JPS6233647A - Color ink jet printer - Google Patents

Abstract

PURPOSE:To adjust the positions of the dot recording of ink of each color simply with high precision by giving data afforded to charging means for respective nozzles while being displaced by the correction sections of positional displacement. CONSTITUTION:Image data inputted from an image source 1 are written to a buffer memory 4 for a control circuit 3 through a picture interface 2. The contents of the buffer memory 4 given from a memory 20 are arranged in order of yellow, magenta, black and cyan, and nozzles are each displaced by one address section. Even when the nozzles are not displaced by one address section, data are inputted similarly by displacing addresses. The displacement of the nozzles in the memory 4 can easily be set by a recording-position setter 14, thus enabling clear printing free of variation in the positions of dot recording.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an inkjet type color inkjet printer.

(Prior Art) In continuous injection type inkjet recording, ink is ejected from a nozzle having a minute opening, becomes particles due to surface tension, travels straight, and records dots on a recording paper wound around a rotating drum. When not recording, a square wave charging voltage is applied to the ink to charge the ink particles.
Charged ink particles are bent under a deflection electric field oriented perpendicular to the ejection axis and directed away from the recording paper. A charging voltage is applied in response to an image signal, and recording is performed using only uncharged particles.

For inkjet color printers, yellow (
Color recording is performed by ejecting inks of three colors (Y), magenta (CM), and cyan (C), or four colors including black (BK) from separate nozzles.

The positions of each nozzle are set so that the dot recording positions on the recording paper are at the same position or on the same line for all colors.

FIG. 7 shows the configuration of a continuous jet Hertzian color inkjet printer. Here, the paper feed/discharge mechanism, drum drive system, and nozzle head drive motor are omitted. The Hertzian method uses extremely small nozzles to modulate and control ink droplets in units of several dozen. Image data input from a host computer or an image source 1 is taken into a buffer memory 4 of a control circuit 3 via an image interface 2. The control circuit 3 applies data in the buffer memory 4 to the charged electrode of the nozzle head 10 through a print line buffer 5 and a correction circuit 6, which will be described later. The control circuit 3 also controls four colors (Y, M) via an ink pump controller 7.

The ink pump 8 that pressurizes the ink (C, BK) is controlled, and the ink is ejected from four nozzles (not shown) of the nozzle head 10. The position of the nozzle is adjusted so that the dot recording positions on the recording paper 9 are on the same line for all colors. A charging voltage is applied to the charging electrode of the nozzle head 1O in response to an image signal (ON-OFF signal) from the print line buffer 5, and an image is recorded on the recording paper 9 on the recording drum 13. Nozzle head I
O is attached to a head feed stand 11, and is moved in the axial direction of the recording drum I3 by a head feed screw 12, so that the recording drum 13 rotates at high speed.

(Problems to be Solved by the Invention) Normally, in monochrome or monochrome inkjet printers, it is only necessary to consider the appropriate flow rate of one color (the amount of ink deposited on the recording paper). On the other hand, in a color printer, the nozzles of four colors are usually arranged in parallel, and the four colors of ink cannot be sent to the same point at the same time. Therefore,
Image data for the same recording position is sequentially output for each ink at different times. Therefore, each color (yellow,
It is necessary to make adjustments so that the recording positions of magenta, cyan, and black (magenta, cyan, and black) overlap. This adjustment typically consists of mechanical and temporal alignment elements. The accuracy of this recording position is important for improving radiation quality.

Mechanical alignment can be solved by precise alignment of nozzle placement. That is, it is sufficient to adjust the left and right and up and down adjustment screws for each color nozzle.

Regarding temporal alignment, the following points need to be considered.

1. Ink ejected from the tip of an inkjet nozzle must travel a certain distance at a finite speed.

For example, the on-demand type is 2 to 5 m/s, and the Hertzian type is 40 to 50 m/s. Therefore, in order to overlap each color at the same point, it is necessary to eject ink at different timings.

3. There are variations in the nozzle. This variation is due to nozzle inner diameter pressure loss, etc. For this reason, the jet speed differs from nozzle to nozzle.

That is, the flight time and ejection timing differ from nozzle to nozzle, and it is necessary to correct this. That is, a time correction circuit is provided in the middle of the signal system to keep the dot recording position on the recording paper constant.

Here, FIG. 9 shows the contents of the memory of the conventional print line buffer 5. Assuming that addresses are shown in the horizontal direction and color signal data is shown in 4 bits in the vertical direction, the first address contains the data of the first four color recording dots (
IY, IM, IC, IB), and n data sets are stored in that order. In the case of reading, each data set is written to the data buffer of the print line buffer 5 from the control circuit 3, and further, this data set is read out in the order of addresses by a read clock linked to the rotation of the recording drum 13, and the data set is written to the data buffer of the print line buffer 5. After a delay of 18 to 18 for each color, it is sent to the nozzle head 10.

A color printer requires nozzles for four colors, for example, and since the positions of the nozzles vary as described above, a time correction circuit 6 as shown in FIG. 7 is necessary.

(If the positional force of each nozzle is adjusted so that the dot recording positions of all colors are on the same position on the recording paper °9, a time correction circuit 6 is also required.) This type It is conceivable to provide delay circuits 15, 16, 17, and 18 for each color nozzle as the correction circuit 6 as shown in Fig. 8.In this case, the delay circuit may include a frequency oscillator and several hundred stages of serial type. Consists of a shift register,
By changing the oscillation frequency, the time during which the jet ON-OFF signal stays in the shift register is changed, thereby making it possible to independently adjust the time for each color. However, this kind of delay circuit! 5 to I8, when attempting to adjust the position and individual differences of each nozzle, it is necessary to further adjust the oscillation frequency, which inevitably increases the complexity and cost of the device. Furthermore, when various additional functions are provided, it is inconvenient that software cannot be involved in the time correction circuit.

Conventional on-demand color inkjet printers have a short flight distance, so the influence of speed differences between nozzles is relatively small. However, the difference in speed between the first and second drops has a large effect. In both on-demand and continuous-jet printers, it is necessary to further improve the accuracy of overlapping recording positions in color inkjet printers.

An object of the present invention is to provide a color inkjet printer with accurate dot positioning.

(Means for Solving the Problems) A color inkjet printer according to the present invention includes a plurality of nozzles that eject ink of different colors onto recording paper, and the positions of the nozzles correspond to dot recording positions on the recording paper. It is adjusted so that all colors are in the same position or on the same line, and each nozzle is equipped with charging means for charging the ink ejected from the nozzle and deflection means for deflecting the charged ink from the ejecting direction. a recording data storage means capable of storing data regarding the presence or absence of recording of each color at each dot recording position on the recording paper, shifted by a predetermined positional deviation correction corresponding to the mounting position of each nozzle; It is characterized by comprising a correction setting means for setting the above-mentioned positional deviation correction amount, and an output control means for reading out one set of data from the recorded data storage means for each read clock and outputting the data to each of the above-mentioned charging means. shall be.

(Function) The data given to the charging means of each nozzle is shifted by the amount of positional deviation correction. As a result, even though each ink is attached to the same dot recording position on the recording paper at different timings, the adjustment of the dot recording position of each color ink, which is necessary due to the position of each nozzle and individual differences, can be made easily. Can be done easily and accurately.

(Example) Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

In this embodiment, since the recording time position is corrected not by a delay circuit but by processing the data in the data buffer, the overlapping of the recording positions of each color can be adjusted accurately.

FIG. 2 shows the configuration of the continuous jet Hertzian color inkjet printer of this embodiment.

The difference from the conventional example shown in FIG. 7 is that a recording position setting device 1 is connected to the printer control circuit 3, and that the correction circuit 6 is omitted. Furthermore, as will be explained later, the data storage method of the buffer memory 4 is changed (see FIG. 1). Image data input from a host computer or an image source 1 is written into a buffer memory 4 of a control circuit 3 via an image interface 2. In this writing, the control circuit 3 performs arithmetic processing (see FIG. 4) according to the recording position data set by the recording position setter 14, and stores the image data as shown in FIG.

