JP2010014970A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which prevents its own downtime from being wastefully long. <P>SOLUTION: A determination part 701 determines toner pattern-detecting conditions (for example, a rotational speed of an intermediate transfer belt 16, a speed for forming a toner pattern on the intermediate transfer belt 16, and a sampling frequency for obtaining a result of detection of a toner pattern by a reflection-type sensor 24) on the basis of the amplitude of an output voltage from the reflection-type sensor 24 which detects reflection light from the intermediate belt 16 before the toner pattern is formed. A detection-controlling part 702 detects reflection light from a toner pattern by meas of the reflection-type sensor 24 according to the determined detecting conditions. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus.

  In an image forming apparatus using an electrophotographic system such as a laser printer, the density and gradation of an image fluctuate due to the influence of environmental changes such as temperature and humidity at the installation site and changes over time. Therefore, in a conventional image forming apparatus, a toner pattern for controlling image forming conditions such as image density, gradation, and positional deviation is formed on an endless belt at a predetermined timing, and reflection from the formed toner pattern is performed. It is known to control image forming conditions based on an output voltage from a sensor that detects light (hereinafter referred to as a reflective sensor).

  By the way, the detection accuracy of the toner pattern largely depends on the variation in the distance between the endless belt and the reflective sensor. For this reason, the distance between the endless belt and the reflective sensor must always be kept constant. However, since the endless belt is always in operation when detecting the toner pattern, the distance between the endless belt and the reflective sensor changes due to any unstable behavior such as distortion or undulation of the endless belt. There was a problem that the pattern detection accuracy deteriorated. Further, depending on the directivity and mounting accuracy of the light emitting element and the light receiving element included in the reflective sensor, the output voltage of the toner pattern may greatly change even if the endless belt being operated is slightly distorted or wavy. Furthermore, as the rotational speed of the endless belt increases, unstable behavior such as distortion and undulation of the endless belt tends to increase.

  In order to solve such a problem, an image forming apparatus (see Patent Document 1) that suppresses unstable behavior such as distortion and undulation of the endless belt by slowing the rotation speed of the endless belt is disclosed. In the image forming apparatus according to Patent Document 1, the density detection accuracy is improved by changing the rotation speed of the endless belt between normal image formation and toner pattern detection.

JP 2003-131538 A

  However, the technique described in Patent Document 1 has a problem that the downtime of the image forming apparatus becomes long because the rotation speed of the endless belt is slow.

  The present invention has been made in view of the above, and an object of the present invention is to provide an image forming apparatus that can prevent the downtime of the image forming apparatus from becoming unnecessarily long.

  In order to solve the above-described problems and achieve the object, the invention according to claim 1 is based on an output voltage from a sensor that detects reflected light from a toner pattern for controlling image forming conditions formed on a rotating body. An image forming apparatus for controlling image forming conditions, wherein the toner pattern detection condition is determined based on an amplitude of an output voltage from the sensor that detects reflected light from the rotating body before forming the toner pattern. A determining unit configured to determine; and a detection control unit configured to detect reflected light from the toner pattern by the sensor according to the determined detection condition.

  The invention according to claim 2 is the invention according to claim 1, wherein the determining means determines the detection condition based on an amplitude of an output voltage from the sensor for one rotation of the rotating body. And

  According to a third aspect of the present invention, in the first or second aspect of the present invention, a threshold range that is a threshold range of an amplitude of the output voltage from the sensor, and an output voltage from the sensor within the threshold range. Storage means for storing the detection condition when the amplitude falls within the association is further provided, and the determination unit is stored in association with the threshold range within which the amplitude of the output voltage from the sensor falls. The detection condition is determined as the detection condition when detecting reflected light from the toner pattern.

  Further, the invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein the control means further includes a case where an average value and an amplitude of the output voltage from the sensor exceed a predetermined value, The detection of reflected light from the toner pattern by the sensor is stopped.

  The invention according to a fifth aspect is the invention according to any one of the first to fourth aspects, wherein the detection conditions include a rotational speed of the rotating body, a forming speed of the toner pattern on the rotating body, and the A frequency at which the output voltage from the sensor that detects the reflected light from the toner pattern is sampled.

  According to the present invention, it is possible to execute a series of processes related to control of image forming conditions in accordance with toner pattern detection conditions according to the strength of any unstable behavior such as endless belt distortion or undulation. There is an effect that it is possible to prevent the downtime of the forming apparatus from becoming unnecessarily long.

  Exemplary embodiments of an image forming apparatus according to the present invention will be explained below in detail with reference to the accompanying drawings. In the following embodiment, an example in which the image forming apparatus of the present invention is applied to an electrophotographic color printer is shown, but the present invention is not limited to this, and a plurality of copying machines, facsimile machines, copying machines, facsimile machines, printers, etc. The present invention can also be applied to a multifunction machine having the above functions.

  First, a schematic configuration of an image forming unit mounted on a color printer according to the present embodiment will be described with reference to FIG. FIG. 1 is a diagram illustrating an example of an image forming unit installed in the color printer according to the present embodiment. The image forming unit 1 shown in FIG. 1 is a tandem image forming unit that employs an intermediate transfer member.

