JP2020148846A - Image formation device and method for controlling image formation device - Google Patents

Abstract

To increase the transfer efficiency of a secondary transfer unit.SOLUTION: An image formation device includes: a photoreceptor for carrying a toner image; an intermediate transfer belt; a primary transfer unit for transferring a toner image carried by the photoreceptor to the intermediate transfer belt by a primary transfer current; a secondary transfer unit for transferring the toner image transferred to the intermediate transfer belt, to a piece of paper; a reception unit 202 for receiving a job; a specification unit 206 for specifying a drive parameter value A of the photoreceptor based on the job received by the reception unit 202; and a setting unit 206 for setting the current value of the primary transfer current to one of a first current value I1 and a second current value I2 larger than the first current value on the basis of the drive parameter value A specified by the specification unit 206 and a first threshold value.SELECTED DRAWING: Figure 6

Description

The present disclosure relates to an image forming apparatus and a method for controlling the image forming apparatus.

Conventionally, a primary transfer unit that transfers a toner image carried by a photoconductor to an intermediate transfer body (for example, an intermediate transfer belt) and a secondary transfer that transfers a toner image transferred to the intermediate transfer body to a recording medium. An image forming apparatus having a portion is known. Further, for example, the image forming apparatus described in Patent Document 1 controls the transfer voltage so that an appropriate transfer current can be obtained even if the electrical resistance of the intermediate transfer body fluctuates during image formation.

Japanese Unexamined Patent Publication No. 2015-222407

However, the image forming apparatus described in Patent Document 1 has a problem that when the primary transfer current is low, the amount of charge of the toner becomes small, so that the secondary transfer efficiency in the secondary transfer portion may decrease. there were.

The present disclosure has been made in view of the above circumstances, and in a certain aspect, an image forming apparatus for improving transfer efficiency in a secondary transfer unit and a control method for the image forming apparatus are disclosed.

According to a certain aspect, the image forming apparatus comprises an image carrier carrying a toner image, an intermediate transfer body, and a primary transfer unit that transfers the toner image carried by the image carrier to the intermediate transfer body by a transfer current. A secondary transfer unit that transfers the toner image transferred to the intermediate transfer body to a recording medium, a reception unit that accepts jobs, and a specific unit that specifies the drive parameter value of the image carrier based on the job accepted by the reception unit. A setting unit that sets the current value of the transfer current to either the first current value or the second current value larger than the first current value based on the drive parameter value and the predetermined value specified by the specific unit. And.

In a certain aspect, the specific unit specifies the drive parameter value of the image carrier driven by the job accepted by the reception unit.

In a certain aspect, the specific unit specifies, as a drive parameter value, an integrated value of unit drive parameter values each time the secondary transfer unit transfers a toner image to a predetermined number of recording media.

In a certain aspect, the specific unit is a value obtained by subtracting the cumulative drive parameter value of the image carrier before the reception unit accepts the job from the cumulative drive parameter value of the image carrier when the job accepted by the reception unit is completed. Is specified as the drive parameter value.

In a certain aspect, the specific unit specifies the drive parameter value of the image carrier driven by the job accepted by the reception unit as the drive parameter value.

In a certain aspect, the specific unit determines the first job and the second job when the reception unit accepts the second job from the time when the reception unit receives the first job to the time when the predetermined time elapses. Identify the drive parameter values of the image carrier based on the job integrated with.

In a certain aspect, a static elimination unit for statically eliminating the image carrier is further provided, and the specific unit specifies a drive parameter value of the image carrier based on the job after the static elimination unit statically eliminates the image carrier.

In a certain aspect, the identification unit specifies the drive parameter value during the period when the transfer current is output.

In a certain aspect, the setting unit further includes a prohibiting unit that prohibits the setting unit from setting the current value of the transfer current to the second current value based on the environment of the image forming apparatus.

In a certain aspect, the setting unit sets the current value of the transfer current to either a second current value or a third current value larger than the second current value, based on the environment of the image forming apparatus.

In a certain aspect, the predetermined value includes a first predetermined value and a second predetermined value smaller than the first predetermined value, and the setting unit determines that the drive parameter value is larger than the first predetermined value. When 1 current value is set and the drive parameter value is equal to or less than the first predetermined value and larger than the second predetermined value, the second current value is set and the drive parameter value is equal to or less than the second predetermined value. Is set to a third current value.

In a certain aspect, the setting unit sets the current value of the transfer current as the first current value and the second current value based on the predetermined value based on the environment of the image forming apparatus and the drive parameter value specified by the specific unit. Set to one of.

In a certain aspect, the image carrier is further provided with an image forming unit, and a condition changing unit for changing the image forming conditions of the image forming unit according to the current value set by the setting unit is further provided.

In a certain aspect, the plurality of primary transfer units corresponding to each of the plurality of colors are provided, and the setting unit sets the current value of the transfer current used for at least one of the plurality of primary transfer units to the second current value. Set to.

In one aspect, the drive parameter value is either the drive amount of the image carrier, the amount of recording medium on which the image was formed using the image carrier, or the drive time of the image carrier.

According to another aspect, the image forming method transfers to an intermediate transfer member based on a step of accepting a job, a step of specifying a drive parameter value of an image carrier based on the job, and a drive parameter value and a predetermined value. The step includes setting the current value of the transfer current to either a first current value or a second current value larger than the first current value.

According to this disclosure, it is possible to provide an image forming apparatus and a control method of the image forming apparatus for improving the transfer efficiency by the secondary transfer unit.

It is a figure which shows the internal structure of an image forming apparatus. It is a figure which showed the hardware structure of the image forming apparatus. It is a figure which shows the relationship between the secondary transfer voltage and the secondary transfer efficiency. It is a figure which shows an example of the charge amount distribution of the toner after the primary transfer by the primary transfer part. It is a figure which shows the relationship between the primary transfer current and the number of prints which can tolerate density unevenness by a transfer memory. It is a figure which shows the functional configuration example of a control device. It is a flowchart of the process of the image forming apparatus of this embodiment. It is a flowchart of the process of the image forming apparatus of another embodiment. It is a figure for demonstrating the concept of the job of another embodiment. It is a figure which shows the relationship between the paper and the period during which a primary transfer current is output. This is an example of a table used by the prohibition unit. This is an example of a table used by the setting unit (No. 1). This is an example of a table used by the setting unit (No. 2). It is a flowchart of the process of the image forming apparatus of another embodiment. This is an example of changing the image formation conditions when the primary transfer current is set to the second current value. It is a figure which showed an example such as a color which changes a primary transfer current.

<First Embodiment>
The image forming apparatus according to the embodiment based on the present invention will be described below with reference to the drawings. When referring to the number, quantity, etc. in the embodiments described below, the scope of the present invention is not necessarily limited to the number, quantity, etc., unless otherwise specified. The same reference number may be assigned to the same part or equivalent part, and duplicate explanations may not be repeated. Further, it is planned from the beginning to use the configurations in each embodiment in appropriate combinations.

[Configuration example of image forming apparatus]
The schematic configuration of the image forming apparatus 100 in this embodiment will be described with reference to FIG. FIG. 1 is a diagram showing an internal configuration of the image forming apparatus 100.

FIG. 1 shows an image forming apparatus 100 as a color printer. Hereinafter, the image forming apparatus 100 as a color printer will be described, but the image forming apparatus 100 is not limited to the color printer. For example, the image forming apparatus 100 may be a monochrome printer, or may be a multifunction device (MFP: Multi-Functional Peripheral) including a monochrome printer, a color printer, and a facsimile.

The image forming apparatus 100 includes image forming units 1A to 1D as forming portions, an intermediate transfer belt 11 (intermediate transfer body), a primary transfer roller 12, a secondary transfer roller 13, a cleaning portion 15, and paper ejection. It includes a tray 16, a cassette 17, a control device 18, an exposure control unit 19, a fixing device 30 as a fixing unit, a paper ejection roller 36, a reverse transfer path 38, and the like.

The image forming unit 1A forms a yellow (Y) toner image. The image forming unit 1B forms a toner image of magenta (M). The image forming unit 1C forms a toner image of cyan (C). The image forming unit 1D forms a black (BK) toner image.

The intermediate transfer belt 11 is an endless belt, and is stretched by a plurality of support rollers including the support roller 63. By rotating at least one of the plurality of support rollers, the intermediate transfer belt 11 is driven orbiting in the direction of the arrow 21. The image forming units 1A to 1D are arranged in order along the driving direction of the intermediate transfer belt 11, respectively.

The image forming units 1A to 1D include a photoconductor 2, a charging unit 3, a developing unit 4, a photoconductor cleaning unit 5, an exposure unit 9, and a static elimination unit 80, respectively. The photoconductor 2 is an image carrier that supports a toner image. As an example, as the photoconductor 2, a photoconductor drum having a photosensitive layer formed on its surface is used. The photoconductor 2 rotates in a direction corresponding to the driving direction of the intermediate transfer belt 11.

