JP2004219547A - Belt moving device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem of an image forming apparatus that an intermediate transfer belt cannot be moved so as to follow a target position, when the output signal of a marker detection means becomes abnormal. <P>SOLUTION: When the output signal of the marker detection means that detects a marker on a belt is in an abnormal state, only the output value of a rotation state detection means that detects the rotating state of a drive shaft for moving the belt is fed back to make the belt follow the target position. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a belt moving device that moves a belt such as an intermediate transfer belt and a transfer material conveying belt, and an image forming apparatus such as a copying machine, a printer, and a facsimile.
[0002]
[Prior art]
Japanese Patent Application Laid-Open No. H11-163,086 has marker detecting means for detecting a marker on an intermediate transfer belt in an image forming apparatus having one photosensitive drum and an intermediate transfer belt, and uses an output signal of the marker detecting means. In the belt moving device which moves the intermediate transfer belt to follow the target position, the number of markers detected by the marker detecting means when the output signal of the marker detecting means is normal is compared with the number of markers. There is described a belt moving device which determines whether the output signal of the marker detecting means is abnormal based on a change in the number of markers detected by the detecting means.
[0003]
Patent Document 2 discloses a tandem-type image forming apparatus that includes a drive shaft for moving an intermediate transfer belt in a tandem image forming apparatus, and a transmission unit that transmits a driving force from a drive source to the drive shaft. A belt moving device that moves by following a position is described.
[0004]
[Patent Document 1]
JP 08-146698 A
[Patent Document 2]
JP 08-085235 A
[0005]
[Problems to be solved by the invention]
In the above-described belt moving device, the marker provided on the belt becomes dusty, and the distance and angle between the marker detecting means for detecting the marker and the marker change due to the warp or meandering of the belt, so that the marker detecting means is not used. If the output signal deviates from the specified value and becomes abnormal, the intermediate transfer belt cannot be moved to follow the target position. For this reason, in the color image forming apparatus using the belt moving device, if the output signal of the marker detecting means deviates from the specified value and becomes abnormal, the positional deviation of the intermediate transfer belt occurs and the color deviation occurs. In addition, the image forming apparatus must be brought down during the period when the serviceman has come to replace the belt.
[0006]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a belt moving device that can move a belt by following a belt surface target position even when an output signal of a marker detecting unit becomes abnormal.
Further, the present invention provides an image forming apparatus capable of preventing a serviceman from being down during a period when a belt is replaced by a serviceman even if an output signal of a marker detecting unit becomes abnormal, thereby suppressing a color shift. The purpose is to do.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 includes a driving shaft for moving a belt, a transmission unit for transmitting a driving force from a driving source to the driving shaft, and a position in a moving direction of the belt. Marker detecting means for detecting a marker provided on the belt for recognition, rotational state detecting means for detecting a rotational state of the drive shaft, and a difference between an output value of the marker detecting means and a belt surface target position. The required surface position control means, the value obtained by the surface position control means and the belt surface target position are added, and the added value is divided by the value obtained by adding the radius of the drive shaft and the thickness of the belt. A drive shaft angle control means for determining a drive shaft target position, and causing the drive source to follow the belt surface target position from a difference between the drive shaft target position and an output value of the rotation state detecting means. In location, when the output signal of said marker detection means is abnormal, it is intended to follow the belt by feeding back only the output value of the rotational state detecting means to the belt surface target position.
[0008]
According to a second aspect of the present invention, in the belt moving device according to the first aspect, the belt surface target position when only the output value of the rotation state detecting unit is fed back is determined when the output signal of the marker detecting unit is normal. And correcting the belt so as to follow the belt surface target position from the difference between the output value of the rotation state detecting means and the belt surface target position.
[0009]
According to a third aspect of the present invention, in the belt moving device according to the first aspect, the determination of the output signal abnormality of the marker detecting means includes determining the steady state belt surface target position and the output value of the marker detecting means in the belt control. This is performed by detecting whether the deviation from the value deviates from a value in a predetermined range.
[0010]
According to a fourth aspect of the present invention, in the belt moving device according to the first aspect, the determination of the output signal abnormality of the marker detection unit is performed when the marker detection unit detects that the output signal of the marker detection unit is normal. This is performed when the number of the markers detected by the marker detection means changes as compared with the number of the markers.
[0011]
According to a fifth aspect of the present invention, there is provided a tandem-type image forming apparatus including the belt moving device according to any one of the first to fourth aspects, wherein the intermediate transfer belt or the transfer material conveying belt is moved by the belt moving device. It is something to move.
[0012]
According to a sixth aspect of the present invention, there is provided an image forming apparatus having one photosensitive drum and an intermediate transfer belt, comprising the belt moving device according to any one of the first to fourth aspects. This is for moving the intermediate transfer belt or the transfer material transport belt.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 4 shows Embodiment 1 of the present invention. The first embodiment is an example of a belt moving device used for an engine drive system in an image forming apparatus.
The intermediate transfer belt 901 to be driven is stretched over a plurality of rollers 902 to 906 including a drive roller 938 as a drive shaft (not shown), and the drive shaft 938, a drive shaft timing pulley 907, a timing belt 908, a motor shaft timing pulley 909 and the like, and connected to and driven by a motor 910 as a drive source.
[0014]
The intermediate transfer belt device includes an intermediate transfer belt 901, and an encoder scale (marker) 911 provided for one rotation along the moving direction of the intermediate transfer belt 901 outside the image area of the intermediate transfer belt 901. Further, an optical head (sensor; pickup) 912 as a marker detecting means for reading a marker 911 on the intermediate transfer belt 901 in order to recognize the position of the intermediate transfer belt 901 in the moving direction faces the marker 911 on the intermediate transfer belt 901. It is attached to a predetermined position. Further, a belt drive shaft encoder 913 is attached to the drive shaft 938.
[0015]
A drum-shaped photoconductor (photoconductor drum) 914 as an image carrier includes a drive shaft 915 of the photoconductor 914, a drive shaft timing pulley (not shown) fixed to the drive shaft 915, the drive shaft timing pulley, and the motor shaft timing. It is connected to and driven by a motor 918 as a driving source via a transmission system such as a timing belt 916 wound around a pulley 917 and a motor shaft timing pulley 917. A rotary encoder 919 as a sensor for detecting rotation of the drive shaft 915 is attached to a drive shaft 915 of the photoconductor 914.
[0016]
The paper transfer roller 920 is moved toward and away from the intermediate transfer belt 901 on the roller 905 by a contact / separation mechanism, and is a drive source via a transmission system (not shown) such as a drive shaft timing pulley, a timing belt, and a motor shaft timing pulley. It is connected to and driven by a motor. The motors 910 and 918 are driven by a motor driver 921, and the motor controller 922 controls the motor 910 via the motor driver 921 using the output signals of the optical head (sensor) 912 and the belt drive shaft encoder 913, and controls the rotary encoder 919. The motor 918 is controlled via the motor driver 921 using the output signal.
