JP2021069043A - Image forming apparatus, image forming method, and program - Google Patents

Abstract

To prevent winding jam of a recording medium in a fixing unit and reduce generation of a thin line and a defective pixel on a print, so as to maintain the balance of light and shade in the entire print image.SOLUTION: An image forming apparatus 100 is an image forming apparatus of an electrophotographic system including fixing means that fixes a toner image to a recording medium, and comprises: an image forming unit 33 that forms the toner image on the recording medium; an image forming condition setting unit 35 that sets an image forming condition for the image forming unit 33 to form the toner image; an edge area detection unit 37 that detects an edge area with a predetermined width from an edge toward a center part of the recording medium; and a gradation generation unit 39 that controls such that the density of the toner image formed in the edge area of the recording medium is gradually increased from the edge toward the center part.SELECTED DRAWING: Figure 2

Description

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

Conventionally, in an MFP (image forming apparatus), there is known a technique of controlling the density of image data related to an edge region of a recording paper when printing on the entire surface of the recording paper.
In such an MFP, an image processing technique for reducing the density of image data related to the edge regions of the four sides by a predetermined amount, or a printing rate in a predetermined length range from the leading edge portion in the transport direction of the recording paper. Based on the above, a technique for reducing the toner concentration by a predetermined amount is installed.

Patent Document 1 and Patent Document 2 are known as examples of such conventional MFPs.
Patent Document 1 discloses a technique for printing with a predetermined amount of toner density reduced by performing image processing for reducing a predetermined amount of image data related to the edge regions of four sides.
In Patent Document 2, based on the printing rate in a predetermined length range from the leading edge of the recording paper in the transport direction, when the printing rate is high, the density in the high density range is reduced to perform image exposure, thereby performing toner. A technique for printing with a predetermined amount of density reduced is disclosed.

Specifically, in Patent Document 1, the toner density is controlled to be reduced by a predetermined amount by performing image processing for reducing the density by a predetermined amount on the image data related to the edge regions of the four sides.
Further, in Patent Document 2, based on the printing rate in a predetermined length range from the leading edge portion of the transfer paper in the transport direction, when the printing rate is high, the density in the high density range is reduced to perform image exposure. By doing so, the toner concentration is controlled to be reduced by a predetermined amount.

However, in Patent Document 1, when the density is reduced by a predetermined amount by using image processing, there is a problem that so-called missing dots occur in which continuous 1-dot lines are interrupted and printed. there were.
Further, in Patent Document 2, there is a problem that when the image exposure is performed by reducing the density in the high density range, the balance of the overall shading is lost with respect to the target image.
The present invention has been made in view of the above, and an object of the present invention is to prevent jamming of a recording medium by a fixing portion, reduce the occurrence of fine lines and missing dots in a printed matter, and shade the entire printed image. Is to maintain the balance of.

The invention according to claim 1 is an electrophotographic image forming apparatus provided with a fixing means for fixing a toner image on a recording medium in order to solve the above problems, and is an image forming apparatus for forming a toner image on the recording medium. The means, the image forming condition setting means for setting the image forming condition for the image forming means to form the toner image, and the edge region having a predetermined width from the edge portion to the central portion of the recording medium are detected. The edge region detecting means and the gradation generating means for controlling the density of the toner image formed in the edge region of the recording medium so as to gradually increase from the edge portion to the center portion are provided. It is characterized by.

According to the present invention, the density of the toner image is gradually increased from the edge portion to the center portion with respect to the edge region of the recording medium, so that the jamming of the recording medium by the fixing portion is prevented and the toner image is prevented from being jammed. It is possible to reduce the occurrence of fine lines and missing dots in the printed matter and maintain the balance of light and shade in the entire printed image.

It is a block diagram which shows the hardware structure of the image forming apparatus provided with the image forming function of this invention. It is a functional block diagram of the image forming apparatus which concerns on one Embodiment of this invention. It is a mechanical schematic block diagram of the printer part of the image forming apparatus which concerns on one Embodiment of this invention. It is a figure which shows the edge region of the recording medium which the image forming apparatus which concerns on one Embodiment of this invention applied the gradation control, and (a) is the figure which shows an example which applied the gradation control only to the leading edge portion. (B) is a diagram showing an example in which gradation control is applied to a front edge portion and a trailing edge portion, and (c) is a diagram showing an example in which gradation control is applied to four sides. It is a figure which shows an example which the image forming apparatus which concerns on one Embodiment of this invention applied the gradation control only to the leading edge part, (a) is a figure which shows an example of the original image, (b) is a recording medium. It is a figure which shows the position of the leading edge part with respect to, and (c) is a figure which shows an example of the printed image which performed the gradation control. It is a figure which compared the printing with a margin in the borderless printing and the normal printing in the present invention, (a) is a figure which shows an example at the time of normal printing with a margin, (b) is an example at the time of borderless printing. It is a figure which shows, and (c) is the figure which shows the detail of the area which performed the gradation control. It is a schematic diagram explaining the image formation process of the image formation apparatus which concerns on one Embodiment of this invention. It is a timing chart for explaining the gradation control by the exposure amount of the image forming apparatus which concerns on one Embodiment of this invention, (a) is the figure which shows the timing of the exposure amount before application of this invention, (b) is the present invention. It is a figure which shows the timing of the exposure amount after application of the invention, (c) is a figure which shows the timing of an image region. It is a timing chart explaining the gradation control by the development bias and charge bias of the image forming apparatus which concerns on one Embodiment of this invention, (a) is the figure which shows the timing of development bias before application of this invention, (b). ) Is a diagram showing the timing of the development bias A after the application of the present invention, (c) is a diagram showing the timing of the development bias B after the application of the present invention, and (d) is a diagram showing the timing of the development bias B after the application of the present invention. It is a figure which shows the timing, (e) is a figure which shows the timing of charge bias A after application of this invention, (f) is a figure which shows the timing of charge bias B after application of this invention, (g). Is a diagram showing the timing of the image area. It is a timing chart for explaining the gradation control by the primary transfer bias of the image forming apparatus which concerns on one Embodiment of this invention, (a) is the figure which shows the timing of the primary transfer bias before application of this invention, (b). Is a diagram showing the timing of the primary transfer bias after the application of the present invention, and (c) is a diagram showing the timing of the image region. It is a timing chart for explaining the gradation control by the secondary transfer bias of the image forming apparatus which concerns on one Embodiment of this invention, and (a) is the figure which shows the timing of the secondary transfer bias before application of this invention. b) is a diagram showing the timing of the secondary transfer bias after the application of the present invention, and (c) is a diagram showing the timing of the image region. It is an operation flowchart of the gradation control of the image forming apparatus which concerns on one Embodiment of this invention.

Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the drawings.
The present invention has the following configuration in order to prevent jamming of the recording medium by the fixing portion, reduce the occurrence of fine lines and missing dots in the printed matter, and maintain the balance of light and shade in the entire printed image.

That is, the image forming apparatus of the present invention is an electrophotographic image forming apparatus provided with fixing means for fixing a toner image on a recording medium, and is an image forming means for forming a toner image on a recording medium and an image forming means. An image forming condition setting means for setting an image forming condition for forming a toner image, an edge area detecting means for detecting an edge region having a predetermined width from the edge portion of the recording medium toward the center portion, and a recording medium. It is characterized by providing a gradation generating means for controlling the density of the toner image formed in the edge region of the image so as to gradually increase from the edge to the center.
By providing the above configuration, the density of the toner image is gradually increased from the edge portion to the center portion with respect to the edge region of the recording medium, so that the jamming of the recording medium by the fixing portion can be prevented. Moreover, it is possible to reduce the occurrence of fine lines and missing dots in the printed matter and maintain the balance of shading of the entire printed image.
The above-mentioned features of the present invention will be described in detail below with reference to the drawings.

<Hardware configuration of image forming device>
FIG. 1 is a block diagram showing a hardware configuration of an image forming apparatus having an image forming function of the present invention.
The MFP (Multifunction Peripheral / Product / Printer) 100 includes a controller 1, a network I / F23, a short-range communication circuit 25, an operation panel 27, and an engine control unit 29.

The hardware configuration of the MFP 100 is not limited to the configuration shown in FIG. For example, the operation panel 27 may be connected to the SB 7 instead of the ASIC 11.

The controller 1 is a CPU 3 which is a main part of a computer, a system memory (MEM-P) 19, a north bridge (NB) 5, a south bridge (SB) 7, an ASIC (Application Specific Integrated Circuit) 11, and a local memory which is a storage unit. It has (MEM-C) 13, an HDD controller 15, and HD17 as a storage unit, and has a configuration in which NB5 and ASIC11 are connected by an AGP (Accelerated Graphics Port) bus 9.

However, the configuration of the controller 1 is not limited to this. For example, two or more components such as CPU3, NB5, and SB7 may be realized by SoC (System on Chip). In this case, the SoC and the ASIC 11 may be connected by a PCI-express (registered trademark) bus.

Of these, the CPU 3 controls the entire MFP 100, and controls, for example, drawing, communication, input from the operation panel 27, and the like.

NB5 is a bridge for connecting CPU3, MEM-P19, SB7, and AGP bus 9, and includes a memory controller that controls reading and writing to MEM-P19, a PCI (Peripheral Component Interconnect) master, and an AGP target. Has.

The MEM-P19 includes a ROM 19a which is a memory for storing programs and data that realizes each function of the controller 1, and a RAM 19b which is used as a memory for developing programs and data and a memory for drawing at the time of memory printing.
The program stored in the RAM 19b is configured to be provided by recording a file in an installable format or an executable format on a computer-readable recording medium such as a CD-ROM, CD-R, or DVD. You may.

The SB7 is a bridge for connecting the NB5 to a PCI device and peripheral devices.
The ASIC 11 is an IC (Integrated Circuit) for image processing applications that has hardware elements for image processing, and has a role of a bridge that connects the AGP bus 9, the PCI bus 21, the HDD controller 15, and the MEM-C13, respectively.

This ASIC 11 is a PCI target and an AGP master, an arbiter (ARB) which is the core of the ASIC 11, a memory controller which controls MEM-C13, and a plurality of DMACs (Direct Memory Access Controllers) which rotate image data by hardware logic and the like. , And a PCI unit that transfers data between the scanner unit 29b and the printer unit 29a via the PCI bus 21.

A USB (Universal Serial Bus) interface or an IEEE 1394 (Institute of Electrical and Electronics Engineers 1394) interface may be connected to the ASIC 11.
The MEM-C13 is a local memory used as a copy image buffer and a code buffer.

The HD17 is a storage for accumulating image data, font data used at the time of printing, and accumulating forms, and controls reading or writing of data to the HD17 according to the control of the CPU 3.

The AGP bus 9 is a bus interface for a graphics accelerator card proposed to speed up graphic processing, and the graphics accelerator card can be speeded up by directly accessing the MEM-P19 with high throughput. .. However, the MEM-C13 may not be installed.

Further, the short-range communication circuit 25 is provided with a short-range communication network 25a. The short-range communication circuit 25 is a communication circuit such as NFC or Bluetooth (registered trademark).
The engine control unit 29 is composed of a printer unit 29a and a scanner unit 29b.

The operation panel 27 displays a current setting value, a selection screen, a replacement procedure, etc., a touch panel that accepts input from the operator, a panel display unit 27a that displays a moving image of the replacement procedure, a density setting condition, and the like. It is provided with an operation panel 27b including a numeric keypad for receiving a set value of a condition related to image formation and a start key for receiving a copy start instruction.

The printer unit 29a or the scanner unit 29b includes an image processing portion such as error diffusion and gamma conversion.
The MFP 100 can be selected by sequentially switching the document box function, the copy function, the printer function, and the facsimile function by using the application switching key on the operation panel 27.

When the document box function is selected, the document box mode is set, when the copy function is selected, the copy mode is set, when the printer function is selected, the printer mode is set, and when the facsimile mode is selected, the facsimile mode is set.

The operation panel 27 includes a display unit such as an LCD for displaying various information and an LED for displaying an operating state by turning on / off, and an input unit having a touch panel and a hard key switch. If the operation panel 27 is provided with a touch panel, the hard key switch may not be provided.

The network I / F23 is an interface for performing data communication using a communication network. The short-range communication circuit 25 and the network I / F23 are electrically connected to the ASIC 11 via the PCI bus 21.

<Functional block of image forming device>
FIG. 2 is a functional block diagram of an image forming apparatus according to an embodiment of the present invention.
The controller 1 controls the entire operation of the MFP 100 by using the RAM as the work memory according to the program stored in the ROM in advance. The controller 1 executes the control unit 31, the image forming unit 33, the image forming condition setting unit 35, the edge area detecting unit 37, the paper feed control unit 38, and the gradation generation unit 39 according to the program stored in the ROM in advance. ..
The control unit 31 controls all the controls by the program stored in the ROM 19a. The control unit 31 controls the image forming unit 33, the image forming condition setting unit 35, the edge region detection unit 37, the paper feed control unit 38, and the gradation generation unit 39.
The control unit 31 sets the image forming conditions for the image forming unit 33 to form the toner image by the image forming condition setting unit 35 with respect to the edge region detected by the edge region detecting unit 37, and sets the floor. The tone generation unit 39 controls the density of the toner image formed in the edge region of the recording medium so as to gradually increase from the edge portion to the center portion.