The photoconductor 2 has, for example, an undercoat layer (UCL: Under Coat Layer), a charge generation layer (CGL: Charge Generation Layer), and a charge transport layer (CTL) on the peripheral surface of a conductive cylindrical body (aluminum tube) made of aluminum. : Charge Transport Layer) is sequentially laminated to be a negatively charged organic photo-conductor (OPC). The charge generation layer is made of an organic semiconductor in which a charge generation material (for example, a phthalocyanine pigment) is dispersed in a resin binder (for example, polycarbonate), and a pair of positive charges and negative charges are generated by exposure by the exposure unit 9. The charge transport layer is composed of a hole transporting material (electron donating nitrogen-containing compound) dispersed in a resin binder (for example, polycarbonate resin), and transports positive charges generated in the charge generation layer to the surface of the charge transport layer. To do.

The charging unit 3 uniformly charges the surface of the photoconductor 2 with a negative electrode property. The charged portion 3 is, for example, a conductive rubber roller, and is arranged in contact with the photoconductor 2. Further, the charging unit 3 rotates according to the rotational drive of the photoconductor 2. A voltage (hereinafter, also referred to as a charging bias or a charging voltage) is applied to the charging unit 3 by the power supply 400. The power supply 400 outputs a DC voltage controlled to a predetermined voltage. The photoconductor 2 is uniformly charged by the charging unit 3. That is, the charging unit 3 charges the photoconductor 2 based on the charging voltage.

The exposure unit 9 irradiates the photoconductor 2 with laser light in response to a control signal from the exposure control unit 19, and exposes the surface of the photoconductor 2 according to a designated image pattern. The surface potential of the unexposed portion of the photoconductor 2 is maintained at the charging potential. By this exposure, electrostatic latent images of each color (YMCK) are formed on the photoconductor 2.

The developing unit 4 develops an electrostatic latent image formed on the photoconductor 2 as a toner image. As an example, the developing unit 4 develops an electrostatic latent image using a two-component developer composed of toner and carriers. The carrier is, for example, iron powder. The developing unit 4 has a developing roller 4A. For example, a development bias is applied to the developing roller 4A. Due to the triboelectric charging of the toner and the carrier, the toner and the carrier are charged with electricity of opposite polarity (for example, static electricity). In this embodiment, it is assumed that the toner has a negative polarity and the carrier has a positive polarity. That is, the toner is charged by this stirring. As a modification, the toner may have a positive polarity and the carrier may have a negative polarity.

In the photoconductor 2, toner is supplied to the lowered portion where the surface potential is lowered by exposure. On the other hand, toner is not supplied to the portion other than the lowered portion (the portion where the surface potential is not lowered). As a result, toner images of each color are formed on the photoconductor 2.

Further, the primary transfer roller 12 sandwiches the intermediate transfer belt 11 between the photoconductor 2 and the photoconductor 2. For example, the primary transfer roller 12 abuts on the intermediate transfer belt 11 and pressurizes the intermediate transfer belt 11 against the photoconductor 2. In the present embodiment, the portion sandwiched between the primary transfer roller 12 and the photoconductor 2 functions as the primary transfer unit 12A (primary transfer nip). The primary transfer unit 12A transfers the toner image on the photoconductor 2 to the intermediate transfer belt 11.

Further, the primary transfer current output unit 60 outputs the primary transfer current to the primary transfer roller 12 for each color. The primary transfer current corresponds to the "transfer current" of the present disclosure. Due to the output of the primary transfer current, a transfer bias having the opposite polarity (that is, + polarity) to the toner is applied to the primary transfer roller 12. A transfer electric field is formed by the transfer bias. The contacted toner image is transferred to the intermediate transfer belt 11 by this transfer electric field. Since this transfer bias is positive, while the charging bias is negative, the transfer bias and the charging bias are opposite polarities. The image forming apparatus executes control that the toner images of the first to fourth colors (toner images of each YMCK) are transferred synchronously on the intermediate transfer belt 11 so as to overlap each other. By applying the transfer voltage to the primary transfer roller 12 in this way, the toner image is transferred to the intermediate transfer belt 11. The primary transfer unit 12A transfers the toner image carried by the photoconductor 2 to the intermediate transfer belt 11 by the transfer current output from the primary transfer current output unit 60. Note that, in FIG. 1, the arrangement of the primary transfer current output unit 60 is an example, and the primary transfer current output unit 60 may be arranged at another location.

The cassette 17 is provided in the lower part of the image forming apparatus 100. A recording medium is housed in the cassette 17. Recording media include, for example, plain paper, woodfree paper, art paper, coated paper, Japanese paper, postcard paper, transparent film and the like. Hereinafter, the recording medium will be described as “paper 14”. The paper 14 is sent from the cassette 17 one by one to the secondary transfer unit 13A.

The secondary transfer unit 13A is composed of a support roller 63 and a secondary transfer roller 13. The secondary transfer roller 13 is a roller that pressurizes and rotates the support roller 63. The secondary transfer portion 13A is also a nip portion formed by the support roller 63 and the secondary transfer roller 13. The control device 18 synchronizes the timing of feeding and transporting the paper 14 with the position of the toner image (toner image in which each color is superimposed) on the intermediate transfer belt 11 so that the secondary transfer unit 13A receives the paper 14. Transfer the toner image to an appropriate position. After that, the paper 14 on which the toner image is transferred is sent to the fixing device 30. Further, for example, the secondary transfer current output unit (not particularly shown) outputs the secondary transfer current to the secondary transfer roller 13. By outputting the secondary transfer current to the secondary transfer roller 13, the secondary transfer voltage is applied to the secondary transfer roller 13. In the secondary transfer unit 13A, an electric field is generated between the intermediate transfer belt 11 and the secondary transfer roller 25 by the secondary transfer voltage applied to the secondary transfer roller 13. By the action of this electric field, the toner image on the intermediate transfer belt 11 is electrostatically transferred to the paper 14.

The fixing device 30 heats the toner image (unfixed toner image) transferred to the paper 14 to fix the toner image on the paper 14. The fixing device 30 sandwiches between the fixing roller 32 as a heating member heated by the heating heater 32h as a heating device and the paper 14 on which an unfixed image is formed on the surface together with the fixing roller 32 and between the fixing roller 32. A pressurizing roller 31 as a pressurizing member for fixing an unfixed image on the paper 14 while passing through the paper 14 and a fixing temperature detecting unit 33 are provided. The fixing temperature is controlled by the control device 18 based on the detection result by the fixing temperature detecting unit 33.

Further, the image forming apparatus 100 can receive the input of the user's command from the operation unit 50 and execute the job. The job includes, for example, a single-sided printing job (a job for single-sided printing), a double-sided printing job (a job for double-sided printing), a scan job (a job for scanning), and the like. The job includes, for example, a single-sided printing job (a job for single-sided printing), a double-sided printing job (a job for double-sided printing), a scan job (a job for scanning), and the like. In the job, the user can also specify an image to be printed by the image forming apparatus 100, the number of sheets to be printed by the image forming apparatus 100, and the like. Also, "printing" is also referred to as "forming an image".

When a single-sided printing job command is input by the user, the paper 14 is ejected to the output tray 16 by the output roller 36 after the fixing process by the fixing device 30. When a command for a double-sided printing job is input by the user, the paper 14 is sent to the reverse transfer path 38 by the reverse rotation of the paper ejection roller 36 after the fixing process by the fixing device 30. After that, the paper is sent to the secondary transfer roller 13 so that the toner image is transferred to the back surface (second side) of the paper. The secondary transfer roller 13 transfers the toner image to an appropriate position on the back surface of the paper 14. After that, it is sent to the fixing device 30 again, and the fixing device 30 fixes the toner image on the back surface of the paper. In this way, when the user inputs the command of the double-sided printing job, it is possible to print on both sides.

The cleaning unit 15 includes a cleaning blade. The cleaning blade is pressed against the intermediate transfer belt 11 to collect the toner particles remaining on the intermediate transfer belt 11 after the toner image is transferred. The toner particles are transported by a transport screw (not shown) and collected in a waste toner container (not shown).

The control device 18 controls the image forming process of the image forming apparatus 100. The control device 18 includes image forming units 1A to 1D, a secondary transfer roller 13, a fixing device 30 (temperature control of the heater 32h, a rotation speed of the pressurizing roller 31, etc.), an exposure control unit 19, and a primary transfer current output unit. 60 etc. are controlled.

A cooler 55 is provided downstream of the fuser 30. The cooler 55 includes a cooling roller 52 (cooling portion) and an opposing roller 51 (opposing portion). The cooler 55 is controlled by the control device 18. The facing roller 51 faces the cooling roller 52, and the facing roller 51 and the cooling roller 52 hold the paper.

In this way, the opposing roller 51 and the cooling roller 52 hold the paper and cool the paper, so that the image forming apparatus 100 can stably cool the paper.

The material of the intermediate transfer belt 11 is semi-conductive with carbon dispersed in polycarbonate, PTFE (polytetrafluoroethylene), or polyimide as a main raw material.

[Hardware configuration]
FIG. 2 is a diagram showing a hardware configuration of the image forming apparatus 100. With reference to FIG. 2, the image forming apparatus 100 includes a CPU (Central Processing Unit) 101 that executes an image forming program, a ROM (Read Only Memory) 102 that non-volatilely stores data such as an image forming program, and data. A RAM (Random Access Memory) 103 that volatilely stores the data, a flash memory 104, an operation unit 50, a speaker 106, and a communication IF 108 are provided. The image forming program is a program to be executed by a computer.

The operation unit 50 includes a display 1051 as a display device and a touch panel 1052 as an input device. Specifically, the operation unit 50 is realized by positioning and fixing the touch panel 1052 on the display 1051 (for example, a liquid crystal display). The touch screen is also referred to as a touch panel display, a display with a touch panel, or a touch panel monitor. The operation unit 50 can use, for example, a resistance film method or a capacitance method as a method for detecting the touch position. When the user operates the operation unit 50, a command is input.

The flash memory 104 is a non-volatile semiconductor memory. The flash memory 104 stores an operating system executed by the CPU 101, various programs, various contents, and data. Further, the flash memory 104 volatilely stores various data such as data generated by the image forming apparatus 100 and data acquired from an external device of the image forming apparatus 100.

The speaker 106 generates sound in response to a command from the CPU 101. The CPU 101 specifies an input position based on the output from the touch panel 1052, and displays a screen based on the specified input position.

Further, the communication IF 108 is connected to another external device (for example, a PC) through a network. When a job is input by the user from the other external device, the image forming apparatus 100 acquires the job via the communication IF 108.

The processing in the image forming apparatus 100 is realized by each hardware and software executed by the CPU 101. Such software may be pre-stored in the flash memory 104. Each component constituting the image forming apparatus 100 shown in the figure is a general one. Therefore, it can be said that an essential part of the present invention is software stored in a flash memory 104, a memory card or other storage medium, or software that can be downloaded via a network. Since the operation of each hardware of the image forming apparatus 100 is well known, the detailed description will not be repeated.

The storage medium is not limited to DVD-ROM, CD-ROM, FD (Flexible Disk), and hard disk, but also magnetic tape, cassette tape, and optical disk (MO (Magnetic Optical Disc) / MD (Mini Disc) / DVD (Digital). A medium such as a Versatile Disc)), an optical card, a mask ROM, an EPROM (Erasable Programmable Read Only Memory), an EEPROM (Electrically Erasable Programmable Read-Only Memory), or a semiconductor memory such as a flash ROM may be used. The recording medium is a non-temporary medium in which the program or the like can be read by a computer.

The program referred to here includes not only a program that can be directly executed by the CPU, but also a source program format program, a compressed program, an encrypted program, and the like.

[Thought of this embodiment]
Next, the idea of this embodiment will be described. FIG. 3 is a diagram showing the relationship between the secondary transfer voltage and the secondary transfer efficiency. In FIG. 3, the horizontal axis represents the secondary transfer voltage (voltage applied to the secondary transfer roller 13), and the vertical axis represents the secondary transfer efficiency. The secondary transfer efficiency indicates the transfer efficiency of the secondary transfer unit 13A. The secondary transfer efficiency is, for example, "the amount of toner image transferred to the paper 14 by the secondary transfer unit 13A" and "the amount of toner image on the intermediate transfer belt 11 before being transferred to the secondary transfer unit 13A". It is the value divided by. The secondary transfer efficiency may be calculated by another method.

Further, in FIG. 3, the graph plotted in the circle image shows the case where the primary transfer current is 9.5 μA, and the graph plotted in the triangular image shows the case where the primary transfer current is 13.5 μA. The case is shown and the graph plotted in the square image shows the case where the primary transfer current is 20.5 μA.

In FIG. 3, for each primary transfer current (9.5 μA, 13.5 μA, and 20.5 μA), the secondary transfer voltages are set to 500 V, 1000 V ,. .. .. The secondary transfer efficiency was determined.

As shown in FIG. 3, it was found that the larger the value of the primary transfer current, the higher the secondary transfer efficiency tends to be. The range of the secondary transfer voltage at which the secondary transfer efficiency is equal to or higher than a predetermined value (for example, 90%) is referred to as an "optimal voltage range". As shown in FIG. 3, it was found that the larger the value of the primary transfer current, the wider the optimum voltage range.

FIG. 4 is a diagram showing an example of the charge amount distribution of the toner after the primary transfer by the primary transfer unit 12A. FIG. 4A shows a toner charge distribution when the primary transfer current is 9.5 μA. FIG. 4B shows the charge amount distribution of the toner when the primary transfer current is 13.5 μA. FIG. 4C shows a toner charge distribution when the primary transfer current is 20.5 μA.

In each of FIGS. 4A to 4C, the horizontal axis represents the amount of toner charged and the vertical axis represents the number of toners. In each of FIGS. 4A to 4C, the peaks of the toner charge amount distribution are defined as peak P1, peak P2, and peak P3, respectively. As shown in FIGS. 4A to 4C, as the value of the primary transfer current increases, the peak of the toner charge amount distribution shifts to the toner charge side (negative electrode side). That is, as the value of the primary transfer current increases, the amount of charge of the toner increases, and as a result, the secondary transfer efficiency increases.

Next, the density unevenness of the transfer memory factor will be described. In general, the static eliminator can remove the negative charging characteristics of the photoconductor by removing the static charge from the photoconductor (the photoconductor can be statically removed). On the other hand, the bias of the primary transfer based on the primary transfer current is positive. Therefore, when the current value of the primary transfer current is high, even if the static eliminator removes the photoconductor, the positive charging characteristics remain, and as a result, the surface potential of the photoconductor becomes excessively high. It ends (it changes exactly). In this case, with respect to the portion where the surface potential of the photoconductor 2 becomes high, a concentration step, a horizontal streak, or the like occurs at the portion where the surface potential of the photoconductor 2 becomes high in the next charging step. Due to this density step and horizontal streaks, density unevenness due to the transfer memory factor occurs. As described above, when the current value of the primary transfer current is high, the density unevenness due to the transfer memory tends to occur.

FIG. 5 is a diagram showing the relationship between the primary transfer current and the number of prints that can tolerate density unevenness due to the transfer memory (the number of prints immediately before (one sheet before) the density unevenness occurs). The vertical axis of FIG. 5 shows the number of prints immediately before the occurrence of density unevenness, and the horizontal axis shows the value of the primary transfer current. Further, on the horizontal axis, the first current value I1 and the second current value I2 of the primary transfer current are defined, and the second current value I2> the first current value I1. The first current value I1 is a normal current value.

As shown in FIG. 5, when the primary transfer current value is set to the first current value I1, density unevenness does not occur regardless of the number of printed sheets. As described above, the first current value I1 is a current value at which density unevenness does not occur regardless of the number of printed sheets. On the other hand, when the primary transfer current value was set to the second current value I2, density unevenness occurred from the Z + 1th sheet. The driving amount of the photoconductor 2 when the density unevenness occurs in the job 1 is set to a predetermined amount L. In other words, even when the primary transfer current is set to the second current value I2, density unevenness does not occur until the drive amount of the photoconductor 2 reaches a predetermined amount L in one job. As described above, the second current value I2 does not cause density unevenness until the driving amount of the photoconductor 2 reaches the predetermined amount L, but after the driving amount of the photoconductor 2 reaches the predetermined amount L (for example). (When the driving amount of the photoconductor 2 is larger than the predetermined amount L), it is a current value at which density unevenness can occur. In FIG. 5, the larger the value of the primary transfer current, the smaller the number of printed sheets in which density unevenness does not occur.

As shown in FIGS. 3 to 5, "the secondary transfer efficiency can be improved by increasing the primary transfer current, but when the drive amount of the photoconductor 2 reaches a predetermined amount L, density unevenness occurs. There is a phenomenon that "it ends up". The image forming apparatus 100 of the present embodiment executes a process based on this phenomenon.

[Example of functional configuration of control device]
FIG. 6 is a diagram showing a functional configuration example of the control device 18. The control device 18 has functions of a reception unit 202, a specific unit 204, a setting unit 206, and a storage unit 208.

The reception unit 202 receives a job based on the input of the user's command from the operation unit 50. In the present embodiment, this job is assumed to be a print job. When the reception unit 202 receives the job, the reception unit 202 outputs job data indicating the job to the specific unit 204. The control device 18 of the present embodiment activates the photoconductor 2 when the reception unit 202 receives the job.

The identification unit 204 specifies the drive parameter value of the photoconductor 2 based on the job (job data) received by the reception unit 202. Here, the drive parameter value may be any value as long as it is a parameter value that directly or indirectly indicates the drive of the photoconductor 2. For example, the drive parameter value may be the drive amount (rotation amount) of the photoconductor 2. Further, the drive parameter value may be the number of sheets of paper printed by the image forming apparatus 100 (the amount of the recording medium on which the image is formed by using the photoconductor 2). Further, the drive parameter value may be the time during which the photoconductor 2 is driven (the drive time of the photoconductor 2).

