JP2008268356A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of discharging a suitable quantity of deteriorative toner from a developing unit by forming a disposable toner pattern, thereby suppressing degradation in image quality due to the deteriorative toner while suppressing wasteful discharge of proper toner. <P>SOLUTION: The image forming apparatus A comprises a disposable toner pattern forming means; a means for detecting the number of successive recording mediums used in an image forming process; a means for detecting an image formation area distribution on an electrostatic latent image carrier in the image forming process; and a means for determining whether toner in a developing unit has deteriorated or not. The disposable toner pattern forming means forms a disposable toner pattern when the toner in the developing unit is determined to have deteriorated. The disposable toner pattern is formed according to the number of successive recording mediums and the image formation area distribution. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multi-function machine combining two or more of these.

  An image forming apparatus such as a copying machine, a printer, a facsimile machine, or a combination machine combining two or more of these develops an electrostatic latent image corresponding to a target image formed on an electrostatic latent image carrier. In general, an image forming process can be performed in which a toner image is formed by developing in a container, and the toner image is transferred and fixed to a recording medium.

  In this type of image forming apparatus, when the toner in the developing device is not used for a while, or when the toner consumption for forming the toner image is small even if it is used, the unused toner stays in the developing device. As a result, the toner becomes deteriorated due to fluctuations in the electrical characteristics of the toner in the developing device, and the quality of the toner image formed thereafter may deteriorate.

  Therefore, if the toner in the developer is not used for a while, or if the toner consumption for the toner image formation is small even if it is used, the toner in the developer is discharged to some extent as waste toner during non-image formation. Has been done.

  This toner discharge is formed as such in an image forming apparatus that forms a waste toner pattern (for example, a waste toner image such as a solid image) on an electrostatic latent image carrier or an intermediate transfer member. This is done by further transferring the waste toner pattern to an intermediate transfer member.

  The waste toner pattern thus formed on the image carrier for forming the waste toner pattern (in the above example, the electrostatic latent image carrier or the intermediate transfer member) is removed from the image carrier by the cleaning device.

  For example, Japanese Patent Application Laid-Open No. 2005-62316 describes forming a waste toner pattern on an intermediate transfer member. In forming the waste toner pattern, in order to remove the pattern from the intermediate transfer member by the cleaning device without causing an increase in the size of the cleaning device or causing a cleaning failure, the waste toner pattern is set to a maximum recording medium passage width. It is described that it is formed in an inner area (image guarantee area) having a width corresponding to.

  Japanese Patent Application Laid-Open No. 2005-165217 discloses a method in which a plurality of patch images are formed on an electrostatic latent image carrier, the patch images are transferred to an intermediate transfer member by changing a transfer voltage, and the image on the intermediate transfer member is transferred. It is described that the amount of waste toner discharged from the developing device is adjusted by checking the toner state in the developing device based on the toner adhesion amount of the transfer patch image.

JP-A-2005-62316 JP 2005-165217 A

  However, the conventional toner discarding method does not determine the shape or the like of the discarded toner pattern according to the distribution of the image forming area on the electrostatic latent image carrier at the time of target image formation.

  For example, when continuously forming an image on a recording medium having a small width in the direction perpendicular to the conveying direction, such as a postcard, the image forming area on the electrostatic latent image carrier corresponding to the through area of the recording medium On the other hand, toner is consumed intensively in the area inside the developing device, while the amount of toner consumed in the area inside the developing device outside the area is small. In this case, the toner in the developing device area where the toner consumption is small is more likely to deteriorate than the toner in the developing device region where the toner consumption is large.

  In addition, regardless of the through-width of the recording medium, when the image forming portion on the recording medium is partially concentrated on the recording medium, the image forming area on the electrostatic latent image carrier is also on the electrostatic latent image carrier. In such a case, the toner in the developing unit area corresponding to the non-image forming area on the electrostatic latent image carrier has a consumption amount corresponding to the image forming area. The toner consumption in the area inside the developing device is smaller, and the toner deterioration is more likely to proceed.

  In such a case, the waste toner pattern is always constant regardless of the image forming area distribution on the electrostatic latent image carrier (for example, a pattern in which the length in the main scanning direction and the length in the sub scanning direction are constant). In such a case, the amount of normal toner that does not need to be discharged may be excessively increased, or the amount of deteriorated toner that is desirably discharged may be excessively decreased.

  Therefore, the present invention develops an electrostatic latent image corresponding to a target image formed on the electrostatic latent image carrier with a developing device to form a toner image, and transfers and fixes the toner image to a recording medium. A waste toner pattern including an image carrier for waste toner pattern and a developer for forming a waste toner pattern by the toner in the developer on the image carrier for waste toner pattern. In the image forming apparatus having the forming unit, the discharge amount of the deteriorated toner from the developing device due to the formation of the waste toner pattern may cause the normal toner discharge amount to be excessively increased or the deteriorated toner discharge amount to be decreased. It can be performed with an appropriate amount of discharged toner, and can reduce image quality deterioration due to deteriorated toner while suppressing wasteful release of normal toner. And to provide an image forming apparatus.

