JP2003241472A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To display a message by detecting damage or soiling on a transfer belt, and deciding the exchange timing of the belt. <P>SOLUTION: The image forming apparatus is equipped with a plurality of image forming means, an endless belt, a pattern detection sensor constituted of a light emitting element and a light receiving element for reading the specified pattern image formed on the endless belt by a plurality of image forming means, a sensor constituted to output a pattern detection signal when an output value in accordance with reflected light quantity received by the light receiving element of the pattern detection sensor is equal to or above a threshold, a means for electrically or mechanically correcting the registration of the respective image forming means based on the pattern detection signal, and a message display means. The endless belt is rotated once as initial action for detecting the reflected light quantity including the damage or the soiling of the endless belt before performing registration correction so as to read the reflected light quantity of the endless belt by the pattern detection sensor, and the damage/soiling is detected in accordance with the pattern detection signal at that time or the reflected light quantity received by the light receiving element of the pattern detection sensor so as to display on a display means to exchange the endless belt. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus adopting an electrophotographic system or an electrostatic recording system, and more particularly to an endless belt used as a transfer material carrier or an intermediate transfer member (an endless belt as a transfer material carrier). A belt and an endless belt as an intermediate transfer member are collectively referred to as a transfer belt) and are related to an image forming apparatus having a function of automatically correcting an image shift during multiple image formation.

[0002]

2. Description of the Related Art Conventionally, an electrostatic latent image on a photosensitive member is developed by irradiating a photosensitive drum with laser beam light which is light-modulated according to recording information or light from a light emitting element such as an LED, and an electrophotographic process. Has a plurality of recording devices for transferring an image to a transfer paper or an intermediate transfer belt, and the transfer material conveying belt sequentially conveys the transfer paper to each recording device to perform multiple transfer of each image on the transfer paper, or an intermediate transfer belt. There has been proposed an image forming apparatus capable of forming a color image by a method in which each image is multiply transferred and then collectively transferred to a transfer paper.

In this type of image forming apparatus, the image is formed on each photosensitive drum due to a mechanical mounting error between the photosensitive drums, an optical path length error of each laser beam, an optical path change, a warp due to an environmental temperature of the LED, and the like. Further, the registration of each color image becomes inconsistent on the transfer material finally subjected to multiple transfer. For this reason, a photosensor reads the registration correction pattern image formed on the transfer belt from each photosensitive drum, detects the registration deviation on the photosensitive drum corresponding to each color, and outputs the image signal to be recorded as an electrical signal. Correction, and a folding mirror provided in the optical path of the laser beam is driven to correct the change in the optical path length or the change in the optical path.

Various patterns have been proposed for the registration correction pattern image.
In the '98810 publication, a first line segment arranged at a predetermined angle with a process direction, which is a moving direction of a transfer belt, and a second line segment symmetrically arranged with an imaginary line orthogonal to the first line segment intersecting the process direction. A pattern consisting of line segments has been proposed. Such a registration correction pattern image is read by a photosensor including an LED and a light emitting element such as a phototransistor and a light receiving element. Two of these photosensors are arranged at a predetermined distance in the direction orthogonal to the process direction, and the registration correction pattern image is also formed so as to pass over the photosensor. FIG. 8 shows how the photosensors 60 and 61 detect the registration correction pattern 203 on the transfer belt 31. It should be noted that the transfer belt 31 is made of a material whose reflectance of light (eg infrared light) emitted by the LED 201 in the photosensors 60 and 61 is higher than that of the pattern 203. Enables pattern detection.

