JP2019152796A - Image forming apparatus - Google Patents

Abstract

To remove filming on an image carrier by allowing the image carrier to carry the minimum required toner image so as not to waste toner.SOLUTION: An image forming apparatus comprises: an image carrier, such as an intermediate transfer belt 45; a cleaning member, such as a cleaning blade 22 that removes a toner image on the surface of the image carrier; and a surface detection member, such as a line sensor 610 that detects a ground part of the surface of the image carrier at a plurality of positions in a main scanning direction W orthogonal to a sub-scanning direction W1 that is the direction of movement of the surface of the image carrier, and the image forming apparatus allows the image carrier to carry a toner image at an arbitrary position on the surface from results of detection performed by the surface detection member, and removes, with the cleaning member, the toner image and a film-like additive accumulated on the surface of the image carrier. The surface detection member has an output adjusted so that the quantity of received light relative to reflected light from the ground part becomes constant, and the image forming apparatus compares an initial output value of the image carrier from the surface detection member with the current output value, and when the current output value is higher, removes the toner image and the film-like additive with the cleaning member.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an image forming apparatus.

  In image density adjustment and color misregistration correction control used in an electrophotographic image forming apparatus, an optical sensor is used to read the density and position of a detection toner pattern formed on a drum-shaped photoreceptor or an intermediate transfer belt. It is corrected.

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 optical sensor is calibrated by obtaining the amount of received light according to the reflected light.
Next, a reference toner image (density adjustment toner pattern) having a predetermined shape is formed on the surface of the photoconductor, and the reference toner image is transferred onto the intermediate transfer belt, and the light emitted from the light emitting element is used as a reference. The light is reflected by the toner image, and the reflected light is received by the light receiving element to obtain a received light amount corresponding to the reflected light.

Using the amount of light received at the background portion of the surface of the intermediate transfer belt as a reference value, this 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.
Image forming conditions such as the charging potential of the photosensitive member, the developing bias, the light writing intensity to the photosensitive member, and the control target value of the developer toner concentration so that the desired toner attaching amount is obtained based on the grasped toner attaching amount. Adjust.

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, when filming (hereinafter also referred to as film-like additive) occurs in which an additive such as toner or paper accumulates in a thin film form on an intermediate transfer belt (hereinafter also simply referred to as “belt”) over time, the belt The glossiness of the sensor decreases, and the amount of light received by the sensor at the background portion decreases. In such a case, calibration for increasing the output of the light emitting element of the sensor is performed in order to adjust the output (current value) of the light emitting element to obtain a predetermined amount of received light.
That is, since the amount of reflected light decreases due to filming, in order to obtain a predetermined amount of received light, the current value (forward current If) that flows through a light emitting element such as an LED must be increased. The current value that flows through the light emitting element is the output value of the sensor.

When the output value of the light emitting element of the sensor exceeds the upper limit, a sufficient amount of received light cannot be obtained even though the light emission amount is increased, and density adjustment and color misregistration correction cannot be performed.
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 likely to occur particularly when the image area ratio is low and the number of output sheets per time is small, or when the full color ratio is high.
On the other hand, when the area ratio of the image to be printed is high, the amount of toner input is large, so even if filming has occurred on the belt, this is removed, and the reduction in the glossiness of the belt is prevented or reduced. It is already known that the glossiness increases.

  In order to remove the filming on the intermediate transfer belt, there is a technology for detecting the background filming on the intermediate transfer belt using the sensor output for image density adjustment (process control) and discharging the toner onto the intermediate transfer belt. Known (for example, Patent Document 1).

  However, since the occurrence of filming up to now depends on how the image forming apparatus is used, even if filming occurs on the intermediate transfer belt over time and the glossiness decreases, the filming can be appropriately generated. It could not be removed at the timing.

That is, in order to improve the cleaning property and prevent the blade from turning over, the control for inputting the toner is executed regardless of the occurrence of filming, so that the removal of filming is not performed at an appropriate timing. Further, the technique of Patent Document 1 has a problem that toner is wasted because the toner is discharged even at a position where filming does not occur.
For this reason, density adjustment and color misregistration correction cannot be performed due to changes with time of the surface of the intermediate transfer belt or the like, and adjustment accuracy and correction accuracy are reduced.

  The present invention has been made in view of the above-described circumstances, and supports a filming (film) on an image carrier without wasteful consumption of toner by carrying a minimum necessary toner image on the image carrier. The purpose is to remove the additive).

  In order to achieve the above object, the present invention provides 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 the moving direction of the surface of the image carrier. A surface detection member that detects a background portion of the surface of the image carrier at a plurality of positions in a direction orthogonal to each other, wherein the surface of the image carrier is detected from each detection result of the surface detection member. In the image forming apparatus, the toner image is carried at an arbitrary position, and the cleaning member removes the toner image and the film-like additive deposited on the surface of the image carrier.

  According to the present invention, it is possible to remove the filming (film-like additive) on the image carrier without wasteful consumption of the toner by carrying the minimum necessary toner image on the image carrier. .

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 drive system and a belt cleaning configuration of an intermediate transfer unit. FIG. 4 is a perspective view for explaining an arrangement of a drive system and a line sensor of an intermediate transfer unit. It is a top view explaining the reading range of a line sensor. It is 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. FIG. 4 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. It is a flowchart explaining the operation | movement of Example 1 which concerns on the belt filming removal mode. FIG. 6 is a configuration diagram of a main part of an image forming unit and an intermediate transfer unit illustrating a configuration and operation of a second embodiment in a belt 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 serving as image forming portions for forming respective single color toner images from four color toners, and a belt-less unit and a transfer device. However, an intermediate transfer unit 4 is also 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 each of the image forming units 3Y, 3M, 3C, and 3K, an optical writing unit 5 is disposed as an exposure unit. 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 paper moving direction. Has been.
The image forming units 3Y, 3M, 3C, and 3K perform the electrophotographic process by using the above-described apparatuses and units, so that the image forming units 3Y, 3M, 3C, and 3K are monochromatic on the photoreceptors 30Y, 30M, 30C, and 30K as image carriers that carry toner images. 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 drive 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 as primary transfer members for transferring a toner image to the intermediate transfer belt 45 face the photoreceptors 30Y, 30M, 30C, and 30K. Are arranged.
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 where the secondary transfer portion 8 is formed and a separated position 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. It consists of a 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.
Further, on the right side of the secondary transfer roller 9 and the fixing unit 12, a double-sided unit that transports the paper to the secondary transfer roller 9 again during double-sided printing is disposed.

  Belt cleaning is performed on the intermediate transfer belt 45 near the support roller 41 to remove and clean residual toner that could not be transferred onto the intermediate transfer belt 45, and toner images including a toner patch and a solid image, which are reference patterns described later. A unit 20 is provided. The detailed configuration of the belt cleaning unit 20 will be described later.

  Between the secondary transfer roller 9 and the belt cleaning unit 20 downstream in the driving direction of the intermediate transfer belt 45, a line sensor 610 as a surface detection member is disposed 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 image forming performance, the line sensor 610 detects the reference pattern formed on the intermediate transfer belt 45 by the image forming unit as image data, and outputs it as an electrical signal to the control unit 500.

  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. A manual tray for manually feeding paper from the side of the color printer 1 is also provided.

  In addition to the above configuration, a new toner container 19 for storing four toner supply containers is provided, and the developing devices 32Y, 32M, 32C of the image forming units 3Y, 3M, 3C, and 3K are rotated by rotating the toner supply container. Toner is replenished to 32K. The number of rotations of the toner supply container is output to a control unit described later. A waste toner bottle, a power supply unit, and the like are also provided.

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 driving system and belt cleaning configuration of the intermediate transfer unit, and FIG. 3 is a perspective view for explaining the arrangement of the driving system of the intermediate transfer unit and the line sensor. 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 in order to clean the residue containing the film 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 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.

A line sensor 610 serving as a surface detection member is placed on the front surface of the intermediate transfer belt 45 above the upper roller surface wound around the support roller 44 and the support roller 41 in the entire area in the circumferential direction of the intermediate transfer belt 45. The surface 45a is disposed opposite to the surface 45a. 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 intermediate transfer belt side with respect to a portion which is charged on the photosensitive member and can be written and exposed but is not exposed.

The reading range of the line sensor and the configuration of the line sensor will be described with reference to FIGS. FIG. 4 is a plan view illustrating the reading range of the line sensor, and FIG. 5 is a cross-sectional view illustrating the configuration of the line sensor.
Since the line sensor 610 is configured to be arranged in a plurality of straight lines as described above, the background portion 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 unevenness in the filming state generated on each surface of the intermediate transfer belt 45 can be read.

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 electric signal is input to the control unit 500 of FIG.

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, and a ROM (Read Only Memory) 503 that stores a control program and various data. 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 / control member. A RAM 502 is backed up by a battery, and a non-volatile memory that stores and saves the amount of toner consumed by each of 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 as.

The control unit 500 includes image forming units 3Y, 3M, 3C, and 3K, a line sensor 610, a belt driving motor 211, a position information detection sensor 213, a belt cleaning unit 20, a driving unit 214 of the optical writing unit 5, and the above-described connection. A secondary transfer roller solenoid 217 and various power supply units 216 provided in the separation mechanism are connected via a signal line 510. The belt contact / separation drive unit 215 indicates a control target component used in an embodiment described later.
The various sensors output the detected detection values to the control unit 500, and the control unit 500 stores the input various detection values in the RAM 502.

  The main control target drive units of the image forming units 3Y, 3M, 3C, and 3K include a photoconductor drive motor 50 that rotationally drives the photoconductor 30 and a charging roller power supply unit that applies a voltage to the charging roller of the charging device 31. 51, 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), as shown in FIG. 7, a density adjustment toner pattern Kp, Cp, Mp, Yp as a detection toner image is formed separately from the normal image forming operation, and the intermediate transfer belt. 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.
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 of the intermediate transfer belt 45 is read is constant. That is, the line sensor 610 also serves as a background portion detection unit and a background portion detection member in the removal mode.

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 threshold value A, the image is transferred to normal paper. In addition to the image forming operation for forming an image, control (hereinafter also referred to as “removal mode”) is performed in which a predetermined toner image is formed and removed by the belt cleaning unit 20.
As described with reference to FIG. 4, the line sensor 610 can read by dividing the main scanning direction W of the intermediate transfer belt 45 into arbitrary areas. The above control is executed for each divided area, and a toner image is formed only in an area determined to be removed.

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 contact / separation mechanism.
Since toner is supplied to the cleaning site by the toner image formed in the removal mode, the friction coefficient reduction or scraping function with respect to the surface of the intermediate transfer belt 45 is increased, and the filming on the intermediate transfer belt 45 is combined with the toner image. Removed.

  The initial output value (the above-mentioned initial output value If0) as the background portion detection member of the line sensor 610 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.
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 removal mode is performed separately from the image forming operation for forming an image by transferring to normal paper, but between continuous printing papers, after printing, or in an image density adjustment mode or a color misregistration correction mode. It may be the timing at the same time.
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 for the image density adjustment mode or the color misregistration correction mode, the image density adjustment is performed. There is an advantage that calibration for the mode and the color misregistration correction mode can be performed appropriately.

