JPS63278070A - Image forming device - Google Patents

Abstract

PURPOSE:To precisely measure color shear by discriminating the deterioration of a detection means, the deterioration of a transfer belt and the stain of the ground of a sensitive body from the ratio or the difference between respective belt texture reflection outputs. CONSTITUTION:The transfer belt texture reflection output VSG0 at the time of initially setting the detection means is previously recorded in a storage means and the belt texture reflection output VSG1 before recording in a pattern image recording part of the belt which is in a transfer ON-state, the belt texture reflection output VSG2 after the belt circuits after recording the pattern image in the same part and the belt texture reflection output VSG3 in the same part which is in a transfer OFF-state are detected at the time of recording images. Based on the result of the ratio of the difference between VSG0 and VSG1, VSG1 and VSG2, VSG2 and VSG3, the deterioration of the detection means, the deterioration of the transfer belt and the stain of the ground of the sensitive body can be discriminated. According to the relation of size with a reference value, a spot where the stain occurs is discriminated and it is displayed with a load driver 74. Thus, the color shear can be precisely measured and it can be compensated.

Description

[Detailed description of the invention] (Technical field) The present invention relates to an image forming apparatus that grows a plurality of photoreceptors.

(Prior art) In an image forming apparatus that forms color images using multiple photoreceptors, the factors that cause misalignment in the transfer paper feeding direction (vertical registration) include the installation position and circumferential speed of each photoreceptor, and the exposure to the photoreceptor. The position, linear speed of the transfer belt, etc. were configured to guarantee each component accuracy and assembly accuracy, but this resulted in high component costs and assembly costs, and due to changes in each factor over time and variations due to component replacement. Readjustment is required.

As a method to solve this problem, a method has been proposed in which the writing timing of each color is obtained by detecting the transfer paper using a sensor installed in front of each transfer position. Due to variations in the mounting position and variations in the detection position of each sensor, it has been difficult to guarantee a positional shift limit (about 0.15 m) for color images.

Furthermore, an application has already been filed by the same applicant as the present invention, which detects measurement patterns of each color on the transfer belt and measures their pitch to detect positional deviation. It may not be possible to reliably read the measurement pattern due to dirt on the sensor, variations in the sensitivity of the detection sensor, etc.

(Objective) The present invention has been made based on such a background, and provides a color image forming apparatus that obtains one color image by superimposing a plurality of color images on a transfer sheet fed by a conveyor belt. The present invention provides a digital color image forming apparatus that can reduce color misregistration in the transport direction of transfer paper for each color with a simple configuration. The purpose is to measure color shift with high precision without being affected.

(Structure) For this purpose, the present invention stores in advance the transfer belt background reflection output vseo at the time of initial setting of the detection means in the storage means, and at the time of image recording, the transfer belt background reflection output vseo is stored before recording of the pattern image recording portion of the belt in the transfer ON state. Belt skin reflection output YS1
11, the same (belt background reflection output vseg at the same part of the belt circumference after pattern image recording and belt background reflection output V!@! at the same part in the transfer OFF state are detected,
31i. and V31!1+v3.1 and vsez I vs
ez and V. The present invention is characterized in that deterioration of the detection means, deterioration of the transfer belt, and background stains on the photoreceptor are determined based on the results of the respective ratios or differences.

Hereinafter, the structure and operation of the present invention will be explained in detail based on the embodiment shown in the drawings.

First, FIG. 1 is a schematic diagram of a digital color image forming apparatus to which the present invention is applied.

In FIG. 1, a color copying machine is shown as an example of an image recording device.The copying machine includes a scanner part 1 for reading a document, and electrically processes an image signal output as a digital signal from the scanner part 1. It has an image processing section 2 and a printer section 3 that forms an image on copy paper based on image recording information of each color from the image processing section 2. The scanner part 1 includes a lamp 5 that scans and illuminates the original on the original table 4.
, with, for example, fluorescent lights. The reflected light from the document when illuminated by the fluorescent lamp 5 is reflected by the mirror 6.7.8 and enters the imaging lens 9. The imaging lens 9 forms an image of the image light on the guichroic prism 10, and the image light is separated into light of three wavelengths, for example, red R, green G, and blue B. The light is input to CCD11R for green, CGDIIG for green, and CCD1 IB for blue. Each CCDIIR, IIG
.