FIG. 8 shows how the phototransistor 202 receives the light emitted by the LED 201 and reflected by the pattern 203 or the transfer belt 31, and FIG. 7 shows the phototransistor 202 receiving the reflected light and converting it into an electric signal. The following shows a light receiving circuit. First, when the transfer belt 31 is detected, the amount of reflected light is large, so a large amount of photocurrent flows through the phototransistor 202, and current-voltage conversion is performed by the resistor 407 and amplification is performed by the resistors 402 to 404 and the operational amplifier 401. When the pattern 203 is detected, the amount of reflected light is small, so a photocurrent smaller than that in the transfer belt 31 flows in the phototransistor 202.
Voltage-converted resistors 402-404 and operational amplifier 401
Is amplified by. The state in which the light receiving circuit detects the reflected light in the order of the transfer belt portion → the pattern portion → the transfer belt portion is shown in FIG.
01. By setting the threshold value level to a predetermined level between the transfer belt detection level and the pattern detection level by the electronic volume 406 capable of changing the threshold level, that is, by comparing the current-voltage converted value with this threshold level by the comparator 405, the pattern is obtained. The sensing output 302 can be produced. This pattern detection output 302 that is sequentially sent is read, registration deviation is detected from the pattern interval, etc., the image signal to be recorded is electrically corrected, and the folding mirror provided in the laser beam optical path is driven. Then, the optical path length change or the optical path change is corrected.

[0006]

However, when the endless belt has scratches or stains, the pattern formed cannot be discriminated from the scratches, and normal registration correction cannot be performed, resulting in a large deviation in registration. There were times when it ended up.

The present invention has been made in view of the above problems, and an image forming apparatus capable of detecting scratches and dirt on the transfer belt, determining the belt replacement timing, and displaying a message. Is intended to provide.

[0008]

In order to solve the above problems, the present invention has the following constitution.

At least a plurality of image forming means for forming a visible image (toner image) on a photosensitive member by an electrophotographic method or an electrostatic recording method, and a driving roller which is in proximity to the image forming means and which transmits rotational drive. An endless belt stretched and driven by one driven roller, a pattern detection sensor including a light emitting element and a light receiving element for reading a predetermined pattern image formed on the endless belt by the plurality of image forming means, A sensor configured to output a pattern detection signal when the output value corresponding to the amount of reflected light received by the light receiving element of the pattern detection sensor is equal to or more than a threshold value, and the registration of each image forming unit based on the pattern detection signal. In an image forming apparatus having a registration correction unit that electrically or mechanically corrects an error, A detection means for displaying an error message, a means for prohibiting the operation of the machine when an error occurs, and detecting the amount of reflected light including scratches or dirt on the endless belt before performing the registration correction. The endless belt is rotated once as an initial operation for reading the amount of reflected light of the endless belt by the pattern detection sensor, and the output signal of the pattern detection signal or the amount of reflected light received by the light receiving element of the pattern detection sensor at that time is read. In response, the error detecting means detects an error, prohibits the operation of the machine, and displays an error message on the display means.

The above-mentioned structure is shown again in the following (1) to (5).

(1) A plurality of image forming means for forming a visible image (toner image) on a photosensitive member by an electrophotographic method or an electrostatic recording method, and a drive which is close to the image forming means and transmits rotational drive. A pattern detection including an endless belt stretched and driven by a roller and at least one driven roller, and a light emitting element and a light receiving element for reading a predetermined pattern image formed on the endless belt by the plurality of image forming means. A sensor, a sensor configured to output a pattern detection signal when the output value corresponding to the amount of reflected light received by the light receiving element of the pattern detection sensor is equal to or greater than a threshold value, and each image forming unit based on the pattern detection signal. In an image forming apparatus having a registration correction unit that electrically or mechanically corrects the registration, A display means for displaying a message,
Before performing the registration correction, the endless belt is rotated once as an initial operation for detecting the amount of reflected light including scratches and dirt on the endless belt, and the amount of reflected light of the endless belt is read by the pattern detection sensor. According to the output signal of the pattern detection signal or the amount of reflected light received by the light receiving element of the pattern detection sensor, a scratch / dirt on the endless belt is detected and a message is displayed on the display means to replace the endless belt. A characteristic image forming apparatus.

(2) The amount of reflected light is detected during one rotation of the endless belt, and when a value larger or smaller than a predetermined reflection is detected by a predetermined number or more, a scratch / dirt on the endless belt is detected and the display is made. The image forming apparatus according to (1) above, wherein a message is displayed on the means to replace the endless belt.

