JP2011107578A - Image forming apparatus and correction method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology for transferring a toner image, developed on the photoreceptor drum, sufficiently onto a recording medium even if a film thickness of a photoreceptor drum decreases. <P>SOLUTION: The image forming apparatus 1 has a print control unit 20. The print control unit calculates a film thickness of the photoreceptor drum 2, calculates an accumulative thickness of a ground film of the photoreceptor drum 2 by subtracting the obtained film thickness of the photoreceptor drum 2 from an initial value of the film thickness of the photoreceptor drum 2, calculates a correction value of voltage to be applied to a transfer roller 6 corresponding to the obtained accumulative thickness of the ground film, and controls transfer voltage-applying units 7 to apply post-correction voltage obtained by performing correction using the obtained correction value to the transfer roller 6. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus and a transfer voltage correction method in the image forming apparatus.

  In an electrophotographic printer, a photosensitive drum is charged, a latent image corresponding to a print image is written on the charged photosensitive drum, a toner image is developed on the latent image, and the toner image is opposite in polarity to the toner. A technique is used in which an image is printed on a recording medium by transferring the electric charge to the supplied recording medium.

Japanese Patent Laid-Open No. 7-24868

  However, in the conventional technology, the film thickness of the photosensitive drum is reduced due to an increase in the cumulative number of printed sheets in the printer, and the toner image developed on the photosensitive drum is not transferred onto the recording medium and is not easily transferred. In some cases, image quality may be deteriorated due to the above.

  Accordingly, an object of the present invention is to provide a technique capable of sufficiently transferring a toner image developed on a photosensitive drum to a recording medium even when the film thickness of the photosensitive drum is reduced. .

  In order to solve the above problems, the present invention includes an image carrier having a film carrying a developer, and a transfer unit that applies a voltage and transfers the developer developed on the image carrier to a recording medium. A film thickness calculating means for calculating the thickness of the film, and a transfer correction voltage calculating means for calculating a correction value of a voltage applied to the transfer means based on the thickness of the film calculated by the film thickness calculating means. And a transfer voltage control means for applying the corrected voltage corrected with the calculated correction value to the transfer means.

The present invention also provides an image forming apparatus having an image carrier having a film carrying a developer, and a transfer unit that applies a voltage and transfers the developer developed on the image carrier to a recording medium. A method for correcting the voltage, wherein the film thickness calculating means calculates the thickness of the film;
A step of calculating a correction value of a voltage applied to the transfer unit based on the thickness of the film calculated by the film thickness calculation unit, and a transfer voltage control unit And applying a corrected voltage corrected with a correction value to the transfer means.

  As described above, according to the present invention, even when the film thickness of the photosensitive drum is reduced, the toner image developed on the photosensitive drum can be sufficiently transferred to the recording medium.

1 is a schematic diagram of an image forming apparatus that is Embodiment 1. FIG. FIG. 2 is a schematic diagram of a print control apparatus according to the first embodiment. FIG. 3 is a schematic diagram of a photosensitive drum film shaving thickness information table according to the first embodiment. Schematic which shows the change of the value of the coefficient A in Embodiment 1. FIG. FIG. 3 is a schematic diagram of a transfer correction voltage calculation information table in the first embodiment. FIG. 3 is a schematic diagram showing a relationship between a cumulative film crack thickness and a transfer correction voltage in the first embodiment. FIG. 3 is a schematic diagram of a film thickness calculation unit in the first embodiment. 5 is a flowchart showing transfer voltage control processing in the first embodiment. FIG. 4 is a schematic diagram of a print control apparatus according to Embodiment 2. 6 is a schematic diagram of a photosensitive drum film shaving thickness information table for yellow, magenta, and cyan in Embodiment 2. FIG. Schematic which shows the change of the value of the coefficient A in Embodiment 2. FIG. Schematic of the film thickness calculation part in Embodiment 2. FIG. FIG. 10 is a schematic diagram of a print control apparatus according to Embodiment 3. FIG. 10 is a schematic diagram of a photosensitive drum film shaving thickness calculation information table when a sheet is passed in Embodiment 3. FIG. 10 is a schematic diagram of a photosensitive drum film shaving thickness calculation information table when no paper is passed in the third embodiment. Schematic of the film thickness calculation part in Embodiment 3. FIG. FIG. 10 is a schematic diagram of a photosensitive drum film shaving thickness calculation information table for a peripheral speed difference, which is a modification of the third embodiment.

Embodiment 1 FIG.
FIG. 1 is a schematic diagram of an image forming apparatus 1 according to Embodiment 1 of the present invention. The image forming apparatus 1 in the first embodiment is an example of a color image forming apparatus that obtains a color image by superimposing and printing toners that are four color developers of black, yellow, magenta, and cyan. The present invention is not limited to such an embodiment, and the present invention can be similarly applied to a monochrome image forming apparatus of one black color or a color image forming apparatus using other colors.

  As illustrated, the image forming apparatus 1 includes photosensitive drums 2K, 2Y, 2M, and 2C (the photosensitive drum 2K is a photosensitive drum for black, the photosensitive drum 2Y is a photosensitive drum for yellow, and the photosensitive drum 2M is a photosensitive drum for magenta). The photosensitive drum 2C is a cyan photosensitive drum. Hereinafter, the photosensitive drum 2C is referred to as the photosensitive drum 2 unless it is particularly necessary to distinguish between the photosensitive drum 2C and the chargers 3K, 3Y, 3M, and 3C (the charger 3K is for black). The photosensitive drum 2K charger, the charger 3Y is a charger for the yellow photosensitive drum 2Y, the charger 3M is a charger for the magenta photosensitive drum 2M, and the charger 3C is a charger for the photosensitive drum 2C for cyan. However, in the following, when it is not necessary to distinguish each of them, it is referred to as a charger 3) and exposure units 4K, 4Y, 4M, and 4C (the exposure unit 4K is a photosensitive drum 2K for black). The exposure unit, the exposure unit 4Y is an exposure unit for the photosensitive drum 2Y for yellow, the exposure unit 4M is an exposure unit for the photosensitive drum 2M for magenta, and the exposure unit 4C is an exposure unit for the photosensitive drum 2C for cyan. When there is no need to distinguish between them, they are referred to as an exposure unit 4) and developing units 5K, 5Y, 5M, and 5C (developing unit 5K is a developing unit for black photosensitive drum 2K, and developing unit 5Y is a photosensitive unit for yellow. The developing device for the drum 2Y, the developing device 5M is the developing device for the photosensitive drum 2M for magenta, and the developing device 5C is the developing device for the photosensitive drum 2C for cyan. Development unit 5).

  The image forming apparatus 1 also includes transfer rollers 6K, 6Y, 6M, and 6C (transfer roller 6K is a transfer roller for black photosensitive drum 2K, transfer roller 6Y is a transfer roller for photosensitive drum 2Y for yellow, and transfer roller 6M is a transfer roller 6M). The transfer roller of the magenta photosensitive drum 2M and the transfer roller 6C are transfer rollers of the cyan photosensitive drum 2C. Hereinafter, when it is not necessary to distinguish between them, they are referred to as transfer rollers 6) and transfer voltage application. 7K, 7Y, 7M, 7C (transfer voltage application unit 7K is a transfer voltage application unit for transfer roller 6K, transfer voltage application unit 7Y is a transfer voltage application unit for transfer roller 6Y, and transfer voltage application unit 7M is a transfer roller. The transfer voltage application unit for 6M and the transfer voltage application unit 7C are transfer voltage application units for the transfer roller 6C. Transfer roller 8, transfer roller 8, drive roller 9, idle roller 10, fixing device 11, first transport roller 12, second transport roller 13, discharge roller 14, and hopping roller. 15, a writing sensor 16, a discharge sensor 17, a support plate member 18, a spring 19, and a printing control device 20.