Further, the identification unit 204 specifies the drive parameter value by using the method (A) or the method (B) shown in FIG. First, the method (A) will be described. In the method (A), the drive parameter value is specified (calculated) by subtracting the "cumulative drive parameter value before job reception" from the "cumulative drive parameter value at the completion of the job accepted by the reception unit 202". To do).

For example, the "cumulative drive parameter value when the job received by the reception unit 202 is completed" is the cumulative drive parameter value from a predetermined timing to the time when the job received by the reception unit 202 is completed. In the present embodiment, it is assumed that the predetermined timing is, for example, when the image forming apparatus 100 is manufactured.

When the image forming apparatus 100 adopts the method (A), the specific unit 204 analyzes the job data from the reception unit 202. The specific unit 204 acquires job parameters by analyzing the job data. The job parameter is information that can specify the drive parameter of the photoconductor 2, and the job parameter is, for example, at least the number of prints, the amount of toner used in the printed image, the size of the printed image, and the like. Includes one. The identification unit 204 estimates (specifies) the cumulative drive parameter value A1 from the time when the image forming apparatus 100 is manufactured to the time when the job is completed. For this estimation, the image forming apparatus 100 stores, for example, a table in which the job parameters and the driving parameter values are associated with each other in the storage unit 208 in advance. The identification unit 204 specifies the cumulative drive parameter value based on the job parameter by referring to the table.

As a modification, the image forming apparatus 100 may store, for example, a function or expression in which a drive parameter value is output when a job parameter is input in the storage unit 208. The identification unit 204 specifies the cumulative drive parameter value by inputting a job parameter to the function or expression.

For example, the identification unit 204 specifies the cumulative drive parameter value A1 (cumulative drive parameter value from the time when the image forming apparatus 100 is manufactured to the time when the job is completed) using any of a table, an expression, and a function. To do. Further, the identification unit 204 specifies the cumulative drive parameter value A2, which is the cumulative drive parameter value before the job is accepted, from the time of manufacturing the image forming apparatus 100. The cumulative drive parameter value A2 is stored in the storage unit 208.

After that, the specific unit 204 can calculate the cumulative drive parameter value A based on the input job by executing the calculation of the specified cumulative drive parameter value A1-stored cumulative drive parameter value A2. Further, the specific unit 204 updates the “cumulative drive parameter value A2 stored in the storage unit 208” to the “specified cumulative drive parameter value A1”. Due to this update, even when the reception unit 202 receives the next job, the specific unit 204 has a new "cumulative drive parameter value A2 from the time of manufacturing the image forming apparatus 100 to before the reception of the next job." Can be obtained.

Next, the method (B) will be described. In the method (B), for example, the specific unit 204 sets “cumulative drive parameter value A2 from the time of manufacturing the image forming apparatus 100 to before accepting a job” to 0. At the same time, the specific unit 204 directly calculates the drive parameter value based on the input job. Even in such a method (B), the specific unit 204 can specify the drive parameter value A based on the input job.

The specific unit 204 outputs the specified drive parameter value A to the setting unit 206. The setting unit 206 sets the primary transfer current of the primary transfer current output unit 60. In the present embodiment, the setting unit 206 sets the current value of the primary transfer current as the first current value I1 and the second current value I2 based on the drive parameter value A and the predetermined value specified by the specific unit 204. Set to one of. Here, the predetermined value is set to the first threshold value N1, and the first threshold value N1 is stored in the storage unit 208. Further, the predetermined value also corresponds to the above-mentioned predetermined amount L.

The setting unit 206 compares the drive parameter value A with the first threshold value N1. When it is determined that the drive parameter value A is larger than the first threshold value N1, "when the primary transfer current is set to the second current value I2, the job received by the reception unit 202 is being executed. There is a high possibility that density unevenness will occur due to the transfer memory. " In this case, in order to prevent density unevenness from occurring, the setting unit 206 sets the first current value I1 as the current value of the primary transfer current.

On the other hand, when it is determined that the drive parameter value A is equal to or less than the first threshold value N1, "the reception unit 202 accepts even when the primary transfer current is set to the second current value I2. When the density unevenness caused by the transfer memory does not occur during the execution of the job. " In this case, in order to improve the secondary transfer efficiency, the setting unit 206 sets the second current value I2 as the current value of the primary transfer current.

The storage unit 208 stores in advance data for setting the first current value I1 and data for setting the second current value I2. The setting unit 206 outputs a control signal indicating the set current value to the primary transfer current output unit 60, so that the primary transfer current output unit 60 outputs the primary transfer current at the set current value. The portion shown by the broken line in FIG. 6 will be described in the embodiment described later.

[Flowchart of processing of image forming apparatus 100]
Next, a flowchart of processing of the image forming apparatus 100 (control apparatus 18) will be described with reference to FIG. 7.

First, in step S102, the reception unit 202 determines whether or not the job has been accepted. In step S102, the reception unit 202 waits until it determines that the job has been accepted (NO in step S102).

Next, in step S106, the identification unit 204 specifies the drive parameter value A of the photoconductor 2 based on the job received by the reception unit 202 (the job input by the user). The identification unit 204 specifies the drive parameter value A by using the above-mentioned method (A) or the above-mentioned method (B).

Next, in step S108, the setting unit 206 determines whether or not the drive parameter value A is larger than the first threshold value N1. When the setting unit 206 determines that the drive parameter value A is larger than the first threshold value N1 (YES in step S108), the process proceeds to step S110. Further, when the setting unit 206 determines that the drive parameter value A is equal to or less than the first threshold value N1 (NO in step S108), the process proceeds to step S112.

In step S110, the setting unit 206 sets the primary transfer current to the first current value I1. When the process of step S110 is completed, the process proceeds to step S114. Further, in step S112, the setting unit 206 sets the primary transfer current to the second current value I2. The process proceeds to step S114.

In step S114, the control device 18 starts the printing process at the first current value I1 set in step S110 or the second current value I2 set in step S112.

[Brief Summary]
(1) In the image forming apparatus 100 of the present embodiment, the identification unit 204 specifies the drive parameter value A of the photoconductor 2 based on the job accepted by the reception unit 202 (see step S106). After that, the setting unit 206 sets the current value of the transfer current to the first current value I1 and the first current value larger than the first current value, based on the drive parameter value A and the first threshold value N1 specified by the specific unit 204. 2 Set to one of the current value I2. In the present embodiment, when it is determined that the drive parameter value A is larger than the first threshold value N1, that is, "a job accepted by the reception unit 202 when the primary transfer current is set to the second current value I2". When there is a high possibility that density unevenness due to the transfer memory will occur during the execution of the above, the setting unit 206 sets the first current value I1 as the current value of the primary transfer current. As a result, the image forming apparatus 100 can prevent the occurrence of density unevenness caused by the transfer memory.

On the other hand, when it is determined that the drive parameter value A is equal to or less than the first threshold value N1, that is, "when the primary transfer current is set to the second current value I2, the job received by the reception unit 202" When the density unevenness caused by the transfer memory does not occur during the execution, the setting unit 206 sets the second current value I2 as the current value of the primary transfer current. As a result, the image forming apparatus 100 can improve the secondary transfer efficiency without causing density unevenness caused by the transfer memory.

Further, in the image forming apparatus 100 of the first embodiment, the first transfer current can be made the same for all the printing papers designated in one job. Therefore, in the first embodiment, it is possible to reduce the density unevenness caused by the difference in the first transfer current for all the printing papers designated in one job.

(2) Further, the specifying unit 204 specifies the driving parameter value of the photoconductor 2 driven by the job received by the receiving unit 202. Therefore, it is possible to determine whether or not density unevenness due to the transfer memory occurs during the execution of the job received by the reception unit 202.

(3) Further, the specific unit 204 uses the method (A) to subtract the "cumulative drive parameter value before job reception" from the "cumulative drive parameter value at the completion of the job accepted by the reception unit 202". By doing so, the drive parameter value is specified (calculated). Therefore, the identification unit 204 can appropriately specify the drive parameter value.

(4) Further, the specific unit 204 may set the “cumulative drive parameter value A2 from the time of manufacturing the image forming apparatus 100 to before receiving the job” to 0 by using the method (B). Along with this, the specific unit 204 directly calculates the drive parameter value based on the input job. Even in such a method (B), the specific unit 204 can appropriately specify the drive parameter value.

(5) Further, in the present embodiment, the static elimination unit 80 removes static electricity from the photoconductor 2 after the primary transfer is completed by the primary transfer unit 12A. That is, the specific unit 204 specifies the drive parameter value of the photoconductor 2 based on the job after the static elimination unit 80 has statically removed the photoconductor 2. If the static elimination unit 80 is an image forming apparatus (hereinafter, referred to as “the image forming apparatus of the first comparative example”) having a configuration in which the static elimination unit 80 does not eliminate static electricity, the charge is charged without removing the charging characteristics by the charging unit 3. The charging process is executed again by the unit 3. Therefore, in the image forming apparatus of the first comparative example, there arises a problem that density unevenness caused by the transfer memory occurs from the first sheet of paper. As in the image forming apparatus 100 of the present embodiment, the static elimination unit 80 statically eliminates the photoconductor 2, so that the occurrence of such a problem can be reduced.