(3) When the pattern detection signal is output a predetermined number of times or more during one rotation of the endless belt, a scratch / dirt on the endless belt is detected and a message is displayed on the display means to replace the endless belt. The image forming apparatus described in (1) above is displayed.

(4) The image forming apparatus as described in (1) above, wherein the endless belt is used as a transfer material conveying means.

(5) The image forming apparatus according to (1), wherein the endless belt is used as an intermediate transfer belt.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below based on examples with reference to the drawings.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of an image forming apparatus embodying the present invention. The image forming apparatus of this embodiment is an electrophotographic system, and a color image output apparatus will be described in which a plurality of image forming units in which the present invention is considered to be particularly effective are arranged in parallel.

The color image forming apparatus comprises an image reading section 1R and an image output section 1P. The image reading unit 1R optically reads a document image, converts it into an electric signal, and sends it to the image output unit 1P, but a detailed description thereof will be omitted.

The image output section 1P is roughly classified into the image forming section 1
0 (four stations a, b, c, and d are arranged in parallel and have the same configuration), a sheet feeding unit 20, an intermediate transfer unit 30, a fixing unit 40, and a control unit 70.

Further, each unit will be described in detail. The image forming unit 10 has the following configuration. Photosensitive drums 11a and 11b as image carriers,
11c and 11d are pivotally supported at their centers, and are rotationally driven in the direction of the arrow. The primary chargers 12a, 12b, 12 face the outer peripheral surfaces of the photosensitive drums 11a to 11d in the rotation direction thereof.
c, 12d, optical systems 13a, 13b, 13c, 13d,
The folding mirrors 16a, 16b, 16c, 16d and the developing devices 14a, 14b, 14c, 14d are arranged. In the primary chargers 12a to 12d, the photosensitive drum 11
A uniform amount of charge is applied to the surface of a to 11d. Then, by the optical systems 13a to 13d, a light beam such as a laser beam modulated according to the recording image signal is applied to the photosensitive drum 1.
An electrostatic latent image is formed there by exposing on 1a-11d. Further, developing devices 14a to 14d that respectively store four color developers of yellow, cyan, magenta, and black (hereinafter, referred to as toners) are stored.
To visualize the electrostatic latent image. Image transfer regions Ta, Tb for transferring the visualized visible image to the intermediate transfer member,
On the downstream side of Tc and Td, the cleaning devices 15a, 1
Toner left on the photosensitive drums 11a to 11d without being transferred to the transfer material by 5b, 15c, and 15d is scraped off to clean the drum surface. By the process described above, image formation with each toner is sequentially performed.

The paper feeding unit 20 includes cassettes 21a and 21b for storing the recording material P and a manual feed tray 2.
7. Recording material P from the cassette or the manual feed tray 27
Pick-up roller 22a for sending out one by one,
22b and 26, pickup rollers 22a and 22
b and 26, the paper feed roller pair 23 and the paper feed guide 24 for transporting the recording material P to the registration rollers, and the recording material P to the secondary transfer area Te in accordance with the image forming timing of the image forming unit 10. It is composed of registration rollers 25a and 25b for sending out to.

