JP2010145848A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve such a problem that when contamination of a reflecting surface is determined based on a laser beam reflected by a rotary polygon mirror, which is detected by a single PD sensor, the contamination of the reflecting surface is detected, however, variations in the quantity of light reflected within a reflecting surface and variations of each reflecting surface cannot be detected, which requires to stop an image forming apparatus at a point in time that the contamination is detected, resulting in a long downtime. <P>SOLUTION: The image forming apparatus obtains a first image pattern formed by being reflected by a first reflecting surface of the rotary polygon mirror, and a second image pattern formed by being reflected by a second reflecting surface instead of the first reflecting surface. On the basis of results obtained by reading the thus formed first and second image patterns, variations in the contamination of the reflecting surfaces of the rotary polygon mirror are detected. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that forms an image by scanning an image carrier with a laser beam such as a laser printer.

  In an optical scanning device used in an electrophotographic image forming apparatus, a laser light source is driven in accordance with input image data to emit laser light, and a rotary polygon mirror (polygon mirror) having a plurality of reflecting surfaces is used. Deflection scanning is performed by the deflection member. An electrostatic latent image is formed in the main scanning direction (axial direction of the photosensitive member) of the photosensitive member as an image carrier provided in the image forming apparatus by the laser beam subjected to the deflection scanning. In the optical scanning device, the laser beam deflected and scanned by the rotary polygon mirror is incident on a light detection sensor (which is also composed of a photodiode and also called a BD sensor), and is based on a main scanning synchronization signal output from the light detection sensor. The start timing for forming the electrostatic latent image on the photosensitive member is controlled.

  In such an optical scanning device, in general, the reflection surface is not contaminated by dust or the like in the image forming apparatus. However, when the dust or the like enters, the rotary polygon mirror rotates at high speed. It is known that the reflecting surface is contaminated by the entrainment of dust or the like.

  As shown in FIG. 16, an air flow B 'is generated in a direction opposite to the direction A' in which the rotary polygon mirror 33 'rotates. For this reason, an air current is entrained on the deflection scanning start side (the bold line portion in the figure) on the reflection surface of the rotating polygon mirror 33 ', and contamination starts from the scanning start side on the reflection surface of the rotation polygon mirror.

Therefore, an optical scanning device has been proposed that determines whether or not the reflecting surface of the rotary polygon mirror is dirty (see, for example, Patent Document 1). Specifically, the laser beam reflected by the rotating polygon mirror is detected by a light detection sensor (PD sensor), and reflected based on the relationship between the output value of the PD sensor measured in advance and the amount of dirt on the rotating polygon mirror. Determine that the surface is dirty.
JP 2006-011300 A

  However, in the method proposed in Patent Document 1 above, the reflection of the reflecting surface of the rotating polygon mirror is compared by comparing the laser light reflected by the rotating polygon mirror detected by the PD sensor with the output value of the PD sensor measured in advance. Judging. In other words, it detects that the reflecting surface is dirty, but does not consider the variation in the amount of reflected light within the reflecting surface or the amount of reflected light on each reflecting surface, and stops the image forming apparatus when it detects that it is dirty. Was.

  It is known that when the reflecting surface becomes dirty, the amount of reflected light tends to vary at each reflection position. If the amount of reflected light within the same reflecting surface varies greatly, the density of the image will partially fluctuate, resulting in partial thinning. Phenomenon occurs, and the image quality deteriorates. If the amount of reflected light varies from one reflecting surface to another, a writing position shift (image fluctuation) in the main scanning direction occurs in the sub-scanning direction (photoconductor rotation direction).

  When such a situation occurs, it is necessary for the service person to perform maintenance, and it is preferable to stop the image forming apparatus until the service person arrives.

  On the other hand, even if there is a decrease in the amount of reflected light, if the amount of reflected light is uniformly reduced regardless of the reflection position, even if there is a variation in density, the image quality will be degraded. Is inconspicuous. Even if there is a decrease in the amount of reflected light, if the amount of reflected light is uniformly reduced regardless of the reflecting surface, even if there is a deviation in the start position, the image quality will deteriorate. Is inconspicuous.

