JP2761287B2 - Image forming device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus that forms images of different colors on a recording medium.

[Conventional technology]

2. Description of the Related Art In recent years, there has been remarkable spread and development of color copying apparatuses, and there are many types of printer engines that realize an ink jet system, a thermal transfer system, a silver halide photographic system, and an electrophotographic system. Among them, the electrophotographic method has been remarkably popularized due to its advantages of high speed and high image quality.

FIG. 9 is a cross-sectional view showing an example of this type of image forming apparatus. In particular, a color original is color-separated for each pixel, digitally read as an electric signal, and a color laser beam printer unit uses an electrophotographic method. For obtaining a full-color print image, A indicates an image reading unit, and B indicates an image printing unit.

 Hereinafter, the configuration and operation will be described.

In the image reading section A, a document exposure lamp (certification lamp)
2, the color original 1 is irradiated, and the color reflected light image reflected from the color original 1 is formed on the color image sensor 3. The color image signal, which is color-separated for each pixel by the color image sensor 3 (CCD color line sensor), is subjected to signal processing by a color signal processing circuit 4 and is connected to a cable.
It is input to the image processing circuit 5 through 25.

The image processing circuit 5 sends the digital image signal to the image printing unit B after color correction by digitizing the input signal and digital image processing of the color signal. The semiconductor laser 8 is modulated by the semiconductor laser drive unit 7 in accordance with the image data sent to the image printing unit B via the cable 6, and is modulated by the polygon mirror 9 onto the photosensitive drum via the mirror 10. To form a single-color latent image which has been color-separated. The formed latent image is visualized (developed) in developing devices 21 to 24, and the color-separated toner image is formed on a photosensitive drum.
11 are formed sequentially. 14 is a conveyor belt, 20 is an exposure lamp, and 19 is a charger.

On the other hand, the copy paper is fed from the cassette 17 or the cassette 18, wound around the transfer drum 12, and the toner is transferred to the copy paper in synchronization with the color separation toner image described above. As shown in this figure, since only one color image is formed in one image forming process, the color separation process of the original is performed for the number of toner colors, that is, yellow (Y), magenta (M), The processes of cyan (C) and black (K) are repeated four times, and the steps of latent image formation, development, and transfer corresponding to each color component are also repeated in synchronization with each color separation.

In this manner, the copy paper is peeled off by the separation claw 13 after four rotations to complete the transfer of the four colors while being wound around the transfer drum 12, and guided to the heat and pressure fixing rollers 15 and 16, and the toner image on the copy paper is removed. Is fixed and discharged out of the apparatus, and one full-color copy is completed. That is, in the case of this type of color copying apparatus, each color separation image, Y, M, C,
A four-drum type color image forming apparatus as shown in FIG. 10 has been proposed in order to further increase the speed by performing the respective steps of K so as to overlap each other.

FIG. 10 is a sectional view showing an example of a four-drum type color image forming apparatus, and the configuration and operation will be described below.

A color original 1 placed on a platen is illuminated by an illumination lamp 2, a color separation image is read by a CCD color line sensor 3, and a color signal processing circuit 4 and a cable 25 are provided.
9 until the digital image processing is performed by the image processing circuit 5 through the process shown in FIG. 9, but one page of the full-color image signal is temporarily stored in the memory device 26 thereafter.

That is, as will be described later, in this type of apparatus, a plurality of photosensitive drums (image forming units) are juxtaposed, and images of a plurality of colors are formed at the same time. This is because images need to be stored.

On the other hand, the image forming section independently operates the photosensitive drums 29 to 32, the primary chargers 41 to 44, and the developing devices for the respective components, magenta (M), cyan (C), yellow (Y), and black (K). Devices 33 to 36, transfer chargers 37 to 40, and cleaner devices 62 to 65, and as the paper fed from the cassette advances,
When the paper signal is detected by the paper leading edge detector (ITOP sensor) 67, the timing control circuit (not shown) synchronizes the image signal for each color component already stored in the memory device 26 with the proper timing in synchronization with the paper leading edge signal. After the signal is read out by the second digital image processing section 27 and the signal is processed by the second digital image processing section 27, the light beam modulated by the semiconductor lasers 50, 57 to 59, etc. 49,51〜53,54〜5
After being reflected by 6 and irradiating the photosensitive drum 29 to form a latent image, magenta toner is developed by a developing unit 33 and a first magenta image is formed on copy paper by a transfer charger 37. Is formed. Subsequently, in the second, third, and fourth stations, cyan (C), yellow (Y), and black (K) are similarly developed and transferred with high precision, and then fixed by fixing rollers 15 and 16. One copy is completed. 16 is a cassette, 66 is an interface circuit.

In such an apparatus, as described above, there are four drum stations for forming each color component image, four laser beam generators for forming a latent image, and the precision of applying each laser beam to each photosensitive drum. Also, four optical system devices for good irradiation are required.

On the other hand, in a high-accuracy full-color copying machine, the position accuracy for superimposing each color component image needs to be 100 to 150 μm or less, and it is difficult to adjust each component for image formation with such accuracy. Very difficult. Further, even if the adjustment is possible, for example, misalignment due to thermal expansion of each component due to temperature fluctuation, misalignment due to reproducibility of machine positional accuracy after jam processing, drum scratches, malfunction of the developing device, etc. The position adjusted by component replacement or the like immediately shifts, and once shifted, it is practically possible for the user to adjust it.

In order to make such adjustments automatically, for example,
As shown in FIG. 11, a mark for registering each color component yellow, magenta, cyan, and black is printed on the transfer belt at a fixed interval time, and the mark is formed at two places on the back and front sides, for example, by a CCD. The sensors 80 and 81 detect the amount of deviation in the main scanning and sub-scanning directions, the inclination, and the like at each printing station, and correct the deviations in the sub-scanning direction and the main scanning direction by the following correction means. A device for automatic correction has been proposed.

(Automatic correction in the sub-scanning direction)

FIG. 12A is a timing chart showing the timing of forming marks for registration in this type of image forming apparatus.

As shown in this figure, in the sub-scanning direction, the number of lines is counted by a counter circuit (not shown) from the rising edge of the output signal ITOP from the ITOP sensor 67 for detecting the leading edge of the copy sheet. After counting tc time for cyan, ty for yellow
After counting the time, in black, after counting tk time, the output signals MTOP, CTOP, YTOP, and KTOP signals are generated, and the image signal is sent from the rising edge of each signal. For example, the count values tm to tk may be determined based on the timing at which the mark #) is detected by the sensors 80 and 81.

(Automatic correction in main scanning direction)

FIG. 12 (b) is a timing chart showing the timing of forming marks for registration in this type of image forming apparatus.

Each signal MBD, CBD, YBD, KBD is a detection signal of a laser beam for forming a latent image of yellow, magenta, cyan, and black. Each signal determines the main scanning position of the image at each position. Is a reference signal. Each color image has an enable signal M generated after a pixel count xm, xc, xy, xk from the detection signal MBD, CBD, YBD, KBD of the laser beam.
Since the values are determined by EN, CEM, YEN, and KEN, the respective values may be appropriately determined based on the positions where the above-described marks are detected by the sensors 80 and 81.

The automatic correction of the inclination is realized, for example, for magenta by tilting the reflection mirrors 45, 46, 47 by an actuator (not shown).

[Problems to be solved by the invention]

When the sensors 80 and 81 read the pattern transferred to the transfer belt in this manner, registration deviation can be detected. However, as shown in FIGS. 13 (a) and 13 (b), the transfer belt and the black Since the toner does not have a reflection region in any wavelength region, a pattern formed by black toner on the transfer belt cannot be identified.

In other words, the yellow, magenta, and cyan toners absorb light having wavelengths of 400 to 500 nm, 500 to 600 nm, and 600 to 700 nm, respectively. Has no reflective area at any wavelength.

On the other hand, the transfer belt reflects only in the infrared region,
By disposing an infrared cut filter in front of the sensors 80 and 81, the above-described magenta, cyan, and yellow marks can be read. However, since the black mark has no reflective area in any area, There is a problem that both can be distinguished, and as a result, registration deviation of the black station cannot be detected.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to provide a device capable of accurately detecting a registration mark image formed on a recording medium and accurately correcting the position of the image.

[Means for solving the problem]

An image forming apparatus according to the present invention detects a plurality of image forming units for forming images of different colors on a recording medium, and detects a plurality of registration mark images formed on the recording medium by the plurality of image forming units. Detecting means for correcting the position of an image formed by the plurality of image forming means using the output of the detecting means, and a predetermined registration mark image among a plurality of registration mark images formed on the recording medium. Forming a base image of a color having a reflection characteristic different from that of the registration mark image on the recording medium, and controlling the plurality of image forming means so as to multiplex the predetermined registration mark image on the base image; Control means.

