JP2009143094A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent an erroneous detection of print data on a print head side caused by cross-talk noises from occurring, to prevent an erroneous control on controlling the temperature of a print head from occurring, and to prevent the print head from coming out of order. <P>SOLUTION: Whether the same nozzle is driven at a plurality of times or not is judged, and when it is judged that the same nozzle is driven, it is avoided that a nozzle driving signal is transmitted to the print head. A substrate near the print head is equipped with a circuit for performing this processing. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus and a control method thereof, and more particularly, to an image forming apparatus including a print head that performs printing in an ink jet system and a control method thereof.

A device that performs printing while moving the print head 1 to the left and right with respect to the recording medium 2 such as an ink jet printer is usually connected between the main control board 3 and the print head 1 by a flexible cable 4. Print control is performed by sending a control signal from 3 to the print head 1. In the ink jet printer, in order to control a large number of nozzles on the print head 1, a large number of control signals are transmitted through the flexible cable 4, and the control signal is transmitted from the main control board 3 to the print head 1 in the above configuration. In particular, as the flexible cable 4 connecting the main control board 3 and the print head 1 becomes longer, the control signal passing through the flexible cable 4 is likely to generate crosstalk noise and waveform distortion. As a result, the control signal is not correctly transmitted to the print head 1, which may cause malfunction of the print head 1 or failure of the print head 1 (FIG. 1). In the conventional invention, as disclosed in Patent Document 1, for the purpose of solving the above-described problem, a nozzle drive signal (heat pulse signal) 5 for driving a plurality of nozzles provided in the print head 1 is printed. The rise and fall timings of the clock signal 6 for transferring the control signal for controlling the head 1 to the print head 1 and the rise and fall timings of the nozzle drive signal (heat pulse) 5 do not overlap. By adjusting the rising and falling signals of the clock signal 6 and transferring the print head control signal, crosstalk noise that may occur at the rising and falling timings of the clock signal 6 is prevented and the print head 1 is controlled. Some control signals are provided with means for preventing erroneous sampling in the print head 1.
JP 2000-025228 A

  The method disclosed in Patent Document 1 transfers a control signal for controlling the print head 1 to the print head 1 for the heat pulse signal 5 for driving a plurality of nozzles provided in the print head 1. By adjusting the rising and falling signals of the clock signal 6 and transferring the print head control signal so that the rising and falling timings of the clock signal 6 and the rising and falling timings of the heat pulse 5 do not overlap. Crosstalk noise in the clock signal 6 that may occur at the rise and fall timings of the clock signal 6 is prevented, and a control signal for controlling the print head 1 is prevented from being erroneously sampled in the print head 1. This prevents malfunction of the print head 1 (FIG. 2).

  However, in the method disclosed in Patent Document 1, the rising and falling timings of the clock 6 and the rising and falling timings of the heat pulse 5 are not overlapped, so that the rising and falling timings of the clock 6 are not overlapped. This is a method for preventing crosstalk noise and preventing erroneous sampling of data at the print head 1, and is caused by transferring the heat pulse signal 5 from the main control board 3 to the print head 1 via the flexible cable 4. It is a problem. If the generation of the heat pulse 5 is performed beside the print head 1, the problem that occurs in Patent Document 1 does not occur. Further, the heat pulse signal 5 may be used as means for raising the temperature of the print head 1 by driving the heat pulse 7 on the pulse so as not to eject ink from the nozzle as shown in FIG. For such a nozzle drive signal (short pulse) 7, the clock 6 is generated by the method disclosed in Patent Document 1 so as not to overlap the rising / falling timing of the clock signal 6 and the rising / falling timing of the heat pulse 5. When the clock transfer speed is high, there is a possibility that the specification of the input timing of the print head 1 cannot be satisfied, and the temperature on the print head 1 is detected on the main control board 3 via the flexible cable 4. Therefore, when the print head temperature is erroneously detected due to crosstalk noise, the correct heat pulse signal 5 is There may not be transferred to the printheads 1. Further, if the heat pulse 5 having an appropriate length is not transferred to the print head 1 due to erroneous detection of the head temperature, the life of the print head 1 may be shortened or may be broken.

