JP5825842B2 - Image forming apparatus - Google Patents

Description

  The present invention provides a permanent image on a recording material by transferring a developer image (toner image) formed on an image carrier, for example, by an electrophotographic method onto the recording material, and then fixing the recording material. And the like.

  In a conventionally known color image forming apparatus, a toner image formed on a photosensitive drum which is an image carrier is temporarily transferred to an intermediate transfer member (hereinafter referred to as “primary transfer”), and then intermediate. Some transfer image toner images are transferred again to a recording material (hereinafter referred to as “secondary transfer”).

  In such an apparatus, in order to cope with endurance fluctuation and environmental fluctuation of the resistance value of the primary transfer means and the intermediate transfer body, as the transfer voltage control, an ATVC control method (abbreviation of Active Transfer Voltage Control, hereinafter referred to as “ATVC”). Adopted). The ATVC performs constant current control of the primary transfer portion with a preset value for the non-image portion on the photosensitive drum, detects a change in resistance of the primary transfer means based on a change in the generated voltage value at this time, and forms an image. In some cases, this is a control method in which constant voltage control is performed based on the result of calculating the generated voltage value.

  The ATVC is performed immediately before the start of image formation in order to cope with endurance fluctuations and environmental fluctuations of the resistance values of the primary transfer unit and the intermediate transfer member during print output. Further, in recent color image forming apparatuses, a configuration in which the developing device is in contact with the photosensitive drum is employed in order to improve the durability of the developing device. The developing device abuts on the photosensitive drum immediately before the start of image formation and is separated immediately after the end of image formation (hereinafter referred to as “developing contact” or “development separation”. "). In such a color image forming apparatus, the ATVC is performed before the development contact without toner on the photosensitive drum for stabilization. The reason why the ATVC is performed before the development contact is to prevent the transfer current in the ATVC from being violated due to the influence of fog toner.

  At the time of transfer voltage control, a transfer bias is applied to the photosensitive drum at a primary transfer portion on a portion that is contact-charged by a charging roller. The contact charging method generally uses DC or a bias application method in which AC and DC are superimposed, and discharge is repeated when a voltage is applied. For this reason, the surface of the photosensitive drum, which is a member to be charged, due to this discharge is greatly deteriorated, and the deteriorated surface portion of the photosensitive drum is scraped off by friction with a contact portion such as a cleaning blade, whereby the photosensitive layer of the photosensitive member becomes gradually thinner. It will follow. In particular, since toner is not present on the photosensitive drum before the development contact, the friction between the photosensitive drum surface portion and the contact portion of the cleaning blade becomes larger, and the abrasion of the photosensitive drum surface portion is further promoted. Become.

  As the photosensitive layer of the photosensitive drum becomes thinner in this way, the electrostatic capacitance of the photosensitive drum increases, and accordingly, the initial detection voltage VO detected by the ATVC control decreases. For this reason, the transfer contrast (the absolute value of the difference between the surface potential of the photosensitive drum and the primary transfer bias) becomes small, and problems such as transfer defects occur.

  As a method for suppressing the friction between the surface of the photosensitive drum and the contact portion of the cleaning blade, there is a case where a discharged toner image that is not transferred to the recording material is formed on the photosensitive drum. Patent Document 1 discloses an image forming apparatus that forms a discharged toner image on a photosensitive drum during pre-rotation prior to the start of normal image formation to be transferred to a recording material. Here, the discharged toner image is supplied to the cleaning blade of the cleaning device to serve as a lubricant.

  Patent Document 2 discloses an image forming apparatus that forms a toner image discharged on a photosensitive drum at intervals of normal image formation transferred to a recording material. Here, when the continuous use time of the developing device reaches a predetermined value, a discharged toner image is formed on the photosensitive drum, and the developed toner is wiped away for a long time and replaced with new toner.