[0017]
The intermediate transfer belt 901 and the photoconductor 914 rotate in contact with each other. Further, the intermediate transfer belt 901 and the paper transfer roller 920 are pressed and rotated by the contact / separation mechanism during the secondary transfer, and the paper as the transfer material passes between them. The toner image formed on the photoconductor 914 is transferred to the intermediate transfer belt 901, and the toner image on the intermediate transfer belt 901 is transferred to a sheet passing between the intermediate transfer belt 901 and the paper transfer roller 920. A charging roller and a cleaning blade (not shown) are adjacent to the intermediate transfer belt 901 and the photoconductor 914.
[0018]
In the above description, the driving target is the intermediate transfer belt 901, but the transmission mechanism is the same as the above-described transmission mechanism even if the driving target is a paper transport belt as a transfer material transport belt. Although the transmission mechanism uses a timing belt, a transmission mechanism using gears may be used, or a direct mechanism in which a motor is directly connected to a driving target may be used. Further, in the above description, the place where the encoder is mounted is the drive shaft, but it may be directly connected to the motor shaft.
[0019]
Next, the hardware configuration of the drive system of the first embodiment will be described with reference to FIG. First, a microcomputer 923 is provided as control means for performing overall control of the first embodiment. In the microcomputer 923, a microprocessor (CPU) 924, a read-only memory (ROM) 925, and a random access memory (RAM) 926 are connected via a bus 927, respectively.
[0020]
The belt conveyance device 928 has an intermediate transfer belt 901, and a drive shaft 938 of the intermediate transfer belt 901 is connected to a motor 910 via the transmission system 929. An output signal of an optical head (belt sensor) 912 that reads an encoder scale (marker) 911 on the intermediate transfer belt 901 is supplied to a microcomputer via a correction information creating unit 930, an interface (I / F) 931 for state detection, and a bus 927. 923. Here, the state detection interface 931 includes a marker detection signal count (coarse counter count) from the correction information creation unit 930, a signal interpolation clock count (counter fine counter count), and a drive shaft encoder (belt drive shaft). The sensor counts the pulse signal from the sensor 913 and converts it into a digital value, and has a function of counting the number of pulses. At this time, the state detection interface 931 may have a function of associating (correlating) with the movement position of the intermediate transfer belt 901 by using the origin information of the correction information creation unit 930.
[0021]
The motor 910 is connected to the microcomputer 923 via a bus 927, a driving interface 932, and a driver 921. The drive interface 932 converts a digital signal of a calculation result in the microcomputer 923 into an analog signal, supplies the analog signal to a motor drive driver 921 which is a drive device, and controls a current and a voltage applied to the motor 910. As a result, the intermediate transfer belt 901 is driven so as to follow a predetermined target position. At this time, the surface position of the intermediate transfer belt 901 is detected from the output signal of the sensor 912 to the encoder scale (marker) 911 by the state detection interface 931 via the correction information creating means 930, and is taken into the microcomputer 923. When the interval between the markers 911 is wide, the correction information creating unit 930 may interpolate the position within the interval between the markers 911 with a clock. Here, the motor controller 922 includes a microcomputer 923, a bus 927, a correction information creating unit 930, an interface 931 for state detection, and an interface 932 for driving.
[0022]
The position control of the belt moving device according to the first embodiment is executed by an arithmetic processing function in the microcomputer 923. It is obvious that a DSP (digital signal processor) having a high numerical processing capability may be used instead of the microcomputer 923.
[0023]
FIG. 1 is a functional block diagram when position control is performed on a drive target according to the first embodiment. The microcomputer 923 converts the command 1 for the target belt surface position directly into the target drive shaft position (angle), compares the command 2 for the target belt surface position with the belt surface position from the interface 931 for state detection, and The deviation is calculated by the surface position control means 933, and the addition to the command 1 of the belt surface target position is executed at the point A. In this case, the microcomputer 923 converts the result of the addition by a value obtained by adding the radius of the drive shaft 938 of the intermediate transfer belt 901 and the thickness of the intermediate transfer belt 901 to a drive shaft target position (angle).
[0024]
Further, the microcomputer 923 calculates a deviation between the drive shaft target position (angle) and the drive shaft angle from the state detection interface 931 by the drive shaft angle control means 934, and outputs the deviation to the motor 910 via the driver 921. A current is applied in accordance with the deviation, and the intermediate transfer belt 901 is driven to follow the target position from the motor 910 of the drive target 935 via the transmission system 929. When there is no deviation between the surface position of the intermediate transfer belt 901 and the target position on the belt surface, the position of the drive shaft 938 is controlled by the command 1. However, due to the misalignment of the core of the intermediate transfer belt 901 and the eccentricity of the drive shaft 938, the intermediate position is controlled. When a deviation occurs between the surface position of the transfer belt 901 and the target position on the belt surface, the target angle of the drive shaft 938 of the intermediate transfer belt 901 is corrected so as to eliminate the deviation. Here, the microcomputer 923 detects the marker 911 provided on the intermediate transfer belt 901 in order to recognize the position of the intermediate transfer belt 901 in the moving direction by the surface position sensor abnormality determination unit 936. It is determined whether the output signal of the sensor 912 is abnormal. If it is determined that the output signal of the sensor 912 is abnormal, the operation result of the surface position control unit 933 is turned off by the ON / OFF switching unit 937 and A Do not add to command 1 at the point. Therefore, even if the output signal of the sensor 912 as the marker detecting means becomes abnormal, the command 1 is directly converted to the drive shaft target position (angle), and the rotation comprising the belt drive shaft sensor 913 and the state detection interface 931 is performed. The output value of the state detection unit (the drive shaft angle from the state detection interface 931) is fed back, and the drive shaft angle control unit 934 drives the motor 910 so that the intermediate transfer belt 901 follows the target position.
[0025]
As described above, according to the first embodiment, when the output signal of the sensor 912 as the marker detection unit is abnormal, only the output value of the rotation state detection unit including the belt drive shaft sensor 913 and the state detection interface 931 is used. Is fed back to cause the intermediate transfer belt 901 to follow the target position. Therefore, even if an abnormality occurs in the marker detection unit, the feedback control of the intermediate transfer belt 901 can be performed using only the signal from the rotation state detection unit.
