JP2021148927A - Image forming apparatus - Google Patents

Abstract

To provide an image forming apparatus that can execute calibration without stopping an image forming operation and can prevent adhesion of toner to a secondary transfer member.SOLUTION: An image forming apparatus comprises: a plurality of image forming units; an endless intermediate transfer belt; primary transfer members; a secondary transfer member; an image density sensor; end blades; a blade moving mechanism; and a control unit. The end blade presses edge parts against second image forming areas of the intermediate transfer belt to scrape off a toner image on the intermediate transfer belt as waste toner. The blade moving mechanism can move the end blades to a scraping position where the edge parts of the end blades are pressed against the intermediate transfer belt and a retracted position where the edge parts are separated from the intermediate transfer belt. The end blades are inclined to get closer to the ends in a width direction of the intermediate transfer belt from the upstream side toward the downstream side in the direction of travel of the intermediate transfer belt.SELECTED DRAWING: Figure 1

Description

The present invention relates to an image forming apparatus including an end blade for scraping a patch image for calibration formed on an intermediate transfer belt.

Conventionally, an endless intermediate transfer belt that is rotated in a predetermined direction and a plurality of image forming portions provided along the intermediate transfer belt are provided, and each image forming portion displays a toner image of each color on the intermediate transfer belt. An intermediate transfer type image forming apparatus is known in which a toner image is secondarily transferred onto a recording medium such as paper by a secondary transfer roller after being sequentially superimposed and primary transferred.

In such an intermediate transfer type image forming apparatus, in order to improve color development and color reproducibility, calibration for correcting image density and color shift is executed at a predetermined timing. Here, when a patch image is formed in the transfer region (transfer image formation region) of the intermediate transfer belt and calibration is executed, it is necessary to pause the image formation.

Therefore, Patent Document 1 discloses an image forming apparatus capable of performing calibration without stopping the image forming operation. The intermediate transfer belt of this image forming apparatus has a first image forming region in the center in the width direction of the transferred image forming region, and has second image forming regions on both sides of the first image forming region. When the size in the width direction of the recording medium is smaller than the size in the width direction of the first image forming region, a transfer image is formed in the first image forming region, and a patch image for calibration is placed in the second image forming region. Form. This makes it possible to perform calibration without stopping image formation.

The image forming apparatus of Patent Document 1 is provided with an end blade for removing the patch image at a position downstream of the image density sensor for reading the patch image and upstream of the secondary transfer roller. There is. By pressing the edge portion of the end blade against the second image forming region of the intermediate transfer belt, the patch image can be scraped off as waste toner. This prevents the patch image from adhering to the secondary transfer roller.

Japanese Unexamined Patent Publication No. 2006-337552

By the way, the end blades are arranged perpendicular to the traveling direction of the intermediate transfer belt. That is, the longitudinal direction of the end blade is perpendicular to the traveling direction of the intermediate transfer belt. Therefore, the waste toner scraped off by the end blade is dammed by the end blade even if it tries to flow downstream due to the progress of the intermediate transfer belt. The dammed waste toner stays between the end blade and the intermediate transfer belt.

However, the waste toner accumulated between the end blade and the intermediate transfer belt is centered (first image forming region) from the end in the width direction of the intermediate transfer belt due to an increase in the amount of waste toner, vibration, or the like. It may spill toward. If the waste toner spills on the first image forming region of the intermediate transfer belt, the waste toner is sent to the downstream side due to the progress of the intermediate transfer belt. Then, the waste toner may be transferred to the recording medium, or the waste toner may be transferred from the first image forming region to the secondary transfer roller, causing image defects such as smearing the back surface of the recording medium. be.

Further, when performing a printing operation on a recording medium having the same size as the width of the secondary transfer roller, which is the maximum size that can be printed, a transfer image is also formed in the second image forming region. At this time, it is necessary to separate the end blade from the second image forming region so that the end blade does not scrape the transferred image. If waste toner is accumulated between the end blade and the intermediate transfer belt when the end blades are separated, the waste toner will flow to the downstream side while the waste toner remains in the second image forming region. , There is a risk of causing image defects similar to the above.

If a driving component such as a screw for collecting waste toner dammed up by the end blade is provided in order to suppress such image defects, the image forming apparatus becomes large and the structure becomes complicated.

The present invention is an image forming apparatus capable of performing calibration without stopping an image forming operation, and has the same size as the size in the width direction of the secondary transfer roller, which is the maximum size while suppressing image defects with a simple structure. It is an object of the present invention to provide an image forming apparatus capable of suppressing stains on the back surface of a recording medium when printing is performed on the recording medium.

In order to achieve the above object, the first configuration of the present invention includes a plurality of image forming portions, an endless intermediate transfer belt, a primary transfer member, a secondary transfer member, an image density sensor, and an end blade. An image forming apparatus including a blade moving mechanism and a control unit. The plurality of image forming units form images of different colors. The intermediate transfer belt advances along the image forming portion and has a first image forming region located at the center in the width direction and a second image forming region located on both sides of the first image forming region in the width direction. .. The primary transfer member is arranged so as to face the image carriers arranged in each image forming portion with the intermediate transfer belt interposed therebetween, and the toner image formed on the image carrier is primarily transferred onto the intermediate transfer belt. The secondary transfer member secondarily transfers the toner image primaryly transferred on the intermediate transfer belt onto the recording medium. The image density sensor is arranged at a position on the upstream side of the secondary transfer member with respect to the traveling direction of the intermediate transfer belt so as to face the intermediate transfer belt, and the toner is formed in the second image forming region on the intermediate transfer belt. Read the image. The end blade is arranged between the image density sensor and the secondary transfer member, presses the edge portion against the second image forming region of the intermediate transfer belt, and scrapes the toner image on the intermediate transfer belt as waste toner. .. The blade moving mechanism can move the end blade to a scraping position where the edge portion is pressed against the intermediate transfer belt and a retracted position away from the intermediate transfer belt. The control unit controls the blade moving mechanism. The end blade is tilted toward the widthwise end of the intermediate transfer belt from upstream to downstream in the traveling direction of the intermediate transfer belt.