  In such a case, even if the service person needs to perform maintenance, the time when the image forming apparatus cannot be used is shortened if the image forming apparatus is operated without stopping until the service person arrives at the maintenance. Therefore, it is preferable. However, such a situation cannot be distinguished by the method proposed in Patent Document 1.

  Therefore, the method proposed in Patent Document 1 has a problem in that the downtime of the image forming apparatus becomes long because the image forming apparatus is stopped when it is detected that it is dirty.

  Therefore, the present invention can detect the state of dirt with high accuracy by detecting the variation in the amount of reflected light for each reflecting surface. Another object of the present invention is to provide an image forming apparatus capable of accurately detecting the state of dirt at an early stage.

  In order to solve such problems, the present invention forms an image on an image carrier by reflecting a laser beam on a rotating polygon mirror having a reflecting surface and transfers the formed image onto a transfer material. The first image pattern formed by reflecting on the first reflecting surface of the rotary polygon mirror and the second image pattern formed by reflecting on the second reflecting surface without using the first reflecting surface. An image pattern generating unit for forming the image pattern, a reading unit for reading the first image pattern and the second image pattern formed by the image pattern generating unit, and based on a result read by the reading unit And detecting means for detecting variation in dirt on the reflecting surface of the rotary polygon mirror.

  According to the present invention, it is possible to detect the state of dirt with high accuracy at an early stage by detecting the variation in the amount of reflected light on the reflecting surface. Also, by reading and comparing the density of the image pattern, it becomes possible to detect the relative degree of contamination of each reflecting surface of the rotary polygon mirror, and it is possible to predict the response and replacement by cleaning before the contamination becomes severe. .

  Preferred embodiments of the present invention will be exemplarily described in detail below with reference to the drawings. In addition, this invention is not limited only to a following example.

<Schematic configuration of image forming apparatus>
FIG. 1 is a schematic cross-sectional view of the entire image forming apparatus as an embodiment of the present invention. A basic operation of the image forming apparatus 100 will be described with reference to FIG. The image forming apparatus 100 includes a document reading unit R and a printer unit P. In the document reading unit R, the documents stacked on the document feeder 1 are sequentially conveyed onto the glass surface of the document table glass 2 one by one. When the original is conveyed on the glass surface of the original table glass 2, the lamp unit 3 of the light source unit 4 is turned on, and the original is irradiated while the light source unit 4 moves in the direction of the arrow in the drawing. Reflected light from the document passes through the lens 8 via the mirrors 5, 6, and 7, and then is input to the image sensor unit 9. The image signal input to the image sensor unit 9 is temporarily stored in the control unit 47, read out again, and then input to the scanner unit 10 as an optical scanning device. The latent image formed on the photoconductor 11 as the image carrier by the irradiation light generated by the scanner unit 10 is monitored by the potential sensor 30 to determine whether the potential on the photoconductor 11 is a desired value, and then Development is performed by the developing device 13. The transfer material is conveyed from the transfer material stacking section 14 or 15 in synchronization with the latent image, and the developed toner image is transferred onto the transfer material in the transfer section 16. The transferred toner image is fixed on the transfer material by the fixing unit 17 and then discharged from the paper discharge unit 18 to the outside of the apparatus. The surface of the photoconductor 11 after the transfer is cleaned by a cleaner 25, and the surface of the photoconductor 11 cleaned by the cleaner 25 is neutralized by an auxiliary charger 26 so that the primary charger 28 can obtain good charge. . Then, the residual charge on the photoconductor 11 is erased by the pre-exposure lamp 27, the surface of the photoconductor 11 is charged by the primary charger 28, and a plurality of images are formed by repeating this process.

<Schematic configuration of scanner unit and control unit>
FIG. 2 is a schematic configuration diagram of the scanner unit 10 and the control unit 47 as an optical scanning device. First, in FIG. 2, a scanner unit 10 as an optical scanning apparatus schematically includes a laser driving device 31 having a laser light source 43 that is a semiconductor laser, an aperture 32, a rotary polygon mirror 33, an f-θ lens 34, and a collimator lens 35. A BD sensor 36 that is a light detection sensor is provided. The image forming apparatus 100 also includes a control unit 47 that controls the photoconductor 11 and the scanner unit 10, and a display unit 400. The control unit 47 includes a CPU 101, an image data generation unit (image pattern generation unit) 200, an optical scanning device control unit 103, a document reading unit control unit 202, and a RAM 203.