[0026]
Further, in the first embodiment, the deviation between the position obtained by converting the detection angle of the rotation state detecting means into the position when the output signal of the sensor 912 as the marker detecting means is normal and the belt surface target position (command 1). Is as shown in FIG. When the output signal of the sensor 912 is normal, even if the deviation between the belt surface target position and the surface position of the intermediate transfer belt 901 is 0, a deviation of ± 100 μm in one second cycle, which is one rotation cycle of the intermediate transfer belt 901. , There is a deviation of ± 25 μm in a cycle of 0.1 seconds which is 938 cycles of the drive shaft.
[0027]
Therefore, according to the second embodiment of the present invention, in the first embodiment, the microcomputer 923 performs a case where the output signal of the sensor 912 as the marker detection unit becomes abnormal and only the output value of the rotation state detection unit is fed back. A target that cancels the deviation between the output value of the rotation state detecting means when the output signal of the sensor 912 is normal (a value obtained by converting the drive shaft angle from the state detection interface 931 into a position) and the belt surface target position. The position is added to the belt surface target position (command 1) as correction data for the eccentricity of the drive shaft 938 of the intermediate transfer belt 901 and the positional deviation of one cycle of the intermediate transfer belt, and the belt surface target position (command 1) is subjected to intermediate transfer. Correction is performed so that the belt 901 follows the target position on the belt surface.
[0028]
FIG. 3 shows the position when the output angle of the rotation state detecting means is converted into the position when the output signal of the sensor 912 is normal and the belt surface target position (command 1) when only the output value of the rotation state detecting means is fed back. ) Is a target position to be added to the belt surface target position (command 1) in order to cancel the deviation from the target position. At this time, the correlation between the detection value of the sensor 912 and the detection position from the rotation state detection unit (the value obtained by converting the drive shaft angle from the state detection interface 931 into a position) uses the origin information of the intermediate transfer belt 901. Can be obtained.
[0029]
According to the second embodiment, the belt surface target position when only the output value of the rotation state detection means is fed back is determined by the output value of the rotation state detection means when the output signal of the marker detection means is normal and the belt surface target position. Is corrected so that the intermediate transfer belt 901 follows the target position, correction data for the eccentricity of the drive shaft 938 of the intermediate transfer belt 901 and the positional deviation of one cycle of the intermediate transfer belt is added to the drive shaft target position. The position of the intermediate transfer belt can be correctly controlled using only the output signal of the rotation state detecting means.
[0030]
In the first embodiment, as shown in FIG. 6, the position fluctuation Pbv of the intermediate transfer belt 901 in the steady state is about 5 μm. However, dust adheres between the markers and the belt surface target position and the marker detecting means. Is varied to 120 μm.
Therefore, in the third embodiment of the present invention, in the first embodiment, the microcomputer 923 causes the surface position sensor abnormality determination unit 936 to output the command 2 of the belt surface target position and the value (the value from the sensor 912 as the marker detection unit). (The belt surface position from the state detection interface 931) is constantly monitored to detect whether or not the value deviates from a predetermined range, thereby determining whether or not the output signal of the sensor 912 as the marker detecting means is abnormal. Judge.
[0031]
According to the third embodiment, the determination of the output signal abnormality of the sensor 912 as the marker detecting means is based on the determination that the deviation between the steady state belt surface target position in the position control of the intermediate transfer belt 901 and the output value of the sensor 912 is within a predetermined range. Since the detection is performed by detecting whether or not the value deviates from the value of マ ー カ, the output signal abnormality of the marker detecting means can be easily determined, and the selection of the sensor signal to be fed back (the surface position control means 933 by the ON / OFF switching means 937). (On / off of the calculation result) can be performed correctly.
[0032]
In the first embodiment, as shown in FIG. 7, the interval Xes between the end position and the start position of the processing of the marker 9911 on the intermediate transfer belt 901 is different from the interval between the other markers, and is different from the length of the intermediate transfer belt 901. Depends on the variation of Therefore, in the fourth embodiment of the present invention, in the first to third embodiments, the length in the width direction of the marker 911 is longer than the other markers by the portion 911a of Xes, and the portion 911a is different from the marker detecting means 912. Xes is identified by detecting the Xes with Xes detecting means (not shown). The signal detected by the Xes detecting means is input to the microcomputer 923 as an origin signal. The microcomputer 923 always monitors the deviation between the command 2 of the belt surface target position and the value from the sensor 912 (the belt surface position from the state detecting interface 931) as the marker detecting means by the surface position sensor abnormality determining means 936. Also, when determining whether or not the output signal of the sensor 912 is abnormal, the origin signal detected by the Xes detecting means does not determine that the output signal of the sensor 912 is abnormal as an exception to the abnormality. Since there is an origin signal from the Xes detecting means, the surface position sensor abnormality determining means 936 determines the number of markers 911 detected by the sensor 912 and the number of markers 911 detected by the sensor 912 when the output signal of the sensor 912 is normal. It is determined that the output signal of the sensor 912 is abnormal by detecting that the number of the markers 911 detected by the sensor 912 has changed as compared with.
[0033]
According to the fourth embodiment, the determination of the abnormality of the output signal of the sensor 912 as the marker detecting means is performed by comparing the number of the markers 911 detected by the sensor 912 when the output signal of the sensor 912 is normal with the detection of the sensor 912. Since the number of the markers 911 is changed, it is possible to easily determine the abnormality of the output signal of the marker detecting means, and to select the sensor signal to be fed back (by the ON / OFF switching means 937 to the surface position control means 933). ON / OFF of the calculation result) can be performed correctly.
[0034]
FIG. 8 schematically shows an image forming unit according to the fifth embodiment of the present invention. The fifth embodiment is an embodiment of a color copying machine as an image forming apparatus. In addition to the image forming unit shown in FIG. 8, a color image reading unit (hereinafter, referred to as a color scanner) (not shown), a paper feeding unit, and a main color copying machine It is composed of a control section for controlling the driving of each section of the machine. The color scanner separates and reads color image information of a document into, for example, red, green, and blue (hereinafter, referred to as R, G, and B, respectively) colors and converts them into electrical image signals. A color conversion process is performed by an image processing unit (not shown) based on the intensity levels of the R, G, and B color image signals obtained by the color scanner, and black, cyan, magenta, and yellow (hereinafter, respectively) Bk, C, M, and Y).
[0035]
The image forming unit shown in FIG. 8 includes a photoconductor drum 200 as an image carrier, a charging charger 201 as a charging unit, a photoconductor cleaning device 210 having a cleaning blade and a fur brush, a writing optical unit (not shown) as an exposure unit, The image forming apparatus includes a revolver developing unit 400 as a developing unit, an intermediate transfer unit 500, a secondary transfer unit 600, and a fixing unit using a pair of fixing rollers (not shown).