  Accordingly, an object of the present invention is to reduce crosstalk noise and waveform distortion that occur when a large number of signals are transmitted to a print head via a flexible cable, and to prevent a malfunction and failure of the print head.

  The present invention for solving the above-described problems is an image forming apparatus for recording on a recording medium using a print head having a plurality of nozzles, wherein the nozzle driving signal generates a driving signal for the plurality of nozzles. Generating means; print data transferring means for transferring print data to the print head; clock generating means for generating a clock signal for transferring print data to the print head; and determining the print data to be transferred to the print head. Print data determining means, extraction means for extracting the nozzle drive order for the print data transferred to the print head, and nozzles for determining whether the same nozzle is driven a plurality of times by extraction by the extraction means The same nozzle is driven by the drive order determination means and the nozzle drive order determination means. Determining whether or not to transfer the nozzle drive signal to the print head when it is determined that the nozzle drive order extracting means, the nozzle drive order determining means, and the enable / disable determining means are disposed on a substrate in the vicinity of the print head. It is characterized by having.

  With the above configuration, the number of signal lines transmitted on the flexible cable 4 between the main control board 3 and the print head 1 can be reduced, so that crosstalk noise can be reduced. Further, the temperature adjustment control of the print head 1 on the print head 1 is possible. Therefore, when detecting the print head temperature on the main control board via the flexible cable 4 and controlling the head temperature, it is possible to prevent erroneous detection of the temperature caused by the crosstalk noise. It is possible to prevent a print image from being distorted due to an erroneous sample of print data of the print head 1 caused by crosstalk noise or waveform distortion, and a print head failure due to the erroneous sample.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected to the already demonstrated part and duplication description is abbreviate | omitted.

  As shown in FIGS. 4 and 5, the inkjet image forming apparatus includes an external device 10 composed of an image scanner, a personal computer, a CAD device, etc., a main control board 3, and a print head 1. The print head 1 includes a plurality of nozzles. The outline of the operation of the ink jet image forming apparatus having such a configuration is as follows.

  In the inkjet image forming apparatus, the main control board 3 detects inputs from the CPU 11, the head control unit 12, the ROM 13 that stores programs executed by the CPU 11 and print patterns, the image memory 14 that temporarily stores image data, and various sensors 15. An I / O port 16, a carriage control unit 17 for driving the print head 1 in the main scanning line direction, and a conveyance control unit 18 for conveying the recording medium 2 are configured. The CPU 11 controls the interface with the external device 10 that transfers image data, and controls the entire main control board including the memory and I / O. The image data is transferred from the external device 10. In response to a command from the CPU 11, the head controller 12 performs various image processing and transfers image data to the print head 1. The carriage controller 17 uses the encoder sensor 19 to read main scanning line position information read from the linear scale 20. By using this, the carriage motor 21 is driven, the print head 1 is brought to a predetermined position on the main scanning line of the recording medium 2, and ink is ejected from the print head 1. Further, the transport control unit 18 uses the sub-scanning encoder sensor 22 and uses the sub-scanning line position information read from the transport linear scale 23 attached to the paper feed shaft, so that the transport motor 24 is controlled. By driving, the recording medium 2 is moved to a predetermined position on the sub-scanning line (conveying direction), thereby ejecting ink from the print head 1 at a predetermined position on the recording medium 2 to form a desired image.

  Further, as shown in FIG. 6, the conventional inkjet image forming apparatus receives a print data confirmation signal (LT) 25, a print data transfer clock (CLK) 6, a print data (DATA) 9, and a nozzle drive signal from the main control board 3. (Heat pulse) 5 is transferred to the print head 1 via the carriage substrate 26, and the print data 9 is erroneously transferred due to crosstalk noise and the temperature from the print head 1 is erroneously detected as the number of ink colors and nozzles increases. As a result, the head failure was a problem.