According to the first configuration of the present invention, waste toner is scraped off by the end blade as the intermediate transfer belt advances. The scraped waste toner tends to flow downstream due to the progress of the intermediate transfer belt, and is guided to the outside in the width direction of the intermediate transfer belt along the inclination of the end blade. Therefore, the waste toner is less likely to spill from between the end blade and the intermediate transfer belt toward the center (first image forming region) in the width direction of the intermediate transfer belt, and the first image forming region of the intermediate transfer belt is less likely to spill. Can be prevented from being polluted by waste toner.

Further, the end blade can be moved to a scraping position and a retracting position by a blade moving mechanism. By moving the end blade to the retracted position, a transferred image can be formed in the second image forming region, and printing can be performed on a recording medium having the maximum size. Here, since the scraped waste toner is guided to the outside in the width direction of the intermediate transfer belt due to the inclination of the end blade, when the end blade is moved to the retracted position, the waste toner is transferred to the intermediate transfer belt. Is hard to remain, and the secondary transfer roller is hard to get dirty. Therefore, it is possible to suppress stains on the back surface of the recording medium when printing on the maximum size recording medium.

Therefore, while suppressing image defects with a simple structure, it is possible to suppress stains on the back surface of the recording medium when printing on a recording medium having the same size as the size in the width direction of the secondary transfer roller, which is the maximum size. An image forming apparatus can be provided.

Schematic diagram showing an internal configuration of an image forming apparatus 100 according to an embodiment of the present invention. Enlarged view of the vicinity of the image forming portion Pa in FIG. The figure which shows the patch image used for calibration and the end blade 26. The figure which shows an example of the reference image for density correction used for calibration. Side sectional view of the intermediate transfer unit 31 mounted on the image forming apparatus 100 of the present embodiment. Partially enlarged view of the part where the end blade 26 and the intermediate transfer belt 8 come into contact with each other. Side sectional view of the periphery of the end blade 26 mounted on the image forming apparatus 100 of the present embodiment. A block diagram showing an example of a control path of the image forming apparatus 100 of the present embodiment. A flowchart showing an example of secondary transfer control executed in the image forming apparatus 100 of the present embodiment. The figure which shows how the end blade 26 of this embodiment guides waste toner D to the outside in the width direction of the intermediate transfer belt 8. The figure which shows the end blade 26 mounted on the image forming apparatus 100 of the modification of this embodiment. The figure which shows the end blade 26 mounted on the image forming apparatus 100 of the modification of this embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing the configuration of an image forming apparatus 100 according to an embodiment of the present invention, and FIG. 2 is an enlarged view of the vicinity of the image forming portion Pa in FIG.

The image forming apparatus 100 shown in FIG. 1 is a so-called tandem color printer, and has the following configuration. In the main body of the image forming apparatus 100, four image forming portions Pa, Pb, Pc and Pd are arranged in order from the upstream side in the transport direction (left side in FIG. 1). These image forming units Pa to Pd are provided corresponding to images of four different colors (magenta, cyan, yellow, and black), and are magenta, cyan, and yellow, respectively, depending on each step of charging, exposure, development, and transfer. And black images are formed sequentially.

Photoreceptor drums 1a, 1b, 1c and 1d carrying visible images (toner images) of each color are arranged in these image forming portions Pa to Pd. Further, in FIG. 1, an intermediate transfer belt 8 rotating in the counterclockwise direction is provided adjacent to each image forming portion Pa to Pd. The toner images formed on the photoconductor drums 1a to 1d are sequentially transferred onto the intermediate transfer belt 8 that moves while abutting on the photoconductor drums 1a to 1d, and then the secondary transfer roller 9 (secondary). The transfer member) is transferred at once on the paper S as an example of the recording medium. Further, after being fixed on the paper S in the fixing portion 13, it is discharged from the main body of the image forming apparatus 100. The image forming process for each of the photoconductor drums 1a to 1d is executed while rotating the photoconductor drums 1a to 1d in the clockwise direction in FIG.

The paper S on which the toner image is transferred is housed in the paper cassette 16 at the bottom of the main body of the image forming apparatus 100, and is conveyed to the secondary transfer roller 9 via the paper feed roller 12a and the resist roller pair 12b. .. A seamless (seamless) belt is mainly used for the intermediate transfer belt 8.

Next, the image forming units Pa to Pd will be described. Hereinafter, the image forming unit Pa will be described in detail, but since the image forming units Pb to Pd have basically the same configuration, the description thereof will be omitted. As shown in FIG. 2, a charging device 2a, a developing device 3a, and a cleaning device 7a are arranged around the photoconductor drum 1a along the drum rotation direction (clockwise direction in FIG. 2), and an intermediate transfer belt 8 is provided. The primary transfer roller 6a is arranged so as to sandwich the. Further, a belt cleaning unit 19 (cleaning mechanism) facing the tension roller 11 with the intermediate transfer belt 8 interposed therebetween is arranged on the upstream side of the photoconductor drum 1a in the rotation direction.

Next, the image forming procedure in the image forming apparatus 100 will be described. When the start of image formation is input by the user, first, the rotation of the photoconductor drums 1a to 1d is started by the main motor 61 (see FIG. 8), and the photoconductor drums 1a to 1d are started by the charging rollers 20 of the charging devices 2a to 2d. The surface of the drum is uniformly charged. Next, the surfaces of the photoconductor drums 1a to 1d are irradiated with light by the beam light (laser light) emitted from the exposure apparatus 5, and an electrostatic latent image corresponding to the image signal is formed on the photoconductor drums 1a to 1d.

