JP2005316118A - Color image forming apparatus provided with position-shifting correction mode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color image forming apparatus capable of automatically performing such a color shift correction mode and confirming the autonomy of the apparatus related to color shift correction without directions of performance of the color shift correction mode according to a worker or a field engineer after assembly in a plant or after overhaul in the installed and used site. <P>SOLUTION: In the color image forming apparatus provided with color shift correction mode, a color image is formed on a recording sheet by superposing respective color toner images, the amount of color shift upon the superposition of the respective color toner images is detected and, in accordance with the detection value, the correction of formation positions of the respective color toner images is performed. The color image forming apparatus is further provided with a means for storing the completion of the color shift correction mode when the color shift correction mode is completed and a correction mode performance section which refers to the retained result of the storage means after the starting of an apparatus body and, when it is determined that the color shift correction mode is not completed once in the past, performs the initial color shift correction mode. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as an electrophotographic copying machine or a laser beam printer, and in particular, includes a plurality of image forming engines for forming a monochromatic toner image, and the toner images formed by the respective image forming engines are transferred to an intermediate transfer belt or a recording sheet. The present invention relates to a color image forming apparatus of a type that forms a color image by superimposing on a moving body such as a conveyor belt.

Japanese Patent No. 2921856 JP-A-9-080847 JP-A-8-305108 JP-A-10-307448

  In a so-called tandem color image forming apparatus, an image forming engine for forming a single color toner image according to image information is provided for each color of yellow, cyan, magenta, and black, and an intermediate transfer that passes through these image forming engines. The single color toner image is sequentially transferred to a belt or a recording sheet, and finally a full color image is obtained by forming a composite toner image in which the four color toner images overlap. Here, each image forming engine includes a photosensitive drum, a charger that uniformly charges the photosensitive drum, a raster scanning device that exposes the surface of the photosensitive drum with a light beam modulated according to image information, A developing unit for developing the electrostatic latent image formed by the exposure with toner and a drum cleaner for cleaning the surface of the photosensitive drum after the toner image is transferred are included.

  Thus, in a color image forming apparatus of a type having a plurality of image forming engines, the rotational accuracy of the photosensitive drum in each image forming engine, the mounting position error of the raster scanning device, and the elongation of each machine element component accompanying the temperature change. The relative positional relationship of each monochromatic toner image on the moving body fluctuates due to speed fluctuations and meandering of the moving body such as an intermediate transfer belt or a sheet conveying belt that is shrunk and finally the four color toner images are superimposed. Therefore, color misregistration (color registration error) is likely to occur. The user's request for this color shift is becoming stricter year by year, and it is required to suppress the color shift amount to 100 to 200 μm or less.

  For this reason, this type of color image forming apparatus is provided with a position detection device for grasping the relative positional deviation amount of each single color toner image on the moving body and the speed fluctuation of the moving body. Deviation correction is performed (Japanese Patent No. 2765627, Japanese Patent Laid-Open No. 2001-22227, etc.). Specifically, toner marks for position measurement (hereinafter referred to as “control marks”) are sequentially formed on the surface of the moving body from each image forming engine at a specific timing, and these control marks are formed on a CCD image sensor or a photo. By detecting using a position detection device including a diode or the like, it is possible to grasp the amount of positional deviation between toner images formed by each image forming engine. Then, by correcting the electrostatic latent image writing timing and writing position in each image forming engine based on the grasped result, it is possible to accurately superimpose single color toner images on the moving body and suppress the occurrence of color misregistration. It is possible.

  The color misregistration correction procedure (hereinafter referred to as “color misregistration correction mode”) performed by forming the control mark in each image forming engine in this way is a normal image forming operation, that is, image formation according to a user instruction. The interval between the operations or the image forming operation itself must be interrupted. If the frequency of the color misregistration correction mode is too high, the productivity of the recorded image decreases. Further, since the control mark is formed using toner in each image forming engine, the toner is consumed regardless of the formation of the recorded image. The running cost of the forming apparatus itself increases.

  Therefore, it has been proposed that the color misregistration correction mode should be performed at a timing at which color misregistration between toner images can be more effectively corrected. For example, in the color image forming apparatus disclosed in Japanese Patent No. 2921856, means for detecting the temperature inside the apparatus is provided, and the color misregistration correction mode is executed every time the detected temperature rises by a predetermined temperature. Further, in the color image forming apparatus disclosed in Japanese Patent Laid-Open No. 9-080847, it is detected whether or not the image forming engine is detached from the apparatus housing, and when it is determined that the image forming engine is detached, the color misregistration correction mode is selected. It is carried out. Further, a color image forming apparatus has been proposed in which a past execution history is added to these execution determinations to determine whether or not to execute the color misregistration correction mode, and the unnecessary color misregistration correction mode is suspended (special feature). (Kaihei 8-305108). Furthermore, in addition to automatic execution determination by a temperature sensor or the like, a color image forming apparatus is also proposed in which a user can directly instruct execution of a color misregistration correction mode from an operation panel.