11B converts the incident light into a digital signal and outputs it, and the output is subjected to necessary processing in the image processing unit 2 to record color information of each color, such as black (hereinafter abbreviated as Bk), yellow (Y), etc. (abbreviation).

The signals are converted into signals for recording each color of magenta (abbreviated as M) and cyan (abbreviated as C).

Although FIG. 1 shows an example of forming four colors, Bk, Y, M, and C, it is also possible to form a color image using only three colors. In that case, the number of recording devices can be reduced by IMi compared to the example shown in FIG.

The signal from the image processing section 2 is input to the printer section 3,
12G, 1 to the laser beam emitting device 128 of each color.
Sent to 2M and 12Y.

In the illustrated example, the printer section includes four sets of recording devices 13Y, 1
3M, 13G, and 138k are arranged side by side. Since each recording device 13 is made of the same constituent members, in order to simplify the explanation, the recording device for C will be explained, and the explanations for other colors will be omitted. In addition, for each emergency, the same parts are given the same reference numerals, and in order to distinguish the composition of each color, a subscript indicating each color is added to the reference number.

The recording device f13G has a photoreceptor 14C1, for example, a photoreceptor drum, outside the laser beam emitting device 12C.

The photoreceptor 14G is provided with a charger 15C, an exposure position #i by a laser beam emitting device 12G, a developing device 16C, a transfer charger 17C, etc., as in a known copying apparatus.

Photoreceptor 1 uniformly charged by charger 15C
4G forms a cyan latent image through exposure by the laser beam emitting device 12C, and develops it by the developing device 16C to form a developed image. Copy paper is fed by a paper feed roller 18 from a paper feed unit 19, for example, one of two paper feed cassettes, and the leading edge of the copy paper is aligned by a registration roller 20 and sent to a transfer belt 21 at the same timing. Transfer belt 2
The copy sheets conveyed by 1 are sequentially sent to photoreceptors 148, 14G, 14M, and 14Y, each having a developed image formed thereon, and the developed image is transferred under the action of the transfer charger 17. The transferred copy paper is fixed by a fixing roller 22 and discharged by a paper discharge roller 23.

By being electrostatically attracted to the transfer belt 21, the copy paper can be conveyed with high precision at the speed of the transfer belt.

FIG. 2 is a front view of the transfer belt section. Transfer belt 21
is supported by a belt drive roller 24 and a driven roller 25, and moves in the A direction to convey the transfer paper. Further, the cleaning unit 26 removes toner adhering to the belt. A reflective sensor 27 is provided downstream of the photoconductor 14 in the belt movement direction as a backlight image detection means.

FIG. 3 is a system block diagram according to the embodiment.

The system controller 30 controls each module of the scanner 1, image processing section 2, and printer 3. The control contents include display control on the operation panel 31, manual key processing, and according to the mode set on the operation panel 31.
Sending start signals and scaling ratio designation signals to the scanner 1 and printer 3; image processing mode designation signals to the image processing unit 2 (color conversion, masking, trimming, mirroring, etc.)
transmission, abnormal signals from each module, operating status status signals (Wait, Ready + Buay, 5to
p, etc.) to control the entire system.

The scanner 1 scans the original at a scanning speed that matches the magnification specified by the start signal from the system controller 30, reads the original image with a reading element such as a CCD, and generates image data of 8 bits each for R, G, and B. 5-LSYNC (horizontal synchronization signal) from the image processing unit 2, S
-3TROBE (image clock), and FGATE
(vertical synchronization signal) and sends it to the image processing section 2.

The image processing unit 2 receives the R and G signals sent from the scanner l.

Image processing such as T correction, UCR (undercolor removal), and color correction is performed on each 5-bit B image data to create Y, M, and C images.

Bk is converted into 3-bit image data for each and sent to the printer 3. Also, according to commands from the system controllers 3 and 0, editing processes such as scaling, masking, trimming, color conversion, mirroring, etc. are performed.

It also has a buffer memory for outputting Y, M, C, and Bk image data shifted by the distance between the photoreceptor drums of the printer 3.

The printer 3 receives P-LSYNC (horizontal synchronization signal), P-5T, and ROBE (image clock) from the image processing unit 2.
The laser beam emitting device is modulated according to image data of 3 bits each of Y, M, C, and Bk sent in synchronization with the image data, and a copy image is obtained on transfer paper by an electrophotographic process.

FIG. 4 shows an example of the detection pattern of the present invention.

In each recording device, the pattern image visualized by the signal from the pattern image signal generating means outside the transfer area is transferred to the transfer belt 21, and as shown in FIG. They are located at intervals of . And C, M in the pattern image 288.

Y passes through the sensor 27 sequentially as the belt moves and is detected by the sensor 27. *The image interval a is a numerical value that can be arbitrarily selected by setting the exposure timing for each recording device in advance.

In the color copying machine shown in FIG. 1, the transmission of image data of each color from the image processing section 2 must be shifted by the distance between the photosensitive drums of the respective colors.

FIG. 5 is a block diagram showing the configuration of a buffer memory for this purpose and the configuration of a pattern image signal generation means.

FIG. 6 is a timing chart showing the operation of the block diagram in FIG. 5 (■=timing chart of the waveform of the part indicated by [shares]).

In the color copying machine of this embodiment, Bk and C.

Since the recording devices are arranged in the order of M and Y, the Bk image data is processed by the image processing unit 2 and output as is, and the C, M, and Y image data are , are output with a delay of Lec, To, and Tゎ, respectively.

Figure 7 shows the delay time of image data! DCn'r...
FIG. 3 is an explanatory diagram for setting T11Y.

The length from the exposure position to the transfer position for each photoconductor 14 is jl+(m), and the photoconductor linear velocity is Vt hn/sec.
), the distance between the photoreceptors is j! 1 (w+), and the transfer belt linear velocity is Vfi (m/sec), the time required from exposure to transfer, t, is the same value for each photoreceptor, t+
-11r /v+ (sec) If the time to move between each photoreceptor is t8, tt -11m /vt
(sac) That is, in order to form images of each color at the same position on the transfer paper, t se = 'j * / v x (sac) Tu
w-21z / v * (sec) TIY” 31
m/V t (sec).

As shown in FIG. 5, the circuit configurations of C, M, and Y are the same, so Bk and C will be explained. A rise detection circuit 40 detects the rise of the vertical synchronization signal FGATH sent from the scanner 1. Since the Bk, C, M, and Y inputs and FGATE are input at the same time, the output of the rise detection circuit 40 is a signal representing the start of Bk image writing. The output of the rising edge detection circuit 40 is input to a Bk pattern signal generation means 41, which outputs a detection pattern. That is, in the case of Bk, the leading edge of the image and the pattern position are the same in the moving direction of the belt 21 (FIG. 4).

The output of the rising edge detection circuit 40 is input to the reset terminal of the address counter C42a via an OR gate, and resets the address counter C42a. The input image data of C is stored in the buffer memory: C43a according to the count value of the address counter 42a.

On the other hand, the output of the address counter 42a is the comparator: C44.
a, the address setter: C45a is compared with the set value, and the output of the address counter 42a is sent to the address setter 4.
When the value matches the set value of 5M, the comparator 44a outputs a match signal. This -defeat signal is input to the reset terminal of the buffer memory 43m via an OR gate, and the output of the address counter 42a is reset to 10# to access address 0 of the buffer memory 43a again.

After reading the already stored image data, the buffer memory 43a writes newly input image data to the same address.

Here, if the setting value of the address setting device 45a is set to the drum interval (twc) of Bk and C, the
An image can be created by aligning the k and C images.

The one-defeat signal of the comparator C44a is also input to the delay device C46a, triggers the delay bag y146a, and the comparator 44
Pattern signal generating means after a certain period of time from the matching signal of a:
C47a outputs a detection pattern.

Since the defeat signal of the comparator C44a is output at the same time as the leading edge of the image of C, the detection pattern of C is outputted with a delay from the leading edge of the image by the delay time (Lec) caused by the delay device 046a.

Here, the delay device: C46a has a delay time of a(m
) If the time required for movement is set, the detection pattern C can be created with a (w) delay from the leading edge of the image, as shown in FIG.

