JP2019174597A - Image forming apparatus - Google Patents

Abstract

To provide provision of an image forming apparatus that can surely detect an area on an image carrier where filming is highly likely to occur and avoid an increase in storage capacity and a delay in processing speed.SOLUTION: An image forming apparatus 100 comprises an image carrier 206, forms a toner on the image carrier, and transfers a toner image to a recording medium, and the image forming apparatus includes: detection means 610 that is arranged opposite to a thrust direction of the image carrier, and can detect a surface state of the entire area to which toner can be attached in the thrust direction of the image carrier; a detection range setting unit 71 that selectively sets a range of detection in the thrust direction performed by the detection means on the basis of history data; a restoration necessity area determination unit 73 that determines whether the surface state of the detection range of the image carrier is necessary to be restored from a result of detection; and a restoration control unit 74 that executes a state restoration operation for the area for which it is determined that restoration is necessary.SELECTED DRAWING: Figure 10

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, the density and position of a detection toner pattern created on a photosensitive drum or an intermediate transfer belt are read and corrected by an optical sensor. ing.

  However, if filming occurs in which additives such as toner and paper accumulate on the intermediate transfer belt in a thin film over time, the glossiness of the intermediate transfer belt decreases and the output of the sensor increases. Therefore, in Patent Document 1, for example, filming on the belt is detected based on the difference between the initial and current belt surfaces, and the belt refreshing operation is performed.

  However, in Patent Document 1, since filming of the entire belt is predicted based on the detection result at a predetermined sensor position on the belt, toner adhesion for suppressing filming is also performed in the entire belt thrust direction, which is inefficient. . If there is a difference in filming depending on the position in the belt thrust direction, an error is likely to occur in detection. Actually, the filming of the belt is often in the form of stripes extending in the circumferential direction of the belt, and the degree of difference depends on the detection position in the thrust direction.

  Therefore, as a means for detecting the filming state on the belt, there is a method using a line sensor that detects the entire area in the thrust direction of the belt (Patent Document 2).

  However, when a line sensor is used, the amount of data becomes enormous, so costs, processing time, and the like become problems. Therefore, in Patent Document 3, after detecting the entire surface, a method of storing only a portion determined to be an abnormal value is performed.

  However, in Patent Document 3, long-term storage at the time of abnormality is partial, but since detection and determination are performed for the entire area, there is a problem that considerable primary storage capacity and processing time are required.

  Accordingly, in view of the above circumstances, the present invention provides an image forming apparatus capable of reliably detecting an area where filming is likely to occur on an image carrier and avoiding an increase in storage capacity and a delay in processing speed. With the goal.

In order to solve the above problems, in one embodiment of the present invention,
In an image forming apparatus comprising an image carrier, forming toner on the image carrier, and transferring a toner image to a recording medium,
A detecting unit that is arranged to face the thrust direction of the image carrier and is capable of detecting the surface state of the entire region to which toner can adhere in the thrust direction of the image carrier;
A detection range setting section for selectively setting the detection range in the thrust direction by the detection means based on history data;
A recovery necessity area determination unit that determines whether the surface state of the detection range of the image carrier needs to be recovered according to a detection result;
An image forming apparatus is provided that includes a recovery control unit that performs a state recovery operation on an area determined to be required to be recovered.

  According to one aspect, in the image forming apparatus, it is possible to reliably detect an area where filming is likely to occur on the image carrier, and to avoid an increase in storage capacity and a delay in processing speed.

1 is a schematic overall configuration diagram showing a printer as an example of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of one image forming unit for generating a toner image in the image forming apparatus of FIG. 1. FIG. 4 is a perspective view illustrating the configuration of an intermediate transfer unit and the position of a detection unit according to an embodiment of the invention. Sectional drawing which shows an example of the support structure of the line sensor which concerns on this invention. The figure which shows the 1st structural example of the line sensor which concerns on this invention. The figure which shows the 2nd structural example of the line sensor which concerns on this invention. The figure which shows the 3rd structural example of the line sensor which concerns on this invention. 1 is a hardware block diagram of a control system of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a functional block diagram of a control unit related to detection and recovery of an intermediate transfer belt in an embodiment of the present invention. The figure which shows the detection object range on an intermediate transfer belt by the line sensor of this invention. 6 is a control flowchart relating to detection and recovery of the intermediate transfer belt according to the present invention.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and redundant description may be omitted.

<Overall configuration of image forming apparatus>
FIG. 1 is a diagram illustrating a schematic overall configuration of a printer that is an example of an image forming apparatus according to the present invention. Although FIG. 1 shows an example of a printer that receives image data as an example of an image forming apparatus to which the present invention can be applied, the image forming apparatus to which the present invention can be applied is an electrophotographic image forming apparatus. The apparatus may be a copying machine that performs copying, or a multi-function peripheral (MFP) that includes functions such as copying, a printer, a scanner, and a FAX.

  An image forming apparatus 100 that is a printer of FIG. 1 includes four image forming units 1Y, 1C, and 1M for generating toner images of yellow, magenta, cyan, and black (hereinafter referred to as Y, C, M, and K). , 1K.

  These image forming units 1 use different colors of Y toner, C toner, M toner, and K toner as image forming substances for forming an image, but the other configurations are the same.

  FIG. 2 is a schematic diagram showing a configuration of an image forming unit (process unit) 1Y for generating a Y toner image. Taking the image forming unit 1Y for generating a Y toner image as an example, the image forming unit 1Y has a photoreceptor unit 2Y and a developing device (developing means) 7Y. The photosensitive unit 2Y and the developing device 7Y are detachably attached to the image forming apparatus main body integrally as the image forming unit 1Y. However, the developing device 7Y can be attached to and detached from the photoreceptor unit 2Y in a state where it is detached from the image forming apparatus main body.

  In FIG. 1, an optical writing device 20 is disposed below the image forming units 1Y, 1C, 1M, and 1K. The optical writing device 20 is a latent image forming unit, and irradiates the photoconductors 3Y, 3C, 3M, and 3K of the image forming units 1Y, 1C, 1M, and 1K with laser light L based on image information. Thereby, electrostatic latent images for Y, C, M, and K are formed on the photoreceptors 3Y, 3C, 3M, and 3K.

  The optical writing device 20 irradiates the photoreceptors 3Y, 3C, 3M, and 3K through a plurality of optical lenses and mirrors while deflecting the laser light L emitted from the light source by the polygon mirror 21 that is rotationally driven by a motor. To do. As the optical writing device, a device that performs optical scanning using an LED array can be adopted instead of the device having this configuration.

  A first paper feed cassette 31 and a second paper feed cassette 32 are arranged below the optical writing device 20 so as to overlap in the vertical direction. In each of these paper feed cassettes, a plurality of sheets P of recording media (recording sheets) are accommodated in a bundle of sheets, and the top sheet P includes a first paper feed roller. 31a and the second paper feed roller 32a are in contact with each other. When the first paper feed roller 31a is driven to rotate counterclockwise in the figure by driving means (not shown), the uppermost paper P in the first paper feed cassette 31 is vertically oriented on the right side of the cassette in the figure. The paper is discharged toward the paper feed path 33 arranged so as to extend. Further, when the second paper feed roller 32 a is driven to rotate counterclockwise in the drawing by a driving means (not shown), the uppermost paper P in the second paper feed cassette 32 is directed toward the paper feed path 33. Discharged. A plurality of transport roller pairs 34 are arranged in the paper feed path 33, and the paper P fed into the paper feed path 33 is sandwiched between the rollers of the transport roller pair 34 while being fed. The inside is conveyed from the lower side to the upper side in the figure.

  A registration roller pair 35 is disposed at the end of the paper feed path 33. The registration roller pair 35 temporarily stops the rotation of both rollers as soon as the paper P sent from the conveyance roller pair 34 is sandwiched between the rollers. Then, the paper P is sent out to a secondary transfer nip described later at an appropriate timing.

  Above the image forming units 1Y, 1C, 1M, and 1K in the figure, an intermediate transfer unit 40 that is a transfer device that is endlessly moved counterclockwise in the figure while stretching the intermediate transfer belt 41 is disposed. Yes. In addition to the intermediate transfer belt 41, the intermediate transfer unit 40 includes a belt cleaning unit 42, a first bracket 43, a second bracket 44, and the like. Also provided are four primary transfer rollers 45Y, 45C, 45M, 45K, a secondary transfer backup roller 46, a drive roller 47, an auxiliary roller 48, a tension roller 49, and the like. The intermediate transfer belt 41 is endlessly moved counterclockwise in the figure by the rotational drive of the drive roller 47 while being stretched around these eight rollers.

  The four primary transfer rollers 45Y, 45C, 45M, and 45K sandwich the intermediate transfer belt 41 that is moved endlessly in this manner from the photoreceptors 3Y, 3C, 3M, and 3K to form primary transfer nips. . Then, a transfer bias having a polarity opposite to that of the toner (for example, plus) is applied to the back surface (loop inner peripheral surface) of the intermediate transfer belt 41. The intermediate transfer belt 41 passes through the primary transfer nips for each of the colors Y, C, M, and K in accordance with the endless movement of the intermediate transfer belt 41, and on the photoreceptor 3Y, 3C, 3M, 3K on the front surface. The Y toner image, the C toner image, the M toner image, and the K toner image are primarily transferred so as to overlap each other. As a result, a four-color superimposed toner image (hereinafter referred to as a four-color toner image) is formed on the intermediate transfer belt 41.

  The secondary transfer backup roller 46 sandwiches the intermediate transfer belt 41 with the secondary transfer roller 50 disposed outside the loop of the intermediate transfer belt 41 to form a secondary transfer nip. The registration roller pair 35 feeds the sheet P sandwiched between the rollers toward the secondary transfer nip at a timing to synchronize with the four-color toner image on the intermediate transfer belt 41. The four-color toner image on the intermediate transfer belt 41 is affected by the secondary transfer electric field formed between the secondary transfer roller 50 to which the secondary transfer bias is applied and the secondary transfer backup roller 46, and the influence of the nip pressure. Then, the secondary transfer is collectively performed on the paper P in the secondary transfer nip. Then, combined with the white color of the paper P, a full color toner image is obtained.

  The residual transfer toner remaining on the intermediate transfer belt 41 without being transferred to the paper P even after passing through the secondary transfer nip is cleaned by the belt cleaning unit 42. The belt cleaning unit 42 makes the cleaning blade 42a abut against the front surface of the intermediate transfer belt 41, thereby scraping off and removing the transfer residual toner on the belt.

  A fixing device 60 is disposed above the secondary transfer nip in the drawing. The fixing device shown in FIG. 1 has a belt fixing configuration. A heater is provided inside the belt, and an unfixed image conveyed to the nip portion is fixed by raising the belt temperature with the heat. The example of the fixing device is not limited to the belt fixing method of FIG. 1, but may be a roller fixing configuration in which the nip is configured by a roller.

  Process control is performed to detect the state of toner adhering to the intermediate transfer belt 41 and the surface state of the intermediate transfer belt, and to control the state of image formation. On the intermediate transfer belt, a line sensor 610 as a detection unit is arranged. During this process control, the secondary transfer backup roller 46 and the secondary transfer roller 50 are separated from each other, and the toner image attached on the intermediate transfer belt is transferred to the paper P or contacts the secondary transfer roller. Without moving, it moves to the position of the line sensor 610 and is detected.

  The line sensor 610 (detection means) includes, for example, a light irradiation device and a reflected light detection device that are long in the depth direction in the figure and correspond to the width of the intermediate transfer belt 41. The arrangement and internal configuration of the detection means will be described with reference to FIGS.

<Intermediate transfer belt surface detection>
Next, the detection of various toner images formed on the front surface of the intermediate transfer unit and the driving system of the intermediate transfer unit will be described with reference to FIG.

  FIG. 3 is a perspective view illustrating the configuration of the intermediate transfer unit and the position of the line sensor according to an embodiment of the present invention. The configuration of the intermediate transfer unit 200 shown in FIG. 3 and the configuration of the intermediate transfer unit 40 shown in FIG. 1 are different in the transfer position and the number and arrangement of rollers. You may use the structure of. Since the intermediate transfer unit in FIG. 1 and the intermediate transfer unit in FIG. 3 are different in arrangement and configuration, different reference numerals are given, but the functions are the same. In FIG. 3, the four primary transfer rollers 45Y, 45C, 45M, and 45K shown in FIG. 1 are not shown.

  Of the entire area of the intermediate transfer belt 206 in the circumferential direction, a line sensor 610 as a detection means (optical detection means) is disposed above the upper stretched surface wound around the drive roller 201 and the cleaning backup roller 202. The front surface 206a of the 206 is opposed to the surface 206a.

  A cleaning blade 210 is disposed outside the intermediate transfer belt 206 to which tension is applied by the cleaning backup roller 202.

  The line sensor 610 has an array structure that extends in the main scanning direction (belt width direction) indicated by the symbol W and has a plurality of light sources, condensing lenses, and light receiving elements arranged linearly in the main scanning direction W. The main scanning direction W corresponds to the thrust direction with respect to the rotation direction (movement direction M) of the intermediate transfer belt 206.

  A symbol W1 in FIG. 3 indicates a sub-scanning direction orthogonal to the main scanning direction W. In the figure, the hatched portion indicates the image formable area IE on the front surface 206a of the intermediate transfer belt 206, and 206b indicates the background portion.

  As shown in FIG. 3, the intermediate transfer unit 200 includes a belt drive motor 211 as a drive source for driving the drive roller 201 to move the intermediate transfer belt 206 endlessly. In the vicinity of the drive roller 201, a position information detection sensor 213 as a position information detection means for detecting the position of the intermediate transfer belt 206 and the toner image in the sub scanning direction W1 is disposed.