  The photosensitive drum 2 carries an image for transfer. The charger 3 charges each photosensitive drum 2 negatively. The exposure device 4 writes an electrostatic latent image on each photosensitive drum 2. The developing device 5 visualizes the electrostatic latent images on the respective photosensitive drums 2 with a negatively charged toner as a developer.

  The transfer roller 6 is disposed inside a transfer belt 8 formed in an endless belt shape, and is urged by an elastic member such as a spring so as to be pressed against the photosensitive drum 2 with the transfer belt 8 interposed therebetween. Yes. The transfer roller 6 is connected to a transfer voltage application unit 7.

  The transfer voltage application unit 7 generates a high voltage to be applied to each transfer roller 6. Here, the transfer voltage application unit 7 is connected to a transfer power supply device (not shown).

  The transfer belt 8 is supported by the drive roller 9 and the outer peripheral surface of the idle roller 10. The transfer belt 8 is pulled between the drive roller 9 and the idle roller 10 so that the surface where the photosensitive drum 2 and the transfer belt 8 are in contact is flat.

  The drive roller 9 is connected to a drive device (not shown) and is rotated about an axis. When the transfer belt 8 is displaced in conjunction with the rotation of the drive roller 9, the idle roller 10 rotates in the same direction as the rotation direction of the drive roller 9 in conjunction with the displacement of the transfer belt 8.

  The fixing device 11 includes a fixing roller having a heat source therein, and a backup roller urged by the urging means to the fixing roller, and fixes the toner image transferred to the recording medium 90 by heat and pressure. To do.

  A broken line in FIG. 1 is a conveyance path of the recording medium 90, and the first conveyance roller 12, the second conveyance roller 13, and the writing sensor 16 are arranged on the upstream side of the transfer belt 8 along the conveyance path. The discharge sensor 17 and the discharge roller 14 are arranged on the downstream side of the fixing device 11.

  When the recording medium 90 is conveyed along the conveyance path, the writing sensor 16 and the discharging sensor 17 are arranged at predetermined positions on the recording medium 90 (in this embodiment, the writing sensor 16 is the head position, and the discharging sensor 17 is The rear end position) is detected, and a detection signal is output to the print control apparatus 20.

  A recording medium 90 is placed on the upper surface of the support plate member 18. Below the support plate member 18, a spring 19 is provided as a biasing member that pushes the support plate member 18 upward. Then, the recording medium 90 placed on the upper surface of the support plate member 18 is pressed against the hopping roller 15 by the urging force of the spring 19, and the hopping roller 15 rotates in a direction to push the recording medium 90 to the conveyance path. Introduced into the transport path.

  The photosensitive drum 2, the hopping roller 15, the first conveying roller 12, the second conveying roller 13, the drive roller 9, the fixing device 11 (fixing roller and backup roller), and the discharge roller 14 are driving devices (for example, motors). The drive device is controlled by the print control device 20.

  FIG. 2 is a schematic diagram of the print control apparatus 20. As illustrated, the print control apparatus 20 includes a storage unit 21, a control unit 28, and an input / output port unit 34.

  The storage unit 21 includes a photosensitive drum rotation distance calculation information storage unit 22, a photosensitive drum peripheral speed information storage unit 23, a photosensitive drum film shaving thickness calculation information storage unit 24, a transfer correction voltage calculation information storage unit 25, and a photosensitive drum. A film thickness information storage unit 26. The photosensitive drum film thickness information storage unit 26 may be configured in the image forming apparatus 1, or when the photosensitive drum 2 or the unit including the photosensitive drum 2 is detachable, the photosensitive drum 2 or the photosensitive drum 2. It is good also as a structure united with the unit containing.

  The photosensitive drum rotation distance calculation information storage unit 22 stores photosensitive drum rotation distance calculation information necessary for calculating the rotation distance of the photosensitive drum 2. For example, when the photosensitive drum 2 is rotated by a stepping motor, the rotation distance of the photosensitive drum 2 per step is stored.

  The photosensitive drum peripheral speed information storage unit 23 stores photosensitive drum peripheral speed information for specifying the peripheral speed of the photosensitive drum detected by a photosensitive drum peripheral speed detector 30b described later.

  The photosensitive drum film shaving thickness calculation information storage unit 24 stores photosensitive drum film shaving thickness calculation information necessary for calculating the thickness at which the film of the photosensitive drum 2 is shaved by using the photosensitive drum 2. For example, in the present embodiment, a photosensitive drum film shaving thickness information table 24a as shown in FIG. 3 is stored.

  The film of the photosensitive drum 2 in the present embodiment is a film on the surface portion of the photosensitive drum 2, and refers to a film in a portion that contacts the toner, the recording medium 90, the exposure device 4, the developing device 5, and the like.

  The photosensitive drum film shaving thickness information table 24a includes a photosensitive drum film thickness column 24b and a peripheral speed row 24c. The photosensitive drum film thickness column 24b is provided with a plurality of columns that specify a predetermined photosensitive drum film thickness range. Further, the peripheral speed row 24c is provided with a plurality of lines for specifying a predetermined peripheral speed value of the photosensitive drum.

  The column corresponding to the column of the film thickness range specified by the film thickness column 24b of the photosensitive drum and the column of the peripheral speed specified by the peripheral speed row 24c has a unit rotational distance (here, Then, the information for specifying the coefficient A for specifying the thickness at which the photosensitive drum is shaved is stored per meter (m).

  As shown in FIG. 4, the coefficient A is such that the thicker the photosensitive drum is, the thicker the photosensitive drum is scraped. The faster the photosensitive drum is, the faster the photosensitive drum is scraped. It is designed to be thicker.

  In this respect, for example, the cause of film abrasion of the photosensitive drum includes friction between the photosensitive drum 2 and the developing device 5 and friction between the photosensitive drum 2 and a cleaning member (not shown). As the printing speed increases, the difference in member speed at each location where friction occurs increases, and the film thickness of the photosensitive drum 2 increases. For this reason, the value of the coefficient A, which is the film scraping thickness per unit rotation distance, increases as the speed increases.

  The photosensitive drum 2 and the developing device 5 are each composed of a roller, and the outer diameter of both the photosensitive drum 2 and the developing roller in the developing device 5 is reduced by friction. The developing roller is often a foam, and the outer diameter is reduced by the foam being slightly crushed by pressure. By reducing the outer diameter in this way, the pressure at the contact portion is reduced, and the thickness of the scraped film per unit rotational distance is reduced. As the photosensitive drum 2 becomes smaller, the film thickness is similarly reduced between the photosensitive drum 2 and a cleaning member (not shown). Therefore, when the outer diameter of the photosensitive drum 2 is reduced, as shown in FIG. 4, the value of the coefficient A that is the film scraping thickness per unit rotational distance of the photosensitive drum 2 is reduced.

  In this embodiment, the value of the coefficient A is changed in four steps according to the change in the film thickness of the photosensitive drum 2 and in two steps depending on the difference in peripheral speed, but may be changed more finely and continuously by calculation. It is good also as a structure to change.

  Returning to FIG. 2, the transfer correction voltage calculation information storage unit 25 stores transfer correction voltage calculation information necessary for calculating the correction value of the voltage applied to the transfer roller 6. For example, in the present embodiment, a transfer correction voltage calculation information table 25a as shown in FIG. 5 is stored.