  The rotary polygon mirror 33 has a plurality of reflecting surfaces (six reflecting surfaces in the present embodiment) and emits laser light emitted from the laser light source 43 to the photosensitive member 11 as an image carrier in the main scanning direction (axial direction of the photosensitive member). ) Is deflected and scanned.

  The laser light emitted from the laser light source 43 becomes substantially parallel light by the collimator lens 35 and the diaphragm 32 and is incident on the rotary polygon mirror 33 with a predetermined beam diameter. The rotating polygon mirror 33 having a plurality of reflecting surfaces rotates at an equal angular velocity in the direction of arrow A, and incident laser light is reflected as a deflected beam that continuously changes its angle with this rotation. . The laser beam that has become a deflected beam is focused by the f-θ lens 34. On the other hand, the f-θ lens 34 simultaneously corrects the distortion aberration so as to guarantee the scanning linearity in time, so that the laser beam is directed onto the photoconductor 11 as the image carrier in the direction of arrow B in the figure. Are scanned at a constant speed. The BD sensor 36 (light detection means) that detects the reflected light from the rotary polygon mirror 33 is disposed at a position for detecting the laser beam on the scanning start side for each reflection surface of the rotary polygon mirror 33. The detection signal S36 of the BD sensor 36 serving as the light detection means synchronizes the rotation of the rotary polygon mirror 33 and the start of writing of the image data from the image data generation unit (image pattern generation means) 200 to the photoconductor 11. Is used as a synchronization signal. The detection signal S36 is output to the image data generation unit (image pattern generation unit) 200 and the optical scanning device control unit 103 of the control unit 47.

  The document reading unit control unit 202 controls the document reading operation in the document reading unit R, and when the reading instruction signal S21 is output from the CPU 101 for detecting the variation in dirt according to the present invention, an image pattern is generated in the document reading unit R. Perform the reading operation. The CPU 101 detects the variation in dirt on the reflecting surface of the rotary polygon mirror 33 based on the density information of the image data detected by the document reading unit R stored in the RAM 203. The CPU 101 of the control unit 47 determines the light amount variation for each reflecting surface and instructs the display unit 400 to display a warning.

  Next, a case where normal image formation is performed will be described. In FIG. 2, the CPU 101 of the control unit 47 issues an image formation start signal S <b> 1 to the image data generation unit (image pattern generation unit) 200, and at the same time, the optical scanning device drive signal S <b> 3 is sent to the optical scanning device control unit 103. Be emitted. Then, the optical scanning device controller 103 issues a laser control signal S5 to the laser driving device 31 to control the light amount of the laser light source 43. Further, a scanner motor control signal is issued to a scanner motor (not shown) that drives the rotary polygon mirror 33 to stably rotate the rotary polygon mirror 33. The laser light emitted from the laser light source 43 is deflected and scanned by the rotary polygon mirror 33, so that the laser light passes through the BD sensor 36. When the laser light reaches the BD sensor 36, a BD signal S36 is emitted from the BD sensor 36 to the optical scanning device controller 103. The optical scanning device control unit 103 issues a scanner motor control signal to the scanner motor so as to stably rotate the scanner motor based on the period of detecting the BD signal S36. Further, when the laser beam is guided to the BD sensor 36, the BD signal S36 is also emitted to the image data generation unit 200. Based on the input timing of the BD signal S36, a predetermined image data signal S47 is emitted to the laser driving device 31, and the laser light source 43 is driven to form an image on the photosensitive member 11 as an image carrier.

  FIG. 3 is a detailed configuration diagram of the laser driving device 31 provided in the scanner unit 10 as the optical scanning device. In FIG. 3, a laser driving device 31 includes a comparator 40, a bias current source 41, a pulse current source 42, a laser light source 43, a current / voltage (I / V) converter 44, an amplifier 45, an APC circuit 46, and a modulation unit. 48 and a switch 49 are provided.