  By the way, even after the device is assembled at the factory, before or after shipment, after the field engineer disassembles and repairs the device at the installation and use location, the device is It is necessary to verify whether or not the color shift of the recorded image can be resolved autonomously. If it cannot be resolved, further adjustment is necessary. Therefore, the color misregistration correction mode must be executed immediately after the assembly of the device in the factory or immediately after the repair adjustment work by the field engineer.

  However, as described above, in the conventional color image forming apparatus, the color misregistration correction mode is not executed unless specific conditions are met from the viewpoint of improving work efficiency by the user. For this reason, after assembly in the factory, the engineer must instruct the device that has completed assembly to input an execution command for the color misregistration correction mode, and the device for inputting the command and the command for inputting the command. Work time was required, leading to a decrease in productivity.

  Similar problems also occur when a field engineer performs disassembly and adjustment at the place where the apparatus is installed and used. In particular, if the field engineer has forgotten to forcibly execute the color misregistration correction mode after performing separation adjustment, there is a problem that the color misregistration cannot be resolved when the user uses it later. Will occur.

  The present invention has been made in view of such problems, and the purpose of the present invention is to provide an engineer or a field engineer to execute the color misregistration correction mode after assembly in a factory or after disassembly and repair at an installation and use location. Accordingly, it is an object of the present invention to provide a color image forming apparatus capable of automatically executing such a color misregistration correction mode and confirming the autonomy of the apparatus regarding color misregistration correction.

  In order to achieve the above object, a color image forming apparatus of the present invention includes a plurality of color image forming engines that form toner images according to image information, and superimposes the color toner images formed by these image forming engines. While forming a color image on the recording sheet or the intermediate transfer belt, the color misregistration amount when each color toner image is superimposed is detected, and the toner image formation position in each image forming engine is corrected based on the detected value. On the premise of a color image forming apparatus having a color misregistration correction mode for performing the color misregistration correction mode, means for storing it when the color misregistration correction mode is completed, and referring to the holding result of the storage means after the apparatus main body is activated, And a correction mode execution unit that executes the initial color misregistration correction mode when it is determined that the color misregistration correction mode has never been completed in the past.

  According to the present invention, when the apparatus main body is turned on and started, the correction mode execution unit first refers to the storage result stored in the storage means. Of course, if the apparatus is activated, the color misregistration correction mode has never been completed, and if the storage means is configured as a flag, no flag regarding completion of the color misregistration correction mode is set. . As a result, the correction mode execution unit immediately executes the initial color misregistration correction mode, and the correction data of the toner image formation position by each image forming engine is created.

  In addition, even when a field engineer disassembles and repairs the device at the place where the device is used and clears the storage unit storage result, when the device main body is turned on after the disassembly repair is completed, the color misregistration correction mode is completed. No correction flag is set, the correction mode execution unit immediately executes the initial color misregistration correction mode, and correction data for the toner image formation position by each image forming engine is created.

  That is, according to the present invention, after assembly at the factory or after disassembly and repair at the installation and use location, as long as the apparatus body is turned on, the execution of the color misregistration correction mode is not instructed by an engineer or a field engineer. Such a color misregistration correction mode is automatically executed, and it becomes possible to confirm the autonomy of the apparatus regarding the color misregistration correction.

Hereinafter, a color image forming apparatus of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows an example of a color laser beam printer to which the present invention is applied. This laser beam printer includes four image forming engines 10Y, 10M, 10C, and 10Bk that form toner images for each of yellow, magenta, cyan, and black, and the toner images are primarily transferred from the image forming engines. An intermediate transfer belt 20 is provided, and the toner image multiple-transferred to the intermediate transfer belt 20 is secondarily transferred to the recording sheet P to form a full color image.

  The intermediate transfer belt 20 is formed in an endless shape and is wound around three belt transporting rolls 21 to 23 including a driving roll 21, and each color image forming engine 10Y, 10M, It is configured to receive primary transfer of a toner image formed with 10C and 10Bk. Further, a secondary transfer roll 30 is disposed at a position facing the belt conveying roll 23 with the intermediate transfer belt 20 interposed therebetween, and the recording sheet P is interposed between the transfer roll 30 and the intermediate transfer belt 20 that are pressed against each other. The toner image is inserted through the intermediate transfer belt 20 to receive secondary transfer of the toner image. That is, the belt conveyance roll 23 functions as a backup roll of the transfer roll 30, and the transfer roll 30 and the belt conveyance roll 23 constitute a secondary transfer unit.