  FIG. 4 is a cross-sectional view showing an example of a support structure for the line sensor 610 of the present invention.

  In the configuration example of the line sensor 610 shown in FIG. 4, one light source 611 composed of an LED as a light emitting element that emits white light and a main light source 611 extending in the main scanning direction W are arranged to reflect red, green, and blue reflected light. Three light receiving elements 612R, 612G, 612B for receiving light and a light receiving lens 613 are supported by a casing 614 as one cell. In this example, for example, the line sensor 610 is configured by linearly arranging a plurality of unit cells having a predetermined length shown in FIG. 3 in the main scanning direction W of FIG.

  In the present embodiment, a contact image sensor (CIS) which is one of color sensors is used as an element constituting each sensor of the line sensor 610. The line sensor 610 may be a CCD (Charge Coupled Device) image sensor (camera) instead of the CIS.

As a configuration of the line sensor, in FIG. 3, a plurality of unit cells of a predetermined length are configured to be linearly arranged in the main scanning direction W, but the line sensor has other shapes,
・ One line array sensor (see Fig. 7)
・ Linear array of array sensors of a certain length ・ Linear array of optical sensors (cells) of a certain length (eg staggered)
-It may be configured by moving an optical sensor of a predetermined length and securing a detection area.

  Regardless of the shape, the line sensor used in the present invention detects the image formable area IE (the entire shaded area in FIG. 3) in the main scanning direction of the opposing intermediate transfer belt 206 (image carrier). This is an optical sensor (optical sensor) having a configuration that can be used. That is, when the intermediate transfer belt 206 rotates and is driven in the circumferential direction, the line sensor as the detection unit can detect the entire image formable area.

  The sensor color of the line sensor 610 is a white light source that can receive RGB light on the light receiving side. The light source may be a color sensor using a light source of three colors (red, green, and blue) or an arbitrary light source instead of one color of a white light source (LED). Alternatively, it may be a conventional infrared light receiving and emitting sensor.

  For example, the CIS line sensor 610 has an amplifier for each unit cell arranged in a straight line in the main scanning direction W, and generation of electrical noise due to reading of an electrical signal optically converted by the light receiving element 132 is suppressed. Yes. This electrical signal is input to the control unit 500 shown in FIG.

  Here, general image density adjustment will be described. In image density adjustment (process control), the light emitted from the light emitting element of the reflective optical sensor is reflected on the background surface of the intermediate transfer belt where the toner is not attached, and the reflected light is received by the light receiving element. The amount of received light is obtained according to.

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

  Using the amount of received light at the background portion of the surface of the intermediate transfer belt as a reference value, the reference value is compared with the amount of received light in the reference toner image to grasp the toner adhesion amount per unit area of the reference toner image.

  Based on the grasped toner adhesion amount, the photosensitive drum charging potential, the developing bias, the optical writing intensity to the photosensitive drum, the control target value of the developer toner density, etc. are adjusted so that the desired toner adhesion amount is obtained. Adjust the image conditions.

  In the color misregistration correction, a toner pattern having an angle with respect to the main scanning direction is formed, and a positional deviation between the main scanning direction and the sub scanning direction is detected and corrected.

  A specific configuration example of a line sensor for appropriately performing density adjustment and color misregistration correction will be described below.

<Configuration of detection means>
FIG. 5 is a diagram showing a first configuration example of the line sensor 610 according to the present invention. In FIG. 5, the line sensor 610 includes a light reflection sensor (photo reflector) 110, an amplifier circuit 120, an arithmetic circuit 130, and a signal generation circuit 140. The amplifier circuit 120 amplifies the electric signal from the light reflection sensor 110. The arithmetic circuit 130 performs predetermined arithmetic processing based on the signal amplified by the amplifier circuit 120. The signal generation circuit 140 generates a signal for optical writing control based on the calculation output from the calculation circuit 130 and outputs the signal to the control circuit CON of the control unit 500 of the image forming apparatus 100.

  The light reflection sensor 110 includes an LED (light emitting diode) 101 as a light source, a condenser lens 102, a photoelectric conversion element 103, and an imaging lens 104. The condensing lens 102 condenses the light emitted from the LED 101 into a light beam having a predetermined beam diameter. The photoelectric conversion element 103 is a light receiving element, and receives reflected light from the image pattern 151 on the intermediate transfer belt 206 and converts it into an electrical signal. The imaging lens 104 images the reflected light from the image pattern 151 on the imaging surface of the photoelectric conversion element 103.

