JP6108807B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer which obtains an image on a transfer material by transferring a toner image formed on an image carrier by an electrophotographic method onto a transfer material and then fixing it.

  Conventionally, the toner image on the surface of the photosensitive drum is temporarily transferred to the surface of the intermediate transfer member (hereinafter referred to as primary transfer), and then the toner image on the surface of the intermediate transfer member is transferred again to the transfer material (hereinafter referred to as secondary transfer). There is known a color image forming apparatus having a configuration referred to as In such an image forming apparatus, in order to cope with endurance fluctuations and environmental fluctuations of the resistance values of the primary transfer unit and the intermediate transfer member, the primary transfer unit is set in advance to the non-image area on the photosensitive drum. The transfer control is performed with constant current control. Then, the resistance fluctuation of the primary transfer portion is detected from the fluctuation of the generated voltage value at the time of constant current control, and at the time of image formation, the constant voltage control is performed based on the result of calculating the previous generated voltage value. The voltage control timing for detecting the resistance fluctuation of the primary transfer portion may be immediately before image formation in order to cope with the durability fluctuation and environmental fluctuation of the resistance value of the primary transfer portion or the intermediate transfer member. In Patent Document 1, the predicted transfer voltage is compared with the transfer voltage based on the temperature and humidity environment information and the resistance change information of the transfer roller. A technique for selecting an optimum transfer voltage based on a comparison result with a temperature and humidity environment is disclosed.

JP 2003-66743 A

  In recent color image forming apparatuses, it is required to shorten a time (First Print Out Time, hereinafter referred to as “FPOT”) until an image-formed first transfer material is output. For this reason, an image forming apparatus is proposed in which voltage control is performed to detect resistance fluctuations in the primary transfer portion during initial rotation of the photosensitive drum, and the above voltage control is omitted immediately before image formation. However, when the voltage control for detecting the resistance fluctuation of the primary transfer portion is omitted, there are the following problems.

  For example, when the environment changes or when a predetermined number of images are formed, the target current value changes, so that it is necessary to perform voltage control to detect the resistance variation of the primary transfer portion again. It is not always possible to omit the voltage control for detecting the resistance fluctuation of the primary transfer portion. The timing of the voltage control for detecting the resistance change of the primary transfer portion again is immediately before or after the image formation, and the voltage control for detecting the resistance change of the primary transfer portion is executed again, so that the FPOT becomes long. Since the photosensitive drum rotates excessively, there is a problem that the life of the photosensitive drum is reduced.

  The present invention has been made under such circumstances, shortening the FPOT, reducing the frequency of performing voltage control for detecting the resistance fluctuation of the primary transfer portion while maintaining the image quality, and reducing the frequency of the photosensitive drum. The purpose is to extend the life.

  The present invention has the following configuration in order to solve the above problems.

(1) and the photosensitive member, the developing means for forming a toner image by applying a developer to a latent image formed on the photosensitive member, a transfer unit that transfers the toner image formed on the photosensitive member, wherein a voltage applying means for applying a voltage to the transfer means, and current detecting means for detecting a current flowing through the transfer means, and control means for controlling the voltage that will be applied to the transfer means by said voltage applying means, wherein, at a timing other than the image forming, before SL voltage control for determining the first voltage based on the current detected by said current detecting means in a state of being applied a voltage to said transfer means by the voltage applying means was carried out, at the time of image formation, the image forming apparatus for controlling the voltage applying means to apply a first voltage determined in the voltage control to the transfer means, the control means, the photosensitive member It is possible to predict the thickness, together with the voltage control was performed at least once to determine the first voltage before starting the image formation, the first voltage and the first voltage the thickness of said photosensitive member to different prediction from the thickness of the photosensitive member when the determined, the second voltage determined based on, then when an image is formed, the image formation is started The voltage application unit is controlled to apply the first voltage or the second voltage corresponding to the film thickness of the photoconductor to the transfer unit without performing the voltage control before. An image forming apparatus.

  According to the present invention, it is possible to shorten the FPOT and reduce the frequency of performing voltage control for detecting the resistance fluctuation of the primary transfer portion while maintaining the image quality, thereby extending the life of the photosensitive drum.

1 is a diagram illustrating a schematic configuration of an image forming unit and an image forming apparatus according to a first embodiment. 1 is a diagram illustrating a system configuration of an image forming apparatus according to a first embodiment. The figure for demonstrating the voltage control of Example 1. FIG. Schematic of the layer structure of the initial photosensitive drum and the photosensitive drum after durability in Example 1 The figure which shows the relationship between the transfer contrast and primary transfer current of Example 1. The figure which shows the sequence of the printing operation | movement of Example 1, and a primary transfer operation | movement. The figure which shows the memory | storage state of the primary transfer voltage setting value of Example 1. FIG. Flowchart for explaining processing for storing a primary transfer voltage setting value according to the first embodiment. The figure which shows the memory | storage state of the primary transfer voltage setting value of Example 2. FIG. 7 is a flowchart for explaining processing for storing a primary transfer voltage setting value according to the second embodiment. Flowchart for explaining processing for storing a primary transfer voltage setting value according to the third embodiment.