The same goes for M and Y, and is it an address setting device? Setting value of M45b - tゎ Address setter: Setting value of Y45c - toy delay device yt: M46b
By setting the setting time of trx-2a/vl delay device: Y46c to Lpv-3a/Vz, the image light edges can be matched for each color, and at the same time the detection pattern can be set as shown in Fig. 4. It is possible to output at a (crane) pitch.

Here, if the Bk, C, M, and Y image positions shift on the transfer paper due to variations in the position of each photoconductor, variations in the exposure position with respect to the photoconductor, and variations in the linear speed of the photoconductor and transfer belt, the detection The detection pattern also shifts accordingly, and by measuring the interval between the detection patterns, the amount of positional shift of the image can be detected.

FIG. 13 shows an example of a conventional pattern detection circuit, in which the output current of a phototransistor of a reflective sensor 50 is
1 is converted into voltage. That voltage is comparator C
OMP 1 is compared with the threshold voltage V□ determined by resistors R3 and R4 to obtain a rectangular wave output.
As shown in Figure 4 (1), +21, under normal conditions, it is possible to obtain a rectangular wave output corresponding to each color pattern without any problem, but due to variations in the sensitivity of the detection sensor or dirt, the problem as shown in Figure 14 (3) If the detection output becomes like this, it will not be possible to obtain accurate rectangular wave output [see Figure 14 (4)
)] FIG. 8 shows an example of the pattern detection circuit according to the present invention, in which the output current of the phototransistor ph of the zero-reflection sensor 27 is converted into a voltage by the resistor Rt (see FIG.
Waveform of 0 part shown in a)], DC by capacitor C2
The AC component is cut off and only the AC component is taken out (waveform of the 0 part shown in Figure 10). This signal is input to the inverting amplifier AMP2 via the voltage follower AMP1, and is amplified to an appropriate voltage level. [0 part waveform shown in Figure 10 (C)], the output of AMP2 is the comparator C
Threshold voltage v determined by resistors R8 and R9 by OMPI
yH to obtain a rectangular wave output [the waveform at the 0 portion shown in FIG. I can do it. Since only the AC portion of the sensor output is amplified and used, accurate measurements can be made without being affected by sensor dirt or variations in sensitivity.

FIG. 9 shows an embodiment of the pattern interval measuring circuit. 1st
Figure 1 shows a timing chart.

CL from the CPU 60 before starting pattern interval measurement.
The output of the detection circuit which outputs the EAR signal to clear the counters CNT1 to CNT4 is input to the clock terminal of the counter CNT1, and the outputs A and B of CNT1 output the signals shown in FIG.

By ANDing (ANDI) the A output of CNT1 and a signal obtained by inverting the B output, a signal representing the pattern interval between Bk and C can be obtained.

Also, by taking the exclusive OR of A output and B output (
EORI), a signal representing the Bk and M pattern intervals can be obtained. Further, by ORing the A output and the B output (ORI), a signal representing the Bk and Y pattern intervals is obtained.

Signals representing the pattern intervals of Bk and C, Bk and M, and Bk and Y are sent to counters CNT2. It is connected to the enable inputs of CNT3 and CNT4, and the counters CNT2.
CNT3. CNT4 counts the reference clock while the enable input is 1H#, Bk and C, Bk and M, Bk
It outputs binary data proportional to the pattern interval between and Y.

CNT2. CNT3. When the counting operation of CNT4 is completed, the data selector 61 is controlled by the 5ELO and 5ELI outputs of the CPU 60 to sequentially count CNT2. C
NT3. FIG. 12(a) shows a flowchart of the above operation in which the binary data of the CNT4 is taken into the CPU 60.

The CPU 60 compares the captured output value of the counter with a reference value, calculates the difference between the reference value and the measured value, and outputs correction signals C, M, and Y for correcting the difference. This correction signal is sent to the address setter: C, M, Y45 shown in FIG.
By changing the timing at which images are written for Bk, alignment of images of each color can be realized.

Now, if the frequency of the reference clock is F (Hz), then Bk
C, M, Y pattern spacing Lc, L, , L with reference to
v is Lc - (Kc /F)Xvz (m)LM - (K
N /F)Xvm (m)t,v-(Kma/F)XV
Snow (Tsuru) (However, Kc, , Kv is the measured clock number), therefore, the deviation from the set value of each pattern interval Dc, D
, 1. Dv becomes Dc=Lc −a (M) DN −LM −2a (m) I) YmLv−3a (day).