<Second Embodiment>
Next, the second embodiment will be described. In the image forming apparatus 100 of the first embodiment, the drive parameter value of the photoconductor 2 to be compared with the first threshold value N1 has been described as "the drive parameter value of the photoconductor 2 in all one job". In the second embodiment, the drive parameter value of the photoconductor 2 to be compared with the first threshold value N1 is "photosensitivity driven to print on a predetermined number of sheets (one sheet in this embodiment) in one job". It is an integrated value of the drive parameter values of the body 2. Further, let N be the number of sheets of paper on which the image is printed in the input job. Also, let n be the variable for the number of sheets of paper. Further, in the present embodiment, the predetermined number is assumed to be "1". As a modification, the predetermined number may be "a number of 2 or more".

FIG. 8 is a flowchart of processing of the control device 18 of the second embodiment. After the end of step S102, in step S202, the specific unit 204 sets the number of printed sheets n as the initial value (1 in the present embodiment). Next, in step S204, the specific unit 204 specifies the unit drive parameter value An of the photoconductor 2 for printing on the nth sheet (secondary transfer to the nth sheet). Here, the "unit drive parameter value" is a "drive parameter value for driving the photoconductor 2 required for printing an image on one sheet of paper".

Next, in step S206, the unit drive parameter value An specified in step S204 is set with respect to "the integrated value ΣAn-1 of the drive parameter values of the photoconductor 2 on the first to n-1 sheets of paper". to add. As a result, the specifying unit 204 can calculate (identify) "the integrated value ΣAn of the driving parameter values of the photoconductor 2 on the first to nth sheets of paper".

Next, in step S208, the setting unit 206 determines whether or not the integrated value ΣAn is larger than the first threshold value N1. When the setting unit 206 determines that the integrated value ΣAn is larger than the first threshold value N1 (YES in step S208), the process proceeds to step S110. Further, when the setting unit 206 determines that the drive parameter value A is equal to or less than the first threshold value N1 (NO in step S108), the process proceeds to step S112.

When step S110 or step S112 is completed, the process proceeds to step S214. In step S214, the image forming apparatus 100 starts the printing process on one sheet of paper. In step S216, the setting unit 206 determines whether or not n = N has been reached, that is, whether or not printing has been completed for all of the number of prints N specified by the input job. In step S216, when the setting unit 206 determines that n has reached N (n = N) (YES in step S216), the process ends. In step S216, when it is determined that n has not reached N (n <N) (NO in step S216), the setting unit 206 returns to step S204.

According to the image forming apparatus 100 of the second embodiment, the primary transfer current can be switched from the second current value I2 to the first current value I1 during the execution of the input job. For example, in FIG. 8, the setting unit 206 determines that the integrated value ΣAn of the unit drive parameter value of the photoconductor 2 is larger than the first threshold value N1 during the execution of the input job (in step S208). NO) The primary transfer current is set to the second current value I2. Therefore, the image forming apparatus 100 can improve the secondary transfer efficiency without causing density unevenness caused by the transfer memory. After that, the setting unit 206 determines that the integrated value ΣAn of the unit drive parameter value of the photoconductor 2 is larger than the first threshold value N1 during the execution of the job (YES in step S208), and then the primary transfer current. Is set to the second current value I2. Therefore, the image forming apparatus 100 can prevent the density unevenness caused by the transfer memory from occurring.

Further, in the image forming apparatus of the second embodiment, since the primary transfer current can be changed during one job, flexible switching control of the primary transfer current can be executed.

<Third Embodiment>
In the above-described embodiment, the image forming apparatus 100 has been described as having the static elimination unit 80. The image forming apparatus of the third embodiment does not have the static elimination unit 80. According to the image forming apparatus of the present embodiment, the number of parts can be reduced.

Further, according to the image forming apparatus of the first embodiment and the second embodiment, it has been described that the charging characteristic of the photoconductor is removed by static elimination by the static elimination unit 80. Generally, the photoconductor 2 spontaneously discharges when a predetermined period t elapses from the time when the primary transfer by the primary transfer unit 12A is completed. In the image forming apparatus of the third embodiment, the charging characteristic of the photoconductor is removed by this natural discharge. The predetermined period t is a period in which the charging characteristics of the photoconductor are removed by natural discharge, and is a period determined in advance by an experiment or the like.

Hereinafter, the job accepted by the reception unit 202 is referred to as a “first job”. Further, the job received by the reception unit after the first job by 202 is referred to as a "second job".

FIG. 9 is a diagram for explaining the concept of the job of the present embodiment. FIG. 9A is specified when the period X from the time when the reception unit 202 receives the first job to the time when the reception unit 202 receives the second job is less than the predetermined period t. Part 204 integrates the first job and the second job into "1 job". Further, when the period X until the reception unit 202 receives the second job is a predetermined period t or more, the specific unit 204 sets the second job as "1 job". In this case, the specific unit 204 also sets the first job as "1 job".

When the idea of the third embodiment is applied to the idea of the first embodiment, in step S106 of FIG. 7, the specific unit 204 sets the drive parameter value A based on the job of 1 to the method (A) shown in FIG. ) Or method (B). Further, when the idea of the third embodiment is applied to the idea of the second embodiment, in step S204 of FIG. 8, the specific unit 204 is a unit drive for printing on the nth sheet in the first job. Specify the parameter value An.

Next, the effect of the image forming apparatus of the present embodiment will be described. "In an image forming apparatus that does not have a static elimination unit 80, when the period X is a period less than a predetermined period t, the second job is designated as" 1 job ", and the photoconductor 2 based on the 1 job is used. The "image forming apparatus for specifying the drive parameter" is referred to as the "image forming apparatus of the second comparative example". In the image forming apparatus of the second comparative example, the charging characteristics of the photoconductor 2 are not sufficiently removed when the second job is accepted. Therefore, positive charging characteristics remain in the photoconductor 2. When the primary transfer current is set to the second current value I2 and the secondary transfer unit 13A executes the secondary transfer in a state where the positive charging characteristics remain, the first 2 in the second job In the next transfer, there is a problem that the density unevenness of the transfer memory factor occurs.

Therefore, in the present embodiment, as shown in FIG. 9B, the period X from the time when the reception unit 202 receives the first job to the time when the reception unit 202 receives the second job is a predetermined period. If it is less than t, the specifying unit 204 integrates the first job and the second job to form a "1 job" and specifies a drive parameter value based on the "1 job". Therefore, when the second job is accepted, even if the charging characteristics of the photoconductor 2 are not sufficiently removed, the density unevenness of the transfer memory factor in the secondary transfer of the first sheet in the second job is performed. Can be reduced.

As a modification of the third embodiment, the idea of the third embodiment may be applied to the image forming apparatus having the static elimination unit 80.

<Fourth Embodiment>
The specifying unit 204 of the fourth embodiment specifies the drive parameter value during the period in which the transfer current is flowing through the primary transfer roller 12. FIG. 10 is a diagram showing the relationship between printing on paper (secondary transfer) and the period during which the primary transfer current is output from the primary transfer current output unit 60.

In the example of FIG. 10, each page includes a print portion α and a margin portion β. In the example of FIG. 10, when the printing process is executed on the entire area of one page including the printing portion α and the margin portion β, the control device 18 outputs the primary transfer current to the primary transfer current output unit 60. Let me. On the other hand, the control device 18 transfers the toner image to be printed on the next paper between the first paper and the next paper, that is, when the toner image to be printed on the first paper is first transferred to the intermediate transfer belt 11. The control device 18 does not cause the primary transfer current output unit 60 to output the primary transfer current between the time of primary transfer to the intermediate transfer belt 11. With such a configuration, between the time when the toner image to be printed on one paper is first transferred to the intermediate transfer belt 11 and the time when the toner image to be printed on the next paper is first transferred to the intermediate transfer belt 11. The cost of the primary transfer current can be reduced as compared with the image forming apparatus in which the primary transfer current output unit 60 outputs the primary transfer current. In the example of FIG. 10, the period during which the primary transfer current is output is referred to as the “primary transfer current output period”, and the period during which the primary transfer current is not output is referred to as the “primary transfer current non-output period”.

The identification unit 204 specifies the primary transfer current output period by analyzing the job received by the reception unit 202. Further, the identification unit 204 specifies the drive parameter value of the photoconductor 2 for the specified primary transfer current output period. At the same time, the specific unit 204 does not specify the drive parameter value of the photoconductor 2 for a period other than the specified primary transfer current output period (primary transfer current non-output period).