The intermediate transfer unit 30 will be described in detail. The intermediate transfer belt 31 (the material thereof is, for example, P
ET [polyethylene terephthalate] and PVdF [polyvinylidene fluoride] are used) to apply an appropriate tension to the intermediate transfer belt 31 by a driving roller 32 for transmitting drive to the intermediate transfer belt 31 and a spring (not shown). The applied tension roller 33 and the driven roller 34 which faces the secondary transfer area Te with the belt interposed therebetween are wound around. Of these, the primary transfer plane A is formed between the drive roller 32 and the tension roller 33. The drive roller 32 is a metal roller whose surface is coated with rubber (urethane or chloroprene) having a thickness of several mm to prevent slippage with the belt. The drive roller 32 is rotationally driven by a pulse motor (not shown). In the primary transfer areas Ta to Td where the photosensitive drums 11a to 11d and the intermediate transfer belt 31 face each other, a primary transfer charger 35a is provided on the back side of the intermediate transfer belt 31.
~ 35d are arranged. A secondary transfer roller 36 is arranged so as to face the driven roller 34, and forms a secondary transfer area Te by a nip with the intermediate transfer belt 31. The secondary transfer roller 36 is pressed against the intermediate transfer body with an appropriate pressure. Further, on the intermediate transfer belt 31, downstream of the secondary transfer area Te, a cleaning unit 50 (a blade 51 and a waste toner box 5 for storing waste toner) for cleaning the image forming surface of the intermediate transfer belt 31.
2) is provided.

The fixing unit 40 includes a fixing roller 41a having a heat source such as a halogen heater therein, a roller 41b which is pressed against the fixing roller 41b (this roller may also have a heat source), and a nip between the roller pair. Guide 43 for guiding the transfer material P to the sheet, fixing heat insulating covers 46 and 47 for confining heat of the fixing unit 40 inside, and further guiding the transfer material P discharged from the roller pair to the outside of the apparatus. The internal discharge rollers 44, the external discharge rollers 45, the discharge tray 48 on which the transfer material P is stacked, and the like.

The control unit 70 comprises a CPU 801 for controlling the operation of the mechanism in each unit, a motor driver section 802, a laser driver 808 for driving a laser for recording an image on a photoconductor, and the like.

Next, description will be added according to the operation of the apparatus.

When the image forming operation start signal is issued from the CPU 801, the paper feeding operation is started from the paper feeding stage selected according to the selected paper size and the like. For example, when the paper is fed from the upper paper feed stage, first, the transfer material P is sent out one by one from the cassette 21a by the pickup roller 22a. Then, the transfer material P is guided between the paper feed guides 24 by the paper feed roller pair 23 and conveyed to the registration rollers 25a and 25b. At that time, the registration rollers 25a and 25b are stopped, and the leading end of the paper hits the nip portion. Thereafter, the registration rollers 25a and 25b start rotating at the timing when the image forming unit 10 starts forming an image. The timing of this rotation is set so that the transfer material P and the toner image primarily transferred from the image forming unit 10 onto the intermediate transfer belt 31 coincide with each other in the secondary transfer area Te.

On the other hand, in the image forming unit 10, when the image forming operation start signal is issued, the toner image formed on the photosensitive drum 11d, which is the most upstream in the rotation direction of the intermediate transfer belt 31, by the above-described process is high. By the primary transfer charger 35d to which a voltage is applied, the primary transfer area T
At d, the image is primarily transferred to the intermediate transfer belt 31. The primary-transferred toner image is conveyed to the next primary transfer area Tc. There, the image formation is performed with a delay between the image forming units by the time when the toner image is conveyed, and the next toner image is transferred by aligning the resist on the previous image. The same steps are repeated below, and eventually the four color toner images are primarily transferred onto the intermediate transfer belt 31.

After that, when the recording material P enters the secondary transfer area Te and comes into contact with the intermediate transfer belt 31, a high voltage is applied to the secondary transfer roller 36 in synchronization with the passage timing of the recording material P. Then, the four color toner images formed on the intermediate transfer belt 31 by the above-described process are transferred to the surface of the recording material P. After that, the recording material P is accurately guided to the fixing roller nip portion by the conveyance guide 43. Then, the toner image is fixed on the paper surface by the heat of the roller pair 41a and 41b and the pressure of the nip. Thereafter, the paper is conveyed by the inner and outer paper discharge rollers 44 and 45, the paper is discharged to the outside of the machine, and is stacked on the paper discharge tray 48.

