JPH09134052A - Electrophotographic printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the variation of light emitting intensity among respective light emitting elements and to reduce a cost by turning on the light emitting element selected out of a pair of light emitting elements in accordance with bit data by each light emitting element group. SOLUTION: When a printing driving signal STB is inputted, light emitting element driving drivers DR1-1, DR1-2, and DR1-3, light emitting element driving drivers DR2-1, DR2-2, DR2-3,..., light emitting element driving drivers DR2560-1, DR2560-2 and DR2560-3 selectively drive and turn on the light emitting elements LD1, MD1 and SD1, the light emitting elements LD2, MD2, SD2,..., the light emitting elements LD2560, MD2560 and SD2560 by the output of gates G1-1, G1-2 and G1-3, the gates G2-1, G2-2, G2-3,..., the gates G2560-1, G2560-2 and G2560-3. Thus, the light emitting element selected by light emitting instructed value is turned on, so that the variation in each light emitting element group can be eliminated.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an electrophotographic printer.

[0002]

2. Description of the Related Art Conventionally, for example, in an electrophotographic printer, the surface of a charged photosensitive drum is irradiated with light to form an electrostatic latent image, and the electrostatic latent image is developed into a toner image. The toner image is transferred and fixed on a sheet. 2 is a block diagram of a printer control circuit in a conventional electrophotographic printer, and FIG. 3 is a time chart of the conventional electrophotographic printer.

In the figure, 11 is a microprocessor,
A print control unit including a ROM, a RAM input / output port, a timer, and the like. The print control unit 11 is arranged in the printer unit of the electrophotographic printer, and has a control signal SG1 and a video signal SG2 from a host controller (not shown). The entire printer unit is sequence-controlled by the above, and the printing operation is performed.

When the print control section 11 receives the print instruction by the control signal SG1, first, the fixer temperature sensor 20 detects whether or not the fixer 22 having the heater 22a is within a usable temperature range. If it is not within the above temperature range, the heater 22a is turned on to heat the fixing device 22 until it is within a usable temperature range. Next, the driver 12
The developing / transferring process motor (PM) 13 is driven through the same, and at the same time, the charge signal SG3 is supplied to the high voltage power source 2 for charging.
5, the high voltage power supply 25a for developing bias and the high voltage power supply 25b for toner supply bias are respectively sent and turned on. Then, the charging roller 27 is charged and the toner supply roller 2
A developing bias voltage is applied to 7b, and toner (not shown) is conveyed toward the developing roller 27a.

Further, the sheets set in a sheet cassette (not shown) are detected by the sheet remaining amount sensor 18 and the sheet size sensor 19, and sheet feeding matching the type of sheet is started. Here, the paper feed motor (PM) 15
Can be driven in both directions via the driver 14, and by driving in the opposite direction first, the paper
The paper is taken out from the paper cassette and is fed by the set amount until it is detected by the paper inlet sensor 16. Then, by driving the paper feed motor 15 in the forward direction, the paper is fed into the printing mechanism of the electrophotographic printer.

The print control section 11 sends a timing signal SG4 (line timing signal, line timing signal,
It includes raster timing signals and the like. ) To receive the video signal SG2. The video signal SG2 edited by the upper controller for each page and received by the print control unit 11 is L as the actual print data signal DATA.
It is sent to the ED head 21.

Then, when the print control section 11 receives the video signal SG2 for one line, the LED head 2
Latch signal LOAD is sent to 1, and the actual print data signal DA
TA is held in the LED head 21. In addition, the print control unit 11 sends the next video signal SG from the host controller.
Before receiving 2, the print drive signal ST is sent to the LED head 21.
Send B. As a result, the LED head 21 prints according to the held actual print data signal DATA. In addition,
CLK is the actual print data signal DATA for the LED head 21.
Is a clock signal for sending to. Further, the transmission / reception of the video signal SG2 is performed for each print line.

The LED head 21 irradiates a photosensitive drum (not shown) charged to a negative potential, and an electrostatic latent image is formed on the surface of the photosensitive drum by the dots having the increased potential. Then, the toner charged to a negative potential is attracted to each dot by an electrical attraction force, and a toner image is formed. Then, the toner image is sent to the transfer portion formed in the gap between the photoconductor drum and the transfer device 28. On the other hand, the print control unit 11 sends the transfer signal SG5 to the transfer high-voltage power supply 26 having a positive potential to turn it on. As a result, the transfer device 28 transfers the toner image onto the sheet passing through the transfer section.

Then, the sheet having the transferred toner image is sent in contact with the fixing device 22, and the toner image is transferred.
The heat of the fixing device 22 fixes the sheet. The paper sheet having the fixed toner is further sent and discharged from the printing mechanism of the electrophotographic printer to the outside of the electrophotographic printer through the paper discharge port sensor 17. Further, the print control unit 11 responds to the detection of the paper by the paper size sensor 19 and the paper inlet sensor 16, and outputs the transfer signal SG5 to the transfer high voltage power supply 26 and the charge signal SG3 to the drum charging high voltage power supply. 25, developing bias high-voltage power supply 25a, and toner supply bias high-voltage power supply 25b.
Therefore, the transfer high-voltage power supply 26 uses the paper transfer device 28.
A transfer voltage is applied to the transfer device 28 only while the transfer voltage passes. Then, when the printing is completed and the paper passes through the paper discharge port sensor 17, the drum charging high-voltage power supply 25 ends the application of the voltage to the charging roller 27, and the developing bias high-voltage power supply 25a applies the voltage to the developing roller 27a. Of the toner supply bias, the high voltage power supply 25b for toner supply bias ends the application of voltage to the toner supply roller 27b, and at the same time,
The transfer process motor 13 is stopped.