  The first embodiment of the present invention will be described below. FIG. 7 is a diagram showing a first embodiment of the present invention. Print data is generated by the head controller 12 on the main control board 3, and the print data 9 is transferred for each ink to the nozzle drive controller 27 on the carriage board 26 in the vicinity of the print head at the timing shown in FIG. Of the DATA signal 9 in FIG. 8, data 0 to data 15 are signals that determine which data nozzle group on the print head 1 (FIG. 9) is driven, and BLK 0 to BLK 5 indicate which nozzle in the data nozzle group. It is a signal that determines whether to drive. For example, when driving the nozzle of the block 40 of the data 0 drive nozzle group of FIG. 9, the data 0 drive nozzle group is selected by the data 0-15, and the block 40 is designated to be driven by BLK0-5. Further, by asserting the heat pulse signal 5, the nozzles of the block 40 of the data 0 drive nozzle group can be driven. In addition, the print head according to the present embodiment cannot simultaneously discharge all nozzles, and the maximum number of nozzles that can be driven at one time is 16. This is because even if the print head of the present embodiment is set to drive all the drive nozzle groups with data 0-15, one of the 40 blocks of nozzles in the drive nozzle group with BLK0-5. This is because only nozzles can be specified. As the number of nozzles that are driven simultaneously increases, the current value for driving increases, and as the amount of current increases, a power supply with that much capacity is required, which is not realistic. The print head is used by limiting the number of simultaneous drives. When all the nozzles are driven in the present embodiment, all the nozzles are driven by transferring data 40 times as in the print head drive timing 28 shown in FIG. 9, and printing using all the nozzles is performed on the recording medium 2. Can be done. Further, printing on the recording medium can be performed by scanning the head in the scanning direction (direction different from the conveyance direction of the recording medium 2) with respect to the recording medium 2 while repeating the data transfer 40 times.

  Further, as shown in FIG. 7, the print data signal 9 transferred from the main control board 3 to the print head 1 has a waveform disturbance due to crosstalk noise as shown in FIG. The print data signal 9 and the waveform distortion due to reflection of the print data signal 9 due to mismatch between the port impedance and the print head side input impedance, and the capacitance component between the main control board 3 -flexible cable 4 -carriage board 26 -print head 1 Since the rising and falling edges of the clock signal 6 are lost, the print data signal 9 may be erroneously sampled on the print head side. If the print data signal 9 is erroneously sampled, the selection of the drive nozzle group and the selection of the drive nozzle block in the drive nozzle group in FIG. 2 will not be able to print. Further, when the nozzles in the print head are used continuously for a short time, in the case of the print head 1 that blows ink by heating the heater like a thermal head, the heater resistance for blowing ink from the nozzles May break, causing a head failure. This is because if the drive nozzle block in the drive nozzle group is continuously driven due to an erroneous sample of the print data signal 9, the nozzle block that has been continuously driven by the print head 1 may break down. That is. The first embodiment of the present invention aims to prevent this head failure.