  Further, as a method of preventing transfer failure due to the durability of the photosensitive drum, there is a case where the target current at the time of transfer is varied according to the progress of the durability of the photosensitive drum. Patent Document 3 discloses an image forming apparatus that changes the control target value based on the usage time of a photosensitive drum and the amount of toner image. Here, the target transfer current value is gradually increased according to the durable number of photosensitive drums and the number of toner images formed by the developing device (the amount of toner images) to obtain an optimum transfer current value. Transfer efficiency.

JP 2000-172027 A JP 2002-244512 A JP 2006-133333 A

  However, in the system described in the above-mentioned patent document, a toner image that is not transferred to the recording material is formed. For this reason, even if the toner consumption is accelerated and the photosensitive layer thickness of the photosensitive drum is sufficiently secured, the developing device (the cartridge itself in the case of the cartridge system in which the developing device and the photosensitive member are integrated) has a lifetime due to the decrease in the toner amount. Will reach. Further, varying the target current during transfer according to the progress of the durability of the photosensitive drum can avoid a transfer failure due to scraping of the surface portion of the photosensitive drum, but the life of the photosensitive drum remains short.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of preventing transfer failure without impairing transfer performance while delaying the progress of scraping of the image carrier and extending its life. is there.

The above object is achieved by the image forming apparatus according to the present invention. In summary, the present invention includes an image bearing member for bearing a toner image, a transfer unit that transfers the toner image before the Kizo bearing member onto a transfer member, and a voltage applying means for applying a voltage to the transfer means a detection knowledge means you detect information about voltage generated to the current flowing through said voltage applying means applies a voltage to the transfer unit, a detection that by the prior danger known means when not subjected to the transfer in the image forming apparatus to have a, and control means for carrying out the transfer voltage control by the voltage applying means sets the transfer voltage to be applied to the transfer means for the transfer based go in to the test known results, An acquisition unit that acquires an accumulated usage amount from the initial use of the image carrier; and a storage unit that stores the accumulated usage amount acquired by the acquisition unit, wherein the control unit executes a print job. Pre-rotation when doing The frequency of the transfer voltage control to be performed can be changed, and the frequency is greater than the first value than the case where the accumulated usage amount stored in the storage means is the first value. The image forming apparatus is characterized in that the value of 2 is more common .
According to another aspect of the present invention, an image carrier that carries a toner image, a transfer unit that transfers a toner image from the image carrier to a transfer target, a voltage application unit that applies a voltage to the transfer unit, Based on a detection result obtained by detecting the current flowing when the voltage applying means applies a voltage to the transfer means and information on the generated voltage, and detecting by the detecting means when the transfer is not performed. Control means for performing transfer voltage control for setting a transfer voltage to be applied to the transfer means by the voltage application means for the transfer, in the image forming apparatus, the accumulated use from the initial use of the image carrier An acquisition unit that acquires the amount; and a storage unit that stores the accumulated usage amount acquired by the acquisition unit; It is possible to change the frequency of the transfer voltage control performed at the time of rotation, and the frequency is larger than the first value than the case where the accumulated usage amount stored in the storage unit is the first value. There is provided an image forming apparatus characterized in that there are more cases of the second value.

  According to the present invention, the timing for performing the transfer voltage control (ATVC) is changed according to the accumulated usage amount of the image carrier. This makes it possible to execute ATVC performed immediately before the start of image formation for each print job at a different timing, delay the progress of scraping of the image carrier, extend the life, and prevent transfer defects. It becomes.

1 is a schematic configuration diagram of an embodiment of an image forming apparatus according to the present invention. 1 is a schematic configuration diagram illustrating an image forming unit of an image forming apparatus. It is a figure explaining transfer voltage control (ATVC). FIG. 3 is a schematic diagram of a layer structure of an initial photosensitive drum. It is the schematic of the layer structure of the photosensitive drum after durability. It is a figure which shows the relationship between the transfer contrast which concerns on a prior art example, and a primary transfer current. FIG. 6 is a schematic diagram illustrating a toner charge amount distribution. It is a figure which shows the relationship between a primary transfer current and transfer efficiency. It is a figure which shows the change of ATVC of 1 day. It is a figure which shows the relationship between temperature / humidity and an absolute water content. It is a flowchart figure explaining the ATVC implementation timing which concerns on one Example of this invention. It is a figure showing the relationship between the number of paper passing and CT layer film thickness. It is a figure which shows the relationship between a primary transfer current and transfer efficiency. It is a sequence diagram when implementing ATVC by pre-rotation. It is a sequence diagram when ATVC is implemented by post-rotation.