  The form for implementing this invention is demonstrated below.

[Image Forming Process and Configuration of Image Forming Apparatus]
A magenta (M) image forming process of the image forming apparatus according to the first exemplary embodiment will be described with reference to FIG. When an image formation start signal is input to the image forming apparatus, rotation of the intermediate transfer belt 30 and the photosensitive drum 9M (image carrier) is started. At this time, the intermediate transfer belt 30 (intermediate transfer member) is in contact with the photosensitive drum 9M. Then, a negative DC voltage of the charging roller 10M is applied to the surface of the photosensitive drum 9M to charge it to a desired charging potential (negative polarity in this embodiment), and the exposure device 11M is applied to the surface of the charged photosensitive drum 9M. Thus, image exposure based on the image information is performed, and an electrostatic latent image is formed.

  Next, the electrostatic latent image formed on the photosensitive drum 9M is developed by applying a magenta toner (toner having a negative charge characteristic) as a developer by the developing device 12M, and a magenta toner image is formed on the photosensitive drum 9M. Is done. This magenta toner image is electrostatically transferred to the intermediate transfer belt 30 by the primary transfer roller 13M. At this time, a predetermined voltage (positive voltage in this embodiment) of the transfer power supply 45M (voltage applying means) controlled by the transfer voltage control unit 44M is applied to the primary transfer roller 13M. 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.

  In this embodiment, the photosensitive drum 9M, the charging roller 10M, the developing device 12M, and the cleaning device 14M are integrally incorporated in a cartridge container 15M (shown by a dotted line in FIG. 1A). This constitutes the cartridge 8M. The cartridge (image forming station) 8M is detachable from the image forming apparatus main body. For example, when the photosensitive drum 9M reaches the end of its life, the whole is taken out from the image forming apparatus main body and replaced with a new cartridge.

  Such image formation to transfer process is similarly repeated for the other cartridges 8C, 8Y, and 8K as shown in FIG. 1B, and cyan, yellow, and black toner images formed on the photosensitive drums 9C to 9K. Are sequentially superposed on the intermediate transfer belt 30 for primary transfer. C, Y, and K indicate cyan, yellow, and black, respectively. The configuration of the cartridges 8C, 8Y, and 8K is the same as that of the above-described cartridge 8M, and thus description thereof is omitted. Thereafter, the toner images of a plurality of colors formed on the intermediate transfer belt 30 are secondarily transferred collectively by the secondary transfer roller 34 to the transfer material 1 fed from the cassette 2 by the pickup roller 16 at a predetermined timing. The At this time, a predetermined voltage (positive voltage in this embodiment) is applied to the secondary transfer roller 34 by the power source 35 as shown in FIG. After the transfer, the toner 22 remains on the intermediate transfer belt 30 as a transfer residual toner. Thereafter, the transfer material 1 is conveyed to the fixing device 19, and the toner image is fixed on the transfer material 1 by heating and pressing by the fixing device 19. The fixed transfer material 1 is discharged out of the apparatus, and a series of image forming steps. Ends.

[System configuration of image forming apparatus]
FIG. 2 is a block diagram for explaining a system configuration of the image forming apparatus according to the present exemplary embodiment. The controller unit 201 can communicate with the host computer 200 and the engine control unit 202. The controller unit 201 receives image information and a print command from the host computer 200, analyzes the received image information, and converts it into bit data. The controller unit 201 sends a print reservation command, a print start command, and a video signal to the engine control unit 202 for each transfer material via the video interface unit 210.

  The controller unit 201 transmits a print reservation command to the engine control unit 202 in accordance with a print command from the host computer 200, and transmits a print start command to the engine control unit 202 at a timing when printing is possible. The engine control unit 202 prepares to execute printing in the order of print reservation commands from the controller unit 201 and waits for a print start command from the controller unit 201. When the engine control unit 202 receives the print start command, the engine control unit 202 outputs a / TOP signal serving as a reference timing for outputting a video signal to the controller unit 201, and starts a printing operation according to the print reservation command. In the engine control unit 202, the CPU 41 controls the image control unit 213, the fixing control unit 214, the paper transport unit 215, the paper feed control unit 216, and the transfer control unit 217 to execute image forming processing necessary for the printing operation. The transfer control unit 217 causes the transfer voltage control unit 44 to calculate the target transfer voltage based on the detection result of the environment sensor 43 and the current detected by the current detection unit 42, and stores the result in the memory 40. The environment sensor 43 may be a sensor that detects the temperature of the intermediate transfer belt 30.