  The transfer correction voltage calculation information table 25a includes a printing surface row 25b and a peripheral speed row 25c. The print surface row 25b is provided with a plurality of rows for specifying a method and a surface to be printed on the recording medium 90. The peripheral speed column 25c is provided with a plurality of rows for specifying a predetermined peripheral speed value of the photosensitive drum.

  Then, the column corresponding to the method and the surface column to be printed on the recording medium 90 specified by the print surface row 25b and the peripheral speed row specified by the peripheral speed row 25c is applied to the transfer roller 6. Information for specifying a coefficient B, which is a proportional constant that makes the voltage correction value proportional to the thickness of the film scraped from the photosensitive drum, is stored.

  As shown in FIG. 6, the coefficient B increases as the thickness of the film scraped from the photosensitive drum increases, and the correction value becomes larger when the printing method is single-sided printing or double-sided printing. The correction value is smaller when printing on the other side of the recording medium 90 on which one side is already printed by duplex printing than when printing on one side of the recording medium 90 where no printing is performed. In addition, the correction value is increased as the peripheral speed of the photosensitive drum increases.

  Here, in the coefficient B, the state of the printing method (printing surface) is taken into account because the dry state of the recording medium 90 changes as it passes through the fixing device 11. The value of the coefficient B may be obtained by calculation by electric field simulation, or may be obtained experimentally by printing using a photosensitive drum having a different film thickness.

  Returning to FIG. 2, the photosensitive drum film thickness information storage unit 26 specifies the initial value of the film thickness of the photosensitive drum 2 (the film thickness at the beginning of use of the photosensitive drum 2 or the designed film thickness of the photosensitive drum 2). Information and information specifying the film thickness of the photosensitive drum 2 calculated by the photosensitive drum film thickness calculation unit 30c described later are stored for each photosensitive drum 2.

  The control unit 28 includes a print control unit 29, a film thickness calculation unit 30, a transfer correction voltage calculation unit 31, and a transfer voltage control unit 32.

  The print control unit 29 controls the entire printing process in the image forming apparatus 1. For example, the print controller 29 controls operations of the charger 3, the exposure device 4, the developing device 5, the fixing device 11, the writing sensor 16, and the discharge sensor 17. The print control unit 29 includes a photosensitive drum 2, a hopping roller 15, a first conveyance roller 12, a second conveyance roller 13, a drive roller 9, a fixing device 11, a motor for rotating the discharge roller 14, and the like. A drive device (not shown) is controlled.

  The film thickness calculation unit 30 calculates the film thickness of each photosensitive drum 2. For example, as shown in FIG. 7, the film thickness calculation unit 30 includes a photosensitive drum rotation distance measurement unit 30a, a photosensitive drum peripheral speed detection unit 30b, and a photosensitive drum film thickness calculation unit 30c. The film thickness of the photosensitive drum 2 is calculated.

  The photosensitive drum rotation distance measuring unit 30a measures the distance that the photosensitive drum 2 has rotated for each print job (command specifying the object to be printed and the number of sheets). For example, when the photosensitive drum 2 is rotated by a stepping motor, the photosensitive drum rotation distance measuring unit 30a measures the number of steps, and the photosensitive drum rotation distance calculation information storage unit 22 stores the photosensitive drum per step. By multiplying the rotation distance of the drum 2, the distance that the photosensitive drum 2 has rotated is calculated.

  The photosensitive drum peripheral speed detection unit 30b detects the peripheral speed designated by the print control unit 29 as the print speed for each print job, and stores the detected peripheral speed in the photosensitive drum peripheral speed information storage unit 23. The peripheral speed may be detected by detecting the peripheral speed from a command from the print control unit 29 to a driving device (not shown), or inquiring the print control unit 29 or notifying from the print control unit 29. You may receive.

  The photosensitive drum film thickness calculation unit 30c calculates the film thickness scraped from the photosensitive drum 2 from the rotational distance of the photosensitive drum 2 and the peripheral speed of the photosensitive drum 2 for each print job, and the film thickness of the photosensitive drum 2 before the start of the print job. Is subtracted from the thickness of the photosensitive drum 2 after the print job. The photosensitive drum film thickness calculation unit 30c is configured so that the film thickness removed from the photosensitive drum 2 becomes thicker as the rotational distance of the photosensitive drum 2 is longer and the peripheral speed of the photosensitive drum 2 is faster. The film thickness to be shaved from is calculated.

  Then, the photosensitive drum film thickness calculation unit 30c specifies the film thickness of the photosensitive drum 2 after the calculated print job using the information specifying the film thickness of the photosensitive drum 2 stored in the photosensitive drum film thickness information storage unit 26. Update to the information you want.

  Returning to FIG. 2, the transfer correction voltage calculation unit 31 subtracts the film thickness of the photosensitive drum 2 from the initial value of the film thickness of the photosensitive drum 2 stored in the photosensitive drum film thickness information storage unit 26 for each print job. Thus, the cumulative value of the film shaving thickness is calculated, and the transfer correction voltage determined by the calculated cumulative value of the film shaving thickness is determined. Here, the transfer correction voltage is set to increase as the cumulative value of the film shaving thickness increases, that is, as the film thickness decreases.

  The transfer voltage control unit 32 calculates the corrected transfer voltage by adding the transfer correction voltage calculated by the transfer correction voltage calculation unit 31 to the transfer voltage of the transfer roller 6 determined by the printing conditions, and calculates the corrected transfer voltage after correction. The voltage is notified to the transfer voltage application unit 7. Upon receiving such notification, the transfer voltage application unit 7 applies the corrected transfer voltage to the transfer roller 6.

  The input / output port unit 34 transmits / receives information to / from an external device such as a personal computer.

  The print control apparatus 20 described above can be realized by, for example, a CPU (Central Processing Unit), a memory such as a ROM (Read-Only Memory) or a RAM (Random-Access Memory), and an input / output interface. it can. For example, the storage unit 21 can be realized by the CPU using a memory, and the control unit 28 can be realized by the CPU executing a predetermined program stored in the memory, and the input / output port unit 34 can be realized by the CPU using the input / output interface.

  However, the printing control apparatus 20 of the present embodiment is not limited to the above-described form, and is implemented by an integrated logic IC such as an ASIC (Application Specific Integrated Circuits) or an FPGA (Field Programmable Gate Array). It may be realized by a digital signal processor (DSP) or the like.

  The image forming apparatus 1 configured as described above operates as follows.

  The print control unit 29, for example, according to a print job (print instruction) from a host controller such as a personal computer connected to the image forming apparatus 1, processes a print instruction image, transport control of the recording medium 90, charging control, exposure Control, development control, transfer control, and fixing control are performed, and as a result, printing is performed on the recording medium 90.

  For example, when the print control unit 29 receives a print job (print instruction) signal from a host controller such as a personal computer connected to the input / output port unit 34 of the print control device 20 of the image forming apparatus 1, Control is started, and the fixing device 11 is heated to a usable temperature.

  When the fixing device 11 reaches a usable temperature, the printing control unit 29 controls a driving device (not shown) to rotate the photosensitive drum 2, and the linear velocity becomes the conveyance velocity of the recording medium 90 during printing. Accelerate to.

  Further, the print control unit 29 controls a driving device (not shown) to start the rotation of the drive roller 9, and rotates the transfer belt 8 by the drive roller 9. The linear velocity of the transfer belt 8 is determined by the recording medium at the time of printing. Accelerate until the transport speed is 90.

