JP6676921B2 - Image forming device - Google Patents

Description

  The present invention relates to an image forming apparatus.

  Japanese Patent Application Laid-Open No. H11-163,897 discloses that the thickness of the photoreceptor is accurately and stably detected when it reaches a lower limit thickness as a service limit (lifetime). In Patent Document 1, an average thickness can be detected.

  Further, in Japanese Patent Application Laid-Open No. H11-163, the leak current after the charge amount is saturated is compared with a predetermined threshold value, and the thickness detection of the photoconductor is controlled according to the comparison result. It is described that when the threshold value is exceeded, data indicating the charging current is discarded.

JP 04-056914 A JP-A-2006-5548

  It is difficult to extract a current caused by the film thickness from the charging current, and uneven wear cannot be detected by monitoring the average thickness of the photoconductor.

  The present invention has been made in consideration of the above-described circumstances, and has as its object to obtain an image forming apparatus capable of accurately detecting uneven wear of a photoconductor compared with a case of detecting a degree of wear by monitoring only an average film thickness. is there.

An image forming mechanism unit comprising: a charging unit having a function of charging the surface of the photoconductor; and a charge elimination function group including a charge elimination function unit having a function of discharging the surface of the photoconductor. An interrupting means for interrupting the static elimination operation by the static elimination function group, interruption of the static elimination operation by the interruption means, and a condition that the charging section is charged in a saturated state, a current value flowing through the charging section, and a threshold value. using said determination means for determining occurrence of irregular wear of the surface of the photosensitive member, have a, in the case where the determination means determines that there is occurrence of uneven wear of the surface of the photosensitive member, the charging unit The surface potential of the photoreceptor due to the charging in step (b) is made lower than the potential during the steady image forming process, and the image forming process is continued while suppressing the leakage current of the photoreceptor .

  According to a second aspect of the present invention, in the first aspect of the present invention, when the determining means determines the occurrence of uneven wear, a current value flowing through the charging section is determined by a difference between the grounded base material and the photosensitive member. It is a leakage current value between the insulating layer on the body surface.

  According to a third aspect of the present invention, in the first or the second aspect of the present invention, the static elimination function group includes an exposure unit that forms an electrostatic latent image on the surface of the photoconductor, and an electrostatic latent image. The image forming apparatus includes at least one of a developing unit that develops with toner, a transfer unit that transfers a toner image developed by the developing unit to a transfer target body, and a charge removing unit that removes charges on the surface of the photoconductor.

  According to a fourth aspect of the present invention, in the first aspect of the present invention, when the occurrence of uneven wear is determined by the determination unit, the photosensitive member is charged by the charging unit. The surface potential of the body is made higher than the potential at the time of image forming processing.

  According to a fifth aspect of the present invention, in the first aspect of the present invention, the condition for the charging in the saturated state, in which the photosensitive member is rotated more than a predetermined number of times, is set. It is established.

  According to a sixth aspect of the present invention, in the invention according to any one of the first to fifth aspects, when the determination unit determines that uneven wear of the surface of the photoreceptor has occurred, the light-sensitive element is moved. There is further provided a notifying unit for notifying that the body is to be replaced.

According to the first aspect of the invention, uneven wear of the photoconductor can be detected with higher accuracy than when only the average film thickness is monitored and the degree of wear is detected.
Further, it is possible to prevent image quality deterioration due to uneven wear of the photoconductor.
Further, it is possible to suppress a difference in shading during image forming processing.

  According to the second aspect of the present invention, it is possible to detect the value of the current flowing through the charging unit as a leakage current.

  According to the third aspect of the present invention, it is possible to prevent the charge from leaking from the photoconductor.

  According to the fourth aspect of the present invention, the detection sensitivity can be higher than the detection sensitivity of the leakage current at the potential during the steady-state image forming process.

  According to the fifth aspect of the present invention, the charged state can be brought into a saturated state by the number of rotations of the photoconductor.

  According to the sixth aspect of the present invention, it is possible to prevent image quality deterioration caused by uneven wear of the photoconductor.