  The intermediate transfer belt 20 is stretched between three belt conveyance rolls 21 to 23, and a substantially horizontal image receiving span is formed between the belt conveyance rolls 21 and 22, while the two are directly below the image receiving span. A third belt conveyance roll 23 facing the next transfer roll 30 is disposed and stretched in an inverted triangular shape as a whole.

  The four image forming engines 10Y, 10M, 10C, and 10Bk described above are arranged in parallel on the image receiving span of the intermediate transfer belt 20, and a toner image formed according to image information of each color is intermediate transferred. Primary transfer is performed on the belt 20. These four image forming engines are arranged in the order of yellow 10Y, magenta 10M, cyan 10C, and black 10Bk along the rotation direction of the intermediate transfer belt 20, and the black image forming that is most frequently used is arranged. The image engine 10Bk is disposed closest to the secondary transfer portion. Each of the image forming engines 10Y, 10M, 10C, and 10Bk includes a raster scanning unit (ROS) 12 that exposes the photosensitive drums 11 included in the image forming engines according to image information. The laser beam Bm modulated according to the image information exposes the photosensitive drums 11 of the image forming engines 10Y, 10M, 10C, and 10Bk.

  Each of the image forming engines 10Y, 10M, 10C, and 10Bk is sensitized by exposure of the photosensitive drum 11, the charger 13 that charges the photosensitive drum 11 to a uniform background portion potential, and the laser beam Bm. A developing device 14 that develops the electrostatic latent image formed on the photosensitive drum 11 to form a toner image, and residual toner and paper dust from the surface of the photosensitive drum 11 after the toner image is transferred to the intermediate transfer belt 20. A drum cleaner 15 that removes toner and a pre-cleaning static eliminator 16 that neutralizes residual toner prior to cleaning by the drum cleaner, and forms a toner image corresponding to image information of each color on the photosensitive drum 11. Configured to get.

  Primary transfer rolls 17Y, 17M, 17C, and 17Bk are disposed at positions facing the photoconductive drums 11 of the image forming engines 10Y, 10M, 10C, and 10Bk so as to sandwich the intermediate transfer belt 20 therebetween. By applying a predetermined transfer bias voltage to 17Y, 17M, 17C, and 17Bk, an electric field is formed between the photoconductive drum 11 and the transfer rolls 17Y, 17M, 17C, and 17Bk. The charged toner image is transferred to the intermediate transfer belt 20 by Coulomb force.

  Therefore, in forming a full color image by the color laser beam printer, first, the raster scanning unit 12 applies the photosensitive drums 11 of the image forming engines 10Y, 10M, 10C, and 10Bk at a predetermined timing according to the image information of each color. After the exposure to form an electrostatic latent image, the electrostatic latent image is developed by the developing unit 14, so that the image forming engines 10 </ b> Y, 10 </ b> M, 10 </ b> C, and 10 </ b> Bk on the photosensitive drums 11 correspond to image information. A toner image is formed. The toner images formed by the image forming engines 10Y, 10M, 10C, and 10Bk are sequentially transferred to the rotating intermediate transfer belt 20, and a multiple toner image in which the respective color toner images are overlapped on the intermediate transfer belt 20. It is formed.

  On the other hand, after the recording sheet P is pulled out from the sheet cassette 40 one by one by the sheet feeding roll 41, the intermediate transfer belt 20 and the secondary transfer roll 30 pass through a predetermined sheet feeding path 46 indicated by a broken line in the drawing. Is fed to the secondary transfer portion in contact. A registration roll 42 is provided on the front side of the secondary transfer portion, and the recording sheet P is primary-transferred onto the intermediate transfer belt 20 by controlling the entry timing with respect to the secondary transfer portion by the registration roll 42. Registration with the toner image is performed.

  The backup roll 23 facing the secondary transfer roll 30 with the intermediate transfer belt 20 interposed therebetween is formed by covering the surface of the insulating roll with a semiconductive sheet, and a predetermined transfer bias voltage is applied to the surface. The conductive contact roll 50 is in contact. Accordingly, when a transfer bias voltage having the same polarity as that of the toner image is applied to the contact roll 50 and a charge is applied to the surface of the backup roll 23, the transfer roll 30 and the intermediate transfer located on the back side of the recording sheet P are transferred. A transfer electric field is formed between the backup roll 23 located on the back side of the belt 20, and the toner image held on the intermediate transfer belt 20 is electrostatically transferred to the recording sheet P.