An image forming apparatus of the present invention that solves the above problems forms a toner image by developing an electrostatic latent image corresponding to a target image formed on an electrostatic latent image carrier with a developing device. An image forming apparatus capable of performing an image forming process for transferring and fixing a toner image on a recording medium, and forming a waste toner pattern image carrier and a waste toner pattern by the toner in the developing device on the waste toner pattern image carrier. An image forming apparatus having waste toner pattern forming means including the developing unit.
Here, the “image forming process” may form an image on only one recording medium, or may form images successively on a plurality of recording media sequentially.

This image forming apparatus
A continuous sheet number detecting means for detecting a continuous sheet number of the recording medium in the image forming process (there may be only one sheet);
Image forming area distribution detecting means for detecting an image forming area distribution on the electrostatic latent image carrier in the image forming process;
Toner deterioration determining means for determining whether or not the toner in the developing device is in a deteriorated state.

  The waste toner pattern forming means forms a waste toner pattern on the waste toner pattern image carrier when the toner deterioration determining means determines that the toner in the developing device is in a deteriorated state, and the waste toner pattern When forming, an appropriate amount of toner discharged for discharging deteriorated toner according to the continuous number of sheets of the recording medium detected by the continuous sheet number detecting means and the image forming area distribution detected by the image forming area distribution detecting means. Forming a waste toner pattern.

  According to the image forming apparatus of the present invention, when it is confirmed by the deteriorated toner determining means that the toner in the developing device is in a deteriorated state, the waste toner pattern forming means including the developing device uses the developing device to A waste toner pattern made of toner in the developing device is formed on the image carrier for the waste toner pattern.

  At this time, when forming the waste toner pattern, the waste toner pattern forming unit determines the continuous sheet number of the recording medium detected by the continuous sheet number detection unit and the image formation region distribution detected by the image formation region distribution detection unit. Accordingly, a waste toner pattern that achieves an appropriate amount of toner discharged for discharging deteriorated toner is formed. Furthermore, the amount of normal toner that does not need to be discharged does not increase too much, or the amount of deteriorated toner that is desirable to be discharged does not decrease too much. A waste toner pattern that achieves a proper amount of toner discharge is formed.

  According to the image forming apparatus of the present invention, in this way, the discharge of the deteriorated toner from the developing device due to the formation of the waste toner pattern may cause the normal toner discharge amount to be excessively increased or the deteriorated toner discharge amount to be decreased. It can be performed with an appropriate amount of discharged toner, and the reduction in image quality due to the deteriorated toner can be suppressed while suppressing wasteful discharge of normal toner.

  The image carrier for waste toner pattern may be the electrostatic latent image carrier itself, or when an intermediate transfer member is provided in a color image forming apparatus or the like, the electrostatic latent image carrier. The intermediate transfer member to which the waste toner pattern is transferred may be used. In any case, the waste toner pattern formed on the waste toner pattern image carrier may be removed by a cleaning device provided for the image carrier.

  The waste toner pattern forming means is an appropriate amount for discharging the deteriorated toner according to the continuous number of sheets of the recording medium and the image forming area distribution according to the determination of “deteriorated toner state in the developing device” by the toner deterioration determining means. When forming a waste toner pattern that achieves the toner discharge amount, for example, the waste toner pattern can be formed as follows.

  That is, when the continuous number of sheets of the recording medium detected by the continuous sheet number detecting means is equal to or smaller than a predetermined reference number, a predetermined fixed waste toner pattern (for example, the length in the main scanning direction and the sub-scanning direction). Each of the image forming regions on the electrostatic latent image carrier based on the image forming region distribution detected by the image forming region distribution detecting means. A waste toner pattern in which more toner is discharged in the non-image forming area is formed.

  Here, the “reference number” will be described. If the number of passing sheets of the recording medium in the image forming process is up to a certain level, the inside of the developing device is used regardless of the passing position and size (especially width) of the recording medium and the image position on the recording medium. The positional deviation in toner consumption is negligible. At this time, the waste toner pattern may be a predetermined pattern. Therefore, an example in which the “number of sheets to a certain extent” is obtained in advance by experiments or the like and used as the reference number of sheets can be given.

The following first and second detections can be exemplified as the image formation distribution detection by the image formation region distribution detection means.
(1) First image forming area distribution detection The electrostatic latent image carrier based on a position and a width on the electrostatic latent image carrier corresponding to a passing position and a passing width of the recording medium in the image forming process. The upper image forming area distribution is detected. In this case, the area of the position and width on the electrostatic latent image carrier corresponding to the passing position and the passing width of the recording medium is an image forming area, and is an area other than the maximum width that can be developed by the developing device. An area within the maximum width can be a non-image forming area.

(2) Second image forming region distribution detection The electrostatic latent image carrying of image data for forming an electrostatic latent image corresponding to a target image on the electrostatic latent image carrying member in the image forming process. The image forming region distribution is detected by accumulating position information on the body.

In this case, for example, the area on the electrostatic latent image carrier is divided in advance, and each divided area is set as an image forming area, and based on the accumulated information of the position of the image data on the electrostatic latent image carrier. Image data position accumulation information included in each divided area obtained in advance is obtained, toner consumption rate of the divided area is obtained from image data position accumulated information contained in each divided area, and each toner consumption rate is thus obtained. The distribution of the image forming area indicating the above is obtained. In this case, an area where the toner consumption rate is not “0” or “0” but is negligible corresponds to a non-image forming area.
Examples of the division of the area on the electrostatic latent image carrier include an example in which the area is divided into band-like areas extending in the sub-scanning direction, or the band-like area is further divided into several areas in the sub-scanning direction.

  When the electrostatic latent image is formed by scanning exposure on the electrostatic latent image carrier, when the exposure is performed by dot (point) exposure using a laser beam or the like, the dot information is recorded on one page of the recording medium for each scanning. Alternatively, the image data position information on the electrostatic latent image carrier may be accumulated by accumulating every time or every job (each image forming process).

  The toner deterioration determining means determines that the toner in the developing device is deteriorated when the toner consumption rate in the developing device is smaller than a predetermined reference consumption rate, and is equal to or higher than the reference consumption rate. For example, the toner in the developing unit can be determined as not deteriorated.

As the toner consumption rate in this case, an example of adopting [(toner consumption amount in the integrated driving time of the developing device) / (integrated driving time of the developing device)] can be given.
If the dot exposure site on the electrostatic latent image carrier is a site where toner adheres during development, the number of dots represents the amount of toner consumed. (The accumulated number of dots in the accumulated drive time) / (the accumulated drive time of the developing device)] may be employed as the toner consumption rate.
Note that the toner consumption rate may be corrected according to development characteristics and the like.

  As described above, according to the present invention, the electrostatic latent image corresponding to the target image formed on the electrostatic latent image carrier is developed with a developing device to form a toner image. An image forming apparatus capable of performing image forming processing to be transferred and fixed on a recording medium, and forming a waste toner pattern image carrier and a waste toner pattern formed by the toner in the developer on the waste toner pattern image carrier. An image forming apparatus having a waste toner pattern forming unit including a discharge amount of a deteriorated toner from a developing device due to the formation of the waste toner pattern, wherein a normal toner discharge amount is too large or a deteriorated toner discharge amount is small. Image quality due to deteriorated toner while suppressing wasteful release of normal toner. Possible to provide an image forming apparatus capable of suppressing degradation.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows an example A of an image forming apparatus according to the present invention.

  The image forming apparatus A is a tandem type full-color image forming apparatus. The image forming apparatus A has an endless intermediate transfer belt 2. The intermediate transfer belt 2 is wound around a driving roller 21 and a roller 22 opposite to the driving roller 21 and is rotated in the counterclockwise direction (arrow direction in the drawing) by the driving roller 21 driven by a belt driving unit (not shown). be able to.

  A cleaning device 8 for removing secondary transfer residual toner and the like on the transfer belt 2 faces the transfer belt portion on the roller 22.

The secondary transfer roller 3 faces the transfer belt portion on the driving roller 21.
The surface layer portion of the secondary transfer roller 3 is formed of an elastic material, and a nip portion N is formed between the secondary transfer roller 3 and the intermediate transfer belt 2 when pressed against the transfer belt 2, and is driven by the rotation of the intermediate transfer belt 2. Alternatively, as will be described later, the recording medium 50 is rotated following the movement of the recording medium 50 fed into the nip portion N.

  A secondary transfer bias can be applied to the secondary transfer roller 3 from a secondary transfer bias power supply (not shown). The secondary transfer roller 3 is brought into contact with and separated from the transfer belt 2 at a predetermined timing by a driving unit (not shown) so as not to hinder image formation.

  Below the secondary transfer roller 3, a timing roller pair 4 and a timing sensor s1 on the exit side thereof are arranged, and further below them, a recording medium containing cassette 5 containing a recording medium 50 is detachably mounted. Is done. The recording medium 50 accommodated in the cassette 5 can be pulled out one by one by the medium supply roller 51 and supplied to the timing roller pair 4. As the recording medium 50, a recording sheet, an overhead projector sheet, or the like can be used.

A fixing device 6 is disposed above the transfer roller 3.
The fixing device 6 includes a fixing roller 61 heated by a built-in halogen lamp heater (not shown) and a pressure roller 62 pressed against the fixing roller 61.