  Further, at the timing when the photosensitive drum 2 starts to rotate, the print control unit 29 controls the charger 3 and applies a negative voltage to the photosensitive drum 2 to charge the photosensitive drum 2 to, for example, −600 V. .

  The print control unit 29 controls the developing device 5 to be in a developable state at the timing when the portion of the photosensitive drum 2 charged to −600 V passes through the developing area of the developing device 5 by rotation. For example, in the case of a contact development method using a developing roller, a developing state is obtained by applying a voltage of −200 V to a developing roller to which negatively charged toner is attached.

  When the photosensitive drum 2 is charged at −600 V and reaches the transfer nip portion by rotation, the printing process is ready for printing.

  Next, the printing control unit 29 rotates the hopping roller 15 with a driving device (not shown) to separate the recording media 90 one by one and place them on the transport path.

  When the print control unit 29 controls a driving device (not shown), the separated recording medium 90 is conveyed to the second conveying roller 13 via the first conveying roller 12. At this time, the writing sensor 16 disposed between the second conveying roller 13 and the transfer belt 8 detects the timing at which the leading end of the recording medium 90 passes the position of the writing sensor 16, and the detection result is displayed as a print control unit. 29 is notified.

  The print control unit 29 separates an image to be printed on the recording medium 90 included in the print job (print instruction) signal received from the host controller into colors of black, yellow, magenta, and cyan, and further exposes the exposure device 4. To convert the image data into writable image data.

  The recording medium 90 is conveyed onto the transfer belt 8 after passing through the writing sensor 16.

  The print controller 29 detects the timing at which the writing sensor 16 detects the leading edge of the recording medium 90, the distance from the writing sensor 16 to the transfer nip of each color, and the distance from the exposure location on the photosensitive drum 2 to the transfer location. Then, the electrostatic latent image is written on the photosensitive drum 2 by controlling the exposure device 4 at the timing when the image to be printed is transferred to a desired position on the recording medium 90 according to the conveyance speed of the recording medium 90.

  The exposure device 4 is charged to −600 V, for example, by using an LED (Light-Emitting Diode) head or the like to irradiate a portion of the photosensitive drum 2 where a toner image is to be obtained with, for example, 600 dpi pitch spot light. The surface of the photosensitive drum 2 is at a potential of about −50 V and forms an electrostatic latent image.

  The surface of the photosensitive drum 2 on which the electrostatic latent image has been written by the exposure device 4 is moved to the position of the developing device 5 by a rotating operation, and exposed to the portion where the absolute value of the surface potential is reduced by the developing device 5. The negatively charged toner that is the developer adheres to the photosensitive drum 2 by the Coulomb force, and the toner image that is a visible image is developed.

  The surface of the photosensitive drum 2 to which the developed toner image adheres reaches the transfer nip portion by a rotating operation.

  A transfer voltage for printing is applied to the transfer roller 6 during a period in which the recording medium 90 is in the transfer nip portion, and a positive voltage (for example, 1500 V to 3000 V) having a polarity opposite to that of the toner is applied.

  The toner image on the photosensitive drum 2 receives a coulomb force by a positive voltage applied to the transfer roller 6 at the transfer nip portion, and is transferred onto the recording medium 90.

  The image forming apparatus 1 sequentially performs the above charging, exposure, development, and transfer operations for black, yellow, magenta, and cyan.

  The recording medium 90 on which the toner has been developed and transferred is conveyed to the fixing device 11. The fixing device 11 melts the toner on the recording medium 90 by heat and pressure and fixes the toner on the recording medium 90.

  The discharge sensor 17 detects the timing at which the rear end of the recording medium 90 that has passed through the fixing device 11 has passed, and notifies the print control unit 29 of the detection result.

  If the print control unit 29 determines from the detection result of the discharge sensor 17 that printing of the print target and the number of sheets specified in the print job has been completed, the recording medium 90 is moved to the device of the image forming apparatus 1 by the discharge roller 14. At the timing of discharging to the outside, the operation of the driving device, the charger 3, the developing device 5, and the transfer power supply device (not shown) are stopped, and the printing is finished.

  Note that the print control unit 29 performs measures such as stopping the operation of the image forming apparatus 1 when the passage timing of the recording medium 90 is determined to be abnormal based on the detection results of the writing sensor 16 and the discharge sensor 17.

  FIG. 8 is a flowchart showing transfer voltage control processing. The film thickness calculator 30, the transfer correction voltage calculator 31, and the transfer voltage controller 32 perform the processing shown in the flowchart shown in FIG. 8 on the photosensitive drum 2 and the transfer voltage application unit 7 of each color.

  The photosensitive drum rotation distance measuring unit 30a monitors the print control unit 29 and detects that the print control unit 29 has started printing (or that the print control unit 29 has received a print job) (Yes in S100). Then, measurement of the rotational distance of the photosensitive drum 2 is started for each print job (S101).

  Then, the photosensitive drum peripheral speed detection unit 30b detects the peripheral speed V that the print control unit 29 instructs the drive device or the like as the printing speed for each print job, and the peripheral speed V is detected as the photosensitive drum peripheral speed information storage unit 23. (S102).

  Next, the transfer correction voltage calculation unit 31 calculates a correction voltage value of the transfer voltage before starting printing of each print job according to the film thickness removed from the photosensitive drum 2 (S103). Therefore, the transfer correction voltage calculation unit 31 uses the value of the film thickness of the photosensitive drum 2 at the start time (before the start) of the print job.

  For example, the transfer correction voltage calculation unit 31 receives a print job start signal from the print control unit 29, and the peripheral speed of the photosensitive drum 2 stored in the photosensitive drum peripheral speed information storage unit 23 and the print control unit 29. From the printing surface of the recording medium 90 to be printed, that is, simplex printing (single-sided printing), printing of the first side in duplex printing (double-sided printing) (one side when both sides are not printed yet), or duplex printing (double-sided printing) ) In the transfer correction voltage calculation table 25a (FIG. 5), which acquires information on whether or not the 2nd surface is printed (the other surface when one side is already printed). The coefficient B corresponding to the peripheral speed of the photosensitive drum 2 and the printing surface of the recording medium 90 is determined.

Next, the transfer correction voltage calculation unit 31 receives the initial value T0 of the film thickness of the photosensitive drum 2 and the film thickness T of the photosensitive drum 2 at the present time (before the start of the print job) from the photosensitive drum film thickness information storage unit 26. , And the cumulative film thickness T2 from the initial stage to the present time is calculated from the following formula (1).
T2 = T0−T [μm] (1)

Further, the transfer correction voltage calculation unit 31 obtains the transfer correction voltage Tr from the following equation (2) from the coefficient B and the accumulated film scraping thickness T2.
Tr = T2 × B [V] (2)

For example, assuming that the initial value T0 of the film thickness of the photosensitive drum 2 is 20 μm and the current film thickness T is 19.5 μm, the film thickness T2 at the present time is calculated from the equation (1):
T2 = 20−19.5 [μm]
= 0.5 [μm]
It becomes.

Further, if the peripheral speed V of the print job is 150 mm / S and printing is performed with Simplex, the coefficient B is 40 from the transfer correction voltage calculation information table 25a in FIG. 5, and the transfer correction voltage Tr is calculated from the equation (2):
Tr = 0.5 × 40 [V]
= 20 [V]
It becomes.

  In the present embodiment, the coefficient B is determined by the printing peripheral speed and the printing surface. However, the coefficient B is more detailed, depending on the type, thickness, size, environmental temperature and environmental humidity in which the apparatus is placed. You may change it.

  Then, the transfer correction voltage calculation unit 31 transmits the calculated transfer correction voltage Tr to the transfer voltage control unit 32.

  Next, the transfer voltage control unit 32 calculates a corrected transfer voltage at the time of printing based on the transfer correction voltage Tr received from the transfer correction voltage calculation unit 31 (S104).

  For example, the transfer voltage control unit 32 prints information such as printing medium type, thickness, size, printing peripheral speed, Simplex or Duplex printing surface, environmental temperature of the apparatus, environmental humidity, and the like, which are printing conditions. 29, the optimum transfer voltage is selected from the information. These operations are the same as those of the conventional image forming apparatus.

  Then, the corrected transfer voltage is calculated by adding the transfer correction voltage Tr to the transfer voltage thus selected.

  Next, the transfer voltage control unit 32 outputs the corrected transfer voltage calculated in step S104 to the transfer voltage application unit 7, and controls the transfer voltage application unit 7 (S105). Then, the transfer voltage application unit 7 generates a high voltage by the instruction voltage (corrected transfer voltage) of the transfer voltage control unit 32 and applies the generated high voltage to the transfer roller 6 to perform transfer.

  Next, the photosensitive drum rotation distance measuring unit 30a monitors the print control unit 29 and detects that the print job has been completed (Yes in S106), the photosensitive drum rotation distance measuring unit 30a detects the rotation distance of the photosensitive drum 2. And the rotation distance L of the photosensitive drum 2 is calculated (S107).

  Next, the photosensitive drum film thickness calculator 30c calculates the film thickness of the photosensitive drum 2 for each print job (S108).

  For example, the photosensitive drum film thickness calculation unit 30c acquires the rotation distance L that the photosensitive drum 2 has rotated by the print job from the photosensitive drum rotation distance measurement unit 30a, and is stored in the photosensitive drum peripheral speed information storage unit 23. The peripheral speed V of the photosensitive drum is obtained.

  Further, the photosensitive drum film thickness calculation unit 30 c acquires the film thickness T of the photosensitive drum 2 before the start of the print job from the photosensitive drum film thickness information storage unit 26.

  Further, the photosensitive drum film thickness calculation unit 30c stores the value of the coefficient A corresponding to the acquired peripheral speed V and the film thickness T of the photosensitive drum 2 in the photosensitive drum film shaving thickness calculation information storage unit 24. It is acquired from the photosensitive drum film shaving thickness calculation information table 24a (see FIG. 3).

Then, the photosensitive drum film thickness calculation unit 30c calculates the film scraping thickness T1 of the photosensitive drum 2 for each print job by, for example, the following equation (3).
T1 [μm] = L [m] × A [μm / m] (3)

  Next, the photosensitive drum film thickness calculation unit 30c calculates the film thickness of the photosensitive drum after the print job (S109).

For example, the photosensitive drum film thickness calculation unit 30c calculates the film thickness Tt of the photosensitive drum after the print job as follows based on the film thickness T1 calculated in step S108 and the film thickness T of the photosensitive drum 2 before the start of the print job. (4) Calculate by the formula.
Tt = T−T1 [μm] (4)

Here, in a certain print job, when L = 10 m, the printing speed is 150 mm / S, and the photosensitive drum film thickness T before the start of the print job is 19.5 μm, the coefficient A is the photosensitive drum film shaving thickness of FIG. The photosensitive drum film thickness T1 which is 0.001 from the calculation information table 24a and is worn by the print job is calculated from the equation (3).
T1 = 10 × 0.001
= 0.01 [μm]

And the film thickness Tt after the end of the print job is expressed by the following equation (4).
Tt = 19.5 [μm] −0.01 [μm]
= 19.49 [μm]
It becomes.

  Next, the photosensitive drum film thickness calculation unit 30c calculates the film thickness of the photosensitive drum stored in the photosensitive drum film thickness information storage unit 26 based on the film thickness Tt of the photosensitive drum 2 after the print job calculated in step S109. The specified information is updated (S110).

  Then, the photosensitive drum rotation distance measuring unit 30a monitors the print control unit 29 to detect whether or not there is a next print job (S111), and when there is a next print job (Yes in S111), step. Returning to S101, the process is repeated, and if there is no next print job (No in S111), the process ends.

  As described above, according to the present embodiment, even when the cumulative number of printed sheets is increased and the film thickness of the photosensitive drum 2 is reduced, an appropriate transfer voltage corresponding to the reduced film thickness is applied to the transfer roller 6. It can be applied and transfer defects such as blurring can be prevented.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described. In the second embodiment of the present invention, since the print control device 40 is different from that in the first embodiment, items related to the print control device 40 will be described below. The second embodiment of the present invention differs from the first embodiment in that the value of the coefficient A of the film thickness of the photosensitive drum 2 is changed depending on the color.

  FIG. 9 is a schematic diagram of the print control apparatus 40 according to the second embodiment of the present invention. As shown in the figure, the print control apparatus 40 includes a storage unit 41, a control unit 48, and an input / output port unit 34. The storage unit 41 and the control unit 48 are different from those in the first embodiment. Therefore, the matters related to these will be described below.

  The storage unit 41 according to the second embodiment of the present invention includes a photosensitive drum rotation distance calculation information storage unit 22, a photosensitive drum peripheral speed information storage unit 23, a photosensitive drum film shaving thickness calculation information storage unit 44, and a transfer correction voltage calculation. An information storage unit 25 and a photosensitive drum film thickness information storage unit 46 are provided, and the photosensitive drum film shaving thickness calculation information storage unit 44 and the photosensitive drum film thickness information storage unit 46 are different from those in the first embodiment. Therefore, the matters related to these will be described below.

  The photosensitive drum film shaving thickness calculation information storage unit 44 according to the second embodiment of the present invention stores the photosensitive drum film shaving thickness information table 24a described in the first embodiment as a photosensitive drum film shaving thickness information table for black. In addition, the photosensitive drum film shaving thickness information table 44e for yellow, magenta and cyan shown in FIG. 10 is stored.

  The photosensitive drum film shaving thickness information table 44e includes a photosensitive drum film thickness column 44f and a peripheral speed row 44g. The photosensitive drum film thickness column 44f is provided with a plurality of columns for specifying a predetermined photosensitive drum film thickness range. The peripheral speed line 44g is provided with a plurality of lines for specifying a predetermined peripheral speed value of the photosensitive drum.

  The columns corresponding to the column of the film thickness range specified by the photosensitive drum film thickness column 44f and the peripheral speed row specified by the peripheral speed row 44g include the per unit rotation distance of the photosensitive drum. In addition, information for specifying a coefficient A for specifying a thickness at which the photosensitive drum is scraped when yellow, magenta, or cyan toner is used is stored.

  The coefficient A when the black toner is used is specified by the photosensitive drum film scraping thickness information table 24a shown in FIG.

  FIG. 11 shows changes in coefficient A of black toner (BK) and yellow, magenta, and cyan toner (YMC) in the second embodiment.

  As can be seen from FIG. 11, the coefficient A of yellow, magenta, and cyan toner with respect to the change in film thickness of the photosensitive drum 2 is smaller than the coefficient A of black toner.

  Here, the cause of abrasion of the photosensitive drum includes friction between the developing device 5 and the photosensitive drum 2 and friction between the photosensitive drum 2 and a cleaning member (not shown). The toner adheres at the places where the respective friction occurs, and the wear of the photosensitive drum 2 is also affected by the toner.

  There are differences in the type of external additive, amount of external additive, pigment, and the like for each toner. Due to these differences, the aggressiveness to the photosensitive drum 2 changes, and the amount of wear of the photosensitive drum 2 changes. Further, due to the difference in development characteristics, the peripheral speed difference of the developing roller (not shown) with respect to the photosensitive drum may be changed for each color, and in this case, the amount of wear of the photosensitive drum 2 also appears.

