JPH04218075A - Image forming device - Google Patents

Abstract

PURPOSE:To surely read the registration correction pattern of color developer which cannot be detected because of a spectroscopic characteristic by executing the color spreading transfer of a registration correction pattern area by the other color developer in advance. CONSTITUTION:Before the pattern transfer of the color developer which coincides with the spectroscopic reflecting characteristic of a carrying member which forms a resistration pattern, the multiple transfer of the color spreading transfer by the color developer having the different characteristic from the spectroscopic reflecting characteristic and the pattern transfer of the color developer which coincides with the spectroscopic reflecting characteristic of the carrying member is controlled by a transfer control means 27a. Then, the pattern of the color developer which coincides with the spectroscopic reflecting characteristic of the carrying member is multiply transferred on the color spreading transfer area by the color developer having the different characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image forming apparatus capable of forming a color image by transferring an image developed with each color developing material onto a recording medium.

[Conventional technology]

The spread and development of color copying devices in recent years has been remarkable, and there are many types of printer engines that implement inkjet methods, thermal transfer methods, silver halide photography methods, and electrophotography methods. Among these, electrophotography has become rapidly popular 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 document is color-separated pixel by pixel, digitally read as an electric signal, and a color laser beam printer is used to print an image using an electrophotographic method. A full-color print image is obtained by this method, where A indicates an image reading section and B indicates an image printing section.

The configuration and operation will be explained below.

In the image reading section A, a document exposure lamp (illumination lamp) 2
As a result, the color original 1 is illuminated, and a color reflected light image reflected from the color original 1 forms an image on the color image sensor 3. A color image signal separated into colors for each pixel by a color image sensor 3 (CCD color line sensor) is processed by a color signal processing circuit 4, and then sent to a cable 2.
5 to the image processing circuit 5.

The image processing circuit 5 performs color correction by digitizing the input signal and digital image processing of the color signal, and then sends the digital image signal to the image printing section B. According to the image data sent to the image printing section B via the cable 6, the semiconductor laser drive section 7 modulates the semiconductor laser 8, and the polygon mirror 9 prints the image onto the photosensitive drum.
A monochromatic latent image color-separated in a raster pattern is formed via a mirror 10. The formed latent images are visualized (developed) in the developing devices 21 to 24, and color separated toner images are sequentially formed on the photosensitive drum 11. 14 is a conveyor belt, 20 is an exposure lamp, and 19 is a charger.

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

In this way, the copy paper remains wrapped around the transfer drum 12 and rotates four times in order to complete the transfer of four colors, and then is separated by the separating claw 13 and guided to the heat pressure fixing rollers 15 and 16.
The toner image on the copy paper is fixed and discharged outside the machine, completing one sheet of full-color copying. In other words, in the case of this type of color copying apparatus, each color separated image,
By overlapping each process of Y, M, C, and K, the first
A four-drum color image forming apparatus as shown in FIG. 0 has also been proposed.

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

A color document 1 placed on a document table is illuminated by an illumination lamp 2, a color separated image is read by a CCD color line sensor 3, and is sent to an image processing circuit 5 via a color signal processing circuit 4 and a cable 25. The process is the same as that shown in FIG. 9 until digital image processing is performed, but after that, one page of full-color image signals is temporarily stored in the memory device 26.

That is, as will be described later, in this type of device, a plurality of photosensitive drums (image forming sections) are arranged side by side, and images of multiple colors are formed at the same time. This is because images need to be stored.

On the other hand, the image forming section is configured for each component, magenta (M), cyan (
C), yellow (Y), and black (K) independently.
Photosensitive drums 29 to 32 and primary chargers 41 to 44, respectively.
, developing devices 33 to 36, transfer chargers 37 to 40, and cleaner devices 62 to 65.As the paper fed from the cassette advances, a paper leading edge detector (ITOP sensor) 6 is provided.
7, the image signal for each color component already stored in the memory device 26 is read out at an appropriate timing by a timing control circuit (not shown) in synchronization with the paper leading edge signal, and the second digital signal is read out at an appropriate timing. After being subjected to signal processing by the image processing unit 27, the magenta (M) image is processed by the semiconductor laser 50,
The light beams modulated from 57 to 59 etc. are transmitted to the polygon mirror 28, reflecting mirrors 45 to 49, 51 to 53, 54 to 56.
After being reflected and irradiated onto the photosensitive drum 29 to form a latent image, the magenta toner is developed in the developing device 33, and the first color magenta image is formed on the copy paper by the transfer charger 37. It is formed. Continuing, the second, third,
Similarly, at the fourth station, cyan (C), yellow (
After the colors Y) and black (K) are developed and transferred with high accuracy, they are fixed by fixing rollers 15 and 16 to complete one copy. 16 is a cassette, and 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 each laser beam is applied to each photosensitive drum with precision. Four optical systems are still required for good irradiation.