The image forming unit 33 is composed of a printer unit 29a described later, and forms a toner image on the entire surface of the recording medium by using the image forming apparatus 100.
Further, when forming a toner image on the entire surface of the recording medium, the image forming unit 33 sets a predetermined amount of space between the sheets of the recording medium. This stabilizes the bias and enables continuous printing without borders.

The image forming condition setting unit 35 sets the image forming condition for the image forming unit 33 to form the toner image in the control unit 31. That is, the image forming condition setting unit 35 faces the edge region, and the control unit 31 switches the exposure amount when the image forming unit 33 forms the electrostatic latent image on the photoconductor 51 (FIG. 3). Set to.
The image formation condition setting unit 35 controls to switch at least one or more output values of a charge bias, a development bias, a primary transfer bias, and a secondary transfer bias for forming a toner image so as to face the edge region. Set in unit 31.
The image formation condition setting unit 35 sets the output value of the secondary transfer bias 41E to the control unit 31 between the time when the drawing ends and the time when the next drawing starts.

The image formation condition setting unit 35 sets the output value of the exposure amount in the control unit 31 before a predetermined time at the start of drawing.
Further, the image forming condition setting unit 35 uses the exposure amount of the writing light emitted by the exposure unit 53 and the charging roller 52 to change the density of the image in the edge region detected by the edge region detection unit 37. Predetermined drawing starts of the output values of the charging bias applied, the development bias applied by the developing roller 55, the primary transfer bias applied by the primary transfer roller 41D, and the secondary transfer bias applied by the secondary transfer roller 41E. Launch before time. That is, the image formation condition setting unit 35 sets the output value of the exposure amount in the control unit 31 before a predetermined time at the start of drawing.

The control unit 31 has the following features.
(1) The control unit 31 sets the exposure amount of the writing light to the exposure unit 53 provided in the printer unit 29a by using the exposure amount set by the image formation condition setting unit 35.
(2) The control unit 31 includes a first DC / DC converter that converts the voltage supplied from the 12V system power supply or the 24V system power supply into a high voltage, and sets the charging bias value set by the image formation condition setting unit 35. The DC voltage generated by the first DC / DC converter is applied to the charging roller 52 as a charging bias.
(3) The control unit 31 includes a second DC / DC converter that converts the voltage supplied from the 12V system power supply or the 24V system power supply into a high voltage, and sets the development bias value set by the image formation condition setting unit 35. The DC voltage generated by the second DC / DC converter is applied to the development roller 55 as a development bias.
(4) The control unit 31 includes a third DC / DC converter that converts the voltage supplied from the 12V system power supply or the 24V system power supply into a high voltage, and the primary transfer bias value set by the image formation condition setting unit 35. Is used to apply the DC voltage generated by the third DC / DC converter to the primary transfer roller 41D as the primary transfer bias.
(5) The control unit 31 includes a fourth DC / DC converter that converts the voltage supplied from the 12V system power supply or the 24V system power supply into a high voltage, and the secondary transfer bias set by the image formation condition setting unit 35. Using the value, the DC voltage generated by the fourth DC / DC converter is applied to the secondary transfer roller 41E as the secondary transfer bias. At this time, the control unit 31 starts up the fourth DC / DC converter before a predetermined time from which the output value of the secondary transfer bias is started to be drawn.

Further, the image forming condition setting unit 35 has at least one or more of the exposure amount, the charge bias, the development bias, and the transfer bias in order to change the density of the image of the edge region detected by the edge region detection unit 37. Change the output value step by step.
The image formation condition setting unit 35 sets the output value of the development bias in the control unit 31 after the exposure start point on the photoconductor 51 reaches the application position D of the development bias.
The image formation condition setting unit 35 sets the output value of the charging bias in the control unit 31 before the charging start point on the photoconductor 51 reaches the exposure start point.
The image formation condition setting unit 35 sets the output value of the primary transfer bias 41D to the control unit 31 after the exposure start point on the photoconductor 51 reaches the application position C of the primary transfer bias 41D.

The image formation condition setting unit 35 controls the control unit 31 so that the density of the toner image in the trailing edge region region gradually increases toward the central portion in the sub-scanning direction.
The image formation condition setting unit 35 sets the control unit 31 so that only the exposure amount changes when the density of the toner image in one or more edge regions of the left and right edge regions of the recording medium is changed.
Further, when the image formation condition setting unit 35 changes the density of the image of the trailing edge region detected by the edge region region detection unit 37 with respect to the control unit 31, the density of the image of the detected trailing edge region is changed. Control so that the edges are dark and thin toward the center.
Further, the image formation condition setting unit 35 sets the control unit 31 to change only the exposure amount when changing the image density of the edge region of all four sides detected by the edge region detection unit 37.

The edge region detection unit 37 detects an edge region having a predetermined width from the edge portion of the recording medium toward the center portion.
The edge region detection unit 37 is a leading edge region and / and a trailing edge region in the sub-scanning direction of the recording medium, and / and a left edge region and / and a right edge region in the main scanning direction of the recording medium. Is detected.

The paper feed control unit 38 controls so as to open a predetermined amount of paper feed interval between the recording medium and the recording medium to be fed next to the recording medium. That is, by opening the space between the papers during borderless printing, the bias is stabilized and continuous printing without borders is possible.

The gradation generation unit 39 controls the density of the image of the edge region detected by the edge region detection unit 37 so that the edge portion is thin and the edge portion becomes darker toward the center portion. That is, the gradation generation unit 39 divides the exposure amount into scanning line units or a certain area to switch the exposure amount.

<Mechanical configuration of the printer section of the image forming apparatus>
FIG. 3 is a mechanical configuration diagram of a printer unit of an image forming apparatus according to an embodiment of the present invention.
The printer unit 29a of the image forming apparatus shown in FIG. 3 is an example of the configuration of a four-color full-color printing machine. The printer unit 29a may perform gradation control so that the edge portion is thin and dark toward the center portion with respect to the edge region during four-sided borderless printing, and is a single-color printing machine or a plurality of other printers. It can also be applied to color printing machines.
Further, the printer unit 29a is a process cartridge 42C, 42M, 42Y, 42K for each color of C (cyan), M (magenta), Y (yellow), and K (black) (exposure unit 53, photoconductor 51, respectively). It has a charging roller 52 and a developing unit 54), an intermediate transfer unit 41, and a heat fixing device 59.