[ATVC]
When primary transfer of the toner image at the time of image formation, that is, when the toner image on each of the photosensitive drums 9M to 9K is transferred onto the intermediate transfer belt 30, constant voltage control described below is performed at least once. In order to cope with endurance fluctuations and environmental fluctuations of the resistance values of the primary transfer portion and the intermediate transfer member, the primary transfer portion is controlled at a constant current with a preset value for the non-image area on the photosensitive drum. Then, ATVC control (Active Transfer Voltage) that detects the resistance fluctuation of the primary transfer portion from the fluctuation of the generated voltage value during the constant current control and performs the constant voltage control based on the result of calculating the previous generated voltage value during the image formation. Control, hereinafter referred to as ATVC). Further, the resistance detection control is a control for detecting the resistance fluctuation of the primary transfer portion from the fluctuation of the generated voltage value during the constant current control.

  Here, ATVC will be described with reference to FIG. In FIG. 3, the horizontal axis represents the transfer voltage (V), and the vertical axis represents the transfer current (A). Taking magenta 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 voltage controller 44M controls the transfer power supply 45M to apply three kinds of voltages of predetermined transfer voltages (Vft1, Vft2, Vft3) to the primary transfer roller 13M, and the current values (Ift1, Ift2, Ift3). Is detected by the current detector 42. The transfer voltage control unit 44 calculates a target transfer voltage Vfttarget corresponding to the target transfer current Iftarget and sets it as the target transfer voltage. This control is performed independently for each color. The calculated target transfer voltage Vfttarget is stored in the memory 40 of the engine control unit 202. Hereinafter, the target transfer voltage may be referred to as a primary transfer voltage set value.

[Photosensitive drum layer structure]
The photosensitive drums 9M to 9K used in this embodiment will be described. Note that symbols Y, M, C, and K representing colors are omitted unless necessary. FIG. 4A shows the layer structure of the initial photosensitive drum 9, and FIG. 4B shows the layer structure of the photosensitive drum 9 after being used for a long time. 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. (Charge generation layer) 94 and 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 a coat layer may be applied on the CT layer 95, it is not employed in a low-cost machine with a small total number of prints in order to reduce costs. 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 by charging and cleaning, and is repeatedly set so that two sheets of A4 size paper are passed (hereinafter referred to as “two intermittent paper passes”). ), The thickness is reduced to about 10 μm.

[Transfer contrast and primary transfer current]
Next, transfer failure due to the CT layer 95 being cut will be described. FIG. 5 shows the relationship between the transfer contrast and the primary transfer current in the two states of the photosensitive drum 9. In FIG. 5, the horizontal axis represents the primary transfer current (μA), and the vertical axis represents the transfer contrast (V). Here, the transfer contrast refers to the absolute value of the difference between the surface potential of the photosensitive drum 9 and the primary transfer voltage. The photosensitive drum 9 of the present embodiment uses a negative-polarity OPC photosensitive member. The photosensitive drum 9 indicated by a solid line is in an initial state of use, and the thickness of the CT layer 95 is 20 μm (hereinafter referred to as “initial drum”). Called). On the other hand, the photosensitive drum 9 indicated by a dotted line is in a state after printing 20000 sheets (20k sheets) of two A4 size sheets intermittently and the film thickness of the CT layer 95 is 10 μm (hereinafter referred to as “endurance”). Called "drums").

  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 the transfer contrast is the same as in the initial stage of use, the primary transfer current flows more than in the initial drum. As a result, 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. Therefore, when the initial target current of 5 μA is applied to the durable drum as it is, a sufficient transfer contrast cannot be obtained, causing a transfer failure. The lifetime of the photosensitive drum 9 is stored in a nonvolatile memory (not shown) by predicting the film thickness of the photosensitive drum (hereinafter referred to as drum film thickness). The initial drum film thickness of 20 μm is defined as 100%, and the drum film thickness after durability of 10 μm is defined as 0%. The lifetime in the meantime is linearly interpolated. The drum film thickness is predicted for each time the photosensitive drum is rotating, that is, for each usage amount of the photosensitive drum.

[Performance of print operation and primary transfer operation]
Next, the sequence of the printing operation and the primary transfer operation will be described. It is assumed that the process speed is a certain speed. FIG. 6 shows the execution timing of the printing operation and the primary transfer operation. Here, the printing operation refers to pre-rotation, image formation, and post-rotation operations, and the primary transfer operation refers to a high-pressure start-up operation and an ATVC operation. First, an outline will be described. Conventionally, resistance detection control is always performed during the pre-rotation before image formation (FIG. 6A). In the present invention, the primary transfer voltage setting value is stored for each environmental fluctuation and drum film thickness, and the previously stored primary transfer voltage setting value is used without performing the resistance detection control that was performed before image formation. To print.

  The stored primary transfer voltage setting value is a predicted primary transfer predicted from the measured primary transfer voltage setting value (first voltage) determined by actually performing resistance detection control and the measured primary transfer voltage setting value. There is a voltage setting value (second voltage), and the operation sequence differs accordingly. The measured primary transfer voltage set value is a primary transfer voltage set value obtained as a result of resistance detection control, and the predicted primary transfer voltage set value is calculated based on the measured primary transfer voltage set value. The primary transfer voltage setting value.