[Action]

According to the present invention, the registration mark image on the recording medium can be accurately detected, and the position of the image can be accurately corrected.

〔Example〕

FIG. 1 is a cross-sectional view for explaining a main configuration of an image forming apparatus according to an embodiment of the present invention, and the same components as those in FIG. 10 are denoted by the same reference numerals.

In this figure, reference numeral 27a denotes a registration correction pattern generation control unit, which outputs a video signal output from the registration correction pattern generation control unit 27a to a laser driver 27b, and controls each photosensitive drum via each laser scanning optical system. An electrostatic latent image corresponding to the registration correction pattern is formed at desired positions 29 to 32.

In the image forming apparatus configured as described above, when a predetermined resist alignment pattern forming process on the photoreceptor is started by the pattern forming means (each of the first to fourth stations), the transfer control means (the resist in this embodiment). Prior to the pattern transfer of the color developer (black in this embodiment) that matches the spectral reflection characteristics of the transport member (transfer belt in this embodiment) in which the translation correction pattern generation control unit 27a) forms the registration pattern, Controls the multiple transfer of color transfer with a color developer having a spectral reflection characteristic different from the spectral reflection characteristic and pattern transfer of a color developer that matches the spectral reflection characteristic of the conveying member, and matches the spectral reflection characteristic of the conveying member. The pattern of the color developer is multiplex-transferred onto a color-transferred transfer area using a color developer having different spectral reflection characteristics (yellow in this embodiment). When the registration pattern of each color transferred to the conveying member in this way is detected by the detection means (sensors 80 and 81), the timing control means (also used by the digital image processing unit 17) is used by the detection means. The image forming timing is individually controlled on the basis of the output of (1), and registration of each color is performed.

Regarding the multiple transfer control, the registration correction pattern generation control unit 27a sets the enable signal YENB to “H level” twice for the laser driver 27b according to the timing chart shown in FIG. In the transfer area of the registration correction pattern for black formed on the photosensitive drum 32 and transferred to the transfer belt, the yellow toner is solidly transferred to the immediately preceding yellow station (third station).

Then, the registration correction pattern developed by the developed black toner is superimposed and transferred to the yellow solid area underlaid and transferred by the yellow toner. Can be detected with good discrimination.

FIG. 2 is a circuit block diagram for explaining a main configuration of the registration correction pattern generation control unit 27a shown in FIG. 1. The configuration and operation will be described below.

In the figure, reference numeral 85 denotes a bit counter, which is a horizontal synchronization signal HS.
Count the number of images since YNC occurred. 90 to 93 are comparators which are registered by a CPU (not shown) or the like.
At the timing when the count value set to ~ 89 and the value of the bit counter 85 match, each output becomes "H level".
Are configured to be, for example, registers 86 to 89
When the values X1, Y1, X2, and Y2 are set respectively, the output of the J / K flip-flop 94 becomes “H level” at the value X1 pixel, becomes “L level” at the value Y1 pixel, and J / K The output of the flip-flop 95 becomes “H level” at the value X2 pixel,
It becomes “L level” at the Y2 pixel. Therefore, enable signals ENB (1 to N) as shown in the timing chart of FIG. 3A are obtained at the output of the OR gate 96.

1 to N indicate the number of lines, 1 is the first line, 2
Corresponds to the signal generated at the line N, and N corresponds to the signal generated at the line N. Reference numeral 200 denotes a color spreading control signal, which is generated and output from the registration correction pattern generation control unit 27a shown in FIG. 201 is an enable signal input and enable signal NEN
B (also the enable signals CENB, YENB, and BKENB) are input from the registration correction pattern generation control unit 27a.

Reference numeral 90 denotes a pattern ROM which stores pattern data corresponding to the pattern shown in FIG. 3B (for example, pattern "#" in this embodiment).
The pattern “#” is read according to the address generated by the dress counter 98. VD1,2, VDK, K + 1, VDL, L
+1, VDM, M + 1, VDN, N + 1 are line numbers 1, 2, K, K + 1, L, L
This is a video signal for forming a pattern corresponding to +1, M, M + 1, N, N + 1.