  In the present embodiment, the surface of the intermediate transfer belt 45 at a plurality of positions in the main scanning direction W perpendicular to the moving direction (sub-scanning direction W1) of the surface of the intermediate transfer belt 45 by the line sensor 610 shown in FIGS. The toner image (toner pattern or the like) is formed on an arbitrary position detected by the background portion 45b. Moreover, in addition to arbitrary positions detected by the background sensor 45 b on the surface of the intermediate transfer belt 45 at a plurality of positions in the main scanning direction W by the line sensor 610, the position information detection sensor 213 applies to the surface of the intermediate transfer belt 45. By detecting the position information of the toner image (toner pattern or the like) carried in the sub-scanning direction W1, the region of the toner image (toner pattern or the like) to be formed can be grasped more accurately. Since the entire circumference of the intermediate transfer belt 45 and the outer circumference of the support roller 44 that is a driving roller are known, the position information detection sensor 213 can detect the moving speed of the intermediate transfer belt 45 and the line. The position information of the toner image (toner pattern or the like) in the sub-scanning direction W1 can be detected based on the position information of the sensor 610.

As described above, according to the present embodiment, filming (film additive) on an image carrier without carrying a wasteful consumption of toner by carrying a minimum necessary toner image on the image carrier. An image forming apparatus can be provided.
In addition to the line sensor as the surface detection member, the position information detection sensor as the position detection member is provided, so that the occurrence position of the filming generated on the surface of the intermediate transfer belt can be grasped more accurately.
In addition, an image forming apparatus that can suppress the influence in the adjustment mode such as density adjustment and color misregistration correction due to the change of the image carrier surface over time at an appropriate timing and position, and can contribute to the improvement of the accuracy of the adjustment mode and consequently the image quality. Can be provided.

Example 1
With reference to FIG. 8, a description will be given of a first embodiment relating to control of a removal mode (hereinafter referred to as “belt filming removal mode”). FIG. 8 is a flowchart for explaining the operation of the first embodiment according to the belt filming removal mode.
The CPU 501 outputs the output of the line sensor 610 so that the read value of the background portion of the intermediate transfer belt 45 (the amount of reflected light (the amount of received light)) of the intermediate transfer belt 45 is constant when executing an adjustment mode such as image density adjustment or color misregistration correction. The value (forward current If) is adjusted, and the adjusted output value is acquired (step S1). That is, the sensor output value after the adjustment of the reading value of the background portion acquired first at the time of executing the adjustment mode is acquired as the current sensor output value in the belt filming removal mode. However, the sensor output value acquisition timing is not limited to this.

The ratio of the (current) sensor output value (If) at that time to the initial sensor output value (If0) stored in the RAM 502 is an execution threshold A (here, 1 or more) for executing the belt filming removal mode. ) Or not (If / If0> A) is determined (step S2).
If the execution threshold A is exceeded, the belt filming removal mode is executed (step S3). In the belt filming removal mode, for normal image formation after execution of the density adjustment and color misregistration correction adjustment modes, for example, filming removal is performed at intervals of once every several sheets (between recording media and between sheets). A toner image having the toner pattern is created on the intermediate transfer belt 45, and the belt filming removal mode is executed.
If the execution threshold A is not exceeded at the time of determination, the belt filming removal mode is terminated without executing.

(Example 2)
With reference to FIG. 9, Embodiment 2 of the belt filming removal mode will be described. FIG. 9 is a configuration diagram of the main parts of the image forming unit and the intermediate transfer unit showing the configuration and operation of the second embodiment of the belt filming removal mode.
As shown in FIG. 9, only the photoreceptor 30K of one image forming unit 3K among the plurality of image forming units 3Y, 3M, 3C, and 3K is configured to be in contact with the intermediate transfer belt 45. In other words, among the four image forming units 3Y, 3M, 3C, and 3K, three image forming units 3Y, 3M, and 3C photoconductors 30Y, 30M, and 30C excluding the photoconductor 30K of one image forming unit 3K The primary transfer rollers 6Y, 6M, and 6C can be brought into contact with or separated from the primary transfer rollers 6Y, 6M, and 6C via the intermediate transfer belt 45 (hereinafter referred to as “contact and separation”).
As an approach / separation mechanism that enables the photoreceptors 30Y, 30M, and 30C of the three image forming units 3Y, 3M, and 3C to contact and separate from the primary transfer rollers 6Y, 6M, and 6C via the intermediate transfer belt 45, FIG. The belt contact / separation driving unit 215 described in the above. The belt contact / separation drive unit 215 is a known mechanism that combines, for example, a spring and a solenoid that allow the primary transfer rollers 6Y, 6M, and 6C to contact and separate from the photoreceptors 30Y, 30M, and 30C via the intermediate transfer belt 45. Or a known swing mechanism.

According to the second embodiment, when the filming removal mode is executed, in the case of an image using only the black (K) toner that is frequently used, only the black image forming unit 3K is driven, and the other image forming unit 3Y is driven. By not driving 3M and 3C, the life of the image forming unit can be extended.
In addition, filming of the intermediate transfer belt may occur due to foreign matter supplied from the image forming unit. Therefore, when the filming removal mode is executed, the primary transfer roller is separated so that the film of the intermediate transfer belt is filled. Ming occurrence risk can be reduced. That is, the filming can be removed while avoiding the filming due to the wraparound material from the image forming unit.

(Example 3)
A third embodiment of the belt filming removal mode will be described with reference to Table 1. In the third embodiment, as shown in Table 1, a plurality of execution threshold values A are set, and the execution interval of the removal mode can be adjusted according to the state of filming. In Table 1, the presence / absence of removal means the presence / absence of execution of the belt filming removal mode (the same applies to Table 2).

  As shown in Table 1, when the ratio of the sensor output values of the line sensor 610 is If / If0 ≦ 1, the belt filming removal mode is not executed. When the ratio of the sensor output values is 1 <If / If0 ≦ 2, a toner image (toner pattern or the like) is created on the intermediate transfer belt 45 at every job end after reaching 200 sheets of paper P. When the ratio of the sensor output values is 2 <If / If0 ≦ 3, a toner image (toner pattern or the like) is created on the intermediate transfer belt 45 at each job end after reaching 100 sheets of paper P. When the ratio of the sensor output values is 3 <If / If0, a toner image (toner pattern or the like) is created on the intermediate transfer belt 45 for each job end after reaching 20 sheets of paper P.

Thus, in Example 3, the execution interval of the belt filming removal mode is shortened as the filming state is worse. In other words, as the difference between the current sensor output value of the line sensor 610 and the initial sensor output value is larger, the number of executions of the belt filming removal mode is increased.
According to the third embodiment, the filming can be reliably removed by changing the number of executions of the belt filming removal mode in accordance with the degree of filming. Further, it is possible to reduce time and toner consumption related to the belt filming removal mode.

Example 4
Example 4 of the belt filming removal mode will be described with reference to Table 2. In Example 4, as shown in Table 2, a plurality of execution threshold values A are set, and the length of the toner pattern related to the size of the toner image formed is changed according to the filming state. In other words, the area of the toner image (toner pattern or the like) may be increased as the difference between the current sensor output value of the line sensor 610 and the initial sensor output value increases.

  As shown in Table 2, when the ratio of the sensor output values of the line sensor 610 is If / If0 ≦ 1, the belt filming removal mode is not executed as in the third embodiment. When the ratio of the sensor output values is 1 <If / If0 ≦ 2, the toner image formation length (described as “toner image formation length” in Table 2) is set to 5 mm on the intermediate transfer belt 45. create. When the ratio of the sensor output values is 2 <If / If0 ≦ 3, a longer toner image formation length of 10 mm is created on the intermediate transfer belt 45. When the ratio of the sensor output values is 3 <If / If0, a longer toner image formation length of 15 mm is created on the intermediate transfer belt 45. As described above, in Example 4, the length in the sub-scanning direction W1 can be adjusted as the size of the toner image (toner pattern or the like) according to the degree of filming.

  According to the fourth embodiment, the belt filming removal mode is changed so that the area of the toner image (toner pattern or the like) increases as the difference between the current sensor output value of the line sensor 610 and the initial sensor output value increases. By doing so, the strength of belt filming removal can be changed according to the degree of filming. Further, it is possible to reduce time and toner consumption related to the belt filming removal mode.

  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.

In the above-described embodiment and each example, the execution target of the filming removal mode is the intermediate transfer belt, but the present invention can be similarly applied to a drum-shaped photoconductor. In this case, the photoconductor functions as an image carrier, and the intermediate transfer belt functions as a transfer target.
Moreover, in the said embodiment and each Example, although the line sensor was set as the structure which also serves as a background part detection means and a background part detection member, a background part detection means and a background part detection member (sensor) are provided separately from a line sensor. It is good also as a structure.
Specifically, a tandem direct transfer image forming apparatus may be used instead of the tandem intermediate transfer image forming apparatus shown in FIG. The background portion in this case refers to a portion that is charged on the photoconductor and is capable of writing exposure but not exposed.

  Further, the line sensor 610 as the surface detection member is not limited to this, and may be a sensor constituted by a plurality of sensors in the main scanning direction or a moving sensor.

  The effects appropriately described in the embodiments of the present invention are merely a list of the most preferable effects resulting from the present invention, and the effects of the present invention are limited to those described in the embodiments of the present invention. It is not a thing.

1 Color printer (an example of an image forming apparatus)
2 Device body 3 Image forming unit, process cartridge 4 Intermediate transfer unit 5 Optical writing unit 6 Primary transfer roller (primary transfer member)
7 Primary transfer part 8 Secondary transfer part 9 Secondary transfer roller (secondary transfer member)
10 Paper cassette 20 Belt cleaning unit 22 Cleaning blade (an example of a cleaning member)
30 photoconductor (latent image carrier / image carrier)
31 Charging device 32 Developing device 33 Cleaning devices 41 to 44 Support roller 45 Intermediate transfer belt (an example of an 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 (Example of Position Detection Member)
214 Drive Unit 215 of Optical Writing Unit Belt Contact / Separation Drive Unit 216 Various Power Supply Units 610 Line Sensor (Example of Surface Detection Member)
P paper (an example of a recording medium)
W Main scanning direction W1 Sub scanning direction

Japanese Patent Laid-Open No. 2006-020970

Claims (10)

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 surface detection member that detects a background portion of the surface of the image carrier at a plurality of positions in a direction orthogonal to the moving direction of the surface of the image carrier;
From each detection result of the surface detection member, a toner image is supported at an arbitrary position on the surface of the image carrier, and the toner image and film-like additive deposited on the surface of the image carrier are removed by the cleaning member. Image forming apparatus.   The image forming apparatus according to claim 1, further comprising a position detection member that detects a position in the moving direction of the toner image carried on the surface of the image carrier. The surface detection member is configured to adjust the output so that the amount of received light with respect to the reflected light from the background portion is constant,
The initial output value of the image carrier by the surface detection member is compared with the current output value, and when the current output value is higher, the cleaning member removes the toner image and the film additive. The image forming apparatus according to claim 1, wherein a removal mode for removal is executable. A plurality of image forming units for forming the toner images carried on the image carrier;
The image forming apparatus according to claim 3, wherein the image forming unit that uses the least amount of toner is used to execute the removal mode. A plurality of image forming units for forming the toner image on the image carrier;
Only 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 3, wherein one image forming unit configured to be in contact with the image carrier is used for executing the removal mode.   6. The image forming apparatus according to claim 3, wherein the number of executions of the removal mode is increased as the difference between the current output value and the initial output value is larger.   6. The image according to claim 3, wherein the larger the difference between the current output value and the initial output value, the larger the area of the toner image formed in the removal mode. Forming equipment.   The image forming apparatus according to claim 3, wherein the timing of executing the removal mode is an end time of an image forming operation.   6. The image forming apparatus according to claim 3, wherein the timing of executing the removal mode is between recording media to which a toner image formed by an image forming operation is transferred.   The image forming apparatus according to claim 3, wherein the timing of executing the removal mode is in an image measurement or image adjustment mode.

Images