In the image forming apparatus of the present embodiment, in order to reduce the cost of the primary transfer current, the toner image to be printed on one paper is first transferred to the intermediate transfer belt 11 and the toner to be printed on the next paper. The control device 18 does not cause the primary transfer current output unit 60 to output the primary transfer current between the time when the image is first transferred to the intermediate transfer belt 11. Under such a configuration, the image forming apparatus of the present embodiment specifies the drive parameter value of the photoconductor 2 only in the “primary transfer current output period”. Therefore, the image forming apparatus of the present embodiment is compared with the image forming apparatus that specifies the drive parameter value of the photoconductor 2 in both the “primary transfer current output period” and the “primary transfer current non-output period”. , The exact drive parameter value can be specified.

<Fifth Embodiment>
For example, when the place where the image forming apparatus is installed is hot and humid, even if the drive parameter value A specified by the specific unit 204 is less than the first threshold value N1, the density unevenness of the transfer memory factor may occur. May occur. Therefore, the image forming apparatus of this embodiment has a prohibited portion 210 (see the broken line portion in FIG. 6). The prohibition unit 210 prohibits the setting unit 206 from setting the current value of the primary transfer current to the second current value I2 based on the environment of the place where the image forming apparatus is installed.

Further, the image forming apparatus of this embodiment has an environmental parameter value sensor 110 that detects an environmental parameter value of a place where the image forming apparatus is installed. Environmental parameters include at least one of temperature T, humidity H, and absolute humidity B. That is, the environmental parameter value sensor 110 includes at least one of a temperature sensor that detects the temperature T, a humidity sensor that detects the humidity H, and an absolute humidity sensor that detects the absolute humidity B.

FIG. 11 is an example of the table used by the prohibition unit 210. In the table of FIG. 11, the condition for prohibiting the setting unit 206 from setting the primary transfer current to the second current value I2 is defined. The table of FIG. 11 is a table created in advance, and the table of FIG. 11 is stored in, for example, a storage unit 208.

For example, when the prohibition unit 210 determines that the temperature T detected by the temperature sensor in the environment parameter value sensor 110 is equal to or higher than the temperature threshold value Tk (when the first prohibition condition is satisfied), the prohibition unit 206 determines that the temperature T is equal to or higher than the temperature threshold value Tk. Prohibits setting the primary transfer current to the second current value I2. Further, as a modification, when the prohibition unit 210 determines that the humidity H detected by the humidity sensor in the environmental parameter value sensor 110 is equal to or higher than the humidity threshold value Hk (when the second prohibition condition is satisfied), the prohibition unit 210 determines. The setting unit 206 may be prohibited from setting the primary transfer current to the second current value I2. Further, as a modification, when the prohibition unit 210 determines that the absolute humidity B detected by the absolute humidity sensor of the environmental parameter value sensor 110 is equal to or higher than the absolute humidity threshold value Bk (when the third prohibition condition is satisfied). The setting unit 206 may be prohibited from setting the primary transfer current to the second current value I2.

Even if at least one of the first prohibition condition to the third prohibition condition is satisfied, the setting unit 206 prohibits the setting of the primary transfer current to the first current value I1. Good.

Further, depending on the characteristics of the photoconductor 2, the first prohibition condition may be "a condition that the temperature T is less than the temperature threshold value Tk". Further, the second prohibition condition may be "a condition that the humidity H is less than the humidity threshold value Hk". Further, the third prohibited condition may be "a condition that the absolute humidity B is less than the absolute humidity threshold value Bk".

The image forming apparatus of the present embodiment prohibits the setting unit 206 from setting the current value of the primary transfer current to the second current value I2 based on the environment in which the image forming apparatus is installed. Therefore, the setting of the primary transfer current can be made more detailed.

<Sixth Embodiment>
In the image forming apparatus of the sixth embodiment, as the primary transfer current, in addition to the first current value I1 and the second current value I2, the third current value I3 (see the third current value I3 shown by the broken line in FIG. 6). Can be set. The third current value I3 is higher than the second current value I2.

When the setting unit 206 sets the primary transfer current to the third current value I3, the secondary transfer efficiency is further improved as compared with the case where the setting unit 206 sets the second current value I2. Can be done. Therefore, in the present embodiment, the manufacturer or the like of the image forming apparatus measures the environmental parameters that do not cause density unevenness due to the transfer memory even if the primary transfer current is set to the third current value I3.

FIG. 12 is an example of the table used by the setting unit 206. In the table of FIG. 12, the condition that the setting unit 206 sets the primary transfer current to the third current value I3 is defined. The table of FIG. 12 is a table created in advance, and the table of FIG. 12 is stored in, for example, a storage unit 208.

For example, in the process of step S112, when the setting unit 206 determines that the temperature T detected by the temperature sensor in the environmental parameter value sensor 110 is less than the temperature threshold value Tk2, the setting unit 206 sets the primary transfer current to the second. Set the current value I2. Further, in the process of step S112, when the setting unit 206 determines that the temperature T detected by the temperature sensor in the environmental parameter value sensor 110 is equal to or higher than the temperature threshold value Tk2 (determines that the first setting condition is satisfied). If), the primary transfer current is set to the third current value I3.

Further, as a modification, in the process of step S112, when the setting unit 206 determines that the humidity H detected by the humidity sensor in the environmental parameter value sensor 110 is less than the humidity threshold value Hk2, the primary transfer current May be set to the second current value I2. Further, in the process of step S112, when the setting unit 206 determines that the humidity H detected by the humidity sensor in the environmental parameter value sensor 110 is equal to or higher than the humidity threshold value Hk2 (determines that the second setting condition is satisfied). If this is the case), the primary transfer current may be set to the third current value I3.

Further, as a modification, in the process of step S112, when the setting unit 206 determines that the absolute humidity B detected by the absolute humidity sensor in the environmental parameter value sensor 110 is less than the absolute humidity threshold value Bk2, 1 The next transfer current may be set to the second current value I2. Further, in the process of step S112, when the setting unit 206 determines that the absolute humidity B detected by the absolute humidity sensor in the environmental parameter value sensor 110 is equal to or higher than the absolute humidity threshold value Bk2 (the third setting condition is satisfied). If it is determined that this has been done), the primary transfer current may be set to the third current value I3.

When at least one of the first setting condition to the third setting condition is satisfied, the setting unit 206 may set the primary transfer current to the third current value I3.

Further, depending on the characteristics of the photoconductor 2, the first setting condition may be "a condition that the temperature T is less than the temperature threshold value Tk". In this case, the condition for setting the primary transfer current to the second current value is "a condition that the temperature T is equal to or higher than the temperature threshold value Tk".

Further, the second setting condition may be "a condition that the humidity H is less than the humidity threshold value Hk". In this case, the condition for setting the primary transfer current to the second current value is "a condition that the humidity H is equal to or higher than the humidity threshold value Hk".

Further, the third setting condition may be "a condition that the absolute humidity B is less than the absolute humidity threshold value Bk". In this case, the condition for setting the primary transfer current to the second current value is "a condition that the absolute humidity B is equal to or higher than the absolute humidity threshold value Bk".

In the image forming apparatus of the present embodiment, the setting unit 206 sets the current value of the primary transfer current to the third current value I3 for improving the secondary transfer efficiency, based on the environment in which the image forming apparatus is installed. To do. Therefore, the secondary transfer efficiency can be improved as compared with the image forming apparatus in which the third current value I3 is not set as the current value of the primary transfer current.

As a modification of the sixth embodiment, the setting unit 206 has a current of 1 or more larger than the third current value I3 in addition to the first current value I1, the second current value I2, and the third current value I3. The value may be set. The current value of 1 or more includes, for example, a fourth current value I4 (a current value larger than the third current value I3).

<7th Embodiment>
In the above-described embodiment, it has been described that the threshold value to be compared with the drive parameter value A is one (first threshold value N1).

However, depending on the environment of the image forming apparatus, the number of pages at which density unevenness due to the transfer memory begins to occur may fluctuate. In other words, depending on the environment of the image forming apparatus, the number of printed sheets immediately before the occurrence of density unevenness may fluctuate due to the fluctuation of the curve shown in FIG. Therefore, in the present embodiment, the manufacturer of the image forming apparatus or the like measures the number of prints immediately before the density unevenness occurs in the environmental parameters after the fluctuation according to the environmental parameters (by changing the environmental parameters). To do. Then, the manufacturer of the image forming apparatus or the like measures the threshold value of the photoconductor 2 based on the measured number of printed sheets.

FIG. 13 is an example of the table used by the setting unit 206. In the table of FIG. 13, the condition that the setting unit 206 sets the threshold value to the first threshold value N1 and the condition that the setting unit 206 sets the threshold value to the second threshold value N2 are defined. Further, the first threshold value N1> the second threshold value N2. The table of FIG. 13 is a table created in advance, and the table of FIG. 13 is stored in, for example, a storage unit 208.

For example, in the process of step S112, when the setting unit 206 determines that the temperature T detected by the temperature sensor in the environmental parameter value sensor 110 is less than the temperature threshold value Tk3, the setting unit 206 sets the threshold value to the first threshold value N1. Set. Further, in the process of step S112, when the setting unit 206 determines that the temperature T detected by the temperature sensor in the environmental parameter value sensor 110 is equal to or higher than the temperature threshold value Tk3 (determines that the first threshold value condition is satisfied). If), the threshold value is set to the second threshold value N2.

