JP2022112778A - Image forming apparatus, image forming method, and image forming program - Google Patents

Abstract

To provide an image forming apparatus that can prevent a deterioration in transfer performance caused by variations during manufacture and a change over time in the resistance of a transfer unit and can prevent a reduction in productivity.SOLUTION: An image forming apparatus has: a transfer unit that transfers a toner image formed on an image carrier to a transfer target body with a constant voltage-controlled transfer voltage; and a control unit that performs determination processing of determining a transfer voltage for generating a predetermined transfer current, and corrects the transfer voltage based on the correction rate of a fluctuation factor that fluctuates the transfer current generated from the transfer voltage, the correction rate according to the amount of change from the time of the determination processing.SELECTED DRAWING: Figure 8

Description

The present invention relates to an image forming apparatus, an image forming method, and an image forming program.

In an electrophotographic image forming apparatus, for example, an electrostatic latent image formed by exposing a charged photoreceptor is developed with toner to form a toner image on the surface of the photoreceptor, and the toner image is transferred to an intermediate transfer member. , and then transferred from the intermediate transfer member to the paper. After that, the image is formed on the paper by performing a fixing process of heating and pressurizing the toner image on the paper.

2. Description of the Related Art In a transfer process for transferring a toner image from a photoreceptor to an intermediate transfer member, the toner image can be transferred by current generated by applying a constant-voltage controlled voltage to a transfer portion such as a transfer roller. In the transfer process based on constant voltage control, a constant transfer rate can be obtained even when the toner adhesion amount in the main scanning direction is different. The voltage for constant voltage control is determined by ATVC (Active Transfer Voltage Control). ATVC is a process of determining a transfer voltage by reading a voltage value when a predetermined constant current-controlled current is applied to the transfer section.

ATVC is usually performed at the start of image formation, but as image formation continues, the temperature and humidity inside the image forming apparatus change due to heat from the fixing device and changes in the external environment. Resistance fluctuates. As a result, the current applied to the toner decreases due to the constant voltage applied to the transfer portion by the constant voltage control, the transfer rate decreases, and problems such as poor color tone may occur. Conventionally, as a countermeasure against this, after the image formation is started, when the image is not formed such as between sheets, the ATVC is performed again, the applied voltage is corrected, and the constant voltage-controlled voltage applied to the transfer section is changed. It maintains the current applied to the toner.

However, if the ATVC or the like is performed during non-image formation, such as between sheets of paper, the transfer member or the like needs to be rotated more than once, resulting in a decrease in productivity.

Patent Document 1 listed below discloses the following prior art. A correction formula for correcting the voltage drop in the transfer roller during ATVC before image formation to the voltage drop during image formation based on the temperature change during image formation is registered in advance for each humidity level. When the humidity level during image formation is the same as that during ATVC, an applied voltage corresponding to the corrected voltage drop calculated using the above correction formula is applied to the transfer roller under constant voltage control to carry out the transfer process. If the humidity level during image formation is different from that during ATVC execution, ATVC is executed again and the transfer process is executed with the determined applied voltage. As a result, the electrostatic force in the transfer process by constant voltage control can be properly maintained while suppressing a decrease in productivity.

JP 2007-183309 A

However, the transfer member used in the transfer section has resistance variations due to lot differences, deterioration due to durability, adhesion of discharge products due to corona discharge during charging and post-transfer static elimination, and increased lubricity in the cleaning section. A change in resistance also occurs due to the adhesion of a lubricant for this purpose. The above-described prior art has a problem that it is impossible to prevent the deterioration of the transfer rate due to such a change in resistance. Further, in the prior art described above, when the absolute humidity changes relatively greatly and the humidity level at the time of image formation becomes different from that at the time of ATVC, ATVC is performed again. However, there is also a problem that the productivity is lowered by performing the ATVC again, and that it is impossible to cope with the case where the non-image forming time is not provided, such as the case where the image is formed on the continuous paper.

The present invention has been made to solve such problems. That is, it is an object of the present invention to provide an image forming apparatus, an image forming method, and an image forming program capable of suppressing deterioration of transfer performance caused by manufacturing variations and temporal fluctuations in the resistance of the transfer portion and preventing a decrease in productivity. and

The above problems of the present invention are solved by the following means.

(1) Determination processing is performed to determine a transfer section for transferring a toner image formed on an image bearing member to a transfer material with a constant-voltage-controlled transfer voltage, and the transfer voltage for generating a predetermined transfer current. and a control unit that corrects the transfer voltage based on a correction ratio according to the amount of change from the time of the determination process of the fluctuation factor that causes the transfer current to fluctuate due to the transfer voltage.

(2) The control unit corrects the transfer voltage by correcting, with the correction ratio, a variable portion of the determined transfer voltage excluding a constant portion that does not change due to the variable factor, thereby correcting the transfer voltage. The image forming apparatus according to .