  FIG. 6B is an operation sequence when there is a measured primary transfer voltage setting value. In this case, the resistance detection control is not performed and the printing operation is performed. FIG. 6C shows an operation sequence when there is a predicted primary transfer voltage setting value. In this case, resistance detection control is not performed before the image forming operation, printing is performed with the predicted primary transfer voltage setting value, and resistance detection control is performed in the post-rotation after the image formation is completed. The result of performing the resistance detection control is stored as a measured primary transfer voltage set value, and when printing in the same environment next time, the sequence of FIG. 6B is executed. By performing such an operation sequence, the FPOT can be shortened and the life of the photosensitive drum (hereinafter referred to as drum life) can be extended.

[Storage of measured primary transfer voltage setting value and predicted primary transfer voltage setting value in memory]
Next, storage of the measured primary transfer voltage setting value and the predicted primary transfer voltage setting value in the memory will be described below with reference to FIG. In the following description, the target of environmental fluctuation, which is a fluctuation factor, is the temperature of the intermediate transfer belt 30. First, FIG. 7 shows the state of the memory 40 of the engine control unit 202 regarding the primary transfer voltage setting value. On the horizontal axis, the temperature (unit: ° C.) of the intermediate transfer belt 30 is divided into six regions for each temperature. The area of the memory 40 may be divided for each temperature and humidity. Specifically, the temperature is divided into six regions of less than 10 ° C, 10 ° C-15 ° C, 15 ° C-20 ° C, 20 ° C-25 ° C, 25 ° C-30 ° C, and higher than 30 ° C. In this embodiment, a temperature sensor (environment detection sensor) for monitoring the temperature of the intermediate transfer belt 30 is used. However, a temperature sensor, a humidity sensor, and a temperature / humidity sensor for measuring the temperature inside or around the image forming apparatus. It may be configured to have. When the humidity is low, it is necessary to set the primary transfer voltage with the same tendency as when the temperature is low, and either a humidity sensor or a temperature / humidity sensor may be used. On the vertical axis, the drum life is divided into four regions of 75% -100%, 50% -75%, 25% -50%, and 0% -25%. In this embodiment, a combination of 6 × 4 (= 24 regions) is used as an example. However, the regions may be subdivided or the result of neighboring may be linearly interpolated.

  Next, a method for updating the memory 40 will be described with reference to FIG. FIG. 7A shows an initial state of the memory 40 having no primary transfer voltage setting value. When printing is started in this state, resistance detection control is performed by pre-rotation as shown in FIG. As shown in FIG. 7B, the result of executing the resistance detection control is related to the temperature of the intermediate transfer belt detected by the environmental sensor 43 at the time of ATVC and the drum life stored in the nonvolatile memory. The measured primary transfer voltage setting value is stored in the corresponding area of 40. Hereinafter, the temperature of the intermediate transfer belt is referred to as “belt temperature”. In the example of FIG. 7B, when the belt temperature detected by the environment sensor 43 is 20 to 25 ° C. and the drum life stored in the nonvolatile memory is 75% to 100%, the result of performing resistance detection control. Are stored in a corresponding area (black background color) of the memory 40.

At this time, the primary transfer voltage setting value at another drum life (predicted usage amount of the photosensitive drum) in the same temperature region is predicted and stored as the predicted primary transfer voltage setting value (FIG. 7C). The prediction method is calculated using Equation 1 below.
Vfttarget = α × (Vft_cur × Dlife_tar / Dlife_cur) + β (Expression 1)
Vft_cur: Result of resistance detection control (primary transfer voltage)
Dlife_cur: drum life when the result of resistance detection control is stored Dlife_tar: drum life for predicting primary transfer voltage setting value α, β: coefficient

  Note that Vft_cur, which is the result of performing resistance detection control, is a measured primary transfer voltage setting value stored in the area of the memory 40. As shown in FIG. 7 (c), the results predicted according to the above-described equation 1 are stored in three categories of drum life 0% -25%, drum life 25% -50%, drum life 50% -75% ( Gray background). Dlife_cur is the actual drum life when the result of resistance detection control is stored. The drum life is calculated from the time when the photosensitive drum 9 is rotated as described above. Dlife_tar is the center value of each drum life value. For example, when the drum life is 0% to 25%, it is set to 12.5%. When the belt temperature detected by the environmental sensor 43 is 20-25 ° C. and the drum life stored in the non-volatile memory is in the region of 75% -100% when the printing is started next time, the correspondence of the memory 40 The measured primary transfer voltage setting value is stored in the area to be used. Therefore, as shown in FIG. 6B, printing is performed without performing ATVC in the pre-rotation. At that time, the primary transfer voltage used for printing uses the measured primary transfer voltage setting value stored in the memory 40 (black background color).

