JP2019159056A - Image forming apparatus - Google Patents

Abstract

To prevent the occurrence of filming on an image carrier while reducing toner consumption.SOLUTION: The image forming apparatus comprises: an image carrier, such as an intermediate transfer belt 45 that carries a toner image on a surface; a cleaning member, such as a cleaning blade 22 that removes the toner image on the surface of the image carrier; a pixel number counting unit 550 that counts the number of pixels per predetermined period for each of areas A1, A2, ... in a main scanning direction W of the image carrier; and toner supply control means 560 that supplies a toner to the image carrier for each of the areas on the basis of the number of pixels counted by the pixel number counting unit 550.SELECTED DRAWING: Figure 7

Description

  The present invention relates to an image forming apparatus.

  In an electrophotographic image forming apparatus, filming in which additives such as toner and paper are deposited in a thin film may occur on the surface of an image carrier that carries a toner image as the apparatus is used. In order to remove the generated filming, it is known to supply toner to a cleaning member that contacts the surface of the image carrier and cleans residual toner and the like. Further, Japanese Patent Application Laid-Open No. 2004-133830 discloses a configuration in which a toner image is formed and entered into an area where there is a risk of turning over for the purpose of preventing the cleaning blade from turning up.

In the conventional configuration, the toner image is supplied to the contact area between the cleaning member and the image carrier. However, since the toner image is executed regardless of the occurrence of filming, the removal of filming is performed at an appropriate timing. Difficult to do. Further, in the technique of Patent Document 1, toner is supplied to a position where filming does not occur, so that toner is wasted.
The present invention has been made in view of the above-described circumstances, and an object thereof is to prevent the occurrence of filming on an image carrier while suppressing toner consumption.

  In order to achieve the above object, an image forming apparatus according to the present invention includes an image carrier that carries a toner image on the surface, a cleaning member that removes the toner image on the surface of the image carrier, and main scanning of the image carrier. A pixel number counting unit that counts the number of pixels per predetermined period for each region in the direction, and a toner supply control unit that supplies toner to the image carrier for each region based on the pixel count value by the pixel number counting unit. It is a feature.

  According to the present invention, filming on the image carrier can be prevented while suppressing toner consumption.

1 is a schematic configuration diagram of a color printer as an image forming apparatus according to an embodiment of the present invention. FIG. 4 is a diagram illustrating a driving system and a belt cleaning configuration of an intermediate transfer unit. FIG. 3 is a perspective view for explaining an arrangement of a drive system and a line sensor of an intermediate transfer unit. The top view explaining the reading range of a line sensor. Sectional drawing explaining the structure of a line sensor. FIG. 2 is a control block diagram illustrating a main control configuration of the color printer of FIG. 1. The block diagram which shows the structure of the control system of a trimming removal. FIG. 3 is a plan view of a main part showing a density adjustment toner pattern formation position and a line sensor arrangement position on an intermediate transfer belt. The flowchart which shows an example of the execution content of filming removal mode. The figure which plotted the accumulation pixel number for every area | region in a fixed travel distance area. FIG. 5 is a configuration diagram of a main part of an image forming unit and an intermediate transfer unit showing a configuration and operation of another form of a filming removal mode.

  Hereinafter, embodiments of the present invention including examples will be described in detail with reference to the drawings. In each embodiment, components (members and components) having the same function, shape, and the like will be omitted by giving the same reference numerals after being described once unless there is a possibility of confusion.

First, the main configuration of an image forming apparatus according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus shown in FIG. 1 is a color printer 1 of a quadruple tandem type intermediate transfer system that forms a color image from toners of four colors of yellow, magenta, cyan, and black. In the figure, Y, M, C, and K are subscripts assigned to components related to yellow, magenta, cyan, and black colors.
The color printer 1 is provided with a new toner storage portion 19 for individually storing four colors of new toner at an upper portion on the front side of an image forming apparatus main body (hereinafter referred to as “apparatus main body”) 2 that is a housing. ing.

In the substantially central portion of the apparatus main body 2, there are four image forming units 3Y, 3M, 3C, and 3K that form image forming portions for forming respective single color toner images from four color toners, and a belt unit that is a transfer device. A certain intermediate transfer unit 4 is arranged. The image forming units 3Y, 3M, 3C, and 3K each constitute a process cartridge and are disposed below the intermediate transfer unit 4.
Below the image forming units 3Y, 3M, 3C, and 3K, an optical writing unit 5 as an exposure unit is disposed. The optical writing unit 5 includes a light source, a polygon mirror, an f-θ lens, a reflecting mirror, and the like, and irradiates exposure light based on image data. Note that the color order of Y, M, C, and K is not limited to that shown in FIG.

  The image forming units 3Y, 3M, 3C, and 3K are drum-shaped photoreceptors 30Y as latent image carriers on which electrostatic latent images are formed by exposure light such as laser light emitted from the optical writing unit 5, respectively. 30M, 30C, 30K.

Since the four image forming units 3Y, 3M, 3C, and 3K have the same configuration, the image forming unit 3Y will be described as a representative. The image forming unit 3Y includes a charging device 31Y as a charging unit, a developing device 32Y as a developing unit, a cleaning device 33Y as a cleaning unit, and a charge eliminating unit around the photoreceptor 30Y. The arrangement of the image forming units 3Y, 3M, 3C, and 3K is set so that the rotation axes of the photoconductors 30Y, 30M, 30C, and 30K are parallel and arranged at a predetermined pitch in the transfer sheet moving direction. ing.
The image forming units 3Y, 3M, 3C, and 3K perform the electrophotographic process by using the above-described apparatuses and units, so that each of the image forming units 3Y, 3M, 3C, and 3K is monochromatic on the photoreceptors 30Y, 30M, 30C, and 30K The toner image is formed.
In the following description, if there is no need to describe the color of the toner to be used, the subscripts for yellow (Y), magenta (M), cyan (C), and black (K) are omitted. In the present embodiment, the number of photoconductors, that is, the number of image forming units, which are also called image forming units, is four, but is not limited to this, and may be five or more.