(3) The image forming apparatus according to (2), wherein the variation factor is temperature, and the control section corrects the variation portion based on a temperature change rate.

(4) The image forming apparatus according to (2), wherein the variable factor is relative humidity, and the control unit corrects the variable part based on a rate of change in relative humidity.

(5) The image forming apparatus according to (2), wherein the variable factor is absolute humidity, and the control section corrects the variable portion based on a change rate of absolute humidity.

(6) The image forming apparatus according to (2), wherein the control unit calculates the transfer voltage determined by performing the determination process when the temperature reaches or exceeds a predetermined threshold as the constant portion. .

(7) The image forming apparatus according to (2), wherein the control unit calculates the transfer voltage determined by performing the determination process after image formation by a print job is completed as the constant portion.

(8) The image forming apparatus according to (7), wherein the print job includes double-sided printing.

(9) The control unit determines the transfer voltage by the determination process under a plurality of conditions in which the resistance of the path through which the transfer current flows is set, and determines the constant portion based on the determined transfer voltage. The image forming apparatus according to (2) above, which calculates .

(10) The image forming apparatus according to (2) above, wherein the control section changes the invariant portion when an influencing factor different from the variable factor that affects the invariant portion changes.

(11) The image forming apparatus according to (10), wherein the influencing factor is temperature, and the control unit calculates the constant portion based on the temperature.

(12) The image forming apparatus according to (10), wherein the influencing factor is relative humidity, and the control section calculates the constant portion based on the relative humidity.

(13) The image forming apparatus according to (10), wherein the influencing factor is absolute humidity, and the control section calculates the constant portion based on the absolute humidity.

(14) A step (a) of transferring the toner image formed on the image carrier onto the transfer material with a constant voltage-controlled transfer voltage, and a determination process of determining the transfer voltage for generating a predetermined transfer current. is performed, and the toner image is transferred in step (a) based on the rate of change according to the amount of change from the time of the determination process of the fluctuation factors that fluctuate the transfer current caused by the determined transfer voltage. and (b) correcting the transfer voltage to be transferred onto a transfer-receiving material.

(15) Procedure (a) for transferring the toner image formed on the image bearing member to the transferred member at a constant voltage-controlled transfer voltage, and determination processing for determining the transfer voltage for generating a predetermined transfer current. is performed, and the toner image is transferred in the step (a) based on the rate of change according to the amount of change from the time of the determination process of the fluctuation factor that fluctuates the transfer current caused by the determined transfer voltage. An image forming program for causing a computer to execute a step (b) of correcting the transfer voltage to be transferred to the transferred material.

A determination process is performed to determine a constant-voltage-controlled transfer voltage that generates a predetermined transfer current for transferring the toner image formed on the image carrier to the transfer material, and the transfer current generated by the transfer voltage is varied. The transfer voltage is corrected based on the correction ratio corresponding to the amount of change from the time of the determination process of the variation factor that causes the transfer voltage. As a result, it is possible to suppress the deterioration of the transfer performance due to manufacturing variations and temporal fluctuations in the resistance of the transfer portion, and prevent a decrease in productivity.

1 is a schematic diagram showing the configuration of an image forming apparatus; FIG. 1 is a block diagram showing the configuration of an image forming apparatus; FIG. 3 is an explanatory diagram showing the configuration of a circuit that applies a transfer voltage to a primary transfer roller; FIG. 7 is a graph for explaining correction of transfer voltage; 7 is a graph of an approximation formula of the relationship between the amount of change in temperature and the transfer voltage under different resistance conditions; 4 is a graph of an approximation formula for the relationship between the amount of change in temperature and the rate of change in the fluctuating portion; FIG. 10 is a graph for explaining immutable part update processing; FIG. 4 is a flow chart showing the operation of the image forming apparatus; It is a graph for demonstrating a prior art. 7 is a graph for explaining calculation of a corrected transfer voltage;

An image forming apparatus according to an embodiment of the present invention will be described below with reference to the drawings. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. Also, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may differ from the actual ratios.

(First embodiment)
FIG. 1 is a schematic diagram showing the configuration of an image forming apparatus 100. As shown in FIG. FIG. 2 is a block diagram showing the configuration of the image forming apparatus 100. As shown in FIG.

Image forming apparatus 100 includes control unit 110 , storage unit 120 , communication unit 130 , operation display unit 140 , image reading unit 150 , image control unit 160 , image forming unit 170 and sensor 180 . These components are communicatively coupled to each other by bus 190 . Image forming apparatus 100 may be configured by an MFP (MultiFunction Peripheral). Control unit 110, storage unit 120, and operation display unit 140 constitute a computer.

The control unit 110 includes a CPU (Central Processing Unit) and various memories, and performs control of the above units and various arithmetic processing according to programs. Details of the action of the control unit 110 will be described later.

Storage unit 120 is configured by an SDD (Solid State Drive), HDD (Hard Disc Drive), or the like, and stores various programs and various data.