[0036]
The photoconductor drum 200 is rotated by a driving unit (not shown) and rotates counterclockwise as indicated by an arrow in FIG. 8, and around the charging charger 201, the photoconductor cleaning device 210, and the revolver developing unit 400. A selected developing device, an intermediate transfer belt 501 as an intermediate transfer body of the intermediate transfer unit 500, and the like are arranged. The surface of the photoconductor drum 200 is uniformly charged by the charging charger 201. The writing optical unit converts the color image data input from the color scanner via the image processing unit into an optical signal, and exposes the uniformly charged surface of the photosensitive drum 200 with the optical signal to perform optical writing. By doing so, an electrostatic latent image is formed on the surface of the photosensitive drum 200. The writing optical unit includes, for example, a semiconductor laser as a light source, a laser emission drive control unit that performs emission drive control of the semiconductor laser based on color image data input from a color scanner via an image processing unit, and a semiconductor laser. , A motor for rotating the polygon mirror, an f / θ lens for forming an image of the laser light from the polygon mirror on the surface of the photosensitive drum 200, and a It is composed of a mirror or the like that reflects laser light.
[0037]
The revolver developing unit 400 includes a Bk developing device 401 using Bk toner, a C developing device 402 using C toner, an M developing device 403 using M toner, a Y developing device 404 using Y toner, and the entire unit counterclockwise. It is constituted by a developing revolver driving unit which rotates.
[0038]
Each of the developing units 401 to 404 installed in the revolver developing unit 400 rotates the developing unit by bringing an ear of developer into contact with the surface of the photosensitive drum 200 in order to develop an electrostatic latent image on the photosensitive drum 200. The image forming apparatus includes a developing sleeve as a developer carrier, a developer paddle that rotates to pump up and agitate the developer, and a developing sleeve driving unit that rotates the developing sleeve clockwise as indicated by an arrow.
[0039]
In the fifth embodiment, the toner in each of the developing devices 401 to 404 is negatively charged by stirring with the ferrite carrier, and a negative DC voltage is applied to each developing sleeve by a developing bias power source (not shown) as a developing bias applying unit. A developing bias voltage in which an AC voltage Vac (AC component) is superimposed on the voltage Vdc (DC component) is applied, and each developing sleeve is biased to a predetermined voltage with respect to the metal base layer of the photosensitive drum 200. In a standby state of the main body of the color copying machine, the revolver developing unit 400 is stopped at the home position where the Bk developing device 401 is located at the developing position.
[0040]
When the copy start key is pressed, reading of the original image data is started, and light writing by the laser light L, that is, formation of an electrostatic latent image is started based on the color image data. Hereinafter, the electrostatic latent image based on the Bk image data is referred to as a Bk electrostatic latent image. The electrostatic latent image based on the C image data, the electrostatic latent image based on the M image data, and the electrostatic latent image based on the Y image data are similarly referred to as a C electrostatic latent image, an M electrostatic latent image, and a Y electrostatic latent image.
[0041]
The Bk developing device 401 starts rotation of the Bk developing sleeve before the Bk electrostatic latent image reaches the Bk developing position so that development can be performed from the front end of the Bk electrostatic latent image. The latent image is developed with Bk toner. Then, the Bk developing device 401 continues the developing operation of the Bk electrostatic latent image thereafter, but when the rear end portion of the Bk electrostatic latent image passes the Bk developing position, the developing device of the next color immediately develops. The revolver developing unit 400 rotates until it reaches the position. This is completed at least before the leading end of the electrostatic latent image based on the next image data reaches the developing position.
[0042]
The intermediate transfer unit 500 includes an intermediate transfer belt 501 which is an intermediate transfer member stretched over a plurality of rollers. Around the intermediate transfer belt 501, a secondary transfer belt 601 as a transfer material conveying belt of the secondary transfer unit 600, a secondary transfer bias roller 605 as a secondary transfer charge applying unit, and an intermediate transfer body cleaning unit. A belt cleaning blade 504, a lubricant application brush 505 serving as a lubricant application unit, and the like are arranged to face each other.
[0043]
The intermediate transfer belt 501 is stretched around a primary transfer bias roller 507, a belt driving roller 508, a belt tension roller 509, a secondary transfer opposing roller 510, a cleaning opposing roller 511, and an earth roller 512 as primary transfer charge applying means. ing. . Each of the rollers 507 to 512 is formed of a conductive material, and each of the rollers 508 to 512 other than the primary transfer bias roller 507 is grounded.
[0044]
To the primary transfer bias roller 507, a transfer bias controlled to a predetermined magnitude of current or voltage in accordance with the number of superimposed toner images is applied by a primary transfer power supply 801 that has been subjected to constant current or constant voltage control. Is done. The intermediate transfer belt 501 is driven in a direction indicated by an arrow by a belt drive roller 508 that is driven to rotate by a drive motor (not shown). The intermediate transfer belt 501 is made of a semiconductor or an insulator and has a single-layer or multilayer structure.
[0045]
In a transfer unit that transfers the toner image on the photosensitive drum 200 to the intermediate transfer belt 501 (hereinafter, referred to as a primary transfer unit), the intermediate transfer belt 501 is transferred to the photosensitive drum 200 by a primary transfer bias roller 507 and an earth roller 512. The nip portion having a predetermined width is formed between the photosensitive drum 200 and the intermediate transfer belt 501 by being stretched so as to be pressed.
[0046]
The lubricant applying brush 505 is for polishing zinc stearate 506 as a lubricant formed in a plate shape, and applying the polished fine particles to the intermediate transfer belt 501. The lubricant application brush 505 is configured to be able to contact the intermediate transfer belt 501, and is contacted with the intermediate transfer belt 501 at a predetermined timing by a contact / separation mechanism.
[0047]
The secondary transfer unit 600 includes a secondary transfer belt 601 stretched over three support rollers 602, 603, and 604, and a stretched portion between the support rollers 602 and 603 of the intermediate transfer belt 501 is subjected to secondary transfer. It can be pressed against the opposing roller 510 via the intermediate transfer belt 501. One of the three support rollers 602, 603, and 604 is a drive roller that is rotationally driven by a drive unit (not shown), and drives the secondary transfer belt 601 in a direction indicated by an arrow in the drawing.
[0048]
The secondary transfer bias roller 605 is a secondary transfer unit, and is disposed so as to sandwich the intermediate transfer belt 501 and the secondary transfer belt 601 between the secondary transfer opposing roller 510 and performs constant current control. A transfer bias of a predetermined current is applied by the secondary transfer power supply 802. The support rollers 602 and 2 are arranged so that the secondary transfer belt 601 and the secondary transfer bias roller 605 can take a position where the secondary transfer belt 601 presses the secondary transfer opposing roller 510 via the intermediate transfer belt 501 and a position where the secondary transfer bias roller 605 separates. An unillustrated separation / contact mechanism for driving the next transfer bias roller 605 in the direction of the arrow is provided. The secondary transfer belt 601 and the support roller 602 at the separated position are shown by two-dot chain lines in FIG.
