JP5787618B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as an electrophotographic printer, a copying machine, and a facsimile, and more particularly to an image forming apparatus that forms and prints a color image.

  In this type of image forming apparatus, since a color image is formed by superimposing a plurality of color images, a problem of color misregistration occurs. For example, each latent image is written on a plurality of image carriers (photoreceptor drums) with laser light from an optical scanning device (LSU), and each latent image on each image carrier is developed with toner of each color. A visible image of each color is formed on the image carrier, and the visible image of each color is transferred from each image carrier to an intermediate transfer member (intermediate transfer belt), and the color visible on the intermediate transfer member. In a configuration in which an image is formed and a color visible image is transferred from an intermediate transfer member to a recording sheet, the visible image of each color is shifted during transfer from each image carrier to the intermediate transfer member. Color misregistration may occur and the quality of the color image is deteriorated. For this reason, the shift amount (registration adjustment value) of the visible image of each color on the intermediate transfer member is obtained by measurement, the latent image writing timing on each image carrier is controlled, and each latent image on each image carrier is controlled. The position of the image is shifted by the respective registration adjustment values, thereby correcting the shift of the visible image of each color.

  However, the position of each latent image on each image carrier changes due to a change in the temperature (atmosphere temperature or internal temperature) of the optical scanning device (LSU), and the amount of shift of the visible image of each color on the intermediate transfer member is different. Change. Therefore, if the registration adjustment value is fixedly maintained, the shift of the visible image of each color cannot be corrected accurately.

  For this reason, for example, in Patent Document 1, a temperature sensor is provided in the vicinity of the optical scanning device (LSU), the registration adjustment value is corrected in accordance with the change in the ambient temperature detected by the temperature sensor, and the shift of the visible image of each color is detected. Is corrected more accurately.

JP 2007-86439 A

  However, in the experiments by the inventors of the present application, the deviation of the visible image of each color is accurately determined only by correcting the resist adjustment value in accordance with the change in the temperature (atmosphere temperature or internal temperature) of the optical scanning device (LSU). It has also been found that there is a possibility that the deviation of the visible image of each color may be further increased.

  FIG. 7 is a graph showing experimental results by the inventors of the present application. In the graph of FIG. 7, the horizontal axis x represents the elapsed time m from the power-on of the image forming apparatus, and the vertical axis y represents the shift of the visible image of each color on the intermediate transfer body (intermediate transfer belt) of the image forming apparatus. Indicates the amount.

  In the period M1 until the elapsed time m from the power-on is 300 minutes, the registration adjustment value is obtained by measuring in a short time immediately after the power-on (m = 0 minutes), and subsequently, the image forming apparatus. As a result, a large number of recording papers are continuously printed, and the internal temperature of the optical scanning device gradually increases accordingly. Further, in the period M2 after the elapsed time m exceeds 300 minutes, intermittent printing is performed by the image forming apparatus, and the number of printed sheets per unit time is reduced as compared with the period M1, and accordingly, the optical scanning device is used. The internal temperature gradually decreases or stabilizes.

  The characteristic f2 indicates a change in the shift amount of the visible image of each color when the registration adjustment value is kept constant regardless of the internal temperature of the optical scanning device. Further, the characteristic f3 indicates a change in the shift amount of the visible image of each color when the registration adjustment value is corrected according to the internal temperature of the optical scanning device.

  On the other hand, the correction of the registration adjustment value based on the internal temperature of the optical scanning device is performed by the following equation (1), for example.

B = A + j (t1-t2) (1)
Where B is the corrected registration adjustment value, A is the registration adjustment value before correction, j is a positive coefficient, and t1 is the internal temperature of the optical scanning apparatus when the registration adjustment value is obtained. T2 is the internal temperature of the optical scanning device during printing.

  Here, in the period M1, the characteristic f2 of the shift amount of the visible image of each color when the registration adjustment value is kept constant is rising to the right, and the internal temperature of the optical scanning device is rising. Thus, as shown by the approximate characteristic f2 ′ of the characteristic f2, it can be said that the shift amount of the visible image of each color increases in proportion to the internal temperature of the optical scanning device.

  In the period M1, since the internal temperature of the optical scanning device is increasing, j (t1-t2) in the above formula (1) becomes a negative value, and the internal temperature of the optical scanning device during printing is increased. The more the registration adjustment value B is corrected in the negative direction according to the internal temperature, the characteristic f3 of the shift amount of the visible image of each color when the registration adjustment value is corrected according to the internal temperature becomes substantially flat. .

However, in the period M1, as is apparent from a comparison between the characteristic f2 when the registration adjustment value is kept constant and the characteristic f3 when the registration adjustment value is corrected, the latter characteristic f3 is more acceptable for each color. The amount of deviation of the visual image is large. As apparent from the characteristic f2 when the registration adjustment value is kept constant, the internal temperature of the optical scanning device rises until the elapsed time m from the power-on reaches approximately 30 minutes. Nevertheless, the shift amount of the visible image of each color changes greatly in the negative direction, and the registration adjustment value B is more negative than the registration adjustment value A according to the internal temperature of the optical scanning device. This is because it is further corrected.

  In addition, at the beginning of the period M2, as shown in the characteristic f3 when the registration adjustment value is corrected according to the internal temperature of the optical scanning device, the shift amount of the visible image of each color is rapidly reduced. This is because, as is apparent from the characteristic f2 when the registration adjustment value is kept constant at the beginning of the period M2, the shift amount of the visible image of each color changes significantly in the positive direction. This is because the amount of deviation of the visible image of each color when the registration adjustment value is corrected also changes in the positive direction.

  Therefore, under the condition that continuous printing is performed in the period M1 and intermittent printing is performed in the subsequent period M2, the shift of the visible image of each color when the registration adjustment value is corrected according to the internal temperature of the optical scanning device. Immediately after the power is turned on, the amount changes greatly in the negative direction and then increases, and when switching from continuous printing to intermittent printing, the amount changes significantly in the positive direction and decreases. To do.