The developing devices 3a to 3d are filled with a predetermined amount of toner of each color of magenta, cyan, yellow, and black, respectively. When the ratio of toner in the two-component developer filled in the developing devices 3a to 3d falls below the specified value due to the formation of the toner image described later, the toner containers 4a to 4d to the developing devices 3a to 3d are used. Toner is replenished. The toner in the developer is supplied onto the photoconductor drums 1a to 1d by the developing rollers 21 of the developing devices 3a to 3d and electrostatically adheres to the photoconductor drums 1a to 1d. As a result, a toner image corresponding to the electrostatic latent image formed by the exposure from the exposure apparatus 5 is formed.

Then, an electric field is applied between the primary transfer rollers 6a to 6d and the photoconductor drums 1a to 1d at a predetermined transfer voltage by the primary transfer rollers 6a to 6d, and magenta, cyan, yellow, and magenta, cyan, yellow, and magenta on the photoconductor drums 1a to 1d are applied. The black toner image is primarily transferred onto the intermediate transfer belt 8. These four-color toner images are formed with a predetermined positional relationship predetermined for forming a predetermined full-color image. After that, the toner remaining on the surfaces of the photoconductor drums 1a to 1d is removed by the cleaning blades 22 and the rubbing rollers 23 of the cleaning devices 7a to 7d in preparation for the subsequent formation of a new electrostatic latent image.

When the intermediate transfer belt 8 starts rotating counterclockwise as the drive roller 10 is rotated by the belt drive motor 63 (see FIG. 8), the paper S is adjacent to the intermediate transfer belt 8 from the resist roller pair 12b at a predetermined timing. The full-color image is transferred to the secondary transfer roller 9 provided. The paper S on which the toner image is transferred is conveyed to the fixing portion 13. The toner remaining on the surface of the intermediate transfer belt 8 is removed by the belt cleaning unit 19.

The paper S conveyed to the fixing portion 13 is heated and pressurized by the fixing roller pair 13a to fix the toner image on the surface of the paper S, and a predetermined full-color image is formed. The paper S on which the full-color image is formed is discharged by the discharge roller pair 15 as it is (or after being sent to the double-sided transport path 18 and printed on both sides) after the transport directions are sorted by the branch portions 14 branched in a plurality of directions. It is discharged to the tray 17.

The image density sensor 25 is arranged at a position facing the drive roller 10 with the intermediate transfer belt 8 interposed therebetween. As the image density sensor 25, an optical sensor including a light emitting element made of an LED or the like and a light receiving element made of a photodiode or the like is generally used. When measuring the amount of toner adhering to the intermediate transfer belt 8, when the reference image (each patch image) formed on the intermediate transfer belt 8 is irradiated with the measurement light from the light emitting element, the measurement light is the light reflected by the toner. , And incident on the light receiving element as light reflected by the belt surface.

The reflected light from the toner and the belt surface includes specularly reflected light and diffusely reflected light. The specularly reflected light and the diffusely reflected light are separated by a polarization separation prism and then incident on separate light receiving elements. Each light receiving element photoelectrically converts the specularly reflected light and the diffusely reflected light received and outputs an output signal to the control unit 90 (see FIG. 8).

Then, the image density (toner amount) and image position of the patch image are detected from the characteristic changes of the output signals of the positively reflected light and the diffusely reflected light, and the characteristic value of the developing voltage is compared with the predetermined reference density and the reference position. By adjusting the exposure start position, timing, and the like of the exposure apparatus 5, density correction and color shift correction (calibration) are performed for each color.

FIG. 3 is a diagram showing an example of a patch image for color shift correction used for calibration. The intermediate transfer belt 8 has a first image forming region R1 located at the center in the width direction and a second image forming region R2 located on both sides of the first image forming region R1 in the width direction. The first image forming region R1 is a band-shaped region in which a toner image for forming a full-color image to be transferred to the paper S is formed.

The second image forming region R2 is a band-shaped region provided on one side and the other side in the width direction of the intermediate transfer belt 8 with the first image forming region R1 interposed therebetween. A patch image for calibration is formed in each second image forming region R2. In the second image forming region R2, patch images M, C, Y, and K composed of diagonal lines and horizontal lines of magenta, cyan, yellow, and black are formed. The arrow X1 indicates the traveling direction of the intermediate transfer belt 8 (hereinafter, simply referred to as “traveling direction”). The patterns of the patch images M to K shown in FIG. 3 are general, and the color shift in the main scanning direction (belt width direction) is detected by using the diagonal lines and the horizontal lines of each color, and the sub is obtained from the interval between the horizontal lines of each color. Detects color shift in the scanning direction (belt circumferential direction).

Further, since the patch images M to K are formed in the same pattern at both ends in the main scanning direction (belt width direction), the same magnification of the main scanning and the scanning inclination can be detected. Further, in order to reduce the detection unevenness of the color shift in the belt circumferential direction, the patch images M to K are repeatedly formed in the sub-scanning direction, and the same pattern is measured a plurality of times to take the average value of the shift amount. ing. The positional relationship between the diagonal lines and straight lines of each color is detected by the image density sensor 25 and compared with a predetermined reference position, and when correcting the color shift in the main scanning direction, the exposure start position of the exposure apparatus 5 is adjusted. When correcting the color shift in the sub-scanning direction, the color shift is corrected for each color by adjusting the exposure start timing of the exposure apparatus 5.

