JPH06278284A - Image forming apparatus and method - Google Patents

Abstract

PURPOSE:To suppress the generation of a streak or density irregularity due to the irregularity of recording characteristics between recording elements by alloting adjacent pixels to mutually different recording heads so as to record them by the respective recording heads and outputting the pixels in synchronous relation to the scanning of the recording heads to perform recording. CONSTITUTION:When an image is recorded on recording paper 4, the respective pixels of the pixel row in the scanning direction of a head carriage 11 are recorded by the ink droplets emitted from the respective nozzles of a plurality of heads 10B1, 10B2 recording the same black color to alternately record black pixels. Even with respect to the respective pixels in the nozzle row direction of the heads 10B1, 10B2, black pixels are alternately recorded by the ink droplets emitted from the recording nozzles of the heads 10B1, 10B2 of black ink. The pixels adjacent in the scanning moving direction of the head carriage and the nozzle row direction of the recording heads 10 with respect to the recording pixels recorded on recording paper are alternately recorded by the recording heads 10 different in ink color.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus having a plurality of recording elements, and a plurality of recording heads for recording with the same color are arranged in the scanning direction and the recording heads are scanned to form an image on a recording medium. The present invention relates to a device and a method thereof.

[0002]

2. Description of the Related Art Ink jet recording is a method of recording an image corresponding to a recording signal by ejecting ink droplets from a nozzle onto a recording medium according to a recording signal, which is low in running cost and quiet recording. Widely used as a method. In a printer that performs recording by scanning a recording head by such an inkjet method, a recording head having a plurality of nozzles linearly arranged in a direction substantially orthogonal to the relative movement direction of the recording medium and the recording head is scanned. By performing the printing, the data having the width corresponding to the number of nozzles can be printed at one time by one scan of the print head, and the speedup can be achieved relatively easily.

When a gradation image is expressed by such an ink jet recording method, the size of the ejected liquid droplets may be changed according to the gradation degree. However, at present, there is no practical method for such gradation recording. Therefore, normally, gradation expression is performed by controlling the number of ejected ink droplets per unit area by pseudo halftone image processing. In addition, the size of one ink droplet is reduced, and a plurality of ink droplets are shot (landed) at approximately the same position to form one pixel, and the number of shots (landing number) is controlled to change the gradation. There is a so-called multi-droplet method for expressing. This method can perform gradation recording without lowering the resolution, and is particularly effective for inkjet recording in which it is difficult to greatly change the size of each ink droplet.

[0004]

However, in the conventional multi-droplet method, since one pixel is formed by a plurality of ink droplets ejected from one nozzle, there is a variation in the ink droplet volume for each nozzle. However, there has been a problem that streaks or uneven density occur in an image that should originally be uniform. Such a problem becomes noticeable when the number of nozzles of the recording head is increased so that recording can be performed at high speed and the recording width that can be recorded by one relative scan between the recording head and the recording paper is increased. . That is, when the recording width is increased as described above, the low-frequency spatial frequency components of the density unevenness are increased, the unevenness is more noticeable, and the quality of the recorded image is deteriorated. In particular, when gradation expression is performed, unevenness is likely to be conspicuous, and density unevenness and streaks in a recorded image can be recognized even if ink ejection variation between nozzles is about several percent.

In order to avoid such a problem, it is necessary to manufacture the recording head very precisely in order to suppress the variation in the ink droplet volume discharged by the conventional multi-droplet method between nozzles as much as possible. . As a result, there are problems such as an increase in manufacturing cost and a decrease in manufacturing yield. Further, as a method of eliminating unevenness in recording density by software, if image processing such as error diffusion method or the like is performed on the recording data to cancel the variation in ink droplet volume between nozzles, the entire system There was the problem of raising costs. In addition, even if such image processing is performed, if the variation in the ejected ink droplet volume changes with time between nozzles, it is necessary to readjust the number of ink droplets to be ejected, resulting in poor maintainability. I have a problem.

The present invention has been made in view of the above-mentioned conventional example, and provides an image forming apparatus and a method thereof in which generation of streaks and density unevenness due to variations in recording characteristics among recording elements of a recording head is suppressed. To aim.