  Under the condition that the image forming apparatus is set in a standby state immediately after the power is turned on and intermittent printing is subsequently performed, each color can be changed when the registration adjustment value is corrected according to the internal temperature of the optical scanning apparatus. Although the shift amount of the visual image becomes small, when continuous printing is performed after this, the shift amount of the visible image of each color also increases before and after the continuous printing.

  From such an experiment, it is not possible to accurately correct the deviation of the visible image of each color simply by correcting the registration adjustment value according to the temperature (atmosphere temperature or internal temperature) of the optical scanning device. It can be seen that there is a possibility that the deviation of the visible image is further increased.

  In addition, the inventors of the present application have found that a significant shift in the visible image of each color that occurs regardless of the temperature of the optical scanning device has caused a change in the operating rate of the image forming process unit in the image forming apparatus. I found out what happened when it was big.

  Here, the image forming process unit writes a latent image on an image carrier (photosensitive drum) with a laser beam of an optical scanning device (LSU), and then develops the latent image on the image carrier, from the image carrier. This is a configuration for carrying out an image forming process from transferring a visible image to an intermediate transfer member (intermediate transfer belt) and transferring the visible image from the intermediate transfer member to recording paper. The configuration for fixing the visible image on the recording paper is not included.

  For example, in the graph of FIG. 7, the registration adjustment value is obtained in a short time immediately after the power is turned on (m = 0 minutes) until the elapsed time m after the power is turned on reaches approximately 30 minutes. Since a large number of recording sheets are continuously printed by the apparatus, the operation rate of the image forming process section has increased substantially from 0% to 100%, and the amount of shift in the visible image of each color has increased. Yes. Also, when the elapsed time m exceeds 300 minutes, since the continuous printing is switched to the intermittent printing, the operation rate of the image forming process section is substantially reduced from 100%. The amount of deviation of the visible image is large.

  Therefore, the present invention has been made in view of the above-described conventional problems, and by correcting the registration adjustment value according to not only the temperature of the optical scanning device but also the operating rate of the image forming process unit, each color is corrected. An object of the present invention is to provide an image forming apparatus capable of more accurately correcting a shift of a visible image.

In order to solve the above problems, an image forming apparatus of the present invention writes each latent image on a plurality of image carriers by laser light of an optical scanning device, develops the latent image of each image carrier, and An image forming process unit for forming a visible image of each color on each image carrier, transferring the visible image of each color on each image carrier to a recording medium, and forming a color visible image; A registration correction unit that detects a shift of the test pattern of each color in the visible image of the color as a resist adjustment value, and corrects the position of the visible image of each color that is superimposed and transferred based on the registration adjustment value; An image forming apparatus, a temperature detection unit that detects a temperature of the optical scanning device, an operation rate calculation unit that calculates an operation rate of the image forming process unit, a temperature change by the temperature detection unit, and the operation rate based on a change in the operating rate by the arithmetic unit , The resist and a registration correction arithmetic unit for correcting the adjustment value, the temperature detection unit includes: a resist step of measuring a resist adjustment value A to form the respective color test patterns, forming a visible image of the color A change in temperature in the printing process is detected, the operating rate calculating unit calculates a change in operating rate in the resist process and the printing process, and the resist correction calculating unit is detected by the temperature detecting unit. Based on the detected change in temperature, the resist adjustment value A measured in the resist process is corrected to obtain a resist adjustment value B. Further, based on the change in operating rate calculated by the operating rate calculation unit, the resist The registration adjustment value C is obtained by correcting the adjustment value B, and the registration adjustment value C approaches the registration adjustment value B as the change in the operating rate decreases. Characterized by Uni corrected.

  In such an image forming apparatus of the present invention, not only the temperature change of the optical scanning device but also the change in the operating rate of the image forming process unit is obtained, and the registration adjustment value is set based on the change in the temperature and the change in the operating rate. Since the correction is performed, the shift of the visible image of each color can be corrected more accurately by using the registration adjustment value.

  The image forming process unit writes a latent image on an image carrier (photosensitive drum) with laser light from an optical scanning device (LSU), develops the latent image on the image carrier, and then intermediates the image carrier. This configuration is used to transfer the visible image to the transfer body (intermediate transfer belt) and to transfer the visible image from the intermediate transfer body to the recording paper. It is assumed that a configuration for fixing a visible image on a sheet is not included.

  In the image forming apparatus of the present invention, the operating rate calculation unit calculates the operating rate of the image forming process unit every predetermined time, and determines a change in operating rate for each predetermined time. Alternatively, the operating rate calculation unit is configured to operate the image forming process unit for a predetermined time when the test pattern for each color is formed and the image forming process unit for forming a visible image of each color. Is obtained as a change in the operation rate of the image forming process unit.

  In this way, the operating rate of the image forming process unit can be obtained in a predetermined time unit.

  For example, in the image forming apparatus of the present invention, the temperature change by the temperature detection unit is detected when the temperature detected when the test pattern of each color is formed and the visible image of each color is formed. It is the difference from temperature.

In the image forming apparatus of the present invention, the optical scanning device includes a polygon mirror that is driven to rotate, the laser beam is reflected by the polygon mirror and scanned in the main scanning direction, and the operation rate calculation is performed. The unit obtains an operation rate of a drive motor that rotationally drives the polygon mirror as an operation rate of the image forming process unit.

  As described above, the operation rate of the polygon mirror drive motor may be obtained as the operation rate of the image forming process unit. In addition, the operating rate of the drive motor of the image carrier, the operating rate of the developing device, and the like may be obtained as the operating rate of the work process.