The communication unit 130 is an interface for communicating between the image forming apparatus 100 and external devices. As the communication unit 130, a network interface conforming to standards such as Ethernet (registered trademark), SATA, and IEEE1394 is used. As the communication unit 130, various local connection interfaces such as wireless communication interfaces such as Bluetooth (registered trademark) and IEEE802.11 are used.

The operation display unit 140 includes a touch panel, numeric keys, a start button, a stop button, etc., and is used to display various information and input various instructions.

The image reading unit 150 has a light source such as a fluorescent lamp and an imaging device such as a CCD (Charge Coupled Device) image sensor. The image reading unit 150 applies light from a light source to a document set at a predetermined reading position, photoelectrically converts the reflected light with an imaging device, and generates image data from the electrical signal.

The image control unit 160 performs layout processing and rasterization processing of print data included in a print job or the like received by the communication unit 130 to generate image data in bitmap format.

A print job is a general term for print commands to the image forming apparatus 100, and includes print data and print settings. The print data is data of a document to be printed, and may include various data such as image data, vector data, and text data. Specifically, the print data can be PDL (Page Description Language) data, PDF (Portable Document Format) data, or TIFF (Tagged Image File Format) data. The print settings are settings related to image formation on the paper 900, and include, for example, various settings such as the number of pages, the number of copies to be printed, the type of paper, selection of color or monochrome, and page layout.

Image forming section 170 includes image forming section 40 , fixing section 50 , paper feeding section 60 , and paper conveying section 70 .

The image forming section 40 has image forming units 41Y, 41M, 41C, and 41K corresponding to Y (yellow), M (magenta), C (cyan), and K (black) toners. The image forming units 41Y, 41M, 41C, and 41K form a toner image on the photosensitive drum 42 based on the image data through processes of charging, exposure, and development. Exposure is performed by scanning the photosensitive drum 42 with a laser beam. The toner images formed on the photoreceptor drum 42 are sequentially superimposed and primarily transferred onto the intermediate transfer belt 43 by the electrostatic force generated by the constant-voltage-controlled transfer voltage applied to the primary transfer roller 44 . . As a result, a color toner image is held on the intermediate transfer belt 43 . The color toner image on the intermediate transfer belt 43 is secondarily transferred onto the paper 900 by the secondary transfer roller 45 . The primary transfer roller 44 constitutes a transfer section.

The intermediate transfer belt 43 has a volume resistivity of about 1.0×10 ⁷ to 1.0×10 ⁹ Ω·cm and a surface resistivity of about 1.0×10 ¹⁰ to 1.0×10 ¹² Ω/□. A semi-conductive endless (seamless) resin belt is used. As the resin belt, a semi-conductive belt with a thickness of 0.05 to 0.5 mm is made by dispersing a conductive material in engineering plastics such as modified polyimide, thermosetting polyimide, ethylenetetrafluoroethylene copolymer, polyvinylidene fluoride, and nylon alloy. A resin film can be used. As the intermediate transfer belt 43, a semi-conductive rubber belt having a thickness of 0.5 to 2.0 mm and having a conductive material dispersed in silicone rubber or urethane rubber can also be used. The intermediate transfer belt 43 is wound by a plurality of roller members including a tension roller 36 and supported so as to be rotatable in the vertical direction.

The primary transfer roller 44 is composed of, for example, a metal shaft and a roller-shaped conductive member using foamed rubber such as silicone or urethane covering the shaft. They are provided facing each other and press the back surface of the intermediate transfer belt 43 to form a transfer area with the photosensitive drum 42 . A transfer voltage having a polarity opposite to that of the toner is applied to the primary transfer roller 44 by constant voltage control, and the toner image on the photosensitive drum 42 is transferred onto the intermediate transfer belt 43 by the electrostatic force of the transfer electric field formed in the transfer area. be transcribed.

The photoreceptor drum 42 is an image carrier having a hollow cylindrical main body (substrate) and a photosensitive layer, and is configured to rotate at a predetermined speed. The main body (substrate) is made of metal such as aluminum, for example. The photosensitive layer is made of, for example, a resin such as polycarbonate containing an organic photo conductor (OPC).

FIG. 3 is an explanatory diagram showing the configuration of a circuit that applies a transfer voltage to the primary transfer roller 44. As shown in FIG.

A transfer voltage is applied to the primary transfer roller 44 by a power supply 441 . When the photosensitive drum 42 pressed against the primary transfer roller 44 via the intermediate transfer belt 43 is grounded, the transfer voltage becomes a voltage using the potential of the photosensitive drum 42 as a reference potential (ground potential). The power supply 441 outputs a transfer voltage based on the control signal VIN that is output from the control section 110 and input to the power supply 441 . Specifically, the power supply 441 outputs a transfer voltage based on an analog signal obtained by converting the control signal VIN by the D/A converter 442 . The power supply 441 operates as a constant voltage source and outputs a constant voltage controlled transfer voltage.