[0007]

In order to achieve the above object, the image forming apparatus of the present invention has the following constitution. That is, an image forming apparatus that includes a plurality of recording elements and that arranges a plurality of recording heads for recording in the same color in the scanning direction and scans the recording heads to form an image on a recording medium, The scanning means for scanning the recording head for recording and the recording head for each pixel of the image data formed by one scanning of the recording head are different from each other in adjacent pixels in the scanning direction or the arrangement direction of the recording elements. Allocation means for allocating to each recording head so as to be recorded, and recording means for outputting the image data allocated by the allocating means to each of the recording heads in synchronization with the scanning of the recording head by the scanning means. Have and.

In order to achieve the above object, the image forming method of the present invention comprises the following steps. That is, it is an image forming method of forming an image by providing an ink jet type recording head having a plurality of nozzles, wherein a plurality of recording heads of the same ink color are provided, and the amount of ink droplets ejected from each recording head of the same ink color. The drive conditions of each recording head are controlled so that they are the same.

[0009]

With the above arrangement, each pixel of the image data formed by one scan of the recording head for recording with the same color is a recording head in which the adjacent pixels in the scanning direction or the arrangement direction of the recording elements are different from each other. It is assigned to each print head so as to be printed, and in synchronization with the scanning of these print heads, the assigned image data is output to each print head for printing.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram for explaining the schematic arrangement of an image forming apparatus according to an embodiment of the present invention. In this image forming apparatus, a color image scanner which reads a color original image and outputs digital color image data is shown. 1 and a printer unit 2 for recording a color image on a recording sheet 4 based on digital color image data output from the reader unit 1.

In the reader section 1, light is irradiated from an exposure lamp (not shown) onto a document on a document table, and reflected light from the document is passed through a lens (not shown) to the image sensor 3 (this embodiment). Then, a CCD sensor is adopted). The image sensor 3 can read a document in full color in line units. This reader unit 1 is the main C
It is controlled by the PU 100. Also, the main CPU
Reference numeral 100 denotes a printer control CPU 102 that controls the control operation of the printer unit 2, a reader control CPU 104 that controls the reading control operation of the reader unit 1, a main image processing unit 106 that controls the image processing operation of the reader unit 1, and various control information by the operator. The input operation unit 108 is connected.

The main image processing unit 106 described above performs image processing such as masking, black extraction, multi-valued conversion, and γ correction.
Further, a synchronization memory 110 is connected to the output side of the main image processing unit 106, and this synchronization memory 110 absorbs the time variation of the input operation and the recording head 1 described above.
This is for performing delay correction due to the mechanical arrangement of 0. Then, the output of the synchronous memory 110 is sent to the head driver 115, is output to the recording head 10 under the control of the printer control CPU 102, and is printed on the recording paper. Further, the printer control CPU 102 is the printer unit 2
Is connected to the printer unit drive system 114 that controls the input drive of the. Reference numeral 102a stores a control program (shown in the flowchart of FIG. 6) executed by the printer control CPU 102, and 102b is a RAM used as a work area of the CPU 102 and storing flags F1, F2 and the like described later. .

Further, in the reader unit 1, the reader control C
The PU 104 is an input system image processing unit 1 that performs necessary correction processing in a reading system such as shading correction, color correction, and γ correction.
16 and a reader unit drive system 118 that controls the input drive of the reader unit 1. Further, the input system image processing unit 116 is connected to the CCD sensor 3, and the input system image processing unit 116 is connected to the main image processing unit 106.

FIG. 2 is a schematic view for explaining the printer unit 2 of the image forming apparatus of this embodiment, and is a guide rail 1 of two.
5a, 15b, recording head (inkjet head) 1
No. 0 and its carriage 11, ink supply devices 12 to 14, a head recovery device 20, and a transmission system (not shown).

The ink supply devices 12 to 14 are for storing ink and supplying a required amount of ink to the recording head 10, and have an ink tank 14, an ink pump 13, an ink supply tube 12 and the like, Ink is forcibly supplied to the recording head 10 through the ink supply tube 12. Recording head 10 and ink supply device 12-
14 are mounted on the head carriage 11 and the ink carriage, respectively. Belt 16 for these carriages
Is fixed, and the belt 16 includes a pulley 17a and a pulley 17b attached to a rotary shaft 18 of a motor 19.
It is stretched between and. As a result, the belt 16 is moved in accordance with the rotation of the motor 19, so that the belt 16 is reciprocated in the arrow S direction along the guide rails 15a and 15b.