The exposure unit 53 includes a polygon motor, a polygon mirror, an Fθ lens, a laser diode, a mirror, and the like.
Further, the exposure unit 53 emits the writing light of each color modulated based on the image data of each color from the laser diode to the polygon mirror rotationally driven by the polygon motor.
The exposure unit 53 deflects the writing light in the main scanning direction by a polygon mirror, passes it through an fθ lens, a mirror, or the like, and as shown by a broken line arrow in FIG. 3, charging rollers 52Y, 52M, 52C, The photoconductors 51Y, 51C, 51M, and 51K uniformly charged by 52K are irradiated to form an electrostatic latent image on the photoconductors 51Y, 51C, 51M, and 51K of each color.

The intermediate transfer unit 41 includes an intermediate transfer belt 41F, a tension roller 41C, a secondary transfer drive roller 41G, a transfer roller 41D for each color of CMYK, and the like.
In the intermediate transfer unit 41, an intermediate transfer belt 41F formed in an endless band shape and a ring shape is stretched to a secondary transfer drive roller 41G and a tension roller 41C stretched in a substantially horizontal direction. The secondary transfer drive roller 41G is arranged in a state of being in contact with the secondary transfer roller 41E with the intermediate transfer belt 41F interposed therebetween.

In the printer unit 29a, CMYK process cartridges 42Y, 42M, 42C, and 42K are arranged along the intermediate transfer belt 41F. Each process cartridge 42Y, 42M, 42C, 42K is centered on the photoconductors 51Y, 51M, 51C, 51K which are rotationally driven in the counterclockwise direction in FIG. 3, and the charging rollers 52Y, 52M, 52C, 52K, and the developing / toner storage. It is housed in the cartridge case with the parts and cleaning parts arranged.
The process cartridges 42Y, 42M, 42C, and 42K are mounted in a state where the photoconductors 51Y, 51M, 51C, and 51K are in contact with the transfer rollers 41D for each color with the intermediate transfer belt 41F interposed therebetween.
In the printer unit 29a, the intermediate transfer belt 41F is conveyed between the photoconductors 51Y, 51M, 51C, 51K of the process cartridges 42Y, 42M, 42C, and 42K and the transfer roller 41D.

The printer unit 29a rotates the photoconductors 51Y, 51M, 51C, and 51K on which the electrostatic latent image is formed counterclockwise, and uses the developing / toner storage unit to apply toner (recording agent) of each color to the photoconductors 51Y, 51C. , 51M, 51K to develop an electrostatic latent image.
The printer unit 29a sequentially superimposes and transfers the color toner images on the intermediate transfer belt 41F by the transfer roller 41D on the photoconductors 51Y, 51C, 51M, and 51K on which the toner images (recording agent images) of each color are formed. Form.
The printer unit 29a further rotates the photoconductors 51Y, 51C, 51M, and 51K for which the transfer of the toner image has been completed to remove the residual toner in the cleaning unit, and then charges the photoconductors 52Y, 52M, 52C, and 52K again. And use it for image formation.

The intermediate transfer belt 41F is rotationally driven counterclockwise by the secondary transfer drive roller 41G, and the toner is transferred to the paper 58 transferred from the resist roller to and from the secondary transfer roller 41E at the secondary transfer drive roller 41G portion. Transfer the image.

In the case of printing only black, the printer unit 29a retracts the transfer rollers other than the black transfer roller 41D to positions separated from the photoconductors 51Y, 51C, and 51M, respectively, to form an image.

Further, the printer unit 29a forms a pattern image on the intermediate transfer belt 41F in order to perform calibration processing such as predetermined color shift correction processing and density adjustment processing, and detects this pattern image with the calibration sensor 43. To do. As the calibration sensor 43, for example, a reflection type optical sensor is used, and the position and density of the pattern image formed on the intermediate transfer belt 41F by the process cartridges 42Y, 42M, 42C, and 42K are detected.

The heat fixing device 59 includes a fixing roller 59a and a pressure roller 59b, sandwiches the paper 58 between the fixing roller 59a and the pressure roller 59b, heats and pressurizes the paper 58 while conveying the paper 58, and heats and pressurizes the paper 58 on the paper 58. The toner image of No. 1 is fixed on the paper 58, and the fixed paper 58 is conveyed.

<Rim area of recording medium>
FIG. 4 is a diagram showing an edge region of a recording medium to which the image forming apparatus according to the embodiment of the present invention has applied gradation control, and FIG. 4A is an example in which gradation control is applied only to the leading edge portion. (B) is a diagram showing an example in which gradation control is applied to the front edge portion and the trailing edge portion, and (c) is a diagram showing an example in which gradation control is applied to four sides.

FIG. 4A is a diagram in which gradation control is applied to the leading edge portion 61 of the recording medium 63 when recording the entire surface. That is, in the leading edge portion 61 of the recording medium 63 for electrophotographic printing, the density of the edge portion 61a is thin, and the toner concentration is adjusted to a predetermined amount by controlling the gradation density so that the density is increased at 61b toward the central portion. It is possible to provide an image forming apparatus 100 that reduces and prevents fixing wrapping jam, reduces the occurrence of fine lines and dot omissions of the recording medium 63, and maintains the balance of shading of the entire printed image.

FIG. 4B is a diagram in which gradation control is applied to the leading edge portion 61 and the trailing edge portion 65. That is, the density of the leading edge portion 61 is as described with reference to FIG. 4A, and the density of the gradation density is controlled so that the density of the edge portion 65a of the trailing edge portion 65 is low and becomes darker at 65b toward the central portion. By performing this, the toner density is reduced by a predetermined amount even during double-sided printing to prevent fixing wrapping jam, and the occurrence of fine lines and dot omissions on the recording medium 63 is reduced to balance the shading of the entire printed image. The held image forming apparatus 100 can be provided.
At the time of double-sided printing, the rear end 65 of the recording medium 63 is printed as the front end in the paper ejection direction.

FIG. 4C is a diagram in which gradation control is applied to the four sides of the leading edge portion 61, the trailing edge portion 65, the left side edge portion 67, and the right side edge portion 69, and the leading edge portion 61 and the trailing edge portion 65 are shown in FIG. 4 (a) and (b) are as described. The gradation control of the left edge portion 67 is similar to the gradation control of the leading edge portion 61 and the trailing edge portion 65, and the density of the edge portion 67a is low in the left edge portion 67 of the recording medium 63 for electrophotographic printing. The gradation density is controlled so that it becomes darker at 67b toward the center.

Further, the gradation control of the right edge portion 69 is similar to the gradation control of the front edge portion 61 and the trailing edge portion 65, and the edge portion 69a is thin in the right edge portion 69 of the recording medium 63 for electrophotographic printing. The gradation density is controlled so that it becomes darker at 69b toward the center. However, when the gradation control is applied to the four sides, it is applied only when the gradation control is changed by controlling the exposure amount. That is, it is only the exposure amount that can change the output value of the hardware in the main scanning direction, and therefore the gradation of the left and right edges is performed in the main scanning direction.

<An example in which gradation control is applied only to the tip edge>
FIG. 5 is a diagram showing an example in which the image forming apparatus according to the embodiment of the present invention applies gradation control only to the leading edge portion, and FIG. 5A is a diagram showing an example of an original image, and FIG. 5B is a diagram showing an example. ) Is a diagram showing the position of the leading edge portion with respect to the recording medium, and (c) is a diagram showing an example of a printed image to which gradation control is applied.
FIG. 5A is a diagram in which the original image 73 is printed on the recording medium 71, and the original image 73 is printed on the upper part of the recording medium 71.
FIG. 5B is a diagram showing the position of the leading edge portion 75 with respect to the recording medium 71, and shows a range in which a predetermined region at the tip of the recording medium 71 applies gradation control.
FIG. 5C is a diagram showing an example of the printed image 73a to which the gradation control is performed, and the density density of the gradation is controlled so that the density of the edge portion is thin and becomes darker toward the center portion. I understand that.

<Borderless printing and printing with margins in normal printing>
6A and 6B are diagrams comparing printing with margins in borderless printing and normal printing in the present invention, FIG. 6A is a diagram showing an example of normal printing with margins, and FIG. 6B is borderless printing. It is a figure which shows an example of time, (c) is a figure which shows the detail of the area which performed the gradation control.
In FIG. 6A, the image is printed with margins 83 provided on the four sides of the recording medium 81, and gradation control is not performed anywhere.
In FIG. 6B, by printing an image on the entire surface of the recording medium 81, there is no margin at each leading edge portion, and gradation control is applied to the leading edge portion 85.
In FIG. 6C, it can be seen that the gradation control of the leading edge portion 85 changes the gradation with respect to the gradation region 87 in five stages a to e. In this example, the gradation region 87 is divided at regular intervals, and the exposure amount, transfer bias, and other values are changed for each of the divided regions (a to e).
The gradation region 87 may be realized by changing the value of the exposure amount for each scanning line.

<Image formation process>
FIG. 7 is a schematic diagram illustrating an image forming process of an image forming apparatus according to an embodiment of the present invention.

In FIG. 7, for simplification of the description, each component is schematically arranged and illustrated.
That is, the exposure position of the photoconductor 51 is A, the charging bias position of the charging roller 52 is B, the primary transfer bias position of the primary transfer roller 41D is C, the development bias position of the developing unit 54 is D, and the secondary transfer roller 41E is secondary. Let E be the next transfer bias position.

Further, the distance from the exposure position A of the photoconductor 51 to the development bias position D of the developing unit 54 is a, the distance from the charge bias position B of the charging roller 52 to the exposure position A of the photoconductor 51 is b, and the photoconductor 51. The distance from the exposure position A to the primary transfer bias position C of the primary transfer roller 41D is c, and the distance from the exposure position A of the photoconductor 51 via the primary transfer bias position C of the primary transfer roller 41D is passed to the secondary of the secondary transfer roller 41E. Let d be the distance to the next transfer bias position E.

Hereinafter, the image forming process of the image forming apparatus will be described. In addition, in FIG. 7, in order to simplify the description, the case of one color will be described.

The photoconductor 51 rotates in the direction of arrow X, the transfer belt 41F moves in the direction of arrow Y according to the rotation of the photoconductor 51, and the recording paper 58 moves in the direction of arrow Z in response to the movement of the transfer belt 41F. To do.
First, the surface of the photoconductor 51 is uniformly charged by the charging roller 52. Then, when the charging start point reaches the exposure point A, it is exposed by the modulated beam light, and an electrostatic latent image is formed on the photoconductor 51.

When the electrostatic latent image formed on the photoconductor 51 reaches the point D, a development bias is applied by the developing roller 55, and a toner image is formed on the photoconductor 51.
When the toner image on the photoconductor 51 reaches point C, a primary transfer bias is applied by the primary transfer roller 41D, and the toner image is transferred to the transfer belt 41F. The transferred toner image is transferred to the recording paper 58 by applying a secondary transfer bias by the secondary transfer roller 41E. After that, the toner image is fixed on the recording paper 58 by the heat fixing device 59.

<Gradation control by exposure amount>
FIG. 8 is a timing chart for explaining gradation control based on the exposure amount of the image forming apparatus according to the embodiment of the present invention, and FIG. 8A is a diagram showing the timing of the exposure amount before applying the present invention. , (B) are diagrams showing the timing of the exposure amount after applying the present invention, and (c) is a diagram showing the timing of the image region.
The solid line indicates the method of controlling the exposure amount, and the broken line indicates the change in the actual exposure amount.

FIG. 8A shows a change in the exposure amount when the present invention is not applied, and the exposure amount does not change until the print job is completed after rising from zero to a constant value A.
In FIG. 8B, the control unit 31 causes the printer unit 29a to raise the exposure amount from the point D before the drawing start point B and maintain the exposure amount from the drawing start points B to the E point.
After that, the control unit 31 controls the printer unit 29a so that the exposure amounts of E, F, and G gradually increase and maintain a constant value at the G point. At this time, the amount that gradually increases may be one scanning unit or a plurality of scanning units. When the drawing is completed (point C), the exposure amount is reduced to the point D after a predetermined time. The exposure amount is controlled in the same manner below.
FIG. 8C shows the timing of the image area, and one image area is from the drawing start point B to the drawing end point C.

<Gradation control by development bias and charging bias>
FIG. 9 is a timing chart for explaining the gradation control by the development bias and the charging bias of the image forming apparatus according to the embodiment of the present invention, and FIG. 9A shows the timing of the development bias before applying the present invention. It is a figure, (b) is a figure which shows the timing of development bias A after applying this invention, (c) is a figure which shows the timing of development bias B after applying this invention.
9 (d) is a diagram showing the timing of charging bias before applying the present invention, (e) is a diagram showing the timing of charging bias A after applying the present invention, and (f) is a diagram showing the present invention. It is a figure which shows the timing of the charge bias B after applying the invention. (G) is a figure which shows the timing of an image area.

FIG. 9A shows a change in the development bias when the present invention is not applied, and the development bias applied by the development roller 55 does not change until the development bias rises from zero to a constant value A and the print job is completed.