  Therefore, in this embodiment, the difference in the amount of wear of the photosensitive drum 2 due to the difference in toner is reflected in the coefficient A by experiment. In this embodiment, since the black toner using a hard pigment accelerates the wear of the photosensitive drum 2, the coefficient A which is a film scraping thickness for the rotational distance 1 [m] of the photosensitive drum is larger than that of other colors. Yes.

  Returning to FIG. 9, the photosensitive drum film thickness information storage unit 46 specifies the initial value of the film thickness of the photosensitive drum 2 (the film thickness at the beginning of use of the photosensitive drum 2 or the designed film thickness of the photosensitive drum 2). Information and information for specifying the film thickness of the photosensitive drum 2K for black and the photosensitive drums 2Y, 2M, and 2C for yellow, magenta, and cyan calculated by the photosensitive drum film thickness calculation unit 50c described later are respectively stored. Is done.

  The control unit 48 includes a printing control unit 29, a film thickness calculation unit 50, a transfer correction voltage calculation unit 51, and a transfer voltage control unit 52. Compared with the first embodiment, the film thickness calculation unit 50. Since the transfer correction voltage calculation unit 51 and the transfer voltage control unit 52 are different, matters related to these will be described below.

  The film thickness calculation unit 50 calculates the film thicknesses of the photosensitive drum 2K for black and the photosensitive drums 2Y, 2M, and 2C for yellow, magenta, and cyan, respectively. For example, as shown in FIG. 12, the film thickness calculation unit 50 includes a photosensitive drum rotation distance measurement unit 30a, a photosensitive drum peripheral speed detection unit 30b, and a photosensitive drum film thickness calculation unit 50c. Since the photosensitive drum film thickness calculation unit 50c is different from the above, matters relating to the photosensitive drum film thickness calculation unit 50c will be described below.

  The photosensitive drum film thickness calculator 50c includes a black photosensitive drum film thickness information table 24a and a yellow, magenta, and cyan photosensitive drum film thickness information table stored in the photosensitive drum film thickness calculation information storage section 44. 44e, the black coefficient A corresponding to the peripheral speed of the photosensitive drum 2 and the film thickness of the photosensitive drum 2 for black and the film thickness of the photosensitive drum 2 for yellow, magenta, and cyan for each print job. The coefficient A for yellow, magenta, and cyan is acquired, and the film thickness of the photosensitive drum 2K for black for each print job, and the film abrasion of the photosensitive drums 2Y, 2M, and 2C for yellow, magenta, and cyan are obtained. The thickness is calculated by the above equation (3).

  The photosensitive drum film thickness calculator 50c calculates the film thickness of the black photosensitive drum 2K after the print job and the film thicknesses of the photosensitive drums 2Y, 2M, and 2C for yellow, magenta, and cyan (4 ) To calculate each.

  Then, the photosensitive drum film thickness calculation unit 50c uses the information specifying the film thickness of the photosensitive drum stored in the photosensitive drum film thickness information storage unit 46 as the calculated film thickness of the black photosensitive drum 2K after the print job. And information specifying the film thicknesses of the photosensitive drums 2Y, 2M, and 2C for yellow, magenta, and cyan.

  The transfer correction voltage calculation unit 51 according to the second embodiment of the present invention calculates the film thickness of the black photosensitive drum 2K calculated by the film thickness calculation unit 50, and the photosensitive drums 2Y and 2M for yellow, magenta, and cyan. The transfer correction voltage of the black transfer roller 6K and the transfer correction voltages of the yellow, magenta, and cyan transfer rollers 6Y, 6M, and 6C are calculated in accordance with the film thickness of 2C.

  The transfer voltage control unit 52 according to the second embodiment of the present invention includes the transfer correction voltage of the black transfer roller 6K calculated by the transfer correction voltage calculation unit 51, and transfer rollers 6Y for yellow, magenta, and cyan. Based on the transfer correction voltages 6M and 6C, the transfer voltage after correction of the transfer roller 6K for black calculated by the transfer correction voltage calculation unit 51, and transfer rollers 6Y, 6M for yellow, magenta, and cyan, The corrected transfer voltage of 6C is calculated and output to the transfer voltage application unit 7.

  As described above, according to the second embodiment of the present invention, the coefficient A is set for each toner color, the film thickness of the photosensitive drum 2 is calculated, and the transfer is performed according to the calculated film thickness of the photosensitive drum 2. By controlling the voltage, it is possible to apply a transfer voltage according to the change in the film thickness of each toner color, and it is possible to always obtain a good transfer result for each color toner.

Embodiment 3 FIG.
Next, a third embodiment of the present invention will be described. In the third embodiment of the present invention, since the print control device 60 is different from that in the first embodiment, items related to the print control device 60 will be described below. The third embodiment of the present invention is different from the first embodiment in that the value of the coefficient A of the film scraping thickness of the photosensitive drum 2 is the same as when the photosensitive drum 2 and the recording medium 90 are in contact with each other. The photosensitive drum 2 and the recording medium 90 are different from each other when no paper is passed.

  FIG. 13 is a schematic diagram of the print control apparatus 60 according to the third embodiment of the present invention. As shown in the figure, the printing control device 60 includes a storage unit 61, a control unit 68, and an input / output port unit 34, and the storage unit 61 and the control unit 68 are different from those in the first embodiment. Therefore, the matters related to these will be described below.

  The storage unit 61 according to the third embodiment of the present invention includes a photosensitive drum rotation distance calculation information storage unit 22, a photosensitive drum peripheral speed information storage unit 23, a photosensitive drum film scraping thickness calculation information storage unit 64, and a transfer correction voltage calculation. The information storage unit 25 and the photosensitive drum film thickness information storage unit 26 are provided, and the photosensitive drum film shaving thickness calculation information storage unit 44 is different from that of the first embodiment. Items related to the thickness calculation information storage unit 44 will be described.

  The photosensitive drum film shaving thickness calculation information storage unit 64 according to Embodiment 3 of the present invention calculates the thickness at which the film of the photosensitive drum 2 is shaved when the photosensitive drum 2 and the recording medium 90 are in contact with each other. And information necessary for calculating the thickness at which the film of the photosensitive drum 2 is scraped when the photosensitive drum 2 and the recording medium 90 are not in contact with each other are stored. . For example, in the present embodiment, the photosensitive drum film shaving thickness calculation information table 64a as shown in FIG. 14 and the photosensitive drum film shaving thickness calculation information table 64e as shown in FIG. , Is stored.

  As shown in FIG. 14, the photosensitive drum film shaving thickness calculation information table 64a at the time of paper passing includes a photosensitive drum film thickness column 64b and a peripheral speed row 64c. The photosensitive drum film thickness column 64b is provided with a plurality of columns for specifying a predetermined range of the photosensitive drum film thickness. Further, the peripheral speed row 64c is provided with a plurality of lines for specifying a predetermined peripheral speed value of the photosensitive drum.

  The columns corresponding to the column of the film thickness range specified by the film thickness column 64b of the photosensitive drum and the column of the peripheral speed specified by the peripheral speed row 64c include the units of the photosensitive drum at the time of sheet passing. Information for specifying the coefficient A1 for specifying the thickness at which the photosensitive drum is scraped per rotation distance is stored.