  When the laser light source 43 of the laser driving device 31 is driven based on the laser control signal S5 generated by the control unit 47 shown in FIG. The laser control signal S5 is a signal indicating a BD detection full lighting signal FULL, a sample / hold signal S / H, and a reference voltage VREF, which will be described later.

  A PD sensor for detecting a part of the laser beam is provided inside the laser light source 43 (described later), and APC control (meaning automatic light quantity control) of the laser diode is performed using a detection signal of the PD sensor. The laser light source 43 is a semiconductor laser and is a laser chip composed of a laser diode 43A and a PD sensor 43B. Further, a bias current source 41 of the laser diode 43A and a pulse current source 42 of the laser diode 43A are provided, and image data that is an image signal input from an image memory (not shown) or the like is subjected to pixel modulation in the modulation unit 48. A signal obtained by performing a logical sum operation on this signal and the BD detection full lighting signal FULL from the control unit 47 by the logic element 50 causes the switch 49 to be turned ON / OFF.

  When the switch 49 is ON, the laser diode 43A is controlled to emit light by the sum of the current from the bias current source 41 controlled every scan and the current from the pulse current source 42 variably controlled during one scan. That is, when the switch 49 is OFF, the laser diode 43A emits light only by the current from the bias current source 41.

  In the time zone before and after passing through the BD sensor 36, full lighting is performed to monitor the amount of light at the time of full lighting for BD detection. The output signal of the PD sensor 43B at the time of monitoring is converted into a voltage signal by the current / voltage (I / V) converter 44, amplified by the amplifier 45, and input to the APC circuit 46.

  FIG. 4 is a detailed configuration diagram of the APC circuit 46. First, in FIG. 4, the APC circuit 46 includes a resistor 37, an analog switch 38, a capacitor 39 and a comparator 40.

  The amplified PD sensor output VPD is sampled with the sample / hold signal S / H from the control unit 47 using the analog switch 38, and this voltage value (VSH) is set to 1 with a time constant determined by the resistor 37 and the capacitor 39. Hold during scan. At the same time, the difference signal VAPC is output by comparing the VSH with a preset reference voltage VREF by the comparator 40. As shown in FIG. 3, the difference signal VAPC controls the current of the bias current source 41. That is, the current of the bias current source 41 is controlled for each scan so that the target bias light emission value set as the reference voltage VREF is obtained, and the bias light amount of the laser diode 43A is APC controlled to a desired light amount.

<Dirt variation detection pattern>
In the present invention, an image pattern is output to detect the variation in dirt on the reflecting surface of the rotary polygon mirror 33. Here, the image pattern used when detecting the variation in dirt and the rotary polygon mirror 33 performed by the control unit 47 are detected. Next, the detection of variation in dirt will be described. FIG. 5 is a top view of the rotary polygon mirror 33 provided in the scanner unit 10 as the optical scanning device. FIG. 6 is a diagram showing an image pattern formed on a transfer material for detecting a variation in dirt. FIG. 7 is an enlarged view of a region A of “an image pattern formed only by scanning light on the [1] surface (first reflective surface)” (first image pattern) shown in FIG. FIG. 8 is an enlarged view of the region B of “an image pattern formed only by scanning light on the [2] plane (second reflective surface)” (second image pattern) shown in FIG. FIG. 11 is a timing chart when the image forming pattern of FIG. 6 is formed.

  As shown in FIG. 5, the rotary polygon mirror 33 of the present embodiment rotates at a constant angular velocity in the direction of arrow A, and includes six reflecting surfaces [1] to [6] in order in the direction of arrow A. Shall. The stain variation detection according to the present invention is performed by switching the operation of the image forming apparatus to the stain variation detection mode. In this stain variation detection mode, an image pattern as shown in FIG. 6 is formed on a sheet by following the same image formation procedure as in the normal image formation.

  FIG. 6 is a diagram showing an image pattern for detecting a variation in dirt. A reflection surface is selected from a plurality of reflection surfaces provided in the rotary polygon mirror 33, and only the selected reflection surface (only a specific surface) is used. Thus, the image pattern is formed and sequentially formed on all the reflection surfaces. That is, only when the photosensitive member is scanned with a specific reflecting surface, the image data signal S47 of FIG. 3 is output, the laser light source 43 is caused to emit light, and the photosensitive drum is scanned. At the timing of scanning the photosensitive drum on the other reflection surface, the image data signal S47 of FIG. 3 is not output, and therefore the laser light source 43 does not emit light, and the portion is not exposed.

