Image forming apparatus that estimates deterioration status of cleaning blade according to current ratio

An image forming apparatus includes an image carrier, a developing device, a voltage applier, a current detector, a cleaning blade, and a control device. The control device acts as a measurer and an estimator. The measurer changes the DC bias to a first value and a second value, and acquires a first magnitude of the developing current corresponding to the first value, and a second magnitude of the developing current corresponding to the second value, from the current detector. The estimator calculates a current ratio between the first magnitude and the second magnitude, and estimates deterioration status of the cleaning blade, according to the value of the current ratio.

INCORPORATION BY REFERENCE

This application claims priority to Japanese Patent Application No. 2020-152060 filed on Sep. 10, 2020, the entire contents of which are incorporated by reference herein.

BACKGROUND

In general, existing image forming apparatuses include a photoconductor drum, a cleaning blade, and a control device. The control device estimates a distribution of slipperiness of the cleaning blade, with respect to the photoconductor drum in the axial direction thereof, on the basis of load variation during the rotation of the photoconductor drum, when a residual object on the surface of the photoconductor drum is being removed by the cleaning blade. According to the estimation result, a developing toner is supplied to a position where the slipperiness is low, so that the distribution of slipperiness is uniformized.

SUMMARY

The disclosure proposes further improvement of the foregoing techniques.

In an aspect, the disclosure provides an image forming apparatus including an image carrier, a developing device, a voltage applier, a current detector, a cleaning blade, and a control device. The image carrier carries an electrostatic latent image. The developing device includes a developing agent carrier that carries a developing agent at least containing toner. The voltage applier applies a bias voltage including a DC bias and an AC bias, to the developing agent carrier, to cause the toner to migrate from the developing agent carrier to the image carrier. The current detector measures developing current flowing between the developing agent carrier and the image carrier. The cleaning blade is located in contact with the image carrier, to remove residual toner on the image carrier after a toner image is transferred. The control device includes a processor, and acts as a measurer and an estimator. The measurer changes the DC bias to a first value and a second value, and acquires a first magnitude of the developing current corresponding to the first value, and a second magnitude of the developing current corresponding to the second value, from the current detector. The estimator calculates a current ratio between the first magnitude and the second magnitude, and estimates deterioration status of the cleaning blade, according to a value of the current ratio.

DETAILED DESCRIPTION

Hereafter, an embodiment of the disclosure will be described, with reference to the drawings. In the drawings, the same or corresponding elements are given the same numeral, and the description of such elements will not be repeated.

Referring toFIG.1, an image forming apparatus100according to the embodiment of the disclosure will be described.FIG.1is a schematic cross-sectional view showing an example of the image forming apparatus. The image forming apparatus100is, for example, a color printer. For the sake of convenience in description, a left-right direction inFIG.1will be defined as X-direction, a depth direction will be defined as Y-direction, and an up-down direction will be defined as Z-direction.

As shown inFIG.1, the image forming apparatus100includes an operation device2, a paper feeding device3, a transport device4, a toner supply device5, an image forming device6, a transfer device7, a fixing device8, and a delivery area9.

The operation device2receives instructions from a user. The operation device2includes an LCD21and a plurality of operation keys22. The LCD21displays, for example, various processing results. The operation keys22include a tenkey, a start key, and so forth.

The paper feeding device3includes a paper cassette31, and a feed roller group32. The paper cassette31can accommodate therein a plurality of sheets P. The feed roller group32delivers the sheets P one by one from the paper cassette31, to the transport device4.

The transport device4includes rollers and guide members. The transport device4extends from the paper feeding device3to the delivery area9. The transport device4transports the sheet P from the paper feeding device3to the delivery area9, by way of the image forming device6and the fixing device8.

The toner supply device5supplies the toner to the image forming device6. The toner supply device5includes a first mounting base51Y, a second mounting base51C, a third mounting base51M, and a fourth mounting base51K.

On the first mounting base51Y, a first toner container52Y is mounted. Likewise, a second toner container52C is mounted on the second mounting base51C, a third toner container52M is mounted on the third mounting base51M, and a fourth toner container52K is mounted on the fourth mounting base51K. The first mounting base51Y to the fourth mounting base51K have the same configuration, except that different toner containers are mounted thereon.

