JP2001331009A - Color image printing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set paper carrying speed higher at the time of monochromatic printing than at the time of color printing. SOLUTION: In this tandem type color image printing device where color images different among four image forming parts are superposed and printed on the same printing medium, printing width in a subscanning direction in each printing mechanism part is defined as (w). In the black image forming part, a black image is printed at the intervals of (4×w) on printing paper based on printing data K1, K5 and so on in 1st, 5th rows and so on; in the yellow image forming part 2Y, the black image is printed similarly at the intervals of (4×w) from the 2nd line of the printing paper based on printing data K2, K6 and so on in 2nd, 6th rows and so on; in the magenta image forming part 2M, the black image is printed similarly at the intervals of (4×w) from the 3rd line of the printing paper based on printing data K3, K7 and so on in 3rd, 7th rows and so on; and in the cyan image forming part 2C, the black image is printed similarly at the intervals of (4×w) from the 3rd line of the printing paper based on printing data K4, K8 and so on in 4th, 8th rows and so on.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for a color printer, a color copier, a color facsimile machine, etc., and comprises a plurality of image forming units arranged along a recording medium conveyance path. The present invention relates to a so-called tandem-type color image printing apparatus that prints a plurality of toner images superimposed on a conveyed recording medium.

[0002]

2. Description of the Related Art Conventionally, color image printing apparatuses (color printers) used for color printers, color copiers, color facsimile machines, etc. include so-called tandem type, intermediate transfer type, and batch type. A multiple development system, a transfer drum system, and the like are known. The tandem type color image printing apparatus simultaneously forms four color toner images of yellow (Y), magenta (M), cyan (C) and black (K) on the photosensitive drums of the respective image forming units, A toner image of each color is transferred onto a recording paper conveyed by a conveying unit such as a belt in a superimposed manner. Among the devices of this type, a color image of four colors can be printed at a high speed in one pass. Is the largest feature point.

FIG. 2 is a block diagram showing a configuration of an image data processing circuit in a tandem type color printer.

Here, image data 201 is transmitted as RGB data from a host device 200 such as a personal computer to an image data processing circuit (printer controller, hereinafter simply referred to as a controller 100). The controller 100 includes a control mechanism unit (CU) 110 as a main controller and a printer unit (PU) 120 as an engine controller.

[0005] In the CU 110 of the controller 100, the RGB data received via the interface (I / F) circuit 111 is stored in the reception buffer memory 112. The reception buffer memory 112 has a data conversion circuit 11
3 is connected, and the data conversion circuit 113
GB data is converted to YMCK data. The converted YMCK data is stored in the reception buffer memory 114.
Is stored in The reception buffer memory 114 is connected to a raster buffer memory 116 via a compression circuit 115. The YMCK data in the reception buffer memory 114 stores print data in page units in the raster buffer memory 116 while being compressed by the compression circuit 115. Will be expanded as The expanded YMCK data is supplied to the decompression circuit 117.
And is sent to the PU 120 side.

[0006] P from the CU 110 side of the controller 100
The YMCK data output to the U120 side is YMCK data as video data for actually printing on printing paper.
Each of the K color printing control units 122 to 125 is supplied. That is, the YMCK data is stored in the video buffer memory 121 in the PU 120, transferred from the video buffer memory 121 to each printer mechanism at a predetermined timing, and output as print data synchronized with the movement of the recording paper.

In the tandem-type color printer, the exposure, development, transfer, and fixing processes in the printer mechanism of each color are independently controlled by the print control units 122 to 125, and four color toners are simultaneously printed on one sheet of recording paper. An image can be formed. In this case, print data is supplied from the PU 120 to the print control units 122 to 125 for each color simultaneously and in parallel, and the printer mechanism for each color operates in series based on the print data for four colors. For this reason, the transport speed of the recording paper is determined only by the processing speed of the video data in the CU 110, and is compared with other intermediate transfer member systems, a batch multiplex development system, or a transfer drum system that sequentially performs four transfers. There is an advantage that the printing speed of the color can be doubled or more. By operating only one print control unit to form a one-color toner image, monochrome printing is also possible.

[0008]

As described above, a tandem-type color printer has an advantage that high-speed color printing is possible as compared with other color electrophotographic printers. However, in other color electrophotographic printer systems, when the monochrome printing speed is compared with the color printing speed, the former can be set to approximately four times the latter,
When performing monochrome printing with a tandem type color printer, the printing speed is inferior to the printing speed of other color electrophotographic printers.

That is, in monochrome printing in a tandem type color printer, when printing of monochrome image data is instructed from the host device 200, only one of the print control units 122 to 125 is involved in printing. Nevertheless, since the recording paper passes through the four image forming sections at the same speed as in the case of color printing, there is a problem that the same printing time is required in monochrome printing as in color printing.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and an object of the present invention is to set a paper conveyance speed in monochromatic printing such as monochrome printing to be higher than that in color printing. Another object of the present invention is to provide a simple tandem type color image printing apparatus.

Another object of the present invention is to provide a tandem type color image printing apparatus which can easily improve the quality of a color image.

[0012]

In a color image printing apparatus according to the present invention, a plurality of image forming units are arranged along a conveyance path of a recording medium, and a plurality of toner images are formed on the recording medium conveyed by the conveyance path. In a color image printing apparatus that prints in a superimposed manner, an image determination unit that determines whether the print command to the recording medium is a color image or a monochrome image.
A speed setting unit that switches and sets the conveyance speed of the recording medium according to the determination by the image determination unit, and a different color for each of the image forming units according to the determination by the image determination unit. Data control means for supplying one or both of image data and image data of the same color, wherein the speed setting means includes a case where the print command is a monochrome image, and a case where the print command is a color image print command. The transport speed is set higher.

In the color image printing apparatus according to the present invention, each image forming section is provided with a replaceable developing unit for forming a toner image. Each of them is provided with a developing unit for forming a toner image of the same color, and the conveying speed of the speed setting means is set to be four times as high as that for forming a color image.

In the color image printing apparatus according to the present invention, each image forming section has a developing unit for forming a black (B), yellow (Y), magenta (M), and cyan (C) toner image. A unit is provided, and from the data control means, an image forming unit provided with a developing unit for forming a black (B) toner image among the four image forming units is provided every other line. Is supplied to the other three image forming units, and the image data of every other line is supplied to the other three image forming units.
It is set to double.

In the color image printing apparatus according to the present invention, each image forming section is provided with a plurality of developing units so as to operate simultaneously or selectively.

In the color image printing apparatus according to the present invention, a developing unit for forming toner images of different colors and a developing unit for forming toner images of the same color are selected for each image forming unit. When printing a single-color image, the developing unit that forms a toner image of the same color in any one of the image forming units is operated, and the transport speed in the speed setting unit is set at the time of color image formation. Is set to four times as large as.

In the color image printing apparatus according to the present invention, each of the image forming units is provided with an exposing means for exposing at a different light emission intensity in accordance with the density of the image data from the data control means;
Two developing units that operate at different developing voltages and form toner images of the same color but different densities are provided, and the developing units are simultaneously operated to obtain different densities for the recording medium. Is formed.

[0018]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
An embodiment of the present invention will be described.

Embodiment 1 The first embodiment is a tandem-type color printer that prints by superimposing toner images of four colors. When performing single-color printing, for example, printing in black only (hereinafter, referred to as monochrome printing), black is used. Also in the other three image forming units, a developing unit for forming a black toner image is arranged, and the monochrome printing operation is shared by the four image forming units.

First, the configuration of a tandem type color printer will be described.

FIG. 1 shows a tandem LED for color printing.
FIG. 2 illustrates a configuration of a printer. In FIG. 1, a color image printing apparatus 1 includes four image forming units 2B, 2Y, 2
M and 2C are arranged in order from the insertion side to the discharge side (from right to left in the drawing) along the recording medium conveyance path. Of each image forming unit, 2B is a printing mechanism for transferring a black toner image to a recording medium, 2Y is a printing mechanism for transferring a yellow toner image to a recording medium, and 2M is a magenta toner image for a recording medium. And 2C constitute a printing mechanism for transferring a cyan toner image to a recording medium.

Four sets of image forming units 2B, 2Y, 2M, 2C
Indicate that the photoconductor drums 6 #, 6Y, 6Y are driven by the LED heads 3B, 3Y, 3M, 3C according to the respective image data.
Expose the photoconductor on M, 6C, and transfer rollers 4B, 4Y,
The toner image is transferred to a recording medium at 4M and 4C. Each of the image forming units 2B, 2Y, 2M, and 2C has a photosensitive drum 6 that rotates in the direction of arrow a, and a charging roller (primary charging roller, hereinafter referred to as a CΗ roller) that uniformly charges the surface of each photosensitive member. And 7, a developing unit 9 and a cleaning unit 15 for scraping off toner remaining on the surface of each photosensitive drum 6.

In the first embodiment, the developing unit 9
B, 9Y, 9M, and 9C are image forming units 2B, 2B, and 2C, respectively.
It is characterized in that it is detachably mounted in Y, 2M and 2C. The image forming units 2B, 2Y, 2M, 2
C are individually driven by motors not shown.

Here, the image forming units 2B, 2Y, 2M, 2
The developing process in C will be described. FIG. 3 is a diagram illustrating a configuration of an exposure device of a printing mechanism and a developing device. FIGS. 4A and 4B are diagrams showing a drum surface potential and a developing unit potential in the exposure process, respectively.

In FIG. 3, a charging roller 7, an LED head 3, and a developing unit 9 are arranged on the photosensitive drum 6, and the developing unit 9 is filled with toner and a developing roller (hereinafter referred to as a DΒ roller). ) 27a and a toner supply roller (hereinafter, referred to as an SB roller) 27b.
Is provided. Here, when the photosensitive drum 6 is rotated by the rotation of a developing / transfer process motor (not shown), a negative voltage is applied to the charging roller 7 from a high voltage power supply (not shown), and the surface of the photosensitive drum 6 is charged to a constant voltage. A primary charging portion (about -700 V) is formed. By irradiating the charged photosensitive drum 6 with light from the L３D head 3 and exposing only the position where printing is performed, only the charged potential of the exposed portion of the drum surface potential becomes −450 to −550V. And a latent image portion is formed.

Next, the developing process voltage in the developing unit will be described with reference to FIG. Figure (A)
In FIG. 7, the horizontal axis indicates the printing range (position) of the recording medium, and the vertical axis indicates the drum surface potential.

In the photosensitive drum 6, the primary charging portion is approximately -7
00V, and the exposed portion becomes -450 to -550V. On the other hand, in the developing unit 9, the D roller 27a connected to the high-voltage power supply for development and the SB roller 27b connected to the high-voltage power supply for toner supply have −300V and −45V, respectively.
A voltage of 0 V is applied. In the SB roller 27b,
A sponge roller is used to transport an appropriate amount of toner to the developing blade. The toner particles in the developing unit 9 have a property of being negatively charged.

In FIG. 4B, the horizontal axis indicates the printing range (position) of the recording medium, and the vertical axis indicates the potential of the DB roller and the toner moving therefrom to the photosensitive drum. As shown here, the developing bias is -300 V as the developing-side potential.
, The toner is supplied from the SB roller 27b in the direction of the D roller 27a, and adheres around the DB roller 27a to become a developing toner for the latent image on the photosensitive drum 6. Here, the charge amount of the toner particles is about -50 to -100 V, and the DB roller 27a
The upper toner potential is -400V to -350V.

As shown in FIG. 4A, the potential of the latent image portion of the photosensitive drum 6 is about -450 V to -550 V.
V, the range where no latent image exists (the range where no printing is performed)
Remains at -700V. Therefore, the portion of the photosensitive drum 6 irradiated with the light from the LED head 3 has a DB
The toner on the roller 27a moves so as to be attracted to the latent image position on the photosensitive drum 6, adheres to the photosensitive drum 6, and is developed as a visible image. In the portion of the photosensitive drum 6 to which the light from the LED head 3 was not irradiated, the surface potential was −700 V, and the toner potential was about −350 V to −350 V.
Because there is a potential difference of -200 V or more between 400 V and
The toner does not move from the DB roller 27a, and the image is not developed.

Next, the configuration of the LED head will be described. FIG. 5 is a block diagram illustrating a drive circuit of the LED head 3Y that performs an exposure operation based on, for example, yellow image data.

As shown in FIG. 5, the actual print data signal DA
TA is input to the LED head 3 together with the clock signal CLK. For example, LEDs arranged at a density of 300 DPI
In the printer having the head 3Y, the actual print data signal DATA is sequentially shifted and input to the shift registers SR1, SR2,... (SR2560) as bit data for 2560 dots. Next, the latch signal LOAD
Is input to the LED head 3Y, the bit data is output from the shift registers SR1, SR2,..., (SR2560) to the respective latches L # 1, LT2,.
There it is latched. Subsequently, at the timing when the print drive signal (strobe signal) STB is input to the LED head 3Y, the bits of the light emitting elements LD1, LD2,... (LD2560) for which the actual print data signal DATA is supplied as a high level value Only those corresponding to the data are lit. G1, G2, ..., (G2560) are gates, Tr
, (Tr2560) are switch elements, r1,
.., (r2560) are protection resistors, and VD is a power supply.

Next, the exposure function of the LED head having the above configuration will be described. The above-mentioned L３D head 3Y is LE
A D array, a substrate on which a drive IC for driving the LΕD array is mounted, and a selfoc lens array for condensing the light of the LED array, and the like. Then, the LED array is caused to emit light, the surface of the photosensitive drum 6Y is exposed, and an electrostatic latent image is formed thereon. Yellow toner is adhered to the photosensitive drum 6Y on which the electrostatic latent image is formed by the developing unit 9Y by electrostatic force to form a toner image. The photosensitive drum 6Y
A transfer belt 20 to be described later is movably disposed between the transfer roller 4Y and the transfer roller 4Y.

Similarly, the magenta image signal of the color image signal is input to the LED head 3M, the cyan image signal of the color image signal is input to the LED head 3C, and the color image signal of the color image signal is input to the LED head 3B. A black image signal is input, and a toner image of each color is formed. In the cleaning unit 15Y, the toner remaining on the surface of the photosensitive drum 6Y is scraped off and discharged to a waste toner container (not shown) arranged outside the printing mechanism by a screw shaft (not shown).

Returning to FIG. 1, the transport belt 20 is made of a high-resistance semiconductive plastic film and is formed as a seamless endless belt.
0, it is wound around the driven roller 31. Conveyor belt 2
The resistance value of 0 is within a range such that the recording medium S can be electrostatically attracted to the transport belt 20 and static electricity remaining on the transport belt 20 when the recording medium S is separated from the transport belt 20 can be neutralized. Shall be. The drive roller 30 is connected to a motor (not shown), and rotates the drive roller 30 in the direction of arrow C by the motor. The upper surface of the conveyor belt 20 is stretched between the photosensitive drums 6B, 6Y, 6M, 6C of the image forming units 2B, 2Y, 2M, 2C and the corresponding transfer rollers 4B, 4Y, 4M, 4C. Thus, both the photosensitive drum 6 and the transfer roller 4 are in contact with the transport belt 20.

A cleaning blade 33 is pressed against the drive roller 30 with the conveyor belt 20 interposed therebetween. This cleaning blade 33 is made of flexible rubber,
Or, it is composed of a plastic material or the like. The tip of the cleaning blade 33 is pressed against the conveyor belt 20,
The residual toner adhering on the surface of the conveyor belt 20 is scraped off to a waste toner tank 34.

Here, a recording medium feeding mechanism will be described.

In the color image printing apparatus 1 shown in FIG. 1, a paper feed mechanism is provided at a lower right portion in the housing. This paper feed mechanism includes a paper storage cassette 40, a hopping mechanism 47, and registration rollers 51 and 52. The paper storage cassette 40 includes a recording medium storage box 41, a push-up plate 42, and pressing means 43. A hopping mechanism 47 including a discriminating means 44, a spring 45, and a paper feed roller 46 is provided at a medium outlet of the recording medium storage box 41. The recording medium S is guided by the hopping mechanism 47 into the guides 48 and 4.
9 to reach a first registration roller 51 and a second registration roller 52 facing the transport roller 50. Note that the first registration roller 51 and the second registration roller 52 are both in pressure contact with the transport roller 50.

Reference numeral 53 denotes a medium guide, and reference numeral 54 denotes a suction roller. The suction roller 54 is pressed against the driven roller 31, and the registration roller 51,
The recording medium S sent from 52 to the medium guide 53 is
It is further charged and electrostatically attracted to the upper surface of the transport belt 20. For this reason, the suction roller 54 is made of a high-resistance semiconductive rubber material. A photo sensor 55 for detecting the leading end of the recording medium S is provided between the suction roller 54 and the first image forming unit 2Y.

Next, the operation of feeding the recording medium S by the above-described sheet feeding mechanism will be briefly described.

The recording medium S stored in the recording medium storage box 41 is pressed against a paper feed roller 46 by a pressing means 43 via a push-up plate 42. 44 is pressed by a spring 45. The recording medium S is selected and taken out one by one from the recording medium storage box 41 by the discriminating means 44.
When the paper feed roller 46 is rotated in the direction of arrow f by a motor (not shown) with this shape, the paper feed roller 46 and the discrimination means 4 are separated.
4 is guided by guides 48 and 49 and reaches between the conveyance roller 50 and the first registration roller 51. When the transport roller 50 is further rotated in the direction of arrow g by a motor (not shown), the recording medium S is guided from the second registration roller 52 to the medium guide 53 and reaches between the suction roller 54 and the transport belt 20.
The conveying belt 20 has a manual tray 56 wound around the driving roller 30 and the driven roller 31. The operator can manually insert the recording medium S along the manual tray 56 and the guide 57. it can. Reference numeral 58 denotes a photo sensor that detects the manually inserted recording medium S. The manually fed recording medium S is guided between the suction roller 54 and the transport belt 20 by the transport roller 50 and the second registration roller 52.

The driven roller 3 against which the suction roller 54 is pressed.
Numeral 1 is grounded so that the recording medium S can be electrostatically attracted to the transport belt 20 by a potential difference from the attracting roller 54. The recording medium S is a suction roller 5
4, the toner image is transferred while being conveyed from right to left in FIG. 1 at a speed corresponding to the rotation speed of the drive roller 30. This conveyor belt 2
The static eliminator 60 is provided on the upper surface on the side of the drive roller 30 at a predetermined distance. This static eliminator 60
The recording medium S attracted to and conveyed to the transport belt 20 is discharged, and the attracted state is released, so that the recording medium S can be easily separated from the transport belt 20. On the left side of the static eliminator 60, a photo sensor 61 for detecting the rear end of the recording medium S is provided.