  Here, the reflection surfaces are the [1] plane, [2] plane, [3] plane, [4] plane, [5] plane, and [6] plane, but the laser beam reflection first detected by the first BD sensor 36. The reflected surface was designated as [1] plane, and in the following order: [2] plane, [3] plane, [4] plane, [5] plane, and [6] plane. In order from the top of FIG. 6, “image pattern formed only with scanning light on [1] surface”, “image pattern formed only with scanning light on [2] surface”, “formed only with scanning light on [3] surface” "Image pattern formed by only the scanning light on the [4] plane". Further, “an image pattern formed only with the scanning light on the [5] plane” and “an image pattern formed only with the scanning light on the [6] plane”.

  That is, the “image pattern formed only with the scanning light on the [1] plane” in FIG. 6 is an image pattern formed using only the light beam deflected and scanned on the reflecting surface [1] shown in FIG. . This is because image formation is performed based on the BD signal S36 output by detecting the light beam deflected and scanned by the reflecting surface [1] by the BD sensor 36 during a period indicated as [1] in FIG. It is an image pattern formed at the timing of the image forming period [1] ′, [1] ″. FIG. 7 is an enlarged view of the area A surrounded by the dotted line in FIG. 6 is the image formed in the image formation period [1] ′ in FIG. 11A. The portion “scanned on the [1] plane (with exposure)” in FIG. Image formation is not performed on the reflection surfaces [2] to [6], and image formation is performed in an image formation period [1] '' formed with a light beam deflected and scanned on the reflection surface [1]. Thereafter, this process is repeated to form an “image pattern formed by only the scanning light on the [1] plane”.

  Further, “an image pattern formed only by scanning light on the [2] plane” in FIG. 6 is an image pattern formed using only a light beam deflected and scanned by the reflecting surface [2] shown in FIG. This is formed on the basis of the BD signal S36 output by detecting the light beam deflected and scanned by the reflecting surface [2] by the BD sensor 36 in a period described as [2] in FIG. 11B. This is an image pattern formed at the timing of the image formation period [2] ′, [2] ″. FIG. 8 is an enlarged view of the region B surrounded by the dotted line in FIG. 6 is the image formed in the image forming period [2] ′ in FIG. 11B. The portion “scanned on the [2] plane (with exposure)” in FIG. Image formation is not performed on the reflective surfaces [1] and [3] to [6], and image formation is performed during an image formation period [2] '' formed with a light beam deflected and scanned on the reflective surface [2]. . Thereafter, this process is repeated to form an “image pattern formed only with the scanning light on the [2] plane”.

  Thereafter, the image formation pattern as shown in FIG. 6 is completed by sequentially forming the image patterns at the timings of FIGS. 11C to 11F on the reflective surfaces [3] to [6].

  By the above operation, an image pattern is formed on the paper, and the image reading unit detects the density of the image pattern formed on the paper to compare the image density of each reflective surface, that is, the amount of reflected light per surface of the rotary polygon mirror. Can be easily compared. In addition, since the image pattern is drawn sequentially using only a specific reflecting surface, unlike the case of forming an image using a plurality of reflecting surfaces in order, the inclination (surface collapse amount) of the reflecting surface of the rotating polygon mirror is different for each reflecting surface. Therefore, it is possible to eliminate image defects such as density unevenness caused by different colors.

<Operation procedure>
FIG. 14 is a flowchart for explaining the stain variation detection mode in the image forming apparatus configured as described above. The process is executed by the control unit 47 and is controlled by the CPU 101. FIG. 15 is a message displayed on the display unit 400 according to an instruction from the CPU 101.

  When an operator such as a user or a service person instructs the display unit 400 to execute the stain variation detection mode, the CPU 101 instructs the image data generation unit 200 and the optical scanning device control unit 103 to output a stain variation detection pattern. (S101). When the stain variation detection pattern is discharged from the image forming apparatus, the operator places the recording medium on which the stain variation detection pattern is formed on the glass surface of the document table glass 2 of the document reading unit R. A message is displayed (S102). When the CPU 101 detects that the transfer material on which the stain variation detection pattern is formed is placed by the operator and an input of a confirmation key indicating that it is placed from the display unit 400 is detected (S103), the document reading unit A reading instruction signal S21 is output to the control unit 202 (S104).