1 is a schematic configuration diagram of an image forming apparatus according to the present embodiment. FIG. 2 is an enlarged view of an image forming unit of the image forming apparatus according to the present embodiment and a sheet transport unit around the image forming unit. FIG. 2 is a block diagram illustrating a control system of the image forming apparatus according to the present embodiment. 4A is an enlarged view of the photosensitive drum and its periphery, and FIG. 4B is a sectional view taken along line IVB-IVB in FIG. FIG. 3 is an electric field-current characteristic diagram in a charge transport layer of a photoconductor drum. FIG. 4 is a characteristic diagram illustrating a surface potential and a DC current value of a charging unit with respect to the number of cycles of the photosensitive drum according to the exemplary embodiment. FIG. 4 is a block diagram in which the flow of uneven wear monitoring control executed by the image forming processing control unit according to the present embodiment is classified according to function. 5 is a flowchart for executing uneven wear monitoring control, which is executed by the image forming processing control unit according to the present embodiment.

  FIG. 1 schematically shows an image forming apparatus 10 according to the present embodiment.

  In the image forming apparatus 10, an image forming unit 14, a sheet conveying unit 16 for conveying a sheet 38, and an MCU 18 for controlling the image forming unit 14 are provided in a housing 12. The MCU 18 is connected to a main controller 20 that controls the entire image forming apparatus 10.

(Image forming unit 14)
FIG. 2 is a schematic diagram of the image forming unit 14 and the sheet conveying unit 16.

  The image forming unit 14 includes a photosensitive drum 22 as a photosensitive member that rotates at a constant speed in the direction of arrow A in FIG.

  Around the photoconductor drum 22, a charging unit 24, an exposure unit 26, a development unit 28, a transfer roll 30, and a cleaner 32 are arranged along the rotation direction of the photoconductor drum 22 (clockwise direction indicated by an arrow A in FIG. 2). And an erase lamp 34 are arranged in this order.

  Hereinafter, the charging unit 24, the exposure unit 26, the developing unit 28, the transfer roll 30, the cleaner 32, and the erase lamp 34 may be collectively referred to as an image forming mechanism unit. Further, the exposure unit 26, the development unit 28, the transfer roll 30, and the erase lamp 34 belong to a static elimination function group in the image forming mechanism unit.

  The exposure unit 26 employs an LED printer head (LPH). The exposure unit 26 is not limited to the LPH, and may be an optical scanning device that irradiates a rotating polygon mirror with a laser and scans the reflected light.

  After the charging unit 24 uniformly charges the surface of the photoconductor drum 22, the exposure unit 26 irradiates a light beam to form a latent image on the photoconductor drum 22.

  The developing unit 28 supplies toner to the latent image formed on the photosensitive drum 22 by the light beam, so that a toner image is formed on the photosensitive drum 22.

  The toner image on the photosensitive drum 22 is transferred by a transfer roll 30 onto a sheet 38 as a recording medium. Hereinafter, the area where the toner image is transferred may be referred to as a “transfer section TR”.

  After the transfer in the transfer unit TR, the toner remaining on the photoconductor drum 22 is removed by the cleaner 32, the charge is removed by the erase lamp 34, and then charged again by the charging unit 24, and the same image forming process is performed. It is possible to repeat.

  On the other hand, the paper 38 on which the toner image has been transferred by the transfer unit TR is conveyed to a fixing unit 40 including a pressure roller 40A and a heating roller 40B, and subjected to a fixing process. Thus, the toner image is fixed, and a desired image is formed on the paper 38. The paper 38 on which the image has been formed is discharged out of the apparatus.

  Note that the image is not directly transferred from the photosensitive drum 12 to the sheet, but is primarily transferred to an intermediate transfer member (formed by a belt or a drum), and then secondary transferred to the sheet (corresponding to the transfer in the transfer unit TR). ).

  In the case of a color image, a plurality of (for example, four for each color of CMYK) image forming units are arranged, and toner images of each color are superimposed and transferred (primary transfer) to an intermediate transfer belt, and then transferred to a sheet at a transfer unit. (Secondary transfer) and then a fixing process.