  In the present invention, not only the temperature change of the optical scanning device but also the change in the operation rate of the image forming process unit is obtained, and the registration adjustment value is corrected based on the change in the temperature and the change in the operation rate. Therefore, using this registration adjustment value, it is possible to more accurately correct the shift of the visible image of each color.

1 is a cross-sectional view showing an embodiment of an image forming apparatus of the present invention. FIG. 2 is a block diagram illustrating a control system of the image forming apparatus in FIG. 1. 2 is a flowchart showing a procedure of a resist process of the image forming apparatus of FIG. FIG. 6 is a plan view schematically showing test patterns transferred to both ends of an intermediate transfer belt. 3 is a flowchart illustrating a procedure of a printing process of the image forming apparatus in FIG. 1. It is explanatory drawing of internal temperature t1 (degreeC) and operation rate a in a resist process, internal temperature t2 (degreeC) and operation rate b in a printing process, and each formula (1), (2). A characteristic f1 indicating a shift amount of a visible image of each color when the registration adjustment value is corrected according to a change in the internal temperature of the optical scanning device and an operation rate of the image forming process unit, and each color when the registration adjustment value is not corrected It is a graph which shows the characteristic f3 which shows the deviation | shift amount of the visible image of each color when the characteristic f2 which shows the deviation | shift amount of a visible image, and the registration adjustment value is correct | amended according to the change of the internal temperature of an optical scanning device.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a cross-sectional view showing an embodiment of the image forming apparatus of the present invention. The image forming apparatus 1 is a so-called multi-function machine having a scanner function, a copying function, a printer function, a facsimile function, and the like, and transmits an image of a document read by the image reading device 41 to the outside (corresponding to a scanner function). The image of the read original or the image received from the outside is recorded and formed on a recording sheet in color or single color (corresponding to a copying function, a printer function, and a facsimile function).

  In order to print an image on a recording paper, the image forming apparatus 1 includes an optical scanning device 11, a developing device 12, a photosensitive drum 13, a drum cleaning device 14, a charger 15, an intermediate transfer belt device 16, a fixing device 17, and a paper transport. A path S, a paper feed cassette 18, a paper discharge tray 19, and the like are provided.

  The image data handled in the image forming apparatus 1 uses data corresponding to a color image using each color of black (K), cyan (C), magenta (M), yellow (Y), or a single color (for example, black). This is in accordance with the monochrome image. For this reason, four each of the developing device 12, the photosensitive drum 13, the drum cleaning device 14, and the charger 15 are provided so as to form four types of toner images corresponding to the respective colors, and black, cyan, Four image stations Pa, Pb, Pc, and Pd are configured in association with magenta and yellow.

  Each photosensitive drum 13 has a photosensitive layer on the surface thereof. Each charger 15 is a charging means for uniformly charging the surface of each photosensitive drum 13 to a predetermined potential. In addition to a contact-type roller-type or brush-type charger, a charger-type charger. Is used.

  The optical scanning device 11 is a laser scanning unit (LSU) provided with a laser diode and a reflection mirror, and exposes the surface of each charged photosensitive drum 13 according to image data and corresponds to the image data on those surfaces. An electrostatic latent image is formed.

  Each developing device 12 develops the electrostatic latent image formed on the surface of each photoreceptor drum 13 with toner of each color, and forms a toner image (visible image) on the surface of each photoreceptor drum 13. Each drum cleaning device 14 removes and collects toner remaining on the surface of each photosensitive drum 13 after development and image transfer.

  The intermediate transfer belt device 16 is disposed above each photosensitive drum 13 and includes an intermediate transfer belt 21, an intermediate transfer belt driving roller 22, a driven roller 23, four intermediate transfer rollers 24, and a belt cleaning device 25. ing.

  The intermediate transfer belt 21 is a film formed in an endless belt shape. The intermediate transfer belt drive roller 22, the driven roller 23, each intermediate transfer roller 24, and the like stretch and support the intermediate transfer belt 21, and rotate the intermediate transfer belt 21 in the direction of arrow C.

  Each intermediate transfer roller 24 is rotatably supported in the vicinity of the intermediate transfer belt 21 and is pressed against the respective photosensitive drums 13 via the intermediate transfer belt 21. The toner images on the surfaces of the respective photosensitive drums 13 are sequentially transferred to the intermediate transfer belt 21 so as to form a color image (color visible image) in which the toner images of the respective colors are superimposed on the intermediate transfer belt 21. Transfer of the toner image from each photosensitive drum 13 to the intermediate transfer belt 21 is performed by each intermediate transfer roller 24 that is in pressure contact with the back surface of the intermediate transfer belt 21. Each intermediate transfer roller 24 is a roller having a metal (for example, stainless steel) shaft as a base and a surface covered with a conductive elastic material (for example, EPDM, urethane foam, or the like). Each intermediate transfer roller 24 is applied with a high-voltage transfer bias (a high voltage having a polarity (+) opposite to the toner charging polarity (−)) in order to transfer the toner image. A high voltage is uniformly applied to the recording paper by the material.

  The color image thus formed on the intermediate transfer belt 21 is conveyed together with the intermediate transfer belt 21 and transferred onto a recording sheet in a nip region between the intermediate transfer belt 21 and the secondary transfer roller 26a of the secondary transfer device 26. .

  The secondary transfer roller 26a of the secondary transfer device 26 has a voltage for transferring the toner image of each color on the intermediate transfer belt 21 to a recording sheet (a high polarity (+) opposite to the toner charging polarity (-)). Voltage) is applied.

  Further, the toner image on the intermediate transfer belt 21 may not be completely transferred onto the recording paper by the secondary transfer device 26, and the toner may remain on the surface of the intermediate transfer belt 21. Causes color mixing. For this reason, the residual toner on the surface of the intermediate transfer belt 21 is removed and collected by the belt cleaning device 25. The belt cleaning device 25 is provided with, for example, a cleaning blade that contacts the surface of the intermediate transfer belt 21 and removes residual toner as a cleaning member, and the intermediate transfer belt 21 is driven by the driven roller 23 at a portion where the cleaning blade comes into contact. The back side is supported.

  The recording sheet is conveyed to the fixing device 17 after the color image is transferred in the nip area between the intermediate transfer belt 21 and the secondary transfer roller 26 a of the secondary transfer device 26. The fixing device 17 includes a heating roller 31, a pressure roller 32, and the like, and sandwiches and conveys a recording sheet between the heating roller 31 and the pressure roller 32.

  The heating roller 31 is controlled so as to have a predetermined fixing temperature, and the recording sheet is thermocompression bonded together with the pressure roller 32 to melt and mix the color image (toner image of each color) transferred to the recording sheet. , And heat-fixed to the recording paper.

  In addition, a paper feed cassette 18 that supplies recording paper is provided below the image forming apparatus 1. The image forming apparatus 1 is provided with a paper transport path S for sending the recording paper supplied from the paper feed cassette 18 to the paper discharge tray 19 via the secondary transfer device 26 and the fixing device 17.

  A paper pickup roller 33 is provided at the end of the paper feeding cassette 18, and the recording paper is pulled out from the paper feeding cassette 18 one by one by the paper pickup roller 33 and conveyed to the paper conveyance path S.

  A paper registration roller 34, a fixing device 17, a transport roller 35, a paper discharge roller 36, and the like are arranged along the paper transport path S. The conveyance roller 35 is a small roller for promoting and assisting conveyance of the recording paper, and a plurality of sets are provided.

  The sheet registration roller 34 temporarily stops the recording sheet that has been conveyed, aligns the leading end of the recording sheet, and in the nip region between the intermediate transfer belt 21 and the secondary transfer roller 26a of the secondary transfer device 26, the intermediate transfer belt. In order to transfer the color image on the recording sheet 21 to the recording sheet, the recording sheet is conveyed with good timing in accordance with the rotation of each photosensitive drum 13 and the intermediate transfer belt 21.

  Further, the recording paper is fixed with a color image by the fixing device 17, passes through the fixing device 17, and is then discharged face down on the paper discharge tray 19 by the paper discharge roller 36.

  When printing not only on the front side of the recording paper but also on the back side, the recording paper is transported by the paper discharge roller 36, and then the paper discharge roller 36 is stopped and then reversely rotated, so that the recording paper is reversed. , Reverse the front and back of the recording paper, guide the recording paper to the paper registration roller 34, record and fix the image on the back of the recording paper, as well as the front of the recording paper, and eject the recording paper to the paper It is discharged to the tray 19.

  Next, the image reading device 41 and the document conveying device 42 mounted on the upper part of the main body of the image forming apparatus 1 will be described. The document conveying device 42 is pivotally supported by the back side of the image reading device 41 by a hinge (not shown) and opened and closed by moving the front portion up and down. When the document conveying device 42 is opened, the platen glass 44 of the image reading device 41 is opened, and the document is placed on the platen glass 44.

  The image reading device 41 includes a platen glass 44, a first scanning unit 45, a second scanning unit 46, an imaging lens 47, a CCD (Charge Coupled Device) 48, and the like. The first scanning unit 45 includes a light source 51 and a first reflecting mirror 52, and exposes a document on the platen glass 44 by the light source 51 while moving at a constant speed V by a distance corresponding to the document size in the sub-scanning direction. Then, the reflected light is reflected by the first reflecting mirror 52 and guided to the second scanning unit 46, thereby scanning the image on the surface of the document in the sub-scanning direction. The second scanning unit 46 includes second and third reflecting mirrors 53 and 54, and follows the first scanning unit 45 while moving at a speed V / 2, while reflecting the reflected light from the document to the second and second. The light is reflected by the three reflecting mirrors 53 and 54 and guided to the imaging lens 47. The imaging lens 47 condenses the reflected light from the document on the CCD 48 and forms an image on the surface of the document on the CCD 48. The CCD 48 repeatedly scans the document image in the main scanning direction, and outputs an analog image signal of one main scanning line each time.

  Further, the image reading device 41 can read not only a stationary document but also an image on the surface of the document conveyed by the document conveying device 42. In this case, the first scanning unit 45 is moved below the original reading glass 55, and the second scanning unit 46 is positioned in accordance with the position of the first scanning unit 45. In this state, the original is conveyed by the original conveying device 42. To start.

  In the document transport device 42, the pickup roller 56 is pressed against the document on the document tray 57 and rotated to pull out the document, transport the document through the document transport path 58, and transport the document between the document reading glass 55 and the reading guide plate 59. Further, the original is further conveyed from the paper discharge roller 61 to the paper discharge tray 62. Along the document conveyance path 58, a registration roller 63 that conveys the document after aligning the front end thereof and a conveyance roller 64 that conveys the document are arranged.

  When the document is transported, the light source 51 of the first scanning unit 45 illuminates the surface of the document through the document reading glass 55, and the reflected light from the surface of the document is reflected by the reflection mirrors of the first and second scanning units 45 and 46. The light is guided to the imaging lens 47, and the reflected light from the document surface is condensed on the CCD 48 by the imaging lens 47, and an image on the document surface is formed on the CCD 48, thereby reading the image on the document surface.

  When reading the back side of the document, the intermediate tray 67 is rotated as indicated by the dotted line around its axis, and the discharge roller 61 is in the process of discharging the document from the discharge roller 61 to the discharge tray 62. Is stopped, the document is received on the intermediate tray 67, the paper discharge roller 61 is rotated in the reverse direction, the document is guided to the registration roller 63 through the reverse conveyance path 68, and the document surface is reversed. In the same manner as the image of FIG. 5, the image on the back side of the document is read, the intermediate tray 67 is returned to the original position indicated by the solid line, and the document is discharged from the discharge roller 61 to the discharge tray 62.