  The document reading unit control unit 202 illuminates the document while turning on the lamp unit 3 of the light source unit 4 and moving the light source unit 4 based on the reading instruction signal S21. Reflected light from the document passes through the lens 8 via the mirrors 5, 6, and 7, and then is input to the image sensor unit 9. An image signal (density data that is a density value) input to the image sensor unit 9 is input to the RAM 203 of the control unit 47. As the input image signal (density data as density values), density data read from the image pattern formed on each of the reflection surfaces [1] to [6] is stored in the RAM 203 (S105). Thereafter, the control of FIG. 10 or FIG. 12 continues.

  The density data that is the read density value is stored in the RAM 203 as density values for each area divided into a plurality of blocks a to z in the main scanning direction B as shown in the image pattern of FIG. The density value is, for example, an area of main scanning direction: 10 mm × sub-scanning direction: 30 mm with each size of the blocks a to z, and the density of the area of main scanning direction 5 mm × sub-scanning direction 15 mm in the area. Is the read value.

  In the density data, when the image pattern sheet 207 is read by the image sensor unit 9, the density of the white background portion where no toner image is formed is 0, and the density when the toner image portion where the image pattern is formed is read is 255. As multi-value data of 8 bits.

  10 and 12 are flowcharts showing a method for comparing the density data stored in the RAM 203 by the CPU 101. It is determined whether the comparison result is equal to or greater than a predetermined value, and the degree of contamination is determined.

  First, FIG. 10 will be described. FIG. 10 shows a flowchart for comparing the density data obtained from the image patterns formed on each of the reflecting surfaces [1] to [6]. The CPU 101 starts comparison of density data obtained from images formed on the respective reflecting surfaces stored in the RAM 203 (S301). The average value of the density data in each of the blocks a to z is calculated for each reflection surface (S302). As a calculation method, the density data of each block corresponding to each reflection surface is added and averaged to calculate averaged data. FIG. 13 shows averaged data obtained by averaging the density data up to blocks az measured by the image sensor unit 9 and the density data up to blocks az.

  From the averaged data corresponding to each reflecting surface calculated in step S302, the maximum value corresponding to the reflecting surface with the maximum density data and the minimum value corresponding to the reflecting surface with the minimum density data are extracted from the averaged data. (S303). Next, it is determined whether or not the difference between the maximum value and the minimum value is less than 5% (S304). If it is less than 5%, the density comparison of each surface is completed (S308). For example, if the value is 5% or more, it is determined whether the difference between the maximum value and the minimum value is, for example, a range of 5 to 10% of the above-described range of 5% or more (S305). Here, the range of 5 to 10% is a start value for determining that 5% starts to be stained, and 10% is a value about the middle of γ, which is a value just before the occurrence of an abnormal image such as image shake. Set. If it is in the range of 5 to 10% (Y), a warning 1 display such as “slight dirt” (contents of warning display: FIG. 14A) is given and notified (S306), and the process ends. By cleaning at this stage, the service person can also prevent progressing to moderate dirt.

  If the stain progresses and the value is larger than 10%, it is determined whether or not the difference between the maximum value and the minimum value is, for example, in the range of 11 to 15% of the above-described range of 10% (S307). Here, the range of 11 to 15% is set to 15% so that the image can be detected at about 15% if an abnormal image such as image shaking is obtained at 20%. In the range of 11 to 15% (Y), warning 2 display such as “medium dirt” (content of warning display: FIG. 14B) is displayed on the display unit 400 and notified. However, since warning 1 and warning 2 are minor / moderate dirt warnings, they are displayed on the serviceman mode screen (screens that can only be viewed by a serviceman such as the service mode in the display unit 400). It may be possible to check at the time of regular maintenance. Further, by cleaning at this stage, the service person can prevent further progress of dirt.

  Next, when the contamination progresses and becomes greater than 15% (a predetermined value or more) (N), a warning 3 display such as “service man call” (contents of warning display: FIG. 14C) is notified ( S309). At this stage, an abnormal image such as image shaking occurs, so the operation of the image forming apparatus is stopped.

  As a result, it is possible to inform the operator of the progress of the stain step by step in accordance with the difference between the maximum value and the minimum value of the density in units of the reflective surface. For this reason, the service person can be urged to periodically clean, and the operation stop state of the image forming apparatus due to the occurrence of the service person call can be reduced.

  Next, FIG. 12 will be described. FIG. 12 shows a flowchart for comparing the density data of the respective blocks in the same plane of the reflecting surfaces [1] to [6] of the rotary polygon mirror.

  The CPU 101 starts comparison of density data of each block obtained from an image formed on each reflection surface stored in the RAM 203 (S401).

  For each block a to z, the average value of the density data on each reflecting surface is calculated (S402). As a calculation method, the density data of each reflecting surface corresponding to each of the blocks a to z is added and averaged to calculate averaged data.

  From the averaged data corresponding to each block a to z calculated in step S402, the maximum value corresponding to the block having the maximum density data and the minimum value corresponding to the block having the minimum density data are extracted from the averaged data. (S403). Next, it is determined whether or not the difference between the maximum value and the minimum value is 5% smaller (S404). If it is smaller than 5%, the density comparison of each block is completed. For example, if the value is 5% or more, it is determined whether the difference between the maximum value and the minimum value is, for example, a range of 5 to 10% of the range of 5% or more (S405). Here, the range of 5 to 10% is a start value for determining that 5% starts to be stained, and 10% is a value about the middle of γ, which is a value just before the occurrence of an abnormal image such as image shake. Set. If it is in the range of 5 to 10% (Y), a warning 1 display (contents to display the warning) such as “slight dirt” is given and notified (S406), and the process ends. By cleaning at this stage, the service person can also prevent progressing to moderate dirt.

  If the contamination progresses and the value is greater than 10%, it is determined whether or not the difference between the maximum value and the minimum value is, for example, in the range of 11 to 15%, which is greater than 10% (S407). Here, the range of 11 to 15% is set to 15% so that the image can be detected at about 15% if an abnormal image such as image shaking is obtained at 20%. If it is in the range of 11 to 15% (Y), warning 2 display (contents to display warning) such as “medium dirt” is displayed on the display unit 400 and notified (S408). However, since warning 1 and warning 2 are minor / moderate dirt warnings, they are displayed on the serviceman mode screen (screens that can only be viewed by a serviceman such as the service mode in the display unit 400). It may be possible to check at the time of regular maintenance. Further, by cleaning at this stage, the service person can prevent further progress of dirt.

  Next, when the stain progresses and becomes greater than 15% (a predetermined value or more) (N), a warning 3 display (contents to be displayed) such as “service man call” is displayed and notified (S409). At this stage, an abnormal image such as image shaking occurs, so the operation of the image forming apparatus is stopped.

  As a result, it is possible to accurately determine the degree of dirt even when dirt is unevenly adhered to the reflecting surface by comparing the contents of warning with the density data for each block. In addition, since the progress of dirt can be communicated to the operator step by step, the serviceman can be urged to regularly clean, and the operation stop state of the image forming apparatus due to the occurrence of the serviceman call can be reduced.

  According to the stain determination flowchart as described above, the service person can know in advance at the time of maintenance that the stain has started, and can appropriately grasp the progress of the stain. In the present invention, the serviceman is notified, but it is not necessary that only the serviceman can confirm. You may make it contact a service person by displaying so that a user may know that it started dirty.

  Accordingly, it is possible to prevent a situation where the operation of the image forming apparatus such as a service man call must be stopped by cleaning the reflecting surface of the rotary polygon mirror at an appropriate timing. In addition, it is possible to prevent an emergency dispatch of service personnel, and it is possible to prevent unnecessary cost increases. In addition, since it is known in advance that there is a high possibility that an error due to the dirt on the reflection surface of the scanner unit has occurred when dispatched by a service man call, it is possible to act quickly and the serviceability is greatly improved.