The power supply 441 can also operate as a constant current source and can be used to determine the transfer voltage by ATVC (Active Transfer Voltage Control). Specifically, the voltage (potential) of the primary transfer roller 44 when a constant current is output from the power supply 441 is detected by the voltage detection circuit 443, converted into a digital signal VOUT by the A/D converter 444, and 110. Accordingly, the control unit 110 can determine the transfer voltage (hereinafter also simply referred to as “transfer voltage”) that needs to be applied to the primary transfer roller 44 in order to generate a predetermined transfer current. The predetermined transfer current can be appropriately set through experiments from the viewpoint of the quality of the image formed on the paper 900 .

The fixing unit 50 includes a fixing roller 51a and a pressure roller 52, and the fixing roller 51a and the pressure roller 52 are pressed against each other to form a fixing nip between the fixing roller 51a and the pressure roller 52. . The fixing unit 50 heats and presses the paper 900 conveyed to the fixing nip at the fixing nip and rotates the fixing roller 51 a and the pressure roller 52 , thereby transferring the toner image on the paper 900 to the surface of the paper 900 . Melt and fix.

Sensors 180 may include thermometers and hygrometers. The sensor 180 is arranged inside the image forming apparatus 100, for example, at a position relatively close to the imaging unit 40, and measures the temperature and humidity inside the apparatus. Sensors 180 may measure temperature and humidity outside the aircraft. In this case, the temperature and humidity are measured within a predetermined distance from the image forming apparatus 100 . The predetermined distance can be appropriately set through experiments from the viewpoint of the quality of the image formed on the paper 900 . Humidity may be relative humidity or absolute humidity.

The action of the control unit 110 will be described.

The control unit 110 performs determination processing (hereinafter also simply referred to as “determination processing”) for determining the transfer voltage by ATVC. Hereinafter, the transfer voltage determined by the determination process will be referred to as "ATVC determined value". The ATVC determination value is determined before execution of the print job, and is applied as a transfer voltage when image formation is performed by execution of the print job. The ATVC decision value is preferably determined just prior to execution of the print job.

The control unit 110 sets a correction ratio (hereinafter simply referred to as "correction ratio") according to the amount of change from the time of the determination process of the variation factor that causes the transfer current to fluctuate due to the application of the ATVC determination value to the primary transfer roller 44. ) corrects the transfer voltage. The correction ratio will be described later. Variables include temperature, relative humidity, and absolute humidity. Specifically, these can be the temperature, relative humidity, and absolute humidity inside the image forming apparatus 100 . For the sake of simplicity, the following description assumes that the variation factor is temperature.

FIG. 4 is a graph for explaining correction of the transfer voltage. The horizontal axis of the graph is the amount of change in temperature, and the vertical axis is the transfer voltage. Specifically, the amount of change in temperature is calculated by subtracting the temperature at the time of determination processing (during determination processing before starting a print job) from the current temperature. The amount of change in current temperature is indicated by a dashed line on the graph.

As shown in FIG. 4, the transfer voltage varies with temperature. The reason why the transfer voltage changes is that the resistance of the path through which the transfer current flows (hereinafter also simply referred to as "resistance") changes due to temperature or the like. The path through which the transfer current flows is considered to be the path from the primary transfer roller 44 to the ground point via the intermediate transfer belt 43 and the photosensitive drum 42 . The transfer voltage is divided into a variable portion that changes with temperature and an invariant portion that does not change with temperature. Note that there may be cases where there is no invariant part.

The control unit 110 corrects the transfer voltage by correcting the changing portion of the ATVC determination value, excluding the unchanged portion, based on the correction ratio according to the amount of temperature change from the time of the determination process. The corrected transfer voltage is hereinafter referred to as "corrected transfer voltage". The correction ratio is given by the following formula.

Correction rate [%] = A x e ^ (B x (current temperature [°C] - temperature at the time of decision processing [°C]))
Here, the current temperature [°C] - the temperature [°C] at the time of determination processing is the amount of temperature change. A and B are coefficients, which are determined by calculating an approximation from a graph of the relationship between the actual measurement value of the ATVC transfer voltage for each temperature change amount and the temperature change amount, as will be described later.

The variable part is the ATVC determined value minus the constant part, and is given by the following equation.

Variable part [V] = ATVC determined value [V] - Invariant part [V]
As will be described later, for example, under two conditions with different resistances, the transfer voltage is actually measured by an ATVC for each temperature, and two approximations are calculated from graphs of the relationship between the measured values and the amount of temperature change. It can be calculated as the voltage at the intersection of the equations. Calculation of such variable portions may be performed experimentally prior to the start of image formation by the print job.

The post-correction transfer voltage is calculated, for example, by multiplying the fluctuation portion by the correction ratio to calculate the fluctuation portion correction value and adding it to the unchanged portion, as in the following equation. Note that there may be cases where there is no invariant part.

Fluctuation part correction value [V] = Fluctuation part [V] × Correction rate [%]
Transfer voltage after correction [V]=Invariant portion [V]+Variable portion correction value [V]
In this way, the transfer voltage is divided into a variable portion and a constant portion, and only the variable portion is corrected by a correction ratio based on the amount of temperature change. It is possible to flexibly suppress deterioration of transfer performance due to factors.

FIG. 5 is a graph of an approximate expression of the relationship between temperature and transfer voltage under different resistance conditions. The horizontal axis of the graph is temperature, and the vertical axis is transfer voltage. The circle and triangle plots on the graph are actual measurement results of the transfer voltage measured by ATVC for each temperature that changes during image formation. Circle plots are the results of actual measurement under high resistance conditions, and triangular plots are the results of actual measurement under low resistance conditions. The conditions of high resistance and low resistance can be realized by changing the type of the primary transfer roller 44 respectively. High resistance and low resistance conditions may be achieved, such as by using relatively worn rollers and new rollers.

In the example of FIG. 5, the approximate expression of the relationship between temperature (x) and transfer voltage (y) under high resistance conditions is y=11815e^(-0.075x). The approximation formula for low resistance conditions is y=5104e^(-0.057x). The intersection of the two approximations corresponds to the invariant portion, which is 358V.

FIG. 6 is a graph of an approximation formula for the relationship between the amount of change in temperature and the rate of change in the fluctuating portion. The horizontal axis of the graph represents the amount of change in temperature, which can be a value obtained by calculating the amount of change from the temperature at the start of image formation. The vertical axis is the rate of change of the variable portion.

An approximation formula for the relationship between the amount of change in temperature and the rate of change in the fluctuating portion is calculated as follows. Assuming that the transfer voltage (equivalent to the ATVC determined value) measured by the ATVC at the start of image formation is 100% and the unchanged portion is 0%, the transfer voltage actually measured by the ATVC for each temperature is normalized to calculate the change rate of the variable portion. do. The variable portion change rate corresponds to the correction rate described above. In the example of FIG. 5, the transfer voltage measured by the ATVC at the start of image formation under the condition of high resistance is 4807V. The measured value of the transfer voltage by ATVC at the start of image formation under the condition of low resistance is 2800V. The constant part is 358V. The normalized transfer voltage can be used to calculate an approximation expression of the relationship between the amount of change in temperature and the rate of change of the change portion without distinguishing between the calculation results under the high resistance condition and the low resistance condition. In the example of FIG. 6, the coefficient A is 0.9806 and the coefficient B is -0.075. Therefore, the approximation formula for the relationship between the amount of change in temperature and the rate of change in the variable portion (correction rate) is: rate of change in the variable portion (correction rate) = 0.9806 x e ^ (-0.075 x amount of change in temperature) .

Specifically, the control unit 110 corrects the transfer voltage using a correction ratio according to the amount of change in temperature as follows, applies the corrected transfer voltage to the primary transfer roller 44 , and transfers the voltage onto the photosensitive drum 42 . is primarily transferred onto the intermediate transfer belt 43 . Control unit 110 determines the ATVC determination value by the determination process at the start of image formation. As image formation continues, the temperature inside the apparatus rises due to, for example, the temperature of the fixing section 50 . Therefore, the transfer voltage is corrected at a predetermined frequency with a correction ratio corresponding to the amount of change in temperature from the time of the determination process. For example, when the temperature is corrected every time the temperature rises by 5° C., the correction ratio (fluctuation partial change rate) is 0.9806×e^(−0.075 × 5V) = 67.4%. If the ATVC determined value is 3000V, then the constant part is 358V, so the variable part is 3000V-358V=2642V. The fluctuation portion correction value is 2642V×67.4%=1781V. Therefore, the corrected transfer voltage is 1781V+358V=2139V. By continuously correcting the transfer voltage in this way, the optimum transfer voltage can be maintained.

When the condition for updating the invariant portion is satisfied, the control unit 110 performs the determination process again, and performs processing for updating the invariant portion by calculating the determined ATVC decision value as the invariant portion (hereinafter referred to as “invariant portion update processing”). ) can be implemented. The condition for updating the invariant portion is, for example, when image formation for all pages is completed by execution of a print job.

FIG. 7 is a graph for explaining the unchanged part update process. The horizontal axis of the graph in FIG. 7 is the amount of change in temperature, and the vertical axis is the transfer voltage.

As shown in FIG. 7, image formation (primary transfer) is started using the ATVC decision value (black dot) determined by the determination process before image formation by the print job as the transfer voltage, and the image is formed while correcting the transfer voltage. Formation is performed, and image formation is completed. Since the ATVC determination value (white circle point) determined in the determination process at the end of image formation substantially corresponds to the unchanged portion, the unchanged portion update processing for updating the unchanged portion with the ATVC determination value is possible. This is because the temperature inside the image forming apparatus 100 is sufficiently high when the image formation by the print job is completed, and even if the ATVC determination value is determined by the determination processing after the temperature is further increased, the same ATVC determination value is determined. This is because it is assumed that the transfer voltage required to generate a given transfer current does not change. In addition, the invariant portion update process is performed for the wear of members such as the primary transfer roller 44, the adhesion of discharge products due to corona discharge during electrification and post-transfer static elimination, and the use of a lubricant to increase the lubricity of the cleaning portion. This is because the resistance may have changed due to adhesion or the like. A decrease in productivity can be prevented by executing the determination process when image formation by a print job is completed.