(Details of the transport system for the paper 38)
As shown in FIG. 1, the image forming apparatus 10 is provided with a plurality of supply units 82 that supply the paper 38 to the image forming unit 14. The supply devices 82 can be pulled out to the front side (left side in FIG. 1) of the image forming apparatus 10, respectively, and the paper 38 is loaded (supplemented) with the supply device 82 pulled out from the image forming apparatus 10.

  The supply device 82 has different storage containers 84 for storing paper such as plain paper and thick paper for each type. As the type of the paper 38, for example, A3 plain paper, A3 thick paper, A4 plain paper, and A4 thick paper are loaded according to the user's selection in order from the top.

  The supply device 82 has a transport roll 86 that takes out the uppermost paper 38 stored in the storage container 84 and transports the taken out paper 38 toward the image forming unit 14.

  As shown in FIGS. 1 and 2, the image forming apparatus 10 is provided with a paper transport unit 16 used for transporting a paper 38. The paper transport section 16 has a main transport path 88, a reverse transport path 90, and a sub transport path 91.

  The main transport path 88 is used for transporting the paper 38 supplied from any of the supply devices 82 to the image forming unit 14 and discharging the paper 38 on which an image has been formed to the outside of the image forming apparatus 10.

  Along the main transport path 88, in order from the upstream side in the direction in which the paper 38 is transported, the transport roll 86, the registration roll 92, the transfer roll 30, the fixing unit 40 (the pressure roller 40A and the heating roller 40B) , And a discharge roll 94.

  The registration roll 92 temporarily stops, for example, in a state where the leading end of the paper 38 conveyed from the supply device 82 is sandwiched, and the paper 38 is moved so as to coincide with the timing at which the toner image is transferred to the transfer unit TR. To the transfer roll 30.

  The discharge roll 94 discharges the paper 38 on which the toner of each color is fixed by the fixing unit 40 to the outside of the image forming apparatus 10.

  The reversing conveyance path 90 is a conveyance path used for reversing the sheet 38 having the toner image fixed on one surface thereof and supplying the sheet 38 to the image forming unit 14 again.

  A pair of reverse transport rolls 96 are appropriately disposed along the reverse transport path 90, for example. The paper 38 is supplied to the reverse conveyance path 90 from the rear end side by the reverse rotation of the discharge roll 94 while the rear end of the paper 38 is sandwiched by the discharge rollers 94, and the supplied paper 38 is The sheet is transported to a position upstream of the registration roll 92 by the reverse transport rollers 96.

  The sub-transport path 91 is a transport path for supplying a sheet 38 different from the sheet 38 stored in the supply device 82 to the image forming unit 14. The sheet 38 is supplied to the sub-conveying path 91 from the left side surface of the image forming apparatus 10 in FIG. 1 with the supply opening / closing section 98 opened. In the sub-transport path 91, a transport roll 99 is provided. The transport roll 99 transports the paper 38 supplied to the sub-transport path 91 toward the image forming unit 14.

(Engine control system)
FIG. 3 is a block diagram of a control system of the image forming apparatus.

  The main controller 20 is connected to a user interface 42 as an example of a notifying unit. The user is instructed to perform image formation and the like by an operation of the user, and notifies the user of information at the time of image formation and the like.

  The main controller 20 is connected to a network line with an external host computer (not shown), and receives image data via the network line.

  When image data is input, the main controller 20 analyzes, for example, print instruction information and image data included in the image data, and converts the data into a format (for example, bitmap data) compatible with the image forming unit 14. , And sends the converted image data to the image forming processing control unit 44 functioning as a part of the MCU 18.

  In the image forming process control unit 44, based on the input image data, together with the image forming process control unit 44, a drive system control unit 46 as an example of a transport control device that functions as the MCU 18, a charging control unit 48, an exposure control The section 50, the transfer control section 52, the fixing control section 54, the static elimination control section 56, the cleaner control section 58, and the development control section 60 are controlled synchronously to execute image formation. In the present embodiment, the functions executed by the MCU 18 are classified into blocks and described, and the hardware configuration of the MCU 18 is not limited.

  A temperature sensor 62, a humidity sensor 64, and the like are connected to the main controller 20, and the environmental temperature and humidity in the housing 12 of the image forming apparatus 10 may be detected based on the temperature sensor 62 and the humidity sensor 64. .

  Here, when image formation is continued in image forming section 14 in the present embodiment, as shown in FIG. 4A, sheet 38 is sandwiched between photoreceptor drum 22 and transfer roll 30. Since the transfer step is indispensable, the photosensitive drum 22 and the paper 38 come into contact with each other, and the surface of the photosensitive drum 22 may be abraded to some extent.

  FIG. 4B is a cross-sectional view of the photosensitive drum 22.

  The photosensitive drum 22 has a cylindrical base material 100 serving as a shaft core made of metal (made of aluminum). Around the base material 100, an undercoat layer 102, a charge generation layer 104, And the charge transport layer 106 is provided in a layered manner.

  The undercoat layer 102 has a role of a base for holding the charge generation layer 104, and is basically conductive, but may have a resistance as needed.

  The charge generation layer 104 has a function of generating a positive charge when a voltage is applied to the photosensitive drum 22 from the charging unit 24 (see FIG. 4A).

  The charge transport layer 106 is an insulator, and is a layer in which a negative charge is charged on the surface layer according to the charge generation layer 104 and a positive charge is transported when exposed to light. It is an important layer.

  In the present embodiment, an appropriate layer thickness (sometimes referred to as a film thickness) of the charge transport layer 106 is 30 μm to 40 μm.

  As described above, since the charge transport layer 106 directly faces the paper 38, the charge transport layer 106 is worn.

  FIG. 5 is an electric field E-current i characteristic diagram between the surface of the charge transport layer 106 and the substrate 100. The electric field E is represented by a potential difference V / distance L between the surface of the charge transport layer 106 and the substrate 100 (E = V / L). Note that the undercoat layer 102 is a conductor, and the charge generation layer 104 is an insulator, but has a thickness on the order of 1/1000 of the charge transport layer 106 (for example, 0.03 μm to 0.04 μm). Here, the distance L depends on the thickness of the charge transport layer 106 (distance L ≒ the thickness of the charge transport layer 106).

  As shown in FIG. 5, the charge transport layer 106 functions as an insulator if it is within the range of use (see the arrow Ea in FIG. 5). However, when the distance L decreases, the electric field E increases, and the electric field E increases. It can be seen that the current i suddenly flows outside the range.

  That is, when the charge transport layer 106, which is an insulator, is worn and the layer thickness becomes thinner than an appropriate layer thickness, the charge transport layer 106 is affected by the negative charge charged on the surface layer, and the positive charge of the charge generation layer 104 is increased. The charge moves (that is, a current flows), and the result is equivalent to that of the exposure.

  The average thickness of the photoconductor drum 22 can be obtained by detecting the current when the entire surface of the photoconductor drum 22 is exposed, as the thickness of the charge transport layer 106.

  On the other hand, regarding the partial wear (uneven wear) of the photosensitive drum 22, the average layer thickness is determined to be benign, and as a result, the image quality is reduced until a streak-like image appears in the wear occurrence area. In some cases, the inducing factor (wear) cannot be recognized. For this reason, there may be a problem that the operation of replacing the photosensitive drum 22 (see FIG. 4A) is delayed.

  Therefore, in the present embodiment, when the charge transport layer 106 is worn out, the current generated by the movement of the positive charge of the charge generation layer 104 (hereinafter, referred to as “leakage current”) is detected and detected. By comparing the detected current value with a threshold value, uneven wear is specified. For this reason, a current detection unit 108 (see FIG. 4A) is provided between the charging control unit 48 and the charging unit 24 as an example of a unit that detects a current value flowing through the charging unit 24.

  The current detection unit 108 detects a current value (leakage current) after the charging unit 24 sufficiently charges the photosensitive drum 22.

  By the way, as shown in FIG. 4A, a path of a current flowing from the photoconductor drum 22 is provided to the image forming unit 14 at the time of exposure of the exposure unit 26, at the time of development of the development unit 28, and at the time of transfer by the transfer roll 30. , There is a time of static elimination by the erase lamp 34.