The first toner container52Y, the second toner container52C, the third toner container52M, and the fourth toner container52K are each configured to accommodate the toner therein. In this embodiment, the first toner container52Y accommodates yellow toner. The second toner container52C accommodates cyan toner. The third toner container52M accommodates magenta toner. The fourth toner container52K accommodates black toner.

The image forming device6includes an exposure device61, a first image forming unit62Y, a second image forming unit62C, a third image forming unit62M, and a fourth image forming unit62K.

The first image forming unit62Y to the fourth image forming unit62K each include a charging device63, a developing device64, a photoconductor drum65, and a cleaning device66. The photoconductor drum65exemplifies the “image carrier” in the disclosure.

The charging device63, the developing device64, and the cleaning device66are located along the circumferential surface of the photoconductor drum65. In this embodiment, the photoconductor drum65rotates in the direction indicated by an arrow R1 inFIG.1(clockwise).

The charging device63uniformly charges, by electric discharge, the photoconductor drum65to a predetermined polarity. In this embodiment, the charging device63charges the photoconductor drum65to the positive polarity. The exposure device61emits a laser beam to the photoconductor drum65charged as above. As result, an electrostatic latent image is formed on the surface of the photoconductor drum65.

The developing device64develops the electrostatic latent image formed on the surface of the photoconductor drum65, thereby forming a toner image. The toner is supplied from the toner supply device5, to the developing device64. The developing device64applies the toner supplied from the toner supply device5, to the surface of the photoconductor drum65. As result, the toner image is formed on the surface of the photoconductor drum65.

In this embodiment, the developing device64in the first image forming unit62Y is connected to the first mounting base51Y. Accordingly, the yellow toner is supplied to the developing device64in the first image forming unit62Y. On the surface of the photoconductor drum65of the first image forming unit62Y, a yellow toner image is formed.

The developing device64in the second image forming unit62C is connected to the second mounting base51C. Accordingly, the cyan toner is supplied to the developing device64in the second image forming unit62C. On the surface of the photoconductor drum65of the second image forming unit62C, a cyan toner image is formed.

The developing device64in the third image forming unit62M is connected to the third mounting base51M. Accordingly, the magenta toner is supplied to the developing device64in the third image forming unit62M. On the surface of the photoconductor drum65of the third image forming unit62M, a magenta toner image is formed.

The developing device64in the fourth image forming unit62K is connected to the fourth mounting base51K. Accordingly, the black toner is supplied to the developing device64in the fourth image forming unit62K. On the surface of the photoconductor drum65of the fourth image forming unit62K, a black toner image is formed.

The transfer device7superposes the respective toner images formed on the surface of the photoconductor drum65of the first image forming unit62Y to the fourth image forming unit62K, and transfers the superposed the toner images to the sheet P In this embodiment, the transfer device7transfers the superposed toner images to the sheet P, through a secondary transfer process. To be more detailed, the transfer device7includes four primary transfer rollers71, an intermediate transfer belt72, a drive roller73, a follower roller74, and a secondary transfer roller75.

The intermediate transfer belt72is an endless belt stretched around the four primary transfer rollers71, the drive roller73, and the follower roller74. The intermediate transfer belt72is driven by the rotation of the drive roller73. InFIG.1, the intermediate transfer belt72rotates counterclockwise. The follower roller74is made to rotate by the movement of the intermediate transfer belt72.

The first image forming unit62Y to the fourth image forming unit62K are opposed to the lower surface of the intermediate transfer belt72, and aligned along the moving direction D thereof. In this embodiment, the first image forming unit62Y to the fourth image forming unit62K are aligned in this order, from the upstream side toward the downstream side in the moving direction D of the lower surface of the intermediate transfer belt72.

The primary transfer rollers71are each opposed to the photoconductor drum65via the intermediate transfer belt72, and pressed against the photoconductor drum65. Therefore, the toner image formed on the surface of each of the photoconductor drums65is sequentially transferred to the intermediate transfer belt72. In this embodiment, the yellow toner image, the cyan toner image, the magenta toner image, and the black toner image are superposed and transferred in this order, onto the intermediate transfer belt72.

The cleaning devices66respectively provided for the first image forming unit62Y to the fourth image forming unit62K serve to remove the residual toner on the photoconductor drum65, remaining after the toner image is transferred to the intermediate transfer belt72.