In FIG. 9B, the control unit 31 causes the printer unit 29a to raise the development bias A from the point E before the drawing start point B and maintain the development bias A from the drawing start point B to the F point.
After that, the control unit 31 controls the printer unit 29a to gradually increase the development bias voltage in steps of F, G, and H so as to maintain a constant value at the H point. Here, the distance a (FIG. 7) from the exposure position on the photoconductor to the development position is shown between points B and C.
At this time, the amount that rises stepwise is divided into a certain region and rises. When drawing is completed (point D), the development bias voltage is lowered to point E after a predetermined time. Similarly, the development bias voltage applied by the development roller 55 is controlled.

In FIG. 9C, the control unit 31 raises the development bias B from the point I before the drawing start point B with respect to the printer unit 29a and maintains the development bias B up to the drawing start point J.
After that, the control unit 31 increases the development bias voltage stepwise with respect to the printer unit 29a in K, L, and M so as to exceed the next drawing start point so as to maintain a constant value at the M point. Control.
At this time, the amount that rises stepwise is divided into a certain region and rises. When drawing is completed (point D), the development bias voltage is lowered to point J after a predetermined time. Similarly, the development bias voltage is controlled.

FIG. 9D shows a change in the charging bias when the present invention is not applied, and the charging bias applied by the charging roller 52 does not change until the printing job is completed after rising from zero to a constant value A.

In FIG. 9E, the control unit 31 causes the printer unit 29a to raise the charging bias A from the point E before the drawing start point C and maintain the charging bias A from the drawing start point C to the F point.
After that, the control unit 31 controls the printer unit 29a to gradually increase the charge bias voltage in steps of F, G, and H so as to maintain a constant value at the H point. Here, the distance between the points B and C indicates the distance from the charged position on the photoconductor to the exposed position (distance b in FIG. 7).
At this time, the amount that rises stepwise is divided into a certain region and rises. When the drawing is completed (point D), the charging bias voltage is lowered to the point E after a predetermined time. Similarly, the charging bias voltage applied by the charging roller 52 is controlled.

In FIG. 9 (f), the control unit 31 raises the charging bias B from the point I before the drawing start point C to the printer unit 29a, maintains it up to the point J, and once drops to the point K thereafter. , K, L, and M, the charging bias voltage is gradually increased, and is controlled so as to exceed the next drawing end point D so as to maintain a constant value at the point M.
At this time, the amount that rises stepwise is divided into a certain region and rises. When drawing is completed (point D), the charging bias voltage is lowered to point J after a predetermined time. Similarly, the charging bias voltage is controlled.

FIG. 9 (g) shows the timing of the image area, and one image area is from the drawing start point B to the drawing end point C.

<Gradation control by primary transfer bias>
FIG. 10 is a timing chart for explaining gradation control by the primary transfer bias of the image forming apparatus according to the embodiment of the present invention, and FIG. 10A is a diagram showing the timing of the primary transfer bias before applying the present invention. (B) is a diagram showing the timing of the primary transfer bias after applying the present invention, and (c) is a diagram showing the timing of the image region.

FIG. 10A shows the voltage change of the primary transfer bias when the present invention is not applied, and the primary transfer bias applied by the primary transfer roller 41D rises stepwise from zero to a constant value A to C for drawing. It does not change until it finishes. Here, between points B and D, the distance from the exposed position on the photoconductor to the primary transfer position (distance c in FIG. 7) is shown.

In FIG. 10B, the control unit 31 causes the printer unit 29a to raise the primary transfer bias from the point F before the drawing start point B and maintain the printer unit 29a from the drawing start point B to the G point.
After that, the control unit 31 controls the printer unit 29a to gradually increase the primary transfer bias voltage in steps of G and H so as to maintain a constant value at the H point.
At this time, the amount that rises stepwise is divided into a certain region and rises. When drawing is completed (point E), the primary transfer bias voltage is lowered to point F after a predetermined time. Similarly, the primary transfer bias voltage applied by the primary transfer roller 41D is controlled.

FIG. 10C shows the timing of the image area, and one image area is from the drawing start point B to the drawing end point E.

<Gradation control by secondary transfer bias>
FIG. 11 is a timing chart for explaining gradation control by the secondary transfer bias of the image forming apparatus according to the embodiment of the present invention, and FIG. 11A shows the timing of the secondary transfer bias before applying the present invention. It is a figure which shows, (b) is a figure which shows the timing of the secondary transfer bias after applying this invention, (c) is a figure which shows the timing of an image region.

FIG. 11A shows the voltage change of the secondary transfer bias when the present invention is not applied, and the secondary transfer bias applied by the secondary transfer roller 41E rises from zero to a constant value B, and the print job is completed. It doesn't change until it does.
Here, the distance between the points A and E indicates the distance from the exposure position on the photoconductor to the secondary transfer position (distance d in FIG. 7).

In FIG. 11B, the control unit 31 gradually raises the secondary transfer bias from the E point to the H point after a predetermined time from the drawing end point I with respect to the printer unit 29a, and sets a constant value at the H point. Control to maintain. At this time, the amount that rises stepwise is divided into a certain region and rises.
When the control unit 31 starts the next drawing on the printer unit 29a (point D), the control unit 31 reduces the secondary transfer bias voltage to zero after a predetermined time. Similarly, the secondary transfer bias voltage applied by the secondary transfer roller 41E is controlled.

FIG. 11C shows the timing of the image area, and one image area is from the drawing start point A to the drawing end point I.

<Gradation control>
FIG. 12 is an operation flowchart of gradation control of the image forming apparatus according to the embodiment of the present invention.
Note that FIG. 12 describes a case where a primary transfer bias is set as an image formation condition for gradation control.

In step S1, when the user instructs the start of printing, the control unit 31 receives the request.

In step S3, the control unit 31 determines whether or not borderless printing is set. This setting is set by the user in advance. If borderless printing is not set (NO in step S3), the process proceeds to step S15, and if borderless printing is set (YES in step S3), the process proceeds to step S5.

In step S5, the control unit 31 determines a predetermined amount of the edge region by the edge region detection unit 37. Here, a value set in advance in the memory area of the image forming apparatus 100 is used as a predetermined amount of edge area.

In step S7, the control unit 31 determines the number of gradation control divisions set in advance in the memory area of the image forming apparatus 100 by the gradation generation unit 39.

In step S9, the control unit 31 divides the tip region according to a predetermined number of divisions, and raises the primary transfer bias applied by the primary transfer roller 41D.

In step S11, the control unit 31 detects the start of writing.
In step S13, after detecting the start of writing, the control unit 31 elapses for each predetermined number of divisions after a lapse of time corresponding to the movement of the distance from the exposure position A to the primary transfer position C on the photoconductor 51. Gradation control is realized by changing the output value of the primary transfer bias.