  The image forming unit 1 includes four photosensitive drums 10Y, 10M, 10C, and 10K, and a plurality of developing devices 11Y, 11M, and 11D that respectively develop the latent images formed on the photosensitive drums into different color toner images. 11C and 11K, and an intermediate transfer belt 16 (rotating body according to the present invention), which is an endless belt that rotates in the direction of arrow A where toner images of different colors are primarily transferred in a superimposed state. . Hereinafter, when it is not necessary to distinguish between the photosensitive drums 10Y, 10M, 10C, and 10K, they are simply referred to as the photosensitive drum 10. Hereinafter, the developing devices 11Y, 11M, 11C, and 11K are simply referred to as the developing device 11 when it is not necessary to distinguish them.

  In the present embodiment, on the upper side of the intermediate transfer belt 16, along the arrow A direction of the intermediate transfer belt 16, the four above-described photosensitive drums 10 for each color of black, cyan, magenta, and yellow are provided. They are arranged in parallel. Around the photosensitive drum 10, the charging devices 12Y, 12M, 12C and 12K, the developing device 11 described above, the primary transfer roller 14 constituting the primary transfer device, the cleaning devices 13Y, 13M, 13C and 13K, Are arranged respectively. Hereinafter, when it is not necessary to distinguish between the charging devices 12Y, 12M, 12C, and 12K, they are simply referred to as the charging device 12. Hereinafter, when it is not necessary to distinguish between the cleaning devices 13Y, 13M, 13C, and 13K, they are simply referred to as the cleaning device 13.

  The photosensitive drum 10 is rotationally driven in the direction of arrow B. At this time, the charging device 12 charges the surface of the photosensitive drum 10 to a predetermined polarity. Next, the exposure device 15 irradiates the charged surface of the photosensitive drum 10 charged with a predetermined polarity by the charging device 12 with laser light. As a result, an electrostatic latent image is formed on the photosensitive drum 10, and the electrostatic latent image is visualized as a toner image of each color by the developing device 11.

  Here, primary transfer rollers 14 </ b> Y, 14 </ b> M, 14 </ b> C, and 14 </ b> K are opposed to each photosensitive drum 10, and an intermediate transfer belt 16 is interposed between each primary transfer roller 14 and the photosensitive drum 10. It is designed to rotate in a sandwiched state. The intermediate transfer belt 16 is supported by two axes of a driving roller 17 and a tension roller 19. The intermediate transfer belt 16 may be stretched by two or more rollers. However, in order to reduce the size of the image forming unit 1 as much as possible, the intermediate transfer belt 16 is stretched by two axes to suppress the height of the image forming unit 1. ing. Hereinafter, when it is not necessary to distinguish the primary transfer rollers 14Y, 14M, 14C, and 14K, they are simply referred to as the primary transfer roller 14.

  The toner images visualized on the respective photosensitive drums 10 are transferred onto the surface of the intermediate transfer belt 16 by the action of the primary transfer roller 14. In this manner, the black, cyan, magenta, and yellow toner images visualized on the respective photoconductive drums 10 are transferred onto the intermediate transfer belt 16 in a state of being sequentially and accurately superimposed, and a full color composition is performed. A color image is formed. The cleaning device 13 removes toner remaining on the surface of the photosensitive drum 10 after the toner image is transferred to the intermediate transfer belt 16.

  The paper feeding unit 21 feeds the transfer paper P, which is a recording medium, to the image forming unit 1. The transfer paper P fed from the paper feed unit 21 to the image forming unit 1 is sent between the driving roller 17 and the secondary transfer roller 18 at a predetermined timing by the rotation of the registration roller pair 22. The driving roller 17 (secondary transfer counter roller) and the secondary transfer roller 18 are disposed to face each other with the intermediate transfer belt 16 interposed therebetween. When the transfer paper P is fed between the driving roller 17 and the secondary transfer roller 18, the composite color image carried on the intermediate transfer belt 16 is collectively put on the transfer paper P by the action of the secondary transfer roller 18. Is transcribed. The toner image transferred onto the transfer paper P is fixed by heat and pressure by the fixing device 23 and discharged onto a paper discharge tray (not shown). The residual transfer toner that adheres to the surface of the intermediate transfer belt 16 after the toner image is transferred to the transfer paper P is removed by the cleaning device 20.

  In the image forming unit 1, a reflective sensor 24 (sensor according to the present invention) is disposed in the main scanning direction at a predetermined distance from the intermediate transfer belt 16. The reflection type sensor 24 irradiates the toner pattern for controlling image forming conditions formed on the intermediate transfer belt 16 rotating in the direction of arrow A, and detects the reflected light.

  The color printer according to the present embodiment controls the image forming conditions based on the output voltage from the reflective sensor 24 that detects the reflected light from the toner pattern. Specifically, in a color printer equipped with the tandem image forming unit 1, mounting errors of each unit included in the image forming unit 1, adjustment errors / distortions / environment of the exposure device 15, changes with time, changes in the photosensitive drum 10 Color misregistration occurs in the toner image transferred to the transfer paper P due to rotation unevenness, unevenness of conveyance of the image carrier (intermediate transfer belt 16) / change due to disturbance of the transfer paper, and the like. Therefore, in a color printer equipped with the tandem image forming unit 1, a toner pattern to be a mark of each color is formed on the image carrier, and the position of the toner pattern of each color is detected by the optical reflective sensor 24. Then, the color misregistration amount of each color is calculated from the detected position, and the image forming conditions such as the exposure timing are controlled.