The head recovery device 20 is provided so as to face the recording head 10 located at the home position HP in order to maintain the stability of ink ejection of the recording head 10, and will be specifically described below. Performs various actions. When not operating, the recording head 10 is moved forward in the direction of arrow f to cap the recording head 10 to prevent evaporation of ink from inside the head nozzle (capping operation). In addition, in order to discharge air bubbles, dust, and the like in the nozzles of the recording head 10 before starting image recording, the ink pump 13 is used to pressurize the ink flow path of the recording head 10 to forcibly discharge the ink from the nozzles. When performing (pressure recovery operation), the ink discharged from the nozzle is recovered.

FIG. 3 is a perspective view showing a schematic structure of the ink jet recording head 10 of this embodiment.
Reference numeral 0 denotes an electrothermal conversion pair 22, an electrode 23, a nozzle wall 24, and a top plate 25 formed on a substrate 21 through semiconductor manufacturing process steps such as etching, vapor deposition, and sputtering.
It consists of The recording ink is supplied from the ink tank 14 of FIG. 2 through the ink supply tube 12 into the common liquid chamber 26 of the recording head 10. In the figure, 27 is a connector for supply. The ink thus supplied into the common liquid chamber 26 is supplied into the nozzle 28 by the capillary phenomenon, and is stably held by forming a meniscus on the ejection port surface at the tip of the nozzle. When the electrothermal converter 22 is energized, the ink on the electrothermal converter surface is heated to cause a bubbling phenomenon, and the bubbling energy ejects ink droplets from the ejection port surface 29.

With the structure as described above, the nozzle density 16
It is possible to manufacture the inkjet recording head 10 with a high-density nozzle arrangement such as nozzles / mm.

FIGS. 4 and 5 are explanatory views for explaining a recording method on the recording sheet 4 by the image forming apparatus of this embodiment. In the present embodiment, as shown in FIG. 4, the head carriage 1 that reciprocates in the direction of arrow S at the moving speed V.
A plurality of recording heads 10 of the same ink color are provided on one (two recording heads of each color in this embodiment, and hereinafter, recording heads 1 of the same ink color are used.
0 will be described for the case of two for each color). By controlling the ejection operation of ink droplets by the recording heads 10 ₁ , 10 ₂ of the same ink color, an image is recorded on the recording paper 4. ing. In FIG. 4, 1
0 _Y2 and 10 _Y1 are heads for recording yellow, 10 _M2 and 1
0 _M1 is a head for recording magenta, 10 _C2 and 10 _C1 are heads for recording cyan, and 10 _B2 and 10 _B1 are heads for recording black.

In the present embodiment, as shown in FIG. 5, when recording ink droplets on the recording paper 4, the head carriage 11 scans and moves in the direction of the arrow S, and first precedes the first carriage. Recording is performed on the recording sheet 4 by the black head 10 _B1 . In FIG. 5, reference numeral 500 indicates a dot printed by the first black head 10 _B1 , and 501 indicates a dot printed by the second black head 10 _B2 . As described above, in this case, printing is performed by using nozzles every other nozzle, such as nozzles having nozzle numbers n, n + 2, n + 4, ... (N; integer) for the pixel row k. For the next pixel row (k + 1), this time, the nozzle number n that was not printed by the nozzle of the previous pixel row k
Recording is performed using the nozzles of +1, n + 3, n + 5, ... (N; integer), and for the next pixel row (k + 2), the nozzle number n, n +
2, n + 4, ... (N; integer) nozzles are used for recording.

Then, the subsequent second black head 1
When recording is performed on the recording paper 4 with 0 _B2 , the pixels not recorded by the first black head 10 _B1 are complemented. That is, for the pixel row k, recording is performed using nozzles having nozzle numbers n + 1, n + 3, n + 5, ... (N; integer), and for the next pixel row (k + 1), nozzle numbers n, n + 2. , N + 4, ... (n; integer) are used for recording. For the next pixel row (k + 2), the nozzle numbers n + 1 and n + are again set.
3, n + 5 ... (n; integer) nozzles are used for recording,
As a result, all the pixels corresponding to the print data are printed on the printing paper 4 by one scanning operation of the head carriage 11.

When an image is recorded on the recording paper 4 as in the present embodiment, a plurality of heads 1 for recording the same black color for each pixel of the pixel row of the head carriage 11 in the scanning direction.
Black pixels are alternately recorded by ink droplets ejected from the nozzles 0 _B1 and 10 _B2 , and the black ink head 10 is also applied to each pixel in the nozzle row direction of the heads 10 _B1 and 10 _B2.
Black pixels are alternately recorded by the ink droplets ejected from the recording nozzles _B1 , _10B2 . In this way, the recording paper 4
Head carriage 1 for each recording pixel to be recorded on
By alternately recording the pixels adjacent to each other in the scanning movement direction of 1 and the nozzle row direction of the recording head 10 by the recording heads 10 having the same ink color, the characteristic difference of the ink droplets ejected from each nozzle of the recording head 10 can be reduced. It is possible to eliminate the streak-like difference in recording density caused and to record a high-quality image with little image deterioration.