  The nozzle drive order extracting means 29 in FIG. 7 is for DATA0 which is print data for ink 0, DATA1 which is print data for ink1, DATA2 which is print data for ink2, DATA3 which is print data for ink3, and for ink4 BLK0-5 data for determining the drive nozzle block in the drive nozzle group is extracted for DATA4 which is the print data and DATA5 which is the print data for the ink 5, and the extracted result is stored in the nozzle drive order extraction means 29. Save to memory as needed. The BLK0-5 data stored in the memory in the nozzle drive order extraction unit 29 is read by the nozzle drive order determination unit 30 as needed. A nozzle drive block is extracted (S101), and the block driven last time is compared with the block driven this time (S102). It is determined whether the same drive nozzle block is continuously driven (S103). When the same drive block is not continuously driven, a heat pulse (HE) 5 is generated by the heat pulse generation availability determination means 31 and a heat pulse signal (HE) 5 is output to the print head 1 ( S104). The nozzle drive control unit 27 prints the print data confirmation signal (LT) 25, the CLK signal 6, and the print data signal 9 from the clock, latch, and data output circuit 32 in accordance with the timing of outputting the heat pulse signal (HE) 5. By outputting to the head 1, the nozzles in the print head are driven. When it is determined by the nozzle drive order determination means 30 that the same nozzle has been continuously driven, the heat pulse (HE) 5 is not output by the heat pulse generation availability determination means 31 (S105). This prevents nozzles from being driven in the print head and prevents head failure (FIG. 10).

  Next, a second embodiment of the present invention will be described. FIG. 11 is a diagram showing a second embodiment. The nozzle drive order extracting means 29 in FIG. 11 is for DATA0 which is print data for ink 0, DATA1 which is print data for ink1, DATA2 which is print data for ink2, DATA3 which is print data for ink3, and for ink4. BLK0-5 data for determining the drive nozzle block in the drive nozzle group of FIG. 12 is extracted for DATA4 which is the print data and DATA5 which is the print data for ink 5, and the extracted result is the nozzle drive order extraction means. The data is stored in the memory 29 at any time. Further, in the nozzle drive order storage means 33, the nozzle drive order storage means 33 is written in advance with the nozzle drive order storage means 33 via the nozzle drive order writing means 34 from the head controller 12 (FIG. 12). The nozzle drive order determination means 30 reads the value of BLK0-5 from the memory in the nozzle drive order extraction means 29 at any time, and compares whether the nozzles are driven in the order of 33 written in the nozzle drive order storage means (S132). Is determined (S133). When the nozzles are driven in the order written in the nozzle drive order storage means 33, a heat pulse (HE) is generated by the heat pulse generation availability determination means 31, and a heat pulse signal (HE) is sent to the print head 1. Is output (S134). The nozzle drive control unit 27 outputs the LT signal, the CLK signal, and the DATA signal from the clock, latch, and data output circuit 32 to the print head 1 in accordance with the timing of outputting the heat pulse signal (HE). Drive the nozzle inside. When it is determined by the nozzle drive order determination means 30 that the nozzles are not driven in the order written in the nozzle drive order storage means 33, the heat pulse generation availability determination means 31 does not output a heat pulse (HE). By doing so, the nozzle in the print head 1 is not driven (S135). The flow shown in FIG.

  Next, a third embodiment of the present invention will be described. FIG. 14 is a diagram showing a third embodiment of the present invention. In the present embodiment, a short pulse generator 35 for controlling the temperature of the print head 1 is generated on the carriage substrate 26 side. The short pulse generator 35 outputs a nozzle drive (short pulse) signal 36 that does not eject ink as shown in FIG. 15 to the print head 1. By giving a nozzle drive (short pulse) signal 36 that does not discharge ink as shown in FIG. 15, the print head 1 is heated by heating the heater resistance in the nozzle without discharging ink from the nozzle of the print head 1. It is generally known that it can be heated. Further, the temperature of the print head 1 is acquired on the carriage substrate 26 from the temperature sensor 37 in the print head 1 and stored in the print head temperature control unit 38 based on the acquired temperature. The temperature of the print head 1 is controlled by the print head temperature control unit 38 of the nozzle drive control unit 27 so that the temperature of the print head 1 is adjusted to the target print head temperature. Control to temperature. The conventional method has a heat pulse generation unit 39, a short pulse generation unit 35, and a print head temperature control unit 38 on the main control board 3. The heat pulse or the short pulse is sent from the main control board 3 to the flexible cable 4. 1, crosstalk noise as shown in FIG. 1 occurs, and the printhead 1 erroneously samples the print data transferred to the printhead due to the crosstalk noise. In some cases, the image is garbled and a print head failure occurs due to an erroneous sample. In the case where a heat pulse (HE) is output on a short pulse for the purpose of heating the print head 1 as in the present embodiment, crosstalk noise becomes particularly prominent, and an erroneous sample of print data is likely to occur. Although crosstalk noise is also generated in this embodiment, the heat pulse signal (HE) is transmitted between the main control board 3 and the carriage board 26 by bringing the generation of the heat pulse signal (HE) to the carriage board 26 side. Therefore, crosstalk noise caused by the rise and fall of the heat pulse can be eliminated. As a result, when the rise and fall of the heat pulse and the rise and fall of the clock signal 6 which are problems in Patent Document 1 overlap, crosstalk noise occurs at the rise and fall of the clock signal 6, thereby causing the print head. 1 can solve the problem that the print data 9 is erroneously sampled.