  FIG. 6 is a diagram showing a second configuration example of the line sensor 610 according to the present invention. In the example of FIG. 5 described above, the unevenness of the image density is detected by the sensor composed of the photoelectric conversion element 103 that detects the reflected light by irradiating the projection spot with a sufficiently small condensing lens 102. In the example of FIG. 6, a light source (LED 101) that can illuminate a wide range of the light projection area is used, and the reflected light on the image reflected from the image pattern 151 and incident on the photoelectric conversion element 103 is made into a minute area.

  FIG. 7 is a diagram showing a third configuration example of the line sensor according to the present invention. In the example of FIG. 7, the line sensor 610 includes an equal-magnification imaging element 160 and an arrayed light receiving element 161 instead of the imaging lens 104 and the photoelectric conversion element 103. The equal-magnification imaging element 160 is, for example, a SELFOC (registered trademark) lens array manufactured by Nippon Sheet Glass. The array-shaped light receiving element 161 includes light receiving elements arranged in an array, for example, a CMOS light receiving element in which several tens to several hundreds of pixels are arranged at 300 dpi (CMOS linear sensor array manufactured by TAOS).

  As shown in FIG. 7, when the reflected light from each minute region of the detection image pattern 151 illuminated in a wide range is incident on the arrayed light receiving element 161 through the equal magnification imaging element 160, Two-dimensional image information can be captured without performing spot light scanning. If two-dimensional image information is used, there is an advantage in that very accurate image density unevenness information can be obtained as compared with one-dimensional image information.

  Further, even in the case of the configuration as shown in FIGS. 5 and 6, two-dimensional image information can be collected by scanning spot light in a direction crossing the moving direction of the image carrier with a drive mirror (not shown) or the like. .

  When density adjustment and color misregistration correction are performed using the line sensor configured as described above, the output of the optical sensor is adjusted so that a predetermined amount of received light is obtained at the background portion of the surface of the intermediate transfer belt. That is, the optical sensor is calibrated so that a predetermined amount of received light can be obtained by adjusting the output (current value) of the light emitting element.

  However, if filming occurs in which an additive such as toner or paper accumulates on the intermediate transfer belt as a thin film over time, the glossiness of the belt decreases and the output of the sensor increases. That is, since the amount of reflected light decreases due to filming, in order to obtain a predetermined amount of received light, it is necessary to increase the current value (forward current If) that flows to a light emitting element such as an LED, which consumes power. The amount will increase. Therefore, in the present invention, the following control is performed.

<Control block>
Next, a control system of the image forming apparatus 100 will be described. FIG. 8 is a block diagram of a control system of the image forming apparatus according to the embodiment of the present invention.

  The image forming apparatus 100 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 temporarily 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. 8 shows only major ones of these peripheral devices.

  Further, the control unit 500 includes toner density sensors 108Y, 108C, 108M, and 108K for each color, a line sensor 610, a belt drive motor 211, a position information detection sensor 213, a drive unit 511 for each developing device 7, and an optical writing device 20. The drive unit 512, the drive unit 513 of each toner supply device, and various power supply units 514 are connected via a signal line 510. The various sensors output the detected detection values to the control unit 500, and the control unit 500 temporarily stores the output various detection values in the RAM 502.

(Filming)
In general, the filming of the intermediate transfer belt differs depending on how the intermediate transfer belt is used. In the conventional method of partially judging the belt surface state by detection with two to several sensors. There has been a problem that it is impossible to detect the occurrence of filming other than in the sensor portion. Further, if the state of the entire area is frequently detected by the line sensor, the memory capacity for storing information becomes enormous.

  Here, since filming occurs with time, a portion that is likely to occur and a portion that is unlikely to occur are formed depending on the tendency of the film to be used on the intermediate transfer belt. By selectively detecting an easily occurring portion, it is possible to detect and reduce filming of the intermediate transfer belt at an early stage.

  When initial filming is detected, the toner is supplied onto the detected intermediate transfer belt, and when the toner is cleaned by a cleaning blade disposed in contact with the intermediate transfer belt, the filming is performed together with the toner. Substances are also reduced. The toner supply of the detected portion onto the intermediate transfer belt is performed as a state recovery operation (refresh operation) by supplying the toner to the photosensitive member with a developing device and attaching it to the intermediate transfer member through primary transfer.

<Control unit>
FIG. 9 is a functional block diagram of a control unit related to detection / recovery of the intermediate transfer belt (image carrier) in the embodiment of the present invention.