Further, when the maximum driving frequency of the recording head 10 is f _op and the number of the recording heads 10 is one, the scanning speed V of the head carriage 11 for recording each pixel of the recording pixel pitch d. ₁ must be scanned as V ₁ = d / T = d · f _op (1 / T = f _op , T; recording nozzle drive time). However, when recording each pixel with the pixel pitch d using two recording heads of the same ink color as in the present embodiment, the recording pixel pitch of each recording nozzle of the recording head 10 may be “2d”. From
In this case, the head carriage 11 is set to the scanning speed V
₂ , that is, V ₂ = 2d / T = 2d · f _op = 2V ₁ . When recording is performed with two recording heads in this manner, it becomes possible to perform scanning and recording at a speed twice as fast as in the case of using one recording head, and the time for recording an image on the recording paper 4 is increased. Can also be cut in half.

Similarly, the cyan recording head 10 is used.
_C1 , 10 _C2 , magenta recording heads 10 _M1 , 10 _M2 ,
Recording is performed using the yellow recording heads 10 _Y1 and 10 _Y2, and by controlling the ejection operation of the ink droplets in each head, the variations in the amount of ink droplets ejected from each nozzle are averaged, and streaks occur. It is possible to record a high-quality full-color image while suppressing image deterioration such as streaks or unevenness.

An operation example of recording one scanning line using a plurality of recording heads for recording the same color in this way will be described with reference to the flowchart of FIG. The process shown in FIG. 6 is executed by the printer control CPU 102, and the control program for performing this process is the program memory 1 of the CPU 102.
It is stored in 02a. Although FIG. 6 shows an example of recording control using the black heads 10 _B1 and 10 _B2 , it goes without saying that the same can be realized for other colors.

The process shown in FIG. 6 is started when the processed image data from the reader unit 1 is input to the synchronous memory 110. First, in step S1, the rotation driving of the carriage motor 19 is started to convey the carriage 11. And the flags F1 and F2 (provided in the RAM 102b) are both set to "0". Then step S
In step 2, it is checked whether or not it is time for the preceding head 10 _B1 to reach the recording position and eject ink, and if so, the process proceeds to step S3 to determine whether the flag F1 is "0". If "0", the process proceeds to step S4, the print data is multiplied by mask data for masking the data of the odd nozzle, and the data is output to the head 10 _B1 in step S6. On the other hand, when the flag F1 is not "0", the process proceeds to step S5, the print data is multiplied by mask data for masking the data of the even nozzles, and the data is output to the head 10 _B1 in step S6. Further, in step S6, the value of the flag F1 is inverted.

Next, in step S7, the succeeding head 1
It is determined whether 0 _B2 has come to the print area. If not, the process proceeds to step S13, the head 10 _B1 is driven, and recording is performed. When the head 10 _B2 is in the print area, the process proceeds to step S8 to determine whether the print timing of the head 10 _B2 has come, and if so, the process proceeds to step S9 to check the value of the flag F2. Flag F here
If the value of 2 is "0", the process proceeds to step S10. In contrast to step S4 described above, the print data is multiplied by the mask data for masking the even nozzle data, and the data is output to the head 10 _B2 in step S12. On the other hand, step S9
When the value of the flag F2 is not "0" in step S11, the process proceeds to step S11. In contrast to step S5 described above, the print data is multiplied by mask data for masking the odd nozzle data, and the result is output to the head 10 _B2 . . Further step S12
In step S13, the flag F2 is inverted, and the heads 10 _B1 and 10 _B2 are driven to perform recording in step S13.

Next, in step S14, it is determined whether or not the preceding head 10 _B1 goes out of the print area. If not, the process returns to step S2 to execute the above-mentioned processing. Leading head 10 _{B1 on} the line currently being scanned
When the recording according to step S14 is finished,
In step 15, it is determined whether the succeeding head 10 _{B2 is} still in the print area, and if so, the process returns to step S8 and the above-described processing is performed. Thus, in step S15,
When the head 10 _B2 goes out of the print area, the recording of the line currently being scanned is completed. Therefore, the process proceeds to step S16, the carriage 11 is returned to the home position, and the recording sheet 4
Is conveyed by an amount corresponding to the recorded width, and the recording for one scan is completed.

