the development area (downstream part with respect to the moving direction of the photoreceptor 1), a phenomenon occurs in which the toner image formed on the photoreceptor 1 is rubbed by the magnetic brush. The toner image moves due to this rubbing. As a result, a toner deficient portion is formed at the tip portion Ta of the toner image, and the density of the tip portion Ta of the toner image is lowered. It is considered that the chipping shown in FIG. 2 (b) occurs by such a mechanism.

  In addition, at the boundary between the high density portion and the low density portion, the toner forming the low density portion is attracted to the electric field formed by the high density electrostatic latent image and counters the carrier that has lost the toner by development. Charge is generated and attracted by the counter charge, and the toner moves from the low density portion to the high density portion. As a result, the density of the boundary Tb when the low density part and the high density part are adjacent to each other is lowered. The suction shown in FIG. 2C is considered to occur by such a mechanism.

  In FIG. 2, the chipping at the tip and the suction are shown to occur in different patterns. However, in actuality, there may be cases where both of these density deficiencies occur in one pattern.

  The arrow indicates the relative movement direction of the magnetic brush with respect to the photoreceptor 1. When viewed from the photoreceptor 1 as a reference, in the reverse rotation developing method, the leading edge chipping occurs at the leading edge portion of the image, and the suction occurs at the leading edge portion of the low density portion adjacent to the high density portion. On the other hand, in the positive rotation developing method, the moving speed of the developing roller 4A is higher than that of the photosensitive member 1, so that the leading edge chipping occurs at the rear end portion of the image, and the suction is performed in the low density portion adjacent to the high density portion. Occurs at the rear end.

  Tip chipping and suction are corrected by toner rearrangement at the toner rearrangement unit electrode 10.

  That is, when a toner image having a chipped portion or a suction end passes through the toner rearrangement electrode 10, the alternating electric field formed between the photosensitive member 1 and the toner rearrangement electrode 10 causes the toner to move between the photoreceptor 1 and the toner rearrangement electrode 10. Reciprocates between. In the portion where the tip is missing or sucked, there is a potential well due to an undeveloped or underdeveloped electrostatic latent image, so toner is replenished to the potential well from the toner rearrangement electrode 10 and the density is insufficient. Is corrected.

  FIG. 3 is a block diagram of a control system of the image forming apparatus according to the embodiment of the present invention, and FIG. 4 shows a configuration of the toner sensor 21 that detects toner on the toner rearrangement electrode 10.

  The toner sensor 21 includes a light emitting element 21 a that is an LED that emits light toward the toner rearrangement electrode 10, and a light receiving element 21 b that is a photodiode that receives reflected light from the toner rearrangement electrode 10. As the cylindrical toner rearrangement electrode 10 rotates as indicated by an arrow, the amount of toner on the toner rearrangement electrode 10 is optically continuously detected.

FIG. 5 shows the output of the toner sensor 21. As shown, the output of the toner sensor 21 decreases as the toner amount (g / m ² ) increases. In FIG. 5, the output of the toner sensor 21 between SV1 and SV2 indicates an appropriate toner amount range.

  In FIG. 3, 20 is a control unit for controlling the entire image forming apparatus, 22 is a temperature sensor for detecting the temperature in the image forming apparatus, 23 is a humidity sensor for detecting the humidity in the image forming apparatus, and 24 is for storing image data. An image data storage unit 25, a sheet number counter 25 for counting the number of images to be formed, a timer 26, and a drive unit 27 for driving the photosensitive member 1, the developing roller 4A, and the like.

  FIG. 6 shows a toner application process for applying toner onto the toner rearrangement electrode 10. A sufficient amount of toner is carried on the toner rearrangement electrode 10 by the toner application step shown in FIG.

  In FIG. 6A, the charging device 2 charges the photoconductor 1 to form a potential V0 on the photoconductor 1. By uniformly exposing the charged photosensitive member 1 with the exposure device 3, the potential on the photosensitive member 1 is lowered to V1 (FIG. 6B), and developing with the developing device 4, the toner T layer Is formed on the photosensitive member 1 (FIG. 6C).

  By applying a DC voltage and an AC voltage between the photoreceptor 1 and the toner rearrangement electrode 10, with the photoreceptor 1 side negative and the toner rearrangement electrode 10 side positive, the toner T on the photoreceptor 1 moves. Then, as shown in FIG. 6D, the toner moves onto the toner rearrangement electrode 10, and a uniform toner image is formed on the toner rearrangement electrode 10. In the toner application process of FIG. 6, a DC voltage is applied to the developing roller 4 </ b> A and the toner rearrangement electrode 10 so that a predetermined amount of toner layer is formed on the toner rearrangement electrode 10.

  Thus, the toner application step is performed by moving the toner from the developing device 4 onto the photoreceptor 1 and moving the toner from the photoreceptor 1 to the toner rearrangement electrode 10. The photoconductor 1 and the developing device 4 constitute a toner applying unit, and the control unit 20 controls the rotation of the photoconductor 1 and the developing roller 4A under the control of the driving unit 27 and develops a developing bias for performing solid development on the developing roller 4A. The toner is applied to the toner rearrangement electrode 10 by performing control such as application. In the example shown in FIG. 6, the toner application step, that is, the toner application in which the photoreceptor 1, the charging device 2, the exposure device 3, the development device 4, and the power supplies 10 </ b> A and 10 </ b> B apply toner to the toner rearrangement electrode 10. The control 20 controls at least a part of these to apply toner to the toner rearrangement electrode 10.

In the illustrated example, the photosensitive member 1 is charged, exposed, and developed to form a toner layer on the photosensitive member 1, but conditions for moving toner from the developing device 4 are created on the photosensitive member 1. Control may be performed, and charging and exposure are not essential in the toner application step.
<Embodiment 1>
FIG. 7 is a flowchart of control for applying toner to the toner rearrangement electrode 10 according to the first embodiment of the present invention. The toner application control process of FIG. 7 is performed at a predetermined interval or a predetermined interval, such as at the start of the image forming process, every time a predetermined number of images are formed at an interval that does not affect the images, such as between images. Implemented at the time.

  In step ST1, the toner amount on the toner rearrangement electrode 10 is detected by the toner sensor 21, and in step ST2, it is determined whether or not the toner amount on the toner rearrangement electrode 10 is sufficient. For example, when the output of the toner sensor 21 is less than 3.0 V (No in ST2), it is determined that the amount of toner is sufficient, and the process proceeds to a printing operation, that is, image formation (ST6).

  When the output of the toner sensor 21 is 3.0 V or higher (Yes in ST2), Step ST3, which is a toner application process for applying toner to the toner rearrangement electrode 10, is executed. In step ST3, the toner application process described above with reference to FIG. 6 is executed.

  In step ST4, the toner amount on the toner rearrangement electrode 10 is detected by the toner sensor 21, and when the sensor output is less than 2.0V (No in ST5), the toner amount is sufficient, and the process proceeds to the image forming process. (ST6). When the sensor output is 2.0 V or more (Yes in ST5), the process proceeds to step ST3 to execute the toner application step.

  Through the toner application control process shown in FIG. 7, a uniform and sufficient amount of toner is always carried on the toner rearrangement electrode 10. Therefore, in the image forming process, the toner rearrangement by the toner rearrangement electrode 10 is always sufficiently performed. As a result, the roughness is sufficiently suppressed, chipping and suction are sufficiently prevented, and a high-quality image is stably formed.

  As is apparent from the figure, in step ST6, image formation is performed in a state where a sufficient amount of toner is present on the toner rearrangement electrode 10. In image formation, toner rearrangement is performed when the toner image formed on the photoreceptor 1 by development of the developing device 4 passes through the position of the toner rearrangement electrode 10. In the toner rearrangement, since a sufficient amount of toner exists on the toner rearrangement electrode 10, the toner is replenished from the toner rearrangement electrode 10 to a portion where the toner is insufficient due to chipping or suction. . As a result, the insufficient density is corrected, and a toner image is formed with the desired density.

  In the toner rearrangement in which the toner forming the toner image on the photoconductor 1 is rearranged, at least an alternating electric field is formed between the photoconductor 1 and the toner rearrangement electrode 10 as described above. Thus, the toner is reciprocated between the photosensitive member 1 and the toner rearrangement electrode 10.

  The electrode conditions of the toner rearrangement electrode 10 in the toner rearrangement are preferably set to optimum values corresponding to various conditions. By adjusting such an optimum value, the above-described correction of insufficient density at the leading edge and the trailing edge of the high density portion is sufficiently performed, and an image with a more uniform density can be formed. Become.