  The image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.

Example 1
FIG. 1 shows an overall configuration of a color image forming apparatus which is an embodiment of an image forming apparatus according to the present invention.

  In this embodiment, the color image forming apparatus 1 includes a plurality of image forming means (image forming portions) arranged in a horizontal row. In this embodiment, four color magenta, cyan, yellow, and black are provided. An image forming unit 8 (8M, 8C, 8Y, 8K) is provided. Each image forming section has the same configuration and has a drum-shaped electrophotographic photosensitive member (hereinafter referred to as “photosensitive drum”) 9 (9M, 9C, 9Y, 9K) as an image carrier. Around the photosensitive drum 9, a charging device 10 (10M, 10C, 10Y, 10K) as a charging unit, an exposure device 11 (11M, 11C, 11Y, 11K) as an exposure unit, and a developing device 12 (developing unit) ( 12M, 12C, 12Y, 12K) are arranged. Further, around the photosensitive drum 9, a cleaning device 14 (14M, 14C, 14Y, 14K) as a cleaning unit is disposed.

  Below the image forming unit 8 (8M, 8C, 8Y, 8K), an intermediate transfer belt 30 is disposed as an intermediate transfer member that is stretched around a plurality of rollers 31, 32, and 33 and circulates in the direction of the arrow. Yes. Further, primary transfer rollers 13 (13M, 13C, 13Y, and 13K) as primary transfer means are disposed via intermediate transfer belts 30 at positions facing the respective photosensitive drums 8.

  In the present embodiment, the sheet feeding unit 2 in which the recording materials S are stacked and accommodated is disposed at the lower part of the image forming apparatus 1. The sheet feeding rollers 16 separate the recording materials S one by one. The paper is fed to the secondary transfer portion T2. In the secondary transfer portion T2, a secondary transfer roller 34 as a secondary transfer unit is disposed to face the secondary transfer counter roller 32.

  FIG. 2 shows a magenta image forming unit 8M in the color image forming apparatus of this embodiment. An image forming process by the image forming apparatus of the present invention in the magenta image forming unit 8M will be described.

  When an image formation start signal is input, rotation of the intermediate transfer belt 30 and the negative OPC photosensitive drum 9M is started. At this time, the intermediate transfer belt 30 is configured to contact the photosensitive drum 9M. Then, the surface of the photosensitive drum 9M is charged to a desired charging potential (VD) by applying a negative DC voltage to the charging roller 10M as a charging device (negative polarity in this embodiment). Next, image exposure (exposure potential VL) based on image information is performed by the exposure device 11M on the surface of the charged photosensitive drum 9M, and an electrostatic latent image is formed.

  Next, the electrostatic latent image formed on the photosensitive drum 9M is developed with magenta toner (negatively charged toner) by the developing device 12M, and a magenta toner image is formed on the photosensitive drum 9M. This magenta toner image is electrostatically transferred to the intermediate transfer belt 30 by the primary transfer roller 13M at the primary transfer portion T1M. At this time, a predetermined voltage (positive voltage in this embodiment) is applied to the primary transfer roller 13M from the transfer power source 51M controlled by the transfer bias control means 50M.

  Toner remaining on the surface of the photosensitive drum 9M without being transferred to the intermediate transfer belt 30 during the primary transfer (residual toner) is removed by the cleaning device 14M and collected in a waste toner container (not shown). The photosensitive drum 9M whose surface has been cleaned in this way is used for the next image formation starting from charging.

  In the present embodiment, the above-described photosensitive drum 9M, charging roller 10M, developing device 12M, and cleaning device 14M constituting the image forming unit 8M are integrally incorporated in a cartridge container 15M (illustrated by a dotted line in FIG. 2). As a whole, the cartridge is constituted. The cartridge 8M is configured to be detachable from the image forming apparatus main body. For example, when the photosensitive drum 9M reaches the end of its life, the entire cartridge 8M is taken out from the image forming apparatus main body and replaced with a new one. It has become.