In this way, the odd-numbered nozzles and the even-numbered nozzles of the heads 10 _B1 and 10 _B2 are alternately used,
By recording with the subsequent 10 _B2 so as to complement the pixels recorded with the preceding head 10 _B1 , there is an effect that a high-quality image without density unevenness can be recorded.

By the way, when recording each pixel on the recording paper 4 with ink droplets ejected from a plurality of recording heads 10 for recording the same ink color as in the apparatus of this embodiment,
There may be a difference in the ejection amount of the recording ink droplets of each recording head 10 due to variations in manufacturing of the plurality of recording heads 10 or the like.

For example, as shown in FIGS. 7A and 7B, the recording pixel pitch d (d when the recording pixel density is 400 dpi is d).
= 63.5 μm), when recording pixels on the recording paper 4, the recording dot diameter on the recording paper 4 is such that there is no gap between adjacent recording dots. D ₁ = 2 ^1/2 d (recording (When the pixel density is 400 dpi, d ₀ = 89.8 μm)
The recording head having the ejected ink droplet amount P _{1 which} is

On the other hand, as shown in FIGS. 7C and 7D,
Ejection amount of ink droplet P ₂ is less than _{P 1 (P 1> P 2} )
When recording is performed on the recording paper 4 by the recording head, the recording dot diameter d ₂ on the recording paper 4 becomes smaller than the dot diameter d ₁ shown in (A) (d ₁ > d ₂ ). As a result, as shown in FIG. 8, the image density D ₂ recorded by the second recording head having a small ink ejection amount (ink ejection amount P ₂ ) is the same as that of the first recording head having the ink ejection amount P ₁ . The image density may be lower than the recorded image density D ₁ .

Therefore, in this embodiment, a plurality of recording heads of the same ink color are provided, and the recording heads for recording the same color select and record each pixel of the pixel row in the scanning movement direction of the head carriage 11. In this case, ink from each nozzle of a plurality of recording heads of the same ink color is prevented so that deterioration in image quality due to difference in recording density (difference in ink diameter) due to manufacturing variations of recording heads does not occur. The discharge amount is controlled to be the same.

FIGS. 9 and 10 are model diagrams for explaining the first embodiment for controlling the amounts of ink droplets ejected from the respective nozzles of a plurality of recording heads of the same ink color to be the same. Is.

When ink droplets are ejected from the ink jet recording head 10 as shown in FIG. 3, the voltage shown in FIG. 9 is applied to the electrothermal converter 22 of each nozzle by V (v).
Then, a pulse signal having a pulse width of W (μsec) is applied, and ink droplets are ejected from each nozzle due to a bubbling phenomenon on the heating surface of the electrothermal converter 22.

Here, as shown in FIG. 10, as the pulse voltage value of the pulse signal applied to the electrothermal converter 22 of the recording head 10 is increased, the ink ejection amount P from each nozzle of the recording head 10 is increased. Therefore, for example, the pulse voltage value V applied to the electrothermal converter 22 of each nozzle of the first recording head for which the ink ejection amount is large is used.
_The pulse voltage value V ₂ applied to each nozzle of the second recording head, which has a small ink ejection amount, is increased relative to ₁ (V ₁ <V ₂ ), and the first recording head and the second recording head By adjusting the amount of ink droplets ejected from the same amount as the amount of ejected ink droplets as P (pl), it is possible to eliminate the height difference of the image density recorded by the recording head, and to eliminate streaks or uneven portions for high quality. You will be able to record images.

The pulse voltage value applied to each recording head may be manually input by the operator through the operation unit 108 and adjusted. Alternatively, if the ink ejection amount from each nozzle of the recording head is P
The pulse voltage value V of (pl) is measured, and the data indicating the pulse voltage value V is stored in the data storage ROM 10a (see FIG. 1) provided in the recording head. Then, after the recording head is mounted on the main body of the image forming apparatus, the printer control CPU 102 reads the data of the pulse voltage value V and instructs the head driver 115 to specify the drive voltage according to the read voltage value. Can also be configured. [Embodiment 2] FIG. 11 is a model for explaining a second embodiment for controlling the amount of ink droplets ejected from the nozzles of each head of a plurality of recording heads for recording with the same color. It is a figure. In this second embodiment,
As shown in FIG. 11, in the electrothermal converter 22 of each nozzle of the recording head, the pulse width W ₁ (μsec) of the voltage applied to each nozzle of the first recording head having a large ink ejection amount is compared. Then, the pulse width W ₂ (μsec) applied to each nozzle of the second recording head with a small ink ejection amount is controlled to be large (W ₁ <W ₂ ) and the first recording of the same ink color is performed. The amount of ink droplets ejected from the head and the second recording head is the same as P (pl). [Embodiment 3] FIGS. 12 and 13 explain a third embodiment for controlling so that the amount of ink droplets ejected from the nozzles of each of a plurality of recording heads of the same ink color is the same. In the third embodiment, a pulse voltage composed of two pulse signals as shown in FIG. 12 is applied to the electrothermal converter 22 of each nozzle of each recording head.

Of the pulse voltages, the first pulse voltage applied to the electrothermal converter 22 first has a pulse width w that gives energy to the extent that ink bubbling does not occur on the electrothermal converter surface. It is set. After the ink on the heating surface of the electrothermal converter 22 is heated by the pulse voltage to raise the temperature, a pulse voltage having a pulse width W (W> w) is electrothermally generated as the second pulse voltage as the main heat pulse. An ink droplet is ejected from the recording head by applying it to the converter 22 to foam the ink.

Then, for each of the plurality of recording heads for recording with the same ink color, the sub-heat pulse width W ₁ applied to the recording head for which the ink ejection amount is large.
By increasing the sub-heat pulse width w ₂ (μsec) applied to the recording head having a smaller ink ejection amount than (μsec) (w ₁ <w ₂ ), the first ink of the same ink color can be obtained. The amount of ink droplets ejected from the recording head and the second recording head is controlled to be the same as P (pl).

Furthermore, for each print head of the same ink color, the pulse voltage of both the pulse width W of the second pulse voltage and the pulse width w of the first pulse voltage that causes the ink bubbling phenomenon By adopting a configuration for controlling the pulse width and further a configuration for controlling the magnitude of the application interval time t (μsec) of the first pulse voltage and the second pulse voltage, each nozzle of each recording head can be controlled. It becomes possible to control the ejected ink droplet amount of (1) with higher accuracy. [Embodiment 4] FIG. 14 and FIG. 15 are a fourth embodiment for controlling the number of ink droplets ejected from the nozzles of each recording head of a plurality of recording heads for recording the same ink color to be the same. It is a model figure for explaining. In the fourth embodiment, a pulse voltage composed of a plurality of sub heat pulse voltages and a main heat pulse voltage as shown in FIG. 14 is applied to the electrothermal converter 22 of each nozzle of each recording head.

That is, in the fourth embodiment, M pulses of the sub-heat pulse voltage having the pulse width w (μsec) of energy to the extent that the ink bubbling phenomenon does not occur are applied to the electrothermal converter 22 of each recording head. After that, a main heat pulse voltage having a pulse width W (μsec) is applied. Then, the pulse number M of the sub-heat pulse voltage having this pulse width w (μsec)
Is controlled for each print head, and the number M of sub-heat pulses applied to the print head with the largest ink ejection amount is applied.
By controlling the driving condition of each recording head so that the number M _{2 of} sub-heat pulses applied to the recording head whose ink ejection amount is smaller than that of ₁ , the ink ejection amount from each recording head is controlled. I try to be the same.

The present invention is particularly effective in an ink jet recording head and a recording apparatus for recording by forming flying droplets by utilizing thermal energy among the ink jet recording methods.

Regarding its typical structure and principle, see, for example, US Pat. Nos. 4,723,129 and 4740.
What is done using the basic principles disclosed in 796 is preferred. This method can be applied to both the so-called on-demand type and continuous type, but especially in the case of the on-demand type, liquid (ink)
By applying at least one drive signal to the electrothermal transducer arranged corresponding to the sheet or liquid path in which is stored, which corresponds to the recorded information and gives a rapid temperature rise exceeding nucleate boiling. Since the electrothermal converter is caused to generate heat energy to cause film boiling on the heat-acting surface of the recording head, as a result, bubbles in the liquid (ink) corresponding to the drive signal in a one-to-one relationship can be formed. It is valid. The liquid (ink) is ejected through the ejection openings by the growth and contraction of the bubbles to form at least one droplet. It is more preferable to make this drive signal in a pulse shape, because bubbles can be grown and contracted immediately and appropriately, and thus a liquid (ink) with excellent responsiveness can be achieved.