Next, the registration correction operation will be described with reference to the control unit block diagram of FIG. 5A and the light receiving circuit of FIG. Control unit 70 of FIG. 5 (a)
Is a CPU 801 that controls the image output unit 1P, a ROM 806 that stores a control program and data, a RAM 803,
Display means (LCD or the like) 80 for displaying an error message
9, a motor driver unit 802 that drives various motors,
A light receiving circuit 807 that receives the outputs from the photosensors 60 and 61 and converts the waveform into a waveform that can be processed by the pattern width shaping unit, a pattern width shaping unit 804 that shapes the pattern width by receiving the output from the light receiving circuit 807, the pattern width and position. Pattern width & position storage unit (registers D to S) 80 for storing
5. A laser driver 808 that controls the amount of laser light by the CPU 801 and performs lighting control according to image data.
When the registration correction operation starts according to an instruction from the CPU 801, and the registration pattern is detected, the photo sensor 6
It is converted into an electric signal by 0 and 61 and the light receiving circuit 807, and is input to the pattern width shaping unit 804 and the CPU 801. The light receiving portion analog signal input to the CPU 801 is a signal obtained by amplifying the reflected light amount of the transfer belt converted into a voltage by the phototransistor 202 with a predetermined gain by the operational amplifier 401 as shown in FIG. The pattern detection signal input to the CPU 801 is obtained by comparing the analog signal of the light receiving portion with the comparator 4
The pattern detection output signal is waveform-shaped by using the output of the electronic volume 406 set by the CPU 801 by 05 as a threshold value. CP in the pattern width shaping unit 804
Only when the pattern detection output continues for a predetermined width T or more set by the U801, it is determined that the pattern is a pattern, and the pattern width and the pattern position are stored in the pattern width & position storage unit (register) 805. Based on the stored data, the registration deviation on the photosensitive drum corresponding to each color is calculated using the table stored in the CPU 801 and the ROM 806, and the image signal to be recorded is electrically corrected and the laser beam is corrected. The folding mirror 16a provided in the optical path is driven (the motor is driven by the motor driver 802 to control the mirror) to correct the optical path length change or the optical path change. As the detection means for detecting the registration correction pattern image, the same photosensors 60 and 61 as in the conventional example of FIG. 8 are used.

Next, the intermediate transfer belt 31 in the present embodiment.
The control method of the scratch / dirt detection of is described. FIG. 3A shows a change in the amount of reflected light detected by the CPU 801 when the intermediate transfer belt 31 is rotated once as an initial operation.

Before the registration correction pattern is output, the intermediate transfer belt 31 is rotated once to receive the reflected light amount signal of the intermediate transfer belt 31 from the photosensors 60 and 61 at the light receiving portion 807, and the operational amplifier 401 performs a predetermined amplification. After that, it is input to the AD input terminal of the CPU 801 as a light receiving portion analog signal. The CPU 801 compares the reflected light amount value of the intermediate transfer belt 31 input to the AD input terminal with a predetermined belt reflected light amount threshold value (dotted line in FIG. 3A), and detects a small value a predetermined number of times ( If it is more than three times in this embodiment), the CPU 801 displays a message for replacing the transfer belt 31 to notify the user that the registration correction operation cannot be performed successfully. In the example of FIG. 3A, the two times in the figure are below the threshold value, but the warning message is not displayed because it is two times. As a result, the user can be notified when the amount of reflected light of the intermediate transfer belt 31 is reduced due to dirt or scratches on the intermediate transfer belt 31 and the registration correction operation does not operate normally. Here, the belt reflected light amount threshold value is set to a minimum value that allows a normal registration correction operation.

