JPS61234163A - Character printing control system for led printer - Google Patents

Abstract

PURPOSE:To print out at high speed in the case of a small printing width by respectively individually connecting extension lines to common side electrodes of respective chips, scanning only chip groups corresponding to the printing width and enlarging a rotating speed of a photosensitive body in inverse proportion to the printing width. CONSTITUTION:When a pulse voltage is impressed to extension lines COM1-COM4 in a time sharing, and only chips 21-24 are scanned, a scanning time T' once may be T' (<a fixed scanning time T). Accordingly, when forming one line by a minimum printing width, a high speed printing out can be performed. When one scanning time is shortened, line intervals of respective latent images I1-I4 formed on a photosensitive drum 7 become smaller than a prescribed line interval L. A control section 10 outputs a speed control signal to a motor drive circuit 14 in order to drive a stepping motor at high speed. Accordingly, since the rotating speed of the photosensitive drum 7 is increased in inverse proportion to the printing width, on the photosensitive drum 7, the latent images I1-I4 are successively formed at the prescribed line interval L.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a printing control method in an LED printer using an electrophotographic method.

(Technical Background of the Invention) FIG. 6 shows an optical writing head in a conventional LED printer of this type. That is, this optical writing head comprises an LED array 1, which includes a plurality of chips 2. ~2
It is formed by arranging n and 2', to 2'n in a line. The LEDs 2a of these chips 2I to 2n and 2'12'n are connected to a drive circuit 3, respectively, by signal lines DO to DI27 wired in a matrix. These drive circuits 3 are connected to the signal line D
O to D Become. On the other hand, each of the above chips 2I~
The common side electrodes of 2n and 2'1 to 2'n each have leader lines COM and ~COM wired in a matrix.
n are connected to each other. These leader lines COMI
~COM n is scanned by the decoder.

In the optical write head having such a structure, the shift register 6 of each drive circuit 3 receives data serially transmitted from the host computer using a clock input. The latch circuit 5 receives a latch signal from the shift register 6 when the shift register 6 takes in the data.
The data within is latched, and the drive unit 4 is driven based on the latched data by inputting a timing signal. Since the drive unit 4 is composed of, for example, a transistor array, the latch circuit 5 drives only predetermined transistors and supplies a signal current corresponding to data to the signal line D o "D rzr. On the other hand, the lead line COM, ~COM n
is scanned by the decoder 8, and as shown in FIG. 7, COM+, C0M2 ---
A voltage with a constant pulse width is applied in the order of COMn(7).

Therefore, each LED 2a of each chip 21 to 2n is connected to the chip 2. .

The LEDs 2a of each chip, 2'j to 2'n, emit light in the order of 2z, 23----2n, and the LEDs 2a of each chip, 2'j to 2'n, emit light in the order of chips 2'+, 2'2.2'z ---2' Since the light is emitted in the order of n, as shown in FIG.
It is formed corresponding to I~2n and 2'+~2'n.

(Problems in the Background Art) Conventionally, all chips 2. ~2n and 2/I~2'n were scanned. ! II. As shown in FIG. 7, the leader line COM
+ to COM n in a time division manner, and chip 2. By scanning ~2n, 2', ~2'n with a constant scanning time T, one line of latent image processing, ~In and i
/, ~I'n were formed on the photosensitive drum 7. However, if all the chips are fixedly scanned in this way, it will always take time T for one scan even if the width to be printed for - lines is small. It takes exactly the same amount of time as printing with the largest printing width.

(Object of the Invention) An object of the present invention is to provide a print control system for an LED printer that can print out at high speed when the print width is small.

(Summary of the Invention) The present invention independently connects lead lines to the common side electrode of each chip forming an LED array, connects each lead line to a scanning circuit, and connects each lead line to a scanning circuit. If the printing width is small, the scanning circuit is controlled to scan only the number of chip groups corresponding to the printing width, and the rotational speed of the photoreceptor is adjusted to obtain a predetermined line spacing. is characterized by increasing in inverse proportion to the print width.

(Embodiments of the Invention) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a block diagram of an LED printer according to the present invention, which includes a control section 10 connected to a host computer 9. As shown in FIG. This control section 10 is composed of a microcomputer, and print data is sent from the host computer 9. An LED array drive circuit 11 is connected to the control section 10, and print data is serially transmitted to this drive circuit 11. In addition, the control unit 10 also has an L
An ED array scanning circuit 12 is connected, and this scanning circuit 12
The common code is input to . An LED array 1 is connected to the LED drive circuit 11 and the scanning circuit 12, and these constitute an optical writing head 13, which will be described later. A motor drive circuit 14 and a charging high-voltage power supply 15 are further connected to the control unit 10 . The motor drive circuit 14 drives and controls a stepping motor (not shown) using a speed control signal from the control section 10, thereby controlling the rotational speed of the photosensitive drum 7 (see FIG. 4). The voltage applied to the charging high-voltage power supply 15 is controlled by a control signal from the control unit 10, whereby the photosensitive drum 7 is uniformly charged and photosensitive. A RAM 16 is connected to the host computer 9.
6 stores print format data including print width data from the host computer 9. And this RAMl6
The printing width data and the like are taken in by the control section 10. A detector 17 for detecting the paper size of a cassette loaded with transfer paper is connected to the control unit 10.
Paper size data is input from 7.

The optical writing head 13 includes an LED array 1, as shown in FIG.
It is formed by arranging monolithic chips 21 to 2n including D2a in a line. Each chip 2. The common side electrodes of ~2n are electrically insulated, and each common side electrode has a lead wire COM +~COM
n are independently connected. A scanning circuit 12 consisting of a decoder is connected to these drawers [cOM+ to COMn. Each LED 2a of each chip 21 to 2n is connected to an LED array drive circuit 11 via signal lines DO to D1 wired in a matrix.
is connected. This drive circuit 11 is a signal line DO”
A drive unit 4 directly connected to the Dray, a latch circuit 5 connected in parallel to this drive unit 4,
The latch circuit 5 is further comprised of a shift register 6 connected in parallel. shift register 6
Print data is serially transmitted from the control unit IO. The latch circuit 5 is formed of 128 flip-flops corresponding to the number of LEDZa of one chip, and latches the print data of the shift register 6. The drive unit 4 is formed from a transistor array, each transistor being connected to the output side of each flip-flop forming the latch circuit 5.

Next, a print control method according to the present invention will be explained together with circuit operation.

First, the host computer outputs print format data including maximum print width data, and this data is stored in the RAM 16. The control unit IO stores this print format data in RAM.
Since the paper size data is input from the paper size detector 17, the control unit IO determines the chip to be scanned based on the paper size data, maximum print width data, etc., and scans the paper (not shown). ) and the print width correspond to each other, and a common code corresponding to each chip is output to the scanning circuit 12. In this case, since it is the maximum print width data, each common code corresponding to the chips 21 to 2n is sequentially output to the scanning circuit 12.

On the other hand, since one line of print data necessary for the maximum print width is sent from the host computer to the control unit 10, this print data is serially transmitted to the shift register 6 of the LED array drive circuit 11 for each LED chip. When print data is transmitted for each LED chip, a latch signal is output to the latch circuit 5 each time, so each flip-flop forming the latch circuit 5 latches the print data for each LED chip. A timing signal is input to the latch circuit 5 when the print data is latched, and each transistor of the drive unit 4 is driven by this signal input. This operation is repeated for each LED chip, so the scanning circuit 1
2 decodes the common code □Code the leader line COM
As shown in FIG. 7, a pulse voltage is applied to each chip 2. When ~2n is scanned in this order, an inclined latent image pattern ~In as shown in FIG. 8 is formed on the photosensitive drum 7. Therefore, one line of characters is printed on the transfer paper at the maximum print width.

Next, the host computer outputs print format data including minimum print width data, and this data is stored in RAMI 6.
, the control unit IO reads the print format data including the minimum print width data.

Then, the control unit 10 determines the chips to be scanned based on the paper size data and minimum print width data from the paper size detector 17, and outputs only the common code corresponding to each chip. In other words, a group of chips necessary for minimum print width data, etc. to form one line.

For example, when corresponding to chip groups 21 to 24, four common codes indicating only these chips are sent to the scanning circuit 12.
Output to. Therefore, the scanning circuit 12 decodes only these common codes and sequentially applies pulse voltages to the lead lines COMI to C0M4 in a time-divisional manner as shown in FIG. scan. Further, when one line of print data necessary for the minimum print width is sent from the host computer to the control unit 10, and this print data is outputted to the drive circuit 3 for each chip 21 to 24, on the photosensitive drum 7, As shown in Figure 4, latent image work! ~I
Only 4 is formed.

By the way, as shown in FIG. 3, the leader lines C0M1 to CO
A pulse voltage is time-divisionally applied to chip 2.M. ~2
When scanning only 4, the scanning time of − times is T'(<
T) is sufficient. Therefore, when forming one line with the minimum print width, it is possible to print out at high speed. However, when the -times scanning time becomes shorter, since the photosensitive drum 7 is rotating at a speed corresponding to scanning all of the chips 2 to 2n, as shown in FIG. The line spacing of each formed latent image pattern ~IL (see broken line) is smaller than the predetermined line spacing.

Therefore, in one method of the present invention, the motor drive circuit 14 is controlled by the control section 10. That is, as described above, when the printing format data including the minimum printing width data and the cassette size data are input, the control unit 10 outputs a speed control signal to the motor drive circuit 14 to drive the staying motor at high speed. do. Therefore, the rotational speed of the photosensitive drum 7 in the direction of the arrow shown in FIG. Formed sequentially.

In the above embodiment, printing format data including printing width data,
Although the printing width of one line is detected by both the paper size data from the paper size detector 17, for example, as shown in FIG. The printing width may be detected.

(Effects of the Invention) According to the present invention, the lead wires are independently connected to the common side electrode of each chip forming the LED array,
Each leader line is connected to a scanning circuit, the width of one line to be printed on the transfer paper is detected, the scanning circuit is controlled to scan only the chip group corresponding to the printing width, and the rotational speed of the photosensitive drum is controlled. By increasing the width in inverse proportion to the print width, it is possible to print out documents at high speed in the case of a document with a small print width of -line.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an LED printer according to the present invention, FIG. 2 is a circuit diagram of an optical writing head according to the present invention,
Fig. 3 is a timing chart of the pulse voltage applied to the leader line when the printing width is small, Fig. 4 is a diagram showing the latent image state when the printing width is small, and Fig. 5 is another embodiment of the present invention. FIG. 6 is a circuit diagram of a conventional optical writing head. Figure s7 is a timing chart of the pulse voltage applied to the leader line when all the chips are scanned, and Figure 8 is a diagram showing the state of the latent image formed when all the chips are scanned. L----1----LED array, 21~2n--1---chip. 2,', ~2' n---tt, 3.11---
---1 drive circuit, 7-------photosensitive drum, 10-------1 control section, 12-----m-scanning circuit, COM+ to C0Mn- leader line. Figure 3 Figure 4 Figure 7 Figure 8

Claims (1)

[Claims] 1. An LED array in which chips including a plurality of LEDs are arranged in a line, a drive circuit that drives the LED array based on print data, and a common of each of the chips. An LED printer comprising an optical writing head comprising a scanning circuit connected to a side electrode and energizing a chip to be driven by the print data, and forming a latent image on a photoreceptor that moves the LED array in a perpendicular direction. In this step, a lead wire is independently connected to the common side electrode of each chip, and each lead wire is connected to the scanning circuit,
Detecting the width of one line to be printed on the transfer paper, controlling the scanning circuit to scan only the number of chip groups corresponding to the printing width, and making the moving speed of the photoreceptor inversely proportional to the printing width. A printing control method for an LED printer, which is characterized in that it is controlled by controlling the LED printer. 2. The print control method for an LED printer according to claim 1, wherein the print width is detected from the print data. 3. The print control method for an LED printer according to claim 1, wherein the print width is detected from the size of paper.