On the other hand, in step S15, the control unit 31 performs normal printing with a margin.
It is also possible to set arbitrary values for the "predetermined amount of the edge region" and the "number of divisions of the gradation control" that are set in the memory area of the image forming apparatus 100 in advance.

In addition, in step S13, the control unit 31 may realize the present invention by changing the exposure amount, the charging bias value applied by the charging roller 52, and the development bias value applied by the developing roller 55. It is possible.

<Supplementary explanation related to gradation control>
In this embodiment, when gradation control is performed in the sub-scanning direction, only the exposure amount can be realized. On the other hand, when gradation control is performed in the main scanning direction, it can be realized by the exposure amount, transfer bias, and charge development bias.

<Structure, Action, Effect of Examples of Embodiments of the Present Invention>
<First aspect>
The image forming apparatus 100 of this embodiment is an electrophotographic image forming apparatus provided with fixing means for fixing a toner image on a recording medium, and is an image forming unit 33 for forming a toner image on a recording medium and an image forming unit. An image formation condition setting unit 35 for setting image formation conditions for the 33 to form a toner image, and an edge region detection unit 37 for detecting an edge region having a predetermined width from the edge portion to the center portion of the recording medium. The feature is that the gradation generation unit 39 is provided to control the density of the toner image formed in the edge region of the recording medium so as to gradually increase from the edge portion to the center portion.
According to this aspect, the image forming condition setting unit 35 sets the image forming condition for the image forming unit 33 to form the toner image with respect to the edge region detected by the edge region detecting unit 37. The gradation generation unit 39 controls the density of the toner image formed in the edge region of the recording medium so as to gradually increase from the edge portion to the center portion.
As a result, the density of the toner image is gradually increased from the edge portion to the center portion with respect to the edge region of the recording medium, so that the jamming of the recording medium by the fixing portion is prevented and the fine lines of the printed matter are prevented. It is possible to reduce the occurrence of missing dots and to maintain the balance of shading of the entire printed image.

<Second aspect>
The image forming condition setting unit 35 of the present embodiment is characterized in that the exposure amount for forming an electrostatic latent image on the photoconductor is switched so as to face the edge region.
According to this aspect, in order to change the density of the image in the edge region, the exposure amount when the image forming unit 33 forms an electrostatic latent image on the photoconductor is changed.
As a result, gradation control of the edge region can be realized by controlling the exposure amount of the hardware, and as a result, the toner density can be reduced.

<Third aspect>
The gradation generation unit 39 of this embodiment is characterized in that the exposure amount is divided into scanning line units or a certain area to switch the exposure amount.
According to this aspect, it is possible to prevent the exposure amount from being switched when one scanning line is exposed by switching in units of scanning lines or in a certain area. As a result, it is possible to prevent the printed image from appearing to have horizontal stripes in the scanning line direction in the portion where the density is switched.

<Fourth aspect>
The image forming condition setting unit 35 of this embodiment switches the output value of at least one or more of the charging bias, the developing bias, the primary transfer bias, and the secondary transfer bias for forming the toner image so as to face the edge region. It is characterized in that it is set as follows.
According to this aspect, in order to change the density of the image, the output value of any one or more of the charge bias, the development bias, and the transfer bias is changed. As a result, it is possible to perform four-sided borderless printing without causing fine lines or missing dots in the printed matter and without disturbing the balance of shading of the entire printed image, while reducing the toner density by a predetermined amount to prevent jamming due to fixing and wrapping. .. In addition, it is possible to perform four-sided borderless printing without causing fine lines or missing dots in the printed matter and without disturbing the balance of shading of the entire printed image.

<Fifth aspect>
The image forming apparatus 100 of this embodiment is characterized by including a paper feed control unit 38 that controls a predetermined amount of paper feed interval between the recording medium and the recording medium to be fed next to the recording medium. ..
According to this aspect, bias can be stabilized by opening a space between papers during borderless printing, and continuous printing without borders can be performed.

<Sixth aspect>
The edge region detection unit 37 of this embodiment is a leading edge region and / and a trailing edge region of the recording medium in the sub-scanning direction, and / and a left edge region of the recording medium in the main scanning direction, and / and right. It is characterized by detecting an edge region.
According to this aspect, the edge region for which gradation control is performed is controlled not only for the front edge of the paper but also for the other three edges, and as a result, the toner concentration is reduced by a predetermined amount and the fixing wrapping is performed. It is possible to perform four-sided borderless printing without causing jamming, causing fine lines and missing dots in the printed matter, and without disturbing the balance of shading of the entire printed image.

<7th aspect>
The image forming condition setting unit 35 of this embodiment is characterized in that the output value of the exposure amount is set in the image forming unit 33 before a predetermined time at the start of drawing.
According to this aspect, since the output value of the exposure amount is set before a predetermined time at the start of drawing, the exposure can be stabilized.

<8th aspect>
The image forming condition setting unit 35 of this embodiment is characterized in that the output value of the development bias is set after the exposure start point on the photoconductor 51 reaches the application position D of the development bias.
According to this aspect, since the output value of the development bias is set after the exposure start point on the photoconductor 51 reaches the application position D of the development bias, the development bias can be stabilized.

<9th aspect>
The image forming condition setting unit 35 of this embodiment is characterized in that the output value of the charging bias is set until the charging start point on the photoconductor 51 reaches the exposure start point.
According to this aspect, since the output value of the charging bias is set before the charging start point on the photoconductor 51 reaches the exposure start point, the charging bias can be stabilized.

<10th aspect>
The image forming condition setting unit 35 of this embodiment is characterized in that the output value of the primary transfer bias 41D is set after the exposure start point on the photoconductor 51 reaches the application position C of the primary transfer bias 41D.
According to this aspect, since the output value of the primary transfer bias 41D is set after the exposure start point on the photoconductor 51 reaches the application position C of the primary transfer bias 41D, the primary transfer bias can be stabilized. it can.

<11th aspect>
The image formation condition setting unit 35 of the present embodiment is characterized in that the output value of the secondary transfer bias 41E is set between the end of drawing and the start of the next drawing.
According to this aspect, since the output value of the secondary transfer bias 41E is set between the end of drawing and the start of the next drawing, the secondary transfer bias can be stabilized.

<12th aspect>
The image forming condition setting unit 35 of this embodiment is characterized in that at least one or more output values of exposure amount, charging bias, development bias, and transfer bias are changed stepwise so as to face the edge region. ..
According to this aspect, since the output values of the exposure amount, the charge bias, the development bias, and the transfer bias are changed stepwise, the actual increase in the bias value becomes gradual.

