JP2012133215A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the prediction accuracy of the amount of the displacement of an image on an image carrier using temperature.SOLUTION: A color shift amount of an image on an image carrier formed by a plurality of image formation units is detected using a detection pattern image (S105). Based on the detected color shift amount, the displacement of the image formed by the plurality of image formation units is corrected (S107). Then, based on the amount of change in temperature after correcting the color shift according to the detected color shift amount using the color shift detection pattern image, the color shift amount of the image on the image carrier formed by the plurality of image formation units is predicted (S115). Based on the predicted color shift amount, the color shift amount of the image formed by the plurality of image formation units is corrected (117).

Description

  The present invention detects the amount of positional deviation of an image formed by a plurality of image forming units on an image carrier and corrects the positional deviation of the image formed by the plurality of image forming units according to the amount of positional deviation. The present invention relates to an image forming apparatus.

  An electrophotographic color image forming apparatus has a plurality of image forming units for speeding up, and sequentially transfers images of different colors onto a recording material held on a conveyance belt or onto an intermediate transfer belt. There is a method to do. A problem with this method is that distortion and deformation occur in the lenses and mirrors in the image forming unit due to temperature changes in the machine, and color misregistration occurs when images of each color are superimposed. To solve this problem, a color misregistration detection pattern is formed on the conveyance belt or intermediate transfer belt at a predetermined timing, and the color misregistration amount is calculated by reading the color misregistration detection pattern with a sensor. A technique for correcting color misregistration by controlling the color is known.

  However, in this color misregistration correction method, it is necessary to form a color misregistration detection pattern at an appropriate time interval or for every number of printed sheets. This results in downtime of the image forming apparatus, leading to a decrease in image formation productivity. It was. In order to solve this problem, a prediction type color corresponding to the temperature is calculated in which the correction amount is calculated by referring to the correction table in which the apparatus internal temperature and the color misregistration amount are associated one by one, and the image formation timing is corrected. Deviation correction has been proposed (see Patent Document 1). Accordingly, the color misregistration detection pattern is not formed or the frequency of forming the color misregistration detection pattern can be reduced, so that the occurrence of downtime can be suppressed only by temperature detection.

JP-A-3-293679

  However, the part deformation method is non-linear with respect to the temperature, and the temperature and the color misregistration amount do not always correspond one-to-one. The relationship between the temperature change and the color misregistration amount is also nonlinear. Even if the temperature shows the same value, the color misregistration amount at that time is not always the same amount. Therefore, when the color misregistration amount is uniquely predicted based on the detected temperature, there is a possibility that an error from the actual color misregistration amount becomes large.

  In order to solve the above problems, an image forming apparatus according to the present invention includes a plurality of image forming units that form an image on an image carrier, and an image formed by the plurality of image forming units on the image carrier. A misregistration amount detecting means for detecting a misregistration amount at the position, a correction means for correcting misregistration of images formed by the plurality of image forming means based on the misregistration amounts detected by the detection means, Based on the amount of change in the temperature detected by the temperature detecting means after the temperature detecting means for detecting the temperature and the correction means correct according to the positional deviation amount detected by the positional deviation amount detecting means, Misregistration amount prediction means for predicting the misregistration amount of the image formed by a plurality of image forming means on the image carrier, and the correction means is predicted by the misregistration amount prediction means. Said position And correcting the positional deviation of an image formed by the plurality of image forming means on the basis of which the amount.

  According to the present invention, it is possible to improve the accuracy of prediction of the amount of image displacement on the image carrier.

1 is a cross-sectional view of an image forming apparatus according to an embodiment. FIG. 3 is a control block diagram of the image forming apparatus. The figure of a color shift prediction table and a prediction value correction table. 5 is a flowchart of color misregistration amount detection processing and color misregistration amount prediction processing. FIG. 4 is a diagram illustrating a color misregistration detection pattern image formed on an intermediate transfer belt. 10 is a flowchart of color misregistration amount detection processing and color misregistration amount prediction processing in the second embodiment.