  On the other hand, when the belt temperature detected by the environment sensor 43 is 20-25 ° C. and the drum life stored in the nonvolatile memory is 0% -25%, 25% -50%, 50% -75%, the memory 40 Predicted primary transfer voltage setting values are stored in the corresponding areas. For this reason, as shown in FIG. 6C, resistance detection control is not performed in the pre-rotation, and printing is performed. At this time, the predicted primary transfer voltage setting value stored in the memory 40 is used as the primary transfer voltage setting value used for printing (gray background color). Thereafter, resistance detection control is performed in the post-rotation. For example, assuming that the belt temperature is 23 ° C. and the drum life is 60% when ATVC is performed, the belt temperature of the memory 40 is 20 ° C. to 25 ° C. and the drum life is 50% to 75% as shown in FIG. The result of the resistance detection control is updated as the measured primary transfer voltage setting value in the area of. On the other hand, when the belt temperature changes, the resistance detection control during the previous rotation (FIG. 6A) is performed again. Printing is started when the belt temperature detected by the environmental sensor 43 is 15-20 ° C. and the drum life is 25% -50% stored in the nonvolatile memory. In this case, resistance detection control is performed in the previous rotation, and the measured primary transfer voltage setting value is stored in the corresponding area of the memory 40 as shown in FIG. 7E, and the value corresponding to the remaining drum life is predicted. calculate. The calculation method follows equation (1). In FIG. 7E, the predicted primary transfer voltage setting values of drum life 75% -100% and 50% -75% are taken into consideration for the replacement of the cartridge.

  By repeating the above operation, the area of the memory 40 is updated from the white “resistance detection control not performed” to the black “measured primary transfer voltage setting value” and the gray “predicted primary transfer voltage setting value”. Go. Eventually, if all the areas of all the memories 40 become black “measurement primary transfer voltage setting values”, resistance detection control is not performed in the forward rotation and the backward rotation as shown in FIG. Printing can be performed.

[Process for storing primary transfer voltage setting value]
FIG. 8 is a flowchart for explaining processing for storing the primary transfer voltage setting value in the memory 40. First, printing is started, and the CPU 41 detects the belt temperature of the intermediate transfer belt by the environmental sensor 43 in step (hereinafter referred to as S) 1 and reads the drum life from the nonvolatile memory. Next, in S2, the CPU 41 determines whether or not the measured primary transfer voltage setting value is stored in an area corresponding to the belt temperature detected by the environmental sensor 43 in S1 of the memory 40 and the drum life read from the nonvolatile memory. Determine whether. If the CPU 41 determines that the measured primary transfer voltage setting value is stored in S2, the CPU 41 performs printing without executing resistance detection control as shown in FIG. 6B in S3 and ends the printing. In this printing, the measured primary transfer voltage setting value stored in the memory 40 is used. If the CPU 41 determines in S2 that the measured primary transfer voltage setting value is not stored, it determines whether or not the predicted primary transfer voltage setting value is stored in the corresponding area of the memory 40 in S4. . If the CPU 41 determines that the predicted primary transfer voltage setting value is stored in S4, the CPU 41 performs printing using the stored predicted primary transfer voltage setting value in S5.

  Thereafter, the CPU 41 performs resistance detection control by post-rotation as shown in FIG. Then, the CPU 41 detects the measured primary transfer voltage set value obtained as a result of the resistance detection control in the post-rotation in S7, the belt temperature detected by the environmental sensor 43 in S1 of the memory 40, and the drum read from the nonvolatile memory. The data is stored in an area corresponding to the life and printing is finished. If the CPU 41 determines in S4 that the predicted primary transfer voltage setting value is not stored, it executes resistance detection control in the previous rotation as shown in FIG. 6A in S8. The CPU 41 performs printing using the measured primary transfer voltage setting value obtained as a result of the resistance detection control in the pre-rotation in S9. The CPU 41 detects the measured primary transfer voltage setting value obtained as a result of the resistance detection control by the pre-rotation in S10, the belt temperature detected by the environmental sensor 43 in S1 of the memory 40, and the drum life read from the nonvolatile memory. Is stored in the area corresponding to. Thereafter, the CPU 41 stores both the measured primary transfer voltage setting value and the predicted primary transfer voltage setting value in the area of the memory 40 where the drum life is different in the temperature range to which the belt temperature detected by the environment sensor 43 belongs in S11. Determine if there is no predictable region. If the CPU 41 determines that there is an area in the memory 40 where the primary transfer voltage setting value can be predicted in S11, the CPU 41 calculates the predicted primary transfer voltage setting value in S12 and stores it in the memory 40. Thereafter, printing is terminated. If the CPU 41 determines in S11 that there is no area in the memory 40 where the primary transfer voltage setting value can be predicted, the printing is terminated.

  The memory 40 may be a volatile memory or a nonvolatile memory. When the nonvolatile memory is used, the usability is further improved because the resistance detection control does not have to be performed again by turning the power off and on. In the present embodiment, an example is described in which the process is performed at one process speed. However, when there are a plurality of process speeds, it is desirable to have primary transfer voltage setting values in the plurality of speed memories 40. For example, when the image forming apparatus has a 1/1 speed, 1/2 speed, and 1/3 speed process speed, each primary transfer voltage setting value can be stored for each process speed. In other words, the memory 40 has a storage area for each process speed. When printing is performed at each speed, the corresponding primary transfer voltage setting value is updated. By adopting this configuration, it is possible to perform printing without performing resistance detection control at each speed as shown in FIG. Further, in the present embodiment, the form of performing resistance detection control at the time of post-rotation as shown in FIG. 6C has been described, but resistance detection is performed during a sequence other than image formation such as calibration, cleaning, and initial rotation. Control may be implemented and results updated.