These video signals VD1,2, VDK, K + 1, VDL, L + 1, VDM, M
By outputting +1, VDN, N + 1 to the OR gate 100 at a predetermined timing, electrostatic latent images corresponding to the pattern shown in FIG. 3B are formed on the photosensitive drums 29 to 32 and stored in a developing unit (not shown) The image is visualized by each of the toners transferred and is transferred onto a transfer belt to be transported.

Hereinafter, the pattern transfer process will be described with reference to the timing chart shown in FIG.

FIG. 4 is a timing chart for explaining the pattern formation timing shown in FIG. 3 (b).

As shown in this figure, the reference shown in FIG.
Because rising of the output signal ITOP from the ITOP sensor 67, the predetermined time _{t m, t c, t y} , t k ( where the transport speed of the transfer belt is constant) for each of the drum at the timing of the image forming When the laser exposure is started, the four colors just overlap on the transfer belt or the print paper. Therefore, in order to form the magenta, cyan, yellow, and black patterns on the transfer belt as shown in FIG.
t _m , predetermined time t _c − (3/2) Δ (where Δ indicates the time required for pattern printing) predetermined time t _y − (5/2) Δ, predetermined time t _k − (7/2) Δ It is sufficient to print at the timing of.

FIG. 5 is a schematic view showing a pattern transfer state in the image forming apparatus according to the present invention, in which pairs are transferred one by one so as to correspond to predetermined positions in the width direction orthogonal to the transport direction of the transfer belt VV. The shaded area in the figure is a color spread area where yellow transfer has been performed in the third station (for yellow), and corresponds to a state in which the pattern formed in the fourth station is superimposed and transferred on this color spread area.

As shown in FIG. 4, the output signal IT from the ITOP sensor 67
The predetermined time t _m and the predetermined time t _c − (3 /
2) Δ (however, Δ indicates the time required for pattern printing) is stored in the pattern ROM 99 at the timing when the predetermined time t _y − (5/2) Δ and the predetermined time t _k − (7/2) Δ have elapsed. The pattern data is read out and output to the laser driver 27b shown in FIG.
A pattern for registration correction of each of the magenta, cyan, and yellow stations is transferred to the transfer belt VV.

In addition, the registration correction pattern generation control unit 27a outputs the color spread control signal 200 at a predetermined time t _y − (7/2) Δ from the rise of the output signal ITOP from the ITOP sensor 67, so that the fourth station The yellow toner is transferred (as a lower color) onto the pattern transfer area (the transfer belt VV (the hatched area shown in FIG. 5)) by the black toner for registration correction.
Predetermined time from rising of output signal ITOP from sensor 67
t _k - (7/2) at the timing of Δ course, black pattern for registration correction is transferred to the color spread area.

In this way, the transferred pattern for registration correction of each station is identified and detected by the sensors 80 and 81 provided downstream of the transfer belt VV in the transport direction.

FIG. 6 is a flowchart showing an example of a registration correction pattern forming operation in the image forming apparatus according to the present invention. Note that (1) to (13) indicate each step.

First, when the output signal ITOP from the ITOP sensor 67 is detected (1), a timer (not shown) is started (2), and when the timer value matches the predetermined time t _m (3), the pattern ROM 9
From 9, a pattern forming exposure is performed in a magenta station based on the output pattern (4), developed with magenta toner, and the pattern is transferred to the transfer belt VV.

Next, when the time value matches the predetermined time t _y- (5/2) Δ (7), pattern formation exposure is performed at the yellow station based on the output pattern from the pattern ROM 99 (8), and the pattern is developed and transferred. When the transfer to the belt VV is performed, and the Tama value matches the predetermined time t _y − (7/2) Δ (9), the registration correction pattern generation control unit 27
a outputs the color spread control signal 200 to the AND gate 101, performs pattern formation exposure at the yellow station based on the color spread pattern (10), develops the color spread pattern, and transfers the color spread pattern to the black pattern transfer area of the transfer belt VV. (11).

Next, when the timer value matches the predetermined time t _k − (7/2) Δ (12), pattern formation exposure is performed in the black station based on the output pattern from the pattern ROM 99 (13), and the black pattern is developed by development. The image is transferred to the yellow spread area of the transfer belt VV, and the process ends.