  The original image read by the CCD 48 is output from the CCD 48 as an analog image signal, and the analog image signal is A / D converted into a digital image signal (image data). The image data is subjected to various image processing and sent to the optical scanning device 11 of the image forming apparatus 1, where the image is recorded on a recording sheet, and the recording sheet is output as a copy original. Is done.

  By the way, after each color toner image is formed on the photosensitive drum 13 of each image forming station Pa, Pb, Pc, Pd, the respective color toner image on each photosensitive drum 13 is formed on the intermediate transfer belt 21. Since the images are sequentially superimposed and transferred, the transfer positions of the toner images of the respective colors on the intermediate transfer belt 21 are shifted, color shifts may occur, and the quality of the color image may be deteriorated.

  For this reason, the registration process is performed when the image forming apparatus 1 is started, and the deviation amount (registration adjustment value) of each color toner image on the intermediate transfer belt 21 is measured and obtained. In the color image printing process, the timing of writing the electrostatic latent image on each photoconductor drum 13 by the optical scanning device 11 is controlled, and the position of the electrostatic latent image on each photoconductor drum 13 is changed to the corresponding position. Deviation of the toner images of the respective colors on the intermediate transfer belt 21 is corrected by shifting the registration adjustment value. Thereby, the color shift of the color image transferred to the recording paper is suppressed.

  However, the position of each electrostatic latent image on each photosensitive drum 13 changes due to a change in the temperature (atmosphere temperature or internal temperature) of the optical scanning device (LSU) 11, and each color toner image on the intermediate transfer belt 21. It is well known that the amount of misalignment changes. For this reason, the misregistration of the toner images of the respective colors cannot be corrected accurately if the registration adjustment value is kept fixed.

  Further, as described above, the inventors of the present application, based on the experimental results shown in the graph of FIG. 7 and the like, show the visible image of each color generated regardless of the temperature (atmosphere temperature or internal temperature) of the optical scanning device 11. It has been found that there is a large shift, and this large shift occurs when the change in the operation rate of the image forming process unit in the image forming apparatus 1 is large.

  Therefore, in the present embodiment, a change in the internal temperature of the optical scanning device 11 is detected, a change in the operation rate of the image forming process unit in the image forming apparatus 1 is obtained, and based on the change in the internal temperature and the change in the operation rate, The registration adjustment value is corrected to accurately correct the deviation of the toner images of the respective colors.

  The image forming process unit includes an optical scanning device 11, a developing device 12, a photosensitive drum 13, a drum cleaning device 14, a charger 15, and an intermediate transfer belt device 16. Each electrostatic latent image is written on the photosensitive drum 13, and then each electrostatic latent image on each photosensitive drum 13 is developed to form a toner image of each color on each photosensitive drum 13. In this configuration, a toner image of each color is transferred from the body drum 13 to the intermediate transfer belt 21 and overlapped, and an image forming process from the transfer of the color image to the recording paper is performed. It is assumed that the recording paper supply process from the paper feed cassette 18 and the fixing process of the color image on the recording paper by the fixing device 17 are not included.

  Next, a registration process for measuring and obtaining the resist adjustment values for each color and a color image printing process for suppressing color misregistration using the registration adjustment values for each color will be described in detail.

  FIG. 2 is a block diagram illustrating a control system for controlling the image forming apparatus 1 to perform a resist process and a printing process. In FIG. 2, a main control unit 71 controls the image forming apparatus 1 in an integrated manner, and includes a CPU, a RAM, a ROM, various interfaces, and the like.

  The printing unit 72 includes an optical scanning device (LSU) 11, a developing device 12, a photosensitive drum 13, a drum cleaning device 14, a charger 15, an intermediate transfer belt device 16, a fixing device 17, a paper transport path S, a paper supply path in FIG. It corresponds to a paper cassette 18, a paper discharge tray 19, and the like, and prints an image on recording paper.

  Further, the optical scanning device 11 of the printing unit 72 includes an LSU control unit 81, each laser diode 82 corresponding to black, cyan, magenta, and yellow, and a polygon mirror 83 that reflects each laser beam emitted from each laser diode 82. (Shown in FIG. 1), a polygon motor 84 that rotationally drives the polygon mirror 83 at a high speed, a temperature sensor 85 (shown in FIG. 1) that detects the internal temperature of the optical scanning device 11, and the like. The LSU control unit 81 of the optical scanning device 11 drives and controls the polygon motor 84 to rotate the polygon mirror 83 at high speed, and modulates the intensity of the laser light of each laser diode 82 according to the image data. The laser light from each laser diode 82 is incident on the polygon mirror 83 rotating at high speed, reflected, and incident on the surface of each photosensitive drum 13 while being repeatedly deflected in the main scanning direction. Thereby, each electrostatic latent image corresponding to the image data is formed on the surface of each photosensitive drum 13.

  The image processing unit 73 performs various image processes on the image data. The input operation unit 74 includes, for example, a plurality of input keys and a liquid crystal display device. The memory (storage unit) 75 is, for example, a hard disk device (HDD), and stores various data and programs.

  The two registration sensors 76 are for detecting a test pattern formed on the intermediate transfer belt 21 of the intermediate transfer belt device 16.

  In such a configuration, the main control unit 71 performs a registration process for measuring and obtaining the registration adjustment values of the respective colors when the image forming apparatus 1 is started, for example.

  Next, the procedure of the resist process will be described in detail with reference to the flowchart of FIG. This registration step is performed, for example, in a short time immediately after power-on (elapsed time m = 0) in the graph of FIG.