A recording medium conveyance path switching claw 70, a medium discharge roller pair 71, and a medium discharge tray 7 are provided on the downstream side of the fixing device 6 in the recording medium conveyance direction.
Further, a recording medium conveyance path 9 for forming a double-sided image is provided behind the secondary transfer roller 3. A pair of recording medium conveying rollers r1, r2, and r3 is disposed in the passage 9.

  Between the rollers 21 and 22 around which the intermediate transfer belt 2 is wound, the yellow image forming unit Y, the magenta image forming unit M, the cyan image forming unit C, and the rollers 22 to 21 are moved along the transfer belt 2. Black image forming portions K are arranged in this order.

  Each of the image forming units Y, M, C, and K includes a drum-type photoconductor 11 as an electrostatic latent image carrier, and a charger 12, an image exposure device 13, and a developer 14 are provided around the photoconductor. A primary transfer roller 15 and a cleaning device 16 for removing and cleaning the primary transfer residual toner and the like on the photosensitive member are arranged in this order.

The photoconductor 11, the charger 12, the image exposure device 13, the developing device 14, and the cleaning device 16 in each image forming unit are provided in a cartridge case, and form a process cartridge together with the cartridge case. That is, the yellow process cartridge YC for forming the yellow image forming portion Y, the magenta process cartridge MC for forming the magenta image forming portion M, the cyan process cartridge CC for forming the cyan image forming portion C, and the black image forming This is a black process cartridge KC for forming the portion K.
Each process cartridge has a non-volatile memory medium m mounted thereon. This memory medium will be described later.

  As shown in FIG. 1, the primary transfer roller 15 of each image forming unit faces the photoconductor 11 with the transfer belt 2 in between, and is rotated by the running of the belt. A primary transfer bias for primary transfer of a toner image formed on the photoreceptor 11 to the belt 2 can be applied to the primary transfer roller 15 from a primary transfer bias power supply (not shown).

  The exposure device 13 repeats dot exposure on the photosensitive member 11 in the main scanning direction (photosensitive member width direction) using a laser beam in accordance with image data provided from a personal computer (not shown) or the like, while in the sub-scanning direction. An electrostatic latent image is formed by performing exposure also in the (photosensitive member surface moving direction).

The photoconductor 11 in each image forming unit is a negatively chargeable photoconductor here, and is rotated clockwise in the drawing by a photoconductor drive motor (not shown).
A voltage for charging the photosensitive member is applied to the charger 12 in each image forming unit at a predetermined timing from a charging power supply (not shown).

  The developing unit 14 in each image forming unit employs a negatively chargeable toner in this example, and a developing bias voltage is applied to the electrostatic latent image formed on the photoconductor 11 from a developing bias power source (not shown). The reversal development can be performed by the developing roller 141. When the toner in the developing device is consumed, the toner is supplied from a toner supply hopper (not shown) according to the consumption.

  A cleaning device 16 in each image forming unit removes and cleans primary transfer residual toner and the like on the photosensitive member 11 with a cleaning blade.

  FIG. 2 is a block diagram showing an outline of a control circuit of the image forming apparatus A. The control circuit includes a control unit Cont that controls the overall operation of the image forming apparatus. An operation panel PA is connected to the control unit Cont. In addition to the print instruction key k1 for instructing image formation, the panel also includes a numeric keypad for setting the number of image formations, a key group Ke for setting the type of recording medium (size, etc.), a liquid crystal display unit Dp, and the like. Yes. The liquid crystal display unit Dp is used to reflect and display key operations by the user, to display an instruction menu for the user, and to display various information.

Each unit of the image forming apparatus A operates at a predetermined timing based on an instruction from the control unit Cont.
The memory medium m mounted on each process cartridge is connected to the controller Cont via a serial communication line when the cartridge is mounted on the image forming apparatus main body.

If communication between the control unit Cont and each memory medium m is established, the control unit Cont determines that the process cartridge is mounted at the corresponding cartridge mounting position.
If communication between the control unit Cont and the memory medium m of the cartridge is not established, it is determined that the cartridge is not attached.

  In addition, data indicating the color of the toner of the developing device 14 in the cartridge is written in advance in the memory medium m of the process cartridge, so that the controller Cont installs a cartridge of what color toner at each cartridge mounting position. It is possible to confirm whether each cartridge is mounted at a predetermined mounting position.

Image formation by the image forming apparatus A will be described.
The image forming apparatus A can form an image using at least one of the image forming units Y, M, C, and K. Taking a case where a full color image is formed using all of the image forming portions Y, M, C, and K as an example, first, a yellow toner image is formed in the yellow image forming portion Y, and this is formed on the transfer belt 2 as a primary. Transcript.

  That is, in the yellow image forming portion Y, the photosensitive member 11 is rotationally driven in the clockwise direction in the figure, and the surface is uniformly charged to a predetermined potential by the charger 12, and the yellow image is transferred from the image exposure device 13 to the charged area. Image exposure is performed, and an electrostatic latent image for yellow is formed on the photoreceptor 11. The electrostatic latent image is developed by a developing roller 141 to which a developing bias of a developing unit 14 having yellow toner is applied to become a visible yellow toner image, and the toner image is transferred onto the transfer belt 2 by a primary transfer roller 15. Primary transfer is performed. At this time, a primary transfer bias voltage is applied to the primary transfer roller 15 from a power supply (not shown).

  Similarly, a magenta toner image is formed in the magenta image forming unit M and transferred to the transfer belt 2, a cyan toner image is formed in the cyan image forming unit C and transferred to the transfer belt 2, and in the black image forming unit K. A black toner image is formed and transferred to the transfer belt 2.

Yellow, magenta, cyan, and black toner images are formed at the timing when these toner images are transferred onto the intermediate transfer belt 2 in an overlapping manner.
Thus, the multiple toner image formed on the transfer belt 2 moves toward the secondary transfer roller 3 by the rotation of the transfer belt 2.

  On the other hand, the recording medium 50 is pulled out from the cassette 5 by the medium supply roller 51 and supplied to the timing roller pair 4. At this time, the recording medium 50 is detected by the timing sensor s1 on the exit side of the roller pair 4, and by the detection, the roller pair 4 is temporarily stopped, and the recording medium 50 stands by at that position.

  At the timing when the toner image on the belt 2 arrives at the secondary transfer area where the secondary transfer roller 3 is located due to the rotation of the belt 2, the timing roller pair 4 feeds the recording medium 50 to the secondary transfer area.

  Thus, supply of the recording medium 50 is started toward the nip portion N between the transfer belt 2 and the secondary transfer roller 3 that is in pressure contact with the multiple toner images sent by the intermediate transfer belt 2. The toner image is secondarily transferred onto the recording medium 50 by the secondary transfer roller 3 to which a secondary transfer bias is applied from a power source.

  Thereafter, the recording medium 50 is passed through the fixing device 6 where the toner image is fixed to the recording medium 50 under heat and pressure.

  In the fixing device 6, when forming a color image, the surface temperature of the fixing roller 61 is controlled to the color image fixing temperature, and when forming a monochrome image formed only with a monochrome toner having a low melting temperature, the fixing roller 61 is used. The surface temperature of 61 is controlled to the monochrome image fixing temperature. This temperature control is performed by turning on and off a heater (not shown) in the fixing roller 61 while monitoring temperature information from a temperature sensor (not shown) that detects the temperature of the fixing roller 61 by the controller Cont.

  The recording medium 50 on which the toner image is fixed is discharged to the discharge tray 7 by the medium discharge roller pair 71 and the like. At this time, the switching claw 70 in front of the discharge roller pair 71 is in a position indicated by a solid line in FIG. 1, and directs the recording medium from the fixing device 6 to the discharge roller pair 71.

  In the mode in which images are formed on both sides of the recording medium 50, when the recording medium 50 image-formed on the first surface is discharged onto the tray 7 by the discharge roller pair 71, the rear end of the recording medium 50 is the switching claw 70. After passing, the discharge roller pair 71 is reversely rotated before reaching the discharge roller pair 71, and the switching claw 70 is rotated downward, whereby the recording medium 50 is fed to the recording medium conveyance path 9 for double-sided image formation. And is again supplied to the timing roller pair 4 by the conveying roller pair r1, r2, r3.

  Then, the toner image on the second surface on the intermediate transfer belt 2 is supplied again to the nip portion N as it arrives at the nip portion N, and the toner image is also transferred to the second surface and fixed by the fixing device 6. It is discharged to the tray 7.

  In each image forming unit, the toner remaining on the photoreceptor 11 after the primary transfer of the toner image is removed and cleaned by the cleaning device 16, and the secondary transfer residual toner on the intermediate transfer belt 2 is removed by the cleaning device 8. To be cleaned.

  In the image forming process described above, an image is formed on only one recording medium 50. However, it is also possible to sequentially form images on a plurality of recording media 50 sequentially. In any case, when one unit of image forming process (job) is set on the operation panel PA, the control unit Cont instructs the image forming process according to the setting.

In the image forming apparatus A, after the image forming process is completed, the deteriorated toner discharging process is also performed under the instruction of the control unit Cont.
The flowchart of FIG. 3 shows an outline of the operation of the control unit Cont.
When there is a print request by the print instruction key k1 on the operation panel PA, the control unit Cont performs print processing (image formation processing), and then performs post-printing processing such as deteriorated toner discharge processing and drive unit stop processing.