  According to this embodiment, it is possible to shorten the FPOT and reduce the frequency of performing resistance detection control while maintaining the image quality, thereby extending the life of the photosensitive drum.

  Description of the same parts of the second embodiment as those of the first embodiment is omitted. In the present embodiment, a configuration in which not only the primary transfer voltage setting value but also the drum life when the ATVC is performed (the accumulated usage amount of the photosensitive drum) is stored in the memory will be described. When predicting the predicted primary transfer voltage setting value, the prediction accuracy can be improved by using the drum life stored in the memory.

[Measured primary transfer voltage setting value, predicted primary transfer voltage setting value and drum life]
First, FIG. 9 shows the state of the memory 40 regarding the primary transfer voltage setting value and the drum life. The area in the left column shows the primary transfer voltage set value, and the area in the right column shows the drum life when resistance detection control is performed. The area where the drum life when the resistance detection control of the memory 40 is stored is hereinafter referred to as a second storage area. As in the first embodiment, the temperature (unit: ° C.) of the intermediate transfer belt 30 is divided into six regions on the horizontal axis.

  Next, the update method of the present embodiment of the memory 40 will be described with reference to FIG. FIG. 9A shows an initial state where there is no primary transfer voltage setting value. When printing is started in this state, resistance detection control is performed by pre-rotation as shown in FIG. As shown in FIG. 9B, the result of executing the resistance detection control is related to the belt temperature detected by the environmental sensor 43 when the resistance detection control is executed, and the drum life stored in the nonvolatile memory. Are stored as measured primary transfer voltage setting values (black background color). In the example of FIG. 9B, when the belt temperature detected by the environment sensor 43 is 20-25 ° C. and the drum life stored in the nonvolatile memory is 75% -100%, the result of the measured primary transfer voltage setting value Is stored in a corresponding area of the memory 40. At that time, the drum life when the resistance detection control is performed is the belt temperature 20-25 ° C. detected by the environment sensor 43 in the second storage area of the memory 40, and the drum life 75% -100 stored in the nonvolatile memory. Store in the% area. In the case of the present embodiment, 99% of the drum life when the resistance detection control is performed is stored.

  Next, when the belt temperature detected by the environmental sensor 43 is 20-25 ° C. and the drum life stored in the nonvolatile memory is in the section of 50% -75% when printing is started next, FIG. 6B. In this way, the resistance detection control is not performed during the pre-rotation, and printing is performed. At that time, as shown in FIG. 9C, the primary transfer voltage setting value used for printing is measured according to the equation (1), and the measured primary transfer voltage setting value and resistance detection control for 75% -100% of the drum life are performed. The predicted primary transfer voltage set value predicted using the drum life (99%) at the time is used. Specifically, Vft_cur in equation (1) is a measured primary transfer voltage setting value obtained as a result of resistance detection control of drum life 75% -100%, Dlife_cur is drum life 99%, and Dlife_tar is non-volatile. The current drum life stored in the memory is used. Note that the predicted predicted primary transfer voltage setting value may be stored in the corresponding area of the memory 40 at this time.

  Thereafter, resistance detection control is performed in the post-rotation, and the primary transfer voltage set value is updated as shown in FIG. At that time, the drum life when the resistance detection control is performed is stored in a corresponding area of the second storage area. In this embodiment, for example, 74% is stored. On the other hand, when the belt temperature detected by the environmental sensor 43 changes, resistance detection control is separately performed. When printing is started at a belt temperature of 15-20 ° C. and a drum life of 25% -50%, the measured primary transfer voltage setting value is stored in a corresponding area of the memory 40 as shown in FIG. At this time, for example, 49% of the drum life is stored in the corresponding area of the second storage area.

  By repeating the above-described operation, the white “resistance detection control not performed” in the memory 40 is updated to the black “measurement primary transfer voltage setting value”. If the memory 40 finally becomes the “measurement primary transfer voltage setting value” that is all black, it is possible to perform printing without performing resistance detection control in both the forward rotation and the rear rotation as shown in FIG. 6B. Become. As a result, it is possible to shorten the FPOT and extend the drum life while maintaining a good image.