Thereafter, the above operation is repeated. Next, the LED
The head 21 will be described. FIG. 4 is a diagram showing a main part of a conventional LED head. As shown in the figure, the actual print data signal DATA is input to the LED head 21 together with the clock signal CLK. In this case, for example, the resolution is 30
In the 0 [DPI] electrophotographic printer, the actual print data signal DATA is composed of bit data of 2560 dots, and each bit data is a shift register SR1.
SR2, ..., SR2560 are sequentially shifted.

Next, the latch signal LOAD is input to the LED head 21, and the bit data is transferred to each latch LT1,
.., LT2560. Then, the bit data latched in each of the latches LT1, LT2, ..., LT2560 and the print drive signal STB are transferred to the gate G1,
, G2, ..., G2560, and the gates G1, G
2, ..., The output of G2560 is the switch element Tr1, Tr
2, ..., Tr 2560 is input.

Therefore, the switching elements Tr1, Tr2, ..., Corresponding to the high level bit data.
Tr2560 is turned on, and each light emitting element LD1, LD
2, ..., LD2560 is turned on. Note that r1,
r2, ..., R2560 are protection resistors, and VD is a power supply.
Next, the developing process will be described.

FIG. 5 is a structural diagram showing a developing process of a conventional electrophotographic printer, and FIG. 6 is a diagram showing a process voltage of the conventional electrophotographic printer. In FIG. 6, the horizontal axis indicates the position of the developing roller 27a, and the vertical axis indicates the photosensitive drum 29a.
The surface potential and the developing side potential of are taken. As shown in the figure, when the photoconductor drum 29 is rotated by driving the developing / transferring process motor 13 (FIG. 2),
The charging high-voltage power supply 25 applies a negative voltage to the charging roller 27, and causes the surface of the photosensitive drum 29 to have a constant voltage (about −).
700 [V]) to form a primary charging portion.

Next, when the LED head 21 irradiates light on the portion of the photosensitive drum 29 where printing is to be performed on the primary charging portion, the potential of the light-irradiated portion, that is, the exposed portion is lowered, and the potential is reduced to about -450. The electrostatic latent image is formed at about −550 [V]. On the other hand, in the developing device 30, the developing bias high voltage power supply 25a supplies the developing roller 27a with a developing bias voltage of -300 [V], and the toner supply bias high voltage power supply 25b supplies the toner supply roller 27b with -450 [V]. Are applied respectively. When these voltages are applied, the toner 31 in the developing device 30 is originally charged with a negative polarity, so that the toner 31 is supplied from the toner supply roller 27b toward the developing roller 27a. It is attached to the surface of 27a. By being charged, the toner 31 has a potential of about −100 to −150 [V]. Therefore, the potential of the toner 31 on the developing roller 27a, that is, the toner potential is -400 to.
It becomes −450 [V]. Further, as described above, the potential of the exposed portion on the photosensitive drum 29 is about -450 to -550.
[V], and the potential of the non-exposed portion where the electrostatic latent image is not formed remains -700 [V].

In the developing section where the developing roller 27a and the photosensitive drum 29 are in contact with each other, when the potential of the photosensitive drum 29 is higher than the toner potential by −200 [V] or more to the minus side, the developing roller 27a is above the developing roller 27a. Toner 31
Is not attracted to the photoconductor drum 29 and is not high, the toner 31 on the developing roller 27a is not
Attracted to 9.

Therefore, the potential of the exposure section is about -45.
0 to -550 [V], and the toner potential is about -400 to
Since it is −450 [V], there is no potential difference of −200 [V] or more between them. As a result, the toner 31 on the developing roller 27 a is attracted to the photosensitive drum 29, and a toner image is formed on the photosensitive drum 29. Further, the potential of the non-exposed portion is -700 [V], and the toner potential is about -4.
Since it is 00 to -450 [V], it is -200 between the two.
There is a potential difference of [V] or more. Therefore, the developing roller 2
The toner 31 on 7a is not attracted to the photosensitive drum 29, and a toner image is not formed on the photosensitive drum 29.

[0017]

However, in the above-mentioned conventional electrophotographic printer, all the light emitting elements LD1, LD2, ..., LD2560 of the LED head 21.
(FIG. 4) are turned on at the same time according to each print drive signal STB, the switch elements Tr1, Tr2 ,.
2560, light emitting elements LD1, LD2, ..., LD2560
If there are variations in the characteristics such as the above, the emission intensity of each dot also varies.

As a result, the size of each dot of the electrostatic latent image formed on the photosensitive drum 29 varies, and the size of each dot of the image actually printed also varies. And when printing images such as characters, even if there is a difference in the size of each dot, it can be almost ignored,
When printing an image such as a photograph, if there is a difference in the size of each dot, the print density varies, and the print quality deteriorates.

Therefore, the LED head 21 is composed of a plurality of LED drivers so that there is no difference in the size of each dot of the electrostatic latent image, and each light emitting element LD1, LD2,
The average value of the current required to drive the LD2560 is calculated for each LED driver, and the average value LE
The D driver is selected, and the LED head 21 is formed by using only the LED driver of the same level.

However, in this case, the variation in the light emission intensity among the LED drivers can be reduced, but the variation in the light emission intensity among the light emitting elements LD1, LD2, ..., LD2560 cannot be reduced. Moreover, in order to select the LED driver, it is necessary to find the average value of the current, which makes the work troublesome and increases the cost of the electrophotographic printer.

Also, a plurality of dots (for example, 4 × 4 = 1)
It is conceivable that the gradation is expressed by forming some dots from the plurality of dots, with 6 dots as one pixel. In this case, since the variation between dots is blurred in pixel units, it is possible to improve the printing quality to the extent that there is no practical problem. However, since one pixel is composed of a plurality of dots, the resolution of the LED head 21 becomes smaller than the original resolution (for example, if 16 dots are one pixel, the resolution is ¼). .), I can't make detailed expressions.

Further, in order to express gradation while maintaining resolution, the respective light emitting elements LD1 and LD of the LED head 21 are
2, ..., Method of changing the light emission time of LD 2560, or each light emitting element LD1, LD of LED head 21
2, ..., A method of changing the size of each dot forming the electrostatic latent image by fixing the light emission time of the LD 2560 and changing the number of times of light emission is provided. And the density of dots actually printed are unlikely to have a linear relationship. Therefore, the printing quality cannot be sufficiently improved.

The present invention provides an electrophotographic printer which solves the problems of the above-mentioned conventional electrophotographic printer, can reduce the variation of the light emission intensity among the light emitting elements, and can reduce the cost. The purpose is to do.

[0024]

Therefore, in the electrophotographic printer of the present invention, a set of light emitting elements having different emission intensities are provided, and a plurality of light emitting elements forming one dot by the one set of light emitting elements. Group, signal generating means for generating an actual print data signal consisting of a plurality of bit data for each light emitting element group, and the above-mentioned 1 for each light emitting element group.
And a light emitting element drive driver for lighting a light emitting element selected according to the bit data of the set of light emitting elements.

In another electrophotographic printer of the present invention, a photosensitive drum, an exposing means for forming an electrostatic latent image composed of a plurality of exposing portions having different potentials on the surface of the photosensitive drum, and each of the exposing means. A plurality of developing devices for converting the electrostatic latent image into a toner image by applying developing bias voltages having different voltages corresponding to the potentials of the parts.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 7 is a block diagram of a printer unit control circuit of the LED printer according to the first embodiment of the present invention, and FIG. 8 is a time chart of the LED printer according to the first embodiment of the present invention.

In the figure, 11 is a microprocessor,
A print control unit including a ROM, a RAM, an input / output port, a timer, and the like. The print control unit is provided in the printer unit of the electrophotographic printer, and the entire printer unit is controlled by a control signal SG1 and a video signal SG2 from a host controller (not shown). The sequence is controlled and the printing operation is performed. When the print control unit 11 receives a print instruction by the control signal SG1, first, the fixer temperature sensor 20 detects whether the fixer 22 having the heater 22a is in a usable temperature range, and the temperature range is determined. If not, the heater 22a is turned on, and the fixing device 22 is turned on until the temperature is within the usable range.
Heat.

Next, the developing / transferring process motor (PM) 13 is driven through the driver 12, and at the same time, the charge signal SG3 is supplied to the charging high voltage power source 25, the developing bias high voltage power source 25a and the toner supply bias high voltage power source 25b. To each of them and turn it on. Then, the charging roller 27 is charged, a developing bias voltage is applied to the toner supply roller 27b, and the toner (not shown) is conveyed toward the developing roller 27a.

Further, the sheets set in the sheet cassette (not shown) are detected by the sheet remaining amount sensor 18 and the sheet size sensor 19, and the sheet feeding matching the type of the sheet is started. Here, the paper feed motor (PM)
15 can be driven bidirectionally via the driver 14, and by first driving in the opposite direction, the paper is taken out from the paper cassette and the paper inlet sensor 1
The set amount is sent until 6 detects. continue,
By driving the paper feed motor 15 in the forward direction,
The paper is fed into the printing mechanism of the electrophotographic printer.

The print control section 11 sends a timing signal SG4 (including a line timing signal, a raster timing signal, etc.) to the host controller when the sheet reaches a printable position, and a video signal SG.
Receive 2. The video signal SG2 edited by the upper controller for each page and received by the print control unit 11 is an LED as an actual print data signal DATA.
It is sent to the head 35.

Then, when the print control section 11 receives the video signal SG2 for one line, it sends a latch signal LOAD to the LED head 35 as an exposing means, and sends an actual print data signal DATA into the LED head 35. Hold it. Further, the print control unit 11 sends the print drive signal STB to the LED head 35 before receiving the next video signal SG2 from the host controller. As a result, the LED head 3
5 prints according to the held actual print data signal DATA. CLK is a clock signal for sending the actual print data signal DATA to the LED head 35. Further, the transmission / reception of the video signal SG2 is performed for each print line.

The LED head 35 irradiates a photosensitive drum (not shown) that has been charged to a negative potential, and forms an electrostatic latent image on the surface of the photosensitive drum by the dots having the increased potential. Then, the toner charged to a negative potential is attracted to each dot by an electrical attraction force, and a toner image is formed. After that, the toner image is sent to a transfer portion formed in a gap between the photosensitive drum and the transfer device 28. On the other hand, the print controller 11 controls the transfer signal S
G5 is sent to the high voltage power supply 26 for transfer having a positive potential and turned on. As a result, the transfer device 28 transfers the toner image onto the sheet passing through the transfer section.

Then, the sheet having the transferred toner image is sent in contact with the fixing device 22, and the toner image is
The heat of the fixing device 22 fixes the sheet. The paper sheet having the fixed toner is further sent and discharged from the printing mechanism of the electrophotographic printer to the outside of the electrophotographic printer through the paper discharge port sensor 17. Further, the print control unit 11 responds to the detection of the paper by the paper size sensor 19 and the paper inlet sensor 16, and outputs the transfer signal SG5 to the transfer high voltage power supply 26 and the charge signal SG3 to the drum charging high voltage power supply. 25, developing bias high-voltage power supply 25a, and toner supply bias high-voltage power supply 25b.
Therefore, the transfer high-voltage power supply 26 uses the paper transfer device 28.
A transfer voltage is applied to the transfer device 28 only while the transfer voltage is passing. Then, the printing is completed, and the paper is ejected by the paper ejection sensor 1
After passing 7, the drum charging high-voltage power supply 25 finishes applying the voltage to the charging roller 27, and the developing bias high-voltage power supply 25a finishes applying the voltage to the developing roller 27a.
The high voltage power supply 25b for toner supply bias ends the application of the voltage to the toner supply roller 27b, and at the same time stops the motor 13 for the developing / transferring process.

Thereafter, the above operation is repeated. Next, the L
The ED head 35 will be described. FIG. 1 shows the first embodiment of the present invention.
It is a figure which shows the structure of the LED head in embodiment of this. In the figure, 35 is an LED head, and 36 is a counter. The counter 36 indicates the dot number of the actual print data signal DATA sent from the print controller 11 (FIG. 7) in synchronization with the clock signal CLK. Whether or not there is is counted by the number of clock signals CLK, and the count value is used as an address, and the nonvolatile memory 37 as a signal generating means.
Send to

Then, the gate 38 inverts the latch signal LOAD sent before the next actual print data signal DATA from the print control unit 11, and inputs it to the reset terminal of the counter 36 as a clear signal. When the clear signal is input to the counter 36, the output of the counter 36 is reset and counting can be performed again. By the way, the LED head 35 includes the light emitting elements LD1, LD2, ...
LD2560, MD1, MD2, ..., MD2560, S
, SD2560, D3, D3, SD3, ...
1, light emitting element LD2, MD2, SD2, ..., Light emitting element L
Each light emitting element group is configured by D2560, MD2560, and SD2560.

In this case, each light emitting element group includes light emitting elements LD1, LD2, ..., LD256 having a high light emission intensity.
0, light emitting elements MD1, MD2, ...
MD2560, and a light emitting element SD1 having a small emission intensity,
SD2, ..., SD2560. Then, when the input actual print data signal DATA is “1”, the corresponding light emitting element group is driven, and at that time, which one of the three light emitting elements is to be turned on is previously set for each light emitting element group. The determined light emission instruction value is stored in the non-volatile memory 37.

Therefore, in the manufacturing process of the LED head 35, a light emission test of the LED head 35 alone is performed, and the amount of emitted light is measured for each light emitting element group. Then, the variation correction data for making the light emission intensity uniform for each light emitting element group is obtained, and the variation correction data is written in the nonvolatile memory 37 as a light emission instruction value by a writing circuit (not shown).

It should be noted that LSR1, LSR2, ..., LSR2
560, MSR1, MSR2, ..., MSR2560, S
SR1, SSR2, ..., SSR2560 are shift registers, and three shift registers LSR1, MSR1, SSR1, shift registers LSR2, MSR2, SSR2 ,.
0s are combined.

Further, LT1-1, LT1-2, LT1-
3, ..., LT2560-1, LT2560-2, LT2
Numeral 560-3 is a latch, and three latches LT1-1, LT1-2, LT1 are provided corresponding to the respective light emitting element groups.
-3, latches LT2-1, LT2-2, LT2-3,
…, Latch LT2560-1, LT2560-2, LT
2560-3 are combined.

Then, G1-1, G1-2, G1-3,
..., G2560-1, G2560-2, G2560-3
Is a gate, and three gates G1-1, G1-2, G1-3, and gate G2 are provided corresponding to each light emitting element group.
-1, G2-2, G2-3, ..., Gate G2560-
1, G2560-2 and G2560-3 are combined.

Further, DR1-1, DR1-2, DR1
-3, ..., DR2560-1, DR2560-2, DR
Reference numeral 2560-3 is a light emitting element driving driver, and three light emitting element driving drivers DR1-1, DR1-2, DR1-3, light emitting element driving drivers DR2-1, DR2-2, corresponding to each light emitting element group, respectively. DR2-3, ..., Light emitting element drive drivers DR2560-1, DR2560-
2, DR2560-3 are combined.

Next, the operation of the LED head 35 having the above structure will be described. In this case, the actual print data signal DATA, the clock signal CLK, the latch signal LOAD, and the print drive signal STB from the print control unit 11 are received at the same timing as the conventional one. That is,
The counter 36 is reset by the latch signal LOAD sent before the actual print data signal DATA.

The actual print data signal DATA is input together with the clock signal CLK, the counter 36 counts the number of clock signals CLK, and when the count value is sent to the non-volatile memory 37 as an address, the light emission instruction value is read. Output of 3 bits, shift register LSR
1, MSR1, SSR1, shift register LSR2, M
SR2, SSR2, ..., Shift register LSR256
0, MSR2560, SSR2560, respectively.

Here, the 3-bit output is output when the actual print data signal DATA is "1", and is not output when it is "0". The value of each bit is set to "1" for the light emitting element to be turned on among the three light emitting elements of each light emitting element group. After that, by repeating this operation 2560 times, the shift register LSR2560, MSR2560, SSR25
The bit data of the actual print data signal DATA is shifted up to 60.

Next, the latch signal LOAD is input, and the shift registers LSR1, MSR1, SSR1, shift registers LSR2, MSR2, SSR2, ..., Shift registers LSR2560, MSR2560, SSR25.
The bit data in 60 is the latches LT1-1, LT1-
2, LT1-3, latches LT2-1, LT2-2, LT
2-3, latches LT2560-1, LT2560-
2, latched by LT2560-3.

