Image forming apparatus, control method for image forming apparatus, and control program for image forming apparatus

Abstract

To provide an image forming device with which it is possible to change a life reference value for replacing an image carrier in accordance with reasons for replacement.SOLUTION: Provided is an image forming device 100 comprising: an acquisition unit 60 for acquiring a value regarding an image density at positions corresponding to at least two points in the longitudinal direction of an image carrier 11; a calculation unit 111 for calculating, as a first density difference, the difference in values regarding image densities at least two points having been acquired from the image carrier 11 before replacement, and calculating, as a second density difference, the difference in values regarding image densities at least two points having been acquired from the image carrier 11 after replacement; and a change unit 112 for changing the preliminarily set life reference value of the image carrier 11 when the difference value between the first and the second density differences is greater than or equal to a prescribed value.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus, a control method for an image forming apparatus, and a control program for an image forming apparatus. [Background technology]

[0002] Electrophotographic image forming devices form a toner image on an image carrier (photoreceptor) through charging, exposure, and development, and then transfer and fix the toner image on the image carrier to a recording material such as paper. In such image forming devices, various parts wear out with use. Therefore, worn parts must be replaced. Wear of the image carrier, in particular, affects the quality of the images formed.

[0003] Conventional technologies relating to part replacement include, for example, Patent Documents 1 and 2. In Patent Document 1, when replacing a worn part, the lifespan of the newly installed part can be changed depending on the reason for replacing the worn part. In Patent Document 2, a part replacement reference value is determined in advance, and the part replacement reference value is changed by inputting the degree of use of the worn part and the degree of wear of that part. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-011674 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-014354 Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 1, the lifespan of a newly installed part is changed according to the amount of operation at the time of replacement of the worn part, and the lifespan of that part is determined. However, in Patent Document 1, if the reason for replacement is irregular, there is a possibility that the cause will not be noticed and an incorrect lifespan will be set.

[0006] Furthermore, in Patent Document 2, it is not possible to accurately determine whether the reason for replacing a worn part is due to its lifespan or irregularity, so there is a possibility that the replacement reference value will be changed to an incorrect value.

[0007] Therefore, an object of the present invention is to provide an image forming apparatus, a control method for an image forming apparatus, and a control program for an image forming apparatus that can change the life standard value for replacing an image carrier depending on the reason for replacement. [Means for solving the problem]

[0008] The above object of the present invention can be achieved by the following means.

[0009] (1) an acquisition unit that acquires values ​​relating to image density at positions corresponding to at least two positions in the longitudinal direction of an image carrier; a calculation unit that calculates a difference between the values ​​relating to the image density at the at least two locations obtained from the image carrier before replacement as a first density difference, and calculates a difference between the values ​​relating to the image density at the at least two locations obtained from the image carrier after replacement as a second density difference; a change unit that changes a preset life reference value of the image carrier when a difference value between the first density difference and the second density difference is equal to or greater than a predetermined value; An image forming apparatus comprising:

[0010] (2) The image forming apparatus according to (1), wherein the acquisition unit acquires the value relating to the image density from one end and the other end in the longitudinal direction of the image carrier.

[0011] (3) The image forming apparatus according to (1), wherein the acquisition unit acquires the value relating to the image density from at least one end and a center portion in the longitudinal direction of the image carrier.

[0012] (4) The acquisition unit The image forming apparatus according to any one of (1) to (3) above, wherein the density sensor is at least one of a density sensor that measures the image density on the image carrier, a density sensor that measures the image density on an intermediate transfer belt onto which the image on the image carrier is transferred, and a density sensor that measures the image density on a recording material onto which the image is transferred from the intermediate transfer belt.

[0013] (5) The acquisition unit The image forming apparatus according to any one of (1) to (3) above, wherein a voltage to be applied to the image carrier when developing the latent image on the image carrier is stored.

[0014] (6) The change unit The image forming apparatus according to any one of (1) to (5) above, wherein the life reference value of the image carrier is changed based on usage information of the image carrier.

[0015] (7) The image forming apparatus according to (6) above, wherein the usage information includes at least one of the usage environment of the image forming apparatus, toner density, print coverage, and ratio of monochrome mode to color mode.

[0016] (8) a step (a) of acquiring values ​​relating to image density at positions corresponding to at least two positions in the longitudinal direction of the image carrier before replacement; a step (b) of acquiring values ​​relating to image density at positions corresponding to at least two positions in the longitudinal direction of the image carrier after replacement; a step (c) of calculating a difference between the values ​​relating to the image density at the at least two locations obtained from the image carrier before replacement as a first density difference, and a difference between the values ​​relating to the image density at the at least two locations obtained from the image carrier after replacement as a second density difference; a step (d) of changing a preset reference life value of the image carrier when a difference value between the first density difference and the second density difference is equal to or greater than a predetermined value; A control method for an image forming apparatus comprising:

[0017] (9) The steps (a) and (b) The control method for an image forming apparatus according to (8) above, further comprising obtaining the value relating to the image density from one end and the other end in the longitudinal direction of the image carrier.

[0018] (10) The steps (a) and (b) The control method for an image forming apparatus according to (8) above, further comprising obtaining the value relating to the image density from at least one end portion and a central portion in the longitudinal direction of the image carrier.

[0019] (11) The steps (a) and (b) a density sensor for measuring the density of the image on the image carrier; and a density sensor for measuring the density of the image on an intermediate transfer belt onto which the image on the image carrier is transferred. And the control method for an image forming apparatus according to any one of (8) to (10) above, wherein the image density is obtained by at least one density sensor among density sensors that measure the image density on a recording material onto which an image has been transferred from an intermediate transfer belt.

[0020] (12) The steps (a) and (b) The control method for an image forming apparatus according to any one of (8) to (11) above, wherein when developing a latent image on the image carrier, a voltage applied to the image carrier is obtained as a value related to the image density.

[0021] (13) calculating a first density difference as a difference between values ​​relating to image density acquired from positions corresponding to at least two positions in the longitudinal direction of the image carrier before replacement, and a second density difference as a difference between values ​​relating to image density acquired from positions corresponding to at least two positions in the longitudinal direction of the image carrier after replacement; changing a preset reference life value of the image carrier when a difference value between the first density difference and the second density difference is equal to or greater than a predetermined value; A control program for an image forming apparatus comprising:

[0022] (14) The value relating to the image density is The control program for an image forming apparatus according to (13) above, wherein the values ​​are acquired from one end and the other end of the image carrier in the longitudinal direction.