[0049]
The registration roller pair 650 feeds the transfer paper P as a transfer material at a predetermined timing between the intermediate transfer belt 501 and the secondary transfer belt 601 sandwiched between the secondary transfer bias roller 605 and the secondary transfer opposing roller 510. . A portion of the secondary transfer belt 601 which is stretched around the support roller 603 on the fixing unit side is provided with a transfer paper charge remover 606 as a transfer material charge remover and a belt charge remover 607 as a transfer material carrier charge remover. They are facing each other. A cleaning blade 608, which is a transfer material carrier cleaning unit, is in contact with a portion of the secondary transfer belt 601 that is stretched around the lower support roller 604 in the drawing.
[0050]
The transfer paper discharging charger 606 discharges the electric charges held in the transfer paper, so that the transfer paper can be satisfactorily separated from the secondary transfer belt 601 by the strength of the transfer paper itself. The belt static elimination charger 607 eliminates electric charges remaining on the secondary transfer belt 601. The cleaning blade 608 is for removing the adhered matter attached to the surface of the secondary transfer belt 601 for cleaning.
[0051]
When the image forming cycle is started in the color copying machine configured as described above, the photosensitive drum 200 is rotated in a counterclockwise direction indicated by an arrow by a drive motor (not shown), and the intermediate transfer belt 501 is driven by a belt drive roller 508. Rotates clockwise as indicated by the arrow. The formation of a Bk toner image, the formation of a C toner image, the formation of an M toner image, and the formation of a Y toner image are performed with the rotation of the photosensitive drum 200, and the transfer bias applied to the primary transfer bias roller 507 causes the transfer from the photosensitive drum 200. The Bk toner image, the C toner image, the M toner image, and the Y toner image are superimposed and primary-transferred onto the intermediate transfer belt 501, and finally a color toner image is formed on the intermediate transfer belt 501.
[0052]
For example, Bk toner image formation is performed as follows. The charging charger 201 uniformly charges the surface of the photosensitive drum 200 to a predetermined potential with negative charge by corona discharge. Then, raster exposure with laser light is performed on the photosensitive drum 200 by a writing optical unit (not shown) based on the Bk color image signal. When this raster image is exposed, in the exposed portion of the surface of the photosensitive drum 200 that is initially uniformly charged, the charge proportional to the amount of exposure light disappears, and a Bk electrostatic latent image is formed.
When the negatively charged Bk toner on the Bk developing roller of the Bk developing device 401 comes into contact with the Bk electrostatic latent image on the photosensitive drum 200, the toner remains on the portion of the photosensitive drum 200 where the charge remains. The toner does not adhere to the portion having no charge, that is, the exposed portion, and the toner is adsorbed, and a Bk toner image similar to the electrostatic latent image is formed. The Bk toner image formed on the photosensitive drum 200 is transferred onto the surface of the intermediate transfer belt 501 that is driven at a constant speed in contact with the photosensitive drum 200. Hereinafter, the transfer of the toner image from the photosensitive drum 200 to the intermediate transfer belt 501 is referred to as belt transfer. A small amount of untransferred residual toner remaining on the surface of the photoconductor drum 200 after the belt transfer is cleaned by the photoconductor cleaning device 210 in preparation for reuse of the photoconductor drum 200.
[0053]
On the photosensitive drum 200 side, the process proceeds to the C image forming step after the Bk image forming step. At a predetermined timing, reading of the original image is started by the color scanner, and the surface of the photosensitive drum 200 is uniformly charged by the charging charger 201. You. The writing optical unit converts the C image data input from the color scanner via the image processing unit into an optical signal, and exposes a uniformly charged surface of the photosensitive drum 200 by the optical signal to perform optical writing. As a result, a C electrostatic latent image is formed on the surface of the photosensitive drum 200.
[0054]
Then, after the trailing end of the Bk electrostatic latent image on the photosensitive drum 200 has passed and before the leading end of the C electrostatic latent image has reached, the rotating operation of the revolver developing unit 400 is performed to perform the C developing. The C electrostatic latent image is developed by the C developing device 402 with the C toner.
[0055]
Thereafter, the C developing device 402 continues to develop the C electrostatic latent image area, but when the rear end of the C electrostatic latent image passes, the revolver developing unit 400 The rotation operation is performed, and the next M developing device 403 moves to the developing position. This is also completed before the leading end of the next M electrostatic latent image reaches the developing position.
[0056]
Next, the M image forming step and the Y image forming step are performed in the same manner as the above-described Bk image forming step and C image forming step. The Bk, C, M, and Y toner images sequentially formed on the photosensitive drum 100 are sequentially transferred onto the intermediate transfer belt 501 while being aligned on the same surface. As a result, a full-color image is formed on the intermediate transfer belt 501 in which toners of up to four colors are superimposed.
[0057]
At the time when the image forming operation is started, the transfer paper P is fed from a paper feed unit such as a transfer paper cassette (not shown) or a manual feed tray, and stands by at the nip of the pair of registration rollers 650. When the leading end of the toner image on the intermediate transfer belt 501 approaches the secondary transfer portion where the nip is formed by the secondary transfer facing roller 510 and the secondary transfer bias roller 605, the leading end of the transfer paper P is just The registration roller pair 650 is driven so as to coincide with the leading end, and registration of the transfer sheet P with the toner image is performed.
[0058]
Then, the transfer paper P is superimposed on the toner image on the intermediate transfer belt 501 and passes through the secondary transfer portion. At this time, the transfer bias applied to the secondary transfer bias roller 605 by the secondary transfer power supply 802 causes the four-color superimposed toner image on the intermediate transfer belt 501 to be collectively transferred onto the transfer paper.
[0059]
The transfer paper P is discharged by the transfer paper discharging charger 606 disposed on the downstream side of the secondary transfer section in the moving direction of the secondary transfer belt 601, is separated from the secondary transfer belt 601, and is sent to the fixing unit. . The transfer sheet P has a toner image fused and fixed by a fixing unit, is sent out of the apparatus main body by a discharge roller pair (not shown), and is stacked face up on a copy tray (not shown) to obtain a full-color copy.
[0060]
On the other hand, the surface of the photoconductor drum 200 after the belt transfer is neutralized by the neutralization unit 202 and is cleaned by the photoconductor cleaning device 210. Further, the toner remaining on the surface of the intermediate transfer belt 501 after the transfer of the toner image onto the transfer paper P is cleaned by a belt cleaning blade 504 pressed against the intermediate transfer belt 501 by a separation / contact mechanism (not shown).