Subsequently, when the print drive signal STB is input, the gates G1-1, G1-2, G1-3, and the gate G2.
-1, G2-2, G2-3, ..., Gate G2560-
1, G2560-2, G2560-3 outputs the light emitting element drive drivers DR1-1, DR1-2, DR1-
3, light emitting element drive drivers DR2-1, DR2-2, D
R2-3, ..., Light emitting element drive driver DR2560-
1, DR2560-2, DR2560-3 are light emitting elements LD1, MD1, SD1, light emitting elements LD2, MD2, S
D2, ..., Light emitting element LD2560, MD2560, SD
2560 is selectively driven to light. In addition, VD is a power supply and GND is earth.

As described above, by turning on the light emitting element selected by the light emission instruction value in each light emitting element group, it is possible to eliminate variations in each light emitting element group. Therefore, the size of each dot of the electrostatic latent image formed on the photosensitive drum (not shown) can be made equal, and the size of each dot of the image actually printed can also be made equal. As a result, even when printing an image such as a photograph, the print density does not vary, and the print quality can be improved.

FIG. 9 is a view showing the arrangement of the light emitting elements of the LED head according to the first embodiment of the present invention. As shown in the figure, each light emitting element group is arranged at a pitch corresponding to the resolution (300 [DPI]) of the LED head 35, and three light emitting elements LD1, MD1, SD in each light emitting element group are arranged.
1, light emitting element LD2, MD2, SD2, ..., Light emitting element L
D2560, MD2560, and SD2560 are arranged in a direction perpendicular to the arrangement direction of each light emitting element group.

In this case, three light emitting elements LD1 and MD
1, SD1, light emitting elements LD2, MD2, SD2, ..., Light emitting elements LD2560, MD2560, SD2560 are arranged in a direction at right angles to the arrangement direction of each light emitting element group, so that the sizes are changed from each other. Will be easier.
Therefore, the three light emitting element drive drivers DR1-1
(FIG. 1), DR1-2, DR1-3, light emitting element drive drivers DR2-1, DR2-2, DR2-3, ..., Light emitting element drivers DR2560-1, DR2560-2, DR
Even if the driving energies of 2560-3 are made equal, three light emitting element driving drivers DR1-1, DR1-2, DR1
-3, light emitting element drive drivers DR2-1, DR2-2,
DR2-3, ..., Light emitting element driver DR2560-1,
The emission intensity of DR2560-2 and DR2560-3 can be changed.

Next, a second embodiment of the present invention will be described. FIG. 10 is a diagram showing an arrangement of light emitting elements of the LED head according to the second embodiment of the present invention. As shown in the drawing, each light emitting element group is arranged at a pitch corresponding to the resolution (300 [DPI]) of the LED head 40, and three light emitting elements LD1, MD1, SD in each light emitting element group are arranged.
1, light emitting element LD2, MD2, SD2, ..., Light emitting element L
D2560, MD2560, and SD2560 are arranged in the same direction as the arrangement direction of each light emitting element group.

In this case, three light emitting elements LD1 and MD
1, SD1, light emitting elements LD2, MD2, SD2, ..., Light emitting elements LD2560, MD2560, SD2560 are arranged in the same direction as the arrangement direction of the respective light emitting element groups, so that it is difficult to change the sizes. Therefore, three light emitting elements LD1, MD1, SD1, a light emitting element LD2,
MD2, SD2, ..., Light emitting element LD2560, MD25
60 and SD2560 are equal in size, and three light emitting element drive drivers DR1-1, DR1-2, DR1-3,
Light emitting element drive drivers DR2-1, DR2-2, DR2
-3, ..., Light emitting element drivers DR2560-1, DR2
The emission intensity can be changed by making the driving energy of 560-2 and DR 2560-3 different.

Next, a third embodiment of the present invention will be described. 11 is a block diagram of a printer unit control circuit of an LED printer according to the third embodiment of the present invention, FIG. 12 is a block diagram of a data conversion circuit according to the third embodiment of the present invention, and FIG. It is a figure which shows the structure of the LED head in 3rd Embodiment. The first
The same reference numerals are given to the portions having the same structures as those in the embodiment, and the description thereof will be omitted.

As shown in the figure, the print controller 11 and the LED
Between the head 41 and the counter 36, the nonvolatile memory 3
7 and a data conversion circuit 42 as a signal generating means composed of a gate 38 are arranged, and when the real print data signal DATA is inputted to the non-volatile memory 37, 3-bit bit data DATA1 to DATA1 corresponding to the light emission instruction value is output. DATA
3 is generated and output to the LED head 41.

In this case, since the data conversion circuit 42 is not arranged in the LED head 41, the light emission instruction value stored in the non-volatile memory 37 in the data conversion circuit 42 can be rewritten by the actual print data signal DATA itself. it can. Therefore, when performing normal printing, as described above, the light emission instruction value is set so that the variation in the light emission intensity of each light emitting element group is reduced, and the light emission energy of each light emitting element group is changed to perform gradation printing. In the case of performing, the light emission instruction value for gradation can be set.

Therefore, the actual print data signal DATA itself input to the LED head 41 depends on which light emitting element LD
1, LD2, ..., LD2560, MD1, MD2 ,.
, MD2560, SD1, SD2, ..., SD2560 are indicated. In this way, since the light emission instruction value is set so that the variation in the light emission intensity of each light emitting element group becomes small, the size of each dot of the electrostatic latent image formed on the photosensitive drum (not shown) is made equal. The size of each dot of the image actually printed can be made equal. As a result, even when printing an image such as a photograph, the print density does not vary, and the print quality can be improved.

Further, since the light emission instruction value can be set on the printer side, one LED printer can perform printing with high printing quality and printing with gradation data. Next, a fourth embodiment of the present invention in which toners having different densities are mounted in the developing unit will be described.