As the pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. If the conditions described in US Pat. No. 4,313,124 of the invention relating to the rate of temperature rise on the heat acting surface are adopted, excellent recording can be performed.

As the constitution of the recording head, in addition to the combination constitution of the discharge port, the liquid passage, and the electrothermal converter (the linear liquid passage or the right-angled liquid passage) as disclosed in the above-mentioned specifications, A configuration using US Pat. No. 4,558,333 or US Pat. No. 4,459,600, which discloses a configuration in which the heat-acting surface is arranged in a bending region, may be used. In addition, Japanese Unexamined Patent Application Publication No. Sho 5-5 discloses a configuration in which a common slit is used as a discharge portion of the electrothermal converter for a plurality of electrothermal converters.
Japanese Patent Application Laid-Open No. 9-123670 and Japanese Patent Application Laid-Open No. Sho 5 (1993) -58
A configuration based on Japanese Patent Publication No. 9-138461 may also be used.

Further, as a full line type recording head having a length corresponding to the maximum recording medium width that can be recorded by the recording apparatus, the length can be increased by combining a plurality of recording heads as disclosed in the above-mentioned specification. Either of the structure satisfying the requirement or the structure as one recording head integrally formed may be used.

In addition, by being attached to the apparatus main body, it can be electrically connected to the apparatus main body and can be supplied with ink from the apparatus main body by a replaceable chip type recording head or the recording head itself. Alternatively, a cartridge type recording head provided with an ink tank may be used.

Further, it is preferable to add recovery means for the recording head, preliminary auxiliary means, etc., which are provided as a constituent of the recording apparatus of the present invention, because the effect of the present invention can be further stabilized. . Specific examples thereof include capping means, cleaning means, pressurizing or suctioning means for the recording head, preheating means using an electrothermal converter or another heating element or a combination thereof, and recording. It is also effective to perform a stable recording by performing a preliminary discharge mode in which another discharge is performed.

Further, the recording mode of the recording apparatus is not limited to the recording mode of only the mainstream color such as black, but the recording head may be integrally formed or a plurality of combinations may be used. Alternatively, the device may be provided with at least one of full-color mixed colors.

In the embodiments of the present invention described above, the ink is described as a liquid, but it is an ink that solidifies at room temperature or below and that softens at room temperature, or is a liquid, or the above-mentioned. In the inkjet method, it is common to control the temperature of the ink itself within a range of 30 ° C to 70 ° C to control the temperature of the ink so that the viscosity of the ink is within a stable ejection range. It is sufficient that the ink is liquid.

In addition, the temperature rise due to the thermal energy is positively prevented by using it as the energy for changing the state of the ink from the solid state to the liquid state, or the ink is solidified in a standing state for the purpose of preventing evaporation of the ink. In some cases, such as ink that is liquefied by applying heat energy according to a recording signal and ejected as a liquid ink, or one that has already started to solidify when it reaches a recording medium. The use of an ink having a property of being liquefied only by heat energy is also applicable to the present invention. In such a case, the ink is disclosed in JP-A-54-5684.
No. 7 or JP-A-60-71260, a mode in which the porous sheet is opposed to the electrothermal converter in the state of being held as a liquid or solid in the recess or through hole of the porous sheet. May be In the present invention, the most effective one for each of the above-mentioned inks is to execute the above-mentioned film boiling method.

In addition, as a form of the recording apparatus according to the present invention, a copying apparatus combined with the above-mentioned reader or the like, and further, as an image output terminal of information processing equipment such as a word processor or a computer, are integrally or separately provided. Other than those provided, it may take the form of a facsimile machine having a transmission / reception function.

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of a single device. Further, it goes without saying that the present invention can be applied to the case where it is achieved by supplying a program for implementing the present invention to a system or an apparatus.

As described above, according to this embodiment, in an image forming apparatus for forming an image using an ink jet type recording head having a plurality of ink ejection ports (nozzles), a plurality of recording heads for recording in the same color. By controlling the recording method on the recording paper by the plurality of recording heads and the driving conditions of the recording heads of the same ink color, density unevenness due to variations in ejection characteristics between nozzles of each recording head is provided. It is possible to prevent high-quality images by preventing image deterioration due to streaks, streaks, and differences in density.

[0056]

As described above, according to the present invention, there is an effect that it is possible to suppress the occurrence of streaks and uneven density due to variations in recording characteristics among recording elements of the recording head.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of an image forming apparatus according to a first exemplary embodiment of the present invention.

FIG. 2 is a schematic diagram of an inkjet recording unit of the image forming apparatus according to the present exemplary embodiment.

FIG. 3 is a schematic diagram of an ink jet recording head of this embodiment.

FIG. 4 is an explanatory diagram of a recording head unit of the image forming apparatus according to the present exemplary embodiment.

FIG. 5 is a diagram illustrating an image recording method by the image forming apparatus according to the present exemplary embodiment.

FIG. 6 is a flowchart showing a recording process of a black image in the image forming apparatus of this embodiment.

FIG. 7 is a model diagram showing a formation state of recording dots by an inkjet recording method.

FIG. 8 is a graph showing the relationship between image data and recording density on recording paper.

FIG. 9 is a model diagram of a pulse signal applied to a recording head.

FIG. 10 is a graph showing the relationship between the amount of ink droplets ejected by the recording head and the voltage applied to the head.

FIG. 11 is a graph showing the relationship between the amount of ink droplets ejected by the recording head and the pulse width applied to the head.

FIG. 12 is a model diagram of a pulse signal applied to a recording head.

FIG. 13 is a graph showing the relationship between the amount of ink droplets ejected by the recording head and the head-applied sub-heat voltage pulse width.

FIG. 14 is a model diagram of a pulse signal applied to a recording head.

FIG. 15 is a graph showing the relationship between the amount of ink droplets ejected by the recording head and the number of sub-multipulses.

[Explanation of symbols]

 1 Reader Unit 2 Printer Unit 3 Image Sensor 4 Recording Paper 10 Recording Head 11 Carriage 14 Ink Tank 19 Carriage Motor 100 Main CPU 102 Printer Control CPU 104 Reader Control CPU 106 Main Image Processing Unit 108 Operation Unit 110 Synchronous Memory 114 Printer Unit Drive System 115 head driver 116 input system image processing unit 118 reader unit driving system

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location B41J 3/54 9012-2C B41J 3/04 103 X

Claims (7)

[Claims] 1. An image forming apparatus, comprising a plurality of recording elements, wherein a plurality of recording heads for recording with the same color are arranged in a scanning direction, and the recording heads are scanned to form an image on a recording medium. A scanning unit that scans a print head that prints in the same color and each pixel of image data formed by one scan of the print head are different from each other in adjacent pixels in the scan direction or the arrangement direction of the print elements. Allocation means for allocating to each recording head so as to be recorded by the recording head, and image data allocated by the allocating means is output to each of the recording heads in synchronization with scanning of the recording head by the scanning means. An image forming apparatus, comprising: 2. An image forming method for forming an image on a recording medium by arranging a plurality of recording heads for recording with the same color in a scanning direction, the recording head comprising a plurality of recording elements, the image forming method comprising: Each pixel of the image data formed by one scan of the recording head is assigned to each recording head so that adjacent pixels in the scanning direction or the arrangement direction of the recording elements are recorded by different recording heads, and the recording is performed. An image forming method, wherein image data assigned in synchronization with scanning of the head is output to each of the recording heads for recording. 3. An image forming method for forming an image by providing an ink jet type recording head having a plurality of nozzles, wherein a plurality of recording heads of the same ink color are provided, and ink ejected from each recording head of the same ink color. So that the drop volume is the same,
An image forming method characterized by controlling driving conditions of each recording head. 4. An image forming method for forming an image using an ink jet type recording head having a plurality of nozzles, wherein a plurality of recording heads of the same ink color are provided, and recording is performed on recording pixels to be recorded by each recording head. Pixels adjacent in the scanning movement direction of the head and the nozzle row direction of the recording head are
Recording with different recording heads of the same ink color,
An image forming method, characterized in that drive conditions of each recording head are controlled so that the same amount of ink droplets is ejected from each recording head of the same ink color. 5. A pulse voltage condition applied to each recording head is controlled as a driving condition of each recording head so that the plurality of recording heads of the same ink color have the same ejected ink droplet amount. Any one of claims 3 to 4
The image forming method according to item. 6. The image forming apparatus according to claim 1, wherein the recording head is an inkjet recording head that performs recording by ejecting ink. 7. The recording head is a recording head which ejects ink by utilizing thermal energy, and is provided with a thermal energy converter for generating thermal energy applied to the ink. Item 6. The image forming apparatus according to Item 6.