The condition for updating the invariant portion may be that image formation of all pages is completed by execution of the print job and that the temperature is equal to or higher than a predetermined threshold. The predetermined threshold may be an empirically estimated temperature at which further increases in temperature will not change the ATVC decision value. The predetermined threshold value may be an empirical value obtained by experimentally measuring the minimum temperature at which a further increase in temperature does not change the determined ATVC value. The condition for updating the invariant portion may be completion of image formation by a double-sided print job. In order to measure the fluctuation part more accurately, it is preferable that the temperature rises as much as possible. For this reason, it is preferable to update the variable portion after image formation for double-sided printing is completed, since the temperature of the image forming unit 40 (surrounding temperature of the primary transfer roller 44) tends to increase when the image forming unit 40 returns.

The unchanged portion updated by the unchanged portion update process can be used to calculate the corrected transfer voltage when the next print job is executed.

Operations of the image forming apparatus 100 will be described.

FIG. 8 is a flow chart showing the operation of the image forming apparatus 100. As shown in FIG. This flowchart can be executed by the control unit 110 according to a program stored in the storage unit 120 .

The control unit 110 determines whether or not a print job has been obtained (S101). For example, the control unit 110 can determine that the print job has been acquired when the print job is received by the communication unit 130 .

When determining that the print job has not been received (S101: NO), the control unit 110 repeatedly executes step S101.

When determining that the print job has been received (S102: YES), the control unit 110 executes determination processing to determine the ATVC determination value (S102).

The control unit 110 applies the determined ATVC determination value as a transfer voltage to the primary transfer roller 44 under constant voltage control, thereby primarily transferring the toner image formed on the photosensitive drum 42 onto the intermediate transfer belt 43 . Image formation is performed by image formation processing including a process for forming an image (S103).

If the control unit 110 determines that image formation has not been completed for all pages (S104; NO), the control unit 110 corrects the transfer voltage at a correction ratio according to the amount of change in temperature measured by the sensor 180 (S105). ). That is, the control unit 110 corrects the transfer voltage by calculating the post-correction transfer voltage by adding the changing portion correction value obtained by multiplying the unchanged portion by the correction ratio to the unchanged portion.

When the control unit 110 determines that the image formation of all pages is completed (S104: YES), it determines whether or not the update condition of the unchanged portion is satisfied (S106). The condition for updating the invariant portion may be, as described above, that the temperature is equal to or greater than a predetermined threshold, or that the print job is a double-sided print job, or the like.

If the control unit 110 determines that the update condition of the invariant part is not satisfied (S106: NO), the process ends.

If the control unit 110 determines that the update condition of the invariant part is satisfied (S106: YES), it performs determination processing and updates the invariant part with the determined ATVC decision value (S107).

Although the transfer voltage is corrected for each sheet 900 (one page) in the flowchart of FIG. 8, it may be corrected at an appropriate predetermined frequency (for example, every 10 pages). The predetermined frequency can be appropriately set through experiments from the viewpoint of the quality of the image formed on the paper 900 . The predetermined frequency may be, for example, when the amount of temperature change is 5° C. or more.

(Second embodiment)
A second embodiment will be described. The difference between this embodiment and the first embodiment is as follows. In the first embodiment, the post-correction transfer voltage is calculated without considering changes in the unchanged portion due to influence factors such as humidity that affect the unchanged portion. On the other hand, in the present embodiment, the post-correction transfer voltage is calculated in consideration of changes in the unchanged portion due to influence factors such as humidity that affect the unchanged portion. In other respects, this embodiment is the same as the first embodiment, so redundant description will be omitted or simplified.

FIG. 9 is a graph for explaining the conventional technology. The horizontal axis of the graph is the amount of change in temperature, and the vertical axis is the transfer voltage.

In the conventional technology, the transfer voltage is determined by the ATVC before image formation by a print job is started, as in the present embodiment. The determined transfer voltages are indicated by black dots on the graph. After the image formation is started, the transfer voltage is corrected by the correction formula as indicated by the solid line based on the temperature change (temperature rise). When the absolute humidity changes above the threshold value, the divergence between the transfer voltage corrected by the correction formula and the ideal value of the transfer voltage for each temperature (transfer current value that produces a predetermined transfer current) indicated by the dashed line becomes significant. . Therefore, when the absolute humidity changes beyond the threshold, the ATVC is performed again. The transfer voltage determined by rerunning ATVC is indicated by the open circle points on the graph. Then, the transfer voltage is corrected by another correction formula corresponding to the changed absolute humidity. In the conventional technology, if the humidity changes to a threshold value or more, even during execution of a print job, ATVC needs to be re-executed during non-image formation such as between paper sheets, which may reduce productivity.

FIG. 10 is a graph for explaining calculation of the corrected transfer voltage in this embodiment. The horizontal axis of the graph is temperature, and the vertical axis is transfer voltage.

As shown in FIG. 10, when the absolute humidity changes (for example, rises) during image formation due to the execution of image formation by a print job, the absolute humidity becomes an influencing factor. The immutable part changes. Influencing factors are factors that differ from variable factors. Therefore, the invariant portion is calculated in advance for each absolute humidity, and the transfer voltage is corrected by calculating the post-correction transfer voltage during image formation based on the invariant portion corresponding to the changed absolute humidity. As a result, it is possible to suppress the deterioration of the transfer performance of the primary transfer due to the change in the absolute humidity without lowering the productivity. It should be noted that the influencing factor can be relative humidity.

The control unit 110 registers an invariant portion for each absolute temperature by calculating it in advance before executing the print job and storing it in the storage unit 120 . The invariant portion can be calculated in the same manner as in the first embodiment.

Control unit 110 measures temperature and absolute humidity by sensor 180 before image formation by a print job, and reads the constant portion corresponding to the absolute humidity from storage unit 120 . Control unit 110 determines the ATVC determination value through determination processing. The ATVC decision values are indicated by the black dots on the graph.

The control unit 110 measures the absolute humidity as well as the temperature using the sensor 180 during image formation by the print job. When the measured absolute humidity changes by a predetermined threshold value or more, the control unit 110 reads the unchanged portion corresponding to the absolute humidity from the storage unit 120, and changes the unchanged portion to the read unchanged portion. The predetermined threshold can be appropriately set through experiments from the viewpoint of the quality of the image formed on the paper 900 . The control unit 110 calculates the variable portion by subtracting the read unchanged portion from the ATVC determination value. The control unit 110 calculates a correction ratio according to the amount of change in temperature using an approximation formula (see the first embodiment) of the relationship between the amount of change in temperature and the correction ratio, and multiplies the change portion by the change Calculate the partial correction value. The control unit 110 calculates the post-correction transfer voltage by adding the changing portion correction value to the unchanged portion. The control unit 110 corrects the transfer voltage with the post-correction transfer voltage.

Embodiments of the present invention have the following effects.

A determination process is performed to determine a constant-voltage-controlled transfer voltage that generates a predetermined transfer current for transferring the toner image formed on the image carrier to the transfer material, and the transfer current generated by the transfer voltage is varied. The transfer voltage is corrected at a correction ratio corresponding to the amount of change from the time of the determination process of the variation factors that cause the transfer voltage to change. As a result, it is possible to suppress the deterioration of the transfer performance due to manufacturing variations and temporal fluctuations in the resistance of the transfer portion, and prevent a decrease in productivity.

Further, the transfer voltage is corrected by correcting the changing portion of the determined transfer voltage, excluding the unchanged portion that does not change due to the fluctuation factor, with the correction ratio. Thereby, the transfer performance can be effectively improved.

Furthermore, with the temperature as a variation factor, the variation portion is corrected based on the rate of temperature change. As a result, the transfer performance can be improved simply and effectively.

Also, with the relative humidity as a variation factor, the variation portion is corrected based on the rate of change in the relative humidity. As a result, the transfer performance can be improved simply and effectively.

Also, the absolute humidity is used as a variation factor, and the variation portion is corrected based on the change rate of the absolute humidity. As a result, the transfer performance can be improved simply and effectively.

Also, the transfer voltage determined by performing determination processing when the temperature reaches or exceeds a predetermined threshold value is calculated as the unchanged portion. This makes it possible to improve the calculation accuracy of the fluctuation portion.

Furthermore, the transfer voltage determined by performing the determination process after the image formation by the print job is completed is calculated as the unchanged portion. This makes it possible to easily calculate the invariant portion.

Furthermore, the transfer voltage determined by performing the determination process after the image formation by the double-sided print job is completed is calculated as the unchanged portion. As a result, the unchanged portion can be easily calculated, and the transfer performance can be further improved.

In addition, the invariant portion is calculated based on the transfer voltage determined by the determination process under a plurality of conditions in which the resistance of the path through which the transfer current flows is different. This makes it possible to easily calculate the invariant portion.

Furthermore, the invariant part is changed when the influencing factors affecting the invariant part change. As a result, it is possible to suppress the deterioration of the transfer performance due to the change of the unchanged portion during the image formation, and prevent the deterioration of the productivity.

Furthermore, using temperature as an influencing factor, an invariant portion is calculated based on the temperature. As a result, it is possible to suppress the deterioration of the transfer performance due to the change of the unchanged portion.