FIG. 14 is a block diagram of a printer section control circuit of an LED printer according to the fourth embodiment of the present invention. In addition, about the part of the same structure as 1st Embodiment, the description is abbreviate | omitted by attaching | subjecting the same code | symbol. In this case, each toner image can be formed by three developing devices (not shown). Therefore, the developing rollers 27a ₁ and 27a of the respective colors are provided in the respective developing devices.
₂ , 27a ₃ are provided, and a high voltage power source 25 for developing bias
a.

FIG. 15 is a diagram showing the structure of an LED head according to the fourth embodiment of the present invention. In the figure, 3
5 is an LED head, 36 is a counter, and the counter 36 receives the clock signal CL from the print control unit 11 (FIG. 14).
Actual print data signal DATA sent in synchronization with K
The dot number is counted by the number of clock signals CLK, and the counted value is sent to the non-volatile memory 45 as a signal generating means.

When the real print data signal DATA as gradation data is input to the non-volatile memory 45, the light emission instruction value is read and the 3-bit output is output to the shift registers LSR1, MSR1, SSR1 and the shift register. It is sent to the registers LSR2, MSR2, SSR2, ..., Shift registers LSR2560, MSR2560, SSR2560, respectively.

Here, the 3-bit output has a large gradation value of the actual print data signal DATA, and the gradation value is a medium value for increasing the light emission intensity when the print density is increased. When the print density is set to a medium level, the light emission intensity is set to a medium value, the gradation value is set to be small, and when the print density is set to a low value, the light emission intensity is set to a small value. When it is 0 ", it is not output.

Therefore, gradation printing can be performed by changing the emission energy of each light emitting element group. FIG.
6 is a schematic view of an LED printer according to the fourth embodiment of the present invention, FIG. 17 is a process potential diagram according to the fourth embodiment of the present invention, and FIG. 18 is a developing direction according to the fourth embodiment of the present invention. FIG.

In FIG. 16, 27 is a charging roller and 27
a ₁ , 27a ₂ and 27a ₃ are developing rollers, 28 is a transfer device, 30a, 30b and 30c are developing devices, 35 is an LED head, and 46 is a cleaning device. As shown in FIG. 17, in the photosensitive drum 29, a potential of −700 [V] is applied to the primary charging portion charged by the charging roller 27, and a potential of -700 [V] is applied to the exposed portion (small exposure) irradiated with a small emission intensity. A potential of −550 [V] is applied to an exposed portion (during exposure) irradiated with a medium emission intensity, and a potential of −450 [V] is applied to an exposed portion (large exposure) irradiated with a high emission intensity. -35
A potential of 0 [V] is formed.

As described above, the electrostatic latent images formed by different potentials move to the portions facing the developing devices 30a to 30c as the photosensitive drum 29 rotates. Since different developing bias voltages are applied to the developing devices 30a to 30c, the developing devices 30a to 30c
The portion where development is performed by c differs depending on the potential of the electrostatic latent image on the photosensitive drum 29.

That is, the developing bias voltage applied in the developing device 30a is small (-200 [V]).
Therefore, the potential of the toner on the developing roller 27a ₁ becomes low. Therefore, the development is performed only on the exposed portion irradiated with the high emission intensity. Next, the photosensitive drum 29 is rotated and the electrostatic latent image reaches the developing device 30b. In the developing device 30b, the developing bias voltage is set higher (-300 [V]) than that of the developing device 30a. Therefore, the development is performed only on the exposed portion irradiated with the medium emission intensity. At this time, the potential of the portion developed by the developing device 30a is also low, but since the toner image is present on the photosensitive drum 29, the potential becomes higher toward the minus side.
Therefore, development by the developing device 30b is rarely performed.

Then, the photosensitive drum 29 is further rotated, and the electrostatic latent image reaches the developing device 30c. The developing device 3
At 0c, the developing bias voltage is set higher than that of the developing device 30b (-400 [V]). Therefore, the development is performed only on the exposed portion irradiated with the small emission intensity. At this time, the potential of the portions developed by the developing devices 30a and 30b is also low, but since the toner image is present on the photosensitive drum 29, the potential becomes higher toward the minus side. Therefore, the developing device 30c does not develop much.

In this way, the development by the developing devices 30a to 30c is sequentially performed, and the toner image reaches the transfer device 28 as the photosensitive drum 29 rotates, and is transferred onto the paper 47.
By the way, the developing devices 30a to 30c are filled with toner having different densities. Therefore,
Gradation printing expressing density can be performed. That is, the print density of the exposed area irradiated with the high emission intensity is high, and the print density of the exposed area irradiated with the low emission intensity is low.

As described above, since the light emission energy is changed for each light emitting element group and the exposure is performed, and the development is performed by using the toner having the different density according to the light emission intensity, the printing quality is high. Gradation printing can be performed. Here, FIG. 18 shows whether or not the development is possible when the development bias voltage and the emission intensity are changed, and the development is possible in the combinations marked with a circle.

Next, a fifth embodiment in which the developing devices 30a to 30c are unitized will be described. FIG. 19 is a block diagram of the process of the LED printer according to the fifth embodiment of the present invention. The same reference numerals are given to those having the same structure as in the fourth embodiment, and the description thereof will be omitted. In the figure, 30
a to 30c are developing units, and the developing units 30a to 30c,
An image drum cartridge 48 is constituted by the charging roller 27, the photosensitive drum 29, and the cleaning device 46, and can be attached to and detached from the main body of the electrophotographic printer as a unit. The photoconductor drum 2
Since the image drum 9 has a mechanical life, it is replaced as a consumable item together with the image drum cartridge 48.