[Process for storing primary transfer voltage setting value]
FIG. 10 is a flowchart for explaining processing for storing the primary transfer voltage setting value of this embodiment. First, printing is started. In S21, the CPU 41 detects the belt temperature of the intermediate transfer belt by the environment sensor 43, and reads the drum life from the nonvolatile memory. Next, the CPU 41 determines whether or not there is a measured primary transfer voltage setting value in the belt temperature region to which the temperature detected by the environmental sensor 43 stored in the memory 40 in S22 belongs. If the CPU 41 determines in S22 that the measured primary transfer voltage setting value is in the belt temperature region to which the temperature detected by the environment sensor 43 belongs, the current drum life is the measured primary transfer voltage setting value in S23. It is determined whether or not it belongs to a certain drum life region. If the CPU 41 determines in S23 that the current drum life belongs to the drum life region having the measured primary transfer voltage setting value, the measurement 1 stored in the drum life region to which the current drum life belongs in S24. Printing is performed using the next transfer voltage setting value. In this case, printing without performing resistance detection control as shown in FIG. 6B is performed, and printing is terminated.

  If the CPU 41 determines in S23 that the current drum life does not belong to the drum life region having the measured primary transfer voltage setting value, the CPU 41 calculates the equation (1) based on the measured primary transfer voltage setting value determined to be S22. ) To calculate the predicted primary transfer voltage set value in S25. Next, the CPU 41 performs printing using the predicted primary transfer voltage setting value calculated in S26. And CPU41 implements resistance detection control by post-rotation like FIG.6 (c) by S27. Further, in S28, the CPU 41 stores the measured primary transfer voltage setting value and the drum life obtained as a result of the resistance detection control in the post rotation in the corresponding area of the memory 40 and the corresponding area of the second storage area. Finish printing.

  If the CPU 41 determines in S22 that there is no measured primary transfer voltage setting value in the belt temperature region to which the temperature detected by the environment sensor 43 belongs, the resistance detection control is performed in the previous rotation in S29. Thereafter, the CPU 41 performs printing using the measured primary transfer voltage setting value obtained as a result of the resistance detection control in S30. Then, the CPU 41 stores the measured primary transfer voltage setting value and the drum life obtained as a result of the resistance detection control in the pre-rotation in S31 in the corresponding area of the memory 40 and the corresponding area of the second storage area. . Thereafter, printing is terminated. By storing the drum life when resistance detection control is performed as in this embodiment, prediction can be performed with high accuracy, and a better image can be printed.

  In the process of S24, printing was performed using the measured primary transfer voltage setting value stored in the corresponding area of the memory 40. However, if the drum life stored in the second storage area is different from the current drum life, printing may be performed using the predicted primary transfer voltage setting value predicted using Equation (1). .

  According to this embodiment, it is possible to shorten the FPOT and reduce the frequency of performing resistance detection control while maintaining the image quality, thereby extending the life of the photosensitive drum.

  Description of the same parts of the third embodiment as those of the first embodiment and the second embodiment is omitted. In this embodiment, an embodiment in which the electrostatic capacity of the intermediate transfer belt 30 changes according to the life and the target transfer current Iftarget must be changed in the middle will be described. When the electrostatic capacity of the intermediate transfer belt 30 changes according to the lifetime, it is necessary to perform resistance detection control again when the lifetime of the intermediate transfer belt 30 has exceeded a predetermined threshold. The configuration of this embodiment will be described below.

  The CPU 41 stores information on a counter (hereinafter referred to as a rotation time counter) that counts the total rotation time of the intermediate transfer belt 30 in a non-volatile memory (device usage amount storage means). The total rotation time of the intermediate transfer belt 30 corresponds to the amount of use of the image forming apparatus. Then, for example, it counts every second and updates to the non-volatile memory every 10 seconds. Here, for example, every time the total rotation time of the intermediate transfer belt 30 is 1000000 seconds, the primary transfer voltage setting value stored in the memory 40 is cleared, and the value of the rotation time counter is also cleared. The above threshold is determined according to the characteristics of the intermediate transfer belt 30.

[Process for storing primary transfer voltage setting value]
FIG. 11 is a flowchart illustrating a process for storing the primary transfer voltage setting value. First, printing is started, and the CPU 41 reads the value of the rotation time counter in S41. In S42, the CPU 41 determines whether or not the rotation time count is greater than a predetermined threshold value. When the CPU 41 determines that the value of the rotation time counter is larger than the predetermined threshold value in S42, it is necessary to perform the resistance detection control again. Therefore, the measured primary transfer voltage setting value stored in the memory 40 in S43. The predicted primary transfer voltage setting value is cleared (erased). Next, in S44, the CPU 41 clears the value of the rotation time counter and proceeds to S45.

  Hereinafter, the contents of S45 to S59 of this flowchart are substantially the same as the contents of S1 to S10 of the flowchart of FIG. In this embodiment, after printing without executing resistance detection control in S47, the value of the rotation time counter is updated in S48, and the measured primary transfer voltage setting value is stored in S52 and S56. The difference is that the value of the rotation time counter is updated in S57.