Also, with relative humidity as an influencing factor, an invariant portion is calculated based on the relative humidity. As a result, it is possible to suppress the deterioration of the transfer performance due to the change of the unchanged portion.

Also, using the absolute humidity as an influencing factor, the invariant portion is calculated based on the absolute humidity. As a result, it is possible to suppress the deterioration of the transfer performance due to the change of the unchanged portion.

The invention is not limited to the embodiments described above.

For example, in the embodiments, the temperature has been described as a variable factor that changes the transfer current generated by applying a constant-voltage-controlled transfer voltage to the transfer section. However, temperature, relative humidity, and absolute humidity are related to each other, and if the relative humidity or absolute humidity causes the transfer current to fluctuate more significantly, the transfer voltage after correction is set as the fluctuation factor as the relative humidity or absolute humidity. can be calculated.

Also, for example, if the variable factor is absolute humidity, the influencing factor affecting the constant part may be temperature or relative humidity. Similarly, if the variable is relative humidity, the influencing factor affecting the constant part may be temperature or absolute humidity.

Further, in the embodiments, the image bearing member, the transfer target member, and the transfer section are explained using the photosensitive drum, the intermediate transfer belt, and the primary transfer roller as examples, respectively. However, the image carrier, transfer material, and transfer section can be intermediate transfer belts, paper, and secondary transfer rollers, respectively.

Also, part or all of the processing executed by the program in the embodiment may be executed by replacing it with hardware such as a circuit.

42 photoreceptor drum,
43 intermediate transfer belt,
44 primary transfer roller,
100 image forming apparatus,
110 control unit,
120 storage unit,
130 Communication Department,
140 operation display unit,
150 image reading unit;
160 image control unit,
170 image forming unit;
180 sensor.

Claims (15)

a transfer unit that transfers the toner image formed on the image bearing member to the transfer member with a constant-voltage controlled transfer voltage;
Determination processing is performed to determine the transfer voltage for generating a predetermined transfer current, and a correction ratio corresponding to the amount of change from the time of the determination processing of the variation factor that causes the transfer current to fluctuate due to the transfer voltage is set. a control unit that corrects the transfer voltage based on
An image forming apparatus having 2. The image according to claim 1, wherein the control unit corrects the transfer voltage by correcting, with the correction ratio, a varying portion of the determined transfer voltage, excluding an unchanged portion that does not vary due to the variation factor. forming device. The variable factor is temperature,
3. The image forming apparatus according to claim 2, wherein said controller corrects said fluctuation portion based on a temperature change rate. The variable factor is relative humidity,
3. The image forming apparatus according to claim 2, wherein said control section corrects said fluctuation portion based on a rate of change in relative humidity. The variable factor is absolute humidity,
3. The image forming apparatus according to claim 2, wherein said control section corrects said fluctuation portion based on a rate of change in absolute humidity. 3. The image forming apparatus according to claim 2, wherein the control unit calculates the transfer voltage determined by performing the determination process when the temperature reaches or exceeds a predetermined threshold as the constant portion. 3. The image forming apparatus according to claim 2, wherein the control unit calculates the transfer voltage determined by performing the determination process after image formation by a print job is completed as the constant portion. 8. The image forming apparatus of claim 7, wherein the print job includes duplex printing. The control unit determines the transfer voltage by the determination process under a plurality of conditions in which the resistance of the path through which the transfer current flows is set to different conditions, and calculates the invariant portion based on the determined transfer voltage. 3. The image forming apparatus according to claim 2. 3. The image forming apparatus according to claim 2, wherein said control section changes said invariant portion when an influencing factor different from said variable factor, which affects said invariant portion, changes. the influencing factor is temperature,
11. The image forming apparatus according to claim 10, wherein said controller calculates said constant portion based on temperature. the influencing factor is relative humidity,
11. The image forming apparatus according to claim 10, wherein said controller calculates said constant portion based on relative humidity. the influencing factor is absolute humidity,
11. The image forming apparatus according to claim 10, wherein said controller calculates said constant portion based on absolute humidity. a step (a) of transferring the toner image formed on the image bearing member to a transferred member with a transfer voltage controlled by a constant voltage;
A determination process for determining the transfer voltage for generating a predetermined transfer current is performed, and a variation factor for varying the transfer current generated by the determined transfer voltage is determined according to the amount of change from the time of the determination process. a step (b) of correcting the transfer voltage for transferring the toner image onto the transfer material in the step (a) based on the rate of change;
An image forming method comprising: a step (a) of transferring the toner image formed on the image bearing member to the transferred member at a constant-voltage controlled transfer voltage;
A determination process for determining the transfer voltage for generating a predetermined transfer current is performed, and a variation factor for varying the transfer current generated by the determined transfer voltage is determined according to the amount of change from the time of the determination process. a step (b) of correcting the transfer voltage for transferring the toner image to the transfer material in the step (a) based on the rate of change;
An image forming program for executing on a computer.

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