<13th aspect>
The image forming condition setting unit 35 of this embodiment is characterized in that the density of the toner image in the trailing edge region is controlled so as to increase stepwise toward the sub-scanning direction.
According to this aspect, the density of the detected image of the trailing edge region is controlled so that the edge portion is dark and the image density is reduced toward the central portion. That is, since the rear end of the recording medium is printed as the tip in the paper ejection direction during double-sided printing, the fixing winding jam is also printed during double-sided printing by printing the rear end of the recording medium as the tip in the paper ejection direction. Can be prevented.

<14th aspect>
The image forming condition setting unit 35 of this embodiment is characterized in that when the density of the toner image in one or more edge regions of the left and right edge portions of the recording medium is changed, only the exposure amount is changed. ..
According to this aspect, when changing the density of the image in the edge region of all four sides, only the exposure amount is changed. That is, since the density of the left and right edge regions is changed with respect to the main scanning direction, it is necessary to change the density depending on the exposure amount.
This makes it possible to change the density of the image in the edge region of all four sides.

<15th aspect>
The image forming method of this embodiment is an image forming method by an electrophotographic image forming apparatus 100 provided with a fixing means for fixing a toner image on a recording medium, and includes an image forming step of forming a toner image on a recording medium. An image formation condition setting step for setting image formation conditions for forming a toner image by the image formation step, and an edge region detection step for detecting an edge region having a predetermined width from the edge portion to the center portion of the recording medium. The feature is that the gradation generation step for controlling the density of the toner image formed in the edge region of the recording medium so as to gradually increase from the edge portion to the center portion is provided.
According to this aspect, the image formation condition setting unit 35 sets the number of gradation control divisions for the edge region detected by the edge region detection unit 37, and determines the density of the image in the edge region. The part is thin and is controlled to gradually increase toward the central part.
By the above operation, it is possible to provide an image forming method in which the toner concentration is reduced by a predetermined amount to prevent fixing wrapping jam, and the occurrence of fine lines and missing dots in the printed matter is reduced to maintain the balance of shading of the entire printed image. be able to.

<16th aspect>
The program of this aspect is characterized in that the processor executes each step in the image forming method described in the fifteenth aspect.
According to this aspect, each step can be executed by the processor.
It is possible to provide an image forming apparatus that reduces the toner concentration by a predetermined amount to prevent jamming due to fixing and wrapping, and reduces the occurrence of fine lines and missing dots in the printed matter to maintain the balance of shading of the entire printed image.

1 ... controller, 3 ... CPU, 5 ... north bridge (NB), 7 ... south bridge (SB), 11 ... ASIC, 13 ... local memory (MEM-C), 15 ... HDD controller, 17 ... HD, 19 ... system Memory (MEM-P), 25 ... Short-range communication circuit, 27 ... Operation panel, 29a ... Printer unit, 29b ... Scanner unit, 31 ... Control unit, 33 ... Image forming unit, 35 ... Image forming condition setting unit, 37 ... Edge area detection unit, 38 ... Paper feed control unit, 39 ... Gradation generation unit

JP-A-2007-31207 JP-A-2005-157035

Claims (16)

An electrophotographic image forming apparatus provided with a fixing means for fixing a toner image on a recording medium.
An image forming means for forming a toner image on the recording medium, and
An image forming condition setting means for setting an image forming condition for the image forming means to form the toner image, and an image forming condition setting means.
An edge region detecting means for detecting an edge region having a predetermined width from the edge portion to the central portion of the recording medium, and
A gradation generating means for controlling the density of the toner image formed in the edge region of the recording medium so as to gradually increase from the edge to the center.
An image forming apparatus characterized by being provided with. The image according to claim 1, wherein the image forming condition setting means is set so as to switch the exposure amount for forming an electrostatic latent image on the photoconductor so as to face the edge region. Forming device. The image forming apparatus according to claim 2, wherein the gradation generating means switches the exposure amount in units of scanning lines or by dividing into a certain area. The image forming condition setting means is opposed to the edge region so as to switch at least one or more output values of a charging bias, a developing bias, a primary transfer bias, and a secondary transfer bias for forming a toner image. The image forming apparatus according to claim 1, wherein the image forming apparatus is set. Any one of claims 1 to 4, further comprising a paper feed control means for controlling a predetermined amount of paper feed interval between the recording medium and the recording medium to be fed next to the recording medium. The image forming apparatus according to the section. The edge region detecting means is a leading edge region and / and a trailing edge region of the recording medium in the sub-scanning direction, and / and a left edge region and / and a right edge of the recording medium in the main scanning direction. The image forming apparatus according to claim 1, wherein a partial region is detected. The image forming apparatus according to claim 1, wherein the image forming condition setting means sets an output value of the exposure amount to the image forming means before a predetermined time at the start of drawing. The image forming condition setting means according to claim 1 or 4, wherein the output value of the development bias is set after the exposure start point on the photoconductor reaches the application position of the development bias. Image forming device. The image according to claim 1 or 4, wherein the image forming condition setting means sets the output value of the charging bias until the charging start point on the photoconductor reaches the exposure start point. Forming device. The image forming condition setting means is characterized in that the output value of the primary transfer bias is set after the exposure start point on the photoconductor reaches the application position of the primary transfer bias. The image forming apparatus according to. The image forming apparatus according to claim 1 or 4, wherein the image forming condition setting means sets an output value of the secondary transfer bias between the drawing end time point and the next drawing start time point. The image forming condition setting means is characterized in that at least one or more output values of the exposure amount, the charging bias, the developing bias, and the transfer bias are changed stepwise so as to face the edge region. The image forming apparatus according to any one of claims 2 to 4. The image forming according to claim 6, wherein the image forming condition setting means controls the density of the toner image in the trailing edge region so as to gradually increase toward the central portion in the sub-scanning direction. apparatus. The claim is characterized in that when the density of the toner image in one or more edge regions of the left and right edge regions of the recording medium is changed, the image forming condition setting means is set so that only the exposure amount is changed. Item 6. The image forming apparatus according to item 6. An image forming method using an electrophotographic image forming apparatus provided with a fixing means for fixing a toner image on a recording medium.
An image forming step of forming a toner image on the recording medium, and
An image formation condition setting step for setting an image formation condition for forming a toner image by the image formation step, and an image formation condition setting step.
An edge region detection step for detecting an edge region having a predetermined width from the edge portion to the center portion of the recording medium, and
A gradation generation step that controls the density of the toner image formed in the edge region of the recording medium so as to gradually increase from the edge to the center.
An image forming method characterized by being provided with. A program comprising causing a processor to execute each step in the image forming method according to claim 15.

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