JP2006220699A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-efficiency image forming apparatus having high productivity in printing by preventing soiling on a transfer member by toner due to the toner sticking to the transfer member which comes in contact with an image carrier. <P>SOLUTION: Regarding the image forming apparatus provided with an image forming means for forming the toner image on the image carrier, a transfer apparatus for transferring the toner image formed on the image carrier to a recording material, and a control means for performing a forcible consumption process of forcibly discharging the toner from the image forming means after forming a forcible consumption toner image on the image carrier by the image forming means, the width of the image carrier is wider than the transfer width of the transfer apparatus, and the control means controls the image forming means so that the forcible consumption toner image may be formed outside a transfer area in the width direction of the image carrier. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrophotographic image forming apparatus, and more particularly to an image forming apparatus that forcibly consumes toner that forcibly discharges toner from a developing device.

  In an electrophotographic image forming apparatus, a technology for forming a high-quality image excellent in image characteristics such as resolution and detail image reproducibility has been developed, and it becomes possible to form a high-quality image equivalent to printing. ing. Therefore, as the image quality is improved, the deterioration of the image quality due to the deterioration of the toner becomes a problem, and countermeasures for this are being studied.

  It has been clarified that toner deterioration mainly occurs when toner stays in the developing device for a long period of time, and is caused by the toner being subjected to stress for a long time due to stirring and conveyance in the developing device. .

As a countermeasure against such toner deterioration, a technique for forcibly discharging the toner in the developing device and replacing the toner for replenishing new toner has been developed (see Patent Documents 1 and 2).
JP 2000-206744 A JP 2003-270878 A

  In the forced toner consumption process for forcibly discharging the toner in the developing device, a solid image latent image is formed on the photosensitive member by the exposure device, the latent image is developed by the developing device, and the solid image is formed on the photosensitive member. By forming the toner image, the toner is discharged from the developing device onto the photoreceptor. The solid toner image formed on the photoreceptor is removed by a cleaning device.

  In the image forming apparatus using the intermediate transfer member, the solid toner image formed on the photosensitive member is transferred to the intermediate transfer member and removed from the intermediate transfer member by a cleaning device that cleans the intermediate transfer member.

  As described in Patent Document 1, a toner image for forced consumption is formed in an area called an inter image portion, that is, between a recording toner image and a recording toner image. Therefore, in the forced consumption step of forming the toner image for forced consumption between the recording toner images, an interval is provided for the forced consumption toner image between the recording toner images, so that the image interval is widened. There is a problem that print productivity or copy productivity (hereinafter referred to as print productivity in a sense including both) is lowered.

  In addition, in the transfer section that transfers the toner image to the recording material, the image carrier that carries the toner image for forced consumption and the transfer member directly face each other without the recording material interposed therebetween. There is a problem of moving and soiling the transfer member. When the transfer member is composed of a transfer roller in contact with the image carrier, the transfer roller becomes soiled, and in the next image forming process, the toner adhering to the transfer roller is reversely transferred to the recording material, and the recording material Undesirable phenomena such as backside contamination occur.

  An object of the present invention is to solve the above-described problem in an image forming apparatus that forcibly consumes toner.