The secondary transfer roller75is opposed to the drive roller73, via the intermediate transfer belt72. The secondary transfer roller75is pressed against the drive roller73. Accordingly, a transfer nip is defined between the secondary transfer roller75and the drive roller73. When the sheet P passes the transfer nip, the toner images superposed on the intermediate transfer belt72are transferred to the sheet P The sheet P having the toner images transferred thereto is transported by the transport device4, toward the fixing device8.

The fixing device8includes a heating member81and a pressing member82. The heating member81and the pressing member82are opposed to each other, so as to define a fixing nip. The sheet P transported from the image forming device6is heated at a predetermined fixing temperature under a pressure, while passing the fixing nip. As result, the toner image is fixed to the sheet P The sheet P is transported by the transport device4, from the fixing device8to the delivery area9.

The delivery area9includes a delivery roller pair91and an output tray93. The delivery roller pair91delivers the sheet P to the output tray93, through a delivery port92. The delivery port92is located on the upper side of the image forming apparatus100.

Referring toFIG.1andFIG.2, the configuration of the developing device64will be described, in further detail.FIG.2is an enlarged cross-sectional view showing the detailed configuration of the developing device64. InFIG.2, the charging device63is not shown.

In this embodiment, as shown inFIG.2, the developing device64includes a developing container640in which a two-component developing agent is stored. The developing device64includes, inside the developing container640, a developing roller641, a first mixing screw643, a second mixing screw644, and a blade645. To be more detailed, the developing roller641is opposed to the second mixing screw644. The blade645is opposed to the developing roller641. The developing roller641exemplifies the “developing agent carrier” in the disclosure.

The developing container640is divided into a first mixing chamber640A and a second mixing chamber640B, by a partition wall640C. The partition wall640C extends in the axial direction of the developing roller641(Y-direction inFIG.2). The first mixing chamber640A and the second mixing chamber640B communicate with each other, through an outer region of the end portions of the partition wall640C in the longitudinal direction.

In the first mixing chamber640A, the first mixing screw643is provided. In the first mixing chamber640A, a magnetic carrier is stored. To the first mixing chamber640A, a non-magnetic toner is supplied through a toner inlet640H.

In the second mixing chamber640B, the second mixing screw644is provided. In the second mixing chamber640B, the magnetic carrier is stored.

The toner is stirred by the first mixing screw643and the second mixing screw644, thus to be mixed with the carrier. As result, the two-component developing agent composed of the carrier and the toner is formed. The two-component developing agent exemplifies the “developing agent” in the disclosure.

The first mixing screw643and the second mixing screw644circulate and stir the developing agent, between the first mixing chamber640A and the second mixing chamber640B. As result, the toner is charged to a predetermined polarity. In this embodiment, the toner is positively charged.

The developing roller641includes a non-magnetic rotary sleeve641A and a magnetic body641B. The magnetic body641B is fixed inside the rotary sleeve641A. The magnetic body641B includes a plurality of magnetic poles. The developing agent is adsorbed to the developing roller641, by the magnetic force of the magnetic body641B. As result, a magnetic brush is formed on the surface of the developing roller641.

In this embodiment, the developing roller641rotates in the direction indicated by an arrow R2 inFIG.2(counterclockwise). The developing roller641transports, by rotating, the magnetic brush to the position opposite the blade645. The blade645is located so as to define a gap between the blade645and the developing roller641. Accordingly, the thickness of the magnetic brush is defined by the b blade645. The blade645is located on the upstream side in the rotating direction of the developing roller641, with respect to the position where the developing roller641and the photoconductor drum65are opposed to each other.

A predetermined voltage is applied to the developing roller641. Accordingly, the developing agent layer formed on the surface of the developing roller641is transported to the position opposite the photoconductor drum65, and the toner in the developing agent adheres to the photoconductor drum65.

The cleaning device66includes a cleaning blade661located in contact with the photoconductor drum65. The cleaning blade661is, for example, made of rubber. The cleaning blade661is located downstream of the position where the primary transfer roller71and the photoconductor drum65are opposed to each other, in the rotating direction of the photoconductor drum65.

Referring now toFIG.1toFIG.3, a circuit configuration of the image forming apparatus100will be described hereunder.FIG.3is a block diagram showing an example of the circuit configuration of the image forming apparatus100.

