JPH06135005A - Image forming system - Google Patents

Abstract

PURPOSE:To eliminate fluctuation of print density due to temperature variation of recording head by providing means for correcting the recording density of recording head based on the decision results of density distribution in main scanning direction. CONSTITUTION:When a region having density higher than a level (d) endures longer than L1 starting from a position (a), a density deciding section 13 makes a decision that correction is required for print density. Correction data 0, 1, 2 corresponding to main scanning position is inputted to a correction data memory 14 and when the region having density higher than level (d) endures longer than L2, a decision is made that a greater correction is required and the value of correction data 2 is inputted to main scanning positions (b)-(c). When the region having density higher than the level (d) disappears, the correction data is returned back to 0 and a decision is made that no correction is required. When printing is carried out subsequently, print pulse width is modified depending on the aforementioned correction data. Print pulse width W0 corresponds to a case where no correction is required and the pulse width becomes narrower in the order of W1, W2 according to the extent of correction.

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 for visualizing an image on a recording material by scanning a recording head in the main scanning direction.

More specifically, according to the present invention, for example, an image reading unit scans the main scanning direction of an original and moves in the sub scanning direction to read the original and print with an inkjet multi-head. The present invention relates to an image forming apparatus applicable to.

[0003]

2. Description of the Related Art FIG. 7 shows a conventional reading device in which a CCD line sensor scans an original in the main scanning direction and moves it in the sub-scanning direction by the reading width. This drawing is a configuration diagram of the reading device as viewed from above, and a CCD unit 64 equipped with a CCD line sensor moves on a main scanning rail 63 in the main scanning direction to scan an original. Here, the CCD unit 64 is first in a position detected by the main-scanning home position sensor 65 and the sub-scanning home position sensor 66, and the CCD unit 64 reciprocates on the main-scanning rail 63 in the first scan, and again performs the main-scanning. Return to the position of the home position sensor 65. After the first scan is completed, the CCD unit 64 is moved to the sub-scanning rail 6
The first scan is moved in the sub-scan direction by the read width (that is, the length of the line sensor) in the main scan, and the second scan is started. By repeating this operation, the entire surface of the original is read.

FIG. 8 shows an ink jet type printing apparatus, which visualizes image data from the reading apparatus shown in FIG. Here, the recording paper 71 is conveyed in the direction C shown by the paper discharge roller 72 and the sub-scanning roller 73 driven by the sub-scanning motor 77. In addition, the recording head 16
Scans the recording paper 71 with the main scanning motor 74.

The recording head 16 has a multi-head structure in which a plurality of inkjet nozzles are arranged,
Cyan (C), magenta (M), yellow (Y), and black (Bk) color heads are sequentially arranged on this head. Then, by ejecting ink from these heads, full-color printing is performed. When the printing for one scan is completed in the main scanning direction, the recording paper 71 is conveyed by the printing width, and the same printing is repeated thereafter.

[0006]

However, in such conventional ink jet recording, the head temperature rises due to printing, and the ink viscosity decreases as the temperature rises. As a result, the amount of ink droplets increases. Is increased and the print density is increased, which is a disadvantage.

For example, even if one line is printed at the same density, the head temperature rises toward the end of the scan and the print density becomes dark, which causes uneven density.

In order to avoid such an inconvenience, it is conceivable that the temperature of the recording head is detected by a sensor such as a thermocouple and the temperature of the head itself is controlled by a heater or a fan. In the form, since there is a time lag between when the head temperature is detected and when the control is applied, there is a problem that a sudden head temperature change does not occur in time and control is difficult.

Therefore, an object of the present invention is to provide an image forming apparatus which eliminates the unevenness of the print density due to the temperature change of the recording head.

[0010]

To achieve the above object, the present invention provides an image forming apparatus for visualizing an image on a recording material in a main scanning direction using a recording head. Prior to driving the recording head, based on the determination means for determining the density distribution in the main scanning direction, and the determination result obtained from the determination means,
And a correction unit for correcting the recording density of the recording head.

In addition to the above construction, an image reading unit is further provided, and an image in the main scanning direction is prescanned before the reading unit reads the image in the main scanning direction, and the image is obtained by the prescan. It is preferable to input the density data to the determination unit.

[0012]

According to the present invention, when the main scanning recording is performed using the recording head, the density distribution in the main scanning direction is discriminated in advance, and, for example, when the dark portion is continuous, the density lower than the specified density is printed. For example, it is possible to make a predetermined correction for the operation of the recording head.

[0013]

EXAMPLES The outline of each example described in detail below is as follows.

In this embodiment, the reading unit scans the original in the main scanning direction and moves in the sub-scanning direction by the reading width, and a multi-head in which a plurality of image recording elements are arranged in a predetermined direction. In the image forming apparatus provided with the printing unit that performs image recording in synchronization with the reading unit, the next reading area is prescanned when the reading unit returns in the main scanning direction, and the image data obtained by this prescan According to the above, the density of the area is determined in advance, and the recording head is corrected in the next printing.

In other words, when the reading unit moves backward so as to return to the home position in the main scanning direction, the area to be printed next is pre-scanned to predict in advance the temperature change of the head due to the density of the original. By applying a correction corresponding to this to the head during printing, density unevenness during printing is removed.

Each embodiment will be described in detail below with reference to the drawings.

Embodiment 1 FIG. 1 is a block diagram showing a first embodiment of the present invention. In the figure, 10 is a reader unit for reading a document, and 12 is an inkjet printer unit. The printer unit 12 includes a density determination unit 13, a correction data memory 14, a pulse width control unit 15, and an inkjet recording head 16, the operation of which will be described later in detail.

