JPH11143163A - Color printing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color printing device in which the cost thereof is prevented from being increased and the printing processing speed is increased in the tandem type color printing device. SOLUTION: Printing data outputted from a host computer 24 are outputted to an I/F controller 20 and after being converted to video data, they are outputted to LED heads 19Y-19BK through a head controller 22 and printed on a recording paper. While the video data are successively outputted to the controller 22 from the controller 20 in the meantime, a vertical synchronizing signal (VSYNM) and a horizontal synchronizing signal (HSYN) for outputting the video data are generated by a logic circuit 26. This generation processing of the signals is executed so that an error is not adjusted by outputting the signal (VSYNM) every color but the output of the signal (VSYNM) of the other color is adjusted by adjusting the reference timing of the signal (VSYNM) to the LED head of black (BK). Therefore, the device is provided with counters for respective colors, however, it is good that they are the single counter, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tandem type color printing apparatus.

[0002]

2. Description of the Related Art In recent years, a tandem type color printing apparatus using an LED array head as optical writing means and using image forming units for each color has been adopted. In such a color printing apparatus, for example, image forming units using yellow (Y), magenta (M), cyan (C), and black (BK) toners are arranged, and charging, exposure, and development are performed in each image forming unit. Then, a transfer process is performed, and an image is formed on a recording sheet.

In such a case, the exposure timing is controlled by a vertical synchronizing signal (VSYN), and the exposure timing of each color can be corrected in TW units by setting so as to correct the displacement in the sub-scanning direction. here,
Conventional methods for correcting misregistration in the sub-scanning direction include a method using a hardware circuit and a method using software. (A) For example, in the method using a hardware circuit, the start timing of the vertical synchronizing signal (VSYN) is output to a counter for each color, and this counter value is set according to the amount of displacement in the sub-scanning direction. (B) On the other hand, the software method performs a count process for each TW by a software counter, and outputs a vertical synchronizing signal (VSYN) and a horizontal synchronizing signal (HSYN) from an output port.

[0004]

However, the conventional apparatus has the following problems. (A) First, in the method using a hardware circuit, the higher the resolution of an image, the more the number of bits of the counter increases. For example, a plurality of counters are required for continuous printing of two or more sheets. In addition, the circuit becomes complicated and causes an increase in the cost of the device. (B) On the other hand, in the method using software, when the resolution of an image is high or the printing speed is increased, the period of TW is shortened, and the ratio of the vertical synchronization (VSYN) processing for each TW to the entire program is increased. For this reason, it is impossible to speed up the printing process due to the limitation of the software processing speed.

An object of the present invention is to provide a color printing apparatus which can prevent an increase in the cost of the apparatus and perform printing at a high speed in view of the above-mentioned conventional circumstances.

[0006]

According to a first aspect of the present invention, there is provided a tandem-type printing apparatus capable of multicolor printing by superposing toner images of a plurality of colors to solve the above-mentioned problems. Can be set, and 1
A horizontal synchronization signal generation circuit serving as a reference for output timing of print data of each color for each line; and a software counter for counting a horizontal synchronization signal output from the horizontal synchronization signal generation circuit. This can be achieved by providing a color printing apparatus that outputs a vertical synchronization signal serving as a reference for page printing based on the output.

Here, the horizontal synchronizing signal generation circuit includes a counter, a latch circuit, a selector, and the like.
The horizontal synchronizing signal is generated by the selection signal output from. The vertical synchronizing signal is generated by counting the horizontal synchronizing signal by a software counter that counts the horizontal synchronizing signal.

With such a configuration, the horizontal synchronizing signal can be generated by a hardware circuit, and the vertical synchronizing signal can be generated by a software counter. A horizontal counter can be generated by a small number of counters as a whole without using a plurality of counters for the same color. The synchronization signal and the vertical synchronization signal can be generated together.

A second aspect of the present invention is the configuration according to the first aspect of the present invention, wherein the counting of the horizontal synchronizing signal is performed based on an output of a vertical synchronizing signal serving as a reference for a printing process of a predetermined color.

That is, the horizontal synchronization signal is counted based on the output timing of the vertical synchronization signal of a predetermined color among the plurality of colors, and the output timing of the vertical synchronization signal of another color is set. With this configuration, the printing process for other colors can be automatically set by the software counter in accordance with the output timing of the vertical synchronization signal of the predetermined color, and the burden on the hardware circuit and software can be reduced. it can.

According to a third aspect, in the second aspect, the predetermined color is, for example, black (BK). However, for example, it is not limited to black (BK),
A configuration may be used in which a vertical synchronization signal of another color is used as a reference.

According to a fourth aspect, in the first, second and third aspects, the plurality of colors are, for example, yellow (Y), magenta (M), cyan (C), black (B
K).

In this case, as described above, black (BK)
With reference to the vertical synchronizing signal, the printing of yellow (Y), magenta (M), and cyan (C) colors sets the vertical synchronizing signal of each color with reference to the output of the vertical synchronizing signal.

The plurality of colors are not limited to yellow (Y), magenta (M), cyan (C), and black (BK), but may be other color combinations.
The color is not limited to four colors, but may be six colors, eight colors,....

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 2 is an overall configuration diagram of a color printing apparatus for explaining an embodiment of the present invention. The color printing apparatus according to the present embodiment is a so-called tandem type color printer.

In FIG. 1, a color printer 1 includes a paper supply / conveyance mechanism 2, an image forming unit 3, and a fixing unit 4. The paper supply / transport mechanism 2 includes a paper cassette 5 in which paper P is loaded and stored, and a paper transport system 6. Further, the paper transport system 6 transfers the paper P
Roller 7, a paper transport path 8 for transporting the paper P carried out by the paper feed roller 7, a standby roll 9 for feeding the paper in a state where the paper position matches the toner image, and a transport not shown. It comprises a roll, a standby sensor 10 for detecting the passage of paper, a paper discharge sensor 11, and the like.

The rotation of the paper feed roller 7 causes the paper feed cassette 5
The sheet P carried out from the printer is sent to the standby roll 9 through the sheet transport path 8 and sent to the image forming unit 12 at a timing coincident with a toner image formed on a photosensitive drum described later. Further, while the paper P moves on the image forming unit 12,
Each of the image forming units 13, 14, 15, 16
Thus, the toner image is transferred. Thereafter, the sheet P on which the heat fixing process is performed by the fixing unit 4 and the toner image is formed is discharged out of the apparatus.

The above-mentioned fixing unit 4 comprises a heat roll 4a and a press roll 4b. While the paper P is nipped and conveyed between the heat roll 4a and the press roll 4b, a transfer process to the paper P is performed. .

On the other hand, the image forming unit 3 includes the yellow (Y), magenta (M), cyan (C),
Four (BK) image forming units 13 to 16
And arranged in the above-described arrangement order. Also,
The three image forming units 13 to 15 are units that transfer corresponding yellow (Y), magenta (M), and cyan (C) toners onto the paper P and perform color printing based on subtractive color mixture. (BK) image forming unit 1
Reference numeral 6 denotes a monochrome unit.

Each of the image forming units 13 to 16 has the same configuration except for the (color of) the developer contained in the developing container, and includes a charger, an LED head, and the like near the peripheral surface of the photosensitive drum.
In this configuration, a developing device and a transfer device are sequentially arranged. Where 4
The configuration of the image forming units 13 to 16 will be described as an example of the image forming unit 15 for cyan as a representative of the image forming units 13 to 16. The photosensitive drum 18 has a peripheral surface made of, for example, an organic photoconductive material.
A charger (not shown), an LED head 19 (19C), a developing unit 17, and a transfer roll (not shown) are sequentially arranged.

The photosensitive drum 18 rotates in the direction of the arrow, and first charges the peripheral surface of the photosensitive drum 18 uniformly by applying a charge from a charger. Next, the LED head 19 (19
An electrostatic latent image is formed on the peripheral surface of the photosensitive drum 18 by the exposure from C), and a toner image is formed by a developing process by the developing device 17. At this time, the toner image formed on the peripheral surface of the photosensitive drum 18 is based on cyan (C) toner stored in the developing container 17. The toner image formed on the peripheral surface of the photosensitive drum 18 in this manner is
The paper P reaches the position of the transfer roll with the rotation in the direction of the arrow, and is conveyed over the image forming unit 18 by the transfer roll.
Is transferred to