For this reason, when detecting the current value after the charging in the charging unit 26 is completed, the following preprocessing is executed.
(Preprocessing 1) The exposure of the exposure unit 26 is turned off.
(Preliminary Processing 2) Since the movement of the toner corresponds to the current, the developing unit 28 may be set to a potential without toner development (for example, −600 V if the charging unit 24 is −700 V).
(Pretreatment 3) The transfer potential by the transfer roll 30 is turned off.
(Preliminary process 4) The charge removal potential by the erase lamp 34 is turned off.

  After the pre-processing 1 to pre-processing 4, the charging unit 24 charges the photosensitive drum 22 (see the characteristic curve A based on the left vertical axis in FIG. 6). 6 (the horizontal axis of FIG. 6), the current value between the charging unit 24 and the photosensitive drum 22, that is, the charging unit DC current value (see the characteristic curve B based on the vertical axis on the right end of FIG. 6) gradually decreases. When charging occurs, no current flows. Although the current value is theoretically 0 after charging, the current may flow with an error within an allowable range even with a normal layer thickness.

  Even if a current flows with an error within an allowable range, if no leakage current is generated, the charge amount Qout of the charging unit 24 when the photoconductor drum 22 starts to make one rotation and the photoconductor drum 22 become 1 The charge amount Qin at the end of the round becomes the same (Qout ≒ Qin) within the allowable range of the error.

  In other words, when a current value ΔI equal to or greater than the predetermined threshold value flows through the charging unit 24, a leakage current occurs, and the photosensitive drum 22 has uneven wear.

  In the present embodiment, the image forming process control unit 44 (see FIG. 3) of the MCU 18 monitors the leakage current (current value ΔI flowing through the charging unit 24) and determines whether or not there is uneven wear. The control subject is not limited to the image forming processing control unit 44, and may be a control device represented by the main controller 20 or an external PC.

  FIG. 7 is a block diagram in which the flow of uneven wear monitoring control executed by the image forming processing control unit 44 is classified according to function. Note that this block diagram does not limit the hardware configuration for determining the presence or absence of uneven wear in the image forming processing control unit 44.

  As shown in FIG. 7, the uneven wear monitoring control is executed by a pre-processing control unit 110 and an uneven wear determination control unit 112 as an example of a determination unit.

  The pre-processing control unit 110 includes an uneven wear determination time setting unit 114, a pre-processing instruction unit 116, and a charging execution unit 118.

  The uneven wear determination time setting unit 114 sets the uneven wear determination time as the maintenance mode when the number of image forming processes reaches a predetermined number. When the uneven wear determination time comes, the uneven wear determination time setting unit 114 instructs the pre-processing instruction unit 116 to execute pre-processing. Although the wear determination is performed every predetermined number of times (periodical) in the number of image forming processes, it may be performed every predetermined date and time (period). You may go to.

  Upon receiving an execution instruction from the uneven wear determination time setting unit 114, the pre-processing instruction unit 116 executes pre-processing 1 to pre-processing 4.

  That is, the pre-processing instruction unit 116 instructs the exposure control unit 50 to turn off the exposure (pre-processing 1).

  The pre-processing instruction section 116 instructs the development control section 60 to perform non-development of toner (pre-processing 2).

  The pre-processing instruction unit 116 instructs the transfer control unit 52 to turn off the transfer (pre-processing 3).

  The pre-processing instruction unit 116 instructs the static elimination control unit 56 to turn off the static elimination (pre-processing 4).

  When the charging of the photosensitive drum 22 is completed and the processing of the pre-processing 1 to the pre-processing 4 is completed, the pre-processing control unit 116 instructs the charging execution unit 118 to execute the charging for monitoring uneven wear. . When executing the uneven wear monitoring, the charging execution unit 118 instructs the exposure control unit 28 to uniformly charge the photosensitive drum 22.

  The applied voltage at the time of monitoring uneven wear is set at -700 V, which is the same as during normal image formation. For example, at the time of monitoring uneven wear, it may be set at about -1000 V. This is because a leakage current appears remarkably. Since the leakage current appears remarkably, it is possible to detect the occurrence of uneven wear before the image quality is reduced when the image forming process is actually performed.

  When the charging of the photosensitive drum 22 is completed, the pre-processing control unit 110 outputs an execution instruction of the uneven wear determination control to the uneven wear determination control unit 112.

  The uneven wear determination control unit 112 executes uneven wear determination control based on an instruction from the pre-processing control unit 110.

  The first receiving unit 120 receives the cycle information of the photosensitive drum 22 from the drive system control unit 46. The second receiving unit 122 receives current value information from the current detecting unit 108.

  The first receiving unit 120 and the second receiving unit 122 are connected to the current value extracting unit 124.

  In the current value extraction section 124, the photosensitive drum 22 makes one rotation after the start of charging and the rotation after the rotation until the photosensitive drum 22 is sufficiently charged (for example, about 1 to 3 cycles). The current value ΔI at the start is extracted.

  The current value ΔI extracted by the current value extraction unit 124 is sent to the comparison unit 126. The threshold value memory 128 is connected to the comparing unit 126. The threshold value memory 128 stores a threshold value Is for determining whether the current is a leakage current.

  Upon receiving the current value ΔI, the comparing unit 126 reads out the threshold value Is from the threshold value memory 128 and compares them. The comparison result of the comparing unit 126 is sent to the determining unit 130 to determine whether there is uneven wear.

  That is, when the determination unit 130 receives “information that the current value ΔI exceeds the threshold value Is” from the comparison unit 126, it is determined that a leak current due to uneven wear of the photosensitive drum 22 has occurred. judge.

  On the other hand, when the determination unit 130 receives “information that the current value ΔI is equal to or less than the threshold value Is” from the comparison unit 128, it determines that uneven wear of the photosensitive drum 22 has not occurred.

  The determination result of the determination unit 130 is displayed on the display unit of the user interface 42 via the output unit 132, for example, via the main controller 20.

  The operation of the present embodiment will be described below.

  First, the procedure of the image forming process will be described.

  Image data received from the outside by the main controller 20 is converted into, for example, gradation data, and output to the image forming unit 14 via the MCU 18 (exposure control unit 50). The image forming section 14 drives the exposing section 26 in accordance with the gradation data, emits exposure light, performs scanning exposure of the photosensitive drum 22, and forms a latent image (electrostatic latent image).

  The electrostatic latent image formed on the photoconductor drum 22 is visualized as a toner image by the developing unit 28 (development). Then, the toner image formed on the photosensitive drum 22 is transferred onto the paper 38 by the transfer roll 30.

  The toner images of the respective colors on the paper 38 are fixed by the fixing unit 40, and the paper 38 after the fixing is discharged outside the apparatus (single-sided printing process), or the discharge roller 94 sandwiches the rear end of the paper 38. In this state, the sheet is sent to the reverse conveyance path 90 (double-sided printing processing).

  After the transfer of the toner image is completed, the surface of the photosensitive drum 22 is removed of residual toner, paper dust, and the like, and is discharged. It is uniformly charged during the next image forming process.

  The paper 38 (the paper 38 on which image formation on the front surface has been completed) sent to the reversing conveyance path 90 is performed by the discharge roller 94 rotating in the reverse direction while the rear end of the paper 38 is sandwiched by the discharge rollers 94. The paper 38 is supplied from the rear end side, and the supplied paper 38 is transported by the reversing transport rolls 96, 96 to a position upstream of the registration roll 92 in a state where the paper 38 is turned upside down.

  As a result, image formation on the back side is performed in the same manner as in the above-described image forming step, and is fixed by the fixing unit 40, and the sheet 38 after fixing is discharged out of the apparatus.

  In the image forming section 14 in the present embodiment, when the image formation is continued, the surface of the photoconductor drum 22 (the charge transport layer 106 shown in FIG. 4B) may be abraded to some extent. The presence or absence of average wear in the entire region of the charge transport layer 106 can be determined by the integrated current value at the time of charging, but partial wear, that is, uneven wear, may be overlooked.

  Thus, in the present embodiment, when the charge transport layer 106 is unevenly worn, the current generated by the movement of the positive charge of the charge generation layer 106 (hereinafter, referred to as “leakage current”) is specifically detected and detected. By comparing the detected current value ΔI with the threshold value Is, it is determined whether uneven wear has occurred (uneven wear monitoring).

  FIG. 8 is a flowchart for executing the uneven wear monitoring control executed by the image forming processing control unit 44 of the MCU 18.

  As shown in FIG. 8A, in step 150, it is determined whether it is time to determine uneven wear, and if a negative determination is made, it is not the time to determine uneven wear (for example, the number of times of image forming processing is predetermined. Has not been reached), and this routine ends.

  If an affirmative determination is made in step 150, it is determined that it is time to determine uneven wear (for example, the number of image forming processes has reached a predetermined number), and the process proceeds to step 152.

  In step 152, pre-processing control (see FIG. 8B) is executed. The pre-processing control C, which corresponds to the symbol a shown in FIG. 6, may be executed during the preparatory rotation of the photosensitive drum 22 before charging.

  As shown in FIG. 8B, in step 154, pre-processing 1 is executed. That is, the exposure of the exposure unit 26 is turned off, and the process proceeds to step 156.

  In step 156, pre-processing 2 is performed. That is, since the movement of the toner corresponds to the current, the developing unit 28 sets the potential without the toner development (for example, -600 V when the charging unit 24 is -700 V), and proceeds to step 158.

  In step 158, the pre-processing 3 is executed, that is, the transfer potential of the transfer roll 30 is turned off, and the process proceeds to step 160.

  In step 160, pre-processing 4 is performed. That is, the charge removing potential of the erase lamp 34 is turned off, and the process returns to step 162 in FIG.

  As shown in FIG. 8A, in step 162, the photosensitive drum 22 is charged. The charging voltage may be -700 V at the time of image forming processing, but may be intentionally increased to about -1000 V in order to make leakage current noticeable. By setting the voltage higher than the voltage at the time of the image forming process, a leakage current appears remarkably. Since the leakage current appears remarkably, it is possible to detect the occurrence of uneven wear before the image quality is reduced when the image forming process is actually performed.

  Accordingly, the charging voltage of the photoconductor drum 22 is set to −700 V to −1000 V (hereinafter, referred to as a setting range). It may be outside the setting range.

  In the next step 164, it is determined whether or not the charging completion cycle has been reached. That is, as shown by reference numeral c in FIG. 6, when the charging of the photoconductor drum 22 is started, the DC current of the charging unit is initially about -90 μA to −100 μA, and the current value gradually decreases. After that, when the charging is completed (see the reference symbol d in FIG. 6), the DC current value of the charging unit theoretically becomes 0 (saturated state). The charging completion cycle is the time of this saturation state (charging completion), and is the fourth cycle in FIG. Note that the charging completion cycle is not limited to the fourth cycle, and may be a fifth cycle or later.

  Here, in the characteristic curve B of FIG. 6, if the DC current value of the charging unit includes an allowable error and is 0 V as shown by the solid line, there is no leakage current, but the characteristic curve Bm indicated by the broken line in FIG. Leakage current may occur.

  Therefore, in the present embodiment, if an affirmative determination is made in step 164 (the fourth cycle or the fourth cycle or later, which is the charging completion cycle), the process proceeds to step 166, where the current value ΔI is detected by the current detecting unit 108. It is detected (see the symbol e in FIG. 6).

  In the next step 168, the threshold value Is is read, and then the process proceeds to step 170 to compare the current value ΔI with the threshold value Is.

  If it is determined in step 170 that ΔI ≦ Is, it is determined that the current value ΔI is within the allowable range, and the flow proceeds to step 172 to determine normality (no leakage current), and then to step 174 to return to “ This routine is terminated by notifying "no uneven wear".

  On the other hand, if it is determined in step 170 that ΔI> Is, it is determined that the current value ΔI is outside the allowable range, and the flow proceeds to step 176 to determine an abnormality (there is a leakage current), and then to step 178. The routine shifts to report "the presence of uneven wear", and this routine ends.

  Here, it is preferable to prompt the exchange of the photosensitive drum 22 in addition to the notification of “the presence of uneven wear” in Step 178.

  If the image forming apparatus 10 has a communication function, the maintenance management center or the like may be notified that the photosensitive drum 22 needs to be replaced.