[0061]
Here, at the time of the repeat copy, the operation of the color scanner and the image formation on the photosensitive drum 200 are performed at a predetermined timing following the image formation process of the fourth color (Y) of the first sheet. Proceed to the image forming step (Bk). Further, in the intermediate transfer belt 501, the second Bk toner image is transferred to the area of the front surface cleaned by the belt cleaning blade 504 following the batch transfer process of the first four-color superimposed toner image onto the transfer paper. The belt is transferred. After that, the operation becomes the same as that of the first sheet.
[0062]
The above operation is a copy mode for obtaining a four-color full-color copy. In the three-color copy mode and the two-color copy mode, the same operation as described above is performed for the designated color and the number of times.
[0063]
Further, in the case of the single color copy mode, until the operation of obtaining a predetermined number of copies is completed, only the developing device of the predetermined color of the revolver developing unit 400 is in the developing operation state, and the belt cleaning blade 504 is moved to the intermediate transfer belt. The copy operation is performed with the position kept pressed to the position 501.
[0064]
In the fifth embodiment, the intermediate transfer belt 501 is moved by any one of the first to fourth embodiments, and the secondary transfer belt 601 serving as a transfer material conveying belt is moved by one of the first to fourth embodiments. Moved by one. In this case, an encoder scale (marker) 911 is provided on the intermediate transfer belt 501 and the secondary transfer belt 601 for one round along the moving direction of the intermediate transfer belt 501 and the secondary transfer belt 601 as in the above embodiment. Note that only one of the intermediate transfer belt 501 and the secondary transfer belt 601 may be moved according to any one of the first to fourth embodiments.
[0065]
According to the fifth embodiment, the intermediate transfer belt 501 and the secondary transfer belt 601 are moved by any one of the first to fourth embodiments. It is possible to prevent the image forming apparatus from going down during the period in which the belt is replaced, and it is possible to suppress color misregistration.
2. Description of the Related Art Today, in the electrophotographic apparatus, color copiers, color printers, and the like are increasing in color in response to market requirements.
A color electrophotographic apparatus is provided with a plurality of color developing devices around a single photoreceptor, and a toner is attached to the photoreceptor by these developing devices to form a synthetic toner image on the photoreceptor, and the toner image is formed. A color image is recorded on a sheet by transferring the image onto a sheet. A so-called one-drum type is provided, and a plurality of photoconductors arranged side by side are provided with individual developing devices, and a single color toner image is formed on each photoconductor. In addition, there is a so-called tandem type in which a composite color image is recorded on a sheet by sequentially transferring the single-color toner images on a sheet.
[0066]
Comparing the one-drum type color electrophotographic apparatus and the tandem type color electrophotographic apparatus, the former has a single photoreceptor, and therefore has the advantages of being relatively compact and capable of reducing costs. Since full-color images are formed by repeating image formation a plurality of times (usually four times) using one photoconductor, it is difficult to speed up image formation. The latter, on the other hand, has the disadvantage of increasing the size and increasing the cost, but has the advantage that the speed of image formation is easy.
[0067]
Recently, tandem-type electrophotographic apparatuses have been receiving attention because full-color image formation is required to be as fast as monochrome image formation.
In the tandem type electrophotographic apparatus, as shown in FIG. 9, a direct transfer in which a single color image on each photoconductor 1 is sequentially superimposed on a sheet s conveyed by a sheet conveying belt 3 by a transfer device 2 and transferred. 10 and, as shown in FIG. 10, each single-color image on each photoreceptor 1 is temporarily superimposed on an intermediate transfer member 4 by a primary transfer device 2 and then transferred to the intermediate transfer member 4. And an indirect transfer type in which the image of the image is collectively transferred to the sheet s by the secondary transfer device 5. The transfer device 5 is a transfer / conveyance belt, but may have a roller shape.
[0068]
Comparing the direct transfer type and the indirect transfer type, the former shows that the sheet feeder 6 is disposed upstream of the tandem type image forming unit T in which the photoconductors 1 are arranged, and the tandem type image forming unit T The fixing device 7 must be disposed on the downstream side, and there is a disadvantage that the size increases in the sheet conveying direction.
On the other hand, in the case of the latter, the secondary transfer position can be relatively freely set, and the sheet feeding device 6 and the fixing device 7 can be arranged so as to overlap the tandem image forming unit T, so that the size can be reduced. There are advantages.
[0069]
In the former case, the fixing device 7 is disposed close to the tandem-type image forming unit T in order to prevent the fixing device 7 from being enlarged in the sheet conveying direction. For this reason, the fixing device 7 cannot be arranged with a sufficient margin to allow the sheet s to bend, and the impact when the leading edge of the sheet s enters the fixing device 7 (particularly remarkable for a thick sheet) and the sheet There is a disadvantage that the fixing device 7 tends to affect the image formation on the upstream side due to the speed difference between the sheet conveyance speed when s passes through the fixing device 7 and the sheet conveyance speed by the sheet conveyance belt 3.
[0070]
On the other hand, in the latter, since the fixing device 7 can be arranged with a sufficient margin to allow the sheet s to bend, the fixing device 7 can hardly affect image formation.
In view of the above, attention has recently been paid to a tandem type electrophotographic apparatus, particularly an indirect transfer type.
[0071]
In this type of color electrophotographic apparatus, as shown in FIG. 10, the transfer residual toner remaining on the photoconductor 1 after the primary transfer is removed by the photoconductor cleaning device 8 to clean the surface of the photoconductor 1, and the re-transfer is performed again. Prepared for image formation. Further, the transfer residual toner remaining on the intermediate transfer member 4 after the secondary transfer is removed by the intermediate transfer member cleaning device 9 to clean the surface of the intermediate transfer member 4 and prepare for the image formation again.
[0072]
Hereinafter, a sixth embodiment of the present invention will be described with reference to the drawings. The sixth embodiment is an embodiment of a copying apparatus as an image forming apparatus including a tandem-type indirect transfer type color electrophotographic apparatus.
FIG. 11 shows the whole of the sixth embodiment. In FIG. 11, reference numeral 91 denotes a copying apparatus main body, 92 denotes a paper feed table on which the copying apparatus main body 91 is placed, 93 denotes a scanner mounted on the copying apparatus main body 91, and 94 denotes an automatic document feeder mounted on the scanner 93 ( (ADF).
[0073]
An endless belt-shaped intermediate transfer body 10 is provided at the center of the copying apparatus main body 91. As shown in FIG. 12, the intermediate transfer belt 10 has, as the base layer 11, a base layer made of a material such as a low-elongation fluororesin or a high-elongation rubber material provided with a non-elongation material such as canvas. The elastic layer 12 is provided thereon. The elastic layer 12 is made of, for example, fluorine-based rubber or acrylonitrile-butadiene copolymer rubber. The surface of the elastic layer 12 is covered with a coat layer 13 having good smoothness, for example, coated with a fluorine-based resin.