Next, the registration correction operation sequence will be described with reference to the flowchart of FIG. CPU
801 performs the registration correction operation at the timing when image formation can be performed, for example, when the power of the image forming apparatus is turned on or after a predetermined time has passed since the power was turned on. When the registration correction operation starts, the CPU 801 determines in f701 whether or not to perform the initial operation. The initial operation may be performed every time the registration correction operation is performed, or may be performed only at a predetermined timing such as only the registration correction operation performed after the power is turned on and the door is opened and closed. When performing the initial operation, the intermediate transfer belt 31 is rotationally driven at f708, and the sensor LED 201 is turned on at f709. Thereafter, at f710, the amount of reflected light when the intermediate transfer belt 31 is driven to rotate once is sampled at the AD input port of the CPU 801, and then the LED is turned off at f711, and f71 is set.
At 2, the CPU 801 determines whether the number of times the amount of reflected light of the intermediate transfer belt 31 is lower than a predetermined threshold value (3.5 V in this embodiment) is three times or more. The registration correction operation from step 1 is sequentially performed, and if it is three times or more, a warning message such as "Please replace the transfer belt" is displayed at f713. When the initial operation is not performed, the intermediate transfer belt 31 is rotationally driven at f702, and then the registration correction operation from f703 is sequentially performed.

Next, the registration correction operation from f703 will be described. At f703, the registration pattern image writing is started. Before the registration pattern image written on the transfer belt 31 passes through the photo sensors 60 and 61, the LED 201 is turned on (f704), and the pattern detection operation is started at f705.

At f705, as described above, the signals from the photosensors 60 and 61 are passed through the light receiving circuit 807 and the pattern width shaping section 804 for shaping the pattern width, thereby eliminating false detection signals due to scratches or dirt. The pattern width and position are sequentially stored in the registers D to S shown in the pattern width & position storage unit (register) 805. At f706, the LED 201 is turned off, the rotation of the intermediate transfer belt 31 is stopped, the pattern interval detection operation is completed, and the process proceeds to f707, where the data is recorded based on the data stored in the register, the table stored in the ROM 806, and the like. The electrical correction is performed on the power image signal, and the folding mirror 16a provided in the optical path of the laser beam is driven to correct the optical path length change or the optical path change, and the registration correction operation is completed.

For example, when the cashier pattern image as shown in FIG. 2 is read, the cashier pattern is stored. The photosensor 60 reads the pattern 501 based on the registration pattern output obtained by reading the pattern 501.
Position data and width data of registers D, E, F, G
To store. Similarly, based on the registration pattern output obtained by reading the patterns 502-504, the pattern 50
The position data and width data of 2 to 504 are stored in H to S.

Although the registration correction method in the intermediate transfer method (collective transfer method) using the intermediate transfer belt has been described in this embodiment, it is needless to say that the method is also effective in the multiple transfer method using the transfer material conveying belt. Nor.

[0038]

Second Embodiment In the first embodiment, when the intermediate transfer belt 31 is rotated once before outputting the registration correction pattern, the CPU 801 causes the electronic volume 406 to determine a predetermined minimum reflected light amount of the intermediate transfer belt 31. In the embodiment, 3.5 V) is set as the threshold value, and the threshold value of FIG.
, The reflected light amount of the transfer belt in the figure is below the threshold value 3.5V set in the electronic volume 406, and the pattern detection signal output from the operational amplifier 405 shown in FIG. Becomes The CPU 801 when the pattern detection signal generated when the amount of reflected light when the intermediate transfer belt 31 makes one rotation falls below 3.5 V set in the electronic volume is detected a predetermined number of times (three times in the embodiment) or more. The same effect can be obtained by displaying a message for replacing the transfer belt 31 and notifying the user that the registration correction operation cannot be performed successfully.

FIG. 6 shows a flowchart of this embodiment.

The CPU 801 performs the registration correction operation, for example, when the power of the image forming apparatus is turned on, or after a predetermined time has passed since the power was turned on, at a timing when image formation can be performed. When the registration correction operation starts, f901
Then, the CPU 801 determines whether to perform the initial operation.
The initial operation may be performed every time the registration correction operation is performed, or may be performed only at a predetermined timing such as only the registration correction operation performed after the power is turned on and the door is opened and closed. When performing the initial operation, the intermediate transfer belt 31 is rotationally driven at f909, and the sensor LE is driven at f910.
Turn on D201. After that, CPU 801 at f911
Sets a minimum value of 3.5 V of the reflected light amount of the intermediate transfer belt to the electronic volume 406. The pattern detection signal when the intermediate transfer belt 31 is driven to rotate once at f912 is CP.
After sampling at the input port of U801, L at f913
The ED is turned off, and at f914, the CPU 801 outputs the pattern detection signal of the intermediate transfer belt 31 a predetermined number of times (3 in this embodiment).
If it is less than 2 times, the registration correction operation from f903 is sequentially performed. If it is 3 times or more, replace the transfer belt with f915. Display a warning message. When the initial operation is not performed, the intermediate transfer belt 31 is rotationally driven at f902, and then the registration correction operation from f903 is sequentially performed.