  Further, a color printer equipped with the tandem image forming unit 1 is required to appropriately stabilize the image density of each color in order to obtain a high-quality full-color image. Therefore, in a color printer equipped with the tandem image forming unit 1, a toner pattern serving as a reference for density is formed on the intermediate transfer belt 16, and the density of this toner pattern is detected by an optical reflective sensor 24. Based on the detected density of each color, image forming conditions that affect the density such as charging potential, exposure intensity, development bias voltage, transfer voltage, and toner replenishment amount are controlled.

  Here, the toner pattern formed on the intermediate transfer belt 16 according to the present embodiment, the reflective sensor 24 for detecting the toner pattern, and the output voltage from the reflective sensor 24 for detecting the toner pattern are shown in FIGS. Will be described in detail with reference to FIG. FIG. 2 is a diagram illustrating an example of a toner pattern formed on the intermediate transfer belt and a position of a reflective sensor that detects the toner pattern. FIG. 3 is a diagram illustrating an example of the configuration of the reflective sensor.

  As shown in FIG. 2, in the present embodiment, density control patterns (Y1 to Y10, K1 to K10, C1 to C10, M1 to M10) and color misregistration control patterns (Y20, K20, C20, M20, Y21). , K21, C21, M21) is formed on the intermediate transfer belt 16. The density control pattern and the color misregistration control pattern move in the direction of arrow A (moving direction), and when each pattern passes directly below the reflective sensors 24a, 24b, 24c, the reflective sensors 24a, 24b, 24c is detected in parallel.

  The density control pattern is formed by arranging patches Y1 to Y10, K1 to K10, C1 to C10, and M1 to M10 representing the single-color gradations of yellow, black, cyan, and magenta in the moving direction. The control of each color uses a preset condition. For example, in the case of a patch representing a yellow gradation, Y1 = density 10%,. . . , Y10 = density 100%. The density control pattern is formed at the center of the intermediate transfer belt 16. Then, the density control pattern is detected by a reflective sensor 24 b that is disposed opposite to the center of the intermediate transfer belt 16.

  The reflective sensor 24b detects regular reflection light and diffuse reflection light from the density control pattern. As shown in FIG. 3A, the reflective sensor 24 b is disposed toward the intermediate transfer belt 16 and detects a density control pattern formed on the surface of the intermediate transfer belt 16. In the present embodiment, the reflective sensor 24b includes a light emitting element 301 such as an infrared light emitting diode, light receiving elements 302 and 303 such as a phototransistor / photodiode, and a holder 304 that accommodates these elements.

  Specifically, the reflection type sensor 24 b detects regular reflection light from the density control pattern by the light receiving element 302, and detects diffuse reflection light from the density control pattern by the light receiving element 303. Thereby, the reflection type sensor 24b can detect the density of black and color from low density to high density. In the present embodiment, it is assumed that the reflective sensor 24b outputs the output voltage of the light receiving elements 302 and 303.

  FIG. 4 is a diagram showing the output voltage of the reflective sensor that detects the density control pattern. As shown in FIG. 4, the output voltage of the reflective sensor 24b that has detected the density control pattern decreases sequentially as the gray level increases. The color printer according to the present embodiment converts the output voltage output from the reflective sensor 24b into a density based on a preset relationship between the output voltage and the density. The color printer according to the present embodiment controls the image forming conditions that affect the density based on the density of each color gradation obtained from the density control pattern.

  On the other hand, in the color misregistration control pattern, straight lines Y20, K20, C20, M20 and diagonal lines Y21, K21, C21, M21 of yellow, black, cyan, and magenta are formed side by side in the movement direction. The color misregistration control pattern is formed near both ends of the intermediate transfer belt 16. The color misregistration control pattern is detected by reflective sensors 24 a and 24 c that are installed facing both ends of the intermediate transfer belt 16.

  The reflection sensors 24a and 24c detect only regular reflection light from the color misregistration control pattern. As shown in FIG. 3B, the reflection sensors 24 a and 24 c are arranged toward the intermediate transfer belt 16 and detect a color misregistration control pattern formed on the surface of the intermediate transfer belt 16. In the present embodiment, the reflective sensors 24a and 24c include a light emitting element 301, a light receiving element 302, and a holder 304 that accommodates these elements.

  Specifically, the reflection sensors 24 a and 24 c detect only regular reflection light from the color misregistration control pattern by the light receiving element 302. In the present embodiment, the reflection sensors 24a and 24c output the output voltage of the light receiving element 302.