FIG. 1 is a flow chart showing the operation of this embodiment.

Next, the operation of this embodiment will be described with reference to FIGS.

First, when the reading of a document is started in this embodiment, the CCD unit included in the reader unit 10 advances in the main scanning direction (step S1). next,
This CCD unit retreats on the same line, and at this time, the image density of the area to be read is read (step S2).

Next, the CCD unit is again advanced in the main scanning direction on the same line to read the image (step S).
3).

When the reading of the entire original is completed, the CCD unit is returned to the home position (step S5). On the other hand, if the reading of the original has not been completed, the CCD unit is moved forward in the sub-scanning direction and moved to the next reading position (step S6), and the CC is read again.
The image density is read by retracting the D unit (step S
2) Further, the process of advancing on the same line in the main scanning direction to read an image (step S3) is repeated.

The image data 11 thus read by the reader unit 10 is sent to the recording head 16 and printed when the CCD unit advances in the main scanning direction. On the other hand, when the CCD unit moves backward in the main scanning direction,
The read data 11 is sent to the density determination unit 13, and the determination result there is input to the correction data memory 14.

Next, referring to FIG. 3, the density determination unit 1
The operation of No. 3 will be described.

FIG. 3A shows a distribution of image density data read when the CCD unit is retracted. In this figure, as an example, there is shown a case in which a region of density d or higher continues over a length L ₃ from the main scanning position a to c. In the present embodiment, it is considered that when the image having the density d or more continues for L ₁ or more, the density unevenness occurs in the printing. Therefore, the position a
When the region of density d or more that started from ₁ continues for L ₁ or more,
The density determination unit 13 determines that the print density needs to be corrected.

The correction data memory 14 is shown in FIG.
As shown in, the correction data 0,
1, 2 are input. That is, 0 is input when no correction is necessary, and values such as 1 and 2 are input depending on the degree of correction. Specifically, when the density d or more continues for L ₂ or more, it is determined that larger correction is necessary, and the main scanning position b to
Enter the value of the correction data 2 for c. Also, the concentration d
When the above area disappears, the correction data is returned to 0, and the correction is unnecessary. In this way, the area to be read next is pre-scanned during the backward movement of the CCD unit, and the read data 11 is referenced to store the correction data for the read data in the correction data memory 14.

FIG. 3C shows the relationship between the pulse width to be applied to the recording head and the main scanning position during the next printing. That is, the print pulse width is changed as shown in the drawing in accordance with the correction data illustrated in FIG. Here, the print pulse width W ₀ is when there is no need for correction, and the pulse width becomes narrower according to the degree to be corrected in the order of W ₁ and W ₂ .

When the pulse width of the pulse applied to the recording head becomes narrower, the amount of ink ejected from the nozzle becomes smaller and the print density becomes thinner. Therefore, in the section from the main scanning direction a to b, by setting the pulse width to W ₁ , the concentration increase due to the temperature rise is offset by the concentration decrease due to the narrow pulse width, and as a result, , The image has no density change. Also in the section from the main scanning direction b to c, by setting the pulse width to W ₂ , it is possible to cancel the increase in density due to the increase in temperature.

FIG. 4 is an external perspective view of the printer section (inkjet printer) 12 shown in FIG.

In the figure, reference numeral 16 is an ink jet head (recording head) provided with a nozzle group for ejecting ink so as to face the recording surface of the recording sheet fed onto the platen 124. Reference numeral 116 denotes a carriage that holds the recording head 16, and is connected to a part of a drive belt 118 that transmits the driving force of the drive motor 117 and can slide with two guide shafts 119A and 119B that are arranged in parallel with each other. By doing so, the reciprocating movement of the recording head 16 over the entire width of the recording paper becomes possible. During this reciprocating movement, the recording head 16 records an image according to the read data 11 on the recording paper. The recording paper is conveyed by a predetermined amount each time the main scanning is completed, and the sub-scanning is performed.

Reference numeral 126 denotes a head recovery device, which is disposed at one end of the movement path of the recording head 16, for example, at a position facing the home position. The head recovery device 126 is operated by the driving force of the motor 122 via the transmission mechanism 123, and the recording head 16 is capped. In association with the capping part for the recording head 16 by the cap part 126A of the head recovery device 126, ink absorption (suction recovery) is performed by an appropriate suction means (for example, a suction pump) provided in the head recovery device 126, As a result, the ink is forcibly ejected from the ejection port, thereby performing the ejection recovery process such as removing the thickened ink in the ejection port. Further, the recording head is protected by capping at the end of recording. Such an ejection recovery process is performed when the power is turned on, when the recording head is replaced, or when the recording operation is not performed for a certain period of time.

Reference numeral 131 denotes a blade as a wiping member, which is disposed on the side surface of the head recovery device 126 and is made of silligon rubber. The blade 131 is held by the blade holding member 131A in a cantilever form, and like the head recovery device 126, the motor 122 and the transmission mechanism 123.
It becomes possible to engage with the ejection surface of the recording head 16 by the operation.

As a result, the head recovering device 1 is operated at an appropriate timing in the recording operation of the recording head 16.
After the ejection recovery process using 26, the blade 131 is projected into the moving path of the recording head 16 to wipe off dew condensation, wetting, dust or the like on the ejection surface of the recording head 16 in accordance with the movement operation of the recording head 16.

Embodiment 2 FIG. 5 shows a second embodiment of the present invention.

In the second embodiment, the print density is adjusted by controlling the temperature of the recording head 16. That is, the head temperature control unit 41 controls the cooling fan (for cