JP2016161618A - Image forming device and process cartridge used for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of correctly obtaining a waste toner amount including a fogging toner and a process cartridge used therefor.SOLUTION: An image forming device includes: an image carrier; charging means for charging a surface of the image carrier; exposure means for forming an electrostatic latent image on the surface of the charged image carrier; a developer carrier for developing the electrostatic latent image by a toner; transfer means for transferring a toner image formed on the image carrier to a transfer body; recovery means for recovering a waste toner generated accompanied with an image formation; and an acquisition part for acquiring the waste toner amount. A potential difference between a charging potential of the image carrier and a developing potential of the developer carrier is made a potential difference for suppressing the transferring of a fogging toner adhered on a non-image portion of the image carrier to the transfer means. The acquisition part acquires the toner amount not transferred to the transfer means from among the toners developed into the image carrier with respect to the image part of the image carrier and the toner amount of the fogging toner with respect to the non-image part as the waster toner amount.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image forming apparatus using an electrophotographic system or an electrostatic recording system, and relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, and a process cartridge used therefor.

  In conventional image forming apparatuses such as copying machines and printers, an electrophotographic recording system using electrostatic toner, an electrostatic recording system, and the like are often used.

  In determining the replacement timing of the waste toner collection container loaded in the image forming apparatus such as an electrophotographic apparatus, the waste toner full state of the waste toner container may be detected (hereinafter referred to as waste toner full tank detection). is necessary. For this reason, there is generally known one that uses a sensor for detecting the fullness of waste toner.

  Patent Document 1 is provided with a sensor that detects waste toner full in a waste toner collection container, and after detection by this sensor, printing is prohibited when the pixel count value of image data reaches a predetermined value. Is disclosed.

  In addition, with the recent miniaturization and cost reduction, the technology for reducing the size and the common technology have been actively adopted. As part of this, common use of high pressure, sensorless, and the like are performed, and among them, a waste toner full sensor is not provided, and a waste toner amount is calculated from a pixel count value of image data. Japanese Patent Application Laid-Open No. 2004-228561 discloses a method in which the accumulated amount of waste toner is corrected based on the consumed toner amount, transfer efficiency, and environmental information, and the pixel count is calculated without using the waste toner full sensor.

JP-A-8-1115014 JP 2003-316224 A

  However, in the above prior art, the developing potential of the toner on the photosensitive drum varies depending on the surface potential of the photosensitive drum due to the operating environment temperature and humidity and the life of the cartridge. Control was difficult. The fog toner includes toner transferred from the photosensitive drum to the recording medium (polarity opposite to the transfer bias) and toner not transferred (same polarity as the transfer bias). Until now, the amount of fog toner as described above has not been accurately calculated. Therefore, waste toner overflows from the waste toner container before full detection of waste toner, or full detection is performed with a smaller amount than waste toner full. There was a possibility.

  In addition, when high voltage (high voltage) is common to each station due to miniaturization and cost reduction, the potential adjustment for each station cannot be performed only with high voltage, and fog toner control is not possible. It was even more difficult.

  An object of the present invention is to provide an image forming apparatus capable of correctly acquiring the amount of waste toner including fog toner and a process cartridge used therefor.

  In order to achieve the above object, an image forming apparatus according to the present invention forms an electrostatic latent image on an image carrier, charging means for charging the surface of the image carrier, and the charged surface of the image carrier. Exposure means for developing, a developer carrier for developing the electrostatic latent image with toner, a transfer means for transferring a toner image formed on the image carrier to a transfer target, and waste toner generated during image formation A collecting means for collecting the amount of waste toner, and an acquisition unit for acquiring the amount of the waste toner, and the potential difference between the charging potential of the image carrier and the developing potential of the developer carrier is set to A potential difference that suppresses transfer of fog toner adhering to the image portion to the transfer means is set, and the acquisition portion is the transfer portion of the toner developed on the image carrier for the image portion of the image carrier. The amount of toner that is not transferred to the non-image area In its toner amount of the fog toner, and acquires as the amount of the waste toner.

  The process cartridge according to the present invention includes an image carrier, a charging unit that charges the surface of the image carrier, and a developer carrier that develops an electrostatic image of the image carrier with toner. The potential difference between the charging potential of the image carrier and the development potential of the developer carrier is a potential difference that suppresses the transfer of fog toner adhering to the non-image portion of the image carrier, and The amount of toner that is not transferred among the toner developed on the image carrier for the image portion, and the amount of waste toner for the non-image portion is the amount of waste toner. And

  According to the present invention, the amount of waste toner including fog toner can be acquired correctly.

1 is a schematic cross-sectional view illustrating a configuration of an image forming apparatus according to a first embodiment of the present invention. 1 is a block diagram illustrating an operation and a configuration of an image forming apparatus according to a first embodiment. 2 is a schematic cross-sectional view of a process cartridge in the image forming apparatus according to the first embodiment. FIG. (A), (b) is a figure which shows the primary transfer efficiency coefficient and primary retransfer efficiency coefficient for acquiring the waste toner amount which concerns on 1st Embodiment. 6 is a flowchart for obtaining a waste toner amount in the first embodiment. (A), (b) is a figure which shows the fog correction factor and the fog correction environment coefficient for acquiring the amount of waste toner which concern on 1st Embodiment. (A), (b) is a diagram showing the photosensitive drum surface potential Vd, the developing bias Vdc, and their potential difference Vback according to the first embodiment in the initial stage of use and during use. FIG. 6 is a diagram showing Vback dependency on the fogging amount of the fog toner at the initial use stage and the final use stage of the cartridge in the first embodiment. FIG. 6 is a diagram showing Vback dependency on the fogging amount of the fog toner for each use environment of the cartridge in the first embodiment. FIG. 6 is a diagram illustrating toner movement when Vback is small (narrow) in the first embodiment. FIG. 6 is a diagram illustrating toner movement when Vback is large (wide) in the first embodiment. FIG. 5 is a diagram illustrating a relationship between Vback and fog toner transfer efficiency in the first embodiment. It is the schematic which shows the image forming apparatus which concerns on the 2nd Embodiment of this invention containing the structure of charging high voltage | pressure. (A), (b) is a diagram showing the photosensitive drum surface potential Vd, the developing bias Vdc, and the potential difference Vback according to the second embodiment in the initial stage of use and during use. (A), (b) is a diagram showing the photosensitive drum surface potential Vd, the developing bias Vdc, and their potential difference Vback according to the third embodiment of the present invention at the initial stage of use and during use. It is a schematic sectional drawing which shows the structure of the image forming apparatus which concerns on the 4th Embodiment of this invention.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<< First Embodiment >>
(Image forming device)
The configuration and operation of the image forming apparatus according to the first embodiment of the present invention will be described with reference to FIG. The image forming apparatus according to the present exemplary embodiment includes first, second, third, and fourth toner images for forming yellow (Y), magenta (M), cyan (C), and black (K) toner images, respectively. Station (image forming station, image forming unit) a, b, c, d.

  Since the configuration and operation of each station are substantially the same except that the color of the toner used is different, the first station a will be described in the following description. In the following description, if there is no particular distinction, the subscripts a, b, c, and d given to the reference numerals are omitted to indicate that they are elements provided for any color, and the overall description is omitted. It may be explained in

(Process cartridge)
In the present embodiment, as a configuration of each station, as shown in FIG. 3, a process cartridge that is detachably attached to the apparatus main body of the image forming apparatus is provided. Here, the process cartridge is a cartridge including at least an image carrier such as an electrophotographic photosensitive drum, and further integrally including an image carrier and process means acting on the image carrier.

(Operation of image forming apparatus)
The first station a of the image forming apparatus according to the present embodiment is provided with a drum-shaped electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) 1a as an image carrier. It is driven to rotate at a peripheral speed (process speed). Here, the first station a corresponds to the most upstream image forming unit.

  In this rotating process, the photosensitive drum 1a is uniformly charged to a predetermined polarity and potential by a charging roller 2a as a charging unit, and then subjected to image exposure by an exposure unit 3a. Thereby, an electrostatic latent image (electrostatic image) corresponding to the yellow color component image of the target color image is formed on the surface of the photosensitive drum 1a. Next, the electrostatic latent image is developed with toner by the first developing device 4a at the development position, and visualized as a toner image (yellow toner image).

  The intermediate transfer member 10 serving as a transfer target has a substantially same peripheral speed as that of the photosensitive drum 1a in a direction of moving in the same direction as the rotation direction of the photosensitive drum 1a at the contact portion between the photosensitive drum 1a and the intermediate transfer member 10. Driven by rotation. The first to fourth stations a to d are arranged side by side along the rotation direction of the intermediate transfer body 10.

  The yellow toner image formed on the photosensitive drum 1a is transferred onto the intermediate transfer body 10 by the primary transfer voltage applied to the primary transfer roller 14a from the primary transfer high-voltage power supply 15 in the process of passing through the primary transfer portion. (Primary transfer). The toner remaining on the surface of the photosensitive drum 1a is cleaned and removed (collected) by the cleaning device 5a.

  Thereafter, a magenta toner image of the second color, a cyan toner image of the third color, and a black toner image of the fourth color are formed in the same manner, and the primary transfer is sequentially performed on the intermediate transfer body 10 in each primary transfer portion. Thus, a composite color image corresponding to the target color image is obtained.

  Thereafter, the four color toner images on the intermediate transfer body 10 are supplied with a recording material by the secondary transfer voltage applied to the secondary transfer roller 20 by the secondary transfer high-voltage power source 21 in the process of passing through the secondary transfer portion. Batch transfer is performed on the surface of the recording material P fed by the apparatus 8 (secondary transfer).

  Thereafter, the recording material P carrying the four color toner images is introduced into the fixing device 7 where the four color toners are melted and mixed and fixed to the recording material P by being heated and pressurized. A full-color print image is formed by the above image forming operation.

  The secondary transfer residual toner remaining on the surface of the intermediate transfer member 10 after the secondary transfer is collected by the transfer cleaning device 16 on the intermediate transfer member 10. The transfer cleaning device 16 may use a conductive roller or a conductive brush in order to simultaneously collect the primary transfer of toner.

(Explanation of latent image / development / primary transfer operation)
Hereinafter, operations performed from the latent image to the primary transfer will be described in detail. First, in order to uniformly charge the surface of the photosensitive drum 1, a predetermined DC voltage is applied to the charging roller 2 serving as a charging unit by a high voltage power source provided inside the image forming apparatus. At this time, a voltage of about −1100 V is applied to the photosensitive drum 1 by the charging roller 2.

  Subsequently, in order to form an electrostatic latent image on the surface of the photosensitive drum 1, an LED or a laser as a light emitting element modulated by image information sent from an information processing device (not shown) is applied to the photosensitive drum 1 by the optical means 3. Irradiate. The optical means 3 can use either LED light or laser light.

  Next, in order to make the electrostatic latent image visible, a predetermined DC voltage is applied to the developing device 4 by a high voltage power source provided inside the image forming apparatus. As a result, the negatively chargeable non-magnetic one-component developer T (hereinafter referred to as “toner”) contained in the developing device 4 is developed on the surface of the photosensitive drum 1 to form a visible image (hereinafter referred to as “toner image”). Form).

  At this time, a developing bias (Vdc) is applied from the developing high pressure 30 to the developing roller 6 as a developer carrying member. By setting such a potential, the negative toner is not attached to the unexposed portion, which is the surface potential (Vd) of the charged photosensitive drum 1, and is attached to the exposed portion (Vl) by electrostatic force. Become. Vl is set to about -150V. Vdc and Vd will be described in detail later.

  Next, in order to transfer the toner image on the surface of the photosensitive drum 1 to the intermediate transfer member 10, a predetermined voltage is applied to the transfer material 14 serving as a transfer unit by a high-voltage power source, thereby transferring the toner image on the surface of the photosensitive drum 1 to the intermediate transfer body 10. Transfer to the body 10. At this time, most of the toner image is transferred to the intermediate transfer member 10, but part of the toner image remains on the photosensitive drum 1 without being completely transferred to the intermediate transfer member 10.

  The remaining toner is scraped off (collected) as waste toner by a cleaning blade 9 which is an image carrier cleaning means in contact with the photosensitive drum 1, and is accumulated in the cleaning device 5, whereby the surface of the photosensitive drum 1 is refreshed. The Thereafter, image formation is continued by repeating the same process.

(Control part)
FIG. 2 is a block diagram of a control unit (image forming system) for explaining the operation and configuration of the image forming apparatus of the present embodiment. The host computer 200 is responsible for issuing a print command and transferring the image data of the print image to the interface board 151 installed in the image forming apparatus. The interface board 151 converts image data from the host computer 200 into exposure data, and issues a print command to the DC controller 150 serving as a control unit. The DC controller 150 operates with power supplied from the low-voltage power supply 152. Upon receiving a print command, the DC controller 150 starts an image forming sequence while monitoring the state of various sensors 153.

  The DC controller 150 is equipped with a CPU, a memory, etc., and performs a pre-programmed operation. Specifically, the operation of various driving devices 154 such as a main motor, a developing device 4 and a driving device for the photosensitive drum 1 is controlled. At the same time, the exposure means 3 is controlled so that the amount of exposure light is stabilized. Further, the power control device 155 connected to the fixing device 7 is controlled to perform power control so that the temperature of the fixing device 7 maintains a predetermined temperature.

  Various functional components that control image formation are connected to the high-voltage power supply 160. For example, the charging rollers 2a to 2d provided in each station receive a high voltage from the high voltage power supply 160 and come into contact with the photosensitive drums 1a to 1d of each station, so that the surfaces of the photosensitive drums 1a to 1d are uniform. It plays a role of charging to a certain potential. This charging potential is controlled by the DC controller 150 controlling the high voltage generated in the high voltage power supply 160.

  Similarly, a high voltage is supplied from a high voltage power supply 160 to the developing rollers 6 a to 6 d and the primary transfer rollers 14 a to 14 d and the secondary transfer roller 20 provided in each station. The applied voltage and applied current at this time are controlled by the DC controller 150.

(Memory mechanism and pixel count)
As shown in FIG. 3, the process cartridge is provided with a memory 23 as storage means. As the memory 23, for example, an arbitrary form such as a contact nonvolatile memory, a contactless nonvolatile memory, a volatile memory having a power source, or the like can be used. In the present embodiment, a non-contact nonvolatile memory 23 is mounted on the process cartridge as a memory. The non-contact non-volatile memory 23 has an antenna (not shown) as information transmission means on the memory side, and can read and write information by wirelessly communicating with the CPU 22 provided in the image forming apparatus main body. .

  That is, in this embodiment, the CPU 22 includes a control unit, a calculation unit, a storage unit (ROM), a clock, and the like, and further includes a function for reading and writing information to the memory 23 via information transmission means on the apparatus body side. ing. The CPU 22 also functions as an acquisition unit that acquires a waste toner amount, which will be described later, and a counting unit that performs pixel count (image signal count).

  In the memory 23, at least the developer consumption amount by detecting the remaining amount of developer, the number of image formation (printing), and / or the integrated count number (pixel count integrated number) of individual image signals forming the dots of the image forming image. ) Is stored. Then, it is possible to estimate the consumed toner amount (developer amount) from the stored number of images and the integrated pixel count.

  Here, the pixel count is to count individual image signals that form image dots (hereinafter, dots) of an image to be formed. The image forming apparatus according to this embodiment is a laser beam printer of 600 dpi (dot / inch) as an example. Further, the image formable area of letter size paper (216 mm × 279 mm) is 204 mm × 269 mm, which is 4878 dots × 6420 dots in terms of dots.

  In the present embodiment, image data to be printed out from the host computer 200 (FIG. 2) is sent to the CPU 22 (FIG. 3) as an electrical signal. The image data may be sent from, for example, an image reading unit provided in the image forming apparatus main body.

  The CPU 22 converts this image data into a video signal for each scanning line, and creates a laser drive signal according to the video signal. Then, the photosensitive drum 1 is irradiated by controlling light emission / extinction of a laser unit (not shown). When the video signal is sent to the laser unit as a signal for laser emission, a horizontal synchronizing signal (BD signal) comes to the head of the scanning line. Since the video signal comes after a certain time from the BD signal, the start position of the video signal can be confirmed by detecting the BD signal.

  The count (count) of dots in each area starts from zero at regular intervals, but the count result is sent to a dot number storage memory (not shown) and stored for each counted area. In this way, the number of dots in the laser scanning direction in each region can be counted. Further, the number of scanning lines can be known by counting BD signals. In this way, the number of dots for each region is counted and stored in the dot number storage memory.

(Acquire (calculate) the amount of waste toner related to the image area)
Next, a method for acquiring (calculating) the amount of waste toner related to the image portion will be described. For the calculation of the amount of waste toner in the present embodiment, a pixel counting unit (pixel counter) that can count the number of pixels emitted by the exposure unit 3 is used.

  First, the toner amount actually used for image formation (developed toner amount) is calculated (acquired) as a predicted value. As the amount of toner required to develop a certain image, the amount of toner used per pixel count is stored in the CPU 22 from the number of pixels emitted by the exposure means 3. Then, the toner usage amount is estimated (acquired) from the integrated value of the stored value and the number of light emitting pixels counted by the pixel counter.

  However, not all 100% of the toner usage calculated as actually used is transferred / fixed on the recording medium, and toner loss occurs in the process until fixing. Therefore, the amount of waste toner is a value obtained by multiplying the amount of toner actually used (developed) by a certain ratio. The amount of toner used and the amount of toner used for the number of light-emitting pixels when not used for image formation are calculated assuming various situations, and the waste toner is stored in the waste toner container of each station sequentially. Accumulated.

  Toner loss includes primary transfer residue and primary retransfer, toner recovery when a jam occurs, toner recovery when a misprint occurs, and fogging. The use of toner for the number of light emitting pixels in a case where it is not used for image formation includes calibration and toner purge.

  The calculation of the toner affected by the primary transfer residue and the primary retransfer can be performed by providing the CPU 22 with a coefficient of transfer efficiency in advance. The amount of toner used corresponding to the actual pixel count is multiplied by a coefficient of transfer efficiency defined under various conditions such as the usage environment and usage history of the photosensitive drum 1. As a result, the amount of toner used can be considered separately as the amount transferred to the intermediate transfer member 10 and the amount remaining on the photosensitive drum 1.

  FIG. 4A shows the primary transfer efficiency coefficient, and FIG. 4B shows the primary retransfer efficiency coefficient. The primary transfer efficiency is a value indicating the ratio of primary transfer of the toner of its own color, and the primary retransfer efficiency is the rotation direction of the intermediate transfer member 10 for each color toner transferred onto the intermediate transfer member 10. On the other hand, this is a value indicating the rate of transfer again onto the photosensitive drum 1 existing downstream from the station.

  As an example, a case where image formation is performed at Y of the first station will be described. 4A and 4B, the primary transfer efficiency of Y is 97.5%, and the primary retransfer efficiency is 5%. Here, if the amount of toner developed on the photosensitive drum 1 of the first station (corresponding to the image portion) is X, the amount of waste toner collected (waste toner amount) at each station is as follows for the image portion. Become.

  First, in the first station, toner that is not primarily transferred (2.5% of X) is collected as waste toner by the cleaning device 5, and is expressed as (2.5 / 100) X. In the second station, the toner (97.5% of X) primarily transferred onto the intermediate transfer body 10 in the first station is retransferred by 5% by the photosensitive drum 1 in the second station. .5 / 100) X × (5/100).

  In the third station, since retransfer efficiency is considered for the toner that has passed through the second station, (97.5 / 100) X × (95/100) × (5/100). In the fourth station, similarly, (97.5 / 100) X × (95/100) × (95/100) × (5/100).

  When a jam occurs, a misprint occurs, calibration, and toner purge are not output to the outside as an image. Therefore, the amount of waste toner may be added according to the pixel count in which dots are actually counted.

(Flow chart for calculating the amount of waste toner relating to the image portion)
FIG. 5 is a flowchart of the waste toner amount calculation (acquisition) process for the image portion. First, after the main body operation is started in S1, a printing start operation is started from the DC controller 150 in S2. In S3, a TOP output signal for judging the image formation output timing is output from the BD signal. In S4, the video signal input from the DC controller 150 is measured using the pixel count measuring means.

  Thereafter, in S5, the image end information is received, and the amount of waste toner is calculated by the calculation means from the count value measured by the pixel count means, and is summed for each image image, and stored in the memory 23 via the CPU 22. The memory 23 mounted on the process cartridge stores an accumulated value of accumulated waste toner amount and a predetermined threshold value. The threshold is set to an amount of waste toner so that the waste toner does not overflow from the cleaning device 5.

  In S6, an integrated value obtained by adding the waste toner amount calculated in the current image formation to the integrated value so far is calculated. The calculation of the amount of waste toner collected by the cleaning device 5 with respect to the image portion is specifically performed using the transfer efficiency and retransfer efficiency in the primary transfer portion. The non-image part will be described in detail later.

  When the threshold value and the integrated value are compared in S7 of FIG. 5 and it is determined that the integrated value exceeds the threshold value (S7-YES), the display unit (not shown) provided in the image forming apparatus is discarded in S8. Notify that the toner is full. After notification or when the threshold is not exceeded, the operation is terminated in S9. Then, this series of operations is sequentially performed in Y, M, C, and K.

(Calculation of waste toner amount for fog toner in non-image area)
Regarding the acquisition of the amount of waste toner, it is necessary to add not only the amount of waste toner related to the image portion described above but also the amount of waste toner related to fog toner in the non-image portion. Accordingly, calculation (acquisition) of the waste toner amount related to the fog toner in the non-image portion will be described. The fog toner refers to toner that is not actually printed with dots, but is unintentionally transferred from the developing roller 6 onto the photosensitive drum 1 due to the potential difference between the photosensitive drum 1 and the developing bias and the polarity of the toner. Therefore, although the toner consumption and the amount of waste toner change in the fog toner, the pixel count is not integrated as it is.

  In other words, it is not sufficient to calculate the amount of waste toner related to the image portion through the pixel count. To calculate the correct amount of waste toner, the amount of waste toner related to the non-image portion is further calculated and added. It is necessary to correct misalignment due to fog toner. This will be specifically described below.

  First, the white part pixel count as the number of pixels in the non-image part is calculated. Here, the pixel count of the white portion is obtained by excluding the pixel count detection number counted when the image is actually formed with respect to the total pixel count per sheet. Specifically, it is calculated as the following formula 1.

(Formula 1)
White part pixel count = total pixel count per sheet-pixel count detection
Subsequently, the toner amount (fogging toner amount) of the non-image portion toner (fogging toner) on the photosensitive drum 1 is calculated as in the following Equation 2.

(Formula 2)
Fog toner amount = white area pixel count × (fogging correction rate (%) / 100) × (fogging environmental coefficient (%) / 100)
The fog correction rate in Equation 2 is obtained by correcting the fog characteristics that differ for each color, and is obtained by applying a color to the fog correction rate table shown in FIG. Further, the fog environment coefficient is obtained by correcting the fog characteristic that varies depending on the environment, and is obtained by applying the color and the environment to the fog environment coefficient table shown in FIG. 6B registered in advance.

  The fogging environment coefficient of this embodiment is set to L / L (15 ° C./10%), N / N (23 ° C./50%), and H / H (30 ° C./80%). Linearly interpolates with moisture content. In addition, each value is memorize | stored in the non-contact non-volatile memory 23 (FIG. 3).

(Waste toner full tank detection)
Hereinafter, consideration of waste toner (fogging correction) related to the fog toner in the non-image area in the waste toner full tank detection, which is a feature of the present embodiment, will be described. In this embodiment, the potential difference ΔV (= Vback) between the surface potential Vd of the photosensitive drum 1 and the developing bias (developing potential) Vdc is set to a predetermined value, and this is controlled to be constant, thereby controlling the recovery of the fog toner. ing. That is, a potential difference that suppresses the transfer of the fog toner adhering to the non-image portion of the photosensitive drum 1 by the transfer means is controlled to be constant.

  For the non-image portion, the amount of toner that is not transferred by the transfer unit among the fog toner (in the present embodiment, matches the fog toner amount) is set as the amount of waste toner. On the other hand, for the image portion, the amount of toner developed on the photosensitive drum 1 that is not transferred by the transfer means is the amount of waste toner. The waste toner full tank detection will be specifically described below.

  Usually, the surface potential Vd of the photosensitive drum 1 changes sequentially due to the use situation and the influence of the transfer bias. Therefore, the charging bias and the developing bias are appropriately changed. Each bias value has for each environment (temperature / humidity) and is stored in the CPU 22. Specifically, L / L (15 ° C / 10%), N / N (23 ° C / 50%), and H / H (30 ° C / 80%) are set, and the amount of water between the environments Use linear interpolation. The environmental information and usage status are read from the non-contact nonvolatile memory 23 and changed.

  FIG. 7A shows the potential relationship at the initial stage of use in this embodiment. As shown in the figure, the actually used potentials were Vd = −510V, Vdc = −380V, and Vback = 130V in the initial stage of use. As the user uses it, the discharge start voltage changes as the film thickness of the photosensitive drum 1 is reduced and thinned. When the same charging bias is selected, the surface of the photosensitive drum 1 is thinner when the photosensitive drum 1 is thinner. The potential Vd increases in absolute value. Therefore, the developing bias is increased in absolute value accordingly, and Vback is kept constant at the above value (130 V).

  The charging bias and the developing bias have a table according to the film thickness of the photosensitive drum 1, read values from the non-contact nonvolatile memory 23, and appropriately change them. FIG. 7B shows the potential relationship when the film thickness of the photosensitive drum 1 changes due to the use of the process cartridge. From the comparison between FIGS. 7A and 7B, it can be seen that Vback is always constant.

  The fogging amount of the toner in the non-image part used in this embodiment was confirmed while changing Vback (FIGS. 8 and 9). FIG. 8 shows a comparison between the initial stage and the end stage of cartridge use, and FIG. 9 shows a result of comparison for each environment. From these figures, it can be seen that the fog toner is bottom in the vicinity of Vback = 100 V, that is, the fog toner is least generated in any situation. On the contrary, the amount of fog toner tends to increase regardless of whether it is small or large with respect to Vback = 100V. Conventionally, since the amount of fog toner is desired to be as small as possible from the viewpoint of toner consumption, Vback is set to the bottom (100 V).

  Next, the Vback dependency of the polarity of the fog toner in the non-image area will be described. When Vback is smaller than 100V, the fog toner tends to increase as shown in FIGS. Here, as shown in FIG. 10, when Vback is small, the proportion of the negatively charged toner on the surface potential Vd of the photosensitive drum 1 that moves with the developing roller 6 and the toner with weak adhesion increases, and the fog toner and Become. FIG. 10 shows the state of toner movement when Vback = 50V.

  When Vback = 100V, if fog toner is present on the photosensitive drum 1, the fog toner is intermediate transferred by primary transfer using a transfer means to which a positive bias is applied to transfer the developed toner. Mostly transferred to the body 10. At this time, since the waste toner is not collected by the cleaning device 5, there is no need to integrate the toner. However, when the fog toner is almost transferred as described above, the fog toner is transferred onto the recording medium, and an image that is disadvantageous to the user is output. That is, although the calculation accuracy of the waste toner full detection is improved, the image is affected.

  On the other hand, in the configuration of the present embodiment in which Vback is greater than 100 V, the toner charged to the weak negative as described above is not developed on the photosensitive drum 1. However, toner that is reversed (having positive polarity) among the toner carried on the surface of the developing roller 6 is selectively developed on the photosensitive drum 1. As a diagram for explaining the above phenomenon, FIG. 11 shows, as an example, a state of toner movement when Vback = 200V.

  Since the positive fogging toner has the same polarity as the polarity of the primary transfer bias, it is collected by the cleaning device 5 while being almost carried on the surface of the photosensitive drum 1 even after the primary transfer. . Therefore, the toner is hardly transferred onto the intermediate transfer body 10.

  Here, the primary transfer ratio (fogging transfer efficiency) of the fog toner in the non-image portion with respect to Vback is shown in FIG. In general, it can be seen that, with Vback = 100V as a boundary, the fog toner is divided into a case where it is not primarily transferred and a case where it is not. In the vicinity of Vback = 100V, the ratio of toner to be transferred is unclear, but in the range shown below, which is larger than Vback = 100V, it has been confirmed that almost no primary transfer is performed (almost 100%).

  That is, if the Vback is 120 V or more, the transfer efficiency is considered to be 5% or less (and if the Vback is 130 V or more, the transfer efficiency is considered to be 3% or less). When it is considered that the fog transfer efficiency is approximately 0%, the above Vback may be used regardless of the fog amount (FIGS. 8 and 9).

  When the fog transfer efficiency is considered to be not approximately 0%, in view of the condition that the product of the fog transfer efficiency (FIG. 12) and the fog amount (FIGS. 8 and 9) is small, the Vback is 120V or more and 250V. It may be set below (further, 130V or more and 200V or less). Furthermore, it may be 130 V or more and 150 V or less.

  From the above results, if the region larger than 100 V described above is adopted as Vback, there is no image defect (there is almost no transfer of fog toner), and the amount of fog toner is directly used as the amount of waste toner (waste toner amount). Calculation can be performed. For this reason, it contributes to the improvement of the waste toner full tank detection accuracy.

  On the other hand, if waste toner detection is performed at Vback = 100 V as in the prior art, the transfer efficiency can be accurately estimated because the polarity of the toner with respect to Vd is not determined when calculating the waste toner of the fog toner. Therefore, it is not possible to perform the optimal waste toner full tank detection.

  Here, the ratio of occurrence of fog toner varies depending on the environment as shown in FIG. Therefore, the amount of waste toner collected by the cleaning device 5 as the amount of fog toner varies depending on the environment. For this reason, the fog correction rate in FIG. 6A and the fog environment correction coefficient in FIG. 6B (assuming that the temperature and moisture content (g / cm ^ 3) are obtained by an environmental sensor not shown) are acquired. .

  As described above, the amount of fog toner is obtained from the white area pixel count number, the fog correction rate, and the fog environment correction coefficient for the non-image portion (Equation 2). When the fog toner is transferred, the fog toner is related. The following considerations are necessary for obtaining the predicted amount of waste toner. That is, in order to obtain the estimated amount of waste toner, it is necessary to further consider primary transfer efficiency and primary retransfer efficiency. In the following, an expression for obtaining a predicted amount of waste toner in the first station that does not consider primary retransfer and the second station that considers primary retransfer of toner transferred from the first station to the intermediate transfer member 10 is shown. Indicates.

(Formula 3: First Station)
Expected amount of waste toner (K1) = white pixel count × (fogging correction rate (%) / 100) × (fogging environmental coefficient (%) / 100) × ((100-1 primary transfer efficiency) (%) / 100)
The predicted amount (K1) of waste toner represented by Equation 3 corresponds to the amount of fog toner that is not transferred in the non-image portion of the photosensitive drum 1a.

(Formula 4: Second Station)
Expected amount of waste toner (K2) = {second station white area pixel count number × (second station fog correction rate (%) / 100) × (second station fog environment coefficient (%) / 100) × ((100 -Primary transfer efficiency of second station) (%) / 100)} + {first station white area pixel count number x (first station fog correction rate (%) / 100) x (first station fog environment coefficient ( %) / 100) × (first station primary transfer efficiency (%) / 100) × (second station primary retransfer efficiency (%) / 100)}
The estimated amount (K2) of waste toner expressed by Equation 4 corresponds to the amount of fog toner in the non-image portion of the photosensitive drum 1b existing on the photosensitive drum 1b. That is, the added amount of the fog toner amount not transferred in the non-image portion of the photosensitive drum 1b and the fog toner amount transferred in the non-image portion of the photosensitive drum 1a that is transferred to the photosensitive drum 1b after being transferred. It becomes.

  Here, if the configuration is such that the fog toner is not primarily transferred by adjusting Vback, when obtaining the estimated amount of waste toner relating to the fog toner in the non-image area, as shown in FIGS. There is no need to consider transfer efficiency and retransfer efficiency. That is, the amount of waste toner for the fog toner may be estimated by setting the primary transfer efficiency and the primary retransfer efficiency of (Equation 3) and (Equation 4) to 0% (the waste toner amount of the non-image portion is the fog toner). Match the quantity). When all the fog toner is collected by the self-color cleaning device 5, the predicted amount (K) of waste toner in the non-image portion is calculated from the following Equation 5 for each color.

(Formula 5)
Expected amount of waste toner (K) = white pixel count × (fogging correction rate (%) / 100) × (fogging environmental coefficient (%) / 100)
Therefore, Equation 5 = Equation 2 is satisfied, and also in the equation, all the fog toner is collected as waste toner by the cleaning device 5. Conventionally, in order to calculate the fog toner to be integrated with the amount of waste toner, it has been necessary to perform calculations using Equations 3 and 4 using the primary transfer efficiency and the primary retransfer efficiency. However, with the configuration of the present embodiment in which the fog toner is hardly primarily transferred, the complicated calculation as described above is not necessary, and the waste toner full detection accuracy is further increased.

  Note that, in the conventional example on the assumption that the fog toner is transferred to obtain the estimated amount of waste toner, if the polarity of the fog toner with respect to the potential is different each time, the error becomes large even if the correction is made by the transfer efficiency. On the other hand, in the method of the present embodiment, since the transfer of fog toner is not premised for obtaining the estimated amount of waste toner, such an error can be reduced.

(Operation of this embodiment)
As described above, according to the present embodiment, the fog toner can be controlled by the electric potential (retained on the photosensitive drum 1), so that it is not necessary to consider the transfer efficiency of the fog toner. For this reason, the accuracy of waste toner amount integration is improved. As a result, the waste toner full state can be accurately detected.

<< Second Embodiment >>
In the first embodiment, Vback is made constant in order to control the collection of fog toner. When all the voltages applied to each station are the same, there is a problem that Vback varies from station to station. In the present embodiment, assuming that the charging high voltage 53 is shared by each station, Vback is made constant using background exposure described later.

(Charging high voltage power supply)
The charging high-voltage power supply 53 will be described with reference to FIG. In FIG. 13, only the main part is shown with respect to the configuration shown in FIG. 1, and members such as the transfer cleaning device 16 are not shown. In FIG. 13, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

  The charging high-voltage power supply 53 includes a transformer and a transformer driving / control system. In the example of FIG. 13, the charging rollers 2a to 2d corresponding to each of a plurality of colors are connected to a charging high-voltage power supply 53, and the charging high-voltage power supply 53 receives a charging voltage Vcdc (power supply voltage) output from a negative transformer. The charging rollers 2a to 2d are supplied. That is, as a power source for supplying voltage to the charging rollers 2a to 2d, one common high-voltage power source 53 is applied.

  Therefore, in the power supply circuit of FIG. 13, the voltage applied to each roller from the charging high-voltage power supply 53 can be collectively adjusted while maintaining a predetermined relationship. However, independent individual adjustment between colors cannot be performed.

  In order to control the charging voltage Vcdc to be substantially constant, a negative voltage obtained by stepping down the charging voltage Vcdc by R2 / (R1 + R2) is offset to a positive voltage by the reference voltage Vrgv to obtain a monitor voltage Vref, which becomes a constant value. Feedback control is performed. Specifically, the control voltage Vc preset by the CPU is input to the positive terminal of the operational amplifier 55, and the monitor voltage Vref is input to the negative terminal. The engine control unit appropriately changes the control voltage Vc depending on the situation.

  The output value of the operational amplifier 55 feedback-controls the control / drive system of the transformer so that the monitor voltage Vref becomes equal to the control voltage Vc. As a result, the charging voltage Vcdc output from the transformer is controlled to be the target value.

  Here, the resistance elements R1 and R2 may be configured by any of a fixed resistance, a semi-fixed resistance, and a variable resistance. In the drawing, the power supply voltage itself from the transformer is directly input to the charging rollers 2a to 2d as the charging high-voltage power supply 53, but this is merely an example, and the present invention is not limited to this voltage input form. Various voltage input forms to individual rollers of the charging unit and the developing unit are assumed. For example, instead of the output from the transformer itself, a voltage obtained by DC-DC conversion using a converter, or a voltage obtained by dividing or stepping down a power supply voltage or a converted voltage by an electronic element having a fixed voltage drop characteristic is used as a charging roller. You may input into 2a-2d.

  As an electronic element having a fixed voltage drop characteristic, for example, a resistance element, a Zener diode, etc. can be cited as examples. The converter also includes a variable regulator and the like. In addition, voltage division or step-down by an electronic element includes further lowering the divided voltage or vice versa. Further, regarding the output control of the transformer, the output of the operational amplifier 55 may be input to the CPU, and the calculation result by the CPU may be reflected in the control / drive system of the transformer.

(Background exposure)
In this embodiment, in order to make Vback of each station constant from beginning to end, weak exposure (background exposure) is performed after applying a charging bias (after voltage application) from a common supply source, and the surface potential Vd of the photosensitive drum is kept constant. To. With this control, Vback can be controlled to be constant regardless of the usage status. This will be specifically described below.

  Before performing the background exposure, the surface potential (= Vd1) of the photosensitive drum 1 is uniquely determined according to the voltage applied to the charging roller 2. In the present embodiment, the surface of the photosensitive drum 1 charged to Vd1 is subjected to background exposure so that the charge is discharged to a desired Vd. This control is always performed regardless of the environment and usage conditions.

  The potential to be neutralized by background exposure was constant, and Vd1−Vd = 50V. By performing background exposure after charging, variation in potential after primary transfer on the surface of the photosensitive drum 1 can be suppressed, and Vd is stabilized. Therefore, the accuracy of Vback also increases.

  The charging bias is changed according to the environment, and is constant according to the usage state of the photosensitive drum 1. Then, since the surface potential Vd of the photosensitive drum 1 changes from a desired value depending on the use situation, the background exposure amount is appropriately adjusted. Since the potential to be neutralized by the background exposure is constant, the background exposure amount increases as the user is more used (the usage period is longer).

  Accordingly, the developing bias is also increased. The background exposure value is stored for each environment (temperature / humidity) and stored in the CPU 22. Values of L / L (15 ° C./10%), N / N (23 ° C./50%), and H / H (30 ° C./80%) are set, and linear interpolation is performed between the environments by the amount of moisture. The environmental information and usage status are read from the non-contact nonvolatile memory 23 and changed.

  An example of the potential relationship of the present embodiment is shown in FIG. As shown in the figure, the actually used potentials were Vd1 = −560V, Vd = −510V, Vdc = −380V, and Vback = 130V in the initial stage of use.

  As the user uses it, the sensitivity changes as the film thickness of the photosensitive drum 1 is reduced and thinned, and Vd1 increases in absolute value. Therefore, the developing bias is increased accordingly, and Vback is kept constant at the above value. It is said. FIG. 14B shows the potential relationship when the film thickness of the photosensitive drum 1 is changed by using the process cartridge. From the comparison between FIGS. 14A and 14B, it can be seen that Vback is always constant. Therefore, Vd1-Vd is made constant and Vdc is made to follow.

  With the above control, it is possible to change the background exposure amount according to the environment / process cartridge usage status, and to control the Vback to be constant at any usage.

<< Third Embodiment >>
In the second embodiment, the control in the case where the charging high voltage 53 is shared is described, but in the present embodiment, the control in the case where the development high voltage 30 is also shared is described. As in the second embodiment, after applying a charging bias to the charging roller 2, background exposure is performed to remove the charge to a desired Vd.

  In this embodiment, Vback is kept constant by making Vd constant without making the potential to be neutralized by background exposure constant. Therefore, unlike the second embodiment, Vd1−Vd is not constant in this embodiment. In this embodiment, in order to make Vd constant, the more frequently used the user, the greater the background exposure amount compared to the second embodiment.

  An example of the potential relationship of this embodiment is shown in FIG. As shown in FIG. 15A, the potential actually used was Vd1 = −600V, Vd = −480V, Vdc = −350V, and Vback = 130V in the initial use. FIG. 15B shows the potential relationship when the film thickness of the photosensitive drum changes due to use. From the comparison between FIGS. 15A and 15B, it can be seen that Vd and Vback are always constant. In the present embodiment, Vd1−Vd is changed for that purpose.

  By the above control, even when charging high voltage and development high voltage are shared, the background exposure amount is changed according to the environment and cartridge usage status, and Vback is controlled to be constant at any usage. It is possible to do.

<< Fourth Embodiment >>
As shown in the first to third embodiments, in order to control the fog toner in the non-image portion, it is only necessary to make Vback constant. Therefore, the charging high voltage 53 and the development high pressure 30 may be shared. In the present embodiment, a case where the charging high voltage 53 and the development high pressure 30 are shared will be described.

  As shown in FIG. 16, a voltage stabilizing element 18 is connected to the developing roller 6 in order to apply a high voltage from the charging high voltage 53 to the developing device 4. Since the voltage required for the developing voltage is smaller than the voltage required for the charging high voltage 53, the voltage stabilizing element 18 can sufficiently cover the voltage. In the present embodiment, the voltage stabilizing element 18 uses a Zener diode, but may be another voltage stabilizing element 18 as long as the same effect can be obtained, for example, an element such as a varistor.

(Modification)
As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary. The dimensions, materials, shapes, relative arrangements, and the like of the components described in the embodiments described above are not intended to limit the scope of the present invention only to those unless otherwise specified.

(Modification 1)
In the above-described embodiment, Vback = 130V is set so that the waste toner full tank detection accuracy is improved, the toner consumption is reduced, and the image is not adversely affected. However, Vback should be larger than 100V, and is not limited to 130V. .

(Modification 2)
In the above-described embodiment, the pixel count is described as the counting means for counting the image signal, but the present invention is not limited to this.

(Modification 3)
In the embodiment described above, the toner image is transferred onto the intermediate transfer member 10 by primary transfer, but a configuration in which the toner image is directly transferred onto the recording medium P may be used. However, since the surface property, resistance, and the like differ depending on the recording medium P, the transferability to the fog toner is not stable. On the other hand, when the intermediate transfer member 10 is used, the transfer state to the fog toner is always stable, so It has been confirmed that the tongue detection accuracy is higher.

1 .... photosensitive drum, 2 .... charging roller, 3 .... exposure device, 5 .... cleaning device, 6 .... developing roller, 22 .... CPU

Claims (19)

An image carrier;
Charging means for charging the surface of the image carrier;
Exposure means for forming an electrostatic latent image on the surface of the charged image carrier;
A developer carrying member for developing the electrostatic latent image with toner;
Transfer means for transferring the toner image formed on the image carrier to a transfer target;
A collecting means for collecting waste toner generated during image formation;
An acquisition unit for acquiring the amount of the waste toner;
Have
The potential difference between the charging potential of the image carrier and the development potential of the developer carrier is a potential difference that suppresses transfer of fog toner that adheres to a non-image portion of the image carrier to the transfer unit,
The acquisition unit
For the image portion of the image carrier, the amount of toner developed on the image carrier that is not transferred by the transfer means, and for the non-image portion, the toner amount of the fog toner, the amount of waste toner An image forming apparatus characterized by being acquired as follows.   The image forming apparatus according to claim 1, wherein the potential difference is a potential difference that makes the fog toner have the same polarity as a transfer bias of the transfer unit.   3. The image forming apparatus according to claim 1, wherein a potential difference between a charging potential of the image carrier and a developing potential of the developer carrier is made constant.   4. The image forming apparatus according to claim 1, wherein the transfer efficiency of the fog toner by the transfer unit is 5% or less.   The image forming apparatus according to claim 1, wherein a potential difference at which transfer by the transfer unit is suppressed is 120 V or more and 250 V or less.   The image forming apparatus according to claim 5, wherein a potential difference at which transfer by the transfer unit is suppressed is 130 V or more and 200 V or less. Having a counting means for counting image signals;
The image forming apparatus according to claim 1, wherein the developed amount of the toner is obtained as a predicted value by using the output of the counting unit.   The image forming apparatus according to claim 7, wherein the counting unit counts a signal for controlling light emission of a light emitting element in the exposure unit. The amount of the waste toner acquired by the acquisition unit is
The image portion of the image carrier is obtained using the output of the counting means and the transfer efficiency, and the non-image portion is obtained using the output of the counting means, a fog correction rate, and a fog environment coefficient. The image forming apparatus according to claim 7, wherein the image forming apparatus is an image forming apparatus.   The image carrier, the charging unit, the exposure unit, the developer carrier, the transfer unit, and the collecting unit are provided at different stations according to a plurality of colors. The image forming apparatus according to claim 1.   By applying a voltage from a common supply source to the charging unit and performing background exposure after applying the voltage, variation in the potential difference between the charging potential of the image carrier and the development potential of the developer carrier for each station The image forming apparatus according to claim 10, wherein the image forming apparatus is suppressed.   12. The image forming apparatus according to claim 11, wherein a voltage is applied from a common supply source to the developer carrying member, and the charging potential of the image carrying member by the background exposure is made constant.   The image forming apparatus according to claim 11, further comprising a voltage stabilizing element connected to the developer carrying member.   14. The image formation according to claim 11, wherein an exposure amount of the background exposure is changed so as to increase as a use period becomes longer in accordance with a use history of the image carrier. apparatus.   15. The voltage applied to the developer carrying member is changed according to the use history of the image carrying member so that the absolute value becomes larger as the use period is longer. The image forming apparatus described in the item.   16. The transfer efficiency for transferring a toner image formed on the image carrier to a transfer medium is defined according to the usage history of the image carrier. The image forming apparatus described.   17. The image forming apparatus according to claim 1, further comprising an intermediate transfer member, wherein the toner image on the image carrier is primarily transferred to the intermediate transfer member and secondarily transferred from the intermediate transfer member to a transfer material. The image forming apparatus according to claim 1. The acquisition unit
The amount of toner developed on the image carrier for the image portion that is not transferred by the transfer means and the amount of toner that is not transferred by the transfer means for the fog toner for the non-image portion are added. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. An image carrier;
Charging means for charging the surface of the image carrier;
A developer carrier that develops the electrostatic image of the image carrier with toner,
The potential difference between the charging potential of the image carrier and the development potential of the developer carrier is a potential difference that suppresses transfer of fog toner that adheres to the non-image portion of the image carrier,
For the image portion of the image carrier, the amount of toner that is not transferred among the toner developed on the image carrier is used, and for the non-image portion, the amount of fog toner is the amount of waste toner. Process cartridge.