As shown inFIG.3, the image forming apparatus100includes a control device10, a storage device11, and a high-voltage applying substrate12, in addition to the photoconductor drum65and the developing roller641.

The storage device11includes memory units. In the storage device11, various types of data and computer programs are stored. The storage device11includes a main memory unit such as a semiconductor memory, and an auxiliary memory unit such as a hard disk drive.

The control device10includes a processor, for example a central processing unit (CPU). The control device10controls the components of the image forming apparatus100, by executing the computer program stored in the storage device11. More specifically, the control device10acts as a first measurer101, a second measurer102, and an estimator103, by executing the computer program stored in the storage device11.

The high-voltage applying substrate12includes a voltage applier121and a current detector122. The voltage applier121applies a bias voltage to the developing roller641, to cause the toner to migrate from the developing roller641to the photoconductor drum65. The bias voltage refers to a voltage in which an AC bias is superposed on a DC bias. The current detector122is an ammeter for measuring a developing current Id, flowing between the developing roller641and the photoconductor drum65.

The measurer101controls the operation of the voltage applier121and the current detector122, and measures the developing current Id. The control device10controls the exposure device61, in the measurement mode of the developing current Id, so as to form an electrostatic latent image representing a rectangular patch pattern having a predetermined area, on the photoconductor drum65.

The estimator102changes the DC bias Vdc to a first value Vdc1 and a second value Vdc2. The estimator102calculates a current ratio R, indicating a ratio between a first magnitude Id1 of the developing current Id corresponding to the first value Vdc1, and a second magnitude Id2 of the developing current Id corresponding to the second value Vdc2. Further, the estimator102estimates the deterioration status of the cleaning blade661, according to the value of the current ratio R calculated as above.

The estimator102changes the value of the AC bias Vac, while maintaining the first value Vdc1 and the second value Vdc2, and acquires a specific value Vx of the AC bias Vac that makes the current ratio R maximum. The estimator102sets the AC bias Vac, to be used for the estimation of the deterioration status of the cleaning blade661, to the specific value Vx.

The estimator102generates a prediction curve C indicating a predicted change with time, of the value of the current ratio R, and determines a next status estimation timing of the cleaning blade661, on the basis of the prediction curve C.

The estimator102updates the prediction curve C, when the value of the current ratio R acquired after generating the prediction curve C is deviated from the prediction curve C.

The estimator102compares between the value of the current ratio R and a first threshold X1, and calculates, when the value of the current ratio R is equal to or smaller than the first threshold X1, the current ratio R with respect to each of a plurality of sections defined by dividing the photoconductor drum65. The estimator102compares between the value of the current ratio R of each of the plurality of sections and a second threshold X2 smaller than the first threshold X1, and outputs a warning about the service life of the cleaning blade661, when the value of the current ratio R is larger than the second threshold X2, with respect to all of the plurality of sections.

The estimator102compares between the value of the current ratio R and the first threshold X1, and calculates, when the value of the current ratio R is equal to or smaller than the first threshold X1, the current ratio R with respect to each of the plurality of sections defined by dividing the photoconductor drum65. The estimator102compares between the value of the current ratio R of each of the plurality of sections and the second threshold X2 smaller than the first threshold X1, and outputs a recommendation to replace the cleaning blade661, when the value of the current ratio R of any of the plurality of sections is equal to or smaller than the second threshold X2.

For example, the direction of the developing current Id flowing from the developing roller641to the photoconductor drum65will be defined as positive direction of the developing current Id. When a potential difference between the DC bias Vdc of the developing roller641and a surface potential V0 of the photoconductor drum65after the exposure (Vdc−V0) is positive, a forward bias is given between the developing roller641and the photoconductor drum65. When the potential difference (Vdc−V0) is negative, a reverse bias is given between the developing roller641and the photoconductor drum65.

The first value Vdc1 of the DC bias Vdc is, for example, determined so as to make the potential difference (Vdc−V0) positive. Accordingly, the first magnitude Id1 of the developing current Id is positive. The second value Vdc2 of the DC bias Vdc is, for example, determined so as to make the potential difference (Vdc−V0) negative. Accordingly, the second magnitude Id2 of the developing current Id is negative. The current ratio R is, for example, the absolute value of Id1/Id2.

When the cleaning blade661is deteriorated, to such an extent that the removal performance of the residual toner on the surface of the photoconductor drum65declines, the first magnitude Id1 of the developing current Id is reduced, though the first value Vdc1 of the DC bias Vdc remains unchanged. This is because the flight of the toner of the positive polarity from the developing roller641is disturbed by the residual toner of the positive polarity, on the photoconductor drum65. Further, when the removal performance of the residual toner on the surface of the photoconductor drum65declines, owing to the deterioration of the cleaning blade661, the absolute value of the second magnitude Id2 of the developing current Id is increased, though the second value Vdc2 of the DC bias Vdc remains unchanged. This is because the residual toner of the positive polarity, on the surface of the photoconductor drum65, is returned to the developing roller641, by the reverse bias. Therefore, it can be predicted that the current ratio R is reduced, when the cleaning blade661is deteriorated.

Referring toFIG.1toFIG.5, an operation performed by the control device10will be described.FIG.4andFIG.5are flowcharts each showing an initialization process, which is an example of the operation performed by the control device10. The initialization process is performed only once, for example when the image forming apparatus100is shipped from the manufacturing plant.

Step S101: As shown inFIG.4, the control device10sets the DC bias Vdc to a first value Vdc1 and a second value Vdc2. Upon completing the operation of step S101, the control device10proceeds to step S103.

Step S103: The control device10initializes a variable n for controlling an iterative process, to 1. Upon completing the operation of step S103, the control device10proceeds to step S105.

Step S105: The control device10sets the AC bias to a specific value Vac_n. The specific value Vac_n varies depending on the value of the variable n. Upon completing the operation of step S105, the control device10proceeds to step S107.

Step S107: The control device10causes the voltage applier121to apply the bias to the developing roller641, and acquires a first magnitude Id1 of the developing current Id corresponding to the bias Vdc1+Vac_n, from the current detector122. Upon completing the operation of step S107, the control device10proceeds to step S109.

Step S109: The control device10causes the voltage applier121to apply the bias to the developing roller641, and acquires a second magnitude Id2 of the developing current Id corresponding to the bias Vdc2+Vac_n, from the current detector122. Upon completing the operation of step S109, the control device10proceeds to step S111.

Step S111: The control device10calculates the value of the current ratio R, on the basis of the first magnitude Id1 and the second magnitude Id2 of the developing current Id. Here, at step S107and step S109, the control device10controls the exposure device61, so as to form the electrostatic latent image, representing the rectangular patch pattern having the predetermined area, over the entirety of the photoconductor drum65in the axial direction. Upon completing the operation of step S111, the control device10proceeds to step S113.

Step S113: As shown inFIG.5, the control device10decides whether the variable n is equal to 1. Upon deciding that the variable n is equal to 1 (Yes at step S113), the control device10proceeds to step S115. When the control device10decides that the variable n is not equal to 1 (No at step S113), the control device10proceeds to step S119.

Step S115: The control device10stores the value of the current ratio R calculated at step S111in the storage device11, as a maximum value Rx. In addition, the control device10stores the specific value Vac_n of the AC bias Vac, used at step S107and step S109, in the storage device11as an optimum value Vx. Upon completing the operation of step S115, the control device10proceeds to step S117.

Step S117: The control device10updates the value of the variable n, by adding 1. Upon completing the operation of step S117, the control device10proceeds to step S121.

Step S119: The control device10decides whether the value of the current ratio R calculated at step S111is larger than the maximum value Rx. Upon deciding that the value of the current ratio R is larger than the maximum value Rx (Yes at step S119), the control device10proceeds to step S115, so that the maximum value Rx is updated. When the control device10decides that the value of the current ratio R is equal to or smaller than the maximum value Rx (No at step S119), the control device10proceeds to step S117.

Step S121: The control device10decides whether the value of the variable n is equal to or larger than a threshold nx. Upon deciding that the value of the variable n is equal to or larger than the threshold nx (Yes at step S121), the control device10proceeds to step S123. When the control device10decides that the value of the variable n is smaller than the threshold nx (No at step S121), the control device10returns to step S105.

Step S123: The control device10sets the value of the AC bias Vac, to be used for estimating the deterioration status of the cleaning blade661, to the optimum value Vx. The optimum value Vx corresponds to the specific value Vac_n of the AC bias Vac that maximizes the value of the current ratio R, as described with reference to the operation from step S103to step S121. While the optimum value Vx is being searched, the first value Vdc1 and the second value Vdc2 of the DC bias Vdc are maintained. Upon completing the operation of step S123, the control device10proceeds to step S125.