  As shown in FIG. 15, the photosensitive drum film shaving thickness calculation information table 64e when no paper is passed has a photosensitive drum film thickness column 64f and a peripheral speed row 64g. The photosensitive drum film thickness column 64f is provided with a plurality of columns for specifying a predetermined photosensitive drum film thickness range. The circumferential speed row 64g is provided with a plurality of rows for specifying a predetermined circumferential speed value of the photosensitive drum.

  The columns corresponding to the column of the film thickness range specified by the photosensitive drum film thickness column 64f and the peripheral speed row specified by the peripheral speed row 64g include the columns of the photosensitive drum at the time of non-sheet passing. Information for specifying the coefficient A2 for specifying the thickness at which the photosensitive drum is scraped per unit rotational distance is stored.

  Here, the difference between the coefficient A1 and the coefficient A2 that is the coefficient of film scraping thickness is different between when the sheet is passed and when the sheet is not passed, and when the photosensitive drum 2 and the recording medium 90 are in contact with each other. This is because the amount of wear of the photosensitive drum 2 differs depending on whether the drum 2 and the transfer belt 8 are in contact with each other. In general, the surface of the recording medium 90 is larger than that of the transfer belt 8, so that the amount of wear of the photosensitive drum 2 is larger when the sheet is passed. Therefore, the coefficient A1 and the coefficient A2 are set in a form that reflects the difference in film scraping amount between when paper is passed and when paper is not passed (the coefficient A2 is made equal to or less than the coefficient A1 as long as other conditions are equal). ). Each value is obtained experimentally and set.

  Returning to FIG. 13, the control unit 68 includes a print control unit 29, a film thickness calculation unit 70, a transfer correction voltage calculation unit 31, and a transfer voltage control unit 32, and compared with the first embodiment, Since the film thickness calculation unit 70 is different, items related to the film thickness calculation unit 70 will be described below.

  The film thickness calculator 70 calculates the film thickness of the photosensitive drum 2 based on the film thickness of the photosensitive drum 2 when the paper is passed and the film thickness of the photosensitive drum 2 when the paper is not passed. For example, as shown in FIG. 16, the film thickness calculation unit 70 includes a photosensitive drum rotation distance measurement unit 70a, a photosensitive drum peripheral speed detection unit 30b, and a photosensitive drum film thickness calculation unit 70c. Since the photosensitive drum rotation distance measurement unit 70a and the photosensitive drum film thickness calculation unit 70c are different from each other, matters relating to these will be described below.

  The photosensitive drum rotation distance measuring unit 70a measures the rotation distance L of the photosensitive drum 2 for each print job, as in the first embodiment.

  In addition, the photosensitive drum rotation distance measuring unit 70a according to the present embodiment acquires information on the length M of the recording medium 90 in the transport direction and the number N of surfaces to be printed. For example, the photosensitive drum rotation distance measuring unit 70a obtains the detection result of the leading position and the trailing edge position of the recording medium 90 from the writing sensor 16 or the discharge sensor 17, so that the length M and the conveying direction of the recording medium 90 are determined. Information specifying the number N of pages to be printed can be acquired.

Then, the photosensitive drum rotation distance measuring unit 70a sets the rotation distance Lp of the photosensitive drum 2 when paper is passed and the rotation distance Ln of the photosensitive drum 2 when paper is not passed, respectively, by the following equations (5) and (6). Calculate using the formula.
Lp = M × N [m] (5)
Ln = L−Lp [m] (6)

  The photosensitive drum film thickness calculation unit 70c is a film scraped from the photosensitive drum 2 for each print job based on the rotation distance when the photosensitive drum 2 is passed, the rotation distance when the photosensitive drum 2 is not passed, and the peripheral speed of the photosensitive drum 2. The thickness is calculated, and the film thickness of the photosensitive drum 2 after the print job is calculated by subtracting the film thickness scraped by the print job from the film thickness of the photosensitive drum 2 before the start of the print job.

  For example, the photosensitive drum film thickness calculation unit 70c includes the value of the peripheral speed V of the photosensitive drum 2 during printing, the current film thickness T of the photosensitive drum 2 stored in the photosensitive drum film thickness information storage unit 26, and The coefficient A1 and the coefficient A2 which are coefficients of film thickness corresponding to the above are respectively the photosensitive drum film shaving thickness calculation information table 64a (see FIG. 14) when passing paper and the photosensitive drum film shaving thickness calculation information table when not passing paper. 64e (FIG. 15).

Then, the photosensitive drum film thickness calculation unit 70c obtains the film shaving thickness Tip when passing paper and the film shaving thickness Tin when not passing paper, using the following formulas (7) and (8).
Tip = Lp × A1 [μm] (7)
Tin = Ln × B2 [μm] (8)

Further, the photosensitive drum film thickness calculating unit 70c calculates the film thickness T1 after the print job from the film thickness Thick at the time of paper passing and the film thickness Thin at the time of non-paper passing by the following equation (9). Use to calculate.
T1 = Tip + Tin [μm] (9)

  Then, the photosensitive drum film thickness calculation unit 70c uses the film scraping thickness T1 and the film thickness T of the photosensitive drum 2 before the print job to calculate the above equation (4) as in the first embodiment. Used to calculate the film thickness Tt of the photosensitive drum 2 after the print job.

  Furthermore, the photosensitive drum film thickness calculation unit 70c specifies the film thickness of the photosensitive drum 2 after the calculated print job using the information for specifying the film thickness of the photosensitive drum 2 stored in the photosensitive drum film thickness information storage unit 26. Update to the information you want.

  As described above, in the present embodiment, the film thickness of the photosensitive drum 2 is calculated by setting the coefficient of the film shaving thickness of the photosensitive drum 2 when the paper is passed and when the paper is not passed. In addition, it is possible to apply a post-correction transfer voltage in accordance with the change in the film thickness of the photosensitive drum 2, and a good transfer result can be obtained.

By the way, some image forming apparatuses are set so that wear is more likely to occur by changing the peripheral speed of the photosensitive drum and the peripheral speed of the recording medium.

  In the case of such an image forming apparatus, as shown in FIG. 17, a peripheral speed storing a coefficient A3 having a value larger than the coefficient A1 at the time of sheet passing in FIG. The photosensitive drum film shaving thickness calculation information table 64 i for difference is stored in the photosensitive drum film shaving thickness information storage unit 64.

  In this way, when there is a peripheral speed difference between the photosensitive drum and the recording medium during paper feeding, the coefficient of film thickness of the photosensitive drum is set to a larger value than when there is no peripheral speed difference. By accurately calculating the film thickness of the photosensitive drum and controlling the transfer voltage according to the calculated film thickness of the photosensitive drum, it is possible to apply a transfer voltage according to the change in the film thickness, which is better It is also possible to obtain a transcription result.

  Also in the third embodiment, as in the second embodiment, at least one of the values of the coefficient A1 and the coefficient A2 can be made different depending on the color of the toner.

Modifications of Embodiments 1 to 3 In the embodiment described above, the image forming apparatus 1 that performs color printing has been described. However, the present invention can be similarly applied to an image forming apparatus that performs monochrome printing. Therefore, for example, the present invention can be applied to MFPs, facsimiles, and copiers as long as the apparatus has a configuration in which a developer is developed and transferred by an electric field using a photosensitive drum.

  The number of colors is not limited, and the present invention can be applied to a single color image forming apparatus or a plurality of color image forming apparatuses.

  In the first and third embodiments, the corrected voltage may be obtained for any one color, or black and any other one, and applied to the transfer rollers for other colors. In 2, the corrected voltage for black and any one color may be obtained, and the corrected voltage calculated for any one color may be applied to the transfer rollers for other colors.

  For example, when the rotational distances of the photosensitive drums 2 of all colors or a plurality of colors are the same (a rotational distance within a specific range), the photosensitive drums 2 have the same rotational distance (including almost the same case). It is also possible to calculate a corrected voltage for any of the photosensitive drums 2 and divert it to the photosensitive drums 2 of other colors.

1: image forming apparatus, 2: photosensitive drum, 3: charger, 4: exposure device, 5: developing device, 6: transfer roller, 7: transfer voltage application unit, 8: transfer belt, 9: drive roller, 10: Idle roller, 11: Fixing device, 12: First transport roller, 13: Second transport roller, 14: Discharge roller, 15: Hopping roller, 16: Write sensor, 17: Discharge sensor, 18: Support plate member, 19: Spring, 20, 40, 60: Print control device, 21, 41, 61: Storage unit, 22: Photosensitive drum rotation distance calculation information storage unit, 23: Photosensitive drum peripheral speed information storage unit, 24, 44, 64: Photosensitive drum Film thickness calculation information storage unit 25: Transfer correction voltage calculation information storage unit 26, 46: Photosensitive drum film thickness information storage unit 28, 48, 68: Control unit 29: Print control unit 30, 50, 70 :film Calculation unit, 30a, 70a: photosensitive drum rotation distance measurement unit, 30b: photosensitive drum peripheral speed detection unit, 30c, 50c, 70c: photosensitive drum film thickness calculation unit, 31, 51: transfer correction voltage calculation unit, 32, 52: Transfer voltage control unit 34: input / output port unit.

Claims (17)

An image carrier having a film carrying a developer;
A transfer means for applying a voltage and transferring the developer developed on the image carrier to a recording medium;
A film thickness calculating means for calculating the thickness of the film;
A transfer correction voltage calculation means for calculating a correction value of a voltage applied to the transfer means based on the thickness of the film calculated by the film thickness calculation means;
An image forming apparatus comprising: a transfer voltage control unit that applies a corrected voltage corrected with the calculated correction value to the transfer unit. The transfer correction voltage calculation means includes:
The image forming apparatus according to claim 1, wherein the correction value of the voltage applied to the transfer unit is increased as the thickness of the film calculated by the film thickness calculation unit is smaller. The transfer correction voltage calculation means includes:
By subtracting the thickness of the film calculated by the film thickness calculation means from the initial value of the thickness of the film, the cumulative film scraping thickness of the film is calculated, and the calculated cumulative film scraping thickness is corresponding to the calculated cumulative film scraping thickness. The image forming apparatus according to claim 1, wherein a correction value of a voltage applied to the transfer unit is calculated. The transfer voltage control means includes
The image forming apparatus according to claim 3, wherein the voltage applied to the transfer unit is increased as the cumulative film scraping thickness is increased. Film thickness information storage means for storing information for specifying the thickness of the film at a specific point in time,
The film thickness calculating means includes
Distance measuring means for measuring the rotational distance of rotation of the image carrier;
Calculate the film thickness of the film from the measured rotational distance, and subtract the calculated film thickness from the thickness of the film at a specific point in time to calculate the film thickness. The image forming apparatus according to claim 1, wherein the image forming apparatus includes: The film thickness calculating means includes
When the thickness of the film is calculated, the thickness at a specific time point of the film stored in the film thickness information storage unit is updated with the calculated thickness of the film. The image forming apparatus described. A film shaving thickness calculation information storage means for storing a first coefficient for specifying the film shaving thickness per unit rotational distance of the image carrier;
7. The image forming apparatus according to claim 5, wherein the film thickness calculating unit calculates a film thickness of the film by multiplying the first coefficient by the rotation distance. The first coefficient is stored in the film shaving thickness calculation information storage means, which differs depending on the thickness of the film at a specific point in time and the peripheral speed of the image carrier.
The film thickness calculating means includes
A peripheral speed detecting means for acquiring a peripheral speed of the image carrier;
The film thickness calculation means calculates the first coefficient corresponding to the thickness at a specific time point of the film stored in the film thickness information storage means and the acquired peripheral speed, as the film scraping thickness. The image forming apparatus according to claim 7, wherein the image forming apparatus is obtained from a calculation information storage unit. The image forming apparatus according to claim 8, wherein the first coefficient decreases as the thickness of the film at a specific time increases. The image forming apparatus according to claim 8, wherein the first coefficient increases as the peripheral speed increases. The first coefficient has a different value stored in the film thickness calculation information storage means depending on the color of the developer carried by the image carrier,
The film thickness calculation means obtains the first coefficient from the film thickness calculation information storage means for each color of the developer, and calculates the thickness of the film,
The image forming apparatus according to claim 7, wherein the transfer voltage control unit controls a voltage applied to the transfer unit for each color of the developer. The first coefficient has a value that is different between when the image carrier and the recording medium are in contact with each other and when the image carrier and the recording medium are not in contact with each other. Stored in the information storage means,
The distance measuring means measures a rotation distance when the image carrier rotates when the paper is passed and a rotation distance when the image carrier rotates when the image carrier is not passed,
The film thickness calculating means is configured to multiply the first coefficient at the time of passing the paper by the rotation distance at the time of passing the paper and the first thickness at the time of non-passing the paper. Calculating the film shaving thickness by adding the non-paper passing film thickness calculated by multiplying the coefficient by the non-paper passing rotation distance to calculate the film thickness. The image forming apparatus according to claim 7, wherein the image forming apparatus is an image forming apparatus. The first coefficient has a different value when there is no speed difference between the image carrier and the recording medium and when there is a speed difference between the image carrier and the recording medium. Stored in the storage means,
The distance measuring unit measures a first rotation distance in which the image carrier rotates when there is no speed difference and a second rotation distance in which the image carrier rotates when there is the speed difference. And
The film thickness calculating means calculates the first film shaving thickness calculated by multiplying the first rotation distance by the first coefficient when there is no speed difference and the speed when there is the speed difference. Adding the second film scraping thickness calculated by multiplying the first coefficient by the second rotational distance to calculate the film scraping thickness and calculating the thickness of the film The image forming apparatus according to claim 7, wherein the image forming apparatus is an image forming apparatus. A transfer correction voltage calculation information storage unit for storing a second coefficient for specifying a correction voltage per predetermined unit of the cumulative film thickness;
5. The image forming apparatus according to claim 3, wherein the transfer correction voltage calculation unit calculates the correction value by multiplying the second film coefficient by the cumulative film scraping thickness. The second coefficient is stored in the transfer correction voltage calculation information storage unit as a different value depending on the peripheral speed of the image carrier.
The film thickness calculating means includes a peripheral speed detecting means for acquiring a peripheral speed of the image carrier,
The image forming apparatus according to claim 14, wherein the transfer correction voltage calculation unit acquires the second coefficient corresponding to the acquired peripheral speed from the transfer correction voltage calculation information storage unit. The second coefficient has a different value stored in the transfer correction voltage calculation information storage means depending on the printing surface of the recording medium,
The image forming apparatus according to claim 14, wherein the transfer correction voltage calculation unit acquires the second coefficient corresponding to the printing surface of the recording medium from the transfer correction voltage calculation information storage unit. An image carrier having a film carrying a developer;
A voltage correction method performed by an image forming apparatus having a voltage applied and a transfer unit that transfers a developer developed on the image carrier to a recording medium,
A process of calculating a thickness of the film by a film thickness calculating means;
A step of calculating a correction value of a voltage applied to the transfer unit based on the thickness of the film calculated by the film thickness calculation unit;
And a step of applying a corrected voltage corrected by the calculated correction value to the transfer unit.

Images