On the other hand, in a high-precision full-color copying device, the positional accuracy for overlapping each color component image must be 100 to 150 μm or less, and each component for image formation must be
Adjustment with such precision is extremely difficult. Also,
Even if adjustments can be made, for example, positional deviations may occur due to thermal expansion of each component due to temperature fluctuations, positional deviations due to reproducibility of machine position accuracy after jam removal, or parts due to drum scratches or defects in the developing device. The position adjusted by replacement or the like will shift immediately, and once shifted, it is virtually impossible for the user to adjust the position.

Therefore, for example, the first
As shown in Figure 1, marks for registration of each color component yellow, magenta, cyan, and black are printed on the transfer belt at a certain interval time, and these are printed at two locations, one in the back and one in the front, using a CCD, for example. sensor 80,
81 to detect the amount of deviation, inclination, etc. in the main scanning and sub-scanning directions at each print station,
An apparatus has been proposed that automatically corrects deviations in the sub-scanning direction and the main scanning direction using the following correction means.

[Automatic correction in sub-scanning direction]

FIG. 12(a) 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 output signal ITOP from the ITOP sensor 67 that detects the leading edge of the copy paper
From the rising edge of , a counter circuit (not shown) counts the number of lines, and for example, after counting tm time for magenta, counting tc time for cyan, counting ty time for yellow, and counting tk time for black, the lines are output. Signal MTOP, CT
By generating OP, YTOP, and KTOP signals and transmitting an image signal from the rising edge of each signal, the above-mentioned registration alignment mark (for example, mark #) is detected by the sensor 80.
, 81, the count value t
It is sufficient to determine m to tk.

[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.

The signals MBD, CBD, YBD, and KBD are laser beam detection signals for forming yellow, magenta, cyan, and black latent images, and each signal determines the main scanning position of the image at each position. This is the reference signal for Each color image is a laser beam detection signal MBD, CBD, YB
Pixel counts xm, xc, xy from D and KBD respectively
, xk are generated after enable signals MEN, CEN
, YEN, and KEN, each value may be appropriately determined based on the position where the above-mentioned mark is detected by the sensors 80 and 81.

Note that the automatic tilt correction, for example for magenta,
Automatic correction is realized by tilting the reflecting mirrors 45, 46, and 47 by actuators (not shown).

[Problem to be solved by the invention]

When the sensors 80 and 81 read the patterns transferred to the transfer belt in this way, it becomes possible to detect registration deviations, but as shown in FIGS. 13(a) and 13(b), Since the toner does not have a reflective region in any wavelength range, it becomes impossible to identify the pattern formed by the black toner on the transfer belt.

That is, yellow, magenta, and cyan toners have a wavelength of 400 to 500 nm, 500 to 600 nm, and 60 nm, respectively.
Since it absorbs light with a wavelength of 0 to 700 nm, conversely, it has a reflective region at other wavelengths, but black toner does not have a reflective region at any wavelength.

On the other hand, since the transfer belt reflects only in the infrared region, by placing an infrared cut filter in front of the sensors 80 and 81, the magenta, cyan, and yellow marks mentioned above can be read. Since the mark does not have a reflective area in any area, it is not possible to distinguish between the two, and as a result, there is a problem in that the misregistration of the black station cannot be detected.

This invention was made in order to solve the above-mentioned problem, and when a registration correction pattern is transferred to a transfer belt using a developing material of a color that is undetectable due to spectral characteristics, it is necessary to By color-laying and transferring the registration correction pattern area using a developer of another color before transferring the pattern of a developer of a certain color, a registration correction pattern of a developer of a color that becomes undetectable due to spectral characteristics is created. An object of the present invention is to provide an image forming apparatus that can reliably read images.

[Means to solve the problem]

The image forming apparatus according to the present invention includes a pattern forming means for forming a predetermined resist alignment pattern on a conveyance member capable of carrying an image using a developer of each color, and a resist alignment pattern of each color transferred onto the conveyance member by the pattern forming means. A detection means for detecting, a timing control means for individually controlling the image forming timing based on the output of the detection means, and a pattern transfer of a color developer that matches the spectral reflection characteristics of a conveying member that forms a registration pattern. In advance,
A transfer control means is provided for controlling multiple transfer of color spread transfer using a color developer having spectral reflection characteristics different from the spectral reflection characteristics and pattern transfer using a color developer matching the spectral reflection characteristics of the conveyance member. .

[Operation] In the present invention, when the pattern forming means starts forming a predetermined resist alignment pattern on the photoconductor, the transfer control means selects a color that matches the spectral reflection characteristics of the conveying surface material on which the resist alignment pattern is to be formed. Prior to the pattern transfer of the developer, multiple transfer of color spread transfer using a color developer having spectral reflection characteristics different from the spectral reflection characteristics and pattern transfer of the color developer matching the spectral reflection characteristics of the conveyance member is controlled. , it is possible to multiple-transfer a pattern of color developer that matches the spectral reflection characteristics of the conveyance member onto a colored transfer area using color developers having different spectral reflection characteristics, and in this way, the pattern of the color developer that matches the spectral reflection characteristics of the conveyance member is transferred to the transfer member. When the registration pattern of each color is detected by the detection means, the timing control means individually controls the image forming timing based on the output of the detection means, thereby making it possible to perform the registration of each color.

[Embodiment] FIG. 1 is a cross-sectional view illustrating the main structure of an image forming apparatus showing an embodiment of the present invention, and the same parts as in FIG. 10 are given the same reference numerals.

In this figure, reference numeral 27a denotes a registration correction pattern generation control section, which outputs a video signal output from the registration correction pattern generation control section 27a to a laser driver 27b, and sends the video signal to each photosensitive drum via each laser scanning optical system. Electrostatic latent images corresponding to the registration correction pattern are formed at desired positions 29 to 32.

In the image forming apparatus configured as described above, when the pattern forming means (each of the first to fourth stations) starts forming a predetermined resist alignment pattern on the photoreceptor, the transfer control means (in this embodiment, the resist Prior to the pattern transfer of a color developer (black in this embodiment) that matches the spectral reflection characteristics of the conveyance member (transfer belt in this embodiment) where the ration correction pattern generation control unit 27a) forms the registration pattern, Controls multiple transfer of color spread transfer using a color developer with different spectral reflection characteristics and pattern transfer of the color developer that matches the spectral reflection characteristics of the conveyance member, and matches the spectral reflection characteristics of the conveyance member. This makes it possible to multiple-transfer patterns of color developers having different spectral reflection characteristics (yellow in this example) onto the color spread transfer area, and in this way, the patterns of each color transferred to the conveying member can be transferred multiple times. When the registration pattern is detected by the detection means (sensors 80, 81), the timing control means (also served by the digital image processing section 27) individually controls the image formation timing based on the output of the detection means, Perform registration alignment.

Regarding the multiple transfer control, the registration correction pattern generation control section 27a sets the enable signal YENB to "H level" twice for the laser driver 27b according to the timing chart shown in FIG. 4, which will be described later. On the transfer area of the black registration correction pattern formed on the photosensitive drum 32 and transferred to the transfer belt, yellow toner is solidly transferred to the immediately preceding yellow station (third station) underlay.

Then, the registration correction pattern developed with the developed black toner is weight-transferred onto the yellow solid area underlay-transferred with this yellow toner.
Further, the developed black registration correction pattern can be detected with good discrimination by the sensors 80 and 81 after being transported.

FIG. 2 is a circuit block diagram illustrating the main part configuration of the registration correction pattern generation control section 27a shown in FIG. 1, and the configuration and operation will be described below.

In the figure, 85 is a bit counter, and the horizontal synchronization signal H
Count the number of pixels after SYNC occurs. 90
-93 are comparators, which are configured so that their respective outputs become "H level" at the timing when the count value set in the registers 86-89 by a CPU (not shown) matches the value of the bit counter 85. For example, the values X1, Y1, X2, and
When Y2 is set, the output of the J/K flip-flop 94 becomes "H level" at the value X1 pixel, "L level" at the value Y1 pixel, and the output of the J/K flip-flop 95 becomes the value It becomes "H level" at the eye, and becomes "L level" at the Y2-th pixel. Therefore, the enable signal ENB (1 to N) as shown in the timing chart shown in FIG. 3a) is obtained at the output of the OR gate 96.

Note that 1 to N indicate the number of lines; 1 corresponds to the signal generated on the first line, 2 corresponds to the second line, and N corresponds to the signal generated on the Nth line. Reference numeral 200 denotes a color layout control signal, which is generated and output from the registration correction pattern generation control section 27a shown in FIG. 201 is an enable signal input; enable signal MENB (enable signals CENB, YENB, B
The same applies to KENB) is input from the registration correction pattern generation control section 27a.

Reference numeral 90 denotes a pattern ROM, which stores pattern data corresponding to the pattern shown in FIG.
, the pattern "#" is read out in accordance with the address generated by the address counter 98. VD1, 2, V
DK, K+1, VDL, L+1, VDM, M+1, VD
N, N+1 are line numbers 1, 2, K, K+1, L, L
This is a video signal for pattern formation corresponding to +1, M, M+1, N, and N+1.

These video signals VD1, 2, VDK, K+1, VD
By outputting L, L+1, VDM, M+1, VDN, and N+1 to the OR gate 100 at predetermined timing,
An electrostatic latent image corresponding to the pattern shown in FIG. 3(b) is formed on the photosensitive drums 29 to 32, visualized by each toner contained in a developing device (not shown), and transferred onto the conveying transfer belt. be done.

The pattern transfer process described above will be described below with reference to the timing chart shown in FIG.

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

As shown in this figure, I
The laser for image formation is applied to each drum at predetermined times tm, tc, ty, and tk (however, the transport speed of the transfer belt is constant) from the rise of the output signal ITOP from the TOP sensor 67. When exposure is started, the four colors are configured to exactly overlap on the transfer belt or print paper. Therefore, in order to form magenta, cyan, yellow, and black patterns on the transfer belt as shown in FIG. Δ indicates the time required for pattern printing) predetermined time ty
- (5/2) Δ, it is sufficient to print at the timing of the predetermined time tk - (7/2) Δ.

FIG. 5 is a schematic diagram showing a state of pattern transfer in the image forming apparatus according to the present invention, in which patterns are transferred pair by pair so as to face each other at predetermined positions in the width direction perpendicular to the conveying direction of the transfer belt VV. Note that the shaded area in the figure is a colored area transferred in yellow by the third station (for yellow), and corresponds to a state in which a pattern formed in the fourth station is superimposed and transferred onto this colored area.

As shown in FIG. 4, from the rise of the output signal ITOP from the ITOP sensor 67, a predetermined time tm, a predetermined time tc - (3/2) Δ (where Δ indicates the time required for pattern printing) a predetermined time ty -(5/2)Δ, at the timing when the predetermined time tk-(7/2)Δ has elapsed, the pattern RO
The pattern data stored in the M99 is read out and sent to the laser driver 2 shown in FIG. 1 via the OR gate 100.
7b, the registration correction patterns of each magenta, cyan, and yellow station are transferred onto the transfer belt VV.

In addition, at a predetermined time ty-(7/2△ from the rise of the output signal ITOP from the ITOP sensor 67, the registration correction pattern generation control section 27a outputs the color laying control signal 200, so that the registration of the fourth station is Yellow toner is transferred as a color spread (as an undercolor) onto the pattern transfer area (on the transfer belt VV (shaded area shown in FIG. 5)) using black toner for correction, and the output signal IT from the ITOP sensor 67 is similarly transferred.
A black pattern for registration correction is transferred to the colored area at a timing when a predetermined time tk-(7/2)Δ has elapsed from the rise of OP.

In this way, the transferred patterns for registration correction at each station are identified and detected by the sensors 80 and 81 provided downstream in the conveyance direction of the transfer belt VV.

FIG. 6 is a flowchart showing an example of the registration correction pattern forming processing 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).
, when the timer value matches the predetermined time tm (3), pattern forming exposure is performed at the magenta station based on the output pattern from the pattern ROM 99 (4), and the pattern is transferred to the transfer belt VV by development with magenta toner. .

Next, when the timer value matches the predetermined time tc-(3/2)Δ (5), pattern forming exposure is performed at the cyan station based on the output pattern from the pattern ROM 99 (6), and the pattern is developed with cyan toner. is transferred onto the transfer belt VV.

Next, when the timer value matches the predetermined time ty-(5/2)Δ (7), pattern forming 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 to the transfer belt. At the same time as transferring to VV, the timer value is set for a predetermined time ty-(7/2)
If it matches Δ (9), the registration correction pattern generation control unit 27a outputs the color laying control signal 200 to the AND gate 101, and performs pattern forming exposure at the yellow station based on the color laying pattern (10). The colored pattern is developed and transferred to the black pattern transfer area of the transfer belt VV (11).

Next, when the timer value matches the predetermined time tk-(7/2)Δ (12), pattern forming exposure is performed at the black station based on the output pattern from the pattern ROM 99 (13), and the black pattern is transferred by development. The image is transferred to the yellow colored area of the belt VV, and the process is completed.

In the above embodiment, a four-drum type full-color image forming apparatus was explained as an example, but as shown in FIG.
The present invention can also be applied to image forming apparatuses arranged around 0.

FIG. 7 is a cross-sectional view of a main part illustrating the configuration of an image forming apparatus showing another embodiment of the present invention, in which 110 is a photosensitive drum;
Developing devices 112, 114, 116, and 118 are arranged in this order in the direction of the arrow.

Chargers 111, 113, 115, and 117 charge the photosensitive drum 110 uniformly. Note that P is a recording medium.

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

The operation shown in FIG. 7 will be described below with reference to FIGS. 8(a) and 8(b).

FIG. 8(a) is a characteristic diagram showing the spectral reflectance of the photosensitive drum 110 shown in FIG. 7, where the horizontal axis shows the wavelength and the vertical axis shows the reflectance.

FIG. 8(b) is a schematic diagram showing a state in which a registration pattern for yellow with color coverage (using black toner) is formed on the photosensitive drum 110 shown in FIG. 7.

The photosensitive drum 110 having the spectral reflection characteristics as shown in FIG. 8(a) roughly matches the spectral reflection characteristics of the yellow toner shown in FIG. 13(a).
The yellow mark above 10 cannot be detected.

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

〔Effect of the invention〕

As explained above, the present invention includes a pattern forming means for forming a predetermined resist alignment pattern on a conveyance member capable of carrying an image using a developer of each color, and a resist alignment pattern of each color transferred onto the conveyance member by the pattern forming means. A detection means for detecting, a timing control means for individually controlling the image forming timing based on the output of the detection means, and a pattern transfer of a color developer that matches the spectral reflection characteristics of a conveying member that forms a registration pattern. A transfer control means for controlling multiple transfer of color spread transfer using a color developer having different spectral reflection characteristics and pattern transfer of the color developer matching the spectral reflection characteristics of the conveying member is provided in advance. Therefore, even if the spectral reflection characteristics of the conveyance member that forms the registration alignment pattern match the spectral reflection characteristics of the color developer, each registration correction pattern formed by the pattern forming means cannot be detected. Means can be easily identified and detected. Therefore,
The registration of each color developer can be corrected with high precision.
This provides effects such as being able to form clear color images without color shift.

[Brief explanation of the drawing]

FIG. 1 is a sectional view illustrating the configuration of the main parts of an image forming apparatus showing an embodiment of the present invention, and FIG. 2 is a circuit block diagram illustrating the configuration of the main parts of the correction pattern generation control section shown in FIG. 1. , FIG. 3(a) is a timing chart showing the correction pattern data formation timing by the correction pattern generation control section shown in FIG. 1, and FIG. 3(b) is a timing chart showing the correction pattern generation control section shown in FIG. FIG. 4 is a plan view showing an example of the pattern formed by the method, FIG. 4 is a timing chart explaining the pattern formation timing shown in FIG. 3(b), and FIG. FIG. 6 is a flowchart showing an example of the registration correction pattern forming processing operation in the image forming apparatus according to the present invention, and FIG. 7 explains the configuration of the image forming apparatus showing another embodiment of the present invention. Main part cross section,
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 yellow color pattern formed on the photosensitive drum shown in FIG. FIG. 9 is a cross-sectional view showing an example of this type of image forming apparatus; FIG. 10 is a cross-sectional view showing an example of a four-drum color image forming apparatus;
FIG. 1 is a perspective view showing a mark detection mechanism for registration alignment in this type of apparatus, FIG. 12(a) is a timing chart showing the timing of forming marks for registration alignment in this type of image forming apparatus, and FIG. b) is a timing chart showing the timing of forming marks for registration in this type of image forming apparatus. In the figure, 27 is a digital image processing section, 27a is a registration correction pattern generation control section, 27b is a laser driver, and 80 and 81 are sensors.

Claims (1)

[Claims] In an image forming apparatus capable of forming a color image by transferring a color image to a recording medium while developing a latent image formed by exposure on a photoreceptor with a developer of each color, a predetermined amount of a latent image is transferred to a conveying member capable of carrying an image using a developer of each color. A pattern forming means for forming a resist matching pattern, a detecting means for detecting the resist matching pattern of each color transferred to the conveying member by the pattern forming means, and image forming timing is individually determined based on the output of the detecting means. and timing control means for controlling, and prior to pattern transfer of a color developer that matches the spectral reflection characteristics of the conveying member forming the resist alignment pattern, using a color developer having spectral reflection characteristics different from the spectral reflection characteristics. An image forming apparatus comprising: a transfer control means for controlling multiple transfer of color spread transfer and pattern transfer using a color developer that matches the spectral reflection characteristics of the conveying member.