  The control unit 70 of the present invention includes a detection range setting unit 71, a filming presence / absence determination unit 72, a recovery necessity region determination unit 73, a toner adhesion control unit 74, a paper width history storage unit 75, and a paper type history. The storage unit 76, the detection range history storage unit 77, the filming occurrence position history storage unit 78, and the recovery operation history storage unit 79 are executable.

  The detection range setting unit 71, the filming presence / absence determination unit 72, the recovery necessity region determination unit 73, and the toner adhesion control unit 74 are realized by the CPU 501 in FIG. The paper width history storage unit 75, the paper type history storage unit 76, the detection range history storage unit 77, the filming occurrence position history storage unit 78, and the recovery operation history storage unit 79 are a RAM 502 or a rewritable storage medium. It is realized by NVRAM.

  The detection range setting unit 71 selectively sets the detection range in the thrust direction of the intermediate transfer belts 206 and 41 by the line sensor (detection unit) 610 based on the history data. The history data (knowledge data) is stored in any one of the sheet width history storage unit 75, the sheet type history storage unit 76, the detection range history storage unit 77, the filming occurrence position history storage unit 78, and the recovery operation history storage unit 79. Information.

  Specifically, the detection range setting unit 71 determines a portion where filming is likely to occur due to usage in the intermediate transfer belt and a portion where filming is difficult to occur, based on usage history information (history data), and detects a detection target range (detection). Range). The ease with which filming occurs mainly depends on the amount of toner attached to the relevant part, and there is a tendency that filming is less likely to occur in the part where the toner is heavily attached. In addition, depending on the type of paper P to be used, the filming occurrence state may differ depending on the filler contained in the paper. Based on these pieces of information, the image formable region (range IE) is divided and the detection target range of the part to be detected is selected. Details will be described with reference to FIG.

  The filming presence / absence determination unit 72 determines whether filming has occurred based on the detection result of the line sensor 610 in the set detection range.

  Here, the detection range in which detection by the line sensor 610 is performed is selected from among the region divisions, but the filming detection itself depends on the resolution of the sensor and is performed in units smaller than the division width. Therefore, the position (region) where filming has occurred can be determined in detail on a pixel basis.

  The recovery necessity area determination unit 73 refreshes for each position by determining whether or not the surface state of the detection target range where the detection has been performed includes an area that requires state recovery (recovery area required). It is determined whether (state recovery operation) is necessary.

  For example, in order to avoid the influence of noise as a judgment example of the recovery operation, refer to the current filming occurrence result and the filming occurrence position / count history, and in the inspection, at the same position more than a predetermined continuous number When the occurrence of filming is detected, it is determined that the state recovery operation is necessary. Alternatively, as soon as filming is detected once, it may be determined that a state recovery operation is necessary.

  The toner adhesion control unit 74 is a recovery control unit, and a developing device of any color in a portion (region) on the intermediate transfer belts 206 and 41 determined to require state recovery by the recovery necessity region determination unit 73. Execute or set the state recovery operation (toner adhesion operation).

  Here, in the image forming apparatus, if the amount of toner consumed from the developing device is extremely small, the toner stays in the developing device for a long time, which may adversely affect the developing characteristics. For this reason, in such a developing device, it is desirable to execute an operation of releasing toner when there is no image formation for a long time.

  Therefore, in the present invention, as the state recovery operation, the toner is supplied onto the intermediate transfer belt with toner of a color with a small amount of use, and thus the toner adhesion operation for suppressing filming on the surface of the intermediate transfer belt is performed. The toner refresh (replacement) operation in the developing device can be performed simultaneously.

  On the other hand, from the viewpoint of system load, in the case of monochrome printing, the toner used to supply toner onto the intermediate transfer belt is black toner. Since the color photoreceptor and development are stopped while the black image forming unit is operating during monochrome printing, the recovery operation is also carried out with black toner, so that the color photoreceptor and development are extra for this operation. It is possible to suppress deterioration over time without operating.

  Further, since the filming detection part is implemented in a fine unit depending on the resolution of the sensor, the toner adhesion for filming removal is caused by the sensor part (a part of the detection range) where the filming is detected. This is limited to a few pixels where filming actually occurs corresponding to (position).

  The paper width history storage unit 75 accumulates and stores information on the paper width of the used paper P. As the history data for selecting the detection area, data based on the history of the sheet passing width, which is the width that the sheet P has passed, is used to reliably detect a portion where filming is likely to occur due to the sheet passing width. Can be done.

  The paper type history storage unit 76 stores and stores information on the paper type of the used paper P. A portion where filming is likely to occur depending on the paper type of the paper passing by using data based on the paper type history of the paper passing that is the type of the paper P passed as the detection area selection history data. Can be reliably detected.

  The detection range history storage unit 77 accumulates and stores the detected areas.