  First, when the power is turned on and the image forming apparatus 1 is activated, the main control unit 71 starts a registration process, and the internal temperature t1 (° C.) of the optical scanning device 11 detected by the temperature sensor 85 at the start. ) And the detected internal temperature t 1 (° C.) of the optical scanning device 11 is stored in the memory 75. Further, the operating rate of the image forming process unit for a predetermined time (for example, 30 minutes) related to the registration process is obtained, and the operating rate of the image forming process unit for the predetermined time is stored in the memory 75.

  For example, the predetermined time is sequentially set at the predetermined time period by a timer built in the image forming apparatus 1. Further, as the operating rate of the image forming process unit, the operating rate ((driving time) / (predetermined time)) of the polygon motor 84 that is rotationally driven by the LSU control unit 81 is obtained and stored. The polygon motor 84 is always rotationally driven during the image forming process. Even if the polygon motor 84 is excessively driven before and after the image forming process, the extra time is compared with a predetermined time (for example, 30 minutes). It is a short time (about 10 seconds). For this reason, the operation rate of the polygon motor 84 can be obtained as the operation rate of the image forming process unit. For example, in the graph of FIG. 7, the predetermined time Δm1 includes a period in which the power is off (the polygon motor 84 is not driven), and the registration process is performed near the end of the predetermined time Δm1 (30 minutes). The operation rate a of the polygon motor 84 for the predetermined time Δm1 related to the process becomes a value close to “0”, and the operation rate a of a value close to “0” is stored in the memory 75 as the operation rate of the polygon motor 84 for the predetermined time Δm1. (Step S101).

  Even when the power is off, the predetermined time Δm1 can be sequentially set by operating the timer.

  In the resist process, for each photoconductor drum 13 (each color), an electrostatic latent image of a pair of test patterns is formed on both ends of the photoconductor drum 13 by the optical scanning device 11, and the photoconductor drum is developed by the developing device 12. The electrostatic latent images at both ends of the photosensitive drum 13 are developed to form test patterns (toner images) at both ends of the photosensitive drum 13, and then the test patterns (toner images) at both ends of the photosensitive drum 13 are formed. ) Is transferred to both end portions of the intermediate transfer belt 21.

  FIG. 4 schematically shows a pair of test patterns P1 and P2 transferred to both ends of the intermediate transfer belt 21 for each color (YMCK). In the vicinity of both ends of the intermediate transfer belt 21, resist sensors 76 for detecting the test patterns P1 and P2 are provided. Each registration sensor 76 detects each test pattern P1 and P2 conveyed in the sub-scanning direction as the intermediate transfer belt 21 rotates in each color, and sequentially outputs each detection output to the main controller 71 ( Step S102).

  The main controller 71 inputs the detection output of each registration sensor 76 for each color, and the sub-scan of each test pattern P1, P2 based on the detection timing of each test pattern P1, P2 and the circumferential movement speed of the intermediate transfer belt 21. The transfer position in the direction is obtained, the shift amount (registration adjustment value) of each test pattern P1, P2 in the sub-scanning direction is measured, and the registration adjustment value of each color is stored in the memory 75 (step S103).

  As is well known, if a pattern oblique to the sub-scanning direction is applied as the test patterns P1 and P2, the deviation of the test patterns P1 and P2 in the main scanning direction can also be measured.

  As described above, in the registration process, the internal temperature t1 (° C.) of the optical scanning device 11 detected by the temperature sensor 85 is acquired, the internal temperature t1 (° C.) is stored in the memory 75, and a predetermined process related to the registration process is performed. The operation rate a of the polygon motor 84 for a time (for example, 30 minutes) is obtained, the operation rate a is stored in the memory 75, and the registration adjustment values for the respective colors are obtained and stored in the memory 75.

  After the resist process is performed in this way, a color image printing process is performed as needed. For example, the main control unit 71 controls the image reading device 41 and the document conveying device 42 so that the document conveying device 42 conveys the document while the image reading device 41 reads the image of the document, The image data shown is stored in the memory 75, the image processing unit 73 processes the image data, and the printing unit 72 records the document image indicated by the image data in the memory 75 on the recording paper.

  Further, in the printing process, based on the change in the internal temperature of the optical scanning device 11 and the change in the operation rate of the polygon motor 84, the registration adjustment value of each color obtained in the registration process is corrected, and each photosensitive drum by the optical scanning device 11 is corrected. 13 is controlled to shift the position of the electrostatic latent image on each photosensitive drum 13 by the corrected registration adjustment value, whereby each color on the intermediate transfer belt 21 is controlled. The toner image is accurately corrected to prevent the color image transferred to the recording paper from being misaligned.

  Next, the printing process will be described in detail with reference to the flowchart of FIG. This printing process is performed at any time following the registration process performed in a short time immediately after power-on (elapsed time m = 0) in the graph of FIG. 7, for example.

  First, when a predetermined time (30 minutes) related to the printing process is set by the timer, the main control unit 71 acquires the internal temperature t2 (° C.) of the optical scanning device 11 detected by the temperature sensor 85 during the predetermined time. Then, the detected internal temperature t2 (° C.) of the optical scanning device 11 is stored in the memory 75, the operation rate b of the polygon motor 84 for a predetermined time is obtained, and the operation rate b of the polygon motor 84 is stored in the memory 75. To remember. For example, as shown in the graph of FIG. 7, in a period M1 until the elapsed time m from the power-on becomes 300 minutes, a large number of recording sheets are continuously printed, so the polygon motor 84 is continuously driven, The operation rate b of the polygon motor 84 for the predetermined time Δm2 related to the printing process is approximately “1”, and “1” is stored in the memory 75 as the operation rate b of the polygon motor 84 for the predetermined time Δm2 (step S201).

  Subsequently, the main control unit 71 reads out the registration adjustment value, the internal temperature t1 (° C.) of the optical scanning device 11 in the registration process, and the internal temperature t2 (° C.) of the optical scanning device 11 in the printing process from the memory 75. The registration adjustment value is corrected based on the following equation (1) (steps S202 and S203).