  FIG. 4 shows a deteriorated toner discharge processing operation by the control unit Cont. The toner discharge process is a process in which a waste toner pattern is formed on the photosensitive member 11 by a developing unit holding toner that has deteriorated due to fluctuations in electrical characteristics and the like, and the pattern is discharged onto the intermediate transfer belt 2 by a transfer process. It is.

  The toner discharging process is sequentially performed for each developing device 14 of each process cartridge. FIG. 4 shows the discharging process for one developing device. The same processing is sequentially executed for the other developing devices.

  Here, the “toner consumption rate” used in the following description will be described first. In this example, the toner consumption rate is calculated by the control unit Cont according to [(toner consumption amount in the integrated usage time of the developing device) / (integrated usage time of the developing device)]. As described above, the toner consumption rate depends on the toner consumption amount. When the toner consumption amount is large, the toner staying in the developing device for a long time is reduced, so that the deteriorated toner is reduced and the toner consumption amount is reduced. When the amount is small, the toner staying in the developing unit for a long time increases, and therefore the deteriorated toner increases. Therefore, the toner consumption rate is an index for determining whether or not the toner in the developing device is in a deteriorated state.

  By the way, in the image forming apparatus A, the electrostatic latent image is formed by scanning exposure on the photosensitive member 11 by the image exposure apparatus 13. The scanning exposure is performed by dot (point) exposure with a laser beam. Since the developing unit 14 performs reversal development in which toner is attached to the exposed portion, the number of exposure dots also represents the amount of toner consumption.

Therefore,
Toner consumption rate = [(toner consumption amount in integrated driving time of developing device) / (integrated driving time of developing device)] [(integrated number of dots in integrated driving time of developing device) / (integrated number of developing device) Drive time)] may be employed. The dot number information is input to the control unit Cont from a computer (not shown) or the like. Here, [(the accumulated number of dots in the accumulated driving time of the developing device) / (the accumulated driving time of the developing device)] is employed as the toner consumption rate.

The integrated driving time and toner consumption (total number of dots) of the developing device are updated by driving the developing device and toner consumption, and are stored in the nonvolatile memory medium m of the process cartridge including the developing device. The controller Cont can read the stored cumulative drive time and toner consumption (total number of dots) and calculate the toner consumption rate.
The integrated drive time and toner consumption (total number of dots) of the developing device may be stored in a non-volatile memory medium provided on the image forming apparatus main body side such as the control unit Cont.

  In the deteriorated toner discharging process, as shown in FIG. 4, first, a toner consumption rate in the developing device 14 is obtained (step S1). When the toner consumption rate is equal to or higher than a predetermined reference toner consumption rate (step S2), A waste toner pattern is not formed on the photoreceptor 11 on the assumption that the toner in the developing device is not deteriorated.

This process occurs when new toner is supplied from the toner supply hopper (not shown) to the developing device 14 and stays in the developing device for a long time when the toner consumption rate is equal to or higher than a predetermined reference toner consumption rate. This is based on the fact that there are few deteriorated toners with varying electrical characteristics and the like, and there is no problem in maintaining image quality without forming a waste toner pattern.
It should be noted that the “reference toner consumption rate” may be obtained in advance through experiments or the like in consideration of whether or not it can be assumed that there is no toner deterioration.

  However, if the toner consumption rate is smaller than the reference toner consumption rate, the toner that stays in the developing device 14 increases, and the deteriorated toner increases. Therefore, the toner in the developing device is regarded as deteriorated.

  By the way, if the number of sheets of the recording medium 50 in the image forming process is limited to some extent, the position of the toner consumption amount in the developing device 14 regardless of the position, size (particularly width) of the recording medium, the image position on the recording medium, and the like. The bias is negligible.

  Therefore, here, the “number of sheets to a certain extent” is obtained in advance by experiments or the like, and this is used as the reference number. When the toner consumption rate is smaller than the reference toner consumption rate in the determination in step S2, if the number of sheets passing through the recording medium is equal to or less than the reference number, the control unit Cont selects a predetermined predetermined waste toner pattern. Instructing the formation of the waste toner pattern on the photosensitive member 11 by the process cartridge including the developing device to which the deteriorated toner is discharged, and instructing the transfer of the pattern on the photosensitive member to the intermediate transfer belt 2 (Steps S3 and S5). Then, after the waste toner pattern on the intermediate transfer belt 2 is removed by the cleaning device 8 (step 5), the deteriorated toner discharging process is finished.

The number of recording media passed through can be counted by the control unit Cont, for example, when the timing sensor s1 detects the recording media.
In this example, the fixed waste toner pattern is a pattern in which the length in the main scanning direction and the length in the sub scanning direction are constant.