  Further, as an example of the suppression unit, after the abnormality determination, the surface potential of the photosensitive drum 22 during the image forming process may be lower than the steady state potential (−700 V) (for example, −600 V).

  According to the present embodiment, when the pre-processing 1 to the pre-processing 4 (exposure off, toner non-development, transfer off, charge removal off) are completed, and the charging of the photoconductor drum 22 is completed, the current detection unit 108 sets the charging unit 24 Is detected and compared with a threshold value Is stored in advance to determine the presence or absence of a leakage current. When the information that the current value ΔI exceeds the threshold value Is is received, it is determined that the leakage current due to the uneven wear of the photosensitive drum 22 has occurred. It is possible to detect uneven wear of the photosensitive drum 22 before image quality is deteriorated.

  In the present embodiment, it is assumed that the uneven wear monitoring control is periodically performed from the time of replacement of a new product. However, the monitoring may be performed after a predetermined number of image forming processes.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Housing 14 Image forming part 16 Paper conveyance part 18 MCU
Reference Signs List 20 main controller 22 photoreceptor drum 24 charging unit 26 exposing unit 28 developing unit 30 transfer roll TR transfer unit 32 cleaner 34 erase lamp 38 paper 40A pressure roller 40B heating roller 40 fixing unit 42 user interface 44 image forming processing control unit 46 driving System control unit 48 Charging control unit 50 Exposure control unit 52 Transfer control unit 54 Fixing control unit 56 Static elimination control unit 58 Cleaner control unit 60 Development control unit 62 Temperature sensor 64 Humidity sensor 82 Supply device 84 Storage container 86 Transport roll 88 Main transport path Reference Signs List 90 reverse transport path 91 sub transport path 92 registration roll 94 discharge roll 96 reverse transport roll 98 supply opening / closing section 99 transport roll 100 base material 102 undercoat layer 104 Charge generation layer 106 Charge transport layer 108 Current detection unit 110 Pre-processing control unit 112 Uneven wear determination control unit 114 Uneven wear determination time setting unit 116 Pre-processing instruction unit 118 Charging execution unit 120 First reception unit 122 Second reception unit 124 Current value extraction unit 126 Comparison unit 128 Threshold memory 130 Judgment unit 132 Output unit

Claims (6)

An image forming mechanism unit including a charging unit having a function of charging the surface of the photoconductor, and a static elimination function group including a static elimination function unit having a function of neutralizing the surface of the photoconductor,
Blocking means for blocking the static elimination operation by the static elimination function group;
Under the condition that the charge removal operation is interrupted by the interrupting unit and the charging is performed in the saturated state by the charging unit, the occurrence of uneven wear on the surface of the photoconductor is determined using a current value flowing through the charging unit and a threshold value. determining means for determining whether the possess,
When the determination unit determines that uneven wear of the surface of the photoconductor has occurred, the surface potential of the photoconductor due to the charging by the charging unit is reduced to be lower than the potential at the time of steady image forming processing. An image forming apparatus which continues image forming processing while suppressing leakage current of the image forming apparatus.   2. A value of a current flowing through the charging unit when the determination unit determines occurrence of uneven wear is a leakage current value between a grounded substrate and an insulating layer which is a surface of the photoconductor. The image forming apparatus as described in the above.   An exposing section for forming an electrostatic latent image on the surface of the photoreceptor, a developing section for developing the electrostatic latent image with toner, and a transfer for transferring a toner image developed by the developing section to a transfer target body The image forming apparatus according to claim 1, further comprising at least one of a unit and a charge removing unit configured to remove a charge on a surface of the photoconductor.   4. The image forming apparatus according to claim 1, wherein when the determination unit determines occurrence of uneven wear, a surface potential of the photoconductor due to charging by the charging unit is higher than a potential at the time of image forming processing. 5. The image forming apparatus according to claim 1.   The image forming apparatus according to any one of claims 1 to 4, wherein the charging condition in the saturated state is satisfied, wherein the photosensitive member is rotated more than a predetermined number of times.   6. The notification device according to claim 1, further comprising a notification device for notifying that replacement of the photoconductor is prompted when the determination unit determines that uneven wear of the surface of the photoconductor has occurred. Image forming apparatus.