  The developing device 32 is a two-component developing type developing device that differs only in the color of the toner to be used. In the developing device 32, a developer containing toner and a magnetic carrier is accommodated. The developing device 32 includes a developing roller facing the photoconductor 30, a screw for conveying and stirring the developer, a toner concentration sensor, and the like. The developing roller is composed of an outer rotatable sleeve and an inner magnet.

The intermediate transfer unit 4 includes a belt driving device having an intermediate transfer belt 45 that conveys the toner images formed by the respective image forming units so as to be superimposed and transferred. The intermediate transfer belt 45 is an intermediate transfer member made of an endless belt member, and functions as an image carrier that carries a toner image.
The intermediate transfer belt 45 is rotatably wound around support rollers 41, 42, 43, and 44 as a plurality of rotation support members. When the support roller 44 is driven as a driving roller in the counterclockwise direction, the intermediate transfer belt 45 is rotationally driven in the direction of arrow W1 (belt running direction) in FIG.
The intermediate transfer belt 45 has a multilayer structure. The base layer is formed of, for example, a fluororesin, PVD sheet, or polyimide resin that has little elongation, and the surface is covered with a smooth coating layer such as a fluororesin. Become.

In the vicinity of the support roller 44, a tension roller 40 that presses against the surface of the intermediate transfer belt 45 and applies tension to the intermediate transfer belt 45 is disposed.
In this embodiment, the number of support rollers for supporting the intermediate transfer belt 45 is four, but the present invention is not limited to this, and two or more rollers that are necessary for rotationally driving the intermediate transfer belt 45 are provided. If it is.

Inside the intermediate transfer belt 45, primary transfer rollers 6Y, 6M, 6C, and 6K for transferring a toner image to the intermediate transfer belt 45 are disposed to face the photoreceptors 30Y, 30M, 30C, and 30K. The primary transfer rollers 6Y, 6M, 6C, and 6K bring the intermediate transfer belt 45 into contact with the photoreceptors 30Y, 30M, 30C, and 30K by a well-known primary contact / separation mechanism so that the primary transfer portions 7Y, 7M, 7C, and 7K are moved. The transfer position can be moved to a standby position where the intermediate transfer belt 45 is separated from the photoreceptors 30Y, 30M, 30C, and 30K.
On the right side of the intermediate transfer unit 4 in the drawing, a secondary transfer roller 9 as a secondary transfer member for transferring a toner image onto a sheet P as a sheet-like recording medium is disposed. The secondary transfer roller 9 is configured to be able to contact and separate between a secondary transfer position that forms a secondary transfer portion and a separated position that is separated from the secondary transfer position. This contact / separation mechanism includes a compression spring that urges the secondary transfer roller 9 in a direction to press the secondary transfer position and a solenoid that displaces the secondary transfer roller 9 to the separation position against the urging force of the compression spring. This is performed by a well-known secondary contact / separation mechanism configured in combination. Above the secondary transfer roller 9, a fixing unit 12 for fixing the sheet P on which an unfixed toner image is formed by applying heat and pressure is disposed.

  On the intermediate transfer belt 45 near the support roller 41, a belt cleaning unit that removes and cleans residual toner that could not be transferred to the intermediate transfer belt 45, and a toner image including a toner patch or a solid image that is a reference pattern to be described later. 20 is provided. The detailed configuration of the belt cleaning unit 20 will be described later.

  A line sensor 610 is disposed between the secondary transfer roller 9 and the belt cleaning unit 20 downstream in the driving direction of the intermediate transfer belt 45 at a position facing the intermediate transfer belt 45. The line sensor 610 is used for measurement of image forming performance that is performed at a predetermined timing. In the measurement of the image forming performance, the line sensor 610 detects the reference pattern formed on the intermediate transfer belt 45 by the above-described image forming unit as image data, and outputs the number of pixels to the control unit 500 as pixel number data. Means.

  At the bottom of the apparatus main body 2 is provided a paper feed cassette 10 on which a sheet-like recording medium and transfer paper or paper (hereinafter, described as “paper”) P as a transfer medium is placed. Yes. The paper feed cassette 10 is provided with a roller group 11 that feeds and separates the paper P on the paper feed cassette 10. The apparatus main body 2 is also provided with a manual feed tray for manually feeding paper from the side of the color printer 1.

  In addition to the above-described configuration, the color printer 1 includes a new toner storage unit 19 that stores four toner supply containers corresponding to four colors in the apparatus main body 2, and the image forming unit is rotated by each rotation of the toner supply container. Each color toner is supplied to the 3Y, 3M, 3C, and 3K developing devices 32Y, 32M, 32C, and 32K.

The operation of the color printer 1 will be described while supplementing the configuration as appropriate.
The photoreceptors 30Y, 30M, 30C, and 30K are rotationally driven in the clockwise direction while contacting the surface of the intermediate transfer belt 45, respectively. First, the photoconductor 30Y of the image forming unit 3Y positioned at the most upstream is charged with a predetermined voltage from a power source to the charging roller of the charging device 31Y and charged to a predetermined polarity by the charging roller. The light-modulated laser beam emitted from the writing unit 5 according to the image data is irradiated, and an electrostatic latent image is written.
As a result, an electrostatic latent image is formed on the photoconductor 30Y. When the surface of the photoconductor 30Y carrying the electrostatic latent image reaches the developing device 32Y, the surface of the photoconductor 30Y is developed by the developing roller disposed opposite to the photoconductor 30Y. Yellow toner is supplied to the electrostatic latent image to be visualized as a yellow toner image.