[0023] (15) The value relating to the image density is The control program for an image forming apparatus according to (13) above, wherein the values ​​are acquired from at least one end and a center of the image carrier in the longitudinal direction. [Effects of the Invention]

[0024] The present invention determines whether the image carrier has reached the end of its life from the difference in image density between at least two positions in the longitudinal direction of the image carrier before and after replacement, and changes the life reference value of the replaced image carrier. This allows the present invention to change the life reference value for replacing the image carrier depending on the reason for replacement. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a schematic diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram illustrating a control unit of the image forming apparatus. [Figure 3A] FIG. 2 is a front view showing an example of the arrangement of a density sensor relative to an image carrier. [Figure 3B] FIG. 10 is a front view showing another example of the arrangement of the density sensor relative to the image carrier. [Figure 4] FIG. 2 is a schematic diagram illustrating an example of the configuration of a concentration sensor. [Figure 5] 10 is a main routine flowchart illustrating a procedure for changing a life reference value of an image carrier. [Figure 6]10 is a subroutine flowchart illustrating a noise determination procedure. [Figure 7] 10 is a graph showing the predicted results of the film thickness of an image carrier in an ideal case of the charging current and film thickness of the image carrier. [Figure 8] 10 is a graph showing the predicted results of the film thickness of the image carrier when there is variation in the charging current and film thickness of the image carrier. [Figure 9] 10 is a graph showing the results of predicting the film thickness of a high-hardness image carrier. [Figure 10] 10 is a graph for explaining film scraping of an image carrier. [Figure 11] 10 is a graph for explaining the film thickness of an image carrier that has reached the end of its life. [Figure 12] 10 is a graph for explaining the film thickness of a new image carrier. [Figure 13] 10 is a graph for explaining the film thickness of an image carrier in which irregular FD streak noise occurs. [Figure 14] 10 is a graph showing the change in film thickness from the front side to the back side of the image carrier in the first image forming apparatus. [Figure 15] 10 is a graph showing the transition of film thickness from the front side to the back side of the image carrier in the second image forming apparatus. [Figure 16] FIG. 4 is a front view illustrating the state of a primary transfer roller of the first image forming apparatus. [Figure 17] FIG. 10 is a front view illustrating the state of a primary transfer roller of the second image forming apparatus. [Figure 18] 10 is a graph showing the amount of toner adhered to an intermediate transfer belt relative to the film thickness of an image carrier. [Figure 19] 10 is a graph showing the change in film thickness of an image bearing member. [Figure 20] 10 is a graph showing the difference in the change in potential Vdc when an image having a constant exposure amount and an image density is formed. [Figure 21] 1 is a graph showing the usage environment of an image forming apparatus and the transition of the average film thickness of an image carrier at that time. [Figure 22]10 is a graph showing the toner concentration of an image forming apparatus and the change in the average film thickness of an image carrier at that time. [Figure 23] 10 is a graph showing the print coverage of an image forming apparatus and the change in the average film thickness of an image carrier at that time. [Figure 24] 10 is a graph showing the ratio of monochrome mode to color mode of the image forming apparatus and the change in average film thickness of the image carrier at that time. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicate explanations will be omitted. Furthermore, the dimensional proportions in the drawings are exaggerated for the convenience of explanation and may differ from the actual proportions.

[0027] (Image forming device) FIG. 1 is a schematic diagram showing the configuration of an image forming apparatus according to one embodiment of the present invention.

[0028] As shown in FIG. 1, an image forming apparatus 100 of this embodiment includes image forming sections 10Y, 10M, 10C, and 10K, a conveying section 20, an intermediate transfer belt 30, and a fixing section .

[0029] Each of the image forming units 10Y, 10M, 10C, and 10K has an image carrier 11, a charging unit 12, an exposure unit 13, a developing unit 14, a cleaning blade 15, and a primary transfer roller 16. The toner images of each color formed by each of the image forming units 10Y, 10M, 10C, and 10K are transferred in sequence onto the intermediate transfer belt 30 and combined on the intermediate transfer belt 30.

[0030] The image carrier 11 is also called a photosensitive member because an electrostatic latent image (also simply called a latent image) is formed on it by light.

[0031] In the description of this embodiment, the image carrier 11 is a high-hardness image carrier having a high-hardness layer on its surface. However, this embodiment is not limited to high-hardness image carriers, and can also be applied to image carriers 11 that do not have a high-hardness layer.

[0032] The entire surface of the image carrier 11 is charged by the charging unit 12, and then a latent image is formed on the image carrier 11 by exposure according to image data by the exposure unit 13. Here, latent images of each color are formed by image forming units 10Y, 10M, 10C, and 10K for each color. When there is no need to distinguish between the image forming units 10Y, 10M, 10C, and 10K for each color or when they are referred to collectively, they will be simply referred to as image forming units 10.

[0033] The developing units 14 contain toners of colors corresponding to the image forming units 10Y, 10M, 10C, and 10K. The developing units 14 supply lubricants to the image carrier 11 along with the toners. The latent images formed on the image carrier 11 are developed by the developing units 14 with toners of the respective colors. The respective colors are yellow (Y), magenta (M), cyan (C), and black (K).

[0034] The developed toner images of each color are transferred onto the intermediate transfer belt 30 (primary transfer) and are sequentially superimposed to form a full-color toner image. A transfer roller 31 and a cleaning blade 32 are in contact with the intermediate transfer belt 30. A transfer nip 33 is formed by the intermediate transfer belt 30 and the transfer roller 31.

[0035] The cleaning blade 15 scrapes off unnecessary toner from the surface of the image carrier 11 to clean the surface of the image carrier 11 .

[0036] The primary transfer roller 16 presses the intermediate transfer belt 30 toward the image carrier 11 .

[0037] The toner image on the intermediate transfer belt 30 is transferred to the surface of a recording material S (e.g., paper) at the transfer nip 33. An unfixed image 50 is formed on the surface of the recording material S. Therefore, the intermediate transfer belt 30, the transfer roller 31, and the transfer nip 33 formed thereby form a transfer section. The unfixed image 50 on the recording material S is transported to the fixing section 40 and fixed thereon.

[0038] The conveying section 20 includes a paper feed roller 22, a timing roller 23, and a paper discharge roller .

[0039] The conveying section 20 conveys the recording material S taken out from the paper feed tray 21 to the transfer nip 33 by the paper feed roller 22 and the timing roller 23 .

[0040] The fixing section 40 passes the recording material S on which the unfixed image 50 has been formed through a fixing nip 41, and fixes the unfixed image 50 onto the surface of the recording material S by applying pressure and heat.

[0041] The recording material S on which the image has been fixed is output by a paper discharge roller 26 onto a paper discharge tray (not shown) or the like.