Step S125: The control device10stores the maximum value Rx of the current ratio R stored at step S115in the storage device11, as an initial value X0. Upon completing the operation of step S125, the control device10proceeds to step S127.

Step S127: The control device10generates the prediction curve C representing the predicted change with time, of the value of the current ratio R. Upon completing the operation of step S127, the control device10proceeds to step S129.

Step S129: The control device10sets the value of an execution interval Tp of the status estimation, to an initial value T0. Upon completing the operation of step S129, the control device10finishes the initialization process.

Referring toFIG.1toFIG.8, further description will be given regarding the operation performed by the control device10.FIG.6,FIG.7, andFIG.8are flowcharts each showing a status estimation process, which is another example of the operation performed by the control device10.

Step S201: As shown inFIG.6, the control device10decides whether the execution interval Tp of the status estimation has elapsed. Upon deciding that the execution interval Tp of the status estimation has elapsed (Yes at step S201), the control device10proceeds to step S203. In contrast, when the control device10decides that the execution interval Tp of the status estimation has not elapsed yet (No at step S201), the control device10finishes the status estimation process.

Step S203: The control device10causes the voltage applier121to apply the bias to the developing roller641, and acquires the first magnitude Id1 of the developing current Id corresponding to the bias Vdc1+Vx, from the current detector122. Upon completing the operation of step S203, the control device10proceeds to step S205.

Step S205: The control device10causes the voltage applier121to apply the bias to the developing roller641, and acquires the second magnitude Id2 of the developing current Id in the bias Vdc2+Vx, from the current detector122. Upon completing the operation of step S205, the control device10proceeds to step S207.

Step S207: The control device10calculates the value of the current ratio R, on the basis of the first magnitude Id1 and the second magnitude Id2 of the developing current Id. Here, at step S203and step S205, the control device10controls the exposure device61, so as to form the electrostatic latent image, representing the rectangular patch pattern having the predetermined area, over the entirety of the photoconductor drum65in the axial direction. Upon completing the operation of step S207, the control device10proceeds to step S209.

Step S209: The control device10decides whether the value of the current ratio R calculated at step S207is larger than the first threshold X1. Upon deciding that the value of the current ratio R is larger than the first threshold X1 (Yes at step S209), the control device10proceeds to step S211. When the control device10decides that the value of the current ratio R is equal to or smaller than the first threshold X1 (No at step S209), the control device10proceeds to step S215.

Step S211: The control device10decides whether the value of the current ratio R calculated at step S207is deviated from the prediction curve C. Upon deciding that the value of the current ratio R is deviated from the prediction curve C (Yes at step S211), the control device10proceeds to step S213. In contrast, when the control device10decides that the value of the current ratio R is not deviated from the prediction curve C (No at step S211), the control device10finishes the status estimation process.

Step S213: The control device10updates the prediction curve C, so as to accord with the value of the current ratio R calculated at step S207. Upon completing the operation of step S213, the control device10finishes the status estimation process.

Step S215: The control device10decides whether the value of the current ratio R calculated at step S207is larger than the second threshold X2 (<X1). Upon deciding that the value of the current ratio R is larger than the second threshold X2 (Yes at step S215), the control device10proceeds to step S219shown inFIG.7. It is when the value of the current ratio R satisfies an inequality X2<R≤X1, that the control device10proceeds to step S219. When the control device10decides that the value of the current ratio R is equal to or smaller than the second threshold X2 (No at step S215), the control device10proceeds to step S217.

Step S217: The control device10outputs an alert recommending replacement of the unit including the cleaning blade661, to the user through the LCD21. Upon completing the operation of step S217, the control device10finishes the status estimation process.

Step S219: As shown inFIG.7, the control device10initializes a variable m for controlling an iterative process, to 1. Upon completing the operation of step S219, the control device10proceeds to step S221.

Step S221: The control device10controls the exposure device61, so as to form the electrostatic latent image, representing the rectangular patch pattern having the predetermined area, only on a section m of the photoconductor drum65in the axial direction. To check whether the cleaning blade661is partially damaged, the control device10virtually divides the photoconductor drum65, for example into eight sections, in the Y-direction. Upon completing the operation of step S221, the control device10proceeds to step S223.