  FIG. 1 is a cross-sectional view of an image forming apparatus 1 according to the present embodiment. 2a to 2d are photosensitive drums, and 3a to 3d are laser scanning units. Reference numerals 4a to 4d denote developing devices, and the photosensitive drum, the laser scanning unit, and the developing device constitute an image forming unit for each color. 5 is an intermediate transfer belt as an image carrier, 6 is a secondary transfer roller, 7 is a fixing roller, 11 is a registration detection sensor for detecting a color misregistration detection pattern image formed on the intermediate transfer belt, and 12 is in the apparatus. It is the temperature detection sensor installed in. The registration detection sensors 11 are provided at positions corresponding to both sides of the intermediate transfer belt 5.

  In the image forming apparatus 1, electrostatic latent images are formed on the photosensitive drums 2a to 2d for the respective colors by the respective laser scanning units 3a to 3d using a semiconductor laser as a light source. Development is performed by 4a to 4d. The toner images of the respective colors developed on the photosensitive drums 2a to 2d are primarily transferred while being superimposed on the intermediate transfer belt 5. That is, a plurality of image forming units form images on the image carrier in an overlapping manner. The four-color toner images on the intermediate transfer belt are transferred to a sheet (recording paper) by the secondary transfer roller 6 and fixed on the recording paper by a heat fixing device including a fixing roller 7 and the like.

  Further, BD sensors 31a to 31d (not shown in FIG. 1) are provided in the laser scanning units 3a to 3d, respectively, to detect the passage of laser light immediately before scanning the photosensitive drums 2a to 2d. The BD signal, which is the synchronization signal of, is generated. Based on the BD signal, an image formation timing control unit 14 to be described later generates a main-running synchronization signal, and controls the main scanning writing timing of each of the laser scanning units 3a to 3d.

  The image forming apparatus 1 forms color misregistration detection pattern images on the photosensitive drums 2 a to 2 d, transfers the color misregistration detection pattern images of the respective colors onto the intermediate transfer belt 5, and detects color misregistration detection pattern images on the intermediate transfer belt 5. Is detected by the registration sensor 11 to detect the color misregistration amount. The image forming apparatus 1 performs color misregistration correction, that is, auto registration by correcting the image writing timing in accordance with the detected color misregistration amount.

  FIG. 2 is a control block diagram of the image forming apparatus. In FIG. 2, reference numeral 13 denotes a memory that stores in advance temperature data detected by the temperature detection sensor 12, a color shift prediction table, and a predicted value correction table, which will be described later. A CPU 10 controls the operation of the image forming apparatus according to the present invention. Further, the CPU 10 calculates the correction amount of the image formation timing based on the reading value of the registration detection sensor 11. Further, the CPU 10 further calculates the correction amount of the image formation timing based on the temperature detected by the temperature detection sensor 12 and the table in the memory 13. Reference numeral 14 denotes an image formation timing control unit. The image forming timing control unit 14 determines the main scanning writing timing in the laser scanning units 3a to 3d based on the correction amount of the image forming timing calculated by the CPU 10 and the BD signals generated by the above-described BD sensors 31a to 31d. By performing the control, an image forming position correcting operation for each color is executed.

FIG. 3 is a diagram of a color misregistration prediction table and a prediction value correction table in the present embodiment. Such table information is stored in the memory 13. The color misregistration prediction table in FIG. 3A shows the relative change amount (T−T ₀ ) of the temperature in the apparatus after the color misregistration correction using the color misregistration detection pattern image, and the color misregistration corresponding to this. This shows the relationship of the amount Δy. Here, T is a temperature when color misregistration prediction is performed, and T ₀ is a temperature when color misregistration correction using a color misregistration detection pattern image is performed. This table is obtained by measurement at the product design stage. The predicted value correction table in FIG. 3B shows the relationship between the temperature change amount (T−T ′) per predetermined time and the corresponding correction value ε. Here, T is a temperature when color misregistration prediction is performed, and T ′ is a temperature when color misregistration prediction is performed last time. By adding this correction value to the reference value of the color misregistration prediction table, a color misregistration prediction error due to a difference in temperature change is reduced. The difference in temperature change is, for example, a difference in the degree of temperature change per unit time. The difference in temperature change appears in the difference in the degree of component deformation in the apparatus.

  FIG. 4 is a flowchart of the color misregistration amount detection process and the color misregistration amount prediction process. First, after powering on the image forming apparatus, the CPU 10 goes through a standby state (S101), and starts a print job in response to the input of a print job (S102) (S103). Next, the CPU 10 determines whether it is auto registration execution timing (S104). Here, the auto registration execution timing is, for example, when returning from the sleep mode or when the number of printed sheets reaches a predetermined value, and can be arbitrarily set. If it is determined in step S104 that the auto registration execution timing is reached, color misregistration correction is performed by the auto registration operation described below.

  The CPU 10 forms a color misregistration detection pattern image on the intermediate transfer belt 5 and detects the color misregistration amount based on the output of the registration detection sensor that has read the color misregistration detection pattern image on the intermediate transfer belt 5 (S105). . FIG. 5 is a diagram showing a color misregistration detection pattern image formed on the intermediate transfer belt. 20a to 20d and 21a to 21d are color misregistration detection pattern images for detecting the color misregistration amount in the paper conveyance direction, and 22a to 22d and 23a to 23d are color misregistration in the main scanning direction orthogonal to the paper conveyance direction. It is a color misregistration detection pattern image of each color for detecting the amount. By sampling these patterns, the amount of color misregistration of other colors with respect to a predetermined reference color is detected. Next, the CPU 10 calculates a color misregistration correction value for each color excluding the reference color from the detected color misregistration amount between each color (S106). Next, the CPU 10 calculates an image formation timing correction amount based on the calculated color misregistration correction amount, and causes the image formation timing control unit 14 to perform image formation timing correction (S107). Steps S105 to S107 described above are auto registration.

Following the auto registration, the CPU 10 detects the in-apparatus temperature T, stores it in the memory 13 as T ₀ = T (S108), and determines whether the print job is completed (S109). If it is determined that the print job is completed, the standby state is entered (S110), and the color misregistration correction operation is terminated. If it is determined in step S108 that the print job has not ended, the process returns to step S104 to determine whether it is the auto registration execution timing.

Next, a case where the auto registration execution timing is not determined in S104 will be described. When it is not the auto registration execution timing in step S104, that is, between the time when auto registration is executed and the time when the next auto registration is executed, the process waits until the prediction correction execution timing is reached (S111). Here, the prediction correction execution timing is when a predetermined time has elapsed since the previous auto registration or the previous prediction correction execution. When the prediction correction execution timing comes in step S111, the apparatus internal temperature T is detected (S112), and by referring to the color misregistration prediction table of FIG. The predicted color shift amount Δy from the time of execution of auto registration is acquired from the temperature difference (change amount of detected temperature) ΔT = T−T ₀ (S113). For example, when the temperature T ₀ at the time of auto registration execution is 30 degrees and the temperature T at the time of prediction correction execution is 33 degrees, the reference value of the color misregistration prediction table is Δy = 70 μm.

Next, the CPU 10 refers to the prediction value correction table of FIG. 3B stored in the memory 13, so that the temperature difference Δt = T−T from the time of the previous prediction correction or the previous auto registration execution time. The correction amount ε is acquired from '(S114). Here, T ′ is a temperature detection value at the time of the previous prediction correction. For example, when the temperature T when the prediction correction is performed is 33 degrees and the temperature T ′ when the previous prediction correction is performed is 32 degrees, the reference value of the prediction value correction table is ε = 3 μm. Here, TT ′ represents the amount of temperature change per unit time since the time interval of prediction correction is constant. Next, the CPU 10 calculates a predicted color shift amount Δy ′ obtained by adding the obtained color shift predicted value Δy and the predicted value correction amount ε (S115). This predicted color misregistration amount is a value obtained by predicting the color misregistration amount from the time of execution of auto registration. For example, in the above example (T = 33, T ₀ = 30, T ′ = 32), Δy ′ = 70 + 3 = 73 μm is calculated.

  Based on the color misregistration prediction amount Δy ′ thus obtained, the CPU 10 calculates the image formation timing correction amount, and causes the image formation timing control unit 14 to perform image formation timing correction (S116). Next, the temperature T detected in S108 is stored in the memory 13 as the temperature T 'at the time of prediction correction execution (S117), and the process returns to step S109 to determine whether or not the print job is completed. If it is determined that the print job is completed, the standby state is entered (S110), and the color misregistration correction operation is terminated.

  As described above, by performing error correction using the time change rate of temperature, it is possible to reduce color misregistration prediction errors caused by differences in temperature change speed and improve color misregistration correction accuracy.

  In FIG. 1, the installation position of the temperature detection sensor 12 is set in the vicinity of the intermediate transfer belt 5, but the position and the number of installation of the temperature detection sensors are not particularly limited. The temperature detection position may be a position where a temperature change correlates with a change in color misregistration amount.

  In this embodiment, the example of performing the color misregistration correction operation in the main scanning direction has been described. However, the same table is also provided and referred to for color misregistration in the sub scanning direction, and color misregistration such as magnification and bending. A similar correction operation can be performed.

  Next, a second embodiment will be described using FIG. 2 and FIG. The configuration of the apparatus is the same as that of FIG. 2 shown in the first embodiment. In the first embodiment, the predicted color misregistration amount is calculated using a table, but in the second embodiment, the predicted color misregistration amount is obtained using an arithmetic expression that predicts the color misregistration amount according to the detected temperature. An arithmetic expression that approximates the relationship between the temperature and the color misregistration amount in the color misregistration prediction table or the prediction value correction table in the first embodiment is held in the memory 13, and the predicted color misregistration amount is calculated using the arithmetic expression.

FIG. 6 is a flowchart of color misregistration amount detection processing and color misregistration amount prediction processing according to the second embodiment. Steps S201 to S212 are the same as steps S101 to S112 in the first embodiment, and a description thereof will be omitted. After step 212, the CPU 10 uses the detected temperature T, the temperature T0 at the time of auto registration execution _, and the temperature T ′ at the previous correction,
Δy ′ = α ₁ · (T−T ₀ ) + α ₂ · (T−T ′)
As a result, a color misregistration prediction amount Δy ′ is calculated (S213). Here, α ₁ · (T−T ₀ ) corresponds to the reference value Δy according to the color misregistration prediction table in the first embodiment, and α ₂ · (T−T ′) corresponds to the reference value ε of the prediction value correction table. . The coefficients α ₁ and α ₂ store data (Δy ′, T−T ₀ , T−T ′) corresponding to the color shift amount, the color shift prediction table, and the predicted value correction table at the product design stage. Is a value calculated by substituting into the above equation, for example, by linear approximation, and is stored in the memory 13.

  Next, as in the first embodiment, the CPU 10 performs color misregistration correction based on the predicted color misregistration amount (S214), and stores the temperature T detected in step S212 in the memory 13 as T ′ at the time of executing the predictive correction. (S215), the process returns to step S209, and it is determined whether or not the print job is completed.

  Here, the primary approximate expression is given as an example of the arithmetic expression, but other suitable approximate expressions such as a quadratic expression may be used. In addition, by using an approximate expression, only a coefficient such as α needs to be held in the memory, so that a smaller amount of memory is required compared to the first embodiment in which a table needs to be held.

10 CPU
DESCRIPTION OF SYMBOLS 11 Registration detection sensor 12 Temperature detection sensor 13 Memory 14 Image formation timing control part

Claims (3)

A plurality of image forming means for superimposing and forming an image on the image carrier;
A misregistration amount detecting means for detecting misregistration amounts on the image carrier of images formed by the plurality of image forming means;
A correction unit that corrects a positional deviation of images formed by the plurality of image forming units based on the positional deviation amount detected by the detection unit;
Temperature detection means for detecting temperature;
Formed by the plurality of image forming units based on the amount of change in the temperature detected by the temperature detection unit after the correction unit corrects the position shift amount detected by the position shift amount detection unit. A misregistration amount predicting means for predicting a misregistration amount of the image on the image carrier;
Have
The image forming apparatus according to claim 1, wherein the correction unit corrects a positional deviation of an image formed by the plurality of image forming units based on the positional deviation amount predicted by the positional deviation amount prediction unit.   The image forming apparatus according to claim 1, wherein the plurality of image forming units form images of different colors, and the detection unit detects a color shift amount.   The image forming apparatus according to claim 1, wherein the detecting unit detects the positional deviation amount by detecting a plurality of pattern images respectively formed by the plurality of image forming units.

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