Further, a paper guide 62 and a fixing device 63 are provided on the left side of the static eliminator 60. Fixing unit 63
Is to fix the toner image transferred thereon by heating the recording medium S transported by the transport belt 20. The fixing device 63 includes a heat roller 64 for heating the toner, and a pressure roller 65 for pressing the recording medium S while rotating while being in contact with the heat roller 64. A cleaning pad 66 made of felt is disposed above the fixing device 63 to clean toner adhered to the surface of the heat roller 64. A discharge port is provided on the left side of the fixing device 63, and a discharge stacker 67 is provided outside the discharge port. The printed recording medium S is discharged to the discharge stacker 67.

Next, a control circuit for controlling the operation of the tandem-type color printer having the above configuration will be described.

FIG. 6 is a block diagram showing the configuration of the printer control circuit. In the drawings, reference characters Y, Μ, C,
B corresponds to a printing mechanism for forming yellow, magenta, cyan, and black images.

A control circuit 70 includes a microprocessor, a ROM, a RAM, a timer, an IO port, and the like, and controls the entire operation of the color image printing apparatus 1 shown in FIG. The control circuit 70 includes the image forming units 2B, 2Y, 2
SB roller 2 composed of M and 2C conductive sponge rollers
7b, a DB bias power supply 72 for supplying power to the DB roller 27a of each image forming unit, and a charging for supplying power to the charging roller 7 of each image forming unit 2B, 2Y, 2M, 2C. And a transfer power supply 74 for supplying power for charging the transfer roller 4 of each of the image forming units 2B, 2Y, 2M, and 2C. Outputs of these power supplies 71 to 74 are connected to respective printing mechanisms (not shown) of yellow, magenta, cyan, and black, and are turned on / off for each color.

Also, the control circuit 70 includes the suction roller 54
Charging power supply 75 that supplies charging power to the
A static elimination power supply 76 for supplying high-voltage electric power for static elimination to is connected. The above power supplies 75 and 76 are on / off controlled by an instruction from the control circuit 70.

The control circuit 70 further includes a print control circuit 7
7 through the LEs of the image forming units 2B, 2Y, 2M, and 2C.
The D heads 3B, 3Y, 3M, 3C and the image memory 78 are connected. The print control circuit 77 controls the transfer of the corresponding print data and control data. The image memory 78 corresponds to the video buffer memory 121 described with reference to FIG. 2, and stores image data sent from a higher-level device via the interface circuit 79. That is, the LED heads 3B, 3
Transfer of print data supplied to Y, 3M, 3C and LE
By controlling the exposure time of D, control for forming an electrostatic latent image on the surface of the photosensitive drum 6 is performed. The interface circuit 79
The image data is equivalent to the CU 110 in FIG. 2, and separates image data transmitted from a higher-level device such as a host computer for each color into yellow image data, magenta image data, cyan image data, and black image data. Image data is stored separately.

The fixing device control circuit 80 drives a heater (not shown) in the heat roller 64 so as to keep the heat roller 64 in the fixing device 63 at a constant temperature. The motor driving circuit 81 includes motors 82 and 8 for driving transfer rollers corresponding to the respective image forming units 2B, 2Y, 2M and 2C.
3, 84, 85, motor 8 for driving the conveyor belt 20
6, a motor 87 for driving the paper feed roller 46 and the transport roller 50, a motor 88 for driving the fixing device 63, a motor 89 for moving the developing unit 2 toward and away from the photosensitive drum 6, and the like. Each of the motors 82 to 89 is connected to a corresponding driven unit by a gear or a belt (not shown).

The sensor driver receiver 90 drives the photo sensors 55, 58, 61 shown in FIG.
They receive the signal waveforms output by them and are connected to the control circuit 70.

The operation of the tandem type color printer shown in FIGS. 1 to 6 will be described below.

First, when a power supply (not shown) is turned on, the control circuit 70 in FIG. 6 executes a predetermined initial setting operation via the motor drive circuit 81. Thereafter, the fixing roller motor 88 is driven to rotate the heat roller 64, and the surface of the heat roller 64 is cleaned by the cleaning pad 66. At the same time, the heat roller 6 in the fixing device 63
By driving the fixing device control circuit 80 to perform the warm-up until the temperature of the color printer 4 reaches a predetermined temperature, the color printer enters the print mode. In the print mode, the fixing device control circuit 80 controls the heat roller 64 so as to always maintain a constant temperature. Even if the power is once turned on, if there is no printing operation for a certain period of time, the mode is temporarily switched to a sleep mode in which power supply to the heat roller 64 is cut off in order to reduce power consumption of the apparatus. In that case, the warm-up operation described above is executed again, and the operation returns to the print mode.

Next, when the temperature of the heat roller 64 reaches a predetermined temperature, the control circuit 70 drives the motor 87 via the motor drive circuit 81 to rotate the drive roller 30 to move the transport belt 20 in the direction of arrow e. . As a result, the residual toner and dust adhering on the surface of the transport belt 20 are scraped off to the waste toner tank 34 by the cleaning blade 33. Here, the motor 87 is stopped when the belt is fed slightly longer than the length of one round of the conveyor belt 20, and the cleaning operation ends. In addition, each printing mechanism unit B, Y,
In M and C, the motors 82, 8
3, 84 and 85, and the control unit 70 turns on the developing bias power supply 72, the charging power supply 73, and the SP bias power supply 71 for the respective colors, so that the charging roller 7, the DB roller 27a, and the SB roller 27b are turned on. And the like. Thus, the toner remaining on the surface of the photosensitive drum 6 is also scraped off by the cleaning blade 15, and the cleaning operation is completed.

When the initial operation of the color image printing apparatus 1 is completed as described above, the apparatus waits for image data sent from an external host device via the interface circuit 79.
Such an initial operation is also performed when a cover (not shown) of the device 1 is opened and closed. Here, the cover is provided so as to be openable and closable to take out the recording medium S and the image forming units 2Y, 2M, 2C, and 2B outside the housing. In order to release the jam of the recording medium S, Alternatively, it is opened and closed when the image forming units 2Y, 2M, 2C, and 2B are replaced.

Now, when image data is sent from the host computer, which is the host device, to the interface circuit 79, the control circuit 70 issues predetermined instructions to the interface circuit 79 and each image memory 78. This instruction is for instructing the interface circuit 79 to separate the received image data signal for each color, and for each image memory 78 to store the image data for each color in the storage area for each color. . As described above, the image memory 78 stores image data of each color to be printed on the recording medium S for one page.

FIGS. 7 and 8 are block diagrams showing an image data processing circuit constituting the CU unit on the printer side. Here, parts corresponding to the respective blocks in FIG. 2 are denoted by the same reference numerals.

In FIG. 7, an I / F control circuit 111 is connected to the host device 200, and receives a print command for printing on a recording medium and image data. The I / F control circuit 111 determines whether the image type is a color image based on these input signals.
Alternatively, a command (shown by a thin line in the figure) in a print command such as a color designation signal for determining whether the image is a monochrome image, a storage end signal, and RGB data (shown by a thick line in the figure) are output. The reception buffer 112 stores RGB data and related commands, and includes a data storage area 112a for each color and a command input area 112.
b.

The I / F control circuit 111 is connected to the host device 200
The command and the data transmitted from are analyzed to form a color designation signal, which is output to the data control circuit 118 shown in FIG. Command input area 112b and data storage area 1 respectively
The data is sequentially stored in the R buffer, the G buffer, and the B buffer 12a. When the I / F control circuit 111 further receives one page of image data from the host device 200 and stores it in the reception buffer 112, the data conversion circuit 113
And outputs a storage end signal.

The data conversion circuit 113 receives a storage end signal from the I / F control circuit 111 and converts RGB data into YMCK data. That is, the data conversion circuit 113 receives the RGB data line by line from the reception buffer 112, performs a conversion process, and converts the converted YMCK data into the reception buffer 114 connected at the subsequent stage.
Store the data. The reception buffer 114, like the reception buffer 112, includes a data storage area 114a divided for each color and a command input area 114b. In the data conversion circuit 113, when reading the RGB data from the reception buffer 112, the start address for each color is determined in advance.
The converted YMCK data is stored in the reception buffer 114 line by line like the K1, C1, M1, and Y1 line data while switching the address of the data storage area 114a for each color.

In the data conversion circuit 113, one page of RGB data is converted into YMCK data. For example, when m lines of YMCK data are stored in the reception buffer 114, a conversion end signal is output to the compression circuit 115. You. When the compression circuit 115 receives the conversion end signal from the data conversion circuit 113, the compression processing is started. In this compression processing, first, the first line (K1 line data) to the last line m (Km line data) of the black image are compressed, and then the first line (Y1 line data) to the last line (Ym line) of the yellow image are compressed. Line data), then from the first line (M1 line data) of the magenta image to the last line (Mm line data),
The cyan image is sequentially processed from the first line (C1 line data) to the last line (Cm line data).
The compression circuit 115 outputs compressed data to the data control circuit 118 every time the compression of one line of data is completed.