[0042] Next, a description will be given of a control unit of the image forming apparatus 100. FIG.

[0043] The control unit 110 has an image formation control unit 120, a calculation unit 111, a change unit 112, and a storage unit 113. The control unit 110 is connected to the image forming unit 10, the conveyance unit 20, the fixing unit 40, and the acquisition unit 60 via a signal line 90.

[0044] The control unit 110 is a computer provided by a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), and storage unit 113. The CPU provides the functions of the image formation control unit 120, the change unit 112, and the calculation unit 111 by executing a predetermined program.

[0045] The image formation control unit 120 controls the image forming unit 10, the conveying unit 20, the fixing unit 40, and the like to perform the image forming operation.

[0046] Based on the signal from the acquisition unit 60, the calculation unit 111 calculates the difference in image density at positions corresponding to at least two locations in the longitudinal direction of the image carrier 11 before and after replacement of the image carrier 11. Specifically, the calculation unit 111 calculates the difference in image density at the two locations acquired by the first and second density sensors from the image carrier 11 before replacement as a first density difference, and calculates the difference in image density at the two locations acquired by the first and second density sensors from the image carrier 11 after replacement as a second density difference. Details of the first and second density sensors will be described later.

[0047] When the difference between the first density difference and the second density difference is equal to or greater than a predetermined value, the change unit 112 changes the previously set life reference value of the image carrier 11. Here, "setting" means storing in the memory unit 113. Therefore, the set life reference value of the image carrier 11 is stored in the memory unit 113 (same below).

[0048] The storage unit 113 is provided by a hard disk drive (HDD), a solid state drive (SSD), or other storage device. The storage unit 113 stores various values, processing (calculation) results, and the like in each process described below. The processing results, and the like, may be temporarily stored in RAM in the control unit 110.

[0049] The acquisition unit 60 acquires image density at positions corresponding to at least two locations in the longitudinal direction of the image carrier 11. In this embodiment, the acquisition unit 60 is two density sensors. In the following description, the rear side in the longitudinal direction of the image carrier 11 will be simply referred to as the rear side, and the front side in the longitudinal direction of the image carrier 11 will be simply referred to as the front side.

[0050] 3A is a front view showing an example of the arrangement of a density sensor relative to the image carrier 11. The front view is a view of the image carrier 11 as seen from upstream to downstream in the recording material conveyance direction. The same applies to the other figures.

[0051] The density sensors shown in FIG. 3A are a first density sensor 61 and a second density sensor 62. The first density sensor 61 is disposed at the rear end of the image carrier 11. The second density sensor 62 is disposed at the front end of the image carrier 11. Here, the end refers to the end within the range where an image can be formed. Note that the first density sensor 61 and the second density sensor 62 will be simply referred to as density sensors when they are not distinguished from each other or when they are referred to collectively.

[0052] 3B is a front view showing another example of the arrangement of density sensors relative to the image carrier 11. The density sensors shown in FIG. 3B are a first density sensor 61 and a third density sensor 63. The first density sensor 61 is arranged on the front side of the image carrier 11. The third density sensor 63 is arranged in the center of the image carrier 11 in the longitudinal direction.

[0053] 3A and 3B, the density sensors may be arranged in three locations (not shown), for example, at both ends and the center in the longitudinal direction of the image carrier 11. When density sensors are arranged in three or more locations, the calculation unit calculates the differences between the signals (density values) from each density sensor. The calculation unit then determines the largest of the calculated differences as the first density difference and the second density difference. Specifically, the calculation unit first calculates (density value of the first density sensor) - (density value of the second density sensor), (density value of the first density sensor) - (density value of the third density sensor), and (density value of the second density sensor) - (density value of the third density sensor). The calculation unit then determines the largest absolute value of these calculated values ​​as the first density difference and the second density difference.

[0054] 4 is a schematic diagram showing an example of the configuration of a density sensor. The density sensor has a light-emitting unit 601 and a light-receiving unit 602. The light-emitting unit 601 emits light toward the image carrier 11. The light-receiving unit 602 receives the light reflected from the image carrier 11. The density sensor detects the density of the toner image 55 on the image carrier 11 based on the intensity of the light received by the light-receiving unit 602. The detected density is input to the control unit 110.

[0055] The first to third density sensors 61, 62, and 63 all detect the density of the toner image formed on the image carrier 11. This makes it possible to directly grasp the state of the image carrier 11 for each color. In particular, the first to third density sensors 61, 62, and 63 measure the image density directly from the image carrier 11, so they can make judgments without being affected by the developing unit 14 (developer carrier) or the intermediate transfer belt 30.

[0056] However, the acquisition unit 60 is not limited to this, and may be, for example, a density sensor for detecting the density of the toner image formed on the intermediate transfer belt 30. In this case, the density sensor also acquires image density at positions corresponding to at least two locations on the image carrier 11. In this case, the number of density sensors can be reduced compared to when one sensor is provided for each image carrier 11.

[0057] The acquisition unit 60 may also be a density sensor for detecting the image density of the recording material S after fixing. In this case, the density sensor also acquires the density at positions corresponding to at least two locations on the image carrier 11. The density sensor for detecting the image density of the recording material can be a sensor provided for color adjustment or image position adjustment. The sensor provided for color adjustment or image position adjustment is, for example, a line image sensor (including a contact line image sensor) in which pixels are arranged in a direction perpendicular to the conveyance direction of the recording material, i.e., in the same direction as the longitudinal direction of the image carrier 11.

[0058] Furthermore, the acquiring section 60 may record, for example, the potential Vdc applied to the image carrier 11 during image formation. In this case, the function of the acquiring section 60 is achieved as follows.

[0059] First, the user causes the image forming unit 10 to print an image of the desired density. The image of the desired density should be, for example, a solid image with a density of 50% or more across the entire surface of the recording material, which makes it easy to measure the density. The user then stores the potential Vdc applied to the image carrier 11 at that time in the memory unit 113. The potential Vdc stored at this time is the potential Vdc at the rear side of the image carrier 11.

[0060] Next, the user measures and compares the density on the recording material S at positions corresponding to the rear side of the image carrier 11 and the front side of the image carrier 11. The density measurement may be performed by a density sensor built into the image forming apparatus 100, or may be performed by a density sensor provided separately from the image forming apparatus 100.

[0061] Next, the user causes the image forming unit 10 to print on the recording material S while changing the density until the density on the rear side of the image carrier 11 and the density on the front side of the image carrier 11 become the same. The user then records the potential Vdc at that time.

