JP2891786B2 - Color printing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a plurality of image forming media which are formed of a rotating body which rotates at a predetermined cycle and form an image by scanning at predetermined intervals. The present invention also relates to a color printing apparatus including a transfer medium including a rotating body that forms one image by superimposing and transferring images formed on each image forming medium.

[0002]

2. Description of the Related Art As a color printing apparatus using electrophotography, as shown in FIG. 2, photosensitive drums 11y, 11m, 11c, 1 of yellow, magenta, cyan, and black are used.
1k is disposed around the transfer drum 12, and the toner images formed on the photosensitive drums 11y, 11m, 11c, 11k of the respective colors are sequentially superimposed on the transfer drum 12 and transferred, and then printed on the printing paper 6 to form a color image. A device for obtaining is proposed.
Such a multi-drum type color printing apparatus is suitable for high-speed printing because it is easy to increase the printing speed.

[0003]

By the way, in the above-mentioned color printing apparatus, as shown in FIG. 6B, for example, the peripheral speed (the outer peripheral speed of the photosensitive drum) is changed by the eccentricity of each photosensitive drum 11 or the like. 11 during one rotation period. This fluctuation in the peripheral speed of the photosensitive drum 11 causes a positional shift during image formation. Further, due to the fluctuation of the peripheral speed of the transfer drum 12, these fluctuations are synthesized in the transfer of the image from the photosensitive drum 11, and the transfer of the toner image is performed for one cycle (corresponding to four rotations of the transfer drum 12) as shown in FIG. There has been a problem that the positions fluctuate irregularly, and the registration of the image of each color is shifted, leading to a deterioration in image quality in color printing.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to improve image quality in color printing by correcting image displacement.

[0005]

As shown in FIG. 1, the present invention for solving the above technical problem comprises a rotating body which rotates at a predetermined period and forms an image by scanning at predetermined intervals. A plurality of image forming media 1i (i = 1, 2,..., M) are arranged around these image forming media 1i, and the images formed on the respective image forming media 1i are superimposed and transferred. In the color printing apparatus provided with the transfer medium 2 composed of a rotating body that forms the image of the transfer medium 2, the rotation cycle of the image forming medium 1i is set to be an integral fraction of the rotation cycle of the transfer medium 2, A rotation signal output means 3 for outputting a signal corresponding to the rotation angle of the image carrier, and a predetermined reference image carrier 1i selected from the image carriers 1i, and each of the other image carriers 1i with respect to the reference image carrier 1i. Position of The amount of displacement is stored as correction data based on the information of the signal output from the rotation signal output unit 3 in a position storage unit 4 for storing each image forming medium 1 i and a correction data stored in the position storage unit 4. And a correcting unit 5 for correcting the scanning interval when forming an image on the image forming medium 1i.

[0006]

[0007]

According to the present invention, the rotation period T ₁ of the image forming medium ₁ i is changed to the rotation period T
₂ , the cycle of the transfer position shift variation that is the least common multiple of T ₁ and T ₂ is the shortest, and the transfer medium 2
Becomes equal to the cycle of one rotation. Therefore, when correcting the transfer position deviation, the correction may be performed within the range of the cycle of one rotation of the transfer medium 2.

Therefore, in order to correct the positional deviation by setting the above-described period, first, the amount of positional deviation of the image transferred onto the transfer medium 2 over one rotation of the transfer medium 2 is measured. That is, a predetermined reference image carrier 1i is selected from among the image carriers 1i, the amount of displacement of each of the other image carriers 1i with respect to the reference image carrier 1i is measured, and this operation is performed for all image forming media. 1i, and stores the result in the position storage unit 4 for each image forming medium 1i.

Next, printing is performed by rotating both media at the same rotation cycle as in the above measurement. When the printing is started and the two media start rotating, a signal corresponding to the rotation angle of the transfer medium 2 is sequentially output from the rotation signal output means 3 and the data of the displacement amount stored in the position storage means 4 is read. put out.
Then, a signal whose scanning interval has been corrected based on the data in the correction means 5 is created, and this signal is
i to form a corrected image on the image forming medium 1i.

The images thus formed on the image forming media 1i are transferred to the transfer medium 2 and these images are superimposed. Since these images are corrected so as to overlap each other, there is no displacement of the images. Then, the image transferred to the transfer medium 2 is transferred to the printing paper 6.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows a color printing apparatus applied to the embodiment of the present invention. The diameter of each of the photosensitive drums 11y, 11m, 11c, and 11k as the image forming medium 1i in this printing apparatus is １ ／ of the diameter of the transfer drum 12 as the transfer medium 2. The two drums are transmitted by a gear and driven at a rotational speed ratio of 3 to 1 so that the peripheral speeds match. Therefore, the rotation cycle of the photosensitive drum 11 is 1 / (1/3) of the integral number of the transfer drum 12.

FIG. 3 is a block diagram of a color printing apparatus according to the present embodiment. This printing apparatus includes a rotary encoder 13, a frequency divider 14, and a rotary encoder 1.
And a pulse counter 15 for counting the increment output pulse output by the counter 3 for each color (yellow, magenta m, cyan c, black k). Are stored, and LED arrays 27, 28, 29, and 30 for exposing the photosensitive drums 11y, 11m, 11c, and 11k are provided. The data in the image memory is shifted and stored in anticipation of the exposure and transfer delay time due to the transfer position relationship of each color.

In this embodiment, since images of other colors are corrected based on the yellow image, a magenta correction ROM 16 storing exposure timing correction data for each of magenta, cyan, and black is provided. R for cyan correction
It has an OM 17 and a ROM 18 for black correction.

On the other hand, in this embodiment, the resolution of the printing dots is 400 dpi, and the diameter of the transfer drum 12 is 410 m.
At m, the rotary encoder 13 is directly connected to the axis of the transfer drum 12 and outputs a pulse signal of 81,000 pulses per rotation. The frequency divider 14 divides the signal of 81,000 pulses per rotation, that is, a pulse signal obtained by equally dividing one rotation by 81,000 into 20250 pulses of ４, and outputs a pulse serving as a light emission timing of the LED array. The pulse counter 15 outputs 1 from the rotary encoder 13.
It counts 81,000 pulse signals per rotation, and is reset by a zero signal generated when the rotary encoder 13 makes one rotation.

By the way, the above ROMs 16, 17, 18
Is generated as follows.

First, as shown in the block diagram of FIG. 4, all four LED arrays 27, 28, 29 and 30 emit light using the same emission timing clock. And
With respect to the drum rotation direction, the dots where the positions of the dots of other colors, magenta MT, cyan CT, and black KT should be matched are printed side by side with reference to the yellow dot YT, and the printing state of the dots of these colors is enlarged. To check. As a result, the printing state of the dots of each color is shown in FIG.
As shown in (a), the dots of each color that should be arranged in a line are shifted in the drum rotation direction due to the eccentricity of each photosensitive drum 11 and the like. Therefore, the amount of deviation of dots of other colors based on the yellow dot YT is determined by the rotary encoder 13.
It is determined how many pulses correspond to the output pulse interval.

In FIG. 5A, the dot MT of the magenta toner lags behind the reference dot YT of the yellow toner by three pulses in the output pulse of the rotary encoder 13. Therefore, it is necessary to advance the light emission timing of the LED by three pulses in order to correct the position to be originally printed. First, data “0” is written to all addresses of the correction ROM 16. Assuming that the absolute rotation position of the transfer drum when the magenta toner dots are exposed, that is, the output of the counter 12 is m, FIG.
As shown in (1), data "1" is written to the address (m-3) of the ROM 16. Such an operation is performed on the transfer drum 12.
Is performed at several tens of points that are averagely distributed over one round of data.
Write 1 '.

Other cyan and black ROMs 17 and 18
The correction information of the exposure position for one round of the transfer drum 12 is written by the same operation.

When the writing of the correction information to each ROM is completed by the above operation, printing is performed next. First, an output pulse of the rotary encoder 13 output in synchronization with the rotation of the transfer drum 12 is counted by the pulse counter 15. this,
The output of the pulse counter 15 is used as an address for each ROM 1
3, 14, and 15 data are accessed. Thus, the exposure timing clock corresponding to the rotation angle of the transfer drum 12 is output from each of the ROMs 13, 14, 15 as data "1".

Each of the LED arrays 28, 29, 30 is RO
The corrected clock signals from M16, M17, M18, M18 are used as timing clocks,
The photosensitive drums 11m and 11m emit light based on
Expose c and 11k. The output pulses of each ROM are counted by the counters 20, 21 and 22 (counter 19).
Counts the output pulses of the frequency divider 14), the addresses of the image memories 23, 24, 25 and 26 to be read out are incremented, and the image information of each color is stored in each LED array 27, 28, 29 and 30 for each line. Sent to

Thus, the photosensitive drums 11m, 11c,
At the time of image formation on 11k, writing is performed by shifting the exposure timing back and forth so as to cancel out the image position shift.

Therefore, according to this embodiment, the photosensitive drum 11
Is set to 1/3 of the diameter of the transfer drum 12, and the rotation period of the photosensitive drum 11 is set to one-third (1/3) of the rotation period of the transfer drum 12, as shown in FIG. The cycle of the transfer position deviation change is the shortest and is equal to the cycle of one rotation of the transfer drum 12. Therefore, since the correction only needs to be performed for one rotation of the transfer drum 12, the correction can be easily performed.

On the other hand, since the images of the respective colors overlap each other on the transfer drum 12, good images are obtained without any misregistration of the images of the respective colors of yellow, magenta, cyan and black, and the image quality of color printing is improved. effective.

[0024]

As described above, in the color printing apparatus according to the present invention, the rotation period of the image forming medium 1i is set to be a fraction of the rotation period of the transfer medium 2, while Rotation signal output means 3 for outputting a corresponding signal
And a predetermined reference image-bearing medium 1i selected from the image-bearing medium 1i, and the displacement of each of the other image-bearing media 1i with respect to the reference image-bearing medium 1i is determined by a signal output from the rotation signal output means 3. Storage means 4 for storing, for each image forming medium 1i, as correction data based on the above information.
And the correction data stored in the position storage unit 4,
Since the correction means 5 for correcting the scanning interval when an image is formed on the image forming medium 1i is provided, the period of the positional deviation fluctuation can be minimized and the correction can be performed for one rotation of the transfer medium 2, so that the correction can be performed. By easily performing the correction based on the correction information for one rotation, when the image formed on each image forming medium 1i is transferred to the transfer medium 2, the overlapping position of each image is matched, so that the color This produces an effect of obtaining a high-quality image without displacement and improving the image quality of color printing.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the principle according to the present invention.

FIG. 2 is a color printing apparatus according to an embodiment of the present invention.

FIG. 3 is a block diagram according to an embodiment of the present invention.

FIG. 4 is a block diagram at the time of position shift measurement according to the embodiment of the present invention.

FIG. 5 is an explanatory view according to an embodiment of the present invention.

FIG. 6 is a diagram showing a pattern of positional deviation.

[Explanation of symbols]

 1i (11) Image forming medium (photosensitive drum) 2 (12) Transfer medium (transfer drum) 3 Rotation signal output means 4 Position storage means 5 Correction means

────────────────────────────────────────────────── ⁶ Continuation of the front page (51) Int.Cl. ⁶ Identification symbol FI H04N 1/23 103 B41J 3/00 B (56) References JP-A-61-83557 (JP, A) JP-A-61-282860 (JP, A) JP-A-63-81371 (JP, A) JP-A-2-120762 (JP, A) JP-A-3-261973 (JP, A) JP-A-57-167034 (JP, A) JP-A-63-151970 (JP, A) JP-A-64-73369 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 13/01 G03G 15/01-15/01 117

Claims (1)

(57) [Claims] 1. A method comprising a rotating body rotating at a predetermined cycle.
An image forming medium (1) that forms an image by scanning at regular intervals
i, i = 1, to m), and these image forming media
(1i) is disposed around the image forming medium (1).
By transferring the image formed in i) in an overlapping manner,
Transfer medium (2) comprising a rotating body for forming an image of
In the color printing apparatus, the rotation cycle of the image forming medium (1i)
(1) Integer fraction of rotation period of (2)While Outputting a signal corresponding to the rotation angle of the transfer medium (2);
Rotation signal output means (3); A predetermined reference image carrier from the image carrier medium (1i)
The medium (1i) is selected, and the reference image-carrying medium (1i) is selected.
The amount of misalignment of each of the other image-bearing media (1i) with respect to
Information on the signal output from the rotation signal output means (3)
As the correction data based on each image forming medium (1i)
Position storage means (4) for storing the Based on the correction data stored in the position storage means (4)
Scanning when forming an image on the image forming medium (1i)
Correction means (5) for correcting the interval of Features
Color printing device.