[0074]
As shown in FIG. 11, the intermediate transfer belt 10 is wound around three support rollers 14, 15, and 16 and is rotatable and conveyable clockwise in the figure. An intermediate transfer body cleaning device 17 for removing residual toner remaining on the intermediate transfer belt 10 after image transfer is provided to the left of the second support roller 15 among the support rollers 14, 15, and 16.
[0075]
A plurality of colors, for example, yellow, cyan, magenta, and black are provided on a portion of the intermediate transfer belt 10 extending between the first support roller 14 and the second support roller 15 along the transport direction. The image forming units 18Y, 18C, 18M, and 18K for forming the four monochromatic images are arranged side by side to form a tandem image forming unit 20. An exposure device 21 is provided on the tandem image forming unit 20.
[0076]
On the other hand, a secondary transfer device 22 is disposed on the opposite side of the tandem image forming unit 20 between both sides of the intermediate transfer belt 10. The secondary transfer device 22 is configured by, for example, a secondary transfer belt 24, which is an endless transfer material transport belt, being stretched between two rollers 23, and a third support roller 16 via an intermediate transfer belt 10. The image on the intermediate transfer belt 10 is transferred to a sheet as a transfer material as described later.
A fixing device 25 for fixing an image on a sheet is provided beside the secondary transfer device 22. The fixing device 25 is configured by pressing a pressure roller 27 against a fixing belt 26 which is an endless belt.
[0077]
The above-described secondary transfer device 22 also has a sheet conveying function of conveying the sheet after image transfer to the fixing device 25. Of course, a transfer roller or a non-contact charger may be provided as the secondary transfer device 22.
In the sixth embodiment, below the secondary transfer device 22 and the fixing device 25, a sheet reversing device 28 for reversing a sheet to record an image on both sides of the sheet is provided in parallel with the tandem image forming unit 20 described above. ing.
[0078]
When copying a document using the color electrophotographic apparatus of the sixth embodiment, the document is set on the document table 30 of the automatic document feeder 94. Alternatively, the automatic document feeder 94 is opened, a document is set on the contact glass 32 of the scanner 93, and the automatic document feeder 94 is closed to hold the document on the contact glass 32.
[0079]
When a start switch (not shown) is pressed, when an original is set on the original platen 30 of the automatic document feeder 94, the automatic document feeder 94 conveys the original on the original platen 30 to a predetermined position on the contact glass 32. Immediately after the original is set on the contact glass 32 of the scanner 93 after the setting, the scanner 300 is driven, and the first traveling body 33 and the second traveling body 34 travel, and are held by the first traveling body 33. A light source illuminates the original on the contact glass 32 and the reflected light is reflected by a mirror held by the first traveling body 33 and a mirror held by the second traveling body 34 and then passes through the imaging lens 35. The original image is read by being incident on the reading sensor 36 and color-separated into a plurality of colors and photoelectrically converted. It is.
[0080]
When the start switch is pressed, one of the support rollers 14, 15, and 16 is rotationally driven as a drive shaft by a drive motor (not shown), whereby the intermediate transfer belt 10 is rotationally conveyed, and the other two support rollers are driven. Is driven to rotate. At the same time, the individual image forming units 18Y, 18C, 18M, and 18K form monochromatic images of black, yellow, magenta, and cyan on the photoconductors 40Y, 40C, 40M, and 40K, respectively. Then, as the intermediate transfer belt 10 rotates and conveys, the single-color images on the photoconductors 40Y, 40C, 40M, and 40K are sequentially superimposed on the intermediate transfer belt 10 and transferred to form a composite color image.
[0081]
On the other hand, when the start switch is pressed, one of the plurality of paper feed rollers 42 in the paper feed table 200 is selectively driven to rotate, and the plurality of paper feed cassettes 44 provided in the paper bank 43 in multiple stages are rotated. A sheet as a transfer material is fed from one of them. These sheets are separated one by one by a separation roller 45 and enter a paper feed path 46, are conveyed by a conveyance roller 47, are guided to a paper feed path 48 in a copying machine main body 91, stop against a registration roller 49 and stop. . Alternatively, the sheet feed roller 50 rotates to feed out the sheet on the manual feed tray 51, and the sheets are separated one by one by a separation roller 52, enter the manual feed path 53, hit the registration roller 49 and stop.
[0082]
The registration roller 49 rotates in synchronization with the composite color image on the intermediate transfer belt 10, and feeds a sheet between the intermediate transfer belt 10 and the secondary transfer device 22. A color image is recorded on the sheet by transferring the composite color image on the intermediate transfer belt 10 by the secondary transfer device 22.
[0083]
The sheet after the image transfer is conveyed by the secondary transfer device 22 and sent to the fixing device 25, where the image is fixed by applying heat and pressure by the fixing device 25, and is usually switched by the switching claw 55. The sheet is discharged by a discharge roller 56 and stacked on a sheet discharge tray 57. Further, in the double-sided mode, the sheet from the fixing device 25 is switched by the switching claw 55 and put into the sheet reversing device 28, where the sheet is reversed and conveyed to the registration roller 49 again. The sheet is fed between the intermediate transfer belt 10 and the secondary transfer device 22 by the registration roller 49, and the composite color image on the intermediate transfer belt 10 is transferred to the back surface by the secondary transfer device 22. The transfer image is fixed by 25 and is discharged onto a discharge tray 57 by a discharge roller 56 via a switching claw 55.
[0084]
The residual toner is removed from the intermediate transfer belt 10 after the image transfer by the intermediate transfer body cleaning device 17 and the tandem image forming unit 20 prepares for the second image formation.
Here, the registration roller 49 is generally often used with being grounded, but it is also possible to apply a bias for removing paper dust from the sheet.
[0085]
Now, in the tandem image forming section 20 described above, the individual image forming units 18Y and 18C include charging devices 60Y and 60C and a developing device 61Y around drum-shaped photoconductors 40Y and 40C, for example, as shown in FIG. , 61C, primary transfer devices 62Y and 62C, photoreceptor cleaning devices 63Y and 63C, and static eliminators 64Y and 64C.
[0086]
The photoconductors 40Y and 40C are driven to rotate by driving units (not shown), are uniformly charged by the charging devices 60Y and 60C, and are exposed by the exposure device 21 in accordance with image signals of yellow and cyan from the scanner 93 by the exposure device 21. Each is exposed to light L to form an electrostatic latent image. The electrostatic latent images on the photoconductors 40Y and 40C are developed by developing devices 61Y and 61C, respectively, and become yellow and cyan toner images, respectively, and are superimposed on the intermediate transfer belt 10 by the primary transfer devices 62Y and 62C. Transcribed. After the transfer of the toner image, the photoconductors 40Y and 40C are cleaned by the photoconductor cleaning devices 63Y and 63C and are neutralized by the neutralization devices 64Y and 64C, respectively, to prepare for the next image formation.
[0087]
Although not shown, the image forming units 18M and 18K similarly include a charging device, a developing device, primary transfer devices 62M and 62K, a photoconductor cleaning device, and a static eliminator around a drum-shaped photoconductor. In each of the image forming units 18M and 18K, the photoreceptor is rotated and driven by the driving unit and is uniformly charged by the charging device, and the exposure device 21 converts the magenta and black image signals from the scanner 93 into the image signals. Each is exposed with the corresponding exposure light L to form an electrostatic latent image. The electrostatic latent images on these photoconductors are developed by developing devices to become magenta and black toner images, respectively, and are transferred onto the intermediate transfer belt 10 by the primary transfer devices 62Y and 62C. A color image is formed by being superimposed and transferred. Further, each of these photoconductors is cleaned by a photoconductor cleaning device after the transfer of the toner image, and is neutralized by a static eliminator to prepare for the next image formation.
[0088]
In the sixth embodiment, the intermediate transfer belt 10 is moved by any one of the first to fourth embodiments, and the secondary transfer belt 24 that is a transfer material conveying belt is moved by one of the first to fourth embodiments. Moved by one. In this case, an encoder scale (marker) 911 is provided on the intermediate transfer belt 10 and the secondary transfer belt 24 for one rotation along the moving direction of the intermediate transfer belt 10 and the secondary transfer belt 24 as in the above-described embodiment. Note that only one of the intermediate transfer belt 10 and the secondary transfer belt 24 may be moved by any one of the first to fourth embodiments. When the sheet transfer belt 3 as a transfer material transfer belt is used as shown in FIG. 9 instead of the intermediate transfer belt 10, the sheet transfer belt 3 is moved by any one of the first to fourth embodiments. You may.
[0089]
According to the sixth embodiment, the intermediate transfer belt 10 and the secondary transfer belt 24 are moved by any one of the first to fourth embodiments. It is possible to prevent the image forming apparatus from going down during the period in which the belt is replaced, and it is possible to suppress color misregistration.
[0090]
【The invention's effect】
As described above, according to the present invention, even when the output signal of the marker detection unit becomes abnormal, the belt can be moved by following the belt surface target position.
Further, correction data for the eccentricity of the drive shaft and the positional deviation of one belt rotation cycle can be added to the drive shaft target position, and the position of the belt can be correctly controlled using only the output signal of the rotation state detecting means.
[0091]
Further, it is possible to easily determine whether the output signal of the marker detecting means is abnormal, and to correctly select a sensor signal to be fed back.
Further, even if an abnormality occurs in the output signal of the marker detecting means, it is possible to prevent the image forming apparatus from being shut down even during the period when the serviceman comes to replace the belt.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating functional blocks when position control is performed on a drive target according to a first embodiment of the present invention.
FIG. 2 is a diagram showing a deviation between a position when the detection angle of the rotation state detecting means is converted into a position and a belt surface target position (command 1) when the output signal of the marker detecting means is normal in the first embodiment. It is.
FIG. 3 is a diagram showing a target position to be added to a belt surface target position (command 1) in Embodiment 2 of the present invention.
FIG. 4 is a perspective view showing the first embodiment.
FIG. 5 is a block diagram illustrating a hardware configuration of a drive system according to the first embodiment.
FIG. 6 is a diagram for explaining Embodiment 3 of the present invention.
FIG. 7 is a diagram illustrating a marker according to the first embodiment.
FIG. 8 is a schematic diagram illustrating an image forming unit according to a fifth embodiment of the present invention.
FIG. 9 is a cross-sectional view illustrating an example of a tandem type direct transfer type electrophotographic apparatus.
FIG. 10 is a cross-sectional view illustrating an example of a tandem type indirect transfer type electrophotographic apparatus.
FIG. 11 is a sectional view showing the entirety of a sixth embodiment of the present invention.
FIG. 12 is a sectional view showing an intermediate transfer belt according to the sixth embodiment.
FIG. 13 is a cross-sectional view illustrating image forming units 18Y and 18C according to the sixth embodiment.
[Explanation of symbols]
901 Intermediate transfer belt
910 motor
911 marker
912 Belt sensor
913 Drive shaft encoder
921 driver
923 microcomputer
928 belt conveyor
929 Transmission system
930 Correction information creation means
931 Status detection interface
932 drive interface

Claims (6)

A drive shaft for moving the belt, transmission means for transmitting a driving force from a drive source to the drive shaft, and a marker for detecting a marker provided on the belt for recognizing a position of the belt in the moving direction Detection means, rotation state detection means for detecting the rotation state of the drive shaft, surface position control means for obtaining the difference between the output value of the marker detection means and the belt surface target position, and the surface position control means Value and the belt surface target position, and the added value is divided by a value obtained by adding the radius of the drive shaft and the thickness of the belt to obtain a drive shaft target position. A drive shaft angle control means for causing the drive source to follow the belt surface target position based on a difference from an output value of the state detection means, wherein the output signal of the marker detection means is different. Case, the belt moving device, characterized in that to follow the belt by feeding back only the output value of the rotational state detecting means to the belt surface target position. 2. The belt moving device according to claim 1, wherein the target position on the belt surface when only the output value of the rotation state detection unit is fed back is an output of the rotation state detection unit when an output signal of the marker detection unit is normal. A belt moving device that corrects the belt so as to follow the belt surface target position from a difference between the value and the belt surface target position. 2. The belt moving device according to claim 1, wherein the determination of the output signal abnormality of the marker detecting means is such that a deviation between the belt surface target position in a steady state in the belt control and the output value of the marker detecting means is a value within a predetermined range. A belt moving device, which is operated by detecting whether the belt has deviated. 2. The belt moving device according to claim 1, wherein the determination of the output signal abnormality of the marker detection unit is performed by comparing the number of the markers detected by the marker detection unit when the output signal of the marker detection unit is normal. 3. A belt moving device, wherein the change is performed when the number of the markers detected by the marker detecting means changes. An image forming apparatus of a tandem type, comprising: the belt moving device according to claim 1, wherein the intermediate transfer belt or the transfer material conveying belt is moved by the belt moving device. Forming equipment. An image forming apparatus having one photosensitive drum and an intermediate transfer belt, comprising the belt moving device according to any one of claims 1 to 4, wherein the intermediate transfer belt or the transfer material transport belt is used by the belt moving device. An image forming apparatus characterized by moving an image.

Images