[0062] Then, the user records the potential Vdc at the time when the density on the rear side of the image carrier 11 and the density on the front side of the image carrier 11 become the same as the potential Vdc on the front side of the image carrier 11.

[0063] In this way, the potential Vdc on the rear side of the image carrier 11 and the potential Vdc on the front side of the image carrier 11 are obtained. The same procedure is followed when obtaining the potential Vdc at three locations, including the center of the image carrier 11, and the user records the bias voltage applied to the printed image carrier 11 when the densities at the three locations are the same.

[0064] (Procedure for changing the reference life value of the image carrier 11) Next, a description will be given of a procedure for changing the life reference value of the image carrier 11. Fig. 5 is a main routine flowchart for explaining the procedure for changing the life reference value of the image carrier 11. The control unit 110 (CPU) executes a program created in accordance with this procedure.

[0065] In the procedure described here, image densities at two locations are obtained using the first density sensor 61 and the second density sensor 62 shown in Fig. 3A. The life reference value of the image carrier 11 initially stored in the memory unit 113 is set to 2000 krot.

[0066] First, the control unit 110 acquires image densities at two locations on the image carrier 11 (S101). This image density is, for example, constantly measured by the first density sensor 61 and the second density sensor 62. The control unit 110 stores the latest measured value in the memory unit 113. This image density is also measured, for example, by preparing a maintenance mode for replacing the image carrier 11 and executing image formation. The control unit 110 stores the image density measured in the maintenance mode in the memory unit 113. Note that when a bias voltage is used as a value related to the image density, a maintenance mode is prepared and the potential Vdc during development is stored as described above.

[0067] Next, the user replaces the image carrier 11 (S102). The reason for the replacement at this time is, for example, the occurrence of FD streak noise.

[0068] Then, the control unit 110 stores the rotation speed of the image carrier 11 at the time of replacement (S103). Whether the image carrier 11 has been replaced is determined, for example, by the on / off state of a switch provided to recognize the presence of the image carrier 11. Here, the rotation speed of the image carrier 11 at the time of replacement is, for example, 1800 krot.

[0069] Next, the control unit 110 acquires the image densities at two locations when an image is formed by the replaced image carrier 11 (S104).

[0070] Next, the control unit 110 determines whether the FD streak noise is caused by wear due to end of life (S105). This determination is performed as the functions of the calculation unit 111 and the change unit 112 as follows.

[0071] FIG. 6 is a subroutine flowchart for explaining the noise determination procedure.

[0072] First, the control unit 110 calculates a first density difference from the image densities at the two locations acquired in S101 (before replacement) (S151).

[0073] Next, the control unit 110 calculates a second density difference from the image densities at the two locations acquired in S104 (after replacement) (S152).

[0074] Next, the control unit 110 calculates the difference value between the first density difference and the second density difference (S153).

[0075] Next, the control unit 110 compares the difference value with a predetermined value (S154).

[0076] If the result of the comparison shows that the difference is equal to or greater than a predetermined value (difference ≧ predetermined value) (S154: YES), the control unit 110 determines that the FD streak noise is caused by wear due to lifespan (S155). In other words, if (difference ≧ predetermined value), it is determined that the image carrier 11 has reached the end of its lifespan.

[0077] On the other hand, if the result of the comparison shows that the difference value is not equal to or greater than the predetermined value (difference value ≧ predetermined value) (S154: NO), the control unit 110 determines that the FD streak noise is caused by something other than wear and tear (S156). In other words, if the difference value is not equal to or greater than the predetermined value, the generated noise is determined to be irregular and caused by something other than the lifespan of the image carrier 11.

[0078] The predetermined value for determining whether wear is the cause is determined in advance through experiments or experience (past performance). The predetermined value is determined, for example, from the difference between the first density difference due to an image carrier 11 that has reached the end of its life and the second density difference due to a brand new image carrier 11 of the same model. The predetermined value may be determined directly from an experimental value or an empirical value, or may be determined with a certain margin added. The determined predetermined value is stored in the memory unit 113.

[0079] Thereafter, the process returns from the subroutine to the main routine.

[0080] If the result of S105 indicates that the FD streak noise is caused by wear (S106: YES), the control unit 110 then sets the life reference value to 1800 krots, which is the rotation speed stored in S103 (S107). Thereafter, the control unit 110 ends the process. Note that if the life reference value has been changed, the process may be continued from S108 onwards, described below, without ending the process, to measure the film thickness of the removed image carrier 11.

[0081] On the other hand, if the result of S105 indicates that the FD streak noise is not caused by wear (S106: NO), the control unit 110 does not change the life reference value, which remains at 2000 krots.

[0082] Thereafter, the control unit 110 determines whether or not to measure the film thickness of the removed image carrier 11 (referred to as a replacement) (S108). The determination as to whether or not to measure the film thickness is made based on an input from the user.

[0083] In S108, if the film thickness of the replacement product is to be measured (S108: YES), the film thickness measurement is carried out by the user (S109).

[0084] Next, the control unit 110 receives an input of a life reference value obtained from the film thickness measurement result. Then, the control unit 110 sets the received life reference value (S110). Thereafter, the control unit 110 ends the process.

[0085] In S108, if the film thickness measurement of the replacement product is not to be performed (S108: NO), the control unit 110 ends the process.

[0086] If the FD streak noise is not caused by wear, the process may be ended as is. As a procedure, the processes of S108 to S110 after it is determined that the FD streak noise is not caused by wear are omitted. As a result, if the FD streak noise is not caused by wear (S106: NO), the control unit 110 ends the process as is. In this case, the life reference value is not changed.

[0087] By the above processing, in this embodiment, when an image defect such as FD streak noise occurs on the image carrier 11 and the image carrier 11 is replaced, it can automatically determine whether the removed image carrier 11 has reached the end of its life or whether the image defect has occurred irregularly.

[0088] As a result, in this embodiment, if the usage conditions of the image carrier 11 after replacement are the same as before, it can be replaced just before the end of its life. Therefore, this embodiment can anticipate the occurrence of image noise caused by the end of its life. Therefore, this embodiment can also reduce waste of recording material and developer. Furthermore, this embodiment does not change the life reference value if the replacement is due to an irregular cause, even if it is before the end of its life. Therefore, this embodiment does not replace the image carrier 11 unnecessarily early.

[0089] In addition, in this embodiment, if the reason for replacing the image carrier 11 is irregular, the film thickness of the replacement part is measured. This makes it possible to grasp the degree of wear of the replacement part and change the life reference value based on the grasped film thickness.

[0090] In the above-described procedure, FD streak noise has been used as an example of an image defect, but image defects are not limited to FD streak noise. For example, the image carrier 11 may be replaced when a defect occurs that does not disappear even after repeated printing. In this embodiment, when the image carrier 11 is replaced for various reasons, it can be determined whether the removed image carrier 11 has reached the end of its life.

[0091] (action) The operation of the image forming apparatus 100 configured as above will be described.

[0092] (film thickness of image carrier) The film thickness of the image carrier 11 can be predicted by reading the charging current flowing through the image carrier 11. The method for predicting the film thickness of the image carrier 11 is to apply a charging bias to the image carrier 11. The potential of the charging bias is a predetermined value. When the charging bias is applied, a current value Iac flows through the image carrier 11. The film thickness is predicted from this current value Iac using a table value stored in advance. The degree to which the film thickness of the image carrier 11 has worn down can be obtained from the difference between the film thickness predicted initially (or immediately after use) and the film thickness predicted after use.

[0093] Fig. 7 is a graph showing the predicted film thickness of the image carrier 11 in the ideal case of the charging current and film thickness of the image carrier 11. Fig. 8 is a graph showing the predicted film thickness of the image carrier 11 in the case of variations in the charging current and film thickness of the image carrier 11.

[0094] As shown in FIG. 7, when a charging bias of 1700 V is applied and the current value Iac is 1800 μA, the ideal film thickness is predicted to be 24 μm.

[0095] However, the method of predicting the film thickness from the current value is subject to variations due to the influence of variations in the output of the high-voltage power supply of the image forming apparatus 100, the charging member, and the humidity control of the image carrier 11. Therefore, the results of film thickness prediction in the actual image forming apparatus 100 vary, as shown in FIG.

[0096] In the case of a normal image carrier 11, even if there is some variation in the predicted film thickness, there is no significant difference between the predicted state of wear and the actual state. A normal image carrier 11 does not have a high-hardness layer on its surface.

[0097] An image carrier 11 having a high-hardness layer (also referred to as a high-hardness image carrier) experiences less film abrasion than a normal image carrier 11. For this reason, in the case of a high-hardness image carrier 11, if there is variation in the predicted film thickness, the amount of wear due to film abrasion will be buried within the range of variation. For this reason, in the case of a high-hardness image carrier 11, its life cannot be accurately determined by film thickness prediction using the current value Iac.

[0098] Fig. 9 is a graph showing the film thickness prediction results for a high-hardness image carrier. As shown in Fig. 9, the lifespan of the high-hardness image carrier 11 is 2000 krot. However, when predicting the film thickness using the current value Iac, there is a possibility that the lifespan will be determined to be around 800 krot due to the influence of variations.

[0099] As described above, it is difficult to predict the life of the high-hardness image carrier 11. For this reason, the high-hardness image carrier 11 is replaced not based on predictions made using the current value Iac described above, but when it reaches a predetermined life reference value (number of rotations).

[0100] However, the high-hardness image carrier 11 does not necessarily reach the end of its life at the rotation speed set as the end of its life. Depending on the usage conditions, the image carrier 11 may generate image noise even earlier than its original end of life. For this reason, if the life reference value is changed every time the high-hardness image carrier 11 is replaced, the life reference value may be set to an unnecessarily short time even though the image carrier 11 is still usable.

[0101] (wear and tear of image carrier) The wear of the image carrier 11 will be described.

[0102] FIG. 10 is a graph for explaining the film scraping of the image carrier 11. In FIG.

[0103] Here, an example will be described in which the image carrier 11 has a high-hardness surface layer. In the image forming apparatus 100, toner and lubricant are supplied to the image carrier 11 from the developing unit 14. In such an image carrier 11, as long as a sufficient amount of the high-hardness surface layer remains, the image carrier 11 is highly durable and does not suffer from film abrasion (film thickness a in FIG. 10). However, with the image forming operation, film abrasion tends to be more accelerated on the front side of the image carrier 11 than on the back side (film thicknesses b to d in FIG. 10).

[0104] In the image forming apparatus 100, in many cases, a lubricant is supplied together with the developer from the developing unit 14. The developer containing the lubricant circulates from the rear side to the front side in the longitudinal direction of the developing unit 14. For this reason, less lubricant is supplied to the front side in the longitudinal direction of the developing unit 14, i.e., the front side of the image carrier 11. For this reason, as described above, film scraping tends to be accelerated at the front side of the image carrier 11 compared to the rear side.

[0105] When the high-hardness surface layer is worn away, the film is rapidly scraped away at the worn portion (film thickness e in FIG. 10). When this happens, image noise occurs in the formed image due to the wear over the life of the image carrier 11. Image noise is not just caused by wear. For example, if FD streak noise occurs at film thickness d in Figure 10, it is impossible to determine whether the cause of the FD streak noise is wear or irregularity. FD streak noise is streak-like image noise that occurs in the conveyance direction of the recording material.

[0106] Therefore, in this embodiment, the FD streak noise is judged based on information related to density. Fig. 11 is a graph for explaining the film thickness of the image carrier 11 that has reached the end of its life.

[0107] The film thickness of the image carrier 11 that has reached the end of its life varies depending on the position in the longitudinal direction of the image carrier 11. As the image carrier 11 is used for a longer period of time, the front side in the longitudinal direction of the image carrier wears out more than the rear side, as shown in Figure 11. When this wear reaches a predetermined amount, the image carrier 11 is deemed to have reached the end of its life and is replaced. When an image is printed with a certain exposure amount on such an image carrier 11, the image density difference ΔID1 is large between the front side and the rear side.

[0108] Figure 12 is a graph illustrating the film thickness of a new image carrier 11. As shown in Figure 12, a new image carrier 11 has a nearly uniform film thickness in the longitudinal direction of the image carrier 11. For this reason, when a new image carrier 11 is printed with a certain amount of exposure, the image density difference ΔID2 between the front and rear sides is almost the same. In other words, the image density difference ΔID2 is smaller than ΔID1.

[0109] This embodiment utilizes these characteristics and determines that noise is due to wear when the image density difference ΔID2 between the front and rear sides of the image carrier 11 is equal to or greater than a predetermined value. In this embodiment, when FD streak noise due to wear occurs, the life reference value for determining the life of the image carrier 11 is changed.

[0110] FIG. 13 is a graph for explaining the film thickness of the image carrier 11 in which irregular FD streak noise occurs.

[0111] When irregular FD streak noise occurs, there is a slight difference in the film thickness of the image carrier 11 between the front and rear sides of the image carrier 11, as shown in Figure 13. However, in this case, the film thickness is not as worn out as when the image carrier 11 has reached the end of its life. Also, even when an image is printed with a certain amount of exposure, the image density difference ΔID3 between the front and rear sides of the image carrier 11 does not change significantly. In other words, the image density difference ΔID3 is not as large as ΔID1, but is larger than ΔID2 (ΔID1 > ΔID3 > ΔID2).

[0112] Therefore, whether image noise is caused by wear due to lifespan can be determined using the image density difference ΔID1 (or a value obtained by adding a margin to ΔID1) as a predetermined value. That is, if the obtained image density difference (difference value) is equal to or greater than a predetermined value, the FD streak noise is determined to be caused by wear due to lifespan. On the other hand, if the obtained image density difference (difference value) is less than the predetermined value, the FD streak noise is determined to be an irregular occurrence. In the case of an irregular occurrence, the lifespan reference value of the image carrier 11 is not changed in this embodiment.

[0113] In this manner, in this embodiment, the cause of noise occurrence is determined using the difference in image density before and after the image carrier 11 is replaced.

[0114] (Changes in the film thickness of the image carrier) Figure 14 is a graph showing the change in film thickness from the front side to the rear side of the image carrier 11 in the first image forming apparatus. As shown in Figure 14, the image carrier 11 has a uniform film thickness from the front side to the rear side in the early stages of use. With use, this film thickness gradually becomes thinner at the rear side in the middle stages. With further use, the film thickness at the rear side becomes thinner first as the lifespan approaches.

[0115] From this transition in film thickness, the difference in film thickness due to film scraping on the image carrier 11 is greatest between the front and rear sides of the image carrier 11. For this reason, the image density difference is greatest when using the image densities at the front and rear ends of the image carrier 11. Therefore, it is preferable to obtain values ​​related to image density from one end and the other end in the longitudinal direction of the image carrier 11. This allows the present embodiment to determine the cause of image noise with high accuracy.

[0116] 15 is a graph showing the change in film thickness from the front side to the back side of the image carrier 11 in the second image forming apparatus. The second image forming apparatus has a smaller diameter primary transfer roller 16 than the first image forming apparatus. The purpose of making the diameter of the primary transfer roller 16 small is to make the image forming apparatus 100 smaller and less expensive.

[0117] In the second image forming apparatus, the primary transfer roller 16 has a small diameter and is therefore prone to bending (described in detail later). As a result, the primary transfer roller 16 makes strong contact with the image carrier 11 at both ends and weak contact (or no contact) at the center, sandwiching the intermediate transfer belt 30. Therefore, the load on the image carrier 11 is higher at both ends than at the center.

[0118] For this reason, as shown in Figure 15, film scraping is more accelerated at both ends of the image carrier 11 than at the center. Therefore, the image density difference is greatest when the image density at the center and one of the ends of the image carrier 11 is used. Therefore, when the primary transfer roller 16 has a small diameter, it is preferable to obtain values ​​related to image density from the center and one of the ends in the longitudinal direction of the image carrier 11. This allows the cause of image noise to be determined with high accuracy in this embodiment.

[0119] Here, we will explain deflection due to differences in diameter of primary transfer roller 16. Figure 16 is a front view illustrating the state of primary transfer roller 16 of the first image forming device. Figure 17 is a front view illustrating the state of primary transfer roller 16 of the second image forming device. Note that intermediate transfer belt 30 is omitted in Figures 16 and 17.

[0120] As already explained, the diameter of primary transfer roller 162 (FIG. 17) of the second image forming apparatus is smaller than that of primary transfer roller 161 (FIG. 16) of the first image forming apparatus. Therefore, primary transfer roller 162 (FIG. 17) of the second image forming apparatus is more likely to bend than primary transfer roller 161 (FIG. 16) of the first image forming apparatus. Whether primary transfer roller 16 bends or to what extent it bends depends on the rigidity of the material of primary transfer roller 16, the diameter, and other factors. For primary transfer roller 16 that is more likely to bend, therefore, it is preferable to provide density sensors at the center and at the ends. For primary transfer roller 16 that is less likely to bend, it is preferable to provide density sensors at both ends. Furthermore, if the state of bending is unknown, density sensors may be provided in a total of three locations (or more), including the center and both ends.

[0121] (Examples of image density and film abrasion on the image carrier) A specific example of the relationship between image density and film abrasion of the image carrier 11 will be described.

[0122] 18 is a graph showing the amount of toner adhered to the intermediate transfer belt 30 relative to the thickness of the image carrier 11. FIG.

[0123] The amount of toner adhesion on the intermediate transfer belt 30 is proportional to the image density. The amount of toner adhesion shown in Figure 18 was calculated from the value of the image density on the intermediate transfer belt 30 measured by the optical density sensor shown in Figure 4.

[0124] The image density was measured by forming a black solid image under the following conditions: exposure dose of 2.2 mJ / m 2 The potential Vdc of the image carrier 11 is 350 V, the linear velocity is 290 mm / s, and the environment is a temperature of 23° C. and a humidity of 65%.

[0125] As shown in Figure 18, when irregular FD streak noise occurs, the amount of toner adhesion is approximately 3.7 to 3.6 g / m 2 The film thickness of the image carrier 11 at this time is between about 26 and 28 μm. On the other hand, the amount of toner adhesion when FD streak noise occurs due to wear-out life is between about 4.7 and 3.7 g / m. 2 At this time, the film thickness of the image carrier 11 is between about 15 and 26 μm.

[0126] Therefore, the difference in toner adhesion amount when irregular FD streak noise occurs and the corresponding difference in film thickness of the image carrier 11 are smaller than the difference in toner adhesion amount when FD streak noise occurs due to wear and tear over the lifespan and the corresponding difference in film thickness.

[0127] This relationship closely matches the relationship between the film thickness difference at both ends of the image carrier 11 in the longitudinal direction in the transition of the film thickness of the image carrier 11 shown in Figure 19. In other words, when the difference in the amount of toner adhesion on the intermediate transfer belt 30 is small, the difference in film thickness at both ends of the image carrier 11 in the longitudinal direction is also small. Therefore, in such cases, it can be determined that the FD streak noise is caused by irregularities. When the difference in the amount of toner adhesion on the intermediate transfer belt 30 is large, the difference in film thickness at both ends of the image carrier 11 in the longitudinal direction is also large. Therefore, in such cases, it can be determined that the FD streak noise is caused by wear and tear due to lifespan.

[0128] When the image carrier 11 is replaced, the difference in film thickness at both ends of the image carrier 11 disappears. Therefore, the difference in the amount of toner adhesion at both ends also almost disappears. On the other hand, as already explained, when the image carrier 11 reaches the end of its life due to use, the difference in the amount of toner adhesion at both ends becomes large. Therefore, by calculating the difference in the difference in the amount of toner adhesion at both ends before and after replacing the image carrier 11, it can be determined whether the FD streak noise that has occurred is due to wear or an irregular cause.

[0129] In a similar manner to reading the image density on the intermediate transfer belt 30, the density of the image developed from the latent image on the image carrier 11 can be read with a density sensor (optical sensor) to determine the life of the image carrier 11.

[0130] As already explained, instead of measuring the image density, it is also possible to use the difference in the potential Vdc during image formation. Figure 20 is a graph showing the difference in the change in potential Vdc when an image with a constant exposure amount and image density is formed.

[0131] As shown in Figure 20, when FD streak noise occurs irregularly, the potential Vdc is between approximately 360 and 340 V. The film thickness of the image carrier 11 at this time is between approximately 26 and 28 μm. On the other hand, when FD streak noise occurs due to wear-out life, the potential Vdc is between approximately 450 and 360 V. The film thickness of the image carrier 11 at this time is between approximately 15 and 26 μm.

[0132] In this way, the difference in potential Vdc is smaller in the film thickness difference Vdc at the end of the irregular image carrier 11 than in the end of the wear life of the image carrier 11. This is similar to the relationship between image density and film thickness difference.

[0133] (Other methods for changing the lifespan reference value) The reference value of the life of the image carrier 11 can be changed as needed using usage information of the image carrier 11 .

[0134] FIG. 21 is a graph showing the usage environment of the image forming apparatus 100 and the transition of the average film thickness of the image carrier 11 at that time.

[0135] When the image forming apparatus 100 is used in a low-temperature, low-humidity environment, the hardness of the image carrier cleaning blade that scrapes off the image carrier 11 increases.

[0136] As shown in Figure 21, when the rotation speed increases, the film thickness of the image carrier 11 becomes thinner when the image forming apparatus 100 is used in a low temperature, low humidity environment (temperature 10°C, humidity 15%) than when it is used in a high temperature, high humidity environment (temperature 30°C, humidity 85%). Therefore, the film thickness is reduced more rapidly when the temperature is high and humidity than when the temperature is low and humidity.

[0137] For this reason, it is preferable to change the reference life value of the image carrier 11 based on the usage environment of the image forming apparatus 100, particularly the temperature and humidity. For example, if the image carrier 11 was used in a high temperature and high humidity environment before replacement and will be used in a low temperature and low humidity environment after replacement, it is preferable to set the reference life value after replacement shorter than the reference life value stored before replacement. Conversely, if the image carrier 11 was used in a low temperature and low humidity environment before replacement and will be used in a high temperature and high humidity environment after replacement, it is preferable to set the reference life value after replacement longer than the reference life value stored before replacement. Furthermore, if the image carrier 11 was used in a high temperature and high humidity environment before replacement and will be used in the same environment after replacement, it may be set longer than the reference life value specified in the product specifications after replacement. If the low temperature and low humidity conditions before replacement are the same after replacement, the reference life value after replacement may be shorter than the specifications.

[0138] FIG. 22 is a graph showing the toner concentration in the image forming apparatus 100 and the change in the average film thickness of the image carrier 11 at that time.

[0139] A stationary layer is formed at the contact point between the cleaning blade and the image carrier 11. The stationary layer is formed by supplying a developer consisting of toner and external additives. The higher the toner concentration, the more toner is supplied to the stationary layer. The developer circulates in the stationary layer. The cleaning blade then scrapes off the toner on the surface of the image carrier 11 using the stationary layer. Therefore, the higher the toner concentration, the more rapidly the image carrier 11 wears.

[0140] As shown in FIG. 22, when the rotation speed increases, the film thickness of the image carrier 11 becomes thinner when the toner concentration is high (toner concentration 7.5%) than when the toner concentration is low (toner concentration 5.5%). Therefore, the film thickness decreases more rapidly when the toner concentration is high than when the toner concentration is low. Note that the toner concentration is the ratio of the toner component to the total amount of developer, which is composed of toner and external additives.

[0141] For this reason, it is preferable to change the reference life value of the image carrier 11 according to the toner concentration setting. For example, if the image carrier 11 was used with a low toner concentration before replacement and with a high toner concentration after replacement, it is preferable to set the reference life value after replacement shorter than the reference life value stored before replacement. Conversely, if the image carrier 11 was used with a high toner concentration before replacement and with a low toner concentration after replacement, it is preferable to set the reference life value after replacement longer than the reference life value stored before replacement. Furthermore, if the image carrier 11 was used with a low toner concentration before replacement and with the same toner concentration after replacement, it may be set longer than the reference life value specified in the product specifications after replacement. If the image carrier 11 was used with a high toner concentration before replacement and with the same toner concentration after replacement, it may be set shorter than the reference life value after replacement.

[0142] 23 is a graph showing the print coverage of the image forming apparatus 100 and the corresponding change in the average film thickness of the image carrier 11. The higher the print coverage, the more toner remains on the surface of the image carrier 11. As a result, more toner is supplied to the stationary layer.

[0143] As shown in Figure 23, when the rotation speed increases, the film thickness of the image carrier 11 becomes thinner when the print coverage is high (15% coverage) than when it is low (1% coverage). Therefore, the film thickness decreases more rapidly when the print coverage is high than when it is low.

[0144] For this reason, it is preferable to change the reference life value of the image carrier 11 depending on the print coverage. For example, if the print coverage is low before replacement and high after replacement, it is preferable to set the reference life value after replacement shorter than the reference life value stored before replacement. Conversely, if the print coverage is high before replacement and low after replacement, it is preferable to set the reference life value after replacement longer than the reference life value stored before replacement. Furthermore, if the print coverage is low before replacement and the image carrier 11 is to be used with the same print coverage after replacement, the reference life value after replacement may be longer than the reference life value specified in the product specifications after replacement. If the print coverage is high before replacement and remains the same after replacement, the reference life value after replacement may be shorter than the specification.

[0145] FIG. 24 is a graph showing the ratio of monochrome mode to color mode of the image forming apparatus 100 and the transition of the average film thickness of the image carrier 11 at that time.

[0146] The image forming units 10Y, 10M, 10C, and 10K are arranged in this order, for example, from upstream in the running direction of the intermediate transfer belt 30. When the color mode ratio is high, toner is reverse-transferred from the upstream colors YMC to K, the most downstream color. For this reason, a large amount of toner is supplied to the image carrier 11 of K, the most downstream color. As a result, a large amount of toner is supplied to the stationary layer of the image carrier 11 of K.

[0147] As shown in Figure 24, the film thickness of the image carrier 11 is thinner when the color mode ratio is high (color mode ratio 50%) than when the color mode ratio is low (color mode ratio 5%). Therefore, the film thickness decreases more rapidly when the color mode ratio is high than when it is low. The color mode ratio (%) is calculated as follows: number of pages printed in color mode / (number of pages printed in color mode + number of pages printed in monochrome mode) x 100.

[0148] For this reason, it is preferable to change the reference life value of the image carrier 11 according to the ratio of color modes. For example, if the ratio of color modes was low before replacement and will be high after replacement, it is preferable to set the reference life value after replacement shorter than the reference life value stored before replacement. Conversely, if the ratio of color modes was high before replacement and will be low after replacement, it is preferable to set the reference life value after replacement longer than the reference life value stored before replacement. Furthermore, if the ratio of color modes was low before replacement and will be used with the same color mode ratio after replacement, the reference life value after replacement may be longer than the reference life value specified in the product specifications after replacement. If the ratio of color modes was high before replacement and remains the same after replacement, the reference life value after replacement may be shorter than the specification.

[0149] As described above, in this embodiment, by changing the life reference value in accordance with various environments in which the image carrier 11 is used, it is possible to set the life with higher accuracy.

[0150] The present invention is not limited to the above-described embodiments, but can be modified in various ways within the scope of the claims.

[0151] The means and methods for performing various processes in the image forming apparatus 100 according to the above-described embodiment can be realized by either a dedicated hardware circuit or a programmed computer. The program may be provided, for example, by a computer-readable recording medium such as a CD-ROM (Compact Disc Read Only Memory), or may be provided online via a network such as the Internet. In this case, the program recorded on the computer-readable recording medium is typically transferred to and stored in the storage unit 113 such as a hard disk. The program may also be provided as standalone application software, or may be incorporated into the software of the image forming apparatus 100 as a function of the apparatus. [Explanation of symbols]

[0152] 10 Image forming unit, 11 image carrier, 14 developing unit, 16 Primary transfer roller, 20 conveying section, 30 Intermediate transfer belt, 31 Transfer roller, 33 Transfer nip, 40 Fixing section, 60 Acquisition Department; 61 first concentration sensor, 62 second concentration sensor, 63 third concentration sensor, 100 Image forming device, 110 control section, 111 calculation unit, 112 Changes Section, 113 Memory section, 120 Image formation control unit, 601 light-emitting part, 602 Light receiving section.

Claims

1. an acquisition unit that acquires values ​​relating to image density at positions corresponding to at least two positions in the longitudinal direction of the image carrier; a calculation unit that calculates a difference between the values ​​relating to the image density at the at least two locations obtained from the image carrier before replacement as a first density difference, and calculates a difference between the values ​​relating to the image density at the at least two locations obtained from the image carrier after replacement as a second density difference; a change unit that changes a preset life reference value of the image carrier when a difference value between the first density difference and the second density difference is equal to or greater than a predetermined value; An image forming apparatus comprising:

2. The image forming apparatus according to claim 1 , wherein the acquisition unit acquires the value relating to the image density from one end and the other end in the longitudinal direction of the image carrier.

3. The image forming apparatus according to claim 1 , wherein the acquisition unit acquires the value relating to the image density from at least one end and a center portion in the longitudinal direction of the image carrier.

4. The acquisition unit The image forming apparatus according to any one of claims 1 to 3, wherein the density sensor is at least one of a density sensor that measures the image density on the image carrier, a density sensor that measures the image density on an intermediate transfer belt onto which the image on the image carrier is transferred, and a density sensor that measures the image density on a recording material onto which the image is transferred from the intermediate transfer belt.

5. The acquisition unit 4. The image forming apparatus according to claim 1, wherein a voltage to be applied to said image carrier when developing the latent image on said image carrier is stored.

6. The change unit 6. The image forming apparatus according to claim 1, wherein the life reference value of the image carrier is changed based on usage information of the image carrier.

7. 7. The image forming apparatus according to claim 6, wherein the usage information includes at least one of a usage environment of the image forming apparatus, a toner density, a print coverage, and a ratio of monochrome mode to color mode.

8. a step (a) of acquiring values ​​relating to image density at positions corresponding to at least two positions in the longitudinal direction of the image carrier before replacement; a step (b) of acquiring values ​​relating to image density at positions corresponding to at least two positions in the longitudinal direction of the image carrier after replacement; a step (c) of calculating a difference between the values ​​relating to the image density at the at least two locations obtained from the image carrier before replacement as a first density difference, and a difference between the values ​​relating to the image density at the at least two locations obtained from the image carrier after replacement as a second density difference; a step (d) of changing a preset reference life value of the image carrier when a difference value between the first density difference and the second density difference is equal to or greater than a predetermined value; A control method for an image forming apparatus comprising:

9. The steps (a) and (b) comprise:

9. The method for controlling an image forming apparatus according to claim 8, wherein the value relating to the image density is obtained from one end and the other end in the longitudinal direction of the image carrier.

10. The steps (a) and (b) comprise:

9. The method for controlling an image forming apparatus according to claim 8, wherein the value relating to the image density is obtained from at least one end portion and a center portion in the longitudinal direction of the image carrier.

11. The steps (a) and (b) comprise: a density sensor for measuring the density of the image on the image carrier; and a density sensor for measuring the density of the image on an intermediate transfer belt onto which the image on the image carrier is transferred. and a control method for an image forming apparatus according to any one of claims 8 to 10, wherein the image density is acquired by at least one density sensor among density sensors that measure the image density on the recording material onto which the image has been transferred from the intermediate transfer belt.

12. The steps (a) and (b) comprise:

12. The control method for an image forming apparatus according to claim 8, wherein a voltage applied to the image carrier when developing the latent image on the image carrier is obtained as a value related to the image density.

13. calculating a first density difference as a difference between values ​​relating to image density acquired from positions corresponding to at least two positions in the longitudinal direction of the image carrier before replacement, and a second density difference as a difference between values ​​relating to image density acquired from positions corresponding to at least two positions in the longitudinal direction of the image carrier after replacement; changing a preset reference life value of the image carrier when a difference value between the first density difference and the second density difference is equal to or greater than a predetermined value; A control program for an image forming apparatus comprising:

14. The value relating to the image density is The control program for an image forming apparatus according to claim 13 , wherein the values ​​are acquired from one end and the other end of the image carrier in the longitudinal direction.

15. The value relating to the image density is The control program for an image forming apparatus according to claim 13 , wherein the value is obtained from at least one end portion and a center portion in the longitudinal direction of the image carrier.

Images