The figure explaining the background of this invention and crosstalk noise. The figure which showed the method currently disclosed by patent document 1. FIG. The figure which showed the subject with respect to the method currently disclosed by patent document 1. FIG. The block diagram of the inkjet image forming apparatus in this invention. 1 is a block diagram of an inkjet image forming apparatus according to the present invention. The figure which showed the structure of the inkjet image forming apparatus until now. The figure which showed the 1st Embodiment of this invention. The figure which showed the data transfer timing to a print head. The figure which showed the structure and drive method of a print head. The figure which showed the heat pulse drive availability determination method in the 1st Embodiment of this invention. The figure which showed the 2nd Embodiment of this invention. The figure which showed the writing method of the drive order of the nozzle in the 2nd Embodiment of this invention. The figure which showed the heat pulse drive availability determination method in the 2nd Embodiment of this invention. The figure which showed the 3rd Embodiment of this invention. The figure which showed the shape of the heat pulse for heating the print head in embodiment of this invention subject 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Print head 2 Recording medium 3 Main control board 4 Flexible cable 5 Nozzle drive signal (heat pulse)
6 Clock signal 7 Nozzle drive signal (short pulse)
9 Print data 10 External device 11 CPU
12 Head controller 13 ROM
DESCRIPTION OF SYMBOLS 14 Image memory 15 Various sensors 16 I / O port 17 Carriage control part 18 Conveyance control part 19 Linear scale 20 Encoder sensor 21 Carriage motor 22 Subscanning encoder sensor 23 Subscanning linear scale 24 Carrying motor 25 Print data decision signal 26 Carriage substrate 27 Nozzle drive controller 28 Print head drive timing 29 Nozzle drive order extraction means 30 Nozzle drive order determination means 31 Heat pulse generation availability determination means 32 Latch, clock, data output means 33 Nozzle drive order storage means 34 Nozzle drive order storage means 34 Means 35 Short pulse generation means 36 Heat pulse (short pulse)
37 Temperature sensor 38 Print head temperature control unit 39 Heat pulse generating means

Claims (1)

An image forming apparatus for recording on a recording medium using a print head having a plurality of nozzles,
Nozzle drive signal generating means for generating a drive signal for the plurality of nozzles;
Print data transfer means for transferring print data to the print head;
Clock generation means for generating a clock signal for transferring print data to the print head;
Print data determining means for determining print data to be transferred to the print head;
Extraction means for extracting the nozzle drive order for the print data transferred to the print head;
Nozzle drive order determination means for determining whether the same nozzle is driven a plurality of times by extraction by the extraction means;
A determination unit for determining whether or not to transfer a nozzle drive signal to the print head when it is determined by the nozzle drive order determination unit that the same nozzle is driven,
An image forming apparatus comprising: a nozzle driving order extracting unit; a nozzle driving sequence determining unit; and the availability determining unit on a substrate in the vicinity of the print head.

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