Step S223: The control device10causes the voltage applier121to apply the bias to the developing roller641, and acquires the first magnitude Id1 of the developing current Id corresponding to the bias Vdc1+Vx, from the current detector122. Upon completing the operation of step S223, the control device10proceeds to step S225.

Step S225: The control device10causes the voltage applier121to apply the bias to the developing roller641, and acquires the second magnitude Id2 of the developing current Id corresponding to the bias Vdc2+Vx, from the current detector122. Upon completing the operation of step S225, the control device10proceeds to step S227.

Step S227: The control device10calculates the value of the current ratio R, on the basis of the first magnitude Id1 and the second magnitude Id2 of the developing current Id. Upon completing the operation of step S227, the control device10proceeds to step S229.

Step S229: The control device10updates the value of the variable m, by adding 1. Upon completing the operation of step S229, the control device10proceeds to step S231.

Step S231: The control device10decides whether the value of the variable m is equal to or larger than a threshold mx. Upon deciding that the value of the variable m is equal to or larger than the threshold mx (Yes at step S231), the control device10proceeds to step S233shown inFIG.8. When the control device10decides that the value of the variable m is smaller than the threshold mx (No at step S231), the control device10returns to step S221. For example, when the photoconductor drum65is divided into eight sections in the Y-direction, the control device10sets the threshold mx to 9.

Step S233: As shown inFIG.8, the control device10decides whether the value of the current ratio R repeatedly calculated at step S227is larger than the second threshold X2, in all the sections of the photoconductor drum65. Upon deciding that value of the current ratio R is larger than the second threshold X2 in all the sections (Yes at step S233), the control device10proceeds to step S235. When the control device10decides that the value of the current ratio R is equal to or smaller than the second threshold X2 in any of the sections (No at step S233), the control device10proceeds to step S243. Here, the second threshold X2 related to step S215, and the second threshold X2 related to step S233may be different from each other.

Step S235: The control device10decides whether it is possible to change a transfer condition of the transfer device7, so as to compensate the decline in performance of the cleaning blade661. Upon deciding that it is possible to change the transfer condition (Yes at step S235), the control device10proceeds to step S237. When the control device10decides that the transfer condition is unable to be changed (No at step S235), the control device10proceeds to step S239.

Step S237: The control device10changes the transfer condition of the transfer device7. Upon completing the operation of step S237, the control device10finishes the status estimation process.

Step S239: The control device10outputs a warning about the service life of the cleaning blade661, to the user through the LCD21. Upon completing the operation of step S239, the control device10proceeds to step S241.

Step S241: The control device10changes the value of the execution interval Tp of the status estimation, to a predetermined value T1 (T1<T0). In other words, the control device10determines the next status estimation timing of the cleaning blade661, on the basis of the prediction curve C. Upon completing the operation of step S241, the control device10finishes the status estimation process.

Step S243: The control device10outputs the alert recommending replacement of the unit including the cleaning blade661, to the user through the LCD21. Upon completing the operation of step S243, the control device10finishes the status estimation process.

Through the status estimation process shown inFIG.6toFIG.8, the control device10calculates the current ratio R with respect to each of the plurality of sections of the photoconductor drum65, when the value of the current ratio R, calculated with respect to the entirety of the photoconductor drum65, is equal to or smaller than the first threshold X1. The control device10compares between the value of the current ratio R of each of the plurality of sections, and the second threshold X2 smaller than the first threshold X1. When the value of the current ratio R is larger than the second threshold X2 in all of the plurality of sections, the control device10outputs the warning about the service life of the cleaning blade661. In contrast, when the value of the current ratio R is equal to or smaller than the second threshold X2 in any of the plurality of sections, the control device10recommends the replacement of the cleaning blade661. Thus, either the service life warning of the cleaning blade661, or the alert recommending the unit replacement is provided to the user, depending on the value of the current ratio R.

Working Example 1

Hereunder, a working example of the disclosure will be described. The driving condition, the bias condition, and the toner condition for the working example are specified below. However, the disclosure is not limited to the following working example.