In the present embodiment, the dimension of the intermediate transfer belt 8 in the width direction is 360 mm, the reading position of the image density sensor 25 is a position of 22.5 mm from the end of the belt, and the second image forming region R2 is abbreviated in the width direction. The central part can be detected. The dimension of the secondary transfer roller 9 in the width direction is 330 mm, which is the same as the maximum size of the insertable paper S (13 inches, paper width 330 mm).

FIG. 4 is a diagram showing an example of patch images M to K for density correction used for calibration. On one side (right side) of the second image forming region R2 of the intermediate transfer belt 8, a patch image consisting of patch images m1 to m10 having 10 levels of density, from the lightest patch image m1 to the darkest patch image m10. m are formed in a row in order from the downstream side along the traveling direction (arrow X1 direction). The patch images m1 to m10 are each formed in a single color so that the density changes at the boundary between adjacent patch images. Although the magenta patch image m has been described here as an example, the cyan, yellow, and black patch images c, y, and k have exactly the same configuration.

The toner adhesion amount (toner density) of the patch images m to k is detected by the image density sensor 25 and compared with a predetermined standard density, and the average value of the density difference between each toner density and the standard density is calculated. The parameter values used for the density correction are read from the density correction table according to the average value of the obtained density differences, and the density correction is executed for each color.

FIG. 5 is a side sectional view of the intermediate transfer unit 31 mounted on the image forming apparatus 100 of the present embodiment. As shown in FIG. 5, the intermediate transfer unit 31 includes the intermediate transfer belt 8 spanned by the drive roller 10 on the downstream side and the tension roller 11 on the upstream side, and the photoconductor drums 1a to the intermediate transfer belt 8 via the intermediate transfer belt 8. It has primary transfer rollers 6a to 6d that come into contact with 1d, and a pressing switching roller 34.

The intermediate transfer unit 31 can rotate both ends of the rotation shafts of the primary transfer rollers 6a to 6d and the pressing switching roller 34, and supports the intermediate transfer unit 31 so as to be movable perpendicular to the traveling direction of the intermediate transfer belt 8 (vertical direction in FIG. 5). A roller attachment / detachment mechanism 35 having a pair of support members (not shown) and a driving means (not shown) for reciprocating the primary transfer rollers 6a to 6d and the pressing switching roller 34 in the vertical direction is provided. .. The roller contact / disengagement mechanism 35 has only a color mode in which four primary transfer rollers 6a to 6d are pressed against the photoconductor drums 1a to 1d (see FIG. 1) via an intermediate transfer belt 8 and only the primary transfer roller 6d. It is possible to switch between a monochrome mode in which the photoconductor drum 1d is pressed against the photoconductor drum 1d via the intermediate transfer belt 8 and a retracting mode in which all four primary transfer rollers 6a to 6d are separated from the photoconductor drums 1a to 1d.

A belt cleaning unit 19 for removing toner remaining on the surface of the intermediate transfer belt 8 is arranged at a position facing the tension roller 11. A secondary transfer roller 9 is arranged and pressure-welded to the drive roller 10 via an intermediate transfer belt 8.

As shown in FIG. 2, the belt cleaning unit 19 comes into contact with the fur brush 42, which is arranged in the housing 44 via the intermediate transfer belt 8 and is opposed to the tension roller 11, and the surface of the fur brush 42, and the fur brush 42 is in contact with the surface of the fur brush 42. A recovery roller 43 capable of recovering the waste toner D adhering to the waste toner D, a scraper (not shown) for scraping the waste toner collected by the recovery roller 43, and a waste toner scraped by the scraper are conveyed to the second storage container 39 described later. The transport spiral 47 is provided.

As shown in FIGS. 1 and 3, each patch image (toner image) formed in the second image forming region R2 is waste toner on the downstream side of the image density sensor 25 and upstream of the secondary transfer roller 9. The end blade 26 for scraping is provided. The end blades 26 are arranged on one side and the other side in the width direction so as to sandwich the first image forming region R1.

As shown in FIGS. 6 and 7, the end blade 26 has a position L1 (scraping position L1) at which the edge portion 29 of the end blade 26 is pressed against the second image forming region R2 to scrape the patch image. , The edge portion 29 of the end blade 26 can be moved to and from the position L2 (retracted position L2) separated from the second image forming region R2.

The end blade 26 at the scraping position L1 is in contact with the second image forming region R2. At the scraping position L1, one end (inner end 28) of the end blade 26 in the longitudinal direction overlaps the second image forming region R2 in the surface direction, and the other end (outer end) of the end blade 26 in the longitudinal direction. The portion 27) is located outside both ends of the intermediate transfer belt 8 in the width direction. The edge portion 29 of the end blade 26 at the scraping position L1 is pressed against the second image forming region R2. As the intermediate transfer belt 8 advances in this state, each patch image on the second image forming region R2 is scraped off.

The end blade 26 at the scraping position L1 is located in the width direction of the intermediate transfer belt 8 from the upstream side (upper side in FIG. 6) to the downstream side (lower side in FIG. 6) of the traveling direction X1 of the intermediate transfer belt 8. It is tilted closer to the edge. That is, the end blade 26 at the scraping position L1 is inclined so as to be displaced downstream from the inner end 28 to the outer end 27. An inclination angle θ is formed between the end blade 26 and the width direction of the intermediate transfer belt 8 orthogonal to the traveling direction X1. The value of the inclination angle θ is 30 ° <θ <60 ° (more preferably 40 ° <θ <50 °).

Returning to FIG. 3, the edge portion 29 of the end blade 26 at the retracted position L2 is separated from the second image forming region R2. The retracted position L2 is a position outside the second image forming region R2 in the width direction. The retracting position L2 and the scraping position L1 are on the same plane as the contact surface between the edge portion 29 of the end blade 26 and the intermediate transfer belt 8, and the positions of the intermediate transfer belt 8 in the surface direction coincide with each other.

The end blade 26 is connected to a blade moving mechanism 30 (see FIG. 8). The blade moving mechanism 30 can reciprocate the end blade 26 to the scraping position L1 and the retracting position L2. At this time, the end blade 26 moves horizontally along the contact surface with the intermediate transfer belt 8 between the scraping position L1 and the retracting position L2. That is, the blade moving mechanism 30 can move the end blade 26 at the scraping position L1 horizontally toward the outside in the width direction of the intermediate transfer belt 8.

The blade moving mechanism 30 includes a pulse motor 65 as a drive source for moving the end blade 26 between the scraping position L1 and the retracting position L2. The pulse motor 65 is connected to the control unit 90 via a motor driver. The motor driver (not shown) is a drive circuit for driving various motors (main motor 61, belt drive motor 63, transfer roller drive motor 64, pulse motor 65, etc.). When the patch image is scraped together with the execution of the calibration, the motor driver drives the pulse motor 65 to move the end blade 26 to the scraping position L1 according to the instruction from the control unit 90. When the patch image is scraped by the end blade 26, the motor driver drives the pulse motor 65 to move the end blade 26 from the scraping position L1 to the retracted position L2. In this way, the end blade 26 can be moved to the scraping position L1 when the calibration is executed, and the end blade 26 can be moved to the retracted position L2 after the calibration is completed.

As shown in FIGS. 2 and 7, waste toner D removed by the belt cleaning unit 19 and waste toner D scraped off by the end blade 26 can be stored below the intermediate transfer belt 8. The container 36 is arranged.

The waste toner accommodating container 36 has an opening 37, a first accommodating portion 38, a second accommodating portion 39, a waste toner transfer pipe 40, and a transfer screw 41. The opening 37 opens at a position where it overlaps the contact portion J1 between the end blade 26 and the widthwise end of the intermediate transfer belt 8 in the vertical direction. The first accommodating portion 38 has a cylindrical shape having a bottom located below the opening 37, and can accommodate the waste toner D scraped off by the end blade 26 in the internal space from the opening 37 to the bottom. Is.

The second accommodating portion 39 is arranged below the belt cleaning unit 19 and can accommodate the waste toner D conveyed by the conveying spiral 47. The transport spiral 47 is connected to the second storage unit 39, and transports the waste toner D removed by the belt cleaning unit 19 into the second storage unit 39.

The waste toner transfer pipe 40 is a tubular body having openings at both ends that connects the first accommodating portion 38 and the second accommodating portion 39. The first accommodating portion 38 and the second accommodating portion 39 communicate with each other via the waste toner transfer pipe 40. The transfer screw 41 is provided inside the waste toner transfer pipe 40 coaxially with the waste toner transfer pipe 40. The transfer screw 41 can rotate around the axis in the circumferential direction. By rotating the transfer screw 41, the waste toner D introduced from one opening of the waste toner transfer pipe 40 can be transferred to the other opening of the waste toner transfer pipe 40.

As shown in FIG. 7, the waste toner D scraped off by the end blade 26 and guided to the outside in the width direction of the intermediate transfer belt 8 falls toward the opening 37 and is inside the first accommodating portion 38. It is housed in the space. The waste toner D in the first accommodating portion 38 is sent from the first accommodating portion 38 to the second accommodating portion 39 through the waste toner transfer pipe 40 by the rotation of the transfer screw 41. In this way, the waste toner storage container 36 stores the waste toner D removed by the belt cleaning unit 19 and the waste toner D scraped off by the end blade 26 in the second storage space inside the waste toner storage container 36. It can be accommodated in the part 39.

FIG. 8 is a block diagram showing an example of a control path of the image forming apparatus 100 of the present embodiment. Since various controls are performed for each part of the image forming apparatus 100 in using the image forming apparatus 100, the control path of the entire image forming apparatus 100 becomes complicated. Therefore, here, the part of the control path required for the implementation of the present invention will be mainly described.

The control unit 90 includes a CPU (Central Processing Unit) 91 as a central processing unit, a ROM (Read Only Memory) 92 as a read-only storage unit, a RAM (Random Access Memory) 93 as a readable and writable storage unit, and a temporary storage unit. A plurality of (here, two) that transmit a control signal or receive an input signal from the operation unit 80 to each device in the temporary storage unit 94, the counter 95, and the image forming device 100 that specifically stores image data and the like. It has at least the I / F (interface) 96 of. Further, the control unit 90 can be arranged at an arbitrary place inside the main body of the image forming apparatus 100.

The ROM 92 contains data such as a control program for the image forming apparatus 100, numerical values necessary for control, and the like that are not changed during use of the image forming apparatus 100. The RAM 93 stores necessary data generated during the control of the image forming apparatus 100, data temporarily required for controlling the image forming apparatus 100, and the like. The RAM 93 (or ROM 92) also stores a density correction table or the like used for calibration. The counter 95 integrates and counts the number of printed sheets.

Further, the control unit 90 transmits a control signal from the CPU 91 to each part and the device in the image forming apparatus 100 through the I / F 96. Further, a signal indicating the state and an input signal from each part and the device are transmitted to the CPU 91 through the I / F 96. The parts and devices controlled by the control unit 90 include, for example, the image forming units Pa to Pd, the exposure device 5, the primary transfer rollers 6a to 6d, the secondary transfer roller 9, the roller attachment / detachment mechanism 35, the main motor 61, and the belt. Examples thereof include a drive motor 63, a transfer roller drive motor 64, a pulse motor 65, an image input unit 70, a voltage control circuit 71, and an operation unit 80.

The image input unit 70 is a receiving unit that receives image data transmitted from a higher-level device such as a personal computer to the image forming apparatus 100. The image signal input from the image input unit 70 is converted into a digital signal and then sent to the temporary storage unit 94.

The operation unit 80 is provided with a liquid crystal display unit 81 and LEDs 82 indicating various states. The user operates the stop / clear button of the operation unit 80 to stop image formation, and operates the reset button to operate the image. The various settings of the forming device 100 are set to the default state. The liquid crystal display unit 81 is designed to show the state of the image forming apparatus 100, and to display the image forming status and the number of printed copies. Various settings of the image forming apparatus 100 are performed from the printer driver of the personal computer.

FIG. 9 is a flowchart showing an example of secondary transfer control executed in the image forming apparatus 100 of the present embodiment. The secondary transfer control procedure at the time of image formation will be described along the steps of FIG. 9 with reference to FIGS. 1 to 8 as necessary.

First, the control unit 90 determines whether or not a print command has been received (step S1). If the print command is not received (No in step S1), the print standby state is continued. When a print command is received (Yes in step S1), it is determined whether or not the paper size is larger than the first image forming area R1 based on the paper size information input from the host device such as a personal computer or the operation unit 80. Determine (step S2).

When the paper size is larger than the first image forming region R1 (Yes in step 2), it is determined whether or not the end blade 26 is at the scraping position L1 (step 3). When the end blade 26 is in the scraping position L1 (Yes in step 3), the end blade 26 is moved to the retracted position L2 (step 4). If the end blade 26 is not at the scraping position L1 (No in step 3), the process proceeds to the next step as it is. Next, the control unit 90 conveys the paper S to the secondary transfer roller 9 and executes printing (step 5).

When the paper size is equal to or less than the first image forming region R1 (No in step 2), it is determined whether or not to execute the calibration (step 6). When performing calibration (Yes in step 6), it is determined whether or not the end blade 26 is in the retracted position L2 (step 7). When the end blade 26 is in the retracted position L2 (Yes in step 7), the control unit 90 transmits a control signal to the pulse motor 65 to move the end blade 26 to the scraping position L1 (step 8). Next, a predetermined patch image is formed in the second image forming region R2 of the intermediate transfer belt 8 and calibration is executed (step 9). Then, printing is executed by a normal image forming operation (step 5). When the calibration is not executed (No in step 6), only normal printing is executed without forming a patch image (step 5).

After that, the control unit 90 determines whether or not printing is completed (step 10), and if printing is continued (No in step 10), returns to step 2 and executes printing and calibration if necessary. (Steps 2-9). If printing is completed (Yes in step 10), the process ends.

According to the configuration of the present embodiment, when the calibration is executed at the same time as printing, the patch image formed in the second image forming region R2 is read by the image density sensor 25 and then discarded by the end blade 26. It is scraped off as toner D. Therefore, the patch image does not come into contact with the secondary transfer roller 9, and the secondary transfer roller 9 can be prevented from being soiled by the patch image. Further, since the cleaning operation of returning the toner adhering to the secondary transfer roller 9 to the intermediate transfer belt 8 is not required, the printing waiting time can be shortened.

Further, the waste toner D scraped off by the end blade 26 tends to flow to the downstream side due to the progress of the intermediate transfer belt 8, but since the end blade 26 is inclined, the end blade 26 is inclined. Along the route, the intermediate transfer belt 8 is guided to the outside in the width direction (see FIG. 10). Therefore, the waste toner D is less likely to spill toward the center of the intermediate transfer belt 8 in the width direction (first image forming region R1), and image defects due to the intermediate transfer belt 8 being soiled by the waste toner D are suppressed. Can be done.

Further, as described above, the scraping position L1 and the retracting position L2 coincide with each other in the position in the surface direction of the intermediate transfer belt 8, and the end blade 26 is located between the scraping position L1 and the retracting position L2. Therefore, it can be moved in the horizontal direction along the contact surface with the intermediate transfer belt 8. The retracted position L2 is located outside the scraping position L1 in the width direction of the intermediate transfer belt 8. Therefore, when the end blade 26 moves from the scraping position L1 to the retracted position L2 in a state where the waste toner D is accumulated between the edge portion 29 of the end blade 26 and the intermediate transfer belt 8, the accumulated toner D is accumulated. The waste toner D is guided by the edge portion 29 of the end blade 26 so as to be swept outward in the width direction of the intermediate transfer belt 8. Therefore, when the paper S larger than the first image forming region R1 is inserted, the waste toner D is less likely to remain on the intermediate transfer belt 8 after the end blade 26 is moved from the scraping position L1 to the retracting position L2. Become. Therefore, it is possible to effectively suppress the stain on the back surface of the paper when the paper larger than the first image forming region R1 is inserted after the calibration is executed.

Further, by setting the value of the inclination angle θ to 30 ° <θ <60 ° (more preferably 40 ° <θ <50 °), the scraped waste toner D is along the inclination of the end blade 26. Therefore, it becomes easy to be guided to the outside in the width direction of the intermediate transfer belt 8, and the waste toner D is less likely to collect between the end blade 26 and the intermediate transfer belt 8. Further, by setting the value of the inclination angle θ to 30 ° <θ <60 ° (more preferably 40 ° <θ <50 °), when the end blade 26 moves from the scraping position L1 to the retracted position L2. In addition, the waste toner D is easily swept by the end blade 26. As a result, image defects can be suppressed more effectively.

Further, the outer end portion 27 of the end blade 26 is located outside the end portion in the width direction of the intermediate transfer belt 8. Therefore, the waste toner D guided along the end blade 26 is guided to the outside of the widthwise end of the intermediate transfer belt 8 without interruption.

Others The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, FIGS. 1 and 7 show the end blade 26 arranged below the intermediate transfer belt 8, but as shown in FIGS. 11 and 12, the end blade 26 is above the intermediate transfer belt 8. It may be arranged in. In the image forming apparatus in this case, the image forming portions Pa to Pd are arranged above the intermediate transfer belt 8, and the image density sensor 25 is also arranged above the intermediate transfer belt 8. The waste toner storage container 36 is arranged below the end blade 26. The opening 37 is located below the contact portion J1 between the end blade 26 and the outer end of the intermediate transfer belt 8 in the width direction. The end blade 26 is pressed against the edge portion 29 from above the intermediate transfer belt 8 toward the upper surface of the intermediate transfer belt 8. The scraped waste toner D is guided toward the outside of the widthwise end of the intermediate transfer belt 8 by the end blade 26, falls from the contact portion J1, and passes through the opening 37 of the waste toner storage container 36. It is introduced into the internal space of the first accommodating portion 38.

Further, the present invention is not limited to the tandem type color printer as shown in FIG. 1, and the toner image primaryly transferred to the intermediate transfer belt 8 such as a color copier or a color multifunction device is secondarily transferred to a recording medium. It can be applied to various image forming devices using a next transfer roller. Hereinafter, the effects of the present invention will be described in more detail with reference to Examples.

Verification experiment on the waste toner scraping performance of the second image forming region R2 when the end blade 26 of the present invention is used, and the effect of suppressing backside stains when a large-sized paper is performed after calibration is executed. Was done. As the testing machine, an intermediate transfer type image forming apparatus 100 (TASKalfa6052ci, manufactured by Kyocera Document Solutions Co., Ltd.) including the end blade 26 as shown in FIG. 1 is used, and the inclination angle θ of the end blade 26 is determined. The displacement was made by 15 ° between 0 ° and 60 °, and the experimental results at each angle were compared.

In the image forming apparatus 100 of Comparative Example 1, in Comparative Example 1, the inclination angle θ of the end blade 26 is set to 0 ° (the end blade 26 moves in the traveling direction) as in the image forming apparatus provided with the conventional end blade 26. It is set so that it is perpendicular to the vertical), and the inclination angle θ is set to increase by 15 ° in sequence from Comparative Examples 1 to 5.

As a test method, 1000 half images with a printing rate of 25% are continuously printed as test images on A3 plain paper (paper width 297 mm) at a process linear speed of 152 mm / sec, and a second image forming region of the intermediate transfer belt 8 is printed at the time of printing. A patch image of a predetermined pattern is formed on R2, and this patch image is scraped off by the end blade 26. Then, 13-inch plain paper (paper width 330 mm) was passed through, and one half image having a printing rate of 25% was printed as a test image. At this time, the scraping property of the end blade 26, the occurrence of dirt on the back surface of the 13-inch plain paper, and the malfunction of the belt drive motor 63 due to the frictional resistance of the end blade 26 were evaluated.

The evaluation standard for scrapability is the FD (Fog) at the position where the 25% half image transferred to 13-inch plain paper is measured by the reflection densitometer and overlaps with the second image forming region R2 during the secondary transfer of the paper. When Density) was less than 0.1, it was evaluated as ◯, and when it was 0.1 or more, it was evaluated as ×. The stain on the back surface of the paper was evaluated as ◯ when the FD on the back surface of the paper was less than 0.1, and x when it was 0.1 or more. Further, regarding the malfunction of the belt drive motor 63, the torque value of the belt drive motor 63 when the end blade 26 is in the retracted position L2 is used as a reference value, and the belt drive motor 63 at the time of performing calibration with respect to this reference value is used. When the rate of increase in torque value was less than 5%, it was evaluated as 0, and when it was 5% or more, it was evaluated as ×. These results are shown in Table 1.

As shown in Table 1, it was confirmed that the patch image of the second image forming region R2 can be scraped off by the end blade 26 in all of Comparative Examples 1 to 5.

In Comparative Examples 1 to 3 in which the inclination angles θ were set to 0 °, 15 °, and 30 °, the back surface of the paper was stained. This is because the inclination angle θ is relatively small and the inclination of the end blade 26 is gentle. Therefore, when the end blade 26 is moved from the scraping position L1 to the retracted position L2, the intermediate transfer belt 8 of the end blade 26 and the end blade 26 are moved. The waste toner D accumulated between the two could not be swept by the edge portion 29 of the end blade 26, and the waste toner D left on the surface of the intermediate transfer belt 8 adhered to the secondary transfer roller 9. This is because it has been done. On the other hand, in Comparative Examples 4 and 5 in which the inclination angles θ were 45 ° and 60 °, the back surface of the paper was not contaminated. This is because the inclination angle θ is relatively large and the inclination of the end blade 26 is steep. Therefore, when the end blade 26 is moved from the scraping position L1 to the retracted position L2, the waste toner D is moved to the edge portion. This is because 29 makes it easier to sweep out the intermediate transfer belt 8 to the outside in the width direction. Therefore, it was confirmed that the larger the inclination angle θ, the easier it is to prevent the back surface of the paper from being soiled, and the larger the inclination angle θ is, the more the back surface of the paper can be prevented from being soiled.

In Comparative Examples 1 to 4, no malfunction of the belt drive motor 63 was observed. On the other hand, in Comparative Example 5, a malfunction of the belt drive motor 63 was confirmed. This is because the end blade 26 needs to overlap the second image forming region R2 when it is at the scraping position L1, so that the length of the end blade 26 becomes longer as the inclination angle θ becomes larger. .. Therefore, the contact length between the end blade 26 at the scraping position L1 and the intermediate transfer belt 8 becomes long, and the frictional force generated between the end blade 26 and the intermediate transfer belt 8 increases. As described above, in Comparative Examples 1 to 4 in which the inclination angle θ is relatively large and the inclination of the end blade 26 is relatively steep, a large load is applied to the belt drive motor 63, and malfunction is confirmed in the belt drive motor 63. Was done. On the other hand, in Comparative Example 5 in which the inclination angle θ is relatively small and the inclination of the end blade 26 is relatively gentle, a malfunction of the belt drive motor 63 could not be confirmed. As described above, it was confirmed that the belt drive motor 63 does not malfunction when the inclination angle θ is smaller than 60 °.

Based on the above results, a recording medium having the same size as the width direction of the secondary transfer roller 9, which is the maximum size, can be obtained while preventing image defects with a simple structure that does not require a complicated structure such as a waste toner discharge screw. It was confirmed that the back surface was not stained during printing. Further, it was confirmed that as the inclination of the end blade 26 increases, it becomes easier to suppress stains on the back surface when printing on the maximum size paper. It was also confirmed that the smaller the inclination of the end blade 26, the smaller the load on the belt drive motor 63. Therefore, it was confirmed that the inclination angle θ is preferably larger than 30 ° and smaller than 60 °.

The present invention can be used in an image forming apparatus including a secondary transfer roller that secondarily transfers a toner image primaryly transferred on an intermediate transfer belt to a recording medium. By utilizing the present invention, there is provided an image forming apparatus capable of performing calibration without stopping the image forming operation and suppressing stains on the back surface of the paper when printing on a recording medium having the maximum size. can do.

Pa to Pd Image forming part R1 First image forming area R2 Second image forming area L1 Scraping position L2 Evacuation position 1a to 1d Photoreceptor drum (image carrier)
6a-6d Primary transfer roller (primary transfer member)
8 Intermediate transfer belt 9 Secondary transfer roller (secondary transfer member)
19 Belt cleaning unit (cleaning mechanism)
25 Image density sensor 26 End blade 29 Edge 30 Blade movement mechanism 31 Intermediate transfer unit 36 Waste toner storage container 37 Opening 38 1st storage 39 2nd storage 40 Waste toner transfer pipe 41 Transfer screw 90 Control 100 Image forming device S paper (recording medium)
θ tilt angle

Claims (9)

Multiple image forming parts that form images of different colors,
An endless shape that progresses along the image forming portion and has a first image forming region located at the center in the width direction and a second image forming region located on both sides of the first image forming region in the width direction. With the intermediate transfer belt,
A plurality of primary transfer members that are arranged so as to face the image carriers arranged on the image-forming portions with the intermediate transfer belt interposed therebetween and that primary transfer the toner image formed on the image-bearing body onto the intermediate transfer belt. When,
A secondary transfer member that secondarily transfers the toner image primaryly transferred onto the intermediate transfer belt onto a recording medium, and a secondary transfer member.
The said, which is arranged at a position on the upstream side of the secondary transfer member with respect to the traveling direction of the intermediate transfer belt so as to face the intermediate transfer belt and is formed in the second image forming region on the intermediate transfer belt. An image density sensor that reads the toner image and
An edge portion is pressed against the second image forming region of the intermediate transfer belt, which is arranged between the image density sensor and the secondary transfer member, and the toner image on the intermediate transfer belt is scratched as waste toner. With the end blade to take,
A blade moving mechanism capable of moving the end blade to a scraping position where the edge portion is pressed against the intermediate transfer belt and a retracting position away from the intermediate transfer belt.
A control unit that controls the blade movement mechanism and
In an image forming apparatus equipped with
An image forming apparatus, characterized in that the end blade is inclined so as to approach an end in the width direction of the intermediate transfer belt as it goes from the upstream side to the downstream side in the traveling direction of the intermediate transfer belt. The image forming apparatus according to claim 1, wherein the inclination angle formed between the end blade and the width direction of the intermediate transfer belt orthogonal to the traveling direction is larger than 30 ° and smaller than 60 °. The image forming apparatus according to claim 1 or 2, wherein the end portion of the end blade located on the downstream side in the traveling direction is located outside the end portion in the width direction of the intermediate transfer belt. A waste toner accommodating container having an opening for receiving the waste toner guided by the end blade and capable of accommodating the waste toner scraped off by the end blade in an internal space communicating with the opening. The image forming apparatus according to any one of claims 1 to 3. A cleaning mechanism provided on the downstream side of the secondary transfer member in the traveling direction and removing residual toner adhering to the entire width direction of the intermediate transfer belt is provided.
The image forming apparatus according to claim 4, wherein the waste toner removed by the cleaning mechanism is stored in the waste toner storage container. The waste toner accommodating container was removed by the cleaning mechanism and a first accommodating portion capable of accommodating the waste toner scraped off by the end blade in the internal space from the opening to the bottom located below. A second accommodating portion capable of accommodating the waste toner, a waste toner transfer pipe connecting the first accommodating portion and the second accommodating portion, and a waste toner transfer pipe provided inside the waste toner transfer pipe, and inside the first accommodating portion. The image forming apparatus according to claim 5, further comprising a transfer screw for transferring the waste toner to the second storage container. The image forming apparatus according to any one of claims 1 to 6, wherein the end blade moves between the scraping position and the retracting position along a contact surface with the intermediate transfer belt. The control unit
When the size in the width direction of the recording medium is equal to or less than the size in the width direction of the first image forming region, the patch image formed in the second image forming region is detected by the image density sensor, and the detection result is obtained. Based on this, it is possible to adjust the image formation conditions and perform calibration to correct the density and color shift of the toner image.
The image formation according to any one of claims 1 to 7, wherein the end blade is moved to the scraping position before the calibration is executed, and the end blade is moved to the retracted position after the calibration is completed. Device. The image forming apparatus according to any one of claims 1 to 8, wherein the end blade presses the edge portion from above the intermediate transfer belt toward the upper surface of the intermediate transfer belt.

Images