  However, when the number of sheets of the recording medium 50 exceeds the reference number, the control unit Cont selects a waste toner pattern corresponding to the recording medium, and instructs the process cartridge to form the waste toner pattern on the photoreceptor 11. Further, the transfer of the pattern on the photosensitive member to the intermediate transfer belt 2 is instructed (steps S3 and S4). Then, after the waste toner pattern on the intermediate transfer belt 2 is removed by the cleaning device 8 (step 6), the deteriorated toner discharging process is finished.

The waste toner pattern in step S4 will be described.
The waste toner pattern in step S4 is a pattern selected based on the image forming area distribution on the photoconductor 11 detected by the control unit Cont based on the position through which the recording medium 50 passes and the width of the recording medium 50. Specifically, it is a waste toner pattern in which more toner is discharged to the non-image forming area than the image forming area corresponding to the recording medium on the photoconductor 11.

This will be described by taking as an example the case where a postcard is adopted as a recording medium. As illustrated in FIG. 5, the control unit Cont sets an area 11 a on the photosensitive member 11 corresponding to the post position and width of the postcard as an image forming area, and both side areas (however, areas within the maximum developing width by the developing device 11). ) Are detected as non-image forming areas 11b and 11c, and based on the image forming area distribution, a waste toner pattern shown in FIG. 6 is selected, and the waste toner pattern is selected on the photoconductor 11 and eventually in the middle. The toner is discharged by being formed on the transfer belt 2.
The waste toner pattern is similarly formed on other types of recording media.

  As shown in FIG. 7, the smaller the toner consumption rate in the developing unit, the larger the amount of deteriorated toner. Therefore, it is preferable to discharge more toner in correspondence with that region, and accordingly, the sub-scanning direction of the waste toner pattern It is preferable to make the length longer. The pattern shown in FIG. 6 is based on this. In FIG. 6, the pattern portion 11a 'corresponds to the image forming area 11a, and the pattern portions 11b' and 11c 'correspond to the non-image forming areas 11b and 11c.

  In the pattern illustrated in FIG. 6, the pattern length in the sub-scanning direction is shortened for an area where the toner consumption rate in the developing device 14 corresponding to the image forming area 11 a is large, that is, an area where there is little deteriorated toner. , 11c corresponding to the region where the toner consumption rate is small, that is, the region where much deteriorated toner is present, the pattern length in the sub-scanning direction is made longer.

  Depending on the situation, toner discharge may not be performed on the image forming area 11a. Further, the toner consumption rate may be calculated separately for the non-image forming areas 11b and 11c, and the same toner discharging process may be performed.

  By forming such a waste toner pattern, the discharge of the deteriorated toner from the developing device 14 due to the formation of the waste toner pattern is suppressed from causing the normal toner discharge amount to be excessively increased or the deteriorated toner discharge amount to be decreased. Therefore, it is possible to perform the discharge with an appropriate toner discharge amount, and it is possible to suppress a decrease in image quality due to the deteriorated toner while suppressing wasteful discharge of normal toner.

  In the example described above, the control unit Cont obtains the image forming area distribution on the photoconductor 11 based on the through position and width of the recording medium. However, the image forming area distribution may be obtained as follows. That is, since the dot information in the image exposure is also input to the control unit Cont, the number of dots is received for each main scan, every page of the recording medium, or for each job, and provided in the control unit Cont. By counting the number of dots with a dot counter, the accumulation of image data position information on the photoconductor 11 is grasped, and based on this, the image forming area on the photoconductor 11 is grasped, and The image forming area distribution indicating the toner consumption rate may be obtained.

  For example, as shown in FIG. 8, the area on the photoconductor 11 is divided into band-like areas extending in the sub-scanning direction, and the toner consumption rate of the area is obtained from the number of dots included in each area, and each toner consumption is determined. The distribution of the image forming area indicating the rate is obtained.

  In the example of FIG. 8, the toner consumption rate in region X> the toner consumption rate in region Y> the toner consumption rate in region Z. If this is represented in a histogram, it will be as shown in FIG.

As shown in FIG. 10, the waste toner pattern based on the image forming area distribution obtained in this way has the length in the sub-scanning direction of the pattern portion X ′ corresponding to the area X having the largest toner consumption rate. Next, the length in the sub-scanning direction of the pattern portion Y ′ corresponding to the region Y is made longer, and the length in the sub-scanning direction of the pattern portion Z ′ corresponding to the region Z having the smallest toner consumption rate is made longer. The discarded toner pattern is obtained.
The toner consumption rate may be corrected according to the development characteristics.
The image forming area distribution may be an area obtained by further dividing the band area in the sub-scanning direction.

  Although the tandem type color image forming apparatus has been described above, the present invention can be applied to other types of color image forming apparatuses and also to monochrome image forming apparatuses.