  As shown in FIG. 1, the image forming process to the transferring process are similarly repeated in the other image forming units (that is, cartridges) 8C, 8Y, and 8K. Cyan toner images, yellow toner images, and black toner images formed on the photosensitive drums 9C to 9K in the other image forming units 8C to 8K are sequentially superimposed on the intermediate transfer belt 30 in the primary transfer units T1C to T1K. Primary transfer is performed. In FIG. 1, members corresponding to the transfer bias control means 50M and the transfer power source 51M in FIG. 2 are omitted.

  Thereafter, the toner images of a plurality of colors on the intermediate transfer belt 30 are secondarily transferred collectively to the recording material S fed at a predetermined timing by the secondary transfer roller 34 at the secondary transfer portion T2. At this time, a predetermined voltage (positive voltage in this embodiment) is applied to the secondary transfer roller 34 from the power source 35 as shown in FIG. Is secondarily transferred, and the toner 22 remains as a transfer residual toner on the intermediate transfer belt 30. The transfer residual toner 22 is removed from the intermediate transfer belt 30 by the intermediate transfer body cleaning device 17.

  The recording material S to which the toner image has been transferred is conveyed to the fixing device 15, and the fixing device 15 heats and presses the toner image onto the recording material S to be fixed. This image forming step is completed.

  Here, when the above-described primary transfer of the toner images, that is, when the toner images on the photosensitive drums 9M to 9K are transferred onto the intermediate transfer belt 30, transfer voltage control is executed. In this embodiment, constant voltage control by ATVC was performed. ATVC will be described with reference to FIG.

  Taking magenta toner as an example, the photosensitive drum 9M is charged by the charging roller 10M at the charging potential at the time of image formation. The transfer bias control means 50M controls the transfer power supply (voltage application means) 51M to apply three kinds of voltages of predetermined transfer voltages (Vft1, Vft2, Vft3). Then, current values (Ift1, Ift2, Ift3) corresponding to the output voltage are detected by the current detection means 52M. A target transfer voltage Vfttarget corresponding to the target transfer current Iftarget is calculated and set as a transfer voltage. This transfer voltage control is performed independently for each color, and the transfer voltage control execution timing is performed immediately before image formation in order to cope with endurance fluctuations and environmental fluctuations of the resistance values of the primary transfer roller and the intermediate transfer belt.

  Next, the photosensitive drum 9 (9M to 9K) used in this embodiment will be described.

  FIG. 4 shows the layer structure of the photosensitive drum 9. The photosensitive drum 9 is an organic photoconductor, and in order from the inner side (lower side in the figure), a base aluminum layer 91, a CP layer (undercoat layer) 92, a UC layer (positive charge injection preventing layer) 93, and a CG layer. A (charge generation layer) 94 and a CT layer (charge transport layer) 95 are included. In the layer configuration shown in the figure, a photosensitive layer is formed by the UC layer 93, the CG layer 94, and the CT layer 95. Therefore, the film thickness of the photosensitive layer is the sum of the film thickness of the UC layer 93 and the CG layer 94 and the film thickness of the CT layer 95. Although there is a coating layer on the CT layer 95, in order to suppress an increase in cost, it is not often used in a low-cost machine with a small total number of printed sheets. Here, the CT layer 95 has an initial film thickness of 20 μm. The CG layer 94 and the UC layer 93 are almost negligible with a thickness of 1 μm or less. The CT layer 95 is shaved together with durability by charging and cleaning, and after repeating the setting of passing two A4 size sheets and stopping (hereinafter referred to as “two-sheet intermittent sheet feeding”) As shown in FIG. 5, the thickness is reduced to about 10 μm.

  Next, a description will be given of a case where transfer defects occur when the CT layer 95 is cut.

  FIG. 6 shows the relationship between the transfer contrast (the absolute value of the difference between the surface potential of the photosensitive drum and the primary transfer bias) and the primary transfer current in two states of the photosensitive drum 9. As described above, the photosensitive drum 9 indicated by a solid line uses a negative-polarity OPC photosensitive member, and its layer configuration is in an initial use state, and the thickness of the CT layer 95 is 20 μm (hereinafter, “ Called "Initial Drum"). On the other hand, the photosensitive drum 9 indicated by a dotted line is in a state after enduring 20000 sheets (20K sheets) of two A4 size sheets by intermittent paper passing, and the film thickness of the CT layer 95 is 10 μm (hereinafter, “ Called "durable drum".)

  The initial drum has a small capacitance because the CT layer 95 is thick (20 μm). For this reason, the primary transfer current hardly flows. On the other hand, the durable drum has a large capacitance because the CT layer 95 has a thin film thickness (10 μm). For this reason, even if it is the same transfer contrast as the initial stage of use, more primary transfer current flows. For this reason, when the initial target current is 5 μA, the transfer contrast is about 800 V for the initial drum, but is about 730 V for the durable drum.

  Further, the developer also deteriorates due to durability. FIG. 7 shows the toner charge amount distribution. The solid line in the figure represents the tribo distribution of toner at the initial use (hereinafter referred to as “initial agent”), and the broken line represents the toner after the endurance of 20000 sheets of two A4 size papers intermittently (hereinafter “ The tribo distribution of “durable agent” is shown. As shown in the figure, the tribo distribution of the durability agent is broader than the tribo distribution of the initial agent. Along with this, the transfer efficiency further deteriorates. Therefore, the worst case where transfer efficiency deteriorates is a combination of a durable drum and a durable agent. Here, the toner charge amount distribution is measured by using an ESPART analyzer (trade name) manufactured by Hosokawa Micron Co., Ltd., and blowing off the toner related to the measurement with nitrogen gas and introducing it into the measuring unit (measuring cell) of the measuring device through the sampling hole. It was done by doing. Further, the toner was used until 3000 toners were counted.

  FIG. 8 shows the relationship between the transfer current (primary transfer current) and the transfer efficiency for the toner in the primary transfer. A solid line indicates an initial agent, and a broken line indicates a durable agent. As shown by the solid line, in the combination of the initial drum and the initial agent, the transfer efficiency hardly increases at 5 μA (corresponding to the solid line ↓ portion in FIG. 8). Further, as shown by the broken line, in the combination of the durable drum and the durable agent, the transfer efficiency hardly increases at 12 μA (corresponding to the broken line ↓ portion in FIG. 8). In the case of a durable agent, the transfer efficiency is 90% when the transfer current is 12 μA, whereas it is as low as 80% when the transfer current of the initial agent is 5 μA.

  Here, it is conceivable to set the transfer current to 12 μA from the beginning of use, but in this case, the transfer contrast becomes too high, and there is a possibility that drum memory is generated. In this embodiment, as shown in FIG. 6, when the transfer contrast is 900 V or more, the photosensitive drum 9 passes through the intermediate transfer belt 30 between the portion where the toner image is present and the portion where the toner image is absent, and directly from the transfer roller 13 to the photosensitive drum. There is a difference in the amount of transfer current flowing through the. Therefore, the surface potential of the photosensitive drum 9 cannot be made uniform by the next charging, and a black dot is generated on the image, or a drum memory is generated in which the history of the previously printed image has a density difference. When the target transfer current is set to 12 μA in the initial drum, the transfer contrast becomes 930 V, which becomes a drum memory generation region.

  Next, the relationship between the ATVC execution timing and the amount of abrasion of the CT layer 95 will be described.

  The CT layer 95 is scraped together with durability by charging and cleaning, and the amount of scraping becomes more prominent as the rotation time becomes long, especially when no toner is present on the photosensitive drum before contact with development. That is, the greater the number of ATVC implementations, the greater the amount of wear of the CT layer 95, and the timing at which ATVC is carried out for each conventional pre-rotation is set to increase the amount of wear of the CT layer 95. In this embodiment, the ATVC is not performed every time the print job is rotated in the past, but is controlled based on the accumulated usage amount of the photosensitive drum, and in this embodiment, the number of sheets to be passed. The control will be described below.

  In the image forming apparatus of this embodiment, the definition of the number of prints is divided by the length in the sheet passing direction as shown in Table 1 and counted.

  Detailed definitions are described below.

If the length of the paper passing direction is L,
(1) When L is not less than the postcard (vertical) size and not greater than the A5 size (148 [mm] ≦ L ≦ 210 [mm]), the count is 0.5 for one sheet.
(2) When L is larger than the A5 size length and less than or equal to the A4 size length (216 [mm] <L ≦ 300 [mm]), the count is 1.0 for one sheet.
(3) When L is larger than the A4 size length and less than the LEGAL size (300 [mm] <L ≦ 356 [mm]), the count is 1.5 for one sheet.

  However, when double-sided printing is performed on the same paper, the print count is doubled.

Table 2 below shows the correspondence between typical paper sizes and areas and the number of times of printing (print count) defined in this embodiment.

Next, an interval for performing ATVC will be described. FIG. 9 shows an example in which ATVC is performed every hour on a certain day (24 hours) and the result (transfer voltage) is monitored. The transfer voltage is stable during the day, and is lowered by about 5 V at midnight and early morning, and the transfer voltage does not change greatly in one day (24 hours). Here, the reason for changing in the middle of the night or early in the morning seems to be due to a change in use environment or a long-term stoppage. Accordingly, it is possible to reduce the frequency of ATVC except when the use environment has changed significantly or when it has not been used for a long time. In this embodiment, the temperature and humidity sensor is mounted, the absolute water content from the absolute moisture amount conversion table of FIG. 10, and when the increase or decrease 5 g / m ² or more, if the printing operation more than an hour had been left rather Forcibly, ATVC is implemented.

  Next, interval counting for performing ATVC for print count will be described with reference to the flowchart of FIG. The interval at which ATVC is performed is shortened in proportion to the amount of abrasion of the photosensitive drum, and ATVC is performed at the interval shown in Table 3 by the pre-rotation of the print job.

  When printing is started from the print standby state (S1) (S2), first, a change in absolute water content from the previous print and a standing time are determined (S3).

If the increase or decrease in the absolute water content is 5 g / m ² or more, or the standing time is 1 hour or more (Yes in S3), ATVC is forcibly executed (S4) and image formation is performed (S10).

If the increase / decrease in the absolute water content is less than 5 g / m ² or the standing time is less than 1 hour (No in S3), the print count is referred to and the following is performed.
(1) ATVC is not performed until 3000 counts, image formation is performed (S5, S10),
(2) From 3001 to 5000 counts, image formation is performed after ATVC is performed every 1000 counts (S6, S6-1, S10),
(3) From 5001 to 10000 counts, image formation is performed after ATVC is performed every 500 counts (S7, S7-1, S10),
(4) From 10001 to 15000 counts, ATVC is performed every 300 counts before image formation is performed (S8, S8-1, S10),
(5) From 15001 to 20000 counts, image formation is performed after ATVC is performed every 100 counts (S9, S9-1, S10),
(6) After 20001 count or more, image formation is performed after ATVC is performed every 50 counts (S9, S9-2, S10),
(7) Finally, the print count is accumulated (S11), and the process returns to the print standby (S1).

  In this embodiment, referring to FIG. 1, the print count as the photosensitive drum integrated usage is acquired (that is, counted) by the print count integration circuit 42 as the integrated usage acquisition means. When the print count is input to the print count integration circuit 42, the CPU (control means) 41 executes ATVC by pre-rotating the print job when each image forming station reaches a predetermined count. Since a predetermined range is provided for the predetermined count, if one color is subjected to ATVC, if another color is also within this range, ATVC is performed at the same time. By doing in this way, ATVC can be implemented efficiently. Further, the CPU 41 has a memory (storage means) 40, in this embodiment a nonvolatile memory, stores a print count, and the remaining processing is continued even after the power is turned OFF / ON.

  Here, when the cutting method of the CT layer 95 is compared between the conventional execution timing and the execution timing of the present embodiment, when 20,000 sheets of A4 size paper are intermittently passed, as shown in FIG. Is performed at the conventional timing (broken line in the graph), the CT layer 95 is cut to about 10 μm, and when ATVC is performed at the timing of this embodiment (solid line in the graph), the CT layer 95 is cut to about 15 μm. It was.

  FIG. 13 shows the relationship between the transfer efficiency (primary transfer current) and transfer efficiency of the initial drum and the drum when the CT layer 95 is scraped to about 15 μm. The solid line shows the combination of the initial drum and the initial agent, and the broken line shows the result of the combination of the durable drum and the durable agent. In both the combination of the initial drum and the initial agent and the combination of the durable drum and the durable agent, the transfer efficiency hardly changes after 8 μA (corresponding to the solid line ↓ portion in FIG. 13), and the transfer efficiency is 90%. Further, the transfer contrast shown in FIG. 6 is 850 V, which is an area where no drum memory is generated. Therefore, by setting the transfer current to 8 μA from the initial use, good transfer efficiency from the initial stage to after the endurance and the drum memory, etc. A good image free from image defects can be obtained.

  By adopting such a configuration, the transfer voltage control (ATVC) executed in the pre-rotation for each print job is changed according to the number of prints to delay the progress of the photosensitive drum scraping, Transfer defects can be prevented. Furthermore, by combining conventional techniques (Patent Document 3 etc.) such as changing the target value of ATVC based on the usage time of the photosensitive drum and the toner consumption with the present invention, the life of the photosensitive drum is further increased. That is, it goes without saying that the life of the cartridge itself can be extended.

Example 2
A second embodiment of the present invention will be described. In the present embodiment, the ATVC is performed in other than the pre-rotation according to the accumulated usage amount stored in the storage means, and the rest is the same as the first embodiment. Therefore, the description of the overall configuration of the image forming apparatus is omitted, and the description of the first embodiment is cited.

  In this embodiment, the ATVC is not performed at the time of the pre-rotation of the print job of the first embodiment, that is, at a time other than immediately before starting the image formation. In this embodiment, the post-rotation of the print job is performed after the development separation. We decided to implement ATVC. The definition of the number of prints and the interval at which ATVC is performed are the same as in the first embodiment.

  By adopting such a configuration, similarly to the first embodiment, it is possible to prevent the transfer failure while delaying the progress of the photosensitive drum scraping and extending the life.

  Further, in this embodiment, the time until the first sheet is printed out after receiving a print command from the standby state, First Print Out Time (hereinafter referred to as FPOT) can be shortened.

  Hereinafter, FPOT shortening will be described with reference to FIGS. 14 and 15.

  FIG. 14 shows a main sequence when one print is output when ATVC is performed in the pre-rotation.

  When printing is started, pre-rotation starts, ATVC is performed during the pre-rotation, and development contact is performed after ATVC is completed. The reason why ATVC is performed before the development contact is that it is not affected by the toner. Next, after completion of the development contact, image formation is started, and post-rotation is performed after the image formation is completed. Development separation is performed during post-rotation. The print is discharged from the apparatus after a predetermined time from the image formation, and the time from the start of printing to the discharge is defined as FPOT.

  Here, FIG. 15 shows a main sequence when one print is output when the ATVC of the present embodiment is implemented by post-rotation.

  In this embodiment, since ATVC is not performed in the pre-rotation, the development contact can be performed immediately after the start of the pre-rotation, and the image formation start timing is advanced. Accordingly, the timing at which the print is discharged from the apparatus after a predetermined time from the image formation is also accelerated, and the FPOT is shortened.

  As described above, in this embodiment, the timing for executing ATVC executed immediately before image formation for each print job in accordance with the number of prints is changed during post-rotation. With this configuration, it is possible to prevent the transfer failure and further shorten the FPOT while extending the life by delaying the progress of the photosensitive drum scraping.