Developing DC bias: −110 V to 130 V

Potential difference between drum and developing agent carrier (Vdc−V0): −130V to 110V

Toner polarity: Positive

Referring toFIG.9, a correlation between the DC bias Vdc and the developing current Id in this working example will be described.FIG.9is a graph showing an example of the correlation between the DC bias Vdc and the developing current Id. InFIG.9, the horizontal axis represents the potential difference (Vdc−V0) [V] between the developing roller641and the photoconductor drum65, and the vertical axis represents the developing current Id [μA].

FIG.9is a graph showing a measurement result obtained when the cleaning blade661is not deteriorated yet. In a range of the DC bias Vdc indicating a forward bias (Vdc−V0>0), the positively charged toner flying from the developing roller641to the photoconductor drum65increases, with the increase of the DC bias Vdc, and therefore the positive developing current Id increases. On the other hand, in a range of the DC bias Vdc indicating the reverse bias (Vdc−V0<0), the negatively charged toner or carrier flies from the developing roller641to the photoconductor drum65, and therefore the negative developing current Id appears. However, the absolute value of the developing current Id corresponding to the reverse bias is smaller than that of the developing current Id corresponding to the forward bias.

According toFIG.9, the DC bias Vdc is set as Vdc1−V0=110V, and Vdc2−V0=−130V in the initialization process. When V0 is 20V Vdc1 is 130V and Vdc2 is −110V. When the value of the AC bias Vac is 1000 Vpp under such condition of the DC bias, the value of the current ratio R was 3.57. When the value of the AC bias Vac is 1200 Vpp under the same condition of the DC bias, the value of the current ratio R was 3.89. Therefore, the optimum value Vx of the AC bias Vac is set to 1200Vpp. The initial value X0 of the current ratio R is 3.89.

Referring toFIG.10, the prediction curve C will be described hereunder.FIG.10is a graph showing an example of the prediction curve C of the value of the current ratio R. InFIG.10, the horizontal axis represents the operation duration of the image forming apparatus100, and the vertical axis represents the value of the current ratio R.

As shown inFIG.10, the value of the current ratio R at the operation duration “0” is the initial value X0. As long as the value of the current ratio R is not deviated from the prediction curve C, the control device10executes the status estimation process shown inFIG.6toFIG.8, each time the initial value T0 of the execution interval Tp of the status estimation elapses. Thereafter, when the cleaning blade661is deteriorated to such an extent that the value of the current ratio R satisfies the inequality X2<R≤X1, the service life warning is provided to the user. When the cleaning blade661is further deteriorated to such an extent that the value of the current ratio R satisfies an inequality R≤X2, the alert recommending the unit replacement is provided to the user. The first threshold X1 and the second threshold X2 may be set, for example, so as to satisfy X1=0.5X0 and X2=0.3X0 respectively, on the basis of the initial value X0 of the current ratio R.

Now, the aforementioned existing image forming apparatus is unable to detect a decline in slipperiness of the cleaning blade as a whole. Besides, an increase in the number of positions where the slipperiness of the cleaning blade has declined leads to an increase in toner consumption.

With the configuration according to the foregoing embodiment, in contrast, the image forming apparatus100, capable of estimating the deterioration status of the cleaning blade661, can be obtained.

The embodiment of the disclosure has been described as above, with reference to the drawings. However, the disclosure is not limited to the foregoing embodiment, but may be implemented in various manners without departing from the scope of the disclosure. The plurality of constituent elements disclosed in the foregoing embodiment may be combined as desired, to achieve various inventions. For example, some constituent elements may be excluded, from those disclosed in the foregoing embodiment. The drawings each schematically illustrate the essential constituent elements for the sake of clarity, and the thickness, the length, and the number of pieces of each of the illustrated constituent elements may differ from the actual ones, depending on the convenience in making up the drawings. Further, the material, the shape, and the dimensions of the constituent elements described in the foregoing embodiment are merely exemplary, and may be modified in various manners without substantially departing from the effects expected from the present invention.

Although the image forming apparatus100is exemplified by the color printer in the foregoing embodiment, the disclosure is not limited thereto. The image forming apparatus100may be any apparatus that forms an image using the electrophotography technique.

Although the two-component developing agent is employed as the developing agent in the foregoing embodiment, the disclosure is not limited thereto. The developing agent may be a one-component developing agent.

INDUSTRIAL APPLICABILITY

The disclosure is applicable to the technical field of the image forming apparatus.