In step S112, the setting unit 206 compares the set threshold value with the drive parameter value specified by the specific unit 204.

Further, as a modification, in the process of step S112, when the setting unit 206 determines that the humidity H detected by the humidity sensor in the environmental parameter value sensor 110 is less than the humidity threshold value Hk3, the threshold value is set to the first threshold value. The threshold value N1 may be set. Further, as a modification, in the process of step S112, when the setting unit 206 determines that the humidity H detected by the humidity sensor in the environmental parameter value sensor 110 is equal to or higher than the humidity threshold value Hk3 (the second threshold value condition is satisfied). If it is determined that this has been done), the threshold value may be set to the second threshold value N2.

Further, as a modification, in the process of step S112, when the setting unit 206 determines that the absolute humidity B detected by the absolute humidity sensor in the environmental parameter value sensor 110 is less than the absolute humidity threshold value Bk3, the threshold value is set. May be set to the first threshold value N1. Further, as a modification, in the process of step S112, when the setting unit 206 determines that the absolute humidity B detected by the absolute humidity sensor in the environmental parameter value sensor 110 is equal to or higher than the absolute humidity threshold value Bk3 (third threshold value). When it is determined that the condition is satisfied), the threshold value may be set to the second threshold value N2.

When at least one of the first threshold value condition to the third threshold value condition is satisfied, the setting unit 206 may set the threshold value to the second threshold value N2.

Further, depending on the characteristics of the photoconductor 2, the first threshold condition may be "a condition that the temperature T is less than the temperature threshold Tk3". In this case, the condition for setting the threshold value to the first threshold value N1 is "a condition that the temperature T is equal to or higher than the temperature threshold value Tk3".

Further, the second threshold condition may be "a condition that the humidity H is less than the humidity threshold Hk3". In this case, the condition for setting the threshold value to the first threshold value N1 is "a condition that the humidity H is equal to or higher than the humidity threshold value Hk3".

Further, the third threshold condition may be "a condition that the absolute humidity B is less than the absolute humidity threshold Bk3". In this case, the condition for setting the threshold value to the first threshold value N1 is "a condition that the absolute humidity B is equal to or higher than the absolute humidity threshold value Bk3".

In the image forming apparatus of the present embodiment, the setting unit 206 sets either the first threshold value N1 or the second threshold value N2 as the threshold value based on the environment in which the image forming apparatus is installed. Therefore, it is possible to set a finer threshold value as compared with the “image forming apparatus that does not set the second threshold value N2 as the threshold value”. Therefore, as compared with the "image forming apparatus in which the second threshold value N2 is not set as the threshold value", it is possible to improve the secondary transfer efficiency without causing more density unevenness.

<8th Embodiment>
Next, the eighth embodiment will be described. FIG. 14 is a flowchart of processing of the control device 18 of the eighth embodiment. Further, the image forming apparatus of the eighth embodiment uses the first current value I1, the second current value I2, and the third current value I3 described in the sixth embodiment, and the first described in the seventh embodiment. A threshold value N1 and a second threshold value N2 are used. The third current value I3> the second current value I2> the first current value I1, and the first threshold value N1> the second threshold value N2.

In the example of FIG. 14, in step S300, the setting unit 206 determines whether or not the drive parameter value A of the photoconductor 2 specified by the specific unit 204 is larger than the first threshold value N1. If the setting unit 206 determines in step S300 that the drive parameter value A is larger than the first threshold value N1 (YES in step S300), in step S110, the first current value I1 is set as the primary transfer current. Set. If the setting unit 206 determines in step S300 that the drive parameter value A is equal to or less than the first threshold value N1 (NO in step S300), the process proceeds to step S302.

In step S302, the setting unit 206 determines whether or not the drive parameter value A is larger than the second threshold value N2. If the setting unit 206 determines in step S302 that the drive parameter value A is larger than the second threshold value N2 (YES in step S302), in step S112, the second current value I2 is set as the primary transfer current. Set. If the setting unit 206 determines in step S302 that the drive parameter value A is equal to or less than the second threshold value N2 (NO in step S302), the third current value is used as the primary transfer current in step S304. Set I3.

In this way, when the setting unit 206 determines that the drive parameter value A is larger than the first threshold value N1, the setting unit 206 sets the first current value I1 in step S110. Further, when the setting unit 206 determines that the drive parameter value A is equal to or less than the first threshold value N1 and larger than the second threshold value N2, the setting unit 206 sets the second current value I2 in step S112. Further, when the setting unit 206 determines that the drive parameter value A is equal to or less than the second threshold value N2, the setting unit 206 sets the third current value I3 in step S304.

For example, when the drive parameter value A specified by the specific unit 204 is very large, that is, when it is determined that the drive parameter value A is larger than the first threshold value N1, the primary transfer current is set as a large current value. The first current value I1 is set. As a result, the image forming apparatus can prevent the occurrence of density unevenness even when it is determined that the drive parameter value A is very large.

When the drive parameter value A specified by the specific unit 204 is very small, that is, when it is determined that the drive parameter value A is smaller than the second threshold value N2, the third transfer current is the third small current value. The current value I3 is set. Therefore, the image forming apparatus can improve the secondary transfer efficiency while preventing the occurrence of density unevenness.

Further, when the drive parameter value A specified by the specific unit 204 is medium, that is, when it is determined that the drive parameter value A is equal to or less than the first threshold value N1 and larger than the second threshold value N2. The second current value I2 as a medium current value is set as the primary transfer current. Therefore, the image forming apparatus can improve the secondary transfer efficiency while preventing the occurrence of density unevenness.

As a modification of the eighth embodiment, the image forming apparatus may use a threshold value of 2 or more and a current value of 3 or more.

As described above, the image forming apparatus of the present embodiment uses two or more threshold values (first threshold value N1 and second threshold value N2) and three or more current values. Therefore, the primary transfer current can be set more finely as compared with the above-described embodiment.

Further, the first threshold value N1 and the second threshold value N2 may be predetermined, or may be determined according to the environmental parameters of the image forming apparatus.

<9th embodiment>
In the present embodiment, the constituent parts that form a toner image on the photoconductor 2 (support the toner image on the photoconductor 2) are collectively referred to as an image forming unit 70 (see FIG. 6). The image forming unit 70 includes, for example, a charging unit 3, an exposure unit 9, and a developing unit 4.

When the setting unit 206 sets a high current value (second current value I2 or third current value I3), the toner concentration of the secondary transfer by the secondary transfer unit 13A tends to increase. Therefore, in the image forming apparatus of the present embodiment, the current value of the primary transfer current is set to the second current value I2 even when the current value of the primary transfer current is set to the first current value I1. Even in this case, the control for making the toner concentration of the secondary transfer uniform is executed.

The control device 18 of the present embodiment has the function of the condition changing unit 212 shown by the broken line in FIG. The condition changing unit 212 changes the image forming condition of the image forming unit 70 according to the current value set by the setting unit 206. In the present embodiment, when the setting unit 206 sets the primary transfer current to the second current value, the image formation conditions are changed so that the toner concentration of the secondary transfer decreases.

FIG. 15 is an example of changing the image formation conditions when the primary transfer current is set to the second current value. The change in the image formation condition is the first change in the example of FIG. 15 that the amount of charge in the charged portion 3 (charged portion) is increased as compared with the case where the primary transfer current is set to the first current value I1. Including. Further, the change of the image forming condition is a second change in which the exposure intensity of the exposed portion 9 (exposed portion) is weakened as compared with the case where the primary transfer current is set to the first current value in the example of FIG. Including. Further, in the example of FIG. 15, the change of the image forming condition weakens the development bias of the developing unit 4 (developing unit) as compared with the case where the primary transfer current is set to the first current value (absolute value of the developing bias). Includes a third change (to make it smaller). The condition change unit 212 may make at least one of the first change, the second change, and the third change.

Depending on the characteristics of the photoconductor 2, at least one of the first change, the second change, and the third change may be the reverse change. For example, the first change may be to reduce the amount of charge in the charged portion 3 (charged portion) as compared with the case where the primary transfer current is set to the first current value.

Further, as a modification, the condition changing unit 212 changes the image forming condition so that the toner concentration of the secondary transfer increases when the setting unit 206 sets the primary transfer current to the first current value. It may be.

According to the image forming apparatus of the present embodiment, the setting unit 206 changes the image forming conditions so that the toner concentration of the secondary transfer decreases when the primary transfer current is set to the second current value. Therefore, regardless of whether the setting unit 206 sets the primary transfer current to the first current value or the second current value, the toner concentration of the secondary transfer by the secondary transfer unit 13A is uniform. Can be.

<10th Embodiment>
The image forming apparatus of this embodiment has a plurality of color image forming units (image forming units 1A to 1D). Further, black toner, cyan toner, magenta toner, and yellow toner are used for each of the image forming unit 1A to the image forming unit 1D of a plurality of colors. That is, the image forming apparatus has the plurality of primary transfer units 12A corresponding to each of the plurality of colors.