  The filming occurrence position history storage unit 78 accumulates and stores information on the generated filming position. For example, the number of filming occurrence detections at each position in the detection target area is counted and stored, and the number of counts at that position is increased with respect to the position where filming is detected this time. Information on the accumulated filming position and the number of occurrence detections is used to determine whether or not there is a recovery operation.

  The recovery operation history storage unit 79 accumulates and stores information on the color of the state recovery operation that has been performed and information on the range in the thrust direction in which the state recovery operation has been performed.

  Hereinafter, division of the detection range in the thrust direction of the intermediate transfer belt 206 by the line sensor 610 set by the detection range setting unit 71 in the present invention will be described.

<Example of area division>
An example of detection area division selected by the line sensor of the present invention is shown in FIG. FIG. 9 is a diagram illustrating a detection target range of the intermediate transfer belt 206 by the line sensor 610. In FIG. 9, 303, 304, 305, and 306 indicate paper passing widths. In this example, 303 indicates the A5 short end width, 304 indicates the A4 short end width, 305 indicates the B4 short end width, and 306 indicates the A3 short end width. , IE indicates the range of the image formable area (entire area).

In the example of FIG.
A: Region outside A3 short end width 306 B: Region inside A3 short end width 306 and outside B4 short end width 305 C: Inside B4 short end width 305 and inside A4 short end width 304 Outside area D: inside A4 short end width 304 and inside A5 short end width 303 E: inside area (center area) of A5 short end width 303
Is set.

  The detection range setting unit 71 determines a detection range as a detection target in which filming detection is performed based on the width and frequency of the paper P to be passed. In the example of FIG. 10, since the paper always passes through the central area E when the paper is passed, and the toner adheres if an image is formed, the frequency of performing the filming is the lowest because the toner adhesion frequency is the highest. become. On the other hand, in the outermost region A, the frequency of filming is the highest because the frequency of toner adhesion is low because there are few opportunities for image formation.

  For example, in the case of a machine that mainly uses B4, since the possibility of filming in areas A and B where B4 paper does not contact is higher than in other areas, the detection frequency is compared with other areas. It is high. The detection timing is performed simultaneously with the process control. Table 1 shows a setting example of the usage ratio of the paper width and the determination ratio.

また、通紙される用紙Ｐの種類によっては、用紙が通過することで、中間転写ベルトがフィルミングしやすくなる場合がある。そのような、性質の用紙の使用が明らかな場合には、該当の用紙の通紙幅に合わせて、フィルミング検知を行う。

Further, depending on the type of the paper P to be passed, the intermediate transfer belt may be easily filmed by the passage of the paper. When it is clear that such a characteristic sheet is used, filming detection is performed in accordance with the sheet passing width of the corresponding sheet.

  If the sheet that is likely to cause filming is A5 size, after setting as shown in Table 1, the frequency of the central region E is increased to increase the number of detections. In this way, by adopting a configuration that does not detect the entire area at the same time, the storage capacity can be reduced, and filming can be detected efficiently.

  When filming is detected, a toner image is formed on the photoreceptor corresponding to the area where filming is detected based on the information. The toner image is formed from the end of the next job in which filming is detected until the amount of toner adhered reaches the target value after each job.

  As described above, the area division detected by the line sensor is set in advance corresponding to the paper width, and the software configuration is simplified and the processing load can be reduced compared to the case where the area division is arbitrarily performed.

  Note that the area division can be changed depending on the situation without being set in advance. By assigning a detection range to the part where filming was detected as a history before carrying out detection, and increasing the frequency of detection, the trend due to the user's usage mode etc. is reflected in the selection of the detection range, More reliable detection is possible.

<Control flow>
FIG. 11 is a control flow relating to detection and recovery of the intermediate transfer belt of the present invention.

  In S1 (step 1), the detection range setting unit 71 selects a detection target range based on the history data. As described above, the data used at this time is used as a selection criterion by combining one or a plurality of paper width histories, paper types, filming occurrence position histories, state recovery operation histories, and the like.

  In S2, the line sensor 610 performs filming detection on the selected detection target range.

  In S <b> 3, the filming presence / absence determination unit 72 determines whether or not filming has occurred in the set detection target range.

  When it is determined that there is no filming in S3 (No), the detection target range is stored in S4, and the flow ends.

  On the other hand, when it is determined in S3 that at least a part of the detection target range (detection range) has filming (Yes), the detection target range is stored in S5, and the filming occurrence position history storage unit 78 stores the filming. 1 is added to the number of occurrence detections at the occurrence position, and the filming occurrence history at that position is stored.