Next, the registration correction operation from f903 will be described. First, in f903, the CPU 801 sets a threshold value (3 V in this embodiment) used for registration correction in the electronic volume 406. Then f904
Then, the registration pattern image writing is started. The registration pattern image written on the transfer belt is the photosensor 6
Before passing through 0 and 61, turn on the LED 201 (f9
05), the pattern detection operation is started at f906.

At f906, as described above, the signals from the photosensors 60 and 61 are passed through the light receiving circuit 807 and the pattern width shaping section 804 for shaping the pattern width, thereby eliminating false detection signals due to scratches or dirt. The pattern width and position are sequentially stored in the registers D to S shown in the pattern width & position storage unit (register) 805. At f907, the LED 201 is turned off, the rotational driving of the intermediate transfer belt 31 is stopped, the pattern interval detection operation is completed, and the process proceeds to f908, where the data is recorded based on the data stored in the register, the table stored in the ROM 806, and the like. The electrical correction is performed on the power image signal, and the folding mirror 16a provided in the optical path of the laser beam is driven to correct the optical path length change or the optical path change, and the registration correction operation is completed.

For example, when the registration pattern image as shown in FIG. 2 is read, the registration pattern is stored. The photosensor 60 reads the pattern 501 based on the registration pattern output obtained by reading the pattern 501.
Position data and width data of registers D, E, F, G
To store. Similarly, based on the registration pattern output obtained by reading the patterns 502-504, the pattern 50
The position data and width data of 2 to 504 are stored in H to S.

Although the registration correction method in the intermediate transfer method (collective transfer method) using the intermediate transfer belt has been described in this embodiment, it is needless to say that the method is also effective in the multiple transfer method using the transfer material conveying belt. Nor.

[0045]

Other Embodiments In the above-described Embodiments 1 and 2, the means for changing the emitted light amount of the laser in order to change the density of the registration detection pattern is taken as an example.
In a system in which the recording density can be changed by driving, the same effect can be obtained by changing the emission duty of the laser as a means for changing the density.

[0046]

As described above, before the registration correction is performed, the intermediate transfer belt is rotated once to detect the amount of reflected light from the intermediate transfer belt, and the scratches and stains on the transfer belt are detected. By notifying the user with a message display, it is possible to replace the belt at an appropriate timing before erroneous detection due to scratches and dirt on the belt occurs.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a color image forming apparatus.

FIG. 2 is a diagram showing a registration correction pattern image.

3A and 3B are diagrams showing an output when a pattern of the photo sensor of the present embodiment is read.

FIG. 4 is a flowchart of registration correction operation according to the first embodiment.

5A is a diagram showing a control unit in the embodiment, and FIG. 5B is a diagram showing a pattern width & position storage unit (register).

FIG. 6 is a flowchart of registration correction operation according to the second embodiment.

FIG. 7 is a diagram illustrating a light receiving circuit that receives an output of a photo sensor.

FIG. 8 is a diagram showing how a photo sensor reads a pattern on a transfer belt.

FIG. 9 is a diagram showing an output when a pattern of a photo sensor is read.