B = A + j (t1-t2) (1)
However, B is the corrected registration adjustment value, A is the registration adjustment value before correction obtained in the registration process, and j is a positive coefficient.

  Further, the main control unit 71 reads out the operation rate a of the polygon motor 84 related to the registration process and the operation rate b of the polygon motor 84 related to the printing process from the memory 75, and based on the following equation (2), The registration adjustment value B obtained in (1) is further corrected (steps S202 and S203).

C = B + k (ba) (2)
Here, C is a further corrected registration adjustment value, and k is a positive coefficient.

  Thereafter, the main control unit 71 controls the writing timing of each electrostatic latent image on each photoconductor drum 13 by the optical scanning device 11, and sets the position of the electrostatic latent image on each photoconductor drum 13. Shift by the corrected registration adjustment value C. Thereby, the deviation of the toner images of the respective colors on the intermediate transfer belt 21 is corrected appropriately (step S204).

  As described above, in the printing process, the internal temperature t2 (° C.) of the optical scanning device 11 detected by the temperature sensor 79 is acquired, the internal temperature t2 (° C.) is stored in the memory 75, and a predetermined process related to the printing process is performed. The operation rate b of the polygon motor 84 for the time (30 minutes) is obtained, and the operation rate b of the polygon motor 84 is stored in the memory 75. Then, the difference (change) between the internal temperature t1 (° C.) in the registration process in the memory 75 and the internal temperature t2 (° C.) in the printing process is obtained, and the operation rate of the polygon motor 84 related to the registration process in the memory 75 is obtained. The difference (change) between the operation rate b of the polygon motor 84 related to a and the printing process is obtained, and the registration adjustment value of each color obtained in the registration process is corrected based on the difference in the internal temperature and the difference in the operation rate. 11 controls the writing timing of each electrostatic latent image on each photoconductor drum 13 by 11 to shift the position of the electrostatic latent image on each photoconductor drum 13 by the respective corrected registration adjustment value, thereby intermediate The shift of the toner image of each color on the transfer belt 21 is corrected appropriately.

  FIG. 6 is an explanatory diagram of the internal temperature t1 (° C.) and operating rate a in the resist process, the internal temperature t2 (° C.) and operating rate b in the printing process, and the above formulas (1) and (2).

  As shown in FIG. 6, in the resist process, the internal temperature t1 (° C.) of the optical scanning device 11 and the operation rate a for a predetermined time (30 minutes) are obtained, and the resist adjustment value A is obtained.

  Next, in the printing process, the internal temperature t2 (° C.) of the optical scanning device 11 and the operation rate b for a predetermined time (30 minutes) are obtained. Then, the resist adjustment value A before correction in the resist process is corrected based on the above formula (1) using the internal temperature t1 (° C.) in the resist process and the internal temperature t2 (° C.) in the printing process. To do.

  However, the registration adjustment value B obtained from the equation (1) is a correction based only on the change in the internal temperature, and the shift of the visible image of each color cannot be corrected accurately. For example, in the graph of FIG. 7, the registration adjustment value corrected based only on the characteristic f2 indicating the change in the shift amount of the visible image of each color adjusted by the registration adjustment value A before correction, and the change in internal temperature alone. As is apparent from comparison with the characteristic f3 indicating the change in the shift amount of the visible image of each color adjusted by B, the shift amount of the visible image of each color is larger in the latter characteristic f3. However, in the adjustment using the registration adjustment value B corrected based only on the change in the internal temperature, the characteristic f3 indicating the change in the shift amount of the visible image of each color can be made substantially flat.

  Therefore, in the printing process, the registration adjustment value B corrected based on the above formula (1) is corrected based on the above formula (2) using the operating rate a in the resist process and the operating rate b in the printing process. . Since the registration adjustment value C obtained from the equation (2) is obtained by correcting the registration adjustment value B corrected based on the change in the internal temperature based on the change in the operating rate. The deviation can be corrected accurately.

  For example, in the graph of FIG. 7, the characteristic f1 indicates a change in the shift amount of the visible image of each color adjusted by the registration adjustment value C. The amount of deviation of the visible image of each color of the characteristic f1 is certainly smaller than the characteristics f2 and f3, and it can be seen that the deviation of the visible image of each color is corrected appropriately. Here, as described above, in the period M1 until the elapsed time m from power-on becomes 300 minutes, the operation rate a of the polygon motor 84 during the predetermined time Δm1 related to the registration process is a value close to “0”. In addition, since the operation rate b of the polygon motor 84 at the predetermined time Δm2 related to the printing process is approximately “1”, the operation rate is increased, and k (b−a) in the above equation (2) is substantially maximum. Is a positive value. For this reason, the registration adjustment value C is a value obtained by greatly correcting the registration adjustment value B in the positive direction, and the shift amount of the visible image of each color of the characteristic f1 becomes small.

In the graph of FIG. 7, in the period M2 after the elapsed time m exceeds 300 minutes, intermittent printing is performed by the image forming apparatus 1, and the number of printed sheets per unit time is reduced compared to the period M1, The operation rate b of the polygon motor 84 during the predetermined time Δm3 related to the printing process gradually decreases. For this reason, k (b−a) in the above equation (2) gradually decreases, and the registration adjustment value C approaches the registration adjustment value B. When the operation rate b of the polygon motor 84 for the predetermined time Δm3 becomes a value close to “0”, k (ba) in the above equation (2) also becomes a value close to “0”. At this time, the registration adjustment value C substantially coincides with the registration adjustment value B, and the characteristic f1 overlaps the characteristic f3 .

  Although the operation rate a of the polygon mirror 83 changes greatly depending on the set timing of the predetermined time Δm1 related to the registration process, the registration adjustment value A also changes greatly at this time, and the deviation amount of each color is temporarily adjusted to substantially “0”. Therefore, in the same manner as described above, the registration adjustment value A is corrected based on the difference in the internal temperature to obtain the registration adjustment value B, and further, the registration adjustment value B is corrected based on the difference in the operating rate. Thus, the shift amount of the visible image of each color can be reduced.

  As described above, in the present embodiment, the unadjusted resist adjustment value A obtained in the resist process is calculated using the internal temperature t1 (° C.) in the resist process and the internal temperature t2 (° C.) in the printing process. Correction based on the above equation (1) is performed to obtain a resist adjustment value B. Further, the resist adjustment value B is calculated by using the operation rate a related to the resist process and the operation rate b related to the printing process to the above equation (2). Since the registration adjustment value C is obtained based on the correction, the deviation of the toner images of the respective colors can be corrected appropriately.

  In the above embodiment, the internal temperature of the optical scanning device 11 is detected. However, the ambient temperature of the optical scanning device 11 is detected by arranging a temperature sensor 85 around the optical scanning device 11, and this atmospheric temperature. The registration adjustment value before correction obtained in the registration process may be corrected based on the change in the above. The operation rate of the polygon motor 84 is obtained as the operation rate of the work process. Instead, the operation rate of the drive motor of the intermediate transfer belt 21, the operation rate of the drive motor of the photosensitive drum 13, and the development device 12. You may obtain | require an operation rate etc. as an operation rate of a work process.

  Further, in the above embodiment, the respective resist adjustment values A and B are corrected by using the above formulas (1) and (2), but the respective resist adjustment values A and B are calculated by using other formulas. It may be corrected. Alternatively, instead of the above equation (1), the internal temperature t1, t2 (° C.) is referred to by referring to a data table in which the internal temperature t1, t2 (° C.) is associated with the correction amount of the registration adjustment value A. The registration adjustment value A is corrected by the correction amount to obtain the registration adjustment value B, or a data table in which the operation rates a and b are associated with the correction amount of the registration adjustment value B instead of the above equation (2). The registration adjustment value C may be obtained by correcting the registration adjustment value B with a correction amount corresponding to the operating rates a and b.

  Further, in the above embodiment, the toner images of the respective colors on the respective photosensitive drums 13 are transferred onto the intermediate transfer belt 21, and the toner images of the respective colors on the intermediate transfer belt 21 are transferred to the recording paper. The present invention can also be applied to a configuration in which the toner images of the respective colors on the respective photosensitive drums 13 are directly transferred onto the recording paper.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. It is understood.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 11 Optical scanning device (LSU, image formation process part)
12 Development device (image forming process section)
13 Photosensitive drum (image carrier, image forming process section)
14 Drum cleaning device (image forming process part)
15 Charger (Image creation process part)
16 Intermediate transfer belt device (image forming process section)
17 Fixing device 18 Paper feed cassette 19 Paper discharge tray 41 Image reading device 42 Document transport device 71 Main control unit (registration correction unit, operating rate calculation unit, registration correction calculation unit)
72 Printing unit 73 Image processing unit 74 Input operation unit 75 Memory (storage unit)
76 Registration Sensor 82 Laser Diode 83 Polygon Mirror 84 Polygon Motor 85 Temperature Sensor (Temperature Detection Unit)

Claims (5)

Each latent image is written on a plurality of image carriers by a laser beam of an optical scanning device, the latent image of each image carrier is developed, and a visible image of each color is formed on each image carrier, An image forming process unit that forms a visible color image by transferring the visible image of each color on each image carrier onto a recording medium, and resists the deviation of the test pattern of each color in the visible color image An image forming apparatus comprising: a registration correction unit that detects a position of a visible image of each color that is detected as an adjustment value and that is transferred based on the registration adjustment value;
A temperature detector for detecting the temperature of the optical scanning device;
An operation rate calculating unit for calculating an operation rate of the image forming process unit;
Based on the change in the operating ratio due to the change and the operating rate calculating unit of the temperature by the temperature detecting unit, and a registration correction arithmetic unit for correcting the registration adjustment value,
The temperature detection unit detects a change in temperature in a resist process for measuring the resist adjustment value A by forming a test pattern for each color and a printing process for forming a visible image of the color,
The operating rate calculation unit calculates a change in operating rate between the resist process and the printing process,
The resist correction calculation unit obtains a resist adjustment value B by correcting the resist adjustment value A measured in the resist process based on a change in temperature detected by the temperature detection unit, and further, by the operating rate calculation unit Based on the calculated change in the operating rate, the resist adjustment value B is corrected to obtain the registration adjustment value C. As the change in the operating rate becomes smaller, the resist adjustment value C becomes the resist adjustment value B. An image forming apparatus , wherein the correction is performed so as to be closer to . The image forming apparatus according to claim 1,
The said operation rate calculating part calculates | requires the operation rate of the said image creation process part for every predetermined time, and calculates | requires the change of the operation rate of each predetermined time. The image forming apparatus according to claim 1,
The operating rate calculating unit, the said imaging process unit of the predetermined time rate of operation when forming the respective colors of the test pattern, the imaging process unit when said forming a visible image of each color An image forming apparatus characterized in that a difference from an operation rate of the predetermined time is obtained as a change in an operation rate of the image forming process unit. An image forming apparatus according to any one of claims 1 to 3 , wherein
Wherein the temperature change due to the temperature detection unit, wherein the temperature detected when forming the respective colors of the test pattern, wherein a difference between the temperature detected when forming the visible images of the respective colors An image forming apparatus. An image forming apparatus according to any one of claims 1 to 4 , wherein
The optical scanning device includes a polygon mirror that is driven to rotate, the laser beam is reflected by the polygon mirror and scanned in the main scanning direction,
The image forming apparatus according to claim 1, wherein the operation rate calculation unit obtains an operation rate of a drive motor that rotationally drives the polygon mirror as an operation rate of the image forming process unit.

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