  FIG. 8 is a flowchart of an example of an electrode condition adjusting process for optimizing the electrode conditions of the toner rearrangement electrode 10. The electrode condition adjusted in FIG. 8 is the amplitude of the alternating voltage, but it is also possible to adjust the frequency of the alternating voltage and the DC voltage together.

  In step ST10, information is taken in. The captured information includes at least one of the in-machine temperature, the in-machine humidity, the coverage, the number of printed sheets, and the stop time.

  These pieces of information are acquired from the temperature sensor 22 that generates the in-machine temperature information, the humidity sensor 23 that generates the in-machine humidity information, the image data storage unit 24, the number counter 25, and the timer 26 in FIG. Note that coverage is obtained from the image data storage unit 24 and the number counter 25 as a coverage information generation unit, and information on the amount of image data and information on the number of images, and the amount of image data is calculated as the number of sheets formed. It is obtained by dividing by the image area calculated from the size information. The number of printed sheets is obtained from the number counter 25. The stop time is information on the length of time that the image forming apparatus is stopped when the toner application control step of FIG. 7 is executed after the image forming apparatus is stopped, and a timer as a stop time information generation unit 26.

  In step ST11 subsequent to step ST10, the criteria for determination in step ST11 in which it is determined whether or not a condition change in toner rearrangement is necessary are determined in advance by experiment, and the various conditions such as the in-machine temperature condition are determined. When it changes beyond a predetermined range, it is determined that it is necessary to change the electrode conditions.

  If no change is required (No in ST11), the toner application process shown in FIG. 6 is executed (ST20), and then the process proceeds to the image forming process (ST21). In the image forming process of ST21, which is determined to be unnecessary in ST11, toner relocation is performed under the electrode conditions in the previous image forming process, that is, the image forming process before entering the electrode condition adjusting process in FIG. Is called.

  If the determination in step ST11 is Yes, toner ejection is performed in step ST12. Toner ejection is a toner removal step for preventing toner from being present in the toner rearrangement electrode 10, and a high DC voltage and an alternating voltage are applied to the toner rearrangement electrode 10 on the negative side of the photoreceptor 1 by the power supplies 10 </ b> A and 10 </ b> B. Then, the toner on the toner rearrangement electrode 10 is discharged to the photoreceptor 1.

  In step ST13 following step ST12, the voltage of the toner rearrangement electrode 10, that is, the output of the power supplies 10A and 10B is set to a predetermined initial value. The initial value is determined in advance and is a voltage for forming an intermediate density toner layer on the toner rearrangement electrode 10. In step ST13, the DC voltage of the developing roller 4A is set so as to form an intermediate density toner layer on the photoreceptor 1. As described above, in ST13, a toner layer having an intermediate density is formed on the toner rearrangement electrode 10, and this makes it possible to finely adjust the electrode conditions of the toner rearrangement electrode 10.

  Next, in step ST14, the toner amount on the toner rearrangement electrode 10 is detected by the toner sensor 21. If the sensor output SV is equal to or greater than a predetermined value (the toner amount is equal to or less than the predetermined value) (Yes in ST15), the process proceeds to the toner application process in ST20, and if the sensor output is less than the predetermined value (the toner amount exceeds the predetermined value). (No in ST15), toner discharge is executed in step ST16. The toner ejection in step ST16 is the same as in step ST12.

  In step ST17 following step ST16, the voltage of the toner rearrangement electrode 10 is changed. In the illustrated example, the AC voltage is a value obtained by reducing the value Vac (n) in step ST13 by 5% without changing the DC voltage, that is, Vac (n + 1) = Vac (n) × (1-0.05). Set to The adjustment of ST16 adjusts the amount of reciprocation of the toner in the toner rearrangement.

  In step ST <b> 18, the toner sensor 21 detects the toner amount on the adjusted toner rearrangement electrode 10. If the toner amount is within the predetermined value (Yes in ST19), the process proceeds to the toner application step ST20. If the toner amount exceeds the predetermined value and the toner amount is not sufficient (No in ST19), the process proceeds to step ST16. In the image forming process of ST21 that is executed after the determination in ST19 is Yes, toner rearrangement is performed under the electrode conditions adjusted in ST17.

  By repeating the loop of ST16 to ST19, the process is completed when the optimum amount of toner is applied onto the toner rearrangement electrode 10, and the process proceeds to the toner application process ST20.