  The recording sheet P on which the toner image has been secondarily transferred is peeled off from the intermediate transfer belt 20 and then conveyed to the fixing device 44 by a series of two sheet conveying belts 43 arranged in series. The recording sheet P is fixed on the toner image by the fixing device 44 and then discharged to the paper discharge tray 45, whereby the formation of the full color image on the recording sheet P is completed. Further, in this printer, an inverter passage 47 for inverting the front and back of the recording sheet P between the fixing device 44 and the discharge tray 45 in order to enable so-called face-down discharge with the image surface of the recording sheet P facing downward. Is formed. Further, the inverter passage 47 is connected to the above-described sheet feeding passage 46 by a sheet re-transmission passage 48. By feeding the recording sheet P that is reversed upside down in the inverter passage 47 to the secondary transfer portion again, the recording sheet P It is possible to form recorded images on both the front and back sides.

  On the other hand, the transfer residual toner is removed from the surface of the intermediate transfer belt 20 after the secondary transfer of the toner image is completed by the belt cleaner 24. The belt cleaner 24 has a cleaning blade that scrapes off toner, paper dust, and the like from the surface of the intermediate transfer belt 20, and the cleaning blade is provided at a position facing the belt conveying roll 21. As a result, the surface of the intermediate transfer belt 20 after the secondary transfer of the toner image is cleaned and used for the formation of the next toner image.

  In such a color printer, if the belt 20 is displaced in the width direction perpendicular to the rotation direction or the rotation speed fluctuates during the rotation of the intermediate transfer belt 20, the image forming engines 10Y, 10M, 10C. The toner image primarily transferred from 10 Bk cannot be accurately superimposed on the intermediate transfer belt 20, and color misregistration occurs in the full-color recording image finally formed on the recording sheet P, so that the image quality is improved. There is a problem that it drops significantly. Further, when there is a displacement in the mounting position of the raster scanning unit 12 included in each of the image forming engines 10Y, 10M, 10C, and 10Bk, or the position is set at the mounting position along the circumferential direction of the intermediate transfer belt of each image forming engine. Even when there is a deviation, the toner images primarily transferred from the image forming engines 10Y, 10M, 10C, and 10Bk to the intermediate transfer belt 20 cannot be accurately superimposed on the intermediate transfer belt 20. Furthermore, even if the mechanical parts expand and contract slightly due to changes in environmental factors such as temperature and humidity, color shift may occur in the final color image.

  For this reason, in the color laser beam printer of this embodiment, a color misregistration correction mode for forming a control mark on the surface of the intermediate transfer belt 20 from each of the image forming engines 10Y, 10M, 10C, and 10Bk is performed. The mark is detected by using the control information detecting means 1, and the relative displacement amount of each color toner image on the intermediate transfer belt 20 is extracted using the detection result, and each color at the time of actual color image formation is extracted. The toner image forming position is corrected. The timing for executing this color misregistration correction mode will be described later.

  FIG. 2 is a block diagram showing a control system for correcting the formation position of the toner image using the control mark. In forming such a control mark, first, the correction mode execution unit 4 determines whether or not it is necessary to execute the color misregistration correction mode according to a predetermined condition. When it is determined that execution is necessary, the correction mode execution unit 4 instructs the mark reference signal generation unit 2 to output image information corresponding to the control mark, and generates a mark reference signal. The unit 2 outputs image information corresponding to the control mark to the raster scanning unit 12. As a result, an electrostatic latent image corresponding to the control mark is formed on the photosensitive drum 11, which is developed with toner by the developing device 14 and then transferred to the intermediate transfer belt 20 in the same manner as a normal toner image. As a result, the control mark M is formed on the intermediate transfer belt 20. As described above, the control mark M is formed on the intermediate transfer belt 20 through the same image formation process as that of a normal toner image. Therefore, the problems that the image forming engines 10Y, 10M, 10C, and 10Bk have, The amount of positional deviation of the toner images formed by the image forming engines 10Y, 10M, 10C, and 10Bk is reflected in a real manner.

  The control mark M formed on the intermediate transfer belt 20 in this way is read by the control information detecting means 1 provided on the downstream side of the black image forming engine 10Bk. The control information detection unit 1 optically reads the control mark M and outputs a signal indicating the position of the center of gravity and the density to the correction control unit 3. Based on the output signal of the control information detection means 1, the correction control unit 3 relates to the time interval through which the control marks M formed by the image forming engines 10Y, 10M, 10C, and 10Bk pass and the width direction of the intermediate transfer belt 20. The position is measured, and the amount of positional deviation of the toner images formed by the image forming engines 10Y, 10M, 10C, and 10Bk is calculated. Then, the correction control unit 3 generates correction data from the calculated amount of misregistration, and uses the correction data for the raster scanning units 12 of the image forming engines 10Y, 10M, 10C, and 10Bk at the time of actual recording image formation. It is configured to provide feedback.

  FIG. 3 shows an example of the control mark M formed on the intermediate transfer belt 20 by each image forming engine. In this example, a substantially V-shaped control mark M is formed from each of the image forming engines 10Y, 10M, 10C, and 10Bk. This control mark M has two sides (M1, M2) that obliquely intersect both the moving direction (sub-scanning direction) of the intermediate transfer belt 20 and the direction orthogonal to it (main scanning direction). Yes. Further, the halftone dot coverage of the image information sent from the mark reference signal generator 2 is Cin = 100%. The control marks M are transferred from the image forming engines 10Y, 10M, 10C, and 10Bk to the intermediate transfer belt 20 at a predetermined timing. As shown in FIG. 3, cyan control marks M are used on the intermediate transfer belt 20. They are arranged so as to sandwich control marks M of other colors. This is because when the relative misregistration amount of the other control marks M is detected with reference to the cyan control mark M, the comparison is facilitated and the detection accuracy of the misregistration amount is increased.

  FIG. 4 shows the details of the control information detecting means 1. The control information detection means 1 receives the LED element 50 as an illuminating means for illuminating the surface of the intermediate transfer belt 20 and the reflected light from the control mark M on the intermediate transfer belt 20 illuminated by the LED element 50. A light receiving element 51 that outputs a current value having an intensity corresponding to the amount of received light, and an amplifier (AMP) 52 that converts / amplifies the current value output from the light receiving element 51 into a voltage value having an intensity corresponding to the magnitude thereof. A peak detection circuit 53 for outputting a detection signal of the control mark M corresponding to the maximum value of the voltage value (hereinafter referred to as “sensor output signal”) output from the amplifier, and the sensor output from the amplifier 52 A sample and hold circuit 54 that takes in the output signal and holds the sensor output signal when the peak detection signal is output from the peak detection circuit 53. To have. Here, a single photoelectric conversion element such as a photodiode or a phototransistor is used as the light receiving element, and these light receiving elements output a current having an intensity corresponding to the amount of reflected light received.

  The LED element 50 and the light receiving element 51 are accommodated in the casing 5, and the irradiation light of the LED element 50 passes through the exit slit 5 a provided in the casing 5, and passes through the surface of the intermediate transfer belt (moving body) 20 by 45 °. It is configured to illuminate at an angle of. The casing 5 is also formed with an incident slit 5b for allowing the reflected light of the control mark M on the intermediate transfer belt 20 to pass toward the light receiving element 51. The incident slit 5b allows the incident slit 5b to pass from the surface of the intermediate transfer belt. The reflected light guided into the casing 5 at an angle of 90 ° forms an image on the light receiving element 51 through the lens 55. This lens has a diameter of 3 mm and a focal length of 6 mm. The distance from the surface of the intermediate transfer belt to the lens is 12 mm, the distance from the lens to the light receiving element is also 12 mm, and a conjugate optical system with a magnification of 1 is constructed. ing. Further, a mask 56 for limiting the passage area of the reflected light is provided on the front surface of the light receiving element 51, and a circular window having a diameter of 1 mm is opened on the mask 56 as a window for transmitting the reflected light. Yes. The mask 56 is black to prevent stray light. By using the exit slit 5 a and the entrance slit 5 b of the casing 5, the lens 55, and the mask 56, a field area of the light receiving element 51 on the intermediate transfer belt 20 is formed.

  FIG. 5 shows the positional relationship between the measurement mark M formed on the intermediate transfer belt 20 and the visual field region R of the light receiving element 3a with time, and the lower graph (a) shows the light receiving element. The output signal of the sensor means 3 according to the position of the visual field region R of 3a, in other words, the output signal waveform of the light receiving element 3a converted / amplified by the amplifier 3b is shown. The lowermost graph (b) shows the measurement mark detection signal output from the peak detection means 4 as time elapses. Here, the visual field region R is formed in a circular shape, while the measurement mark is formed with a thickness t slightly smaller than the diameter d of the visual field region R.

  The measurement mark M primarily transferred onto the intermediate transfer belt 20 by the image forming engines 10Y, 10M, 10C, and 10Bk passes through the front surface of the position detection device 1 as the intermediate transfer belt 20 rotates, and receives a light receiving element. It crosses the viewing area R of 3a. When the measurement mark M moves together with the intermediate transfer belt 20 and the field area of the light receiving element reaches the point A on the intermediate transfer belt shown in FIG. 5, the measurement mark M enters the field area R. As a result, the output signal of the sensor means 3 starts to change. When the measurement mark M further moves, the area of the measurement mark M included in the visual field region R, that is, the overlapping area of the visual field region R and the measurement mark M increases, so that the output signal of the sensor means 3 gradually increases. The output signal of the sensor means 3 becomes maximum at the point B where the visual field region R is substantially covered with the measurement mark M.

  As described above, since the thickness t of the measurement mark M is slightly smaller than the diameter d of the visual field region R of the light receiving element 3a, when the measurement mark M passes the B point, this time the visual field region. Since the area of the measurement mark M included in R, that is, the overlapping area of the visual field region R and the measurement mark M decreases, the output signal of the sensor means 3 gradually decreases, and the measurement mark M becomes a light receiving element. The output signal of the sensor means 3 becomes the minimum (point C) when it completely leaves the visual field region R of 3a.

  When an instantaneous maximum value is generated in the output signal waveform of the sensor means 3 as shown in FIG. 5A, the maximum value is the center position (center of gravity position) in the thickness direction of the side M1 of the measurement mark M. This occurs when the center position of the visual field region R of the light receiving element 3a is matched. Therefore, the peak detection means 4 detects the maximum value (peak) of the output signal of the sensor means 3, and outputs a pulse-like peak detection signal in accordance with this maximum value, as shown in FIG. 5B. With this configuration, the rising edge portion of the peak detection signal indicates the center position (center of gravity position) of the measurement mark side M1, and the position of the measurement mark M can be accurately detected. For the peak detection means 4, the peak level detection technique used in the signal processing of the electric circuit can be applied as it is.

  If the center position (center of gravity position) of the measurement mark M can be accurately detected in this way, the center position (center of gravity position) of the measurement mark M sequentially formed on the intermediate transfer belt 20 at a predetermined interval. ) And measuring the time interval, it is possible to accurately grasp the moving speed of the intermediate transfer belt 20 and its fluctuation.

  In particular, the measurement mark M shown in FIGS. 3 and 5 is formed in a V shape having two sides M1 and M2 that are inclined at approximately 45 degrees in different directions with respect to the moving direction of the intermediate transfer belt 20. Therefore, by detecting one of the measurement marks M with the position detection device 1 of the present embodiment, the speed fluctuation of the intermediate transfer belt 20 and the positional deviation amount in the width direction can be grasped at a time. It can be done. That is, the output signal of the sensor means 3 is once minimized when the visual field region R of the light receiving element 3a reaches the point C, but when the visual field region R passes the point D, the measurement mark M and the visual field region R again. Starts to overlap and starts rising again, and shows the maximum value at the point E where the center position of the measurement mark M in the thickness direction overlaps the center position of the visual field region R. As the overlap area between the measurement mark M and the visual field region R decreases, the output signal of the sensor means 3 also decreases, and the measurement mark M returns to the minimum output at the point F where the measurement mark M leaves the visual field region R.

  Therefore, when the V-shaped measurement mark M shown in FIG. 5 is detected by the position detection apparatus 1 of the present invention, as shown in FIG. A pair of pulsed peak detection signals are output from the peak detection means 4 corresponding to the points B and E where the center of gravity position overlaps the center position of the visual field region R, and the rising edge of these peak detection signals By measuring the time interval, it is possible to grasp the moving speed and speed fluctuation of the intermediate transfer belt 20.

  Further, by adding the previously determined movement speed of the intermediate transfer belt 20 to the time interval between the pair of peak detection signals, it is possible to detect the amount of positional deviation of the toner image in the width direction of the intermediate transfer belt 20. . That is, assuming that the moving speed of the intermediate transfer belt 20 is constant and the time interval of the peak detection signal is shorter than a predetermined value, the toner image on the intermediate transfer belt 20 is displaced downward from the paper surface of FIG. If it is longer than the predetermined value, it means that the toner image on the intermediate transfer belt 20 is displaced upward from the paper surface of FIG. Such misalignment of the toner image occurs when the intermediate transfer belt 20 itself moves in the width direction during rotation, and electrostatically with respect to the photosensitive drums 11 of the image forming engines 10Y, 10M, 10C, and 10Bk. This also occurs due to the positional deviation of the raster scanning unit 12 that writes the latent image.

  According to the position detection apparatus 1 of the present embodiment configured as described above, the light emission amount of the LED element 2 that illuminates the intermediate transfer belt 20 and the reflected light amounts of the measurement mark M and the intermediate transfer belt 20 are changed over time. Even if the intensity level of the output signal of the sensor means 3 changes, the appearance position of the maximum value of the output signal does not change, so by detecting the appearance point of this maximum value The center position (center of gravity position) of the measurement mark M can be accurately detected.