Then, the image drum cartridge 4
When the remaining amount of the toner of each density filled in each of the developing devices 30a to 30c in 8 becomes small, the toner can be replenished. Next, the developing devices 30a to 30
A sixth embodiment in which c is filled with color toner to perform color printing will be described.

FIG. 20 is a block diagram of the process of the LED printer according to the sixth embodiment of the present invention, and FIG. 21 is a diagram showing the structure of the LED head according to the sixth embodiment of the present invention. The same reference numerals are given to those having the same structure as in the fourth embodiment, and the description thereof will be omitted. In the figure, 30Y, 30C,
Reference numeral 30M denotes a developing device filled with yellow (Y), cyan (C), and magenta (M) toners, respectively. The developing device 30Y, 30C, and 30M, the charging roller 27, the photosensitive drum 29, and the cleaning device 46 are used. The image drum cartridge 48 is configured so that it can be attached to and detached from the main body of the electrophotographic printer as a unit. Since the photosensitive drum 29 has a mechanical life, it is replaced as a consumable item together with the image drum cartridge 48.

Then, the image drum cartridge 4
When the remaining amount of the toner of each color filled in each of the developing devices 30Y, 30C, and 30M in No. 8 becomes small, the toner can be replenished. In this case, the LED head 75 irradiates the photoconductor drum 29 with light emission intensity different from each other to form an exposed portion having a different potential. And
Developing roller 27 of each developing device 30Y, 30C, 30M
The developing bias voltages applied to a ₁ , 27a ₂ and 27a ₃ are made different, and the toners of respective colors are attached to the exposed portions having different potentials.

Therefore, each color can be developed by rotating the photosensitive drum 29 once, so that the color printing process can be simplified. Next, the LED head 75 will be described. In this case, LE
The D head 75 is a print control unit 11 as a signal generating unit.
From FIG. 14, from the actual print data signal DATA, the clock signal CLK, the latch signal LOAD, and the print drive signal ST.
B is received at the same timing as in the conventional case, and color printing is performed.

The actual print data signal DATA includes yellow bit data DATAY and cyan bit data D.
It has a 3-bit structure consisting of ATAC and magenta bit data DATAM, and is L together with the clock signal CLK.
Input to the ED head 75, the shift register LSR1,
MSR1, SSR1, shift register LSR2, MSR
2, SSR2, ..., Shift register LSR2560, M
It is sent to SR2560 and SSR2560, respectively.

Then, the light emitting elements LD1, LD2, ..., LD2 having a high light emission intensity according to the bit data DATAY.
Reference numeral 560 denotes light-emitting elements MD1, MD2, ..., MD2560 having a medium emission intensity according to the bit data DATAC.
However, the light emitting elements SD1, SD2, ..., SD2560 having a small light emission intensity are turned on by the bit data DATAM.

FIG. 22 is a process potential diagram in the sixth embodiment of the present invention, and FIG. 23 is a diagram showing a developing direction in the sixth embodiment of the present invention. As shown in FIG. 22, in the photosensitive drum 29 (FIG. 20), the primary charging portion charged by the charging roller 27 has −700.
A potential of [V] is -550 [V] for an exposed portion (small exposure) irradiated with a low emission intensity, and -450 for an exposed portion (during exposure) irradiated with a medium emission intensity. [V]
A potential of −350 [V] is formed in each exposed portion (large exposure) irradiated with a high emission intensity.

As described above, the electrostatic latent images formed by the different potentials move to the portions facing the developing units 30Y, 30C and 30M as the photosensitive drum 29 rotates. Since different developing bias voltages are applied to the developing devices 30Y, 30C and 30M, the portions where development is performed by the developing devices 30Y, 30C and 30M are electrostatic latent images on the photosensitive drum 29. It depends on the potential.

That is, the developing bias voltage applied to the developing device 30Y is small (-200 [V]).
Therefore, the potential of the yellow toner on the developing roller 27a ₁ becomes low. Therefore, the development is performed only on the exposed portion irradiated with the high emission intensity. Next, the photosensitive drum 29
Is rotated, and the electrostatic latent image reaches the developing device 30C.
In the developing device 30C, the developing bias voltage is set higher than that of the developing device 30Y (-300 [V]). Therefore, the development is performed only on the exposed portion irradiated with the medium emission intensity. At this time, the potential of the portion developed by the developing device 30Y is also low, but since the yellow toner image exists on the photoconductor drum 29, the potential becomes higher toward the minus side. Therefore, development by the developing device 30C is rarely performed.

Then, the photosensitive drum 29 is further rotated, and the electrostatic latent image reaches the developing device 30M. The developing device 3
At 0M, the developing bias voltage is set higher than that of the developing device 30C (-400 [V]). Therefore, the development is performed only on the exposed portion irradiated with the small emission intensity. At this time, the potentials of the portions developed by the developing units 30Y and 30C are also low, but since the yellow and cyan toner images are present on the photoconductor drum 29, the potentials become higher toward the minus side. Therefore, the developing device 30M
Is not often developed.

In this way, the developing devices 30Y, 30C, 3
Development by 0M is sequentially performed, and the yellow, cyan, and magenta toner images reach the transfer device 28 and are transferred onto the paper 47 as the photosensitive drum 29 rotates. By the way, since the developing devices 30Y, 30C, and 30M are respectively filled with yellow, cyan, and magenta toners, color printing can be performed. That is, a yellow toner image is formed on the exposed portion irradiated with a large emission intensity,
A cyan toner image is formed on the exposed portion irradiated with medium emission intensity, and a magenta toner image is formed on the exposed portion irradiated with low emission intensity.

Here, FIG. 23 shows whether or not the development is possible when the development bias voltage and the light emission intensity are changed, and the development is possible in the combinations marked with a circle. It should be noted that the present invention is not limited to the above-described embodiment, but can be variously modified based on the gist of the present invention, and these are not excluded from the scope of the present invention.

[0081]

As described above in detail, according to the present invention, the electrophotographic printer is provided with one set of light emitting elements having different emission intensities, and one dot is formed by the one set of light emitting elements. A plurality of light emitting element groups, signal generating means for generating an actual print data signal composed of a plurality of bit data for each light emitting element group, and for each light emitting element group, the one of the one set of light emitting elements And a light emitting element drive driver for lighting a light emitting element selected according to bit data.

In this case, by turning on the light emitting element selected by the actual print data signal in each light emitting element group, it is possible to reduce variations in each light emitting element group. Therefore, the size of each dot of the electrostatic latent image formed on the photosensitive drum can be made equal, and the size of each dot of the image actually printed can also be made equal. As a result, even when an image such as a photograph is printed, the print density does not vary, and the print quality can be improved.

In another electrophotographic printer of the present invention, a photoconductor drum, an exposure unit for forming an electrostatic latent image formed on the surface of the photoconductor drum by a plurality of exposure units having different potentials, and each of the exposure units. A plurality of developing devices for converting the electrostatic latent image into a toner image by applying developing bias voltages having different voltages corresponding to the potentials of the parts. in this case,
The portion where development is performed by each developing device differs depending on the potential of the electrostatic latent image on the photosensitive drum.

Therefore, when the developing devices are filled with toners having different densities, it is possible to perform development using toners having different densities corresponding to the emission intensity, and it is possible to perform gradation printing.

[Brief description of the drawings]

FIG. 1 is a diagram showing a structure of an LED head according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a printer section control circuit in a conventional electrophotographic printer.

FIG. 3 is a time chart of a conventional electrophotographic printer.

FIG. 4 is a diagram showing a main part of a conventional LED head.

FIG. 5 is a structural diagram showing a developing process of a conventional electrophotographic printer.

FIG. 6 is a diagram showing a process voltage of a conventional electrophotographic printer.

FIG. 7 is a block diagram of a printer control circuit of the LED printer according to the first embodiment of the present invention.

FIG. 8 is a time chart of the LED printer according to the first embodiment of the present invention.

FIG. 9 is a diagram showing an arrangement of light emitting elements of the LED head according to the first embodiment of the present invention.

FIG. 10 is a diagram showing an arrangement of light emitting elements of an LED head according to a second embodiment of the present invention.

FIG. 11 is a block diagram of a printer unit control circuit of an LED printer according to a third embodiment of the present invention.

FIG. 12 is a block diagram of a data conversion circuit according to a third embodiment of the present invention.

FIG. 13 is a diagram showing a structure of an LED head according to a third embodiment of the present invention.

FIG. 14 is a block diagram of a printer control circuit of an LED printer according to a fourth embodiment of the present invention.

FIG. 15 is a diagram showing a structure of an LED head according to a fourth embodiment of the present invention.

FIG. 16 is a schematic diagram of an LED printer according to a fourth embodiment of the present invention.

FIG. 17 is a process potential diagram according to the fourth embodiment of the present invention.

FIG. 18 is a diagram showing a developing direction in the fourth embodiment of the invention.

FIG. 19 is a block diagram of a process of the LED printer according to the fifth embodiment of the present invention.

FIG. 20 is a block diagram of a process of the LED printer according to the sixth embodiment of the present invention.

FIG. 21 is a diagram showing a structure of an LED head according to a sixth embodiment of the present invention.

FIG. 22 is a process potential diagram according to the sixth embodiment of the present invention.

FIG. 23 is a diagram showing a developing direction in the sixth embodiment of the invention.

[Explanation of symbols]

11 Print Control Unit 29 Photoreceptor Drums 30a, 30b, 30c, 30Y, 30C, 30M
Developing device 35, 41, 75 LED head 37, 45 Non-volatile memory 42 Data conversion circuit DATA Actual print data signal LD1, LD2, ..., LD2560, MD1, MD2,
..., MD2560, SD1, SD2, ..., SD2560
Light emitting elements DR1-1, DR1-2, DR1-3, DR2-1, D
R2-2, DR2-3, ..., DR1-260, DR1
-2560, DR1-260 Light emitting element driver

Claims (4)

[Claims] 1. A plurality of light emitting element groups each comprising: (a) a set of light emitting elements having different light emission intensities, and one set of light emitting elements to form one dot; and (b) each of the light emitting element groups. Signal generating means for generating an actual print data signal composed of a plurality of bit data, and (c) each light emitting element group,
An electrophotographic printer, comprising: a light emitting element drive driver for lighting a light emitting element selected according to the bit data of the one set of light emitting elements. 2. An exposure means for forming an electrostatic latent image on a surface of the photoconductor drum, comprising: (a) a photoconductor drum; and (b) a plurality of exposure parts having different potentials, and (c) each of the exposures. An electrophotographic printer, comprising: a plurality of developing devices that convert the electrostatic latent image into a toner image by applying a developing bias voltage having a different voltage corresponding to the potential of each part. 3. A plurality of light emitting element groups each comprising (a) a set of light emitting elements having different light emission intensities and forming one dot by the one set of light emitting elements, and (b) each light emitting element group. Signal generating means for generating an actual print data signal composed of a plurality of bit data, and (c) each light emitting element group,
The electrophotographic printer according to claim 2, further comprising: a light emitting element driving driver that turns on a light emitting element selected according to the bit data of the one set of light emitting elements. 4. The electrophotographic printer according to claim 2, wherein each developing device is filled with toner of each color.