  Table 1 shows the electrode conditions of the toner rearrangement electrode 10 in the image forming step, the toner application step in FIG. 6, and the toner rearrangement electrode condition adjustment step (FIG. 8), that is, in the AC power source 10A and the DC power source 10B. An example of voltage is shown. The charging potential of the photosensitive member is −700V, and the DC potential of the developing roller 4A is −500V.

  As shown in Table 1, the toner rearrangement electrode 10 is substantially equal to the potential of the developing roller 4A in the image forming process, and the toner only vibrates between the photoreceptor 1 and the toner rearrangement electrode 10, On the other hand, the toner hardly moves. This is because there is no transfer of toner from the toner rearrangement electrode 10 to the photoconductor 1 in the portion where the potential well on the photoconductor 1 is filled with toner, and the potential well on the photoconductor 1 is not filled. In the portion, the toner is transferred from the toner rearrangement electrode 10 to the photoreceptor 1.

In the toner discharging step, the DC voltage of the toner rearrangement electrode 10 is −1000V. As a result, the toner on the toner rearrangement electrode 10 moves to the photoreceptor 1 side, and the toner on the toner rearrangement electrode 10 is removed. In the toner application step, the toner rearrangement electrode 10 is −200 V, the toner on the photoreceptor 1 moves to the toner rearrangement electrode 10, and the toner is applied to the toner rearrangement electrode 10.
<Embodiment 2>
In the toner application step, the toner moves from the developing device 4 to the photoconductor 1 by development, and further, the toner moves from the photoconductor 1 to the toner rearrangement electrode 10. As a result, a certain amount of toner is carried on the toner rearrangement electrode 10.

  However, the toner amount is reduced in the portion of the toner rearrangement electrode 10 where the toner is replenished from the toner rearrangement electrode 10 to the photosensitive member 1, and the toner replenishment occurs in the next cycle in the reduced portion. As a result, the density correction effect by the toner rearrangement electrode 10 may be reduced and image quality may be reduced.

  Embodiment 2 of the present invention prevents such image quality deterioration.

  FIG. 9 is a flowchart of control in Embodiment 2 of the present invention.

  In step ST30, the toner amount is detected, and in step ST31, it is determined whether or not the toner amount on the toner rearrangement electrode 10 is sufficient based on the output SV of the toner sensor 21. If the output SV is less than 3.0 V and the toner amount is sufficient (No in ST31), the process proceeds to the image forming process ST35. The determination of ST31 is made based on, for example, the average value of the toner amount for one week on the peripheral surface of the toner rearrangement electrode 10.

  When the output is 3.0 V or more and the toner amount is insufficient (Yes in ST31), a profile of the toner layer on the toner rearrangement electrode 10 is created in step ST32.

  This profile is a profile for one round of the toner layer along the rotation direction of the toner rearrangement electrode 10, and is created by the control unit 20 based on the output of the toner sensor 21. An example is shown in FIG. As shown in the drawing, the amount of toner on the toner rearrangement electrode 10 is not uniform, and a portion with a small amount of toner is formed in the portion where the toner has moved to the photoreceptor 1. FIG. 10A shows the toner amount by the sensor output, and the insufficient portion of the toner amount is expressed as a mountain.

  In step ST33, a toner application condition setting for replenishing the partially deficient toner shown in FIG. 10A is performed. In this toner application, the toner is applied to the toner rearrangement electrode 10 by changing the image forming conditions with time. The image forming conditions to be changed include the exposure conditions in the exposure device 3 and the development bias in the development device 4.

  FIG. 10B shows an example in which the exposure intensity is changed.

  In EX1, EX2, and 2X3 corresponding to the toner-deficient portions TD1, TD2, and TD3 on the toner rearrangement electrode 10, the exposure intensity is high. As a result, the amount of toner that moves from the developing device to the photoreceptor 1 increases in EX1, EX2, and EX3, and the toner amount shortage on the toner rearrangement electrode 10 is corrected.

  The photoreceptor 1 and the toner rearrangement electrode 10 rotate at a constant speed ratio, and the exposure device 3 and the toner rearrangement electrode 10 are fixedly installed. The position of the exposure device 3 and the toner rearrangement electrode 10 are fixed. The position of is invariant. Therefore, it is easy to synchronize the operation of the exposure apparatus 3 with the profile shown in FIG. 10A so that the light emission amount is as shown in FIG. A uniform toner layer can be formed on the toner rearrangement electrode 10 by performing the exposure shown in FIG. 10B corresponding to the profile shown in FIG.

  In step ST34, toner is applied under the set conditions, for example, the exposure conditions shown in FIG.

The continuous image forming process was executed under the following common conditions to evaluate the image quality.
(1) Common conditions:
・ Environment: NN (normal temperature and humidity)
-Photoconductor diameter: 60 mm
・ Developing roller diameter: 25 mm
・ Developing roller surface speed: 720 mm / s (reverse rotation development)
・ Development roller to photoreceptor gap: 0.30 mm
・ Developer transport amount on the developing roller: 220 g / m ²
Image forming device: Monochrome 80 ppm machine (process speed 400 mm / s)
-Toner diameter: 6.5 μm
・ Carrier diameter: 33μm
-Toner concentration: 7% by mass
-Developer amount in the developing unit: 1000 g
At the time of test relocation electrode condition: DC component -600 VAC component 1.3 kV f = 9 kHz gap (interval between photoconductor and toner relocation electrode) = 0.15 mm
(2) Image used for evaluation:
-Write dpi = 600 and 200 lpi line screen where dpi is the number of dots per 2.54 mm and lpi is the number of lines per 2.54 mm.
-Patch image comparison example shown in FIG. 11: No toner application step without applying toner to the toner rearrangement electrode.
Example 1: As shown in FIG. 6, toner application is performed at a sensor output of 3.0 V or more, and when the sensor output is 2.0 V or less as a result of toner application, the toner application process is terminated.
Example 2: When the sensor output exceeds 3.0 V, toner is applied under the application condition corresponding to the profile shown in FIG. 9A of the toner layer on the toner rearrangement electrode, and the sensor output is 3.0 V or less. It ends when it becomes.

  The evaluation results are shown in Tables 2 and 3.

  Table 2 shows the results of the tip missing and suction as evaluation items, and Table 3 shows the results of scoring as evaluation items.

  Both Examples 1 and 2 were good with respect to chipping and suction. On the other hand, the comparative example was inferior in terms of chipping and suction. Table 3 shows the evaluation results of the roughness of the image. As shown in Table 3, the example of the roughness was good, but the comparative example was bad.

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging apparatus 3 Exposure apparatus 4 Developing apparatus 10 Toner rearrangement electrode 10A, 10B Power supply 20 Control part

Claims (7)

An image carrier;
A latent image forming apparatus for forming an electrostatic latent image on the image carrier;
A developing device that develops an electrostatic latent image carried on the image carrier and forms a toner image on the image carrier;
An electrode located on the downstream side in the moving direction of the image carrier with respect to the developing device and disposed opposite the image carrier;
A power supply for applying at least an alternating voltage to the electrodes;
In an image forming apparatus comprising:
A toner applying unit for applying toner to the electrode;
A toner sensor for detecting toner on the electrode;
An image forming apparatus comprising: a control unit that controls the toner applying unit based on a detection result of the toner sensor to execute a toner applying process. The toner applying unit includes the developing device and the image carrier.
The image forming apparatus according to claim 1, wherein the toner in the developing device is moved to the image carrier, and the toner on the image carrier is moved to the electrode. The control unit, when the toner sensor detects that the amount of toner on the electrode is equal to or less than a predetermined value, executes the toner applying step for supporting the toner on the electrode. The image forming apparatus according to claim 1. 4. The control unit according to claim 1, wherein the control unit creates a profile of a toner layer on the electrode based on a detection result of the toner sensor, and executes the toner applying step based on the profile. The image forming apparatus according to claim 1. 5. The image forming apparatus according to claim 1, wherein the control unit executes an electrode condition adjusting step of adjusting an output of the power source in the image forming step. The electrode condition adjusting step includes: a toner discharging step for removing toner on the electrode; a step of applying toner on the electrode; a step of detecting the amount of toner on the electrode by the toner sensor; and a detection result The image forming apparatus according to claim 5, further comprising: setting the output of the power supply based on A temperature sensor, a humidity sensor, a coverage information generation unit, a number counter, and an information generation unit including at least one stop time information generation unit, and the control unit performs the electrode condition adjustment step. The image forming apparatus according to claim 5, wherein whether or not to execute is determined based on information from the information generation unit.