The above operation is similarly performed at a predetermined timing in the photoconductors 30M, 30C, and 30K of the other image forming units 3M, 3C, and 3K, and toner images of a predetermined color are respectively formed on the surfaces of the photoconductors 30M, 30C, and 30K. Is formed. The toner images on the respective photoconductors are sequentially primary transferred onto the intermediate transfer belt 45 by the primary transfer unit 7 at the image forming operation timing of the image forming unit. The primary transfer of the toner image is performed by applying a voltage having a polarity opposite to that of the toner on the photoconductor from the power source to the primary transfer roller 6 disposed opposite to each photoconductor with the intermediate transfer belt 45 interposed therebetween. . That is, the primary transfer unit 7 is supplied with a transfer bias for primary transfer. The application of the primary transfer voltage may be AC superimposition.
In this way, the toner images are sequentially superimposed on the intermediate transfer belt 45 to be primarily transferred, and the four color superimposed toner images are carried on the intermediate transfer belt 45. The transfer residual toner adhering to each photoconductor 30 after the toner image primary transfer is removed by the cleaning device 33.

A sheet P as a recording medium and as a transfer medium is conveyed from either the sheet feed cassette 10 or the manual feed tray, and once reaches the pair of registration rollers 17, the sheet P is stopped and the skew is corrected. The paper P is conveyed to the secondary transfer unit 8 by the rotation of the registration roller 17 in accordance with the image forming operation timing described above. The secondary transfer portion 8 is a nip between a portion where the intermediate transfer belt 45 is supported by the support roller 44 and the secondary transfer roller 9 disposed so as to be opposed thereto. The secondary transfer roller 9 is pressed against the support roller 44 via the intermediate transfer belt 45 and is driven to rotate clockwise while contacting the surface of the intermediate transfer belt 45.
The four color toner images superimposed on the intermediate transfer belt 45 are transferred onto the paper P by the secondary transfer unit 8 where the secondary transfer roller 9 and the intermediate transfer belt 45 are in contact with each other. The secondary transfer of the toner image is performed by applying a voltage having a polarity opposite to that of the toner image on the intermediate transfer belt 45 from the power source to the secondary transfer roller 9. That is, a transfer bias for secondary transfer is supplied to the secondary transfer unit 8. The application of the secondary transfer voltage may be AC superimposition.

The sheet P is transported to the fixing unit 12 by the rotational transport of the secondary transfer roller 9 and the intermediate transfer belt 45 while being sandwiched by the secondary transfer unit 8.
In the fixing unit 12, a fixing roller and a pressure roller are in contact with each other. A halogen heater is provided inside the fixing roller, and power is supplied from the power source to the heater so that the surface of the fixing roller has a predetermined temperature. The unfixed toner image on the sheet P is fixed on the sheet P by heat and pressure from the fixing roller at the fixing nip. The sheet P on which the toner image is fixed is conveyed to the pair of paper discharge rollers 15 by the rotation conveyance of the fixing nip.
In the case of single-sided printing, the paper P on which the toner image has been fixed is discharged and stacked on a discharge tray 14 outside the apparatus by a discharge roller 15 toward a discharge outlet 13. In the case of duplex printing, the sheet is conveyed to the duplex unit by each conveyance roller.

The drive system, belt cleaning configuration, and line sensor of the intermediate transfer unit 4 will be described with reference to FIGS. FIG. 2 is a diagram showing a drive system and belt cleaning configuration of the intermediate transfer unit 4, and FIG. 3 is a perspective view for explaining the drive system of the intermediate transfer unit 4 and the arrangement of line sensors. In FIG. 3, the tension roller 40 is omitted for the sake of simplicity.
On the intermediate transfer belt 45 after the secondary transfer, filming (film-like additive) in which additives such as toner and paper are deposited in a thin film shape is generated with time, including toner that could not be transferred. . A belt cleaning unit 20 is provided in the intermediate transfer unit 4 to clean the residue containing the film-like additive.
As shown in FIG. 2, the belt cleaning unit 20 includes a cleaning blade 22 that contacts the surface of the intermediate transfer belt 45, a transport screw 24 that transports the toner scraped off by the cleaning blade 22 to the outside, the cleaning blade 22, and the transport And a cleaning case 21 for accommodating the screw 24.
A backup roller 26 is disposed on the opposite side of the portion where the cleaning blade 22 contacts the intermediate transfer belt 45. The cleaning blade 22 functions as a cleaning member that removes and cleans residual toner that could not be transferred to the intermediate transfer belt 45, a toner image including a toner patch that is a reference pattern to be described later, and a solid image, and filming.

As shown in FIG. 3, the intermediate transfer unit 4 includes a belt drive motor 211 as a drive source for rotationally driving a support roller 44 that is a drive roller to move the intermediate transfer belt 45 endlessly. In the vicinity of the support roller 44, a position information detecting sensor 213 as a position detecting means / position detecting member for detecting the position of the intermediate transfer belt 45 and the toner image in the sub scanning direction W1 is disposed. The position information detection sensor 213 is composed of a transmissive photosensor.
The position information detection sensor 213 detects the rotation speed and rotation position of the support roller 44 in combination with the rotation of the slit plate 212 that is an encoder provided on the shaft of the support roller 44. As a result, position information in the sub-scanning direction W1 of the toner image carried on the surface of the intermediate transfer belt 45 is detected.

Of the entire area of the intermediate transfer belt 45 in the circumferential direction, the line sensor 610 is disposed above the support roller 44 and the upper stretched surface wound around the support roller 41 so as to face the front surface 45a of the intermediate transfer belt 45. Has been. The line sensor 610 extends in a main scanning direction (belt width direction) W orthogonal to the sub-scanning direction W1, and a plurality of light sources, condenser lenses, and light receiving elements are arranged in the main scanning direction W as shown in FIG. It consists of an array structure arranged in a straight line. In FIG. 3, the hatched portion indicates the background portion 45 b in the image forming area on the front surface 45 a of the intermediate transfer belt 45.
Here, the background portion 45b of the intermediate transfer belt 45 refers to a portion on the surface of the intermediate transfer belt 45 where a toner image is not formed (non-image portion) or a portion where no toner image is formed in an image forming portion. Specifically, it refers to a portion on the side of the intermediate transfer belt 45 with respect to a portion that is charged on the photosensitive member and capable of writing exposure but not exposed.

The reading range of the line sensor 610 and the configuration of the line sensor 610 will be described with reference to FIGS. FIG. 4 is a plan view illustrating the reading range of the line sensor 610, and FIG. 5 is a cross-sectional view illustrating the configuration of the line sensor 610.
Since the line sensor 610 is configured to be arranged in a plurality of straight lines as described above, as shown in FIG. 4, the background portion 45b in the main scanning direction W is divided into an arbitrary number ((A1), (A2). (An)) can be read. For this reason, the line sensor 610 has an advantage that it is possible to detect filming unevenness generated on the surface of each of the divided regions of the intermediate transfer belt 45 and the number of pixels of the toner image on the surface.

For example, as shown in FIG. 5, the line sensor 610 is arranged in the main scanning direction W with one light source 611 made of an LED as a light emitting element that emits white light, and reflects reflected light of red, green, and blue. The three light receiving elements 612R, 612G, and 612B that receive light and the light receiving lens 613 are supported by a casing 614 as one cell. In the present embodiment, the line sensor 610 uses a contact image sensor (CIS) that is one of color sensors. As the line sensor 610, a CCD image sensor may be used instead of the CIS. Further, as a light source, a light source of three colors (red, green, blue) may be used instead of one color of a white light source (LED).
The line sensor 610 made of CIS has an amplifier for each unit cell arranged in a straight line in the main scanning direction W, and suppresses generation of electrical noise due to reading of an electrical signal optically converted by the light receiving elements 612R, 612G, and 612B. It has been. This electrical signal is input to the control unit 500 of FIG. 6 described later as pixel number information.
As the pixel number detection means, not the line sensor 610 but a form in which individual image reading sensors are arranged in rows for each region divided into an arbitrary number, or one sensor unit is moved in the main scanning direction W by a moving mechanism. It may be a moving sensor that moves. In other words, any form can be used as long as the front surface 45a of the intermediate transfer belt 45 is regarded as a plurality of areas in the main scanning direction W and the detected information can be output as information on the number of pixels associated with the area information. Absent.

The control system of the color printer will be described with reference to FIG. FIG. 6 is a control block diagram showing the main control configuration of the color printer. The color printer 1 shown in FIG. 1 includes a control unit 500 shown in FIG. The control unit 500 includes a CPU (Central Processing Unit) 501, a RAM (Random Access Memory) 502 that stores various data, a ROM (Read Only Memory) 503 that stores a control program and various data, and a timer 504 that serves as a measurement unit. It has. Various peripheral devices are connected to the control unit 500 via a signal line 510. FIG. 6 shows only major ones of these peripheral devices.
The CPU 501 functions as a control unit. A RAM 502 is backed up by a battery, and is a non-volatile memory that stores and saves the amount of toner consumed by the image forming units 3Y, 3M, 3C, and 3K even when the main power of the color printer 1 in FIG. 1 is turned off. Function.

The control unit 500 includes image forming units 3Y, 3M, 3C, and 3K, a line sensor 610, a belt drive motor 211, a position information detection sensor 213, a belt cleaning unit 20, a drive unit 214 of the optical writing unit 5, a primary connection. A primary transfer solenoid 217, a secondary transfer roller solenoid 218, and various power supply units 216 provided in the separation mechanism and the secondary separation mechanism are connected via a signal line 510.
The various sensors output the detected or detected value to the control unit 500, and the control unit 500 stores the input various values in the RAM 502.

  As main control target drive units of the image forming units 3Y, 3M, 3C, and 3K, a photoconductor drive motor 50 that rotationally drives the photoconductor 30 and a charging roller power supply unit 51 that applies a voltage to the charging roller of the charging device 31. And a developing device driving unit 52 that drives the developing device 32, a cleaning device driving unit 53 that drives the cleaning device 33, and the like.

The control unit 500 controls the printing operation according to the image information by the color printer based on the control program stored in the ROM 503, and as the measurement of the image forming performance described in FIG. The color misregistration correction mode and the removal mode are configured to be executable.
In the image density adjustment mode (process control), apart from the normal image forming operation, as shown in FIG. 8, density adjustment toner patterns Kp, Cp, Mp, and Yp are formed as detection toner images, and the intermediate transfer belt is formed. 45 is transferred. The density adjustment toner pattern is detected by the line sensor 610, and the density adjustment as described above is performed based on the detection result. The density adjustment toner pattern formed in the image density adjustment mode may be used in the removal mode.
In the color misregistration correction mode, a color misregistration correction toner pattern as a detection toner image is formed in an inclined state in the main scanning direction separately from the normal image forming operation, and is transferred onto the intermediate transfer belt 45. The color misregistration correction toner pattern is detected by the line sensor 610, and the misregistration in the main scanning direction and the sub scanning direction is corrected based on the detection result.

The line sensor 610 adjusts the output so that the output when the background portion 45b of the intermediate transfer belt 45 is read is constant. That is, the line sensor 610 also functions as a background portion detection unit in the removal mode and functions as a pixel number detection unit.
The CPU 501 compares the initial output value If0 of the line sensor 610 stored in the RAM 502 with the current output value If, and if the current output value is higher than the set value stored in the ROM 503 in advance. In addition to the image forming operation of transferring images to normal paper P and forming an image, a predetermined toner image is formed and removed by the belt cleaning unit 20 (hereinafter also referred to as “removal mode”).

Here, differences from the conventional configuration will be described.
In image density adjustment and color misregistration correction control used in an electrophotographic image forming apparatus, the density and position of a detection toner pattern created on a photosensitive drum or an intermediate transfer belt are read and corrected by an optical sensor. ing. For example, in image density adjustment (process control), light emitted from a light emitting element of a reflective optical sensor is reflected by a background portion of the intermediate transfer belt on which toner is not attached, and the reflected light is received by a light receiving element. The amount of light received according to the reflected light is obtained.
Next, a reference toner image (density adjustment toner pattern) having a predetermined shape is formed on the surface of the photosensitive drum, the reference toner image is transferred onto the intermediate transfer belt, and the light emitted from the light emitting element is emitted. The reflected light is reflected by the reference toner image, and the reflected light is received by the light receiving element to obtain the received light amount according to the reflected light.
Using the amount of received light at the background portion of the surface of the intermediate transfer belt as a reference value, the reference value is compared with the amount of received light in the reference toner image to grasp the toner adhesion amount per unit area of the reference toner image. Based on the grasped toner adhesion amount, the photosensitive drum charging potential, the developing bias, the optical writing intensity to the photosensitive drum, the control target value of the developer toner density, etc. are adjusted so that the desired toner adhesion amount is obtained. Adjust the image conditions.
In the color misregistration correction, a toner pattern having an angle with respect to the main scanning direction is formed, and a positional deviation between the main scanning direction and the sub scanning direction is detected and corrected. When density adjustment or color misregistration correction is performed, the output of the optical sensor is adjusted so that a predetermined amount of received light is obtained at the background portion of the intermediate transfer belt surface. That is, the optical sensor is calibrated so that a predetermined amount of received light can be obtained by adjusting the output (current value) of the light emitting element.

However, if filming occurs in which an additive such as toner or paper accumulates on the intermediate transfer belt as a thin film over time, the glossiness of the belt decreases and the output of the sensor increases. That is, since the amount of reflected light decreases due to filming, the current value (forward current If) that flows through a light emitting element such as an LED must be increased in order to obtain a predetermined amount of received light. For this reason, the value of the current passed through the light emitting element becomes the output value of the sensor. If the output value of the sensor exceeds the upper limit, density adjustment and color misregistration correction cannot be performed. This is because a sufficient amount of received light cannot be obtained even though the amount of light emission is increased.
Further, there is a problem that the output of the sensor is not stable and cannot be adjusted (corrected) correctly due to uneven filming.
These problems are particularly likely to occur when the image area ratio, the number of output sheets per time are low, or the full color ratio is high.
When the area ratio of the image to be printed is high, the amount of toner input is large, so if filming has occurred on the belt, it will be removed, and the belt glossiness will be automatically prevented from being reduced, It is known that the reduced glossiness increases.
For the purpose of preventing uneven wear of the cleaning blade and preventing defective cleaning, a control method for forcibly supplying toner to the cleaning blade in accordance with the number of output images is also known.
However, in the case of the configuration up to now, the occurrence of filming depends on how the image forming apparatus is used, so even if filming occurs on the intermediate transfer belt over time and the glossiness decreases, it is appropriate There was no means to remove it at the right time.
In addition, control for inputting toner for the purpose of improving cleaning performance and preventing blade turning has been conventionally performed, but the purpose is different and is executed regardless of the occurrence of filming. It is not always done in Furthermore, filming itself occurs. For this reason, the problem that the density adjustment and the color misregistration correction cannot be performed due to the temporal change of the surface of the intermediate transfer belt or the like, and the adjustment accuracy and the correction accuracy are still not solved.

In contrast, in the present embodiment, the color printer 1 includes a pixel number counting unit 550 that counts the number of pixels in each region detected by a line sensor 610 serving as a pixel number detection unit, as shown in FIG. And a toner supply control unit 560 that supplies toner to the intermediate transfer belt 45 for each region based on the pixel count value by the number counting unit 550. The pixel number counting unit 550 and the toner supply control unit 560 are configured by the control unit 500 described with reference to FIG.
The line sensor 610 is divided into a plurality of regions in advance in the main scanning direction. The pixel number counting unit 550 has a function of detecting the number of pixels from an electrical signal of a certain part of the image among the information detected by the line sensor 610, and counting (calculating) by dividing each area. The pixel number counting unit 550 has a function of accumulating and counting the number of pixels for every predetermined distance of the traveling distance that is a predetermined period. The travel distance is, for example, a distance traveled by rotating the photosensitive member or the intermediate transfer belt 45. These travel distances are calculated by the control unit 500 from the rotational speed of the motor, the total length and the rotational speed of the intermediate transfer belt 45, and stored in the RAM 502. The predetermined period may be the operating time of the color printer 1. In this case, the cumulative operating time may be measured by the timer 504 and stored in the RAM 502. That is, the pixel count unit 550 has a function of storing the pixel count value calculated for each region in the RAM 502.

When the pixel count values A1a, A2b... Calculated for each area are lower than the threshold value A set in the ROM 503 in advance, the toner supply control unit 560 forms a toner image in the area that is lower than the threshold value A. Each part is controlled to be supplied. That is, the toner supply control unit 560 supplies the belt driving motor 211, the belt cleaning unit 20, the driving unit 214 of the optical writing unit 5, the belt to supply toner to the intermediate transfer belt 45 for each region based on the pixel count value. The operation of the removed toner image forming means 600 such as the separation drive unit 215, various power supply units 216, the primary transfer solenoid 217, and the secondary transfer roller solenoid 218 is controlled to form a toner image, which is below the threshold A. A toner image is supplied only to the area.
These operations of forming a toner image in accordance with the number of pixels per area and the image count value and supplying the toner image to the area below the threshold A are performed here by removing filming (film additive) This is executed by the controller 500 during the removal mode.

  The toner image formed in the removal mode is for removing the filming (film additive) generated on the surface of the intermediate transfer belt 45 to recover the surface state of the intermediate transfer belt 45. After being transferred to the belt, it is not subjected to secondary transfer and is removed together with filming by the belt cleaning unit 20. At this time, the secondary transfer roller 9 is separated to the separation position by the secondary transfer roller solenoid 218 of the contact / separation mechanism, so that transfer onto the paper P is prevented. Of course, the controller 500 also controls the power supply for secondary transfer so that the secondary transfer bias is not applied.

  The initial output value (the above-described initial output value If0) of the line sensor 610 as the background portion detection member is the sensor output value at the background portion of the intermediate transfer belt 45 in the initial stage of use (when new) or filming. It means the sensor output value at the background immediately after the removal.

Any image forming unit 3Y, 3M, 3C, 3K may be used as an image forming unit for forming a toner image in the removal mode. However, among them, a unit that uses a small amount of toner (in other words, (Also a unit with a large amount of toner). That is, the CPU 501 refers to the toner usage data for each of the image forming units 3Y, 3M, 3C, and 3K stored in the RAM 502, and uses the image forming unit 3Y, which is used to form a toner image in the removal mode. One of 3M, 3C, and 3K is determined and specified. Alternatively, the control unit 500 may determine an image forming unit that uses a small amount of toner from the number of pixels that is a detection result of the pixel number counting unit. In this case, the control unit 500 compares the cumulative number of pixels of yellow, magenta, cyan, and black, forms a toner image using the image forming unit having the color toner having the smallest cumulative number of pixels, and forms the intermediate transfer belt 45. To supply.
As a result, the toner in the image forming unit can be refreshed, and an early toner end can be avoided. Here, the refresh means that even if the developing device is driven, if the toner is not consumed, the toner becomes overcharged toner, and the electrostatic latent image on the photoreceptor cannot be properly developed. This means that the toner inside is carried on the photoreceptor and forcibly consumed.

The timing for executing the control of the removal mode is performed separately from the image forming operation for forming an image by transferring to the normal paper P. However, the interval between continuous printing, after the end of printing, or the image density adjustment mode and color The timing may be at the same time as the shift correction mode.
When the timing of executing the predetermined toner image formation in the removal mode is between the recording media to which the toner images formed by the normal image forming operation are transferred, that is, between the sheets of continuous printing, there is no influence on the normal image forming operation. There is an advantage that the removal mode can be executed.

If the timing of executing the predetermined toner image formation in the removal mode is before the start of the normal image forming operation or at the end of the normal image forming operation, that is, after the start or end of printing, each of the continuous printing before the removal mode There is an advantage that the integrity of the image quality can be maintained because the image quality of the paper does not change greatly, and the image quality of each of the continuous printing after the removal mode does not change significantly.
In addition, when the predetermined toner image formation timing in the removal mode is set to the same timing as other image measurement or image adjustment, that is, the same timing as the image density adjustment mode or the color misregistration correction mode, the image density adjustment mode or color There is an advantage that the shift correction mode can be executed without any influence.
Further, when the timing for executing the threshold determination in the removal mode is the same timing as other image measurement or image adjustment, that is, the calibration timing in the background portion 45b for the image density adjustment mode or the color misregistration correction mode, the image density There is an advantage that calibration for the adjustment mode and the color misregistration correction mode can be appropriately performed.

Next, one mode of the removal mode control will be described with reference to FIG. FIG. 9 is a flowchart showing one form of control content in the removal mode, which is executed by the control unit 500.
In step ST <b> 1, the control unit 500 acquires pixel number information on the front surface 45 a of the intermediate transfer belt 45 from the line sensor 610.
It should be noted that the control unit 500 reads the reading value of the background portion of the intermediate transfer belt 45 (the amount of light reflected by the line sensor 610 (light reception) when executing an adjustment mode such as image density adjustment or color misregistration correction or before the removal mode is started. It is preferable to adjust the output value (forward current If) of the line sensor 610 so that the amount)) becomes constant, and to obtain the adjusted output value.
In step S2, the control unit 500 counts the number of pixels for each region by the pixel number counting unit 550, and proceeds to step S13. The controller 500 determines whether or not a predetermined period has elapsed. Here, for example, the reference distance K0 preset in the ROM 503 is compared with the travel distance K1 of the intermediate transfer belt 45. If K0 ≦ K1, it is determined that the predetermined period has not elapsed, and the process returns to step S11 to return the number of pixels. And the cumulative count are continued, and if K0 ≦ K1, the process proceeds to step S4.
In step S14, the controller 500 calculates the total number of pixels Aa1, Aa2,. That is, the cumulative number of pixels counted within a predetermined period is calculated, and the process proceeds to step S15. In step S15, the control unit 500 compares the threshold value A set in the ROM 503 with the cumulative pixel number A1a. If there is no cumulative pixel number (pixel count value) that is lower than the threshold value A, the control unit 500 ends this control. If there is a cumulative pixel number (pixel count value) that is less than, the process proceeds to step S16. In step S16, the controller 500 supplies the toner image to an area that is equal to or smaller than the threshold value. That is, the controller 500 operates the removed toner image forming unit 600 so that the toner image is supplied to the area (A1...) Of the front surface 45a of the intermediate transfer belt 45 in which the cumulative number of pixels is equal to or less than the threshold value. Control.
After supplying the toner image, the control unit 500 proceeds to step S17 to reset the counted number of pixels and finish this control.

As described above, in this embodiment, the line sensor 610 causes the intermediate transfer belt 45 to move at a plurality of positions in the main scanning direction W orthogonal to the moving direction (sub-scanning direction W1) of the front surface 45a of the intermediate transfer belt 45. When the line sensor 610 detects the number of pixels for each area of the front surface 45a and counts it by the pixel number counting unit 550, when the cumulative number of pixels in a certain area for a predetermined period falls below a preset threshold A, The area below the threshold T of the transfer belt 45 is regarded as a filming generation area or an area where filming is likely to occur, and a toner image is supplied to the area. For this reason, the friction coefficient in the specific region (region below the threshold) of the front surface 45a of the cleaning blade 22 and the intermediate transfer belt 45 or the scraping function of the cleaning blade 22 increases, and the intermediate transfer belt 45 Foreign matter and filming can be removed together with the toner image, filming can be prevented while suppressing toner consumption, and even if it occurs, it can be removed at an appropriate timing. For this reason, the problem that adjustment precision and correction precision fall can also be solved.
Further, by dividing the base surface 45a of the intermediate transfer belt 45 into a plurality of regions in the main scanning direction W, it is not necessary to supply extra toner from the intermediate transfer belt 45 to the cleaning blade 22, so that toner is supplied efficiently. Thus, filming can be efficiently removed.
FIG. 10 is a diagram in which the total number of accumulated images on the front surface 45a of the intermediate transfer belt 45 in a fixed travel distance section is plotted. In FIG. 10, the vertical axis represents the number of images, and the horizontal axis represents a region divided in the longitudinal direction (main scanning direction / belt width direction). FIG. 10 shows the cumulative number of pixels of each color toner when forming yellow, magenta, cyan, and black color images. For example, when the value of the threshold A is the number of pixels “5”, the areas A1 and Ax are areas to be supplied with toner. Further, when the threshold value A is set to the number of pixels “10”, the region Az is also a toner supply target region.

The amount of toner that enters the cleaning blade 22 of the intermediate transfer belt 45 during printing is small because it is a transfer residual toner. However, in the case of toner supply by the toner image in the above-described removal mode for the purpose of preventing filming, the controller 500 The primary transfer voltage (primary transfer bias) is turned on, and the secondary transfer roller 9 activates the secondary transfer roller solenoid 218 to put it in the separated state. By controlling in this way, the developing toner can be allowed to enter the cleaning blade 22 of the intermediate transfer belt 45 as it is. As a result, filming can be prevented by supplying a small amount of toner.
Note that the primary transfer bias in the removal mode may be the same as that during normal output, but may be supplied by switching to a bias value at which toner is likely to adhere to the intermediate transfer belt 45 from the normal state. Alternatively, the conveyance speed of the intermediate transfer belt 45 in the removal mode may be slower than the conveyance speed during normal printing.

  For example, when toner is supplied from the intermediate transfer belt 45 to the target region via the cleaning blade 22 after color printing, the toner to be supplied to the toner supply region may be supplied from a toner with a small consumption amount. That is, the remaining amount of toner of each color is detected, and the toner with a large remaining amount is regarded as a toner with a small amount of consumption. By preventing the filming from occurring while suppressing toner consumption, the toner remains in the developing device for a long period of time because the color deviation and consumption amount of the toner consumption as a whole is small. The effect of suppressing toner deterioration due to stirring.

By the way, many color printers are capable of monochrome printing using black toner as well as color printing. In the case of monochrome printing, as shown in FIG. 11, since yellow, magenta, and cyan toners are not used, the photoreceptors 30Y, 30M, and 30C are used to prevent erroneous transfer of these color toners to the intermediate transfer belt 45. In many cases, a black mode for separating the intermediate transfer belt 45 from the intermediate transfer belt 45 is set. In this embodiment, the primary transfer rollers 6Y, 6M, and 6C are configured to come into contact with the intermediate transfer belt 45 by using a primary transfer roller solenoid 217 (see FIGS. 6 and 7).
That is, when the color image forming units (process cartridge units) 3Y, 3M, and 3C are not driven during printing in the black mode, the toner is supplied to the cleaning blade 22 via the intermediate transfer belt 45 after the black mode printing. In this case, by forming a toner image with black toner by the image forming unit 3K and supplying the toner image with black toner to an area below the threshold A, the occurrence of filming can be prevented.

In the above embodiment, the case where the total number of pixels in each region (cumulative pixel number) is equal to or less than the threshold A has been described as an example of the condition parameter for supplying the toner image to the region equal to or less than the threshold. Is not to be done.
For example, the ratio of the total number of pixels of each color in the region, that is, the bias of a specific color may be used as the threshold value. As an example, when there is an area where the number of images showing black is lower than the threshold A1 set in the ROM 503, the toner image may be supplied to an area lower than the threshold A1. In this way, it is possible to avoid filming that affects the characteristics of each color toner material while suppressing toner consumption and preventing filming.

  In the above embodiment, the reference (toner) pattern is detected using the line sensor 610 as the pixel number detection means, and the pixel number is calculated by the pixel number counting unit 550 (control unit 500). However, the present invention is not limited to this form. For example, the number of pixels may be calculated by the pixel number counting unit 550 (control unit 500) assuming that the optical unit 5 (exposure means) corresponds to the amount of light applied to the photoreceptors 30Y, 30M, 30C, and 30K. In addition, the irradiation spot intensity on the photoconductors 30Y, 30M, 30C, and 30K based on the image data to be printed (original data for a copying machine) is related to the amount of toner adhering to the photoconductors 30Y, 30M, 30C, and 30K. Therefore, the number of pixels may be calculated from the image data using the pixel number counting unit 550 (control unit 500). In the case of such a configuration, the line sensor 610 for detecting the number of images is not necessary, so that the configuration can be simplified.

  In the above embodiment, the cumulative number of pixels in each region is reset after the toner image is supplied to the region below the thresholds A and A1, but the cumulative number of pixels in the region where the toner is supplied to the intermediate transfer belt 45 ( If the number of accumulated pixels in the area below the thresholds A and A1 is not cleared, and it is necessary to continuously supply the next time, the toner supply amount to that area may be increased. The increase in the amount of toner supply here refers to an increase in the number and area of toner images (toner patterns) supplied to a region.

In the present exemplary embodiment, an intermediate transfer system is exemplified as the image forming apparatus, and the prevention of filming and the removal of filming from the intermediate transfer belt 45 serving as an image transfer member and intermediate transfer member have been described. The application of is not limited to the intermediate transfer method.
For example, the present invention can also be applied to a direct transfer type image forming apparatus in which a toner image formed on a photoconductor as an image carrier (latent image carrier) is directly transferred to a sheet P without using an intermediate transfer belt. In this case, the pixel number detection unit represented by the line sensor 610 is disposed so as to face the photoconductor, and is arranged so as to detect the number of pixels on the surface of the photoconductor after being transferred onto the paper P, and the cumulative number of pixels within a predetermined period. A toner image is formed on the surface of the photoconductor in an area where the value is below the threshold value and is supplied to the photoconductor cleaning member. In such a configuration, a reduction in the friction coefficient in a specific region (region below the threshold) on the front surface of the photosensitive member cleaning member and the photosensitive member or a scraping function of the photosensitive member cleaning member is increased, and the photosensitive member is increased. The foreign matter and filming on the top can be removed together with the toner image, the occurrence of filming can be prevented while suppressing the consumption of toner, and even if it occurs, it can be removed at an appropriate timing.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to such specific embodiments and examples, and is described in the claims unless otherwise limited by the above description. Various modifications and changes can be made within the scope of the present invention. For example, the technical matters described in the above embodiments and examples may be appropriately combined.

1 Color printer (an example of an image forming apparatus)
2 Device body 3 (Y, M, C, K) Image forming unit 4 Intermediate transfer unit 5 Optical writing unit 6 (Y, M, C, K) Primary transfer roller (primary transfer member)
7 (Y, M, C, K) Primary transfer portion 8 (Y, M, C, K) Secondary transfer portion 9 (Y, M, C, K) Secondary transfer roller (secondary transfer member)
10 Paper cassette 20 Belt cleaning unit 22 Cleaning blade (an example of a cleaning member)
30 (Y, M, C, K) photoconductor (latent image carrier / image carrier)
31 (Y, M, C, K) Charging device 32 (Y, M, C, K) Developing device 33 (Y, M, C, K) Cleaning devices 41-44 Support roller 45 Intermediate transfer belt (image carrier)
50 Photoconductor Drive Motor 51 Charging Roller Power Supply Unit 52 Developing Device Drive Unit 53 Cleaning Device Drive Unit 211 Belt Drive Motor 212 Slit Plate 213 Position Information Detection Sensor (Position Detection Member)
214 Optical Writing Unit Drive Unit 215 Belt Contact / Separation Drive Unit 216 Various Power Supply Units 218 Secondary Transfer Roller Solenoid 550 Pixel Count Counting Unit 560 Toner Supply Control Unit 610 Line Sensor (Pixel Number Detection Unit)
A1, A2,... Area P paper (an example of a recording medium)
W Main scanning direction W1 Sub scanning direction

Japanese Patent Laying-Open No. 2015-169877

Claims (8)

An image carrier that carries a toner image on the surface;
A cleaning member for removing a toner image on the surface of the image carrier;
A pixel number counting unit that counts the number of pixels per predetermined period for each region in the main scanning direction of the image carrier;
An image forming apparatus comprising: a toner supply control unit that supplies toner to the image carrier for each region based on a pixel count value by the pixel number counting unit. The image carrier is disposed opposite to an image forming unit that forms the toner image, and the toner image formed by the image forming unit is transferred by a primary transfer unit that applies a transfer bias, and is in contact with a transfer member. A transfer belt that is transferred to a recording medium at the next transfer section,
2. The image formation according to claim 1, wherein when supplying a toner image to the transfer belt, the toner supply control unit applies a transfer bias to the first transfer position to place the transfer member in a separated state from the transfer belt. apparatus. A plurality of image forming units for forming the toner image;
The toner supply control unit determines an image forming unit that uses a small amount of toner from the result of the pixel count counting unit, and forms a toner image to be supplied to the image carrier using the image forming unit that uses a small amount of toner. The image forming apparatus according to claim 1. A plurality of image forming units for forming the toner image;
One of the plurality of image forming units is configured to be in contact with the image carrier,
The image forming apparatus according to claim 1, wherein the toner supply control unit forms a toner image to be supplied to the image carrier using one image forming unit configured to be in contact with the image carrier. A plurality of image forming units for forming the toner image;
The pixel number counting unit counts the number of pixels of the toner image supplied from the plurality of image forming units to each region of the image carrier,
The toner supply control means uses the at least one image forming unit of the plurality of image forming units to place the toner image in an area having the smallest value among the number of pixels counted by the pixel number counting unit. The image forming apparatus according to claim 1, wherein the image forming apparatus is supplied.   The image carrier is a belt member that is disposed opposite to an image forming unit that forms the toner image, and that forms a transfer position for supplying the toner image formed by the image forming unit to a recording medium. 5. The image forming apparatus according to any one of items 1 to 4.   The image forming apparatus according to claim 1, wherein the toner is supplied to the image carrier at the end of a normal image forming operation.   6. The image forming apparatus according to claim 1, wherein the toner is supplied to the image carrier at the same time as other image measurement or image adjustment.

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