[Explanation of symbols]

A Primary transfer plane P Recording material Ta to Td Image transfer area (Primary transfer area) Te Secondary transfer area 1P Image output section 1R Image reading section 10 Image forming section 11a to 11d Photosensitive drum 12a to 12d Primary charger 13a to 13d Optical Units (optical system) 14a to 14d Developing devices 15a to 15d Cleaning devices 16a to 16d Folding mirror 20 Paper feeding units 21a and 21b Cassettes 22a and 22b Pickup rollers 23 Paper feeding roller pairs 24 Paper feeding guides 25a and 25b Registration rollers 26 Pickup rollers 27 Manual Feed Tray 30 Intermediate Transfer Unit 31 Intermediate Transfer Belt (Transfer Belt) 32 Drive Roller 33 Tension Roller 34 Driven Rollers 35a to 35d Primary Transfer Charger 36 Secondary Transfer Roller 40 Fixing Unit 41a Fixing Roller 41b Fixing Roller Roller 43 pressed by 41a Guide 44 Inner sheet discharge roller 45 Outer sheet discharge rollers 46, 47 Fixing heat insulating cover 48 Sheet discharge tray 50 Cleaning unit 51 Blade 52 Waste toner box 60, 61 Photo sensor 70 Control unit 201 LED 202 Photo Transistor 203 Registration correction pattern (pattern) 401 Operational amplifier 402, 403, 404, 407 Resistor 405 Comparator 406 Electronic volume 501, 502, 503, 504 Pattern 801 CPU 802 Motor driver 803 RAM 804 Pattern width shaping section (pattern forming section) ) 805 pattern width & position storage section (register) 806 ROM 807 light receiving circuit (light receiving section) 808 laser driver 809 display means (display section)

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 15/16 G03G 15/16 21/00 386 21/00 386 510 510 510 F term (reference) 2H027 DA09 DA50 DE02 DE07 DE09 EB06 EC04 EC06 ED04 ED06 EE01 EF02 GB07 HB16 2H030 AA01 AB02 AD17 BB42 BB43 BB56 BB63 2H200 FA04 GA12 GA23 GA34 GA47 GB22 GB25 HA02 HA12 HA28 HB03 HB12 PA20 J12 J20C20 J20 J20 JC03 J20 JC03 J20 JC03 J20 PB13 PB16 PB22 PB39

Claims (5)

[Claims] 1. A plurality of image forming means for forming a visible image (toner image) on a photoconductor by an electrophotographic method or an electrostatic recording method, and a drive roller which is close to the image forming means and transmits rotational drive. And a pattern detection sensor including an endless belt stretched and driven by at least one driven roller, and a light emitting element and a light receiving element for reading a predetermined pattern image formed on the endless belt by the plurality of image forming means. And a sensor configured to output a pattern detection signal when the output value corresponding to the amount of reflected light received by the light receiving element of the pattern detection sensor is equal to or more than a threshold value, and the resist of each image forming unit based on the pattern detection signal. Image forming apparatus having a registration correction means for electrically or mechanically correcting the registration, The endless belt is rotated once as an initial operation for detecting the amount of reflected light including scratches and dirt on the endless belt before the registration correction is performed. The amount of reflected light of the endless belt is read, and according to the output signal of the pattern detection signal at that time or the amount of reflected light received by the light receiving element of the pattern detection sensor, scratches / stains of the endless belt are detected and the display means displays the endless belt. An image forming apparatus, which displays a message to exchange the information. 2. The amount of reflected light during one rotation of the endless belt is detected, and when a value larger or smaller than a predetermined reflection is detected by a predetermined number or more, a flaw / dirt on the endless belt is detected and the display means. The image forming apparatus according to claim 1, wherein a message is displayed on the screen to replace the endless belt. 3. When the pattern detection signal is output a predetermined number of times or more during one rotation of the endless belt, a flaw / dirt on the endless belt is detected and a message is displayed on the display means to replace the endless belt. The image forming apparatus according to claim 1, wherein the image forming apparatus comprises: 4. The image forming apparatus according to claim 1, wherein the endless belt is used as a transfer material conveying unit. 5. The image forming apparatus according to claim 1, wherein the endless belt is used as an intermediate transfer belt.