Next, the execution timing of the color misregistration correction mode will be described.
As described above, in the color misregistration correction mode, the control marks M are formed using the respective image forming engines 10Y, 10M, 10C, and 10Bk. Therefore, when the color misregistration correction mode is performed, normal printing is performed according to instructions from the user. Since the operation mark must be interrupted and the control mark M is formed using toner in each of the image forming engines 10Y, 10M, 10C, and 10Bk, if the color misregistration correction mode is executed too frequently, In addition to a decrease in print production capacity, there is a problem that running costs increase due to wasteful consumption of toner. For this reason, a condition for starting execution of the color misregistration correction mode is determined. Normally, when the user uses the color misregistration correction mode, the color misregistration correction mode is executed only when the condition is met. .

  Also, immediately after this color laser beam printer is assembled at the factory, or after a field engineer visits the place of installation and repair by the user, the printer itself becomes autonomous by performing the above-described color misregistration correction mode. In addition, it is necessary to check whether or not the color misregistration of the recorded image can be eliminated. If the color misregistration cannot be eliminated autonomously, an assembly failure or a repair failure is suspected. For this reason, it is necessary to forcibly execute the color misregistration correction mode even before maintenance such as disassembly and repair at the installation and use place before shipment in the factory.

  For this reason, this printer is provided with a correction mode counter 5 for counting the number of times that the color misregistration correction mode has been executed in the past, and the correction mode execution unit 4 first refers to the count value of the correction mode counter 5. If it is determined that the color misregistration correction mode should be executed immediately, and if it is determined that it is not necessary to execute it immediately, the color misregistration correction mode is checked by checking whether or not a predetermined condition is satisfied. Judgment is necessary. Here, the reason why the correction mode counter 5 counts the number of completed color misregistration correction modes, not just the number of executed color misregistration correction modes, is that the control mark M is formed and the control marks are connected to each other. This is because, when the amount of misalignment is detected, but the color misregistration correction mode is terminated without creating correction data, this is not counted. That is, although it is rare, even if the proper control mark M cannot be formed for some reason in each of the image forming engines 10Y, 10M, 10C, and 10Bk, and even if the proper control mark M can be formed, the intermediate transfer belt. In some cases, the control mark M cannot be read correctly by the control information detection means 1 and the correction control unit 3 does not create correction data. This is because the color misregistration correction mode ends and no color misregistration correction is performed.

  The count value of the correction mode counter 5 increases every time the color misregistration correction mode ends normally and accumulates as it is. However, when a field engineer removes the image forming engine 10Y, 10M, 10C, 10Bk or the intermediate transfer belt 20 from the main body of the apparatus and removes an important part for forming a recorded image, it is attached. At this time, the count value of the correction mode counter 5 is cleared.

FIG. 6 is a flowchart illustrating a processing procedure when the correction mode execution unit 4 determines whether or not to execute the color misregistration correction mode.
First, when the power of the printer apparatus is turned on, warm-up of the image forming engines 10Y, 10M, 10C, 10Bk and the fixing device 44 is started (ST10). With reference to the count value C of the correction mode counter 5, it is checked whether or not the count value is C = 0 (ST11). The correction mode counter 5 counts the number of times the color misregistration correction mode has been executed and completed in the past. If the count value is 1 or more, the color misregistration correction mode is normally performed at least once. This means that correction data for correcting the formation position of the toner image in each image forming engine has been created normally.

  When the count value C = 0 of the correction mode counter 5 is, for example, immediately after assembly by the factory and the image forming operation is not yet performed, or the field engineer has disassembled and repaired the printer as described above. This is the case. In this case, the correction mode execution unit 4 instructs the mark reference signal generation unit 2 to supply the image signals corresponding to the control marks M to the image forming engines 10Y, 10M, 10C, and 10Bk, and immediately corrects color misregistration. The mode is executed (ST12). The color misregistration correction mode here is a rough adjustment step, and does not correct the toner image formation position to such an extent that the color misregistration can be completely eliminated. The amount of color misregistration after completion of assembly or after disassembly and repair is much larger than the amount of color misregistration that occurs during daily use. In order to detect this large color misregistration amount, the intermediate transfer belt 20 is adjacent to each other. It is necessary to set a large interval between the two-color control marks M and M formed above. Therefore, in this coarse adjustment step, control is performed to roughly grasp the toner image formation position and correct it. When the rough adjustment step is executed, the correction mode execution unit 4 checks whether or not the correction control unit 3 can properly generate the correction data, and if the correction data can be generated, It is determined that the coarse adjustment step has been normally completed (ST13). If correction data cannot be created, it is considered that some abnormality exists in the image forming engine and the intermediate transfer belt. Therefore, a fail process is performed to notify the line engineer or field engineer of that fact (ST1). 4) The color misregistration correction mode ends here.