  FIG. 5 is a diagram illustrating the output voltage of the reflective sensor that detects the color misregistration control pattern. As shown in FIG. 5, the output voltage of the reflection type sensors 24a and 24c that have detected the color misregistration control pattern is slightly deteriorated in the black reflectance, so that the output of the black (K20, K21) color misregistration control pattern is performed. The voltage is slightly lower than the output voltage of the color misregistration control pattern for other colors. Further, the output voltages of the color misregistration control patterns for the colors other than black (Y20, Y21, C20, C21, M20, M21) have substantially constant values. When the color printer according to the present embodiment calculates the amount of color misregistration, the rise of the output voltage of the reflection type sensors 24a and 24c that detect the color misregistration control pattern for each color is determined with reference to a predetermined threshold value. The center value obtained by adding the falling intersection and the rising intersection and dividing by two is obtained. Next, the color printer according to the present embodiment uses the center value obtained for the color misregistration control pattern for each color and uses the center value for black as a reference color to move in the moving direction according to the positional relationship between the straight lines for each color of yellow, cyan, and magenta. The amount of misregistration in the main scanning direction is calculated from the positional relationship between the straight lines and the diagonal lines of the colors yellow, cyan, and magenta. The color printer according to this embodiment controls image forming conditions such as writing timing based on the calculated color misregistration amount. Hereinafter, when it is not necessary to distinguish between the reflective sensors 24a, 24b, and 24c, they are simply referred to as the reflective sensor 24. Further, when it is not necessary to distinguish between the density control pattern and the color misregistration control pattern, they are simply referred to as a toner pattern.

  However, when an unstable behavior such as distortion or undulation of the intermediate transfer belt 16 occurs, the distance and angle between the intermediate transfer belt 16 and the reflective sensor 24 fluctuate. Therefore, the reflective sensor that detects the toner pattern. The output voltage from 24 varies greatly. In addition, the output voltage from the reflective sensor 24 may vary greatly depending on the directivity and mounting accuracy of the light emitting element 301 and the light receiving elements 302 and 303 included in the reflective sensor 24.

  Further, the unstable behavior of the intermediate transfer belt 16 changes depending on the rotation speed of the intermediate transfer belt 16. Specifically, the unstable behavior of the intermediate transfer belt 16 tends to increase when the rotation speed of the intermediate transfer belt 16 is high, and tends to weaken when the rotation speed of the intermediate transfer belt 16 is low.

  Therefore, the color printer according to the present embodiment has a rotational speed of the intermediate transfer belt 16, a toner pattern forming speed on the intermediate transfer belt 16, and an output voltage from the reflective sensor 24 that detects reflected light from the toner pattern. The toner pattern is detected by determining the condition for detecting the toner pattern (hereinafter referred to as the detection condition) such as the frequency for acquiring the toner (hereinafter referred to as the sampling frequency) and detecting the toner pattern according to the determined detection condition. The occurrence of uneasy behavior of the intermediate transfer belt 16 during the operation is prevented. The unstable behavior of the intermediate transfer belt 16 generally appears significantly in the output voltage from the sensor that detects specularly reflected light, and does not affect the output voltage from the sensor that detects diffused light. Therefore, in the present embodiment, the reflection sensors 24a, 24b, and 24c output the output voltage of the light receiving element 302 when detecting the unstable behavior of the intermediate transfer belt 16.

  Hereinafter, a main configuration of the color printer according to the present embodiment that executes a series of processes related to control of image forming conditions including a determination process of detection conditions and a sequence of processes related to control of image forming conditions will be described.

  First, the main configuration of the color printer according to the present embodiment will be described with reference to FIG. FIG. 6 is a diagram showing a main configuration of the color printer according to the present embodiment.

  A color printer 600 according to this embodiment includes an image forming unit 1, a CPU (Central Processing Unit) 601, a ROM (Read Only Memory) 602, a RAM (Random Access Memory) 603, and an I / O (Input / Output) unit 604. , A writing unit 605, and an I / F unit 606.

  The RAM 603 includes various necessary parameters and a work area area for overall control of the color printer 600.

  The I / F unit 606 is connected to an external device such as a wired LAN, a wireless LAN, or a USB, and receives image data from the external device.

  The writing unit 605 stores, in the RAM 603, an image digital signal obtained by separating image signals of each color Y, M, C, and K included in image data, toner patterns, and the like received from an external device via the I / F unit 606. The image is transmitted to the exposure device 15 according to the stored color misregistration parameter and toner density.

  The I / O unit 604 receives the output voltage from the reflective sensor 24 that has detected the toner pattern and the output voltage from the reflective sensor 24 that has detected the reflected light from the intermediate transfer belt 16 before forming the toner pattern. The output voltage is converted into a digital signal by an AD converter.

  The ROM 602 implements the storage medium of the present invention, and stores various programs executed by the OS (Operating System) and the CPU 601 and various data.

  As the storage medium, not only the ROM 602 but also various types of media such as semiconductor memory such as various optical disks such as CD-ROM and DVD, various magnetic disks such as various magneto-optical disks and flexible disks can be used. Alternatively, the program may be downloaded from a network such as the Internet via the I / F unit 606 and installed in a storage device such as an HDD (Hard Disk Drive) (not shown). In this case, the storage device storing the program in the server on the transmission side is also a storage medium of the present invention. Note that the program may operate on a predetermined OS, and in that case, the OS may take over the execution of some of the various processes described later, It may be included as a part of a group of program files constituting the OS or the like.

  The CPU 601 controls various processes in the color printer 600 according to the ROM 602 that stores various control programs.

  Next, among the functions that the various programs stored in the ROM 602 cause the CPU 601 to execute, characteristic functions for realizing a series of processes related to control of image forming conditions will be described with reference to FIGS.

  FIG. 7 is a block diagram illustrating a functional configuration of the color printer. FIG. 8 is a flowchart illustrating a procedure of detection condition determination processing. FIG. 9 is a diagram illustrating an example of a table associating the threshold value ranges of the average value and the amplitude value of the output voltage from the reflective sensor with detection conditions. 10 and 11 are diagrams illustrating an example of fluctuations in the output voltage from the reflective sensor that has detected the intermediate transfer belt before the toner pattern is formed. FIG. 12 is a flowchart illustrating a procedure of image forming condition control processing. As illustrated in FIG. 7, the CPU 601 implements a determination unit 701, a detection control unit 702, and an image formation condition control unit 703 by following a program stored in the ROM 602.

  First, the detection control unit 702 drives the respective units related to the detection process of the intermediate transfer belt 16 such as the photosensitive drum 10, the developing device 11, the intermediate transfer belt 16, the reflection type sensor 24, and starts up the image forming unit 1. An operation is performed (step S801). In the present embodiment, the detection control unit 702 drives the photosensitive drum 10, the developing device 11, the intermediate transfer belt 16, and the like according to the fastest rotation speed at which the intermediate transfer belt 16 can rotate.

  The detection control unit 702 applies a constant voltage to the light-emitting elements 301 such as FETs and transistors driven by the light-emitting currents included in the reflective sensor 24 so that, for example, the output voltage of specular reflection light is about 4 (V). The amount of light emitted from each light emitting element 301 is controlled (step S802). For example, the detection control unit 702 controls the light emission amount of the light emitting element 301 so that the output voltage from the light receiving element 302 becomes 4 (V).

  Next, the determination unit 701 determines a detection condition based on the amplitude of the output voltage from the reflective sensor 24 that has detected the reflected light from the intermediate transfer belt 16 rotating before the toner pattern is formed (steps S803 to S803). Step S813).

  In the present embodiment, the determination unit 701 determines the detection condition based on the amplitude of the output voltage from the reflective sensor 24 for one rotation of the intermediate transfer belt 16. Specifically, the determination unit 701 resets the counter value n indicating the number of times the output voltage from the intermediate transfer belt 16 is acquired to n = 0 (step S803). In the present embodiment, it is assumed that the counter value n is stored in the RAM 603. Next, the determination unit 701 waits until an interrupt from a timer (not shown) occurs (step S804: No). In the present embodiment, it is assumed that a timer (not shown) generates an interrupt at the highest frequency at which the output voltage from the reflective sensor 24 can be acquired: 5 ms interval (hereinafter, sampling frequency). When an interrupt from a timer (not shown) occurs (step S804: Yes), the determination unit 701 increments the counter value n stored in the RAM 603 (n = n + 1) (step S805).

Further, the determination unit 701 acquires an AD value obtained by converting the output voltage from the reflective sensor 24 into a digital signal by the AD converter included in the I / O unit 604 (step S806). In the present embodiment, the I / O unit 604 digitally outputs output voltages from the reflection sensors 24a, 24b, and 24c, which detect regular reflection light from a background point on the intermediate transfer belt 16, by using an AD converter. converting converted AD value signal _{(χa n, χb n, χc} n) to. Then, the determination unit 701 converts the output voltage from the reflection sensors 24a, 24b, and 24c from the I / O unit 604 into a digital signal (χa _n , χb) in response to the occurrence of an interrupt from a timer (not shown). _n , χc _n ). Incidentally, the determination unit 701, the acquired AD value _{(χa n, χb n, χc} n) shall be stored in the RAM603 in.

Further, determination unit 701, the acquired AD value _{(χa n, χb n, χc} n) each time to store in the RAM 603, AD value stored in the _{RAM603 (χa 1, χb 1,} χc 1) ,. . . _{(Χa n, χb n, χc} n) the average value of _{(χa av, χb av, χc} av) is calculated (step S807). Moreover, determination unit 701, the acquired AD value _{(χa n, χb n, χc} n) each time to store in the RAM 603, AD values already stored in the _{RAM603 (χa 1, χb 1,} χc 1) ,. . . _{(Χa n-1, χb n} -1, χc n-1) of, χa, χb, respective maximum value _{χc (χa max, χb max,} χc max) and the acquired AD value (χa _n, χb _n , Χc _n ). Then, determination unit 701, AD value _{(χa 1, χb 1, χc} 1) ,. . . Of _{(χa n, χb n, χc} n), extracted χa, χb, respective maximum value _{χc (χa max, χb max,} χc max) (steps S808).

Moreover, determination unit 701, the acquired AD value _{(χa n, χb n, χc} n) every time is stored in the RAM 603, AD values already stored in the _{RAM603 (χa 1, χb 1,} χc 1), . . . _{(Χa n-1, χb n} -1, χc n-1) of, χa, χb, respective minimum value _{χc (χa min, χb min,} χc min) and the acquired AD value (χa _n, χb _n , Χc _n ). Then, determination unit 701, AD value _{(χa 1, χb 1, χc} 1) ,. . . Of _{(χa n, χb n, χc} n), extracted χa, χb, respective minimum value _{χc (χa min, χb min,} χc min) (steps S808).

Next, the determination unit 701 determines whether or not the counter value n stored in the RAM 603 is n ≧ 10 (step S809). If the counter value n is smaller than 10 (step S809: NO), the determination unit 701 repeats the processes shown in steps S804 to S808. On the other hand, when the counter value n is 10 or more (step S809: Yes), that is, an AD value obtained by converting the output voltage from the reflective sensor 24 that has detected the reflected light from the intermediate transfer belt 16 into a digital signal is acquired. If you are time (sampling time) it has reached 5ms × 10 = 50ms, determining unit 701, AD value _{(χa n-9, χb n} -9, χc n-9) ,. . . _{(Χa n, χb n, χc} n) averaging (step S810).

  Then, the determination unit 701 determines whether or not the intermediate transfer belt 16 has made a full turn (step S811). If the intermediate transfer belt 16 has not made one revolution (step S811: No), the determination unit 701 repeats the processes shown in steps S804 to S810. That is, in the present embodiment, the determination unit 701 is converted into a digital signal in the I / O unit 604 at a sampling frequency (for example, at an interval of 5 ms) corresponding to the fastest rotation speed at which the intermediate transfer belt 16 can rotate. Get AD value. The determination unit 701 acquires the AD value obtained by converting the output voltage from the reflective sensor 24 that has detected the reflected light from the intermediate transfer belt 16 into a digital signal, and stores the past 5 ms × 10 stored in the RAM 603. = Average AD values for 50 ms. The determination unit 701 repeats these processes every 5 ms to calculate a moving average of AD values for one rotation of the intermediate transfer belt 16. Alternatively, the determination unit 701 may determine the detection condition by using the AD value for one rotation of the intermediate transfer belt 16 obtained at the sampling frequency of 5 ms as it is. Alternatively, the determining unit 701 may average the AD values for 50 ms acquired at the sampling frequency of 5 ms intervals, and determine the detection condition using the AD values for every 50 ms.

If the intermediate transfer belt 16 is round (Step S811: Yes), determination unit 701, the reflection type sensor 24a, 24b, of 24c respectively intermediate transfer belt 16 the average value of one round of AD values (χa _av, χb _av, χc _av ) and the amplitude are compared with the threshold parameter stored in advance in the ROM 603 (step S812), and the detection condition is determined based on the comparison result (step S813). Note that the amplitude of the AD value for one rotation of the intermediate transfer belt 16 is the maximum of the AD value for one rotation of the intermediate transfer belt 16 of each of the reflective sensors 24a, 24b, and 24c from a predetermined output voltage (for example, 4 (V)). value _{(χa max, χb max, χc} max) or minimum value _{(χa min, χb min, χc} min) and maximum displacement of up.

  Specifically, the RAM 603 (storage means according to the present invention) includes a threshold range that is a threshold range of the amplitude of the output voltage from the reflective sensor 24, and an amplitude of the output voltage from the reflective sensor 24 within the threshold range. Are stored in association with the detection conditions when the In the present embodiment, as shown in FIG. 9, the RAM 603 stores the average value and amplitude threshold range of the AD value for one rotation of the intermediate transfer belt 16 and the detection condition in association with each other.

  In the table shown in FIG. 9, the rotational speed a (mm / s) is the fastest rotational speed at which the intermediate transfer belt 16 can rotate. The rotational speed c (mm / s) is the slowest rotational speed at which the intermediate transfer belt 16 can rotate. The rotation speed b (mm / s) is a rotation speed between the rotation speed a (mm / s) and the rotation speed c (mm / s).

  The forming speed a ′ (mm / s) is the fastest forming speed at which the writing unit 605 can form a toner pattern. The formation speed c ′ (mm / s) is the slowest formation speed at which the writing unit 605 can form a toner pattern. The formation speed b ′ (mm / s) is a formation speed between the formation speed a ′ (mm / s) and the formation speed c ′ (mm / s).

  The sampling frequency A (KHz) is the highest frequency at which an AD value obtained by converting the output voltage from the reflective sensor 24 that has detected reflected light from the toner pattern into a digital signal can be acquired from the I / O unit 604. The sampling frequency C (KHz) is the lowest frequency at which the AD value obtained by converting the output voltage from the reflective sensor 24 that has detected the reflected light from the toner pattern into a digital signal can be acquired from the I / O unit 604. The sampling frequency B (KHz) is a frequency between the sampling frequency A (KHz) and the sampling frequency C (KHz).

  The determination unit 701 determines the detection condition stored in association with the threshold range in which the amplitude of the output voltage from the reflective sensor 24 falls within the detection condition for detecting the toner pattern. In this embodiment, the determination unit 701 detects the toner pattern based on the detection condition stored in association with the threshold value range of the amplitude of the AD value for one rotation of the intermediate transfer belt 16 in the table shown in FIG. The detection conditions are determined.

  For example, the average value of the AD values for one rotation of the intermediate transfer belt 16 of all of the reflective sensors 24a, 24b, 24c is within 3.5 to 4.5 (V), and the amplitude of the AD value is an amplitude value of 0 to 1. When the value is within 0.0 (V) (that is, when the fluctuation of the AD value of the intermediate transfer belt 16 is the smallest), the determination unit 701 determines the rotational speed a (mm / s) and the formation speed a ′ (mm / s). The sampling frequency A (KHz) is determined.

  In addition, the average value of the AD value for one rotation of the intermediate transfer belt 16 by at least one of the reflection type sensors 24a, 24b, and 24c is within 3.5 to 4.5 (V), and the amplitude of the AD value is an amplitude value. When it is within 1.0 to 1.5 (V), the determination unit 701 determines the rotation speed b (mm / s), the formation speed b ′ (mm / s), and the sampling frequency B (KHz).

  In addition, the average value of the AD value for one rotation of the intermediate transfer belt 16 by at least one of the reflection type sensors 24a, 24b, and 24c is within 3.5 to 4.5 (V), and the amplitude of the AD value is an amplitude value. When it is within 1.5 to 2.0 (V) (that is, when the variation of the AD value of the intermediate transfer belt 16 is the largest), the determination unit 701 determines the rotational speed c (mm / s) and the formation speed c ′. (Mm / s) and the sampling frequency C (KHz). The determination unit 701 stores the rotation speed, the formation speed, and the sampling frequency determined by the above processing in the RAM 603.

  Further, when the average value of the AD value for one rotation of the intermediate transfer belt 16 by at least one of the reflection type sensors 24a, 24b, and 24c is 3.5 (V) or less, or 4.5 (V) or more, or When the amplitude of the AD value is greater than or equal to the amplitude value 2.0 (V), the determination unit 701 does not perform the determination process of the rotation speed, the formation speed, and the sampling frequency.

  FIG. 10 and FIG. 11 are diagrams showing fluctuations in the AD value for one round of the intermediate transfer belt by the reflective sensor. For example, as shown in FIG. 10, the average value of the AD values for one rotation of all the intermediate transfer belts 16 of the reflective sensors 24a, 24b, 24c is within 3.5 to 4.5, and the amplitude of the AD value is When the amplitude value is within the range of 0 to 1.0 (V), the determination unit 701 determines the rotation speed a (mm / s), the formation speed a ′ (mm / s), and the sampling frequency A (KHz).

  On the other hand, as shown in FIG. 11, only the reflection type sensor 24a has an average value of AD values for one rotation of the intermediate transfer belt 16 in the range of 3.5 to 4.5, and the amplitude of the AD value has an amplitude value of 1.5 to 1.5. When it is within 2.0 (V), the determination unit 701 determines the rotation speed c (mm / s), the formation speed c ′ (mm / s), and the sampling frequency C (KHz).

  Note that the image forming condition control unit 703 stops the control of the image forming condition when the average value and the amplitude of the AD value for one rotation of the intermediate transfer belt 16 of the reflective sensor 24 exceed a predetermined value. In the present embodiment, as shown in FIG. 9, the image forming condition control unit 703 has an average AD value for one turn of the intermediate transfer belt 16 by the reflective sensor 24 of 3.5 (V) or less, or 4.5. When it is equal to or greater than (V), or when the amplitude of the AD value is equal to or greater than the amplitude value 2.0 (V), it is determined as an error and the control of the image forming condition is stopped.

  Returning to FIG. 8, when the detection condition is determined, the detection control unit 702 stops the units related to the detection process of the intermediate transfer belt 16, such as the photosensitive drum 10, the developing device 11, the intermediate transfer belt 16, and the reflective sensor 24. The image forming unit 1 is then lowered (step S814).

  Next, image forming condition control processing will be described with reference to FIG.

  First, the detection control unit 702 rotates the intermediate transfer belt 16 at a rotation speed included in the detection condition determined by the determination unit 701. In the present embodiment, the detection control unit 702 drives the photosensitive drum 10, the developing device 11, the intermediate transfer belt 16, and the like according to the rotation speed included in the detection condition determined by the processing shown in FIG. The start-up operation of the unit 1 is performed (step S1201).

  The detection control unit 702 applies a constant voltage to the light-emitting elements 301 such as FETs and transistors driven by the light-emitting currents included in the reflective sensor 24 so that, for example, the output voltage of specular reflection light is about 4 (V). The amount of light emitted from each light emitting element 301 is controlled (step S1202). For example, the detection control unit 702 controls the light emission amount of the light emitting element 301 so that the output voltage output from the light receiving element 302 is 4 (V).

  Next, the detection control unit 702 uses the determination unit 701 to determine the frequency at which the AD value obtained by converting the output voltage from the reflective sensor 24 that has detected the reflected light from the toner pattern into a digital signal is acquired from the I / O unit 604. The sampling frequency included in the detected condition is set (step 1203). In the present embodiment, the detection control unit 702 stores the sampling frequency included in the detection condition determined by the determination unit 701 in the RAM 603.

  Next, the detection control unit 702 forms a toner pattern on the intermediate transfer belt 16 at a formation speed included in the detection condition determined by the determination unit 701 (step S1204). In the present embodiment, the detection control unit 702 controls the writing unit 605 based on the formation speed included in the detection condition determined by the determination unit 701 to form a toner pattern on the intermediate transfer belt 16.

  Then, the image forming condition control unit 703 controls the image forming condition based on the AD value of the toner pattern acquired according to the sampling frequency included in the detection condition determined by the determining unit 701 (step S1205). In the present embodiment, the image forming condition control unit 703 converts the output voltage output from the reflective sensor 24 into a digital signal by an AD converter included in the I / O unit 604 in accordance with the occurrence of an interrupt from a timer (not shown). Obtain the converted AD value. In the present embodiment, it is assumed that a timer (not shown) generates an interrupt based on the sampling frequency stored in the RAM 603. Further, the image forming condition control unit 703 corrects the color misregistration, density, and the like correction parameters (for example, color misregistration parameter, toner density, etc.) based on the AD value indicating the color misregistration, density, etc. acquired from the I / O unit 604. And the calculated correction parameter is stored in the RAM 603. The image forming condition control unit 703 executes control of image forming conditions such as color misregistration and density using the correction parameters stored in the RAM 603 to prepare for an image forming operation.

  When the control is completed, the detection control unit 702 stops the units related to the toner pattern detection process, such as the photosensitive drum 10, the developing device 11, the intermediate transfer belt 16, the reflection type sensor 24, and the like. A fall operation is performed (step S1206).

  As described above, according to the color printer of the present embodiment, the image forming condition control process is executed in accordance with the detection condition determined by the determining unit 701, thereby preventing any problems such as distortion and undulation of the intermediate transfer belt 16. Since a series of processes for controlling the image forming conditions can be executed according to the toner pattern detection conditions according to the strength of the stable behavior, it is possible to prevent the downtime of the color printer from becoming unnecessarily long. .

  In the present embodiment, the images from the photosensitive drums 10Y, 10M, 10C, and 10K are temporarily transferred onto the intermediate transfer belt 16 and superimposed on the intermediate transfer belt 16 to form a composite color image. Although an application example of the “indirect transfer method” in which the composite color image is transferred onto the transfer paper P at once by the secondary transfer roller 18 has been described, the present invention is not limited to this. A “direct transfer type” image forming unit 1300 (sequentially transferring a monochrome image formed on each of 10Y, 10M, 10C, and 10K onto a sheet that is a transfer body P conveyed by an intermediate medium (conveyance belt) 25. The same applies to (shown in FIG. 13). FIG. 13 is a diagram illustrating an example of an image forming unit installed in a color printer.

FIG. 3 is a diagram illustrating an example of an image forming unit installed in the color printer according to the present embodiment. FIG. 4 is a diagram illustrating an example of a toner pattern formed on an intermediate transfer belt and a position of a reflective sensor that detects the toner pattern. It is a figure which shows an example of a structure of a reflection type sensor. It is a figure which shows the output voltage of the reflective sensor which detected the pattern for density control. It is a figure which shows the output voltage of the reflection type sensor which detected the pattern for color misregistration control. It is a figure which shows the main structures of the color printer concerning this Embodiment. 2 is a block diagram illustrating a functional configuration of a color printer. FIG. It is a flowchart which shows the procedure of the determination process of detection conditions. It is a figure which shows an example of the table which matches the threshold value range of the average value and amplitude value of an output voltage from a reflective sensor, and detection conditions. FIG. 6 is a diagram illustrating an example of fluctuations in output voltage from a reflective sensor that detects an intermediate transfer belt before forming a toner pattern. FIG. 6 is a diagram illustrating an example of fluctuations in output voltage from a reflective sensor that detects an intermediate transfer belt before forming a toner pattern. It is a flowchart which shows the procedure of the control process of an image formation condition. FIG. 3 is a diagram illustrating an example of an image forming unit installed in a color printer.

Explanation of symbols

1,1300 Image forming unit 10Y, 10M, 10C, 10K Photosensitive drum 11Y, 11M, 11C, 11K Developing device 12Y, 12M, 12C, 12K Charging device 13Y, 13M, 13C, 13K, 20 Cleaning device 14Y, 14M, 14C , 14K Primary transfer roller 15 Exposure device 16, 25 Intermediate transfer belt 17 Drive roller 18 Secondary transfer roller 19 Tension roller 21 Paper feed unit 22 Registration roller pair 23 Fixing device 24a, 24b, 24c Reflective sensor 25 Intermediate medium 301 Light emitting element 302, 303 Light receiving element 304 Holder 600 Color printer 601 CPU
602 ROM
603 RAM
604 I / O unit 605 writing unit 606 I / F unit 701 determining unit 702 detection control unit 703 image forming condition control unit

Claims (5)

An image forming apparatus that controls image forming conditions based on an output voltage from a sensor that detects reflected light from a toner pattern for controlling image forming conditions formed on a rotating body,
Determining means for determining a detection condition of the toner pattern based on an amplitude of an output voltage from the sensor that detects reflected light from the rotating body before the formation of the toner pattern;
Detection control means for detecting reflected light from the toner pattern by the sensor according to the determined detection condition;
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the determination unit determines the detection condition based on an amplitude of an output voltage from the sensor for one rotation of the rotating body. Storage means for storing the threshold range, which is a threshold range of the amplitude of the output voltage from the sensor, and the detection condition when the amplitude of the output voltage from the sensor falls within the threshold range in association with each other. In addition,
The determination means determines the detection condition stored in association with the threshold range in which the amplitude of the output voltage from the sensor falls as the detection condition for detecting reflected light from the toner pattern. The image forming apparatus according to claim 1, wherein:   The detection control means further stops detecting the reflected light from the toner pattern by the sensor when an average value and an amplitude of an output voltage from the sensor exceed a predetermined value. 4. The image forming apparatus according to any one of items 1 to 3.   The detection condition includes a rotation speed of the rotating body, a formation speed of the toner pattern on the rotating body, and a frequency for sampling an output voltage from the sensor that detects reflected light from the toner pattern. The image forming apparatus according to any one of claims 1 to 4.

Images