Further, among black toner, cyan toner, magenta toner, and yellow toner, there may be toners of a specific color that are difficult to be charged. For example, it is assumed that the black toner is hard to be charged.

FIG. 16 is a diagram showing colors and the like that change the primary transfer current. As shown in FIG. 16, in the present embodiment, the primary transfer current of the primary transfer unit 12A for the black toner that is difficult to be charged can be set to the second current value I2, while the primary transfer for other toners. It is stipulated that the primary transfer current of part 12A cannot be set to the second current value I2.

For example, in step S112, the setting unit 206 of the present embodiment sets the primary transfer current of the primary transfer unit 12A for the black toner that is difficult to be charged to the second current value I2. On the other hand, the setting unit 206 sets the primary transfer current of the primary transfer unit 12A for toners of other colors to the first current value I1.

If there are two or more toners of a plurality of colors that are difficult to charge, in step S112, the setting unit 206 sets the primary of the primary transfer unit 12A for the two or more toners (toners that are difficult to charge). The transfer current is set to the second current value I2, and the primary transfer current of the primary transfer unit 12A for other toners is set to the first current value I1. That is, the setting unit 206 sets the primary transfer current of at least one primary transfer unit 12A to the second current value I2.

In the image forming apparatus of this embodiment, the primary transfer current of the primary transfer unit 12A for one or more toners that are difficult to be charged is set to the second current value I2. Therefore, it is possible to improve the secondary transfer efficiency of one or more toners that are difficult to be charged.

<Modification example>
Next, a modified example will be described.

(1) The image forming apparatus of the present embodiment has been described as using toners of a plurality of colors. However, the number of colors of the toner may be one. For example, the image forming apparatus may use only black toner.

(2) Further, in the present embodiment, the control device 18 activates the photoconductor 2 when executing a job. Therefore, the expression "activation of the photoconductor 2" may be used to express the idea of the image forming apparatus of the present embodiment. For example, in the method (A) of FIG. 6, from "cumulative drive parameter value of the photoconductor when the job accepted by the reception unit 202 is completed", "cumulative drive of the photoconductor before the reception unit 202 accepts the job". It was explained that "parameter value" is subtracted. For example, this method (A) in the first embodiment can be described from, for example, "when the photoconductor 2 is activated" from "the cumulative drive parameter value of the photoconductor 2 when the job accepted by the reception unit 202 is completed". The cumulative drive parameter value of is subtracted. Further, in the second embodiment, the specific unit 204 performs the process of specifying the unit drive parameter value An from the "cumulative drive parameter value of the photoconductor" to the "cumulative drive parameter when the photoconductor 2 is recently activated". The value may be subtracted. The "cumulative drive parameter value of the photoconductor" is the cumulative drive parameter value for the nth sheet, and the "cumulative drive parameter value when the photoconductor 2 is started most recently" is the cumulative drive parameter value for the n-1th sheet. It is the cumulative drive parameter value of.

"When the photoconductor 2 is recently activated" may be the latest activation of the photoconductor 2 after the driving of the photoconductor is completed for a predetermined period t or more. Further, "when the photoconductor 2 is started most recently" may be "when the photoconductor 2 is started most recently and the charge is removed by the static elimination unit 80". Further, for example, when printing on a large number of sheets (for example, 1000 sheets), the image forming apparatus may execute a temporary stop process for temporarily stopping the printing process during printing. Once the stop process is started, the photoconductor 2 is stopped, but once the stop process is completed (when the printing process is restarted), the photoconductor 2 is started. "When the photoconductor 2 is started most recently" may be "starting the photoconductor 2 when the stop processing is completed".

(3) Further, in the primary transfer of the toner image to which the secondary point is transferred on one page, the setting unit 206 may switch the primary transfer current during the primary transfer. Further, in the primary transfer of the toner image to which the secondary point is transferred to one page, the setting unit 206 is prohibited by the control device 18 or the like from switching the primary transfer current during the primary transfer. It may be.

It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

1A, 1B, 1C, 1D image forming unit, 2 photoconductor, 3 charging part, 4 developing part, 4A developing roller, 5 photoconductor cleaning part, 9 exposure part, 11 intermediate transfer belt, 12 primary transfer roller, 13 2 Secondary transfer roller, 12A primary transfer section, 13A secondary transfer section, 14 paper, 15 cleaning section, 16 paper ejection tray, 17 cassette, 18 control device, 19 exposure control section, 30 fuser, 31 pressure roller, 32 Fixing roller, 32h heating heater, 33 Fixing temperature detector, 36 Paper ejection roller, 38 Reverse transfer path, 50 Operation part, 51 Opposing roller, 52 Cooling roller, 55 Cooler, 60 Primary transfer current output part, 70 Image Unit, 80 static elimination unit, 100 image forming device, 110 environmental parameter value sensor, 202 reception unit, 204 specific unit, 206 setting unit, 208 storage unit, 210 prohibition unit, 212 condition change unit.

Claims (16)

An image carrier that supports a toner image and
With the intermediate transcript,
A primary transfer unit that transfers the toner image carried by the image carrier to the intermediate transfer body by a transfer current, and
A secondary transfer unit that transfers the toner image transferred to the intermediate transfer body to a recording medium, and
The reception department that accepts jobs and
A specific unit that specifies the drive parameter value of the image carrier based on the job accepted by the reception unit, and
Based on the drive parameter value and the predetermined value specified by the specific unit, the current value of the transfer current is set to either the first current value or the second current value larger than the first current value. An image forming apparatus including a setting unit. The image forming apparatus according to claim 1, wherein the specific unit specifies the drive parameter value of the image carrier driven by a job accepted by the reception unit. The specific unit according to claim 1, wherein the integrated value of the unit drive parameter values for each transfer of the toner image to the predetermined number of recording media by the secondary transfer unit is specified as the drive parameter value. Image forming device. The specific unit subtracts the cumulative drive parameter value of the image carrier before the reception unit accepts the job from the cumulative drive parameter value of the image carrier when the job accepted by the reception unit is completed. The image forming apparatus according to any one of claims 1 to 3, wherein the value is specified as the drive parameter value. The image according to any one of claims 1 to 3, wherein the specific unit specifies a drive parameter value of the image carrier driven by a job accepted by the reception unit as the drive parameter value. Forming device. The specific unit includes the first job and the second job when the reception unit receives the second job from the time when the reception unit receives the first job to the time when the predetermined time elapses. The image forming apparatus according to any one of claims 1 to 5, which specifies the driving parameter value of the image carrier based on the job integrated with the job. Further provided with a static elimination unit for statically eliminating the image carrier,
The image according to any one of claims 1 to 5, wherein the specific unit specifies the drive parameter value of the image carrier based on a job after the static elimination unit has statically removed the image carrier. Forming device. The image forming apparatus according to any one of claims 1 to 7, wherein the specific unit specifies the drive parameter value during the period in which the transfer current is output. Any one of claims 1 to 8, further comprising a prohibition unit that prohibits the setting unit from setting the current value of the transfer current to the second current value based on the environment of the image forming apparatus. The image forming apparatus according to the section. Based on the environment of the image forming apparatus, the setting unit sets the current value of the transfer current to either the second current value or the third current value larger than the second current value. The image forming apparatus according to any one of claims 1 to 9. The predetermined value includes a first predetermined value and a second predetermined value smaller than the first predetermined value.
The setting unit
When the drive parameter value is larger than the first predetermined value, the first current value is set.
When the drive parameter value is equal to or less than the first predetermined value and larger than the second predetermined value, the second current value is set.
The image forming apparatus according to claim 10, wherein when the drive parameter value is equal to or less than the second predetermined value, the third current value is set. The setting unit sets the current value of the transfer current to the first current value and the first current value based on the predetermined value based on the environment of the image forming apparatus and the drive parameter value specified by the specific unit. 2. The image forming apparatus according to any one of claims 1 to 11, which is set to any one of the current values. An image-forming portion for image-forming on the image-bearing body is further provided.
The image forming apparatus according to any one of claims 1 to 12, further comprising a condition changing unit that changes the image forming conditions of the image forming unit according to a current value set by the setting unit. It has the plurality of primary transfer portions corresponding to each of the plurality of colors.
The setting unit according to any one of claims 1 to 13, wherein the current value of the transfer current used for at least one of the plurality of primary transfer units is set to the second current value. Image forming device. The driving parameter value is one of the driving amount of the image carrier, the amount of the recording medium on which the image is formed by using the image carrier, and the driving time of the image carrier. The image forming apparatus according to any one of claims 1 to 14. Steps to accept jobs and
The step of specifying the drive parameter value of the image carrier based on the job, and
Based on the drive parameter value and the predetermined value, the current value of the transfer current transferred to the intermediate transfer body is set to either the first current value or the second current value larger than the first current value. A method of controlling an image forming apparatus including a step.

Images