The correction signal Hc l HN + Hy is Dc, D,, Dv
is multiplied by a count for converting the amount of deviation on the belt into a memory address, Hc=CXDc HH-CXD becomes 1 (y=CX Dv). The above calculation process is shown in FIGS.

In the present invention, the detection patterns are arranged at intervals of a (m), Bk and C, with the front edge of each color image as a reference.

Created in the order of M and Y. a (m) means that when the belt speed is as per the design value, it becomes a (same), and if the belt speed deviates from the design value due to parts variations etc., the pattern interval a' (w
) is a' - (v, I/v value) Xav: Design value of belt speed v, # * Actual value of belt speed.

However, the time t for detection by the detection sensor is t = a
' / v い' den a / V! Therefore, the pattern spacing can be accurately measured regardless of the actual belt speed.

By the way, the detection control using the photosensor as described above is
As time passes, the detection SN ratio decreases due to stains on the photo sensor, belt stains due to poor belt cleaning, background stains generated on the photoconductor during development, or transferred onto the belt due to poor photoconductor cleaning. There is a risk that the detection level may deteriorate and false detection may occur more easily.

Therefore, in the present invention, the belt surface output is read at each timing to read the location where dirt is occurring.

As shown in FIG. 15, the background reflection output of the transfer belt is taken out at ■, and the OUT at ■ is a rectangular wave output for detecting positional deviation.

At the initial setting level of the sensor 27 (with no dirt on the sensor, belt, photoreceptor, etc.), adjust Vm so that the belt background reflection output level becomes an arbitrary voltage at ■.
Adjust 1. The belt skin reflection output at that time is v3°. shall be.

FIG. 16 shows the amount of light reflected from the belt surface at the image recording area, and
A timing chart when detecting the amount of pattern image reflected light is shown.

Prior to detecting a pattern image to detect positional deviation or toner adhesion amount, the belt background reflection output of the same belt portion is set to Vs before one rotation of the pattern image detection portion of the belt.
*l (At this time, the transfer is ON), the belt reflection output of the same belt part after one rotation of the belt at the pattern image detection part of the belt is set to Vs.(The transfer is ON at this time as well),
Furthermore, the belt reflection output of the same belt portion after one more rotation is assumed to be vl, 3 (at this time, the transfer is 0FF).

FIG. 17 is a block diagram for inputting the belt background output detected above and finally determining the location where stains occur on the sensor, transfer belt, and photoreceptor.

Belt background output V at the initial setting level. is taken into the CPU 71 via the analog input circuit 70, and internally A
/D conversion and stored in the RAM 73. Similarly, the belt background output V, detected during image recording. t*Vs*
g*Vs. 3 is also connected to the CPU via the analog input circuit 70.
The data is taken into the RAM 71, A/D converted, and taken into the RAM 73. And the belt skin output VSS at the initial setting level. and belt background output v3□ before pattern image recording in transfer ON state; V 1 (II / V ml!I
ll and ■! , , and belt background output v one week after pattern image recording with transfer ON. ! The ratio i V SO2/V
861, V, ..., and the ratio of the heald background output vses in the transfer OFF state: vsaz / vsos is determined, and each is compared with a preset reference value, and it is determined whether dirt has occurred based on the magnitude relationship with the reference value. Identify the location,
The load driver 74 lights up an LED indicating the abnormal location, or the abnormal location is displayed as a guidance on the display of the operating section of the recording device.

FIG. 18 shows a flowchart when making the determination. At the beginning, V. /Vs*. is compared with the reference value A, and if it is smaller than the initial setting level, it means that the belt surface output has decreased over time due to some kind of dirt or the like, and the process proceeds to the next flow.

When it is equal to or higher than the reference value A, it is assumed to be normal and jumps to READY. */When comparing Vsrt2 with the reference value 1, since we are comparing the belt background output with and without transfer, when it is 1, even with transfer, there is no dirt on the photoreceptor and the background-stain toner is transferred. Assuming that it has not been done, proceed to the next flow. If the value is other than 1, it is determined that there is an abnormality around the photoreceptor because the belt is stained due to transfer and the belt background output is reduced.

Next V. 2/v,. When comparing , with the standard value 1, since we are comparing the belt background output on the same belt before and after pattern image creation, if it is other than 1, one lap after pattern image creation, due to poor belt cleaning. Since a pattern image remains on the belt and the reflected output decreases accordingly, it is determined that the belt is abnormal. Standard value l
In this case, since there is still a decrease in the reflected output even before and after the pattern image is created, it is determined by the elimination method that the output decrease is due to deterioration or dirt in the sensor itself, and it is determined that the sensor is abnormal.

In this embodiment, a method of calculating the ratio and comparing it with a reference value has been described, but the same effect can be obtained by calculating the difference between each reflected output.

Furthermore, although this embodiment has described digital color image recording using a transfer belt and multiple photoreceptors, it is also possible to use an analog recording method, and it is not limited to color recording. The same effect can be obtained with a drum-shaped one.

I would like to add that, in this embodiment, as a control method after determination, the abnormal location is displayed. good.

(Effects) The present invention is as described above, and is not affected by dirt on the conveyor belt, dirt on the sensor, variation in sensitivity, etc., and can compensate for this by accurately measuring color shift.

Furthermore, in order to prevent false detection due to aging, it is possible to quickly determine the abnormal location where dirt is occurring.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a digital color image forming apparatus to which the present invention is applied, FIG. 2 is a front view of a transfer belt section, FIG. 3 is a system block diagram according to an embodiment of the present invention, and FIG. 4 is a schematic diagram of a digital color image forming apparatus to which the present invention is applied. Figure 5 is a block diagram of the image data transmission control, Figure 6 is a timing chart of each part of the same, Figure 7 is an explanation for setting the delay time of image data. 8 shows an embodiment of the pattern detection circuit according to the present invention, FIG. 9 shows an embodiment of the pattern interval measuring circuit, and FIGS. 10(a) and 10(b)
. (C), +d) are waveform diagrams of each part in Figure 8, Figure 11 is a timing chart in Figure 9, Figure 12 (a),
(b) is a flowchart of i, 1111a according to the present invention, FIG. 13 is a pattern detection circuit diagram according to a conventional example, FIG. 14 is a waveform diagram thereof, and FIG. 15 is for explaining the input of the background reflection output of the transfer belt. FIG. 16 is a timing chart at the time of image recording, FIG. 17 is a block diagram for determining the location where dirt occurs, and FIG. 18 is a flowchart. 27...Detection means, 41.47...Pattern image signal generation means, CNTl, 2.3.4...Detection timing counting means, 60...Comparison calculation means, 71...
・CPU. (a no BK CM Y to figure BK CM Y 1 translation to standing H to bl figure 12 (a)
(b) Figure 13's14 Figure jlI116 Garden

Claims (1)

[Claims] a photoreceptor; a charger that uniformly charges the surface of the photoreceptor;
A recording device includes an exposure means for projecting image light on a photoreceptor according to recording information, a developing means for developing an electrostatic latent image on the photoreceptor, and a transfer means for transferring the developed image on the photoreceptor onto a transfer paper. In an image recording device in which a plurality of images are arranged and images are transferred one over the other by sequentially conveying transfer paper to each recording device using a transfer belt,
A pattern image signal generation means for forming a measurement pattern image for each color on a transfer belt, a single detection means for detecting passage of each color pattern image, a detection timing counting means by the detection means, and the detection means. It has a comparison calculation means that compares the count value by the timing counting means with a set value and calculates the deviation amount as necessary, and a writing timing signal generation means for each color whose setting can be changed according to the output value from the calculation means. , the transfer belt background reflection output V_S_G_0 at the time of initial setting of the detection means is stored in advance in the storage means, and at the time of image recording, the belt background reflection output V_S_G_1 before recording of the pattern image recording portion of the belt in the transfer ON state, Similarly, the belt background reflection output V_S_G_2 of the same part after one rotation of the belt after pattern image recording, and the belt background reflection output V_S of the same part in the transfer OFF state.
_G_3 is detected, V_S_G_0 and V_S_G_1,
V_S_G_1 and V_S_G_2, V_S_G_2 and V
An image forming apparatus characterized in that the deterioration of the detection means, the deterioration of the transfer belt, and the background stain on the photoreceptor are determined based on the results of the ratios or differences of _S_G_3.