  According to the present invention, the discharge of the deteriorated toner from the developing device due to the formation of the waste toner pattern is performed with an appropriate toner discharge amount that prevents the normal toner discharge amount from being excessively increased or the deteriorated toner discharge amount from being decreased. Therefore, the present invention can be used to provide an image forming apparatus that can suppress a decrease in image quality due to deteriorated toner while suppressing wasteful discharge of normal toner.

1 is a diagram illustrating a schematic configuration of an example of an image forming apparatus according to the present invention. FIG. 2 is a block diagram illustrating an outline of a control circuit of the image forming apparatus illustrated in FIG. 1. It is a flowchart which shows the outline of operation | movement of a control part. 10 is a flowchart showing an example of deteriorated toner discharge processing. FIG. 6 is a diagram illustrating an image forming region distribution on a photoconductor according to a through position and a width of a recording medium. It is a figure which shows the example of a waste toner pattern. FIG. 5 is a diagram illustrating a basic concept of a relationship between a toner consumption rate of each region in a developing device and a length of a waste toner pattern in a sub-scanning direction. It is a figure which shows the example of image formation area distribution based on the image data position information on a photoconductor. FIG. 9 is a histogram showing a toner consumption rate for each divided region in the case of the image forming region distribution shown in FIG. 8. FIG. It is a figure which shows the other example of a waste toner pattern.

Explanation of symbols

A Printer Y Yellow image forming unit M Magenta image forming unit C Cyan image forming unit K Black image forming unit YC, MC, CC, KC Process cartridge 11 Photoconductor 12 Charger 13 Image exposure device 14 Developer 141 Developer roller m Non-volatile Memory medium 15 Primary transfer roller 16 Cleaning device 2 Intermediate transfer belt 21 Driving roller 22 Opposing roller 3 Secondary transfer roller 4 Timing roller pair s1 Timing sensor 5 Recording medium storage cassette 51 Medium drawing roller 50 Recording medium 6 Fixing device 61 Fixing roller 62 Pressure roller 71 Medium discharge roller pair 7 Medium discharge tray 70 Switching claw 8 Cleaning device 9 Recording medium conveyance path r1 to r3 for double-sided image formation Recording medium conveyance roller pair PA Operation panel k1 Print instruction key Ke Key group Dp Liquid crystal display Part

Claims (6)

An electrostatic latent image corresponding to a target image formed on the electrostatic latent image carrier is developed with a developing device to form a toner image, and image forming processing is performed to transfer and fix the toner image on a recording medium. An image forming apparatus capable of forming a waste toner pattern image carrier and a waste toner pattern forming unit including the developer for forming the waste toner pattern by the toner in the developer on the waste toner pattern image carrier. An image forming apparatus,
A continuous sheet number detecting means for detecting a continuous sheet number of recording media in the image forming process;
Image forming area distribution detecting means for detecting an image forming area distribution on the electrostatic latent image carrier in the image forming process;
Toner deterioration determining means for determining whether or not the toner in the developing device is in a deteriorated state;
The waste toner pattern forming unit forms a waste toner pattern on the waste toner pattern image carrier when the toner deterioration determining unit determines that the toner in the developing device is in a deteriorated state, and forming the waste toner pattern At this time, an appropriate toner discharge amount for discharging deteriorated toner is determined according to the continuous sheet number of the recording medium detected by the continuous sheet number detection unit and the image formation region distribution detected by the image formation region distribution detection unit. An image forming apparatus for forming a waste toner pattern to be achieved. When forming the waste toner pattern, the waste toner pattern forming unit applies a predetermined constant waste toner pattern when the continuous number of sheets of the recording medium detected by the continuous sheet number detecting unit is equal to or less than a predetermined reference number. When it is formed and exceeds the reference number, more toner is discharged to the non-image forming area than the image forming area on the electrostatic latent image carrier based on the image forming area distribution detected by the image forming area distribution detecting means. The image forming apparatus according to claim 1, wherein a waste toner pattern is formed. The image forming area distribution detecting means is arranged on the electrostatic latent image carrier based on a position and width on the electrostatic latent image carrier corresponding to a passing position and a passing width of the recording medium in the image forming process. 3. The image forming apparatus according to claim 1, which is means for detecting an image forming area distribution. The image forming region distribution detecting means is provided on the electrostatic latent image carrier for image data for forming an electrostatic latent image corresponding to a target image on the electrostatic latent image carrier in the image forming process. The image forming apparatus according to claim 1, wherein the image forming area distribution is detected by accumulating position information. The toner deterioration determining means determines that the toner in the developing device has deteriorated when the toner consumption rate in the developing device is smaller than a predetermined reference consumption rate, and The image forming apparatus according to claim 1, wherein the toner in the developing unit is determined not to be deteriorated. 6. The image forming apparatus according to claim 5, wherein the toner consumption rate is [(toner consumption amount in the integrated driving time of the developing device) / (integrated driving time of the developing device)].