In the above embodiment, a four-drum type full-color image forming apparatus has been described as an example. However, the image forming apparatus in which developing units 112, 114, 116, and 118 are arranged around the photosensitive drum 110 as shown in FIG. The invention can be applied.

FIG. 7 is a cross-sectional view of a principal part for explaining a configuration of an image forming apparatus according to another embodiment of the present invention.
The developing devices 112, 114, 116, and 118 are arranged in this order in the direction of the arrow. 111, 113, 115 and 117 are chargers for uniformly charging the photosensitive drum 110. P is a recording medium.

 LM, LC, LY, and LK indicate exposure beams.

Hereinafter, the operation of FIG. 7 will be described with reference to FIGS. 8 (a) and (b).

FIG. 8A is a characteristic diagram showing the spectral reflectance of the photosensitive drum 110 shown in FIG. 7, in which the horizontal axis represents the wavelength and the vertical axis represents the reflectance.

FIG. 8 (b) is a schematic diagram showing a state in which a yellow registration pattern is formed on the photosensitive drum 110 shown in FIG.

The photosensitive drum 110 having the spectral reflection characteristic as shown in FIG. 8A substantially matches the spectral reflection characteristic of the yellow toner shown in FIG.
The upper yellow mark cannot be detected.

Therefore, the pattern of the yellow color can be reliably identified and detected in the same manner as described above by transferring the black toner in color at a predetermined timing prior to the yellow mark transfer area on the photosensitive drum 110.

〔The invention's effect〕

As described above, according to the present invention, a registration mark image is formed on a base image having a reflection characteristic different from that of a predetermined registration mark image. Even in the same case, the registration mark image can be accurately detected.

Therefore, the position of the image can be accurately corrected.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a main part configuration of an image forming apparatus according to an embodiment of the present invention, and FIG. 2 is a circuit block diagram illustrating a main part configuration of a correction pattern generation control unit illustrated in FIG. FIG. 3 (a) is a timing chart showing the timing of forming the correction pattern data by the correction pattern generation control unit shown in FIG. 1, and FIG. 3 (b) is the correction pattern generation control unit shown in FIG. FIG. 4 is a plan view showing an example of a pattern formed by the method shown in FIG. 4, FIG. 4 is a timing chart for explaining the pattern formation timing shown in FIG.
FIG. 6 is a schematic diagram showing a pattern transfer state in the image forming apparatus according to the present invention, FIG. 6 is a flowchart showing an example of a registration correction pattern forming operation in the image forming apparatus according to the present invention, and FIG. FIG. 8 (a) is a characteristic diagram showing the spectral reflectance of the photosensitive drum shown in FIG. 7, and FIG. 8 (b) is a characteristic diagram showing the configuration of an image forming apparatus showing another embodiment. FIG. 9 is a schematic view showing a state of forming a registration pattern for yellow with a color spread formed on the photosensitive drum shown in FIG. 7, FIG. 9 is a sectional view showing an example of this type of image forming apparatus, and FIG. Sectional view showing an example of a four-drum type color image forming apparatus.
FIG. 11 is a perspective view showing a registration mark detection mechanism in this type of apparatus, FIG. 12A is a timing chart showing registration mark formation timing in this type of image forming apparatus, and FIG. FIG. 13B is a timing chart showing the timing of forming marks for registration in this type of image forming apparatus, and FIG. 13 is a diagram showing the spectral reflection characteristics of each color toner. In the figure, 27 is a digital image processing unit, 27a is a registration correction pattern generation control unit, 27b is a laser driver, and 80 and 81 are sensors.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI G03G 15/16 B41J 3/00 M (72) Inventor Jun Koide 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Yoshiaki Tahara 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-4-149472 (JP, A) JP-A-4-147280 (JP, A) JP-A-62-239180 (JP, A) JP-A-1-3852 (JP, U)

Claims (1)

(57) [Claims] A plurality of image forming means for forming images of different colors on a recording medium; and a detecting means for detecting a plurality of registration mark images formed on the recording medium by the plurality of image forming means. Correcting means for correcting the position of an image formed by the plurality of image forming means using the output of the detecting means; and a predetermined registration mark image among the plurality of registration mark images formed on the recording medium. Forming a base image of a color having different reflection characteristics on the recording medium, and controlling the plurality of image forming units to form the predetermined registration mark image in a multiplexed manner on the base image; An image forming apparatus comprising: