JPH05212902A - Image forming device - Google Patents

Abstract

PURPOSE:To reduce a variation between blocks to eliminate a deterioration of an image quality by a method wherein image forming elements and drive circuits are divided into a plurality of blocks, and a circuit generating a strobe signal per block is provided. CONSTITUTION:Shift registers SR1-SR40 of 64 bits serially transmit printing data from a printer body. Latch circuits L1-L40 of 64 bits series-parallel convert the printing data serially transmitted from the shift registers SR1 SR40. A strobe signal generation circuit 6 generates 40 strobe signals per line. Namely, LED arrays 4, constant-current circuit arrays B1-B40, AND circuit arrays A1-A40, the latch circuits L1-L40, and the shift registers SRI-SR40 are divided into blocks per array or circuit. One line is divided into 40 blocks, and the blocks are driven on 40 strobe signals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a static type image forming apparatus, and more particularly to reduction of power source capacity and prevention of a step in a printing line.

[0002]

2. Description of the Related Art In a static type image forming apparatus, a large number of image forming elements are arranged on a substrate and a dedicated drive circuit is assigned to each image forming element. FIG. 4 shows the basic configuration of a static LED print head. In the figure, 01 is a control circuit, SR1 to SR40 are shift registers, L1 to L40 are latch circuits, A1 to A40 are AND circuit arrays, B1 to B40 are constant current circuit arrays, 4
Is an LED array.

FIG. 5 shows operation waveforms of the static type image forming apparatus. When the data for one line is sent from the printer main body, this is latched in the latch circuits L1 to L40, and the AND circuit arrays A1 to A40 are sent by the strobe signal.
To drive the LED array 4 to emit light all at once. In such an image forming apparatus, the load on the power source is large and a large-capacity power source is required, which increases the circuit cost. For example, in an A4 300 DPI (dot / inch) image forming apparatus, the emission current of each LED is set to 5 mA, and the constant current circuit array B1 is used.
When B40 is driven by 5V, the maximum power consumption reaches 64W. Here, the LED print head is taken as an example to show the problems of the conventional example, but other image forming apparatuses such as a thermal head also have the problem of large power consumption due to simultaneous operation of many image forming elements.

To reduce the power source capacity, Japanese Patent Laid-Open No. 63-647
Japanese Patent Laid-Open No. 75 proposes to drive a static image forming apparatus in four divisions by providing four strobe terminals. However, one pitch in the sub-scanning direction is 84.
When the width is 6 μm and this is divided into four, a step of 21 μm occurs at the strobe signal switching portion. If there is a step of 10 μm or more, the image quality is significantly deteriorated.
One strobe signal is further divided into 128 in the sub-scanning direction, and four strobe signals are set to 1 for printing one line.
It is proposed to generate 28 times alternately. In this way, the step is eliminated, but since the printing of one dot is divided into 128 times in the sub-scanning direction for printing, the dots spread in the sub-scanning direction and the resolution is reduced. Also set the strobe signal to 1
Dividing into 28 × 4 512 times complicates signal processing.

One of the causes of performing such complicated processing in Japanese Patent Laid-Open No. 63-64775 is that a strobe signal is generated on the printer main body side. The connection is complicated and the number of strobe signals cannot be increased.

[0006]

An object of the present invention is to (1) reduce the power supply capacity of an image forming apparatus and simplify the power supply circuit, (2)
Eliminating the step in the print line, and (3) Generating a strobe signal in the image forming apparatus to simplify signal transmission with the printer body and reduce the resolution in the sub-scanning direction as described above. To prevent.

[0007]

The image forming apparatus of the present invention is a static type image forming apparatus in which a large number of image forming elements are arranged on a substrate and a drive circuit is provided for each image forming element. And a drive circuit are divided into a plurality of blocks, a clock signal is counted, a strobe signal generation circuit for generating a strobe signal is provided for each block, and an image forming element and a drive circuit are provided for each block. It is characterized by making it operate.

As the image forming apparatus, L shown in the embodiment is used.
The same applies to a thermal head, a liquid crystal shutter array print head, an EL print head, a plasma print head, etc., in addition to the ED print head.

[0009]

According to the present invention, the strobe signal is generated in the image forming apparatus. For this purpose, a clock signal may be counted by a counter and a block may be switched every time a clock for one block is input to generate a strobe signal.

[0010]

FIG. 1 shows the configuration of the embodiment, and FIG. 2 shows its operation waveform. In FIG. 1, reference numeral 2 denotes a control circuit, which receives a clock signal from the printer body and generates a latch signal each time data for one line is prepared. Each of SR1 to SR40 is a 64-bit shift register that serially transfers print data from the printer body. 64 for L1 to L40
Bit latch circuit, shift registers SR1 to SR4
The print data serially transferred at 0 is converted to serial-parallel.
A1 to A40 are AND circuit arrays each including 64 AND circuits. B1 to B40 are constant current circuit arrays each consisting of 64 constant current circuits, and 4 is an LED array. Here, 40 LED arrays 4 in which 64 LEDs are integrated are provided. The image forming apparatus has a resolution of 30
For 0DPI A4 printer. In addition to this, the embodiment is provided with a power supply circuit 7 for supplying the power supply voltage VDD to the constant current circuit arrays B1 to B40 and the like.

A strobe signal generating circuit 6 generates 40 strobe signals (strobe 1 to strobe 40) per line. That is, the LED array 4, constant current circuit arrays B1 to B40, AND circuit arrays A1 to A40,
Latch circuits L1 to L40, shift registers SR1 to SR
40 is a block for each array or circuit, and one line is divided into 4
It is divided into 0 and driven by 40 strobe signals.

The strobe signal generating circuit 6 has, for example, 2
64-bit counter 8 for counting the MHz clock signal and a preset bit at the beginning
A shift register 10 having 0 bits is provided.

FIG. 2 shows the operation of the embodiment. Control circuit 2
Applies a latch signal to the latch circuits L1 to L40 each time a clock for one line (2560 dots) is input.
The print data input in synchronization with the clock is stored in the shift registers SR1 to SR40 and is transferred to the latch circuits L1 to L40 by a latch signal. In addition, the shift register SR
A clock signal from the printer main body is used as the shift clocks in 1 to SR40.

In the strobe signal generating circuit 6, data is set in the preset bit DPB of the shift register 10 by resetting the image forming apparatus, and every time the counter 8 counts 64 clock signals, the data is shifted by 1 bit by 1 bit. Shift within 10. The data of the last bit is circulated to the first bit (the bit next to the preset bit DPB) of the shift register 10 by the signal of the next counter 8. Then, the data of the shift register 10 is used as a strobe signal, and 40 strobe signals are extracted.

In this way, the strobe signals are each 6
It is generated by being divided into 40 strobe signals corresponding to 4 clocks, the AND circuit arrays A1 to A40 are driven one array at a time, and the LED array 4 also operates at a width of 64 clocks one array at a time. Calculate in terms of power consumption. The constant current circuit arrays B1 to B40 are driven by 5 V, and LE
When each LED of the D array 4 is driven by 5 mA, the constant current circuit arrays B1 to B40 are driven one by one, so that the maximum power consumption is 1.6 W (5 mA × 5 V × 64).
Of 1/40 of the conventional example. Therefore, the capacity of the power supply circuit 7 may be much smaller than that of the conventional example, and it is possible to prevent the power supply circuit 7 from increasing in size.

Next, considering the step difference, the pitch in the sub-scanning direction is 84.6 μm at a resolution of 300 DPI. Since this is divided into 40, the step difference between blocks is 2.
The image quality is 1 μm, and the image quality is not deteriorated even in the case of graphic data in which a step is prominent. According to the experience of the inventor, a step of 20 μm causes a problem of deterioration of image quality particularly in graphic data, and for example, a jagged line due to the step becomes conspicuous on a straight line in the horizontal direction. To make the step inconspicuous with the naked eye,
It is necessary to keep the step difference to about 10 μm or less.
An image forming apparatus having a resolution of 4 and a resolution of 300 DPI can be obtained by dividing the strobe signal into at least eight or more.
If the pitch of one line in the sub-scanning direction is 84.6 μm and this is divided into eight, the step difference caused by the switching of strobe signals will be about 10 μm. Also, in the A4 240 DPI printer, the line pitch in the sub-scanning direction is 106 μm.
If this is divided into 8 parts, the difference in level will not be noticeable.
The step is 25 μm. In order to eliminate the influence of the step and reduce the power supply capacity, the strobe signal is preferably divided into 10 or more, more preferably 20 or more.

The strobe signal generating circuit 6 of FIG. 1 can be modified in various ways, and for example, the strobe signal generating circuit 12 of FIG. 3 may be used. In this strobe signal generation circuit 12,
A 40-base counter 14 is provided after the 64-base counter 8, and the signal of the 40-base counter 14 is decoded by the decoder 16 to generate 40 strobe signals.

Although the LED print head has been described as an example in the embodiment, a thermal head can be obtained by changing the LED to a heating element, and an EL head can be obtained by changing the LED to an EL element.

[0019]

According to the present invention, since the static type image forming apparatus is time-division driven by the strobe signal,
The maximum power consumption is reduced and the power supply circuit is simplified. Further, since the strobe signal is divided into a plurality of steps, the step difference between blocks due to the switching of the strobe signal is made small, and the image quality is not deteriorated by the step. Further, since a large number of strobe signals are generated in the image forming apparatus, the signal transmission with the printer body is simplified.

[Brief description of drawings]

FIG. 1 is a block diagram of an image forming apparatus according to an embodiment.

FIG. 2 is an operation waveform diagram of the embodiment.

FIG. 3 is a block diagram of a main part of an image forming apparatus according to a modified example.

FIG. 4 is a block diagram of a conventional image forming apparatus.

FIG. 5 is an operation waveform diagram of a conventional image forming apparatus.

[Explanation of symbols]

 2 control circuit 4 LED array 6 strobe signal generation circuit 7 power supply circuit 8 counter 10 shift register 12 strobe signal generation circuit 14 40-ary counter 16 decoder A1 to A40 AND circuit array B1 to B40 constant current circuit array L1 to L40 latch circuit SR1 SR40 shift register

Claims (1)

[Claims] 1. A static image forming apparatus in which a large number of image forming elements are arranged on a substrate and a driving circuit is provided for each image forming element, wherein a plurality of the image forming elements and the driving circuits are provided. In addition to dividing into blocks, a clock signal is counted, a strobe signal generation circuit for generating a strobe signal is provided for each block, and the image forming element and the drive circuit are operated for each block. An image forming apparatus characterized.