The object is achieved by the following invention.
(Claim 1)
Image carrier,
Image forming means for forming a toner image on the image carrier;
A transfer device for transferring a toner image on the image carrier to a recording material; and
In the image forming apparatus, the image forming unit includes a control unit configured to form a forced consumption toner image on the image carrier and forcibly discharging the toner from the image forming unit.
The image carrier has a width larger than the transfer width of the transfer device, and the control means forms the forced consumption toner image outside the transfer region in the width direction of the image carrier. An image forming apparatus that controls a forming unit.
(Claim 2)
The image carrier is composed of a photoconductor, and the image forming unit includes a charging device that charges the photoconductor, an exposure device that exposes the photoconductor, and a developing device that develops a latent image on the photoconductor, The image forming apparatus according to claim 1, wherein the control unit forms the toner image for forced consumption by controlling the exposure apparatus.
(Claim 3)
The image carrier is an intermediate transfer member, and the image forming unit includes a photosensitive member, a charging device, an exposure device, a developing device, and a primary transfer device. The charging device and the exposure device expose the exposure device. A latent image is formed on the photosensitive member, the latent image is developed by the developing device to form a toner image on the photosensitive member, and the toner image is transferred to the intermediate transfer member by the primary transfer device. Is,
The image forming apparatus according to claim 1, wherein the control unit controls the exposure apparatus to form the toner image for forced consumption on the intermediate transfer member.
(Claim 4)
2. A detection unit for detecting an image rate or a toner consumption rate, wherein the control unit executes the forced consumption step according to the detected image rate or the toner consumption rate. The image forming apparatus according to claim 1.
(Claim 5)
5. The control unit according to claim 4, wherein the control unit controls at least one of a density and a size of the toner image for forced consumption according to the image rate or the toner consumption rate detected by the detection unit. Image forming apparatus.
(Claim 6)
6. The transfer device according to claim 1, wherein the transfer device has a power supply for applying a transfer voltage, and the control unit controls the power supply so that TP2 <TP1. TP1 is an output of the power source when a recording toner image passes through the transfer device, and TP2 is an output of the power source when the toner image for forced consumption passes through the transfer device. It is.
(Claim 7)
A photosensitive member, a charging device for charging the photosensitive member, an exposure device for exposing the charged photosensitive member to form a latent image, and developing the latent image on the photosensitive member to form a toner image on the photosensitive member. An image forming unit having a developing device and a primary transfer device
Intermediate transfer member, and
A secondary transfer device for transferring a toner image on the intermediate transfer member to a recording material;
A toner image formed on the photosensitive member is transferred to the intermediate transfer member by the primary transfer device, and the toner image on the intermediate transfer member is transferred to a recording material by the secondary transfer device. In the image forming apparatus,
The photoconductor has a width larger than the transfer width of the primary transfer device, and also has a control unit, and the control unit is configured to detect the photosensitivity outside the transfer region of the primary transfer device in the width direction of the photoconductor. An image forming apparatus, wherein a toner image for forced consumption is formed on a body to perform a forced toner consumption step.
(Claim 8)
The intermediate transfer member has a width larger than the transfer width of the secondary transfer device, and the control means is disposed on the intermediate transfer member outside the transfer region of the secondary transfer device in the width direction of the intermediate transfer member. 8. The image forming apparatus according to claim 7, wherein a forced consumption process is executed by forming a toner image for forced consumption.

  According to the invention of any one of claims 1 to 8, since the toner image for forced consumption is formed outside the transfer area of the transfer device, the toner forming the toner image for forced consumption is transferred to the transfer device. There is nothing. Therefore, the toner contamination of the transfer member caused by the transfer is prevented by the toner adhering to the transfer device, particularly the transfer member contacting the image carrier. As a result of preventing the transfer member from being stained, the back surface of the recording material caused by the transfer member is also prevented from being stained. Further, when a forced consumption toner image is formed at an image interval, it is necessary to widen the image interval in order to form a forced consumption toner image, which reduces print productivity. According to the first to eighth aspects of the present invention, a high-efficiency image forming apparatus having high print productivity is realized without causing such a decrease in print productivity.

  According to the fourth or fifth aspect of the present invention, image formation that prevents a decrease in image quality due to toner deterioration that occurs when an image with a low image rate or toner consumption rate is formed is prevented, and an image formation that stably outputs a high-quality image is achieved. A device is realized.

  According to the sixth aspect of the present invention, contamination inside the apparatus such as a transfer device, which is likely to occur due to the formation of a toner image for forced consumption, is particularly well prevented.

  The present invention will be described below based on the embodiments, but the present invention is not limited to the embodiments described below. FIG. 1 is a diagram showing an overall configuration of a color image forming apparatus according to an embodiment of the present invention.

  In FIG. 1, 10Y, 10M, 10C, and 10K are photosensitive members, 11Y, 10M, 10C, and 10K are charging devices, 12Y, 12M, 12C, and 12K are exposure devices, 13Y, 13M, 13C, and 13K are developing devices, and 14Y, 14M, 14C and 14K are cleaning devices for cleaning the surface of the photosensitive member, 15Y, 15M, 15C and 15K are primary transfer devices, and 20 is an intermediate transfer member formed of an endless belt.

The image forming unit Y includes a photoreceptor 10Y, a charging device 11Y, an exposure device 12Y, a developing device 13Y, a cleaning device 14Y, and a primary transfer device 15Y.
The image forming unit M includes a photoreceptor 10M, a charging device 11M, an exposure device 12M, a developing device 13M, a cleaning device 14M, and a primary transfer device 15M.
The image forming unit C includes a photoreceptor 10C, a charging device 11C, an exposure device 12C, a developing device 13C, a cleaning device 14C, and a primary transfer device 15C.
The image forming unit K includes a photoreceptor 10K, a charging device 11K, an exposure device 12K, a developing device 13K, a cleaning device 14K, and a primary transfer device 15K. The charging device 11Y and the exposure device 12Y, the charging device 11M and the exposure device 12M, The charging device 11C and the exposure device 12C, and the charging device 11K and the exposure device 12K constitute a latent image forming unit that forms an electrostatic latent image on the photoreceptors 10Y, 10M, 10C, and 10K, respectively.

  The image forming units Y, M, C, and K constitute an image forming unit that forms a toner image on the intermediate transfer member 20, and these units are Y, M, C, and K with respect to the traveling direction of the intermediate transfer member 20. The photoconductors 10Y, 10M, 10C, and 10K are in contact with the stretched surface of the intermediate transfer body 20, and rotate at the contact point in the same direction as the traveling direction of the intermediate transfer body 20 and at the same linear speed. To do.

  The intermediate transfer member 20 is stretched around a driving roller 21, an earth roller 22, a tension roller 23, and a driven roller 24, and the belt unit BU is constituted by these rollers, the intermediate transfer member 20, the primary transfer device 25, the cleaning device 28, and the like. To do.

  The intermediate transfer member 20 travels by rotation of the drive roller 21 by a drive motor (not shown).

  For example, an organic semiconductor formed by applying a coating liquid in which a phthalocyanine pigment is dispersed in polycarbonate to the outer periphery of a cylindrical metal base formed of an aluminum material with an outer diameter of 60φ is applied to the photoreceptors 10Y, 10M, 10C, and 10K. The charging potential of the photoconductor 10 can be controlled within the range of −250 V to −900 V, and the potential of the highest density portion can be controlled within the range of −45 V to −150 V.

  The charging devices 11Y, 11M, 11C, and 11K are scorotron chargers having discharge electrodes and a control grid.

  An electrical signal corresponding to image data from the reading device SU or an external device is converted into an optical signal by a semiconductor laser, and image exposure is performed by the exposure devices 12Y, 12M, 12C, and 12K. As the exposure apparatus, a scanning exposure apparatus using a semiconductor laser as a light source is used.

  Each of the developing devices 13Y, 13M, 13C, and 13K uses a two-component developer mainly composed of toner and carrier, and the developing bias includes a DC component voltage Vdc = −200 V to −700 V, and an AC component voltage Vac = 0.5 kV to 2.0 kV is applied. The AC component is used at a frequency f = 2 kHz to 7 kHz. The AC component voltage Vac is a peak-to-peak voltage.

  Polymerized toner is used as the toner, and resin-coated carrier is used as the carrier.

The intermediate transfer body 20 is a semiconductive endless belt having a volume resistivity of 10 ⁶ Ω · cm and a surface resistance of about 10 ¹¹ Ω / □. For example, modified polyimide, thermosetting polyimide, ethylene tetrafluoroethylene copolymer, polyfluoride This is a semiconductive seamless belt having a thickness of 0.015 to 0.05 mm, in which a conductive material is dispersed in an engineering plastic such as vinylidene or nylon alloy. The belt tension of the intermediate transfer member 20 is about 50N.