  When the primary transfer voltage setting value is cleared, there is no primary transfer voltage setting value shown in FIG. When printing is started in this state, the resistance detection control is performed again by the pre-rotation as shown in FIG. Thereafter, as described in the first embodiment, the primary transfer voltage set value is updated. If the intermediate transfer belt 30 is replaceable and has a sensor that can detect the replacement, the primary transfer voltage setting value is cleared at the time of replacement, and the value of the rotation time counter is also cleared. . In this embodiment, the method for counting the total rotation time of the intermediate transfer belt 30 has been described. However, the amount of use of the apparatus is calculated based on the print count counted for each sheet and the life of the intermediate transfer belt 30. Also good. In the present embodiment, an example is shown in which the resistance detection control is re-executed when the device usage amount reaches a predetermined threshold based on the first embodiment. However, the device usage amount is predetermined based on the second embodiment. When the threshold value is reached, the resistance detection control may be re-executed.

  According to this embodiment, it is possible to shorten the FPOT and reduce the frequency of performing resistance detection control while maintaining the image quality, thereby extending the life of the photosensitive drum.

DESCRIPTION OF SYMBOLS 1 Transfer material 9 Photosensitive drum 10 Charging roller 11 Exposure apparatus

Claims (12)

A photoreceptor ,
Developing means for forming a toner image by applying a developer to the latent image formed on the photoreceptor ;
Transfer means for transferring a toner image formed on the photoreceptor ;
Voltage application means for applying a voltage to the transfer means;
Current detection means for detecting a current flowing through the transfer means;
And control means for controlling the voltage that will be applied to the transfer means by said voltage applying means,
Have
Wherein, at a timing other than the image forming, before SL voltage control for determining the first voltage based on the current detected by said current detecting means in a state of being applied a voltage to said transfer means by the voltage applying means was carried out, at the time of image formation, the image forming apparatus for controlling the voltage applying means to apply a first voltage determined in the voltage control to the transfer means,
The control means is capable of predicting the film thickness of the photosensitive member, determines the first voltage by performing the voltage control at least once before starting image formation, and determines the first voltage. and voltage to determine the thickness of the photosensitive member to different prediction from the thickness of the photosensitive member at the time of determining the first voltage, the second voltage based on,
Next, when the image is formed, the first voltage or the second voltage corresponding to the film thickness of the photosensitive member is applied to the transfer unit without performing the voltage control before starting the image formation. An image forming apparatus, wherein the voltage applying unit is controlled to be applied to the image forming apparatus. The image forming apparatus according to claim 1, wherein the control unit predicts a film thickness of the photoconductor based on a time when the photoconductor is rotated. An intermediate transfer member to which a toner image formed on the photosensitive member is transferred;
The transfer means, the image forming apparatus according to claim 1 or 2, characterized in that for transferring the toner image formed on the photosensitive member to the intermediate transfer member. Storage means for storing the first voltage and the second voltage;
The storage means is divided according to the film thickness of the photoreceptor ,
Said control means, said first voltage storing the first voltage to the segments corresponding to the thickness of the photosensitive member when the determining, the predicted when determining the second voltage sensitive the image forming apparatus according to claim 1 or 2, characterized in that for storing the second voltage to the segments corresponding to the thickness of the body. When the control unit determines the first voltage in the film thickness of the photoconductor corresponding to the section of the storage unit in which the second voltage is stored, the control unit sets the second voltage to the second unit. The image forming apparatus according to claim 4, wherein the image forming apparatus is replaced with a first voltage. Having an environment detecting means for detecting temperature or temperature / humidity in or around the image forming apparatus;
The control means, the temperature or each temperature and humidity environment detecting unit detects the image forming apparatus according to claim 4, characterized in that determining said first voltage to determine said second voltage. Storage means for storing the first voltage and the second voltage ;
Means for detecting the temperature of the intermediate transfer member ;
Have
The storage means is classified according to the film thickness of the photosensitive member and the temperature of the intermediate transfer member,
Wherein said control means stores the first voltage to the segments corresponding to the temperature of the photosensitive member having a thickness and said intermediate transfer member when determining the first voltage, determining said second voltage 4. The image forming apparatus according to claim 3 , wherein the second voltage is stored in the section corresponding to the predicted film thickness of the photosensitive member and the temperature of the intermediate transfer member. When the control unit determines the first voltage in the film thickness of the photoconductor and the temperature of the intermediate transfer member corresponding to the section of the storage unit in which the second voltage is stored, The image forming apparatus according to claim 7, wherein the second voltage is replaced with the first voltage.   The image forming apparatus according to claim 4, wherein the storage unit has a storage area for each process speed.   The image forming apparatus according to claim 4, wherein the storage unit is a nonvolatile memory. Second storage means for storing an accumulated usage amount of the photosensitive member when the first voltage is determined;
Said control means of claims 1 to 10, characterized in that determining the second voltage based on the integrated amount of the stored said photosensitive member to said first voltage and said second storage means The image forming apparatus according to claim 1. An apparatus usage amount storage means for storing the accumulated usage amount of the image forming apparatus;
When the control unit determines that the accumulated usage amount of the image forming apparatus stored in the apparatus usage amount storage unit is greater than a predetermined threshold value, the control unit stores the first voltage stored in the storage unit and the first voltage. The image forming apparatus according to claim 4, wherein all the voltages of 2 are erased.

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