The toner image transferred onto the upper surface of the sheet P is conveyed in the direction of the arrow, and the yellow (Y) toner formed on the sheet P by the other image forming units 13 and 14 having the same configuration as described above. The fixing unit 4 performs a heat fixing process together with the magenta (M) toner and performs color printing based on subtractive color mixture. For example, if the print image is blue, the magenta (M) toner is transferred from the image forming unit 14 to the paper P based on the subtractive color mixture, and then the cyan (C) toner is transferred from the image forming unit 15 to the paper P. , To achieve a blue image. For example, if the print image is red, the image forming unit 13 sends a yellow (Y)
Is transferred to the sheet P, the image forming unit 14
To transfer the magenta (M) toner onto the paper P to realize a red image.

Each of the image forming units 13 to 16 or each of the image forming units 13
16 is likely to cause an error, and this error is caused by a vertical synchronization signal (VS) serving as a reference for starting printing of each color.
YNx) is adjusted by shifting the output timing.

FIG. 1 shows a color printer 1 having the above-described mechanism.
Is shown. The control circuit of the color printer 1 includes an interface controller (hereinafter, referred to as an I / F controller) 20, a printer controller 21, a head controller 22, and an LED head unit 23.
A host computer 24 which is an external device is connected to the F controller 20.

The I / F controller 20 prints one sheet of paper P in accordance with print information output from the host computer 24.
Create corresponding bitmap data on a one-to-one basis. The printer controller 21 includes a CPU 25 and a logic circuit 26.
The CPU 25 performs control in accordance with a program stored in a ROM (not shown), for example, bitmap data (video data) created by the I / F controller 20.
Is output to the head controller 22.

The output of the bit map data to the head controller 22 is performed in accordance with the vertical synchronizing signal (VSYNx) and the horizontal synchronizing signal (HSYNx) output from the printer controller 21. In particular, the video data for each line is The signal is output to the head controller 22 according to the output of the synchronization signal (HSYNx).

The bitmap data (video data) supplied to the head controller 22 is supplied to the above-mentioned LED heads 19Y, 19Y by the head controller 22.
M, 19C, and 19BK.

Here, the above-mentioned vertical synchronizing signal (VSYN)
x) and the horizontal synchronizing signal (HSYNx) are generated by the logic circuit 26 in the printer controller 21. 3 and 4 are circuit diagrams illustrating specific examples of the logic circuit 26. The circuit shown in FIG. 3 is a horizontal synchronizing signal (HSYN).
The circuit shown in FIG. 4 has a vertical synchronizing signal (V
SYN), and a logic circuit 26 is constituted by these two circuits.

First, in FIG. 3, the logic circuit 26 comprises a counter 28, a decoder 29, a latch circuit 30, and selectors 31 to 33. The counter 28 is supplied with a write signal TW generated by an oscillation circuit (not shown). The counter 28, which is a ring counter, counts the input write signal TW and sets the counter value to 0 or 1 every time the write signal TW is input. , 2, 3, 0,... The count data is supplied to the A and B inputs of the decoder 29. The decoder 29 outputs the Y signal according to the 2-bit data input to the A input and the B input.
0 to Y3 to horizontal synchronization signal (HSYN0 to HSYN3)
Is output. For example, A input is “L”, B input is “L”
At this time, the output Y0 is selected, and a horizontal synchronization signal (HSYN0) is output from the output Y0. For example, when the A input is “H” and the B input is “L”, the output Y1 is selected, and the output Y1 outputs a horizontal synchronizing signal (HSYN1). Further, for example, when the A input is “L” and the B input is “H”, the output Y
2 is selected, the output Y3 is selected when the A input is “H” and the B input is “H”, and the corresponding outputs (Y2, Y2) are selected.
3) to output horizontal synchronization signals (HSYN2, HSYN3).

On the other hand, the CPU 25 outputs selection data for selecting any one of the above-mentioned horizontal synchronizing signals (HSYN0 to 3). This selection data has a 6-bit configuration and is supplied to inputs D0 to D5 of the latch circuit 30. At the same time, a latch signal is also output from the CPU 25, and the above-described selection data is latched in the latch circuit 30. The selection data latched in this manner is sequentially output to the selectors 31 to 33 two bits at a time in synchronization with the output of the horizontal synchronization signal (HSYNx).

For example, first, a vertical synchronization signal (HSYNK) corresponding to black (BK) is output from the decoder 29 (logic circuit 26) to the CPU 25, and based on the supply of the vertical synchronization signal (HSYNK), the CPU 25 Perform processing. That is, first, a 2-bit selection signal is output from the outputs “00” and “01” of the latch circuit 30, supplied to the selector 31, and the selector 31 outputs a horizontal synchronizing signal (HSYNY). Next, a 2-bit selection signal is supplied from the outputs “02” and “03” of the latch circuit 30 to the selector 32, and the selector 32 outputs a horizontal synchronizing signal (HSYNM). Further, a 2-bit selection signal is supplied to the selector 33 from the outputs "04" and "05" of the latch circuit 30, and the selector 33 outputs a horizontal synchronization signal (HSYNC).

With the above configuration, the horizontal synchronizing signals (HSYN0, HSYNK) are first output from the decoder 29, and then the horizontal synchronizing signals (HSH) are sequentially output from the selectors 31, 32, 33.
YNY), (HSYNC), and (HSYNC) are output. FIG. 5 is a time chart showing the output timing. As shown in the figure, every time the write signal TW is output four times, the horizontal synchronization signals (HSYN0, HSYNK) to (HSYN) based on the vertical synchronization signal (VSYNK) are used.
4, HSYNC) are sequentially output.

Image alignment is performed by finely adjusting each of the other colors in units of 1/4 dot based on black. Therefore, the ratio of the cycle of the write cycle signal TW to the cycle of the horizontal synchronizing signal (HSYNx) is 1: 4, and if the original image data is 600 DPI, the LED head 19
Y, 19M, 19C, 19BK are 4 times 2400DP
The print processing operation is performed at the dot pitch of I. Therefore, the head controller 22 converts one line of image data (VIDEOx) sent from the I / F controller 20 in synchronization with the horizontal synchronization signal (HSYNx) into four lines of data in accordance with the write cycle signal TW. Divided into LE
The data is sent to the D heads 19Y, 19M, 19C, and 19BK, respectively.

Next, generation of the vertical synchronizing signal (VSYN) will be described. As described above, it is generated by the circuit shown in FIG.
That is, the vertical synchronizing signals (VSYNK-
VSYNC) is output. The selection data has a 4-bit configuration, is supplied to inputs D0 to D3 of the latch circuit 34, and is simultaneously latched by the latch circuit 34 by a latch signal output from the CPU 25. The selection data latched in this manner are D-type flip-flops (hereinafter simply referred to as DF / F) 35a to 35a.
Output to 35d.

That is, the output "00" of the latch circuit 34
Outputs a selection signal to the D terminal of the DF / F 35a to output the vertical synchronization signal (VSYNC) supplied to the DF / F 35a to the I / F controller 20.
Also, the DF / F35 is output from the output "01" of the latch circuit 34.
By outputting a selection signal to the D terminal of b, DF /
The vertical synchronizing signal (VSYNY) supplied to F35b is
/ F controller 20. Further, the DF / F 35 is output from the outputs "02" and "03" of the latch circuit 34.
By outputting a selection signal to the D terminals c and 35d, the vertical synchronization signals (VSYNC) and (VSYNC) supplied to the DF / Fs 35c and 35d are output to the I / F controller 20.

The outputs of the vertical synchronizing signal (VSYN) and the horizontal synchronizing signal (HSYN) have the relationship shown in FIG. That is, while the vertical synchronizing signal (VSYNx) corresponding to the printing of one page of the paper P is output, the horizontal synchronizing signal (HSYNx) corresponding to the printing timing of each line is output, and the horizontal synchronizing signal (HSYNx) is output. , Video data (bitmap data) is output in correspondence with. Next, the processing operation of this embodiment will be described.

First, when print data is supplied from the host computer 24, it is converted into video data (bitmap data) by the I / F controller 20. This video data is stored in the vertical synchronizing signal (VSYNx)
And output to the head controller 22 according to the output timing of the horizontal synchronizing signal (HSYNx).

Here, as described above, the vertical synchronizing signal (VS
YNx) and the horizontal synchronizing signal (HSYNx) are created by the logic circuit 26 and supplied to the I / F controller 20. FIG. 7 is a flowchart for explaining the output timing of the vertical synchronization signal (VSYNx) and the horizontal synchronization signal (HSYNx), and the output timing of the video data. 8 and 9 are time charts.

In the description of this embodiment, first, the case without the error adjustment shown in FIG. 8 will be described with reference to FIGS. 7 and 8, and then the case with the error adjustment will be described with reference to FIGS. 7 and 9. I do. <If there is no error adjustment> First, if there is no error adjustment, it is determined whether or not there is a request to turn on the vertical synchronizing signal (VSYN) in the process (step (hereinafter referred to as S) 1) shown in FIG. The first request is output from the CPU 25. Here, if there is no request yet (S
It is determined whether the counter (VSTACNTY) is "0" (S2). Here, the counter (VSTACN)
TY) is a so-called software counter. If the count value of this counter is not "0" (S2 is Y (yes)), the counter value of this counter (VSTACNTY) is decremented by -4. However, this counter (VSTACNT)
Y) is assumed to be initially reset to "0". Therefore, the first decision (S2) is N (No).

For this reason, the flow shifts to judgment (S3), and the counter for magenta (M) (VSTACNTM)
Is not “0”. This counter (VSTA
CNTM) is also a software counter, which is initially set to "0", and therefore N (No), and the cyan (C) counter (VSTACNTC) is "0".
Is determined (S4). This determination is the same (S4 is N (No)), and it is further determined whether the black (BK) counter (VSTACNTK) is "0" (S5), and the process returns to the first determination (S1).

Here, the vertical synchronizing signal (V
SYN) If there is an ON request (S1 is Y (yes)), the yellow (Y) counter (VSTACNT)
An initial value Y is set in Y) (S6). This initial value is shown in FIG.
The initial value of “4728” corresponds to the distance from the standby roll 9 shown in FIG. 1 to the position where the yellow (Y) image forming unit 13 is provided, and It is calculated from the speed (v). For example, the above-mentioned initial value is the LED head 19 of this example.
It is assumed that the dot pitch of Y to 19BK is 600 DPI, the period of the horizontal synchronizing signal (HSYN) is 4 TW, and the distance from the standby roll 9 to the yellow (Y) photosensitive drum is 50 mm.

As described above, the counter (VSTACN)
When the initial value is set to (TY), the above-described determination (S)
3) to (S5) are repeated, and the process returns to the initial judgment (S1). Here, the output of the vertical synchronizing signal (VSYN) is confirmed again (S1). At this point, the request is off, and the CPU 25 determines whether the count value of the counter (VSTACNTY) is "0" (S2). . At this time, the counter value of the counter (VSTACNTY) is still at the initial value ("4728") (Y in S2), and then the value of the counter (VSTACNTY) is in the range of "1" to "4". Is determined (S7), and here the count value is “47”.
Since it is 28 ", 4 is subtracted from the value of the counter (VSTACNTY) (-4 is subtracted) (S8).

In the same manner, judgments (S3) to (S
5) After executing the determinations (S1, S2, S7), the above-described subtraction processing is repeated (S8). Periods A1 to B1 shown in FIG. 8 are this period. The paper P re-fed by the standby roll 9 during this time is conveyed toward the image transfer unit of the yellow (Y) image forming unit 13.

Thereafter, as a result of the above-described subtraction processing (S8),
When the value of the counter (VSTACNTY) reaches "1" to "4", the judgment (S7) becomes Y and the vertical synchronization signal (VS)
YNY) is turned on (output) (S9).

The output timing of the vertical synchronizing signal (VSYNY) is shown in FIG. In FIG. 8, the output of the vertical synchronizing signal (VSYNY) is indicated by negative logic, so that the vertical synchronizing signal (VSYNY) is output to the I / F controller 20 at the fall of the vertical synchronizing signal (VSYNY). .

Thereafter, the CPU 25 sets an initial value to a counter (VSTACNTM) for magenta (M) (S
10). Counter set at this time (VSTACNTM)
Is "9460". This value is also calculated from the mechanism configuration shown in FIG. 1 and the paper transport speed (v). For example, the initial value described above is the same as LED
The dot pitch of the heads 19Y to 19BK is 600 DPI
And the period of the horizontal synchronizing signal (HSYN) is 4 TW, and the yellow (Y) photosensitive drum to the magenta (M)
Calculated assuming the distance up to 100 mm.
The above-mentioned count value is added with the remaining 4 TW.

Next, the count value of the counter (VSTACNTY) is reset to "0" (S11), and the judgment is made (S11).
4, S5), and after further performing the determinations (S1, S2), perform the determination (S3). The processing performed here counts the time during which the paper P on which the image transfer processing has been performed by the yellow (Y) image forming unit 13 is conveyed to the next magenta (M) image forming unit 14.
A vertical synchronizing signal (VS) is output at the timing for outputting video data for magenta (M) from the image forming unit 14.
YNM).

Also in this case, it is determined whether the counter for magenta (M) (VSTACNTM) has performed the subtraction processing up to the count value of "1" to "4" (S12), and the subtraction processing has been performed up to this count value. If not, the subtraction process of -4 is repeated. This period corresponds to the periods B1 to C1 shown in FIG.

Thereafter, as a result of the above-described subtraction processing (S13), the value of the counter (VSTACNTM) becomes "1" to "1".
When it reaches "4" (Y in S12), the vertical synchronization signal (VS
YNM) is output (S14). The output timing of the vertical synchronizing signal (VSYNCM) is the timing shown in FIG.

After outputting the magenta (M) vertical synchronizing signal (VSYNM) as described above, the initial value is set to the next cyan (C) counter (VSTACNTC) (S15). The counter to be set at this time (VSTA
The initial value of “CNTC” is “9460” which is the same as the initial value of the counter for magenta (M) described above.

Thereafter, the count value of the counter (VSTACNTM) is reset to "0", and judgment is made (S5, S1,
After performing S2 and S3), the determination (S4) is performed.
The next process is to count the time during which the paper P on which the image transfer process has been performed by the magenta (M) image forming unit 15 is conveyed to the next cyan (C) image forming unit 15. The output of the vertical synchronizing signal (VSYNC) is performed at an appropriate timing when the video data for cyan (C) is output from the image forming unit 15.

Also in this case, it is determined whether the counter for cyan (C) (VSTACNTC) has been subjected to the subtraction processing up to the count value of "1" to "4" (S17), and the subtraction processing has been performed up to this count value. If not, the subtraction process of -4 is repeated (S18). This period is C1 to D1 shown in FIG.
Corresponding to the period. Thereafter, the above-described subtraction processing (S18)
As a result, the value of the counter (VSTACNTC) is "1" to
When it reaches “4” (Y in S17), the vertical synchronizing signal (VS
YNC) is output (S19). The output timing of the vertical synchronizing signal (VSYNCM) is the timing shown in FIG.

After outputting the vertical synchronizing signal (VSYNC) for cyan (C) as described above, the initial value is set to the counter (VSTACNTK) for the next black (BK) (S20). At this time, the counter (VSTACNT)
The initial value set in K) is “9460” which is the same as the above-described counter value.

Thereafter, the count value of the counter (VSTACNTC) is reset to "0" (S21), and the judgment is made (S21).
After executing (1, S2, S3, S4), the determination (S5) is performed. In this process, an output of a vertical synchronization signal (VSYNC) necessary for performing image transfer processing by the image forming unit 16 for black (BK) is performed at an appropriate timing.

Also in this case, it is determined whether the counter (VSTACNTK) for black (BK) has performed the subtraction processing to the count value of "1" to "4" (S22), and the subtraction processing has been performed to this count value. If not, the subtraction process of -4 is repeated (S23), and during this period (D1 to E shown in FIG. 8).
1), a subtraction process is performed, and a counter (VSTACN)
When the value of (TK) reaches "1" to "4" (Y in S22), a vertical synchronization signal (VSYNCK) is output (S2).
4). Thereafter, the image forming unit 16 is driven by the output of the vertical synchronization signal (VSYNK) to perform monochrome printing on the paper P.

The above process is a color printing process for yellow (Y), magenta (M), cyan (C), and black (BK). <Case of Error Correction> Next, a case where error correction is performed will be described.

The time chart shown in FIG. 9 shows an example in that case. In this example, the output timing of the vertical synchronizing signal (VSYNY) is 1 TW earlier than in the case where there is no error, the output timing of the vertical synchronizing signal (VSYNM) is 1 TW later than in the case where there is no error, and the output timing of the vertical synchronizing signal (VSYNC). Is a case where it is set to be 2 TW slower than a case where there is no error. Therefore, in the case of the color printing apparatus 1 of this example, there is an error that the interval between the standby roll 9 and the first image forming unit 13 is slightly shorter than the standard, and the interval between the image forming units 13 and 14 is small. There is an error slightly longer than the standard, and the image forming unit 14
There is an error where the interval from to 15 is longer than the standard.
Note that, also in this processing, the flowchart is as shown in FIG.

When print data is supplied from the host computer 24, it is converted into video data (bitmap data) by the I / F controller 20 in the same manner as described above.
It is output to the head controller 22 in accordance with the output timing of the vertical synchronizing signal (VSYNM) and the horizontal synchronizing signal (HSYN) in this example.

First, the initial value set in the process (S6) shown in FIG. 7 is a count value "4727" which is "1" smaller than the standard case having no shift as described above. And
This count data is subtracted by 4 (S
8) When the count value reaches “1” to “4”, a vertical synchronization signal (VSYNY) is output. This timing is the timing shown in FIG.

In this way, the video data of yellow (Y) is output to the head controller 22, and the video data is output from the head controller 22 to the corresponding LED head 19Y. At this time, the output timing of the video data is shorter by 1 TW than the standard case, and corresponds to the displacement of the arrangement position of the yellow (Y) LED head 19Y.

Next, a counter (VS) for magenta (M)
TACNT) is set to an initial value. At this time, the count value set in the counter (VSTACNTM) is "94
61 ", and the count value is 1 TW from the standard position by the magenta (M) image forming unit 19M as described above.
Since the cycle is longer and the previous counting process is completed 3 TW earlier as can be seen from FIG.
A count value of “9461” which is larger by W is set.

Magenta (M) set in this way
Counter (VSTACNTM) for processing (S13)
Are sequentially subtracted by “4” and the counter (VSTA
When CNTM) reaches the count value of “1” to “4”,
A vertical synchronizing signal (VSYNM) is output. This timing is the timing shown in FIG.

In this manner, the magenta (M) video data is output to the head controller 22, and the head controller 22 outputs the video data to the corresponding LED head 19Y. At this time, the output timing of the video data is longer by 1 TW than the standard case, and corresponds to the displacement of the magenta (M) LED head 19M.

Next, a counter (VST) for cyan (C)
(ACNTC) is set to an initial value. At this time, the count value set in the counter (VSTACNTC) is “945”.
9 ", which is a value set from the arrangement position of the cyan (C) image forming unit 19C and the previous count data. That is, since the arrangement position of the image forming unit 19C is longer than the standard position by 2 TW and the previous processing is completed earlier by 3 TW, the count value at this time is "9459" which is one less than usual.

The counter (VSTACNTC) for cyan (C) set in this way is sequentially decremented by "4" by the process (S18), and the counter (VSTACNT) is subtracted.
When NTC) changes from "1" to "4", a vertical synchronization signal (VSYNC) is output. This timing is shown in FIG.

In this way, the cyan (C) video data is output to the head controller 22, and the head controller 22 outputs the video data to the corresponding LED head 19Y.

Next, a black (BK) counter (V
STACTNK), the counter (VSTACNTK) is set to a count value “9456”, and thereafter, in the process (S23), the counter is sequentially decremented by “4”, and the counter (VSTACNTK) is set to “1” to “4”. (S22 is Y), the vertical synchronization signal (VSYNC)
Is output. This timing is shown in FIG. 9. According to this timing, a vertical synchronization signal (VSYNK) for printing black (BK) is output.

In the same manner, a count value is set to a black (BK) counter (VSTACNTK), and the printing position (electrostatic latent image forming position) of the black (BK) on the photosensitive drum 18 is adjusted. Continue the printing process.

As described above, the vertical synchronizing signal (VSYN
Y) to (VSYNC), for example, black (B
K) in synchronization with the output timing of the vertical synchronizing signal (VSYNK), the vertical synchronizing signal (VSYN) for yellow (Y), magenta (M), cyan (C),.
Y), (VSYNC), (VSYNC),..., The output timing is counted by a software counter having a preset counter value, and is sequentially output.

With this configuration, the load on the software counter is reduced, and the influence on other programs is reduced. Further, since a software counter is used, the number of bits of the counter is increased as compared with, for example, a case where all are configured by hardware circuits, and the problem of providing a plurality of counters for each color is eliminated.

According to the above-described embodiment, the vertical synchronization of the other yellow (Y), magenta (M) and cyan (C) is based on the output timing of the black (BK) vertical synchronization signal (VSYNK). Signal (VSYNY),
Although (VSYNC) and (VSYNC) are set, a configuration other than black (BK) may be used as a reference.

The ratio between the vertical synchronizing signal (VSYNx) and the horizontal synchronizing signal (HSYNx) is not limited to TW, and other numerical values may be used as long as they are integer ratios.

[0073]

As described above, according to the present invention, the circuit configuration such as the counter can be reduced as compared with the case where the vertical synchronizing signal (VSYNCM) and the horizontal synchronizing signal (HSYN) are generated only by the hardware circuit. it can.

On the other hand, as compared with the case where the vertical synchronizing signal (VSYNM) and the horizontal synchronizing signal (HSYN) are generated only by the software counter, the load on the software is small even when high resolution and high speed processing are performed, and other programs can be used. No adverse effects.

Further, since both the horizontal synchronizing signal (HSYN) and the vertical synchronizing signal (VSYNM) are processed by a hardware circuit immediately before output, a high quality waveform can be obtained. Further, by combining a hardware circuit and a software counter, high-resolution printing processing is enabled, and further high-speed printing processing is enabled.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a control circuit of a color printer.

FIG. 2 is an overall configuration diagram of a color printing apparatus illustrating the embodiment.

FIG. 3 shows a part of a logic circuit, and a horizontal synchronizing signal (H
SYN).

FIG. 4 shows a part of a logic circuit, and includes a vertical synchronizing signal (V
SYNM).

FIG. 5 is a diagram illustrating output timings of four horizontal synchronization signals (HSYN).

FIG. 6 shows a horizontal synchronization signal (HSYN) and a vertical synchronization signal (V
FIG.

FIG. 7 is a flowchart illustrating an example of the present embodiment.

FIG. 8 is a time chart for explaining the embodiment.

FIG. 9 is a time chart for explaining the embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Color printer 2 Paper supply / transport mechanism 3 Image forming unit 4 Fixing device 4a Heat roll 4b Pressure contact roll 5 Paper feed cassette 6 Paper transport system 7 Paper feed roller 9 Standby roll 10 Standby sensor 11 Discharge sensor 12 Image forming unit 13 -16 Image forming unit 17 Developing device 18 Photoconductor drum 19, 19Y, 19M, 19C, 19BK, LED head 20 Interface controller 21 Printer controller 22 Head controller 23 LED head unit 24 Host computer 25 CPU 26 Logic circuit 28 Counter 29 Decoder 30 Latch circuit 31-33 Selector 34 Latch circuit 35a-35d D-type flip-flop

Claims (4)

[Claims] In a tandem printing apparatus capable of multicolor printing by superimposing toner images of a plurality of colors, a phase can be set from a control circuit, and output of print data of each color for each line. A horizontal synchronization signal generation circuit serving as a timing reference; and a software counter for counting the horizontal synchronization signal output from the horizontal synchronization signal generation circuit. Based on the output of the software counter, a vertical synchronization signal is generated. A color printing device characterized by outputting. 2. The method of claim 2, wherein the counting of the horizontal synchronizing signal is based on the output of a vertical synchronizing signal serving as a reference for a printing process of a predetermined color, and the output timing of a vertical synchronizing signal of another color is counted. The color printing device according to claim 1. 3. The color printing apparatus according to claim 2, wherein the predetermined color is black (BK). 4. The color printing apparatus according to claim 1, wherein the plurality of colors are yellow (Y), magenta (M), cyan (C), and black (BK).