  Then, in S6, the recovery necessity area determination unit 73 refers to the counted filming occurrence history, and at least part of the detection target range detected by the intermediate transfer belts 206 and 41, the surface Determine if there is an area whose state requires state recovery.

  If it is determined that the state recovery operation is not necessary for all the detection target ranges detected this time (No in S6), the inspection flow is terminated.

  If there is an area where it is determined that the state recovery operation is necessary (Yes in S6), the toner adhesion control unit 74 sets the toner color used in the state recovery operation in S7.

  In the state recovery operation, it is sufficient that the toner is supplied onto the intermediate transfer belt, so the color is not limited. Therefore, for example, when setting a color to be used for the state recovery operation in S7, in an image forming apparatus that uses a plurality of color toners, the toner used for the state recovery operation has the smallest usage amount based on the toner usage history. By using color toners, it is possible to simultaneously reduce the deterioration of each color toner inside the developing device.

  On the other hand, in monochrome printing, the toner used for the state recovery operation is black toner, so that the state recovery operation is performed without operating the color image forming unit, and the color image forming unit is not deteriorated. Can be suppressed.

  In step S8, the state recovery operation is performed in which toner is attached to an area where the state recovery operation is determined to be necessary, and then wiped with the cleaning blades 210 and 42a.

  Here, as the state recovery operation in S8, the toner consumption is minimized by selectively attaching the toner to the areas of the surfaces of the transfer belts 206 and 41 that are determined to be in the required state recovery. Thus, the occurrence of filming on the belt surface can be reduced.

  Then, the area where the state recovery operation is performed in S9 is stored as a recovery operation execution history.

  By selecting and setting the detection target range by the line sensor based on the history data by the above-described control, it is possible to reliably detect the portion of the image carrier that is highly likely to cause filming. Since the detection target range is limited by selection, it is possible to avoid an increase in storage capacity for holding data and an increase in processing speed.

  When it is determined that the surface state of the image carrier is “required”, it is possible to provide a stable image over time by performing a state recovery operation by attaching toner to the determined region. Is possible.

  As described above, in the image forming apparatus of the present invention, it is possible to reliably detect an area where filming is highly likely to occur on the image carrier, and avoid an increase in storage capacity and a delay in processing speed.

  The preferred embodiment of the present invention has been described in detail above, but the present invention is not limited to the specific embodiment, and within the scope of the gist of the embodiment of the present invention described in the claims, Various modifications and changes are possible.

7 Developing device (Developing means)
40,200 Intermediate transfer unit (transfer device)
41,206 Intermediate transfer belt (image carrier)
42a, 210 Cleaning blade 71 Detection range setting unit 72 Filming presence / absence determination unit 73 Recovery necessary / unnecessary region determination unit 74 Toner adhesion control unit (recovery operation control unit)
75 Paper width history storage unit 76 Paper type history storage unit 77 Detection range history storage unit 78 Filming occurrence position history storage unit 79 Recovery operation history storage unit 90,610 Line sensor (detection means)
100 printer (image forming apparatus)
500 Control unit W Main scanning direction (thrust direction)
P paper (recording medium)

Japanese Patent Laid-Open No. 2006-20970 JP 2005-106919 A JP, 2006-148781, A

Claims (8)

In an image forming apparatus comprising an image carrier, forming toner on the image carrier, and transferring a toner image to a recording medium,
A detecting unit that is arranged to face the thrust direction of the image carrier and is capable of detecting the surface state of the entire region to which toner can adhere in the thrust direction of the image carrier;
A detection range setting section for selectively setting the detection range in the thrust direction by the detection means based on history data;
A recovery necessity area determination unit that determines whether the surface state of the detection range of the image carrier needs to be recovered according to a detection result;
An image forming apparatus comprising: a recovery control unit configured to perform a state recovery operation on an area determined to be required to be recovered. The image forming apparatus according to claim 1, wherein the history data is history information of a width of the recording medium. The image forming apparatus according to claim 1, wherein the history data is history information of a type of the recording medium. The image forming apparatus according to claim 1, wherein the history data is a filming occurrence history for each position. The image forming apparatus according to claim 1, wherein the history data is a recovery operation execution history. The image forming apparatus according to any one of claims 1 to 5, wherein the state recovery operation is to attach toner to an area determined to be required to be recovered. A plurality of developing means for supplying different color toners to the image carrier;
The image forming apparatus according to claim 6, wherein the toner used in the state recovery operation is a toner having a color that is least used based on a toner usage history. A plurality of developing means for supplying different color toners to the image carrier;
The image forming apparatus according to claim 6, wherein the toner used in the state recovery operation when performing monochrome printing is black toner.

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