  In the above embodiment, the image pattern formed on each reflection surface of the rotary polygon mirror on the paper is output and compared in the entire main scanning direction. And the density may be compared at a main scanning end position where dirt is relatively difficult to adhere. In this case, since the total area of the image pattern can be suppressed, there is an effect that it is possible to suppress the amount of toner necessary for pattern formation.

  In addition, the image pattern is output to the paper, the density data is acquired by the reading device, and the density data is compared. However, the image pattern is not output to the paper, and the image forming apparatus using the intermediate transfer belt is formed on the intermediate transfer belt. The density data read by the photo sensor may be compared. In this case, it is not necessary to force the operator to perform a density measurement operation, and thus there is an effect that a user-friendly dirt discrimination function can be provided.

  Further, even if the density data of the image pattern is not read by the image forming apparatus, the image pattern can be output and the serviceman and the user can visually compare and determine the dirt and replacement time of the rotary polygon mirror. is there.

  In the above description, the criteria for determining the degree of contamination is 5% to 10%, 11% to 15%, and so on. However, this is an example of “when there is almost no difference”, “when there is a medium difference”, and “when there is a large difference”, and it is set appropriately according to the characteristics of the device at the time of implementation. It is what is done.

1 is a schematic cross-sectional view of an entire image forming apparatus as an embodiment of the present invention. It is a schematic block diagram of the scanner unit and control unit as an embodiment of the present invention. It is a detailed block diagram of the laser drive device as embodiment of this invention. It is a detailed block diagram of the APC circuit as an embodiment of the present invention. FIG. 3 is a top view of a rotary polygon mirror included in the scanner unit. It is a figure which shows an image pattern. It is an enlarged view of the area | region A in the image pattern of FIG. It is an enlarged view of the area | region B in the image pattern of FIG. It is a figure which divides | segments into a block in the main scanning direction B at the time of reading the image pattern of FIG. It is a figure showing the flow of the density comparison of an image pattern. It is a figure showing the image formation timing at the time of forming the image pattern in embodiment of this invention. It is a figure showing the flow of the density comparison of the main scanning block of an image pattern. It is a figure showing the read image density data. It is a flowchart explaining the dispersion | variation detection mode of dirt. It is a figure which shows the message displayed on a display part. It is a figure showing the stain | pollution | contamination of the reflective surface of a rotary polygon mirror.

Claims (6)

In an image forming apparatus that reflects a laser beam on a rotating polygon mirror having a reflecting surface to form an image on an image carrier, and transfers the formed image to a transfer material.
A first image pattern formed by reflecting on the first reflecting surface of the rotary polygon mirror and a second image pattern formed by reflecting on the second reflecting surface without using the first reflecting surface. Image pattern generating means to be formed;
Reading means for reading the first image pattern and the second image pattern formed by the image pattern generation means;
An image forming apparatus comprising: a detecting unit configured to detect a variation in dirt on a reflecting surface of the rotary polygon mirror based on a result of reading the first image pattern and the second image pattern by the reading unit.   The detecting means detects a variation in dirt on the reflecting surface of the rotary polygon mirror based on a comparison between the density value of the first image pattern and the density value of the second image pattern read by the reading means. The image forming apparatus according to claim 1.   The reading unit divides the axial direction of the image carrier into a plurality of blocks, reads the density value of the formed image pattern by the plurality of blocks, and the detection unit reads the blocks read by the reading unit. The image forming apparatus according to claim 2, wherein a variation in dirt on the reflecting surface of the rotary polygon mirror is detected based on each density value.   The detecting means detects the reflection surface of the rotary polygon mirror when the difference between the density value of the first image pattern read by the reading means and the density value of the second image pattern is a predetermined value or more. The optical scanning device according to claim 2, wherein it is determined that there is a variation in dirt.   5. The detection unit according to claim 4, wherein the detection unit detects a variation in dirt on a reflection surface of the rotary polygon mirror based on a difference between a maximum value and a minimum value of density values read by the reading unit. Optical scanning device.   Content of displaying a warning according to the difference between the maximum value and the minimum value, having a notification unit that displays a warning that the detection unit has detected a variation in dirt on the reflecting surface of the rotary polygon mirror An image forming apparatus comprising the optical scanning device according to claim 5.

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