In addition to the method of sequentially performing the compression processing for each color, there is also a method of simultaneously processing each color for each line. Here, data processing is performed for each color in consideration of the procedure for storing the YMCK data from the data control circuit 118 at the next stage to the raster buffer 116 shown in FIG. This color-specific processing has the advantage that the address on the memory can be processed as a continuous address while data of one color is stored in the corresponding buffer.

The data control circuit 118 comprises a data write control circuit 21 and selectors 22 to 26 as shown in FIG. The raster buffers 116 are raster buffers 116K, 116Y, 116M, 11 for four colors.
6C.

The data writing control circuit 21 includes a compression circuit 11
5, the compressed data D and the write control signals CS1 to CS4 are input, and the I / F control circuit 111 also receives a color designation signal and the like. In this data write control circuit 21, 4
The compressed data D of each color is stored in a predetermined raster buffer 11.
In order to store in the 6K, 116C, 116M, and 116Y, selection of data D and switching of address A are instructed, and switching signals S1 and S2 and write control signal CS1
To CS4, and an address latch and data latch signal are output. In each of the selectors 22 to 26, data selection of only black data or selection of color data is performed according to the color designation signal, and the data content output from the data control circuit 118 to the raster buffer 116 will be described below. Is to switch to.

In the selector 22, the input data D is output from the output terminal A when the switching signal S1 goes to the “Η” level, and the data D is output to the output terminal B when the switching signal S1 goes to the “L” level. Selected to be output from the side. Further, in the selectors 23 to 26, when the switching signal S2 goes to the “Η” level, the data input to the B side becomes the output D, and when the switching signal S2 goes to the “L” level, the data is input to the A side. The data is selected to be output D.

In the data write control circuit 21 of the data control circuit 118, when it is determined that black printing is to be performed based on the color designation signal input from the I / F control circuit 111, the switching signal S2 is set to the “Η” level, Selector 23-2
The data input to the B side of 6 is output D. If it is determined that color printing is performed by the color designation signal,
The data write control circuit 21 sets the switching signal S2 to "L".
The level is selected so that the data input to the A side of the selectors 23 to 26 becomes the output D.

The image data processing circuit configured as described above determines whether the command is a print command for a single color image using only black or a print command for a color image on the basis of the color designation signal. Is instructed to switch the transport speed of the recording medium. When printing a single-color image, for example, monochrome printing, in the three image forming units other than black shown in FIG. 1, development is performed in advance to form black toner images instead of the developing units 9Y, 9M, and 9C. By arranging the unit 9B and controlling the printer mechanism as described below by the image data processing circuit described above, the monochrome printing operation is shared by the four image forming units.

FIG. 9 shows that the image data from the data control circuit 118 is stored in a predetermined raster buffer
It is a figure which shows the timing stored in 6K, 116Y, 116M, 116C. 5A is an address A, FIG. 5B is image data D, FIGS. 5C and 5D are switching signals S1 and S2, FIG. 5E is an address latch, and FIG. Data latches, (g) to (j), show write control signals CS1 to CS4.

First, the print control operation when color printing is designated will be described.

In the data control circuit 118, if it is determined by the color designation signal that the instruction is to print a color image, the switching signal S2 maintains the "L" level as shown by the broken line in FIG. The data D directly input from the data write control circuit 21 to the A-side input terminals of the selectors 23 to 26 is read out to each raster buffer 116. As a result, the K1 line data, the Y1 line data, the M1 line data, and the C1 line data are synchronized with the write control signals CS4 to CS1, respectively.
116M and 116C. When the compressed data of four colors for one page is stored in the line data storage area of each raster buffer 116 as line data of n lines, the image data expanded by the expansion circuit 117 is converted to the CU 110 shown in FIG. Is transferred to the PU 120 to start printing. On the PU 120 side, the compressed data read out line by line from the raster buffer 116 is decompressed by the decompression circuit 117 while being synchronized with each printing mechanism, and stored as video data in the video buffer memory.

Next, a printing control operation when monochrome printing is designated will be described with reference to FIG.

First, in the data write control circuit 21, both the switching signals S1 and S2 are set to "H" level. Then, the signal input to the input terminal D of the selector 22 is output from the terminal A side. Also, selectors 23 to 26
Then, the data input to the input terminal B side is output from the terminal D. Here, when K1 data which is black print data of the first line is input from the compression circuit 115 to the data write control circuit 21, the data write control circuit 21 sets the address A and the write control at a predetermined timing. Signal C
K1 data is output together with S4, and the K1 data is passed through selectors 22 and 23 to the K raster buffer 116K.
Is stored in the corresponding line data storage area. At this time, the remaining three raster buffers 116C, 116M,
There is no data output to 116Y.

Next, K2 data, which is black print data on the second line, is input from the compression circuit 115 to the data write control circuit 21 as Y1 data in FIG. At this timing, the switching signal S1 is switched to the “L” level, so that the selector 22 outputs the data input to the input terminal D from the terminal B. Thereafter, while the write control signals CS3 to CS1 are supplied, the switching signal S
1 is held at the "L" level, and the output terminal B of the selector 22 is connected to the input terminals B of the selectors 24-26.
4 to 26 output terminals D to the raster buffers 116Y, 1
16M and 116C. Thus, FIG.
In place of the Y1 data, M1 data, and C1 data of
K2, K3, which are black print data of the fourth line
By supplying the K4 data to the data control circuit 118, the address A, the data D, and the write control signals CS4 to CS are output from the data write control circuit 21 at a predetermined timing.
1 is output, and K2 data of the second line to K4 data of the fourth line are stored in the data storage areas of the first line of Y, M, and C, respectively.

The above processing is repeated for one page, that is, up to the n-th line, and K data for n lines is K, C, M, Y.
, Each of the raster buffers 116K, 116Y, 116M,
The data is divided into １ ／ and stored in 116C. One page of compressed data is transferred to each of the raster buffers 116K, 116Y,
After storing in 116M and 116C, the CU
Data transfer to the side is started. In other words, the PU side synchronizes with each printing mechanism unit,
The compressed data is read out for each line, decompressed by the decompression circuit 117, and the monochrome image data is stored in the video buffer memory 121.

Next, the operation of printing on the recording medium S taken out of the paper feed mechanism 40 based on the color or monochrome image data input to each print control unit will be briefly described with reference to FIGS. .

First, the control circuit 70 determines whether the data received by the color designation signal is a color image or a monochrome image. Hereinafter, a case where a color image is first received will be described. When it is determined that the received data is a color image, the developing units 9Y, 9M, and 9C of the image forming units 2Y, 2M, and 2C are used as they are.

The control circuit 70 instructs the motor drive circuit 81 to drive the motor 86 to rotate the paper feed roller 46. The rotation of the paper feed roller 46 causes the paper storage box 4
Only one recording medium S is sent to the guides 48 and 49. At this time, the motor drive circuit 81 controls the motor drive time so that the recording medium S is transported a distance slightly longer than the distance that the leading end of the recording medium S reaches between the transport roller 50 and the first registration roller 51. The motor 86 is driven for the time. Thereby, the leading end of the recording medium S is
The recording medium S is pressed between the first registration roller 51 and the first registration roller 51 to be slightly bent, and the skew of the recording medium S (distortion in the direction of the conveyance path) is corrected by using the bending.

Next, the control circuit 70 controls the motor drive circuit 8
1 drive the motors 82 to 88 through the respective image forming units 2
Photoconductor drums 6Y, 6M, 6 in Y, 2M, 2C, 2B
C, 6B, charging rollers 7Y, 7M, 7C, 7 #, developing rollers in each developing unit 2, sponge rollers, transfer rollers 4Y, 4M, 4C, 4B, driving rollers 30, transport rollers 50, and fixing device 63. The heat rollers 64 are respectively rotated. At the same time, the control circuit 70 turns on the charging power supply 73, the developing bias power supply 72, and the SΡ bias power supply 71 to turn on the image forming units 2Y, 2M, and 2 respectively.
A voltage is supplied to C, 2B charging rollers 7Y, 7M, 7C, 7B, DB roller 27a, and SB roller 27b. As described above, the surfaces of the photosensitive drums 6Y, 6M, 6C, 6 # of the image forming units 2Y, 2M, 2C, 2B are uniformly charged by the charging rollers 7Y, 7M, 7C, 7B, respectively, and the DB rollers 27a, SB The roller 27b is also charged to a predetermined high voltage shown in FIG.

Further, by rotating the transport roller 50 in the direction of arrow g, the recording medium S is transported by the first registration roller 51 and the second registration roller 52 to the medium guide 5.
It is guided to 3 and transported. As a result, the leading end of the recording medium S reaches between the suction roller 54 and the transport belt 20, and at this point, the control circuit 70 supplies the suction charging power supply 75
Is turned on to supply a voltage to the suction roller 54, so that the leading end of the recording medium S is
It is attracted to the conveyor belt 20 by the electrostatic force during one period.

When the transport roller 50 is further rotated in the direction of arrow g, the recording medium S is sucked by the transport belt 20 and is transported integrally with the belt in the direction of arrow e. When the leading end of the recording medium S is detected by the photo interrupter 55, the detection signal is transmitted to the sensor receiver driver 90.
Is supplied to the control circuit 70 via the. The recording medium S
When the trailing end of the paper feed roller 46 has passed, the control circuit 70
Receives a detection signal from the discriminating means 44 and instructs the motor drive circuit 81 to stop the motor 86.

When a certain period of time has elapsed since the start of rotation of the transport roller 50, the control circuit 70 issues a command to an image memory 78 storing image data, from which black data for one line is stored. Is transmitted to the print control circuit 77. The print control circuit 77 converts black image data for one line into a signal format that can be transmitted to the LED head 3B according to a command from the control circuit 70, and transmits the signal to the LED head 3B. In the LED head 3B, the LE corresponding to the transmitted image data is
D is turned on to form one line of an electrostatic latent image corresponding to the image data on the surface of the charged photosensitive drum 6B. Black toner is stored in the image forming unit 2B,
Black toner charged from the DB roller 27a is attached to the electrostatic latent image on the surface of the photosensitive drum 6B. Then, the photosensitive drum 6B continues to rotate, and the electrostatic latent images are successively developed with the black toner.

Thereafter, when the leading end of the recording medium S reaches between the photosensitive drum 6B and the transfer roller 4B, the control circuit 70
Then, the transfer power supply 73 is turned on, and the toner image on the surface of the photosensitive drum 6B is electrically transferred onto the recording medium S by the transfer roller 4B. The toner images are sequentially transferred onto the recording medium S by the rotation of the photosensitive drum 6B, and a black image for one page is transferred onto the recording medium S. From the above,
The transfer of the black image to the recording medium S by the image forming unit 2B ends. The transfer power supply 74 of the image forming unit 2B turns off a fixed time after the rear end of the recording medium S passes between the photosensitive drum 6B and the transfer roller 4B.

The recording medium S continues to move together with the conveyor belt 20 and is conveyed from the image forming section 2B to the image forming section 2Y, where a printing operation of a yellow toner image is performed. That is, the control circuit 70 issues a command to the image memory 78 storing the image data, and transmits one line of yellow image data from the image memory 78 to the print control circuit 77. The print control circuit 77 converts the yellow image data for one line into a signal format that can be transmitted to the LED head 3Y according to a command from the control circuit 70, and transmits the signal to the LED head 3Y. In the LED head 3Y, an LED corresponding to the sent image data is turned on, and one line of an electrostatic latent image corresponding to the image data is formed on the surface of the charged photosensitive drum 6Y. In this way, the yellow image data sent from the image memory 78 line by line forms an electrostatic latent image on the surface of the photosensitive drum 6Y one after another, and the yellow image data is lengthened in the sub-scanning direction. Exposure is completed when the image data is converted into a latent image. The following transfer operation of the yellow toner is the same as that of the above-described black toner, and the description thereof is omitted.

Further, the recording medium S is conveyed from the image forming unit 2Y to the image forming unit 2M, and the transfer of the magenta toner image by the image forming unit 2M is performed. When the transfer of the magenta toner image is completed, the recording medium S is transferred to the image forming unit 2C.
Transfer of the cyan toner image is performed. As described above, the toner images of the respective colors are transferred onto the recording medium S in a superimposed manner.

Thereafter, the recording medium S is sent to the static eliminator 60 by the conveyor belt 20, and the control circuit 70 turns on the static elimination power supply 76 to eliminate the charge of the recording medium S. The recording medium S is
The sheet is easily separated from the conveyor belt 20 due to the charge removal, and is separated from the conveyor belt 20 above the drive roller 30 and guided to the fixing device 63 by the paper guide 62. When the recording medium S is separated from the static eliminator 60, the control circuit 70
Turn off.

In the fixing device 63, the toner image is fixed on the recording medium S by the heat roller 64 which has already reached the temperature at which the image can be fixed and the pressure roller 65 which comes into pressure contact with the heat roller 64.
When the fixing is completed, the recording medium S is discharged to the discharge stacker 67. In the control circuit 70, this ejection can be detected by the photo interrupter 61 detecting the rear end of the recording medium S. When the discharge of the recording medium S is completed and the next recording medium is not conveyed, the control circuit 70 stops the motor 87 and the motor 88 via the motor driving circuit 81.
Further, the charging power supply 73, the SP bias power supply 71, and the DB bias power supply 72 are also turned off.

As described above, a color image can be recorded on the recording medium S fed from the paper feeding mechanism 40. The recording medium S inserted from the manual feed tray 56
Similarly, color image data can be recorded.

That is, when the operator sets the recording medium S on the manual feed tray 56, the control circuit 70 detects the recording medium S by the photo sensor 58 connected to the sensor receiver driver 90, and controls the motor drive circuit 81. The motors 82, 83, 84, 85, 85 are driven via the motor. Accordingly, the transport roller 50, the photosensitive drum 6, the charging roller 7, the DB roller 27a, the SP roller 27b, the transfer roller 4, the driving roller 30, and the heat roller 64 of the fixing device 63 of the image forming unit 2 of each color rotate. . At the same time, the control circuit 70 turns on the suction charging power supply 75 to supply a voltage to the suction roller 54. Since the transport roller 50 rotates in the direction of arrow g, the inserted recording medium S
The recording medium S is conveyed while being guided by the medium guide 53 by the registration rollers 52 of the recording medium S. The leading end of the recording medium S reaches between the suction roller 54 and the conveyance belt 20. At this point, the recording medium S
Is attracted to the conveyor belt 20 by electrostatic force between the suction roller 54 and the driven roller 31. Further, when the transport roller 50 rotates in the direction of arrow g, the recording medium S is transported in the direction of arrow e while being attracted to the transport belt 20.
Subsequent recording operations are the same as those described above, and will not be described.

Next, a case where the data to be printed is only black will be described. If the print command is, for example, an image of only black, that is, monochrome printing, the operator preliminarily sets the developing units 9Y, 9Y,
9M and 9C are replaced with those that form a black toner image.

FIG. 10 shows each LED from the video buffer.
This shows the data transfer timing to the head. Since the four printing mechanisms are provided side by side with respect to the transport belt, the driving timing of the LEDs in each printing mechanism differs with respect to the paper transport. As shown in FIG. 10, there is a difference of n lines in the printing position of the recording medium between the respective printing mechanisms. When the recording medium S reaches the position shown in FIG. The image data of the line is printed, and at the same time, the image data of the (3n + 1) th line is printed in the image forming unit 2B.

Image data is supplied to each of the image forming units 2B, 2Y, 2M, and 2C constituting the four printing mechanism units at the same speed as the color image printing operation. The amount of supplied image data is 1/4
Becomes For example, in the image forming unit 2B, the printing paper 1
Exposure may be performed every four lines in the raster direction by the LED head 3B supplied with black print data for printing 5,..., 1 + 4i lines. Therefore, by setting only the transport speed of the recording medium S to four times while keeping the data transfer ability as it is in the past, each image forming unit is allowed to share printing by 比較, and compared with printing of a color image. As a result, a printing speed four times higher can be realized.

FIG. 11 is a schematic diagram for explaining an example of a printing method on printing paper as a recording medium. The printing width in the sub-scanning direction in each printing mechanism unit is w, and the printing density in the sub-scanning direction is 600 DPI, which is the same as for printing a color image. In the black image forming section 2B, the first row, the fifth row,...
(4 ×) on the printing paper based on the printing data K1, K5.
The black image is printed at intervals of w), and in the yellow image forming unit 2Y, the print data K2 of the second row, the sixth row...
K6, black images are printed at the same interval (4 × w) from the second line of the printing paper. In the magenta image forming unit 2M, the print data K3, K7 of the third line, the seventh line. , Black images are printed at the same interval (4 × w) from the third line of the printing paper, and in the cyan image forming unit 2C, the print data K4, K8,. , Black images are printed at the same (4 × w) intervals from the third line of the printing paper.
Therefore, if the black image data is divided into four and stored in the raster buffer 116 and supplied to the video buffer at a conventional speed, the print density on the recording medium conveyed at four times the speed is reduced. A single monochrome image can be printed without the need for printing.

As described in detail above, by controlling the printing mechanism and setting the printing speed to four times that in the case of color printing, it is possible to form a single color image at four times the speed of color printing. A recording medium, for example, a recording sheet is conveyed, and the printing process can be performed at the printer unit at four times the speed. In other words, the black image printing time for one recording medium can be shortened to 1/4 as compared with the conventional one.

Note that the same printing speed as in the case of the above-described black can be realized even when printing other single-color images such as yellow, magenta, and cyan.

Embodiment 2 In the second embodiment, the monochrome printing operation is performed by sharing the monochrome printing operation among the four image forming units, similarly to the first embodiment. However, unlike the first embodiment, When the print command is monochrome, the developing units 9Y, 9M, and 9C of each image forming section are automatically replaced with black developing units, thereby saving the trouble of replacing the developing units.

FIG. 12 is a schematic diagram for explaining a printing method on printing paper according to the second embodiment. In the conventional monochrome printing, the printing of each line K1, K2,... Is all performed by the image forming unit B for forming a black toner image, whereas an image of a mixture of three colors is printed every other line. By doing so, the printing speed is increased. That is, utilizing the fact that a black image can be formed by subtractive color mixing when three colors of yellow, magenta, and cyan are superimposed, the same is applied to each of the three image forming units Y, M, and C, for example, for each even-numbered row. Black image data is supplied to form a black image by subtractive color mixing on every other line, and the image on the odd line is printed by the image forming unit B. Thus, the printing paper is sent to each image forming unit at twice the speed of color printing, and black (K), yellow (Y), magenta (M), and cyan (C) toner images are respectively formed. Even in this case, the printing process can be executed at twice the speed on the printer unit side. Other configurations are the same as those of the first embodiment, and different points will be described below.

FIGS. 13 to 17 show the timing of data transfer to each LED head. In FIG. 13, I1 is a line scan period from the first line to the n-th line, and is enlarged in FIG. Similarly, FIG.
3, I2 to I4 are n + 1 to 2n lines, 2n + 1 to 3
This is a line scan period for n lines and 3n + 1 to 4n lines, and is enlarged in FIGS. 15 to 17, respectively.

As shown in FIG. 13, a print command (PRINT-PR) is sent from the host device to the printer unit (PU) side.
N) is sent from the PU side to the control unit (C
When the print preparation completion signal (PRDY-P) is supplied to the U) side, the CU side starts a data transfer operation. Here, FSYNC-N is the page synchronization signal of the Nth page for each image forming unit, and is the FSYNC which is the Nth page synchronization signal for the black image forming unit B from the PU side to the CU side.
When NCK-N is supplied, black print bit data WDATA is transmitted to the PU side.

In FIG. 14, only the page synchronizing signal FSYNCK-N for the black image forming section B is "L", and the page synchronizing signal F for the remaining image forming sections Y, M, C is set.
SYNCY-N, FSYNCM-N, FSYNCC-N
Indicates the transfer data transmitted from the first line to the n-th line, which is transmitted when is “H”. LSYNCK is a line synchronization signal, WCLK is a data transfer clock, STB1
Reference numerals 4 indicate driving signals for driving the LED head.

At the data transfer timing of the first line,
The print data K1 for the first line of the printing paper is transferred from the first line of the K raster buffer 116K shown in FIG. 8, and null data is transferred from the remaining Y, M, and C raster buffers, and the respective LEDs are connected. Latched as print data in the memory. At the data transfer timing of the second line, null data is transferred from all raster buffers, and in the next third line, the K raster buffer 1
The print data K3 for the third line of the printing paper from the second line of 16K is latched by the LED head 3B.
Null data is transferred to the other LED heads 3Y, 3M, 3C.

The LED head 3B is driven by the drive signals STB1 to STB4 at the data transfer timing of the second line. The drive signal is divided into four, and the drive signal STB1 is divided.
The reason why the LED head is driven by (4) is that there is a limitation due to the capacity of the driving power supply.

FIG. 15 shows the timing of data transfer from the (n + 1) th line to the (2n) th line. Here, after the printing paper is conveyed by n lines, the page synchronizing signal FS for the image forming portion Y for black and yellow is also sent.
YNCY-N becomes “L”.

At the data transfer timing of the (n + 1) th line, the print data Kn + 1 for the (n + 1) th line of the printing paper from the first line of the K raster buffer 116K.
Is transferred, null data is transferred from another raster buffer, and latched in each LED head.
At the data transfer timing of the (n + 2) th line, the second line of the printing paper starts from the first line of the Y raster buffer 116Y.
The print data Y2 (= K2) for the line is transferred,
Null data is transferred from another raster buffer. After the data transfer timing, the STB signal drives the black and yellow LED heads 3B and 3Y. Further, in the (n + 3) th line, the (n + 3) th line of the printing paper starts from the second line of the K raster buffer 116K.
3) The print data Kn + 3 for the line is LED head 3
B, and null data is transferred from the Y, M, and C raster buffers.

FIG. 16 shows the third line from the (2n + 1) th line.
The timing of data transfer up to the n-th line is shown. When the printing paper is further conveyed by n lines,
The page synchronizing signal FSYNCM-N for the magenta image forming unit M becomes "L" together with black and yellow.

At the data transfer timing of the (2n + 1) th line, the print data K for the (2n + 1) th line of the printing paper from the first line of the K raster buffer 116K.
2n + 1 is transferred, null data is transferred from another raster buffer, and latched in each LED head. At the data transfer timing of the (2n + 2) th line, the Y raster buffer 116Y and the M raster buffer 11
From the first line of 6M, the (n +)
2) Print data Yn + 2 (= Kn + 2) for the line and print data M2 (= K2) for the second line of the printing paper
Is transferred to the LED heads 3Y and 3M, and the LED head 3
Null data is transferred to K and 3C. After the data transfer timing, the black, yellow, and magenta LED heads 3B, 3B are driven by the STB signal.
Y and 3M are driven. Further, in the (2n + 3) th line, the print data K2n + 3 for the (2n + 3) th line of the printing paper from the second line of the K raster buffer 116K.
Is transferred to the LED head 3B, and null data is transferred from any of the other raster buffers.

FIG. 17 shows the fourth line from the (3n + 1) th line.
The timing of data transfer up to the n-th line is shown. When the printing paper is further conveyed by n lines,
The page synchronization signals for all the image forming units K, Y, M, and C become "L".

At the data transfer timing of the (3n + 1) th line, the print data K for the (3n + 1) th line of the printing paper from the first line of the K raster buffer 116K.
3n + 1 is transferred, null data is transferred from another raster buffer, and latched in each LED head. At the transfer timing of the (3n + 2) th line, the Y raster buffer 116Y, the M raster buffer 116M, and the C
From the first line of the raster buffer 116C, the print data Y for the (2n + 2) th line of the printing paper
2n + 2 (= K2n + 2), the print data Mn + 2 (= Kn + 2) for the (n + 2) th line of the printing paper, and the second
The print data C2 (= K2) for the line is transferred to the LED heads 3Y, 3M, 3C, and null data is transferred to the LED head 3K. At this data transfer timing, all the LED heads of each color are driven by the STB signal. Further, at the data transfer timing of the (3n + 3) th line, the print data K3n + 3 for the (3n + 3) th line of the printing paper from the second line of the K raster buffer 116K is transferred to the LED head 3B, and Y,
Null data is transferred from the M and C raster buffers.

When the black print data is transferred to the LED heads of the four image forming units according to the above procedure, only the odd-numbered lines are printed in the black image forming unit B and the remaining lines are printed. Three color image forming units Y, M,
In C, only the printing of the even-numbered lines is performed by the subtractive color mixing effect. Therefore, by controlling the printing mechanism and setting the printing speed to twice that in color printing, the black image printing time on one recording medium can be reduced to half.

Embodiment 3 In the color image printing apparatus according to the third embodiment, among the four image forming units arranged along the conveyance path of the recording medium, three image forming units other than black are respectively provided with yellow, magenta, and cyan colors. A developing unit for forming a black toner image is disposed together with the developing unit.
The configuration is such that one developing unit is switched and used.

FIG. 18 is a diagram showing a color image printing apparatus according to the third embodiment. In the following, only parts different from the apparatus shown in FIG. 1 described in the first embodiment will be described, and corresponding parts will be denoted by the same reference numerals and description thereof will be omitted.

In the figure, image forming units 2C, 2M, 2Y
Has a black developing unit 9B together with the developing units 9Y, 9M and 9C, respectively.
One set of developing units of each of the image forming units 2C, 2M, and 2Y is operated by an instruction of a control circuit to be described later.
The structure is selectable such that the developing operation is performed by contacting the developing device or the developing operation is performed by separating from the developing device. As shown in FIG. 18, when the black developing unit 9B is separated from the photosensitive drum 6 in the image forming units 2C, 2M, and 2Y, color printing similar to that of the conventional apparatus can be performed.

First, the control circuit 70 determines whether the received data is a color image or a monochrome image. Hereinafter, a case where a color image is first received will be described.

When the control circuit 70 determines that the received data is a color image, the control circuit 70 drives the motor 89 via the motor drive circuit 81 so that each of the image forming sections 2Y, 2
The developing units 9Y, 9Y,
9M, 9C are brought into contact with the photosensitive drums 6Y, 6M, 6C, and the developing units 9B1,
9B2 and 9B3 are separated from the photosensitive drums 6Y, 6M and 6C. The developing unit 9B is a photosensitive drum 6
B is always in contact with it.

Next, the case where the data to be printed is only black will be described.

FIG. 19 is a diagram showing a state of the developing unit in the tandem type LED printer in the monochrome print mode according to the third embodiment. Developing units 9Y, 9
M, 9C are separated from the photosensitive drums 6Y, 6M, 6C, and the developing units 9B, 9B1, 9B2, 9B3
Are in contact with the photosensitive drums 6B, 6Y, 6M, and 6C, respectively.

When the control circuit 70 determines that the received data is a monochrome image, the control circuit 70 drives the motor 89 via the motor drive circuit 81 so that the developing unit for each of the image forming units is used for developing the monochrome toner. Unit 9B, 9B
1, 9B2, 9B3 are brought into contact with the photosensitive drum 6, and the developing units 9Y, 9M, 9C for color toner are provided.
From the photosensitive drum 6. In this state, the printing operation on the recording medium S transported to each image forming unit is performed.

The overall printing operation is the same as in the case of color printing, and therefore will not be described. However, the difference is that the paper feeding operation and the image forming operation are performed at a speed four times faster than the color printing. Further, similarly to the case of the first embodiment, a difference is that the print signal to each of the LED heads 3Y, 3M, 3C, 3B is divided and supplied for every four lines. That is, the print data of the monochrome image is stored in each of the LED heads 3Y, 3M, 3
C and 3B are supplied every four rows, and an exposure operation is performed on the photosensitive drum every four rows in the raster direction. This makes it possible to set the printing speed four times as in the first embodiment.

As described above, according to the apparatus of the third embodiment, the control circuit 70 is provided with the image discriminating means for judging whether the print instruction on the recording medium is a color image or a monochrome image. Of the plurality of developing units provided in each image forming unit, a developing unit for monochrome printing was selected and used, and the conveying speed of the recording medium and the operation speed of the image forming unit were set high, so that the color image The advantage is that printing of a monochrome image can be speeded up as compared to printing.

Further, as compared with the first embodiment, the operator does not need to manually replace the developing unit, and the printing speed of the monochrome image can be easily increased. Even in cases where color images and monochrome images are mixed,
The total printing time can be easily shortened.

Embodiment 4 The fourth embodiment is characterized in that, similarly to the color image printing apparatus of the third embodiment, two developing units are arranged in each image forming unit, whereby the same color is obtained. And simultaneously forming toner images having different densities to improve the image quality of a printed color image.

FIG. 20 is a diagram showing a configuration of a tandem-type LED printer according to Embodiment 4, FIG. 21 is a perspective view showing an arrangement structure of each light emitting element in an LED head, and FIG.
FIG. 2 is a block diagram showing a configuration of a driving circuit of the LED head.

Here, only the configuration and operation different from those of FIG. 18 described in the third embodiment will be described.

As shown in FIG. 20, each image forming unit 2B,
Two developing units 9B and 9B-1, 9Y and 9B-2, 9M and 9B-3, 9 are provided in 2Y, 2M, and 2C, respectively.
C and 9B-4 are arranged. The developing units 9B and 9B-1 of the image forming section 2B form black toner images that differ only in density from each other. The developing units 9Y and 9B-2 also form yellow toner images that differ only in density from each other. The developing units 9M and 9B-3 also form magenta toner images that differ only in density from each other. Further, the developing units 9C and 9B-4 also form cyan toner images different only in density from each other. Of these, the developing units 9B-1 to 9B-4 arranged on the upstream side in the rotational direction of the photosensitive drums 6B, 6Y, 6M, and 6C respectively have the developing units 9B, 9Y, and 9M arranged on the other downstream side. , 9
A toner lighter than C is stored.

The plurality of developing units are configured to be able to simultaneously contact the photosensitive drums 6B, 6Y, 6M, 6C, and to form the respective electrostatic latent images formed on the photosensitive drums 6B, 6Y, 6M, 6C. Can be developed simultaneously. Further, different developing biases are applied to these developing units, and the developing bias of the developing unit located on the upstream side in the rotation direction of the photosensitive drum is set to be lower in absolute value than that of the developing unit on the downstream side. Have been. That is, for example, in the image forming section 2B, the developing unit 9B-1 has a developing bias smaller in absolute value than the developing unit 9Y. These will be described later in detail.

The LED head 3 used for exposure is
As shown in FIG. 21, large and small light emitting elements LD and SD having different light emission amounts are close to each other in the sub-scanning direction, and 2560 light emitting elements are arranged in the scanning direction. These light emitting elements LD and SD are selectively controlled so that one of the light emitting elements is turned on in accordance with data input to each LED head 3. In the figure, 300D
4 shows a PI LED head. That is, 2560 element arrangement pitches of each light emitting element group were arranged such that the resolution of the LED head was 300 DPI, and light emitting elements having different light emission intensities in each light emitting element were arranged in a direction perpendicular to the sub-scanning direction. Things.

In the driving circuit of the LED head shown in FIG. 22, LSR1, SSR1,... Are shift registers, and a clock signal CLK corresponds to two rows of light emitting element groups.
Color data D1 and light color data D2 input in synchronization with
, And two sets of 2560-stage shift registers. .., LT1-1, LT1-2,... Are latch circuits for latching data in response to a latch signal LOAD, and two groups of latch circuits for latching dark color data D1 and light color data D2 respectively supplied to the respective light emitting element groups. Consists of G1-1, G1-2,... Are gate circuits that are controlled to open and close by a strobe signal STB. DR1-1, DR1-2,... Are light-emitting element drive drivers connected to a driver power supply VD, and each driver group includes two drivers.

LD1, SD1,... Are light emitting elements.
Each light emitting element group is constituted by two types of light emitting elements having different light emission intensities. Among them, the light emitting elements LD1, LD
Are elements having high emission intensity, and SD1, SD
Are elements having a small emission intensity. As shown in the figure, in the LED head having the above-described configuration, two sets of light emitting element groups can be driven with a common driver circuit.

Next, the operation of the color image printing apparatus having the above configuration will be described.

FIG. 23 is an explanatory diagram showing the image forming process in the image forming section, FIG. 24 is a diagram showing the bias of the developing unit and the developing direction, and FIG. 25 is a time chart showing the driving timing of the LED head.

In FIG. 23, reference numeral 3 denotes the LED shown in FIG.
The head 4 is a transfer roller, and 6 is a photosensitive drum. Around the photosensitive drum 6, a cleaning unit 15,
The image forming unit 2 including the charging roller 7 and the developing units 9A and 9B is disposed. The photoconductor drum 6 transfers an image line by line with the recording medium S sandwiched between the transfer roller 4. If the printing is performed at a print density of 300 DPI, the LED head 3 is used. Figure 2
As shown in FIG. 5A, the recording medium S is driven at the timing of a line synchronization signal LSYNC generated at intervals of 1/300 inch of conveyance, and irradiates the photosensitive drum 6.

As in the first embodiment, actual print data is supplied from the print control circuit 77 shown in FIG. 6 to the LED head 3, but as described with reference to FIG. Dark data D1
And light color data D2 are supplied as actual print data. As shown in FIGS. 25 (b) and 25 (c), when these data D1 and D2 are input to the LED head 3 together with the clock signal CL #, the shift register LSR , SSR. If the actual print data D1 (dark color) is "1", the 2-bit input signal in the shift registers LSR and SSR becomes a signal output of high emission intensity and the actual print data D2
If (light color) is "1", a signal output with low light emission intensity is obtained, and if "0", no signal is output.

Thereafter, the same operation is repeated 2560 times, and the shift registers LSR1, SSR1,.
560, the data is shifted to SSR2560. Next, the latch signal LOAD shown in FIG. 25D is input, and the data of all the shift registers are latched LT1-
1, LT1-2,... Thereafter, when the strobe signal STB is input, the light emitting elements LD1, S1
Only the selected element among D1,.
, G1-2,..., Drivers DR1-1, DR1
-2, ... are lit.

FIG. 25E shows the driving energy of the LED head. The driving energy amount is proportional to the driving time, and the driving energy amounts of the respective lines are set to be equal. Therefore, since the LED head is always driven with the same emission energy, it is necessary to express the shading of the image in dot units. However, in the fourth embodiment, the dark color data D1 is supplied for each dot position of each line. The light emission energy is changed to L or S shown in FIG. 25 (f) depending on whether the color data D2 is supplied or the light color data D2 is supplied.

As described above, in the LED head 3 in which light emitting elements having different light emitting intensities are arranged in combination at one dot position, each light emitting element is selectively caused to emit light.
The exposure intensity at each dot position can be changed according to the scanning direction position. Therefore, as shown in FIG. 24A, the same printing line on the photosensitive drum 6 has different potentials at different dot positions (-550 V at low exposure, and -350 V at high exposure).
V) to form a latent image.

The exposed photosensitive drum 6 rotates and is developed first by the developing unit 9A. When the photosensitive drum 6 further rotates, the same dot position moves to the next developing unit 9B. As shown in FIG.
Since different developing biases are applied to the developing units 9A and 9B, the toner image on the photosensitive drum 6 developed in each of the developing units 9A and 9B is either dark or light in accordance with the latent image potential. It is selectively developed as a toner image.

FIG. 24B shows the toner potential (−50 to −50).
100 V), the developing unit 9 using dark toner
A and the developing bias (-45) of the developing unit 9B for the light-color toner.
0 to -500 V). The toner potential of the developing unit 9A is changed to a normal toner potential (−350 to −400 V,
In order to make the potential smaller (in absolute value) than in FIG.
The developing bias of the dark color toner is set as low as -200V. Therefore, the photosensitive drum 6 receives a large amount of energy from the LED head 3 and can develop only a portion irradiated with a light emitting element having a large light emitting intensity (a portion having a large exposure), and is irradiated with a light emitting element having a small light emitting intensity. The exposed portion (small exposure portion) is not developed. Thus, the dark toner is attracted to the dot positions of the photosensitive drum 6 whose latent image voltage (absolute value) is low, and the dot positions whose latent image voltage is high are not developed.

Next, the photosensitive drum 6 rotates and reaches the developing unit 9B. The developing bias of the developing unit 9B is higher than that of the developing unit 9A (−400).
V), the dot position where the latent image voltage is high is developed by the developing unit 9B, that is, the light color toner is attracted by the surface electric field of the photosensitive drum 6 because
This is a dot position where the latent image voltage is high (irradiated with small energy by the LED, that is, irradiated by the light emitting element with low light emission intensity). Here, the latent image potential of the photosensitive drum portion already developed by the developing unit 9A is as low as -350V. However, at that position on the photosensitive drum 6, the potential has risen in the negative direction due to the presence of the already-developed dark color toner, and the developing unit 9B does not perform much development. As described above, the two developing devices 9A,
The dark and light toner developed on the photosensitive drum 6 sequentially at 9B rotates to a transfer position corresponding to the transfer roller 4 and is then transferred onto the recording medium S.

In the above, only the operation in one image forming unit 2 has been described, but the four image forming units 2B, 2
By performing the same operation in each of Y, 2M, and 2C, an image can be sequentially transferred onto a recording medium. Then, the developing units 9A and 9B of the image forming units 2B, 2Y, 2M and 2C are filled with toners having different densities, respectively. As a dark image,
An exposed portion having a small emission intensity can be printed as a faint image.

As described in detail above, according to the present invention, the light-emitting elements are exposed while changing the light-emitting energy for each light-emitting element group.
Since the toners having different densities are developed depending on the magnitude of the light emission intensity, high-quality gradation printing can be performed at the same speed as the conventional printing speed.

Further, since the dark and light images are selectively developed by switching the potential of the latent image on the photosensitive drum, the density can be reduced by passing the recording medium once through a photographic process in an electrophotographic printer. Printing of changed color images is possible.

In the above-described fourth embodiment, as an example, the printing using the dark and light toners of yellow, magenta, cyan, and black has been described. Color printing is also possible. In addition, printing with eight types of toner images having different densities on a recording medium is also possible. Furthermore, if the number of developing units mounted on each image forming unit is increased to two or more, multicolor printing can be performed.

[0140]

Since the present invention is configured as described above, it has the following effects.

According to the color image printing apparatus of the first aspect, the plurality of image forming units are arranged along the transport path of the recording medium, and the plurality of toner images are superimposed on the recording medium transported by the transport path. When printing a single color image, the transport speed is set higher than when printing a color image, so high-speed color printing is possible compared to other color electrophotographic printers. In addition, even when monochrome printing is performed, the printing speed is not inferior to the printing speed of other color electrophotographic printers. .

According to the color image printing apparatus of the second aspect, each image forming section is provided with a replaceable developing unit for forming a toner image. A developing unit for forming a toner image of the same color is attached to each of the units, and the conveying speed of the speed setting means can be set to four times that in forming a color image.

According to the color image printing apparatus of the third aspect, black print data is transferred to each LED head of the four image forming units, and only the printing of the odd lines is performed in the black image forming unit. By performing only the printing of the even-numbered lines by the subtractive color mixing operation in the remaining three color image forming units, monochrome printing can be performed at twice the printing speed as compared with color printing.

According to the color image printing apparatus of the fourth aspect, by arranging a plurality of developing units in each image forming section, it is possible to improve the printing speed and the print quality.

According to the color image printing apparatus of the fifth aspect, the operator does not need to manually replace the developing unit, and the printing speed of a monochrome image can be easily increased.

According to the color image printing apparatus of the sixth aspect, it is possible to simultaneously form toner images having the same color but different densities, thereby improving the image quality of the printed color image.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a tandem-type LED printer during color printing according to a first embodiment.

FIG. 2 is a block diagram illustrating a configuration of an image data processing circuit in the tandem type color printer.

FIG. 3 is a diagram illustrating a configuration of an exposure device of a printing mechanism and a developing device.

FIG. 4 is a diagram illustrating a developing process in a developing unit.

FIG. 5 is a block diagram showing a driving circuit of the LED head.

FIG. 6 is a block diagram illustrating a configuration of a printer control circuit.

FIG. 7 is a block diagram showing an image data processing circuit constituting a control unit on the printer side.

FIG. 8 is a block diagram showing an image data processing circuit constituting a control unit on the printer side.

FIG. 9 is a diagram illustrating transfer timing and storage timing of image data in the image data processing circuit.

FIG. 10 is a diagram showing a data transfer timing to each LED head.

FIG. 11 is a schematic diagram for explaining an example of a printing method on a recording medium.

FIG. 12 is a schematic diagram for explaining a printing method on printing paper in the color image printing apparatus according to the second embodiment.

FIG. 13 is a diagram showing a data transfer timing to each LED head.

FIG. 14 is a data transfer timing diagram showing the line scan period I1 of FIG. 13 in an enlarged manner.

FIG. 15 is a data transfer timing diagram showing the line scan period I2 of FIG. 13 in an enlarged manner.

FIG. 16 is a data transfer timing diagram showing the line scan period I3 of FIG. 13 in an enlarged manner.

FIG. 17 is a data transfer timing diagram showing the line scan period I4 of FIG. 13 in an enlarged manner.

FIG. 18 is a diagram illustrating a state of a developing unit in a tandem-type LED printer in a color print mode according to the third embodiment.

FIG. 19 is a diagram illustrating a state of a developing unit in a tandem-type LED printer in a monochrome print mode according to the third embodiment.

FIG. 20 is a diagram showing a configuration of a tandem-type LED printer according to a fourth embodiment.

FIG. 21 is a perspective view showing an arrangement structure of each light emitting element in the LED head.

FIG. 22 is a block diagram illustrating a configuration of a driving circuit of the LED head.

FIG. 23 is an explanatory diagram illustrating an image forming process in the image forming unit.

FIG. 24 is a diagram illustrating a bias of a developing unit and a developing direction.

FIG. 25 is a time chart showing the drive timing of the LED head.

[Explanation of symbols]

1 color image printing device, 2, 2B, 2Y, 2M, 2
C image forming unit, 3B, 3Y, 3M, 3C LED head, 4B, 4Y, 4M, 4C transfer roller, 6
６, 6Y, 6M, 6C Photoconductor drum, 7B, 7Y,
7M, 7C Charging roller (CΗ roller), 9B, 9
Y, 9M, 9C developing unit, 15B, 15Y, 1
5M, 15C cleaning unit, 20 conveyor belt, 30 drive roller, 31 driven roller, S
Recording medium, 33 cleaning blade, 34 waste toner tank, 40 paper storage cassette, 47 hopping mechanism, 51, 52 registration roller, 53
Media guide, 54 suction roller, 56 manual feed tray, 57, 62 guide, 58, 61 photo sensor, 60 static eliminator, 63 fixing device, 64 heat roller, 65 pressure roller, 66 cleaning pad, 67 discharge stacker, 70 control Circuit, 7
1 SP bias power supply, 72 DB bias power supply,
73 charging power supply, 75 adsorption charging power supply, 76 static elimination power supply, 77 print control circuit, 78 image memory,
79 interface circuit, 80 fuser control circuit,
81 motor drive circuit, 82 to 89 motor, 90
Sensor driver receiver.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H04N 1/46 H04N 1/46 C F term (Reference) 2H027 EA02 EA05 ED16 ED30 EE03 FA28 2H030 AA07 AB02 AD05 AD07 AD16 AD17 BB13 BB34 2H077 AD35 BA09 GA13 GA15 5C074 AA12 BB04 BB26 CC26 DD13 DD24 DD28 EE11 FF15 GG09 GG15 HH02 5C079 HA13 HB03 KA02 KA09 KA17 LA31 NA01 NA11 PA01 PA02 PA03

Claims (6)

[Claims] 1. A color image printing apparatus in which a plurality of image forming units are arranged along a conveyance path of a recording medium and a plurality of toner images are superimposed and printed on a recording medium conveyed by the conveyance path. An image determining unit that determines whether a print instruction to a medium is a color image or a monochrome image; a speed setting unit that switches and sets a conveyance speed of the recording medium according to the determination by the image determining unit; Data control means for supplying one or both of image data of different colors or image data of the same color to each of the image forming units in accordance with the judgment by the image discriminating means; A color image printing apparatus, wherein the setting means sets the transport speed to be higher when the print command is a monochromatic image than when the print command is a color image print command. 2. Each of the image forming sections is provided with a replaceable developing unit for forming a toner image. In the case of printing a single color image, each of the image forming sections has the same color toner. 2. The image forming apparatus according to claim 1, wherein a developing unit for forming an image is mounted, and a conveying speed of said speed setting means is set to be four times as high as that for forming a color image.
3. The color image printing device according to 1. 3. A developing unit for forming toner images of black (B), yellow (Y), magenta (M), and cyan (C) is provided in each of the image forming units. From the data control means, of the four image forming units, an image forming unit provided with a developing unit for forming a black (B) toner image is provided with image data of every other line. The remaining three lines of image data are supplied to the three image forming units, and the conveying speed of the speed setting means is set to 2 in the color image forming.
2. The color image printing apparatus according to claim 1, wherein the setting is doubled. 4. The color image printing apparatus according to claim 1, wherein a plurality of developing units are provided in each of the image forming units so as to operate simultaneously or selectively. 5. A developing unit for forming toner images of different colors and a developing unit for forming toner images of the same color are selectively provided in each of the image forming units. In printing a single-color image, the developing unit for forming a toner image of the same color is operated in any of the image forming units, and the conveyance speed in the speed setting unit is set to be four times that in forming a color image. The color image printing apparatus according to claim 4, wherein: 6. An image forming section, wherein each of the image forming sections is provided with an exposing means for exposing at a different light emission intensity in accordance with the density of image data from the data control means, and operates at different developing voltages and has the same color as each other. 5. The image forming apparatus according to claim 4, further comprising: two developing units for forming toner images having only different densities, wherein the developing units are simultaneously operated to form toner images having different densities on the recording medium. 3. The color image printing device according to 1.