1 Image forming apparatus 8 (8M to 8K) Image forming means (image forming unit, cartridge)
9 (9M-9K) Photosensitive drum (image carrier)
10 (10M-10K) Charging roller (charging means)
11 (11M to 11K) Exposure apparatus (exposure means)
12 (12M-12K) Developing device (developing means)
30 Intermediate transfer belt (intermediate transfer member)
34 Secondary transfer roller (secondary transfer means)
40 memory (storage means)
41 CPU (control means)
42 Print count integration circuit (integrated usage acquisition means)
50 Transfer bias control means 51 Transfer power supply (voltage application means)
52 Current detection means

Claims (8)

An image carrier for carrying a toner image;
A transfer unit for transferring the toner image from the front Kizo bearing member onto a transfer member,
A voltage applying means for applying a voltage to said transfer means,
A detection knowledge means you detect information about voltage by the voltage applying means generates current that flows by applying a voltage to said transfer means,
Transfer to set the transfer voltage to be applied to the voltage application means the transfer means for the transfer based on the detection knowledge results performed detection that by the prior danger known means when not subjected to the transfer Control means for performing voltage control ;
In the image forming apparatus to have a,
An acquisition means for acquiring an accumulated usage amount from the initial use of the image carrier;
Storage means for storing the accumulated usage acquired by the acquisition means;
Have
The control means can change a frequency of the transfer voltage control performed at the time of pre-rotation when executing a print job, and the frequency is determined by the integrated usage amount stored in the storage means being a first value. In the image forming apparatus, the second value larger than the first value is more often than the first value .   2. The control unit according to claim 1, wherein when the accumulated usage amount stored in the storage unit is equal to or less than a predetermined threshold value, the transfer voltage control is not performed at the time of pre-rotation when executing a print job. The image forming apparatus according to 1.   An image carrier for carrying a toner image;
  Transfer means for transferring a toner image from the image carrier to a transfer medium;
  Voltage application means for applying a voltage to the transfer means;
  Detecting means for detecting information relating to a current flowing and a voltage generated when the voltage applying means applies a voltage to the transfer means;
  Control means for performing transfer voltage control for setting the transfer voltage applied to the transfer means by the voltage application means for the transfer based on the detection result by performing detection by the detection means when the transfer is not performed. When,
In an image forming apparatus having
  An acquisition means for acquiring an accumulated usage amount from the initial use of the image carrier;
  Storage means for storing the accumulated usage acquired by the acquisition means;
Have
  The control means can change the frequency of the transfer voltage control performed at the time of post-rotation when a print job is executed, and the frequency is calculated based on the first usage value stored in the storage means. In the image forming apparatus, the second value larger than the first value is more often than the first value.   The control means does not perform the transfer voltage control at the time of post-rotation when a print job is executed when the accumulated usage amount stored in the storage means is equal to or less than a predetermined threshold value. The image forming apparatus according to 3.   When executing the print job, the control unit determines whether the change amount of the index value of the environment of the image forming apparatus from the previous print job is equal to or greater than a predetermined change amount, or the print job is executed from the previous print job. When the time that the image forming apparatus is left unexecuted is a predetermined time or more, the transfer is performed at the time of pre-rotation when executing a print job regardless of the accumulated use amount stored in the storage unit. The image forming apparatus according to claim 1, wherein voltage control is performed. The integrated amount stored by the storage unit, in any one of claims 1 to 5, characterized in that said image forming apparatus is a count value that is added in accordance with the number of the output image The image forming apparatus described.   A cleaning unit disposed in contact with the image carrier for removing toner remaining on the image carrier after the transfer from the image carrier; and an image carrier in contact with the image carrier. A developing device that supplies toner and is detachable from the image carrier, and the transfer voltage control is performed in a state where the developing device is separated from the image carrier. The image forming apparatus according to claim 1.   In the transfer voltage control, the control unit obtains a relationship between the current and the voltage by changing an output voltage of the voltage application unit and causing the detection unit to detect a current corresponding to each output voltage. The image forming apparatus according to claim 1, wherein the voltage application unit sets a transfer voltage to be applied to the transfer unit for the transfer based on the image.

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