During recording, the control circuit 3 reads data stored in the buffer memory 4 and outputs it to the nozzle head IO via a print line buffer (print position controller) 5 that outputs the print position.

FIG. 3 shows the hardware parts forming the print line buffer 5. As shown in FIG. The essential function of the print line buffer 5 is that of an output data buffer from the perspective of the control circuit 3.

The print line buffer 5 has a memory 20.

Data is written into the memory 20 from the control circuit 3 during non-printing, and is read out using a counter address generated by the jet readout clock counter 2I that is synchronized with the rotation of the recording drum 13 during printing. address buffer 2
2.23 outputs write and read addresses, respectively.

This switching is performed by a control signal from the control circuit 3.

By the way, the time constant of charging particles when a jet is ejected from a nozzle is several μs, and the jet's 0N-OF
Depending on the timing of the F signal, slightly charged particles (particles with an intermediate charge amount between normal charged particles and uncharged particles) are generated, which greatly affects radiation quality deterioration.

Therefore, it is ideal to apply the ON-OFF signal immediately after the ink is turned into particles. In order to improve this problem, the number of slightly charged particles can be minimized by synchronizing the generated particles with the ON-OFF signal of the jet. Synchronization between the generated particles and the ON-OFF signal can be easily achieved by adding an ultrasonic vibrator to the nozzle. For this reason, a nozzle with an ultrasonic vibrator is used. Further, the oscillator 31 oscillates at a constant frequency, and the synchronization circuit and ink charging circuit 34 synchronizes the jet signal output at that frequency (via the delay circuit 33 as necessary).
Converts to 0V ink charge signal. The necessity and delay time of the delay circuit 33 is adjusted by experimentally examining the timing of jet breakage from the nozzle.

The frequency of the read clock is divided by the frequency divider 32 by the number of particles contained in 1 recording dot (not necessary when 1:1).

The contents of the buffer memory 4 provided from the memory 20 are as shown in FIG. This enables clear printing without fluctuations in dot recording positions. That is, the data is not uniform as shown in FIG. 9, but is input as data whose address is shifted by the amount of nozzle shift. In Figure 1, IY, IM, IC, IB, 2Y, 2M,
. . . are the first yellow data, the first magenta data, the first cyan data, the first black data, the second yellow data, the second magenta data, etc.・Indicates. Further, 0 is a signal that does not emit a jet. Here, the nozzles are arranged in the order of yellow, magenta, black, and cyan, and the nozzle deviation is l for each.
This is the address. Even if the nozzle deviation is not by one address, the address is similarly shifted and input. In addition,
The amount of nozzle deviation in the memory 4 can be easily set by a recording position setting device I4, which will be described later. It can also be investigated and adjusted experimentally.

The data buffer memory 20 may be one in which data is input manually in the form shown in FIG. 1 and outputted sequentially in response to a read clock. This results in positional deviation correction being possible in units of read dot clocks.

The present invention is characterized in that the contents of the memory 4 are configured as shown in FIG. There are many ways to reconstruct data as shown in Figure 1 using software, but they can be roughly divided into the following two.

■Once it is stored in memory as shown in Figure 9? Reconfigure after writing this.

2. Reconfigure the data in advance and then write it to the buffer memory.

The writing method is closely related to the configuration of the memory 20.

The easiest way to understand this is to use 1-bit data for each color when writing, provide four sets of address buffers for sequential writing and reading of four colors, and have four 1-bit memories. However, this configuration requires a large number of hardware components. For this reason, the print line buffer 5 is
In the configuration shown in the figure, it is practical to perform data reconfiguration using software.

FIG. 4 shows an example of a program flowchart for reconstructing yellow data. First, the maximum number of read addresses (step S
1) and the number to be shifted, the maximum number of write addresses (step S2) is set.

Take in the data at the read address (step S3), and if there is data by bit determination (step S4), write the data at the write address (step S5).

The read address (-capture address) is decreased (step S6), and data capture is continued until the address θ is reached. If the address reaches θ (step S7), the write address is still 0.
Since it is not, the bits at the remaining addresses are set to O (step S8).

The above procedure completes the reconstruction of the yellow data.

When reconfiguring four colors, this can be done by repeating the above operation four times for each color, or by expanding the write program portion of the memory for four colors.

Since this program is a simple reconfiguration operation, it does not need to be performed after writing to the buffer memory 4, and may be performed during or after processing such as color conversion performed within the control circuit and then written to the buffer memory 4. . This way you have more time.

FIG. 5 shows an example of the recording position setting device 14. The yellow position setting device is a rotary switch 31 and its manual buffer 35.
The set value is read in by the yellow position read command. Similarly, there are position setting devices for magenta, cyan, and black, but they are simplified and omitted in the figure.

Instead of the rotary switch 31, coded switches called thumbwheel switches or digital switches may be used. This is preferable because it requires fewer wiring lines. It is also suitable for connection to microprocessors.

FIG. 6 shows another recording position setting device 14. In FIG. The voltage of the power source 42 is converted into a set voltage by a variable resistor 43, which is a yellow position setting device, and is input to a multi-input terminal type AD converter 41.

In the case of other colors, the recording position is similarly set using variable resistors 44, 45, and 46.

In either case, the position setting is relative, and the amount of shift is also arbitrary, so it may be determined as appropriate.

(Effects of the Invention) Fine adjustment of the dot recording position of each color of ink can be easily and accurately performed.

Print positioning is possible for each readout clock, and the print jet dots are synchronized with the readout clock.
Compared to the conventional asynchronous type, the charge on the dots is more stable and more accurate positioning can be achieved.

Since position settings can be changed using software, less hardware is required and the cost is reduced.

Fine adjustments can also be made by multiplying the dot read clock by an integer.

Since it is composed of software, it is advantageous when adding or changing other functions. For example, lowering the nozzle pressure or changing the nozzle shape will result in a change in the flight time of the jet, which may result in insufficient or too coarse positioning range when relying solely on hardware. be. In such a case, it is necessary to replace parts or change the circuit, but with software, the advantage is that all you have to do is change the select switch, for example.

[Brief explanation of drawings]

FIG. 1 is an address map showing the storage method of image data. FIG. 2 is a block diagram showing the configuration of a color inkjet printer. FIG. 3 is a block diagram of the print line buffer and nozzle head. FIG. 4 is a flowchart of image data storage. 5 and 6 are circuit diagrams of the recording position setter, respectively. FIG. 7 is a block diagram showing the configuration of a conventional color inkjet printer. FIG. 8 is a block diagram of the correction circuit. FIG. 9 is an address map showing a conventional image data storage method. 9... Nozzle head, IO... Recording paper, 1
3. Recording drum. Patent applicant: Minolta Camera Co., Ltd. Agent: Patent attorney: Mr. Maeda and 2 others Figure 1 BK CM Y BK
CM Y Figure 2 L
JlE41!21 Figure 5 Figure 6 Figure 7 Figure 8

Claims (1)

[Claims] (1) Equipped with multiple nozzles that eject ink of different colors onto the recording paper, and the positions of the nozzles are adjusted so that the dot recording positions on the recording paper are at the same position or on the same line for all colors. an ink ejecting means for each nozzle including a charging means for charging the ink ejected from the nozzle and a deflection means for deflecting the charged ink from the ejecting direction; a recording data storage means that can store data regarding the presence or absence of recording by shifting it by a predetermined positional deviation correction amount corresponding to the mounting position of each nozzle; a correction setting means that sets the above-mentioned positional deviation correction amount; and output control means for reading out a set of data from the recording data storage means and outputting the data to each of the above-mentioned charging means.