  The primary transfer devices 15Y, 15M, 15C, and 15K are applied with a DC voltage having a polarity opposite to that of the toner, and transfer the toner images formed on the photoreceptors 10Y, 10M, 10C, and 10K onto the intermediate transfer body 20. . The primary transfer device 15 has a transfer roller composed of a semiconductive foam roller.

  The secondary transfer device 26 has a transfer roller 26 </ b> A as a transfer member that can contact and release the intermediate transfer body 20, and a transfer power source 26 </ b> B that applies a transfer voltage to the transfer roller 26 </ b> A, and is formed on the intermediate transfer body 20. The transferred toner image is retransferred to the recording material P. The transfer roller 26A is a semiconductive foam roller.

  Reference numeral 27 denotes a paper feeding unit that supplies the recording material P to a transfer position where transfer by the secondary transfer device 26 is performed, 28 denotes a fixing device that fixes an unfixed toner image on the recording material P, and 29 denotes a cleaning of the intermediate transfer body 20. Cleaning device.

  In the image forming units Y, M, C, and K, a single color toner image is formed, transferred to the intermediate transfer member 20 by the primary transfer devices 15Y, 15M, 15C, and 15K, and superimposed on the intermediate transfer member to form a color toner image. Is formed. The color toner image on the intermediate transfer member 20 is transferred to the recording material P by the secondary transfer device 26. The color toner image transferred to the recording material P is fixed by the fixing device 28.

  Thus, a toner image is formed on the intermediate transfer member 20 as an image carrier by the image forming units Y, M, C, and K as image forming means. Then, the toner image is transferred onto the recording material P by the secondary transfer device 26.

  The photoreceptors 10Y, 10M, 10C, and 10K after the transfer are cleaned by the cleaning devices 14Y, 14M, 14C, and 14K, respectively. Further, the intermediate transfer member 20 after the transfer is cleaned by a cleaning device 29.

  2 shows the photoreceptors 10Y, 10M, 10C, and 10K in the image forming units Y, M, C, and K, the charging devices 11Y, 11M, 11C, and 11K, the exposure devices 12Y, 12M, 12C, and 12K, the developing devices 13Y, 13M, and the like. 13C and 13K and the cleaning devices 14Y, 14M, 14C, and 14K are shown. Since these portions have the same structure, the reference characters Y, M, C, and K are omitted and shown in FIG.

  The charging device 11 includes a discharge electrode 11A and a control grid 11B, and the charging potential of the photoconductor 10 is controlled by controlling the control grid 11B. The control grid 11B is feedback-controlled based on the potential detected by the potential sensor 17 that detects the surface potential of the photoconductor 10, and charges the charged potential of the photoconductor 10 to a desired constant potential.

  In FIG. 2, reference numeral 13 </ b> A denotes a casing for storing a two-component developer composed of toner and carrier, and a fixed magnet roll 132 is provided inside the developing sleeve 130. Reference numeral 133 denotes a regulating member that regulates the amount of developer conveyed through the developing sleeve 130. Reference numerals 135 and 136 denote screws that stir and convey the developer. The toner is supplied from the toner replenishing device 30 into the developing device 13.

  The stirring chamber DB in which the screw 135 is disposed and the supply / recovery chamber DA in which the screw 136 is disposed are separated by a partition 13B. The partition 13B has a developer at the end in the rotational axis direction of the screws 135 and 136, although not shown. Passing holes are provided through which.

  In the housing 13 </ b> A, an opening is formed at a portion where the developing sleeve 130 faces the photoconductor 10 to form a developing region G. A toner density sensor 137 detects the toner density of the developer in the developing device 13.

  Development is performed as follows.

  In FIG. 2, as the photosensitive member 10 is indicated by W0, the developing sleeve 130 is indicated by W1, the screw 135 is indicated by the arrow W2, and the screw 136 is indicated by the arrow W3, respectively. Are transported as follows: screw 135 → screw 136 → developing sleeve 130, and development is performed in the development region G. As shown in the drawing, in the developing region G, the photosensitive member 10 and the developing sleeve 130 move in opposite directions, and development is performed.

  A developing bias voltage in which a DC voltage is superimposed on an AC voltage is applied to the developing sleeve 130 by bias power supplies E1 and E2. The bias power source E1 is a DC component power source, and the bias power source E2 is an AC component power source.

  Hereinafter, toner replacement by forced consumption and forced replenishment of toner will be described with reference to FIG. 2 and subsequent drawings. This toner replacement is independent in each of the image forming units Y, M, C, and K in FIG. Executed.

  In the following description, the forced cover process performed in the image forming units Y, M, C, and K will be described with the symbols Y, M, C, and K attached to the components omitted.

  FIG. 3 is a block diagram of a control system of the image forming apparatus according to the embodiment of the present invention. 40 is a control unit that controls the whole, 41 is an image processing unit that generates an image signal for driving the exposure device 12 by processing an image signal obtained by image reading or an image signal received from the outside, and 42 is an image recording unit. A recording material transport unit that outputs size information of the recording material to be printed and information on the number of recording materials forming an image.

  The control unit 40 controls each unit shown in FIG. 1 to form an image on the recording material P, and executes a forced toner consumption process described below and shown in FIG.

  In STEP 1 of FIG. 4, the control unit 40 as a detection unit that detects the image rate calculates the image rate.

  The image rate PR is the ratio of the cumulative value of the image information forming the recording image to the total area of the image area, and is expressed as PR = M / S × 100.

  M is a cumulative value of the image information, and the control unit 40 inputs the image information from the image processing unit 41 and calculates the cumulative value M. In the case of a binary image, the accumulated value of image information is the accumulated value of the number of black pixel dots, and in the case of a multi-valued image, it is the accumulated value of pixel values.

  S is the total area of the image area, and is calculated based on the cumulative value of the length in the conveyance direction of the recording material based on the recording material size information and the number of sheets information from the recording material conveyance unit 42.

  FIG. 5 shows the concept of image rate calculation.

Images B1, B2,... Bn whose density is not 0 are formed in the image areas A1, A1, A3.
The image areas A1, A2, and A3 are areas of the image carrier Z excluding the image intervals C1 and C2, and the widths of the images F1, F2, and F3 (the images F1 and F1 in the direction perpendicular to the moving direction X of the image carrier) This is a region in which the side lengths of F2 and F3 are uniform. In FIG. 5, the image rate PR is represented by (ΣBn / ΣAm) × 100.

  In place of the image rate, a toner consumption rate can be used.

  The toner consumption rate TR is a ratio of the cumulative value of the image information to the operation amount of the developing device, and is represented by TR = M / D × 100.

  D is a cumulative value of the rotation amount of the developing sleeve and the agitating / conveying member (developing sleeve 130 and screws 135, 136 in FIG. 2) in the developing device, and the control unit 40 operates from the command signal for driving the developing device 13. Is calculated.

  The calculation of the image rate PR or the toner consumption rate TR is performed every time a predetermined number N of images are formed, and is calculated by the control unit 40 as a detection unit.

  As the image rate described above, the print rate, that is, the ratio of the amount of image information to the area of the images F1, F2, and F3 is used, or the image area (A1 + A2 + A3...) + Image interval (C1 + C2. It is also possible to calculate by an approximate calculation such as using the ratio of the amount of image information to

  In STEP 2, the toner is forcibly discharged.

  Forcibly discharging the toner, the exposure unit 12 is driven by controlling the image processing unit 41 to form a latent image for forced consumption on the photoconductor 10, and the forcible consumption is performed on the photoconductor 10 by the developing device 13. This toner image is formed, and a toner image for forced consumption is formed on the intermediate transfer member 20 by the primary transfer device 25.

  The forced consumption toner image formed on the intermediate transfer member 20 is removed from the intermediate transfer member 20 by the cleaning device 29 without being transferred.

  FIG. 6 shows a toner image for forced consumption.

  The toner image PG for forced consumption is formed outside the image F on both sides of the image F on the intermediate transfer body 20. In the figure, X is the moving direction of the intermediate transfer member 20, and the forced consumption toner image PG is formed outside the images F on both sides in the width direction of the intermediate transfer member 20, that is, in the direction perpendicular to the moving direction X.

  Moreover, the forced consumption toner image PG is formed outside the transfer area of the secondary transfer device 26. In the figure, W1 indicates the width of the intermediate transfer member 20, and W2 indicates the width of the transfer region of the secondary transfer device 26, that is, the transfer width. As shown in the drawing, W1> W2, and the toner image PG for forced consumption is formed on the intermediate transfer body 20 outside the transfer width W2. The transfer width W <b> 2 is the length of the transfer roller 26 </ b> A that constitutes the transfer device 26.

  6A shows an example in which a toner image for forced consumption is formed at a position overlapping the image A with respect to the moving direction X of the intermediate transfer member 20, and FIG. 6B shows the moving direction X of the intermediate transfer member 20. FIG. 6C illustrates an example in which a toner image for forced consumption is formed at a position that is between the images F and F and does not overlap the image F. FIG. 6C illustrates the image from the position of the image F with respect to the moving direction of the intermediate transfer member 20. This is an example in which a toner image for forced consumption is formed over the area between F.

  In the transfer portion formed by the secondary transfer device 26 in FIG. 1, when the recording material P passes, the intermediate transfer body 20 and the transfer device 26 face each other directly outside the area of the image F. As shown in FIG. 6, the transfer roller 26 </ b> A of the transfer device 26 does not face the portion where the toner image PG for forced consumption is formed. Therefore, it is possible to prevent the toner image for forced consumption from being transferred to the transfer device 26 and soiling the transfer roller 26A of the transfer device 26.

  In the forced consumption process in which a toner image for forced consumption is formed between images in the transfer area of the transfer device 26, that is, the range of the transfer width W2, the toner image for forced consumption is transferred to the transfer member and stains the transfer member. Therefore, in order to prevent this, it is necessary to provide a transfer member cleaning means for cleaning the transfer member, or in the forced consumption process, it is necessary to separate the transfer member from the image carrier. As described above, by forming the toner image PG for forced consumption outside the transfer region, there is no need to provide a transfer member cleaning unit, and the transfer member (transfer roller 26A) is separated from the image carrier (intermediate transfer member 20). There is no need.

  Further, as shown in FIGS. 6A to 6C, in order to form the toner image PG for forced consumption, it is not necessary to widen the interval between the images F, and the image interval between the images F is forcibly consumed. It is possible to set regardless of the toner image PG for use. Therefore, by executing the forced toner consumption process, it is possible to prevent the adverse effect that the image interval is widened and the print productivity is lowered.

  The amount of toner that is forcibly consumed can be changed according to the image rate. As a mode of forced consumption corresponding to the image rate, the forced consumption may be continuously changed according to the image rate, or the forced consumption may be changed stepwise according to the image rate. As a typical mode of forced consumption, there is a mode in which a threshold of the image rate is set and forced consumption is executed when the threshold is lower than the threshold.

  In the forced consumption process for forming the forced consumption toner image PG shown in FIG. 6B, the transfer power supply 26B in the transfer device can be controlled to prevent the toner from scattering in the transfer portion. The control unit 40 controls the transfer power supply 26B in FIG. 1, and sets the output TP2 of the transfer power supply 26B in the image interval C to be lower than the output TP1 in the image area A as shown in FIG. This prevents the toner from scattering due to electrostatic force. The output of the transfer power supply 26B can be controlled by controlling at least one of voltage and current.

  In STEP 3, toner is forcibly supplied. The forced supply is performed by the toner supply device 30. In the forcible replenishment, a toner replenishment of an amount substantially equal to the amount discharged by the forced discharge in STEP 3 is performed, whereby the toner density of the developer in the developing device is maintained constant. Such toner replenishment control is performed based on the toner density information detected by the toner density sensor 137 shown in FIG.

  FIG. 8 shows the relationship among the photoconductor, the intermediate transfer member, and the transfer device in another example of the embodiment of the present invention.

  The image forming apparatus having the relationship shown in FIG. 8 has the same structure as that shown in FIG. 1, and will be described with reference to FIG.

  In FIG. 8, as in FIG. 6, the width of the intermediate transfer member 20 is W1, and the length of the transfer roller 26A is W2. Further, the length of the transfer roller of the primary transfer device 25 is W3, and the width of the photoconductor 10 is W4. W1 to W4 are set so that W1 <W2 <W3 <W4 as illustrated. As in FIG. 6, the forced consumption toner image PG <b> 1 is formed on the intermediate transfer body 20 outside the transfer area indicated by W <b> 2.

  In the example of FIG. 8, the forced consumption toner image PG2 is formed on the photoreceptor 10 outside the transfer area of the primary transfer apparatus, that is, the area indicated by W3.

  The forced consumption toner image PG <b> 2 is formed on the photoreceptor 10 by charging of the charging device 11, exposure of the exposure device 12, and development of the developing device 13 in FIG. 2.

  The forced consumption toner image PG <b> 2 is formed outside the transfer area of the primary transfer device 15 as shown in the figure, so it is not formed on the intermediate transfer body 20 but is removed from the photoconductor 10 by the cleaning device 14.

  As described above, the forced consumption toner image PG1 is not transferred by the transfer device 26, but is removed from the intermediate transfer member 20 by the cleaning device 29.

  In FIG. 8, the forced consumption toner image PG1 may not be formed, and only the forced consumption toner image PG2 may be formed to forcibly consume the toner.

  FIG. 9 is an example of an embodiment that does not use an intermediate transfer member.

  A charging device 11, an exposure device 12, a developing device 13, a transfer device 15, a separating device 16, and a cleaning device 14 are disposed around a photoconductor 10 as an image carrier. Reference numeral 28 denotes a fixing device, and 30 denotes a toner replenishing device.

  In the image forming process, a toner image is formed on the photoreceptor 10 by charging by the charging device 11, exposure by the exposure device 12, and development by the developing device 13, and the toner image is transferred to the recording material P by transfer by the transfer device 15. Then, the toner image on the recording material P is fixed by the fixing device 28.

  In the toner forced consumption process, a latent image for forced consumption is formed on the photoconductor 10 by charging by the charging device 11 and exposure for forced consumption by the exposure device 12. The forced consumption latent image formed on the photoreceptor 10 is developed by the developing device 13, and a forced consumption toner image is formed on the photoreceptor 10. By this development, the toner is forcibly discharged from the developing device 13.

  The forced consumption toner image formed on the photoconductor 10 reaches the cleaning device 14 without being transferred by the transfer device 15 and is removed from the photoconductor 10 by the cleaning device 14.

  In this example, the transfer device 15 includes a corotron charger. In the corotron charger, the transfer width W2 in FIG. 6 is the length of the discharge region in the direction perpendicular to the moving direction of the photoconductor 10. FIG. In the same manner as described above, the width of the photosensitive member 10 (the length in the rotation axis direction of the photosensitive member 10) W1 and the transfer width W2 of the transfer region of the transfer device 15 are set to have a relationship of W1> W2. The toner image PG for forced consumption is formed on the photoreceptor 10 outside the transfer area.

  With this configuration, the transfer device 15 is prevented from being contaminated in the toner forced consumption process. Although the separation device 16 includes a corotron charger, toner discharge of the separation device 16 can be prevented by setting the discharge area of the separation device 16 to be substantially equal to the width of the transfer region of the transfer device 15.

1 is a diagram illustrating an example of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a diagram illustrating portions of a photoconductor, a charging device, an exposure device, a developing device, and a cleaning device in an image forming unit. 2 is a block diagram of a control system of the image forming apparatus according to the embodiment of the present invention. FIG. It is a flowchart of a forced consumption process. It is a conceptual diagram of image rate calculation. FIG. 6 is a diagram illustrating a toner image for forced consumption. It is a figure which shows the output of a transfer power supply. It is a figure which shows the relationship between the photoreceptor, the intermediate transfer body, and the transfer apparatus in the other example of embodiment of this invention. It is a figure which shows the example of embodiment which does not use an intermediate transfer body.

Explanation of symbols

10, 10Y, 10M, 10C, 10K photoconductor 11, 11Y, 11M, 11C, 11K charging device 12, 12Y, 12M, 12C, 12K exposure device 13, 13Y, 13M, 13C, 13K developing device 15, 15Y, 15M, 15C, 15K Primary transfer device 20 Intermediate transfer member 26 Secondary transfer device 30 Toner supply device 40 Control unit 41 Image processing unit 42 Recording material transport unit Y, M, C, K Image forming unit

Claims (8)

Image carrier,
Image forming means for forming a toner image on the image carrier;
A transfer device for transferring a toner image on the image carrier to a recording material; and
In the image forming apparatus, the image forming unit includes a control unit configured to form a forced consumption toner image on the image carrier and forcibly discharging the toner from the image forming unit.
The image carrier has a width larger than the transfer width of the transfer device, and the control means forms the forced consumption toner image outside the transfer region in the width direction of the image carrier. An image forming apparatus that controls a forming unit. The image carrier is composed of a photoconductor, and the image forming unit includes a charging device that charges the photoconductor, an exposure device that exposes the photoconductor, and a developing device that develops a latent image on the photoconductor, The image forming apparatus according to claim 1, wherein the control unit forms the toner image for forced consumption by controlling the exposure apparatus. The image carrier is an intermediate transfer member, and the image forming unit includes a photosensitive member, a charging device, an exposure device, a developing device, and a primary transfer device. The charging device and the exposure device expose the exposure device. A latent image is formed on the photosensitive member, the latent image is developed by the developing device to form a toner image on the photosensitive member, and the toner image is transferred to the intermediate transfer member by the primary transfer device. Is,
The image forming apparatus according to claim 1, wherein the control unit controls the exposure apparatus to form the toner image for forced consumption on the intermediate transfer member. 2. A detection unit for detecting an image rate or a toner consumption rate, wherein the control unit executes the forced consumption step according to the detected image rate or the toner consumption rate. The image forming apparatus according to claim 1. 5. The control unit according to claim 4, wherein the control unit controls at least one of a density and a size of the toner image for forced consumption according to the image rate or the toner consumption rate detected by the detection unit. Image forming apparatus. 6. The transfer device according to claim 1, wherein the transfer device has a power supply for applying a transfer voltage, and the control unit controls the power supply so that TP2 <TP1. TP1 is an output of the power source when a recording toner image passes through the transfer device, and TP2 is an output of the power source when the toner image for forced consumption passes through the transfer device. It is. A photosensitive member, a charging device for charging the photosensitive member, an exposure device for exposing the charged photosensitive member to form a latent image, and developing the latent image on the photosensitive member to form a toner image on the photosensitive member. An image forming unit having a developing device and a primary transfer device
Intermediate transfer member, and
A secondary transfer device for transferring a toner image on the intermediate transfer member to a recording material;
A toner image formed on the photosensitive member is transferred to the intermediate transfer member by the primary transfer device, and the toner image on the intermediate transfer member is transferred to a recording material by the secondary transfer device. In the image forming apparatus,
The photoconductor has a width larger than the transfer width of the primary transfer device, and also has a control unit, and the control unit is configured to detect the photosensitivity outside the transfer region of the primary transfer device in the width direction of the photoconductor. An image forming apparatus, wherein a toner image for forced consumption is formed on a body to perform a forced toner consumption step. The intermediate transfer member has a width larger than the transfer width of the secondary transfer device, and the control means is disposed on the intermediate transfer member outside the transfer region of the secondary transfer device in the width direction of the intermediate transfer member. 8. The image forming apparatus according to claim 7, wherein a forced consumption process is performed by forming a toner image for forced consumption.

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