  Next, when it is determined in ST13 that the rough adjustment step has been normally completed, a second color misregistration correction mode is subsequently performed (ST15). The color misregistration correction mode here is a fine adjustment step, in which the toner image forming position is corrected more finely than the rough adjustment step, and the color misregistration is completely eliminated. This fine adjustment step is exactly the same as the content of the color misregistration correction mode which has been conventionally performed under a predetermined condition while using the printer. When the fine adjustment step is executed, the correction mode execution unit 4 checks whether or not the correction control unit 3 can properly generate correction data, and if correction data can be generated, It is determined that the fine adjustment step is normally completed (ST16), and one count value of the correction mode counter 5 is added (ST17).

  On the other hand, when the count value C ≠ 0 of the correction mode counter 5 in ST11, the correction mode execution unit 4 does not immediately perform the color misregistration correction mode and determines whether or not the conditions of ST20, ST21, and ST22 in FIG. Only when they are checked and matched, the color misregistration correction mode is executed (ST23). That is, whether or not the temperature in the printer has risen by a predetermined temperature or more compared to the previous color misregistration correction mode, or whether important parts such as the image forming engines 10Y, 10M, 10C, and 10Bk and the intermediate transfer belt 20 have been replaced Whether or not a predetermined time or more has elapsed since the previous execution of the color misregistration correction mode is sequentially checked, and if there is any, the color misregistration correction mode is immediately executed. These conditions are factors that are considered to cause a deviation in the relative positional relationship between the toner images formed by the image forming engines 10Y, 10M, 10C, and 10Bk, and it is determined that such factors exist. In addition, the color misregistration correction mode is executed. If the color misregistration correction mode is normally completed, the count value of the correction mode counter 5 is incremented by one. Note that conditions other than those described in ST20, ST21, and ST22 may be used as the start conditions for the color misregistration correction mode.

  According to this flowchart, the color misregistration correction mode is executed regardless of whether the count value C = 0 of the correction mode counter 5 or C ≠ 0, and if correction data is generated and completed normally. In the subsequent recording image forming operation, it is possible to form a high-quality recorded image without color misregistration.

  In particular, if the execution timing of the color misregistration correction mode is determined according to this flowchart, when the count value C = 0 of the correction mode counter 5, that is, the stage of the finished product inspection after assembly in the factory, or the disassembly / repair at the installation / use location. After that, if you just turn on the printer, the color misregistration correction mode will be executed immediately without any command input, reducing labor and time for engineers and field engineers. It is possible to prevent the failure to confirm the autonomy of the apparatus after repairing and to detect inadequate repair work later.

  In the above description, the counter 5 is used as a means for storing the past execution history of the color misregistration correction mode. However, a flag may be used and only the presence or absence of past execution may be stored. Absent. However, if the cumulative number of executions of the color misregistration correction mode is counted using the counter 5, it is possible to grasp how often the color misregistration correction mode is executed for each user, and the color misregistration correction mode. It is also possible to appropriately set the execution condition for each user, reduce the number of times of execution of the correction mode, and increase the productivity of the recorded image.

1 is a configuration diagram illustrating an example of a color image forming apparatus to which the present invention is applied. 3 is a block diagram showing a control system for correcting a toner image forming position and density using a control mark. FIG. 2 shows an example of a toner mark for image control according to the present invention. It is a block diagram which shows the structure of a control information detection means. It is a figure which shows the positional relationship of the visual field of a light receiving element on an intermediate transfer belt, and a control mark, and the change of the sensor output signal and peak detection signal at that time. It is a flowchart which shows the process for judging the execution timing of color misregistration correction mode. It is a branch from ST11 of the flowchart shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Control information detection means, 2 ... Mark reference signal generation part, 3 ... Correction control part, 4 ... Correction mode execution part, 5 ... Correction mode counter, 10Y, 10M, 10C, 10Bk ... Image formation engine, M ... Image control Toner mark

Claims (4)

A plurality of color image forming engines for forming toner images according to image information, and superimposing the color toner images formed by these image forming engines to form a color image on a recording sheet or an intermediate transfer belt,
In a color image forming apparatus having a color misregistration correction mode for detecting a color misregistration amount when each color toner image is superimposed and correcting a toner image forming position in each image forming engine based on the detected value.
A means for storing the color misregistration correction mode when it is completed, and a result stored in the storage means after activation of the apparatus main body, it was determined that the color misregistration correction mode has never been completed in the past. A color image forming apparatus comprising: a correction mode execution unit that executes an initial color misregistration correction mode. 2. The color image forming apparatus according to claim 1, wherein the storage unit is a counter that counts the number of completion times of the color misregistration correction mode. The color image forming apparatus according to claim 1, wherein the storage unit can be initialized. 2. The color image forming apparatus according to claim 1, wherein the initial color misregistration correction mode includes a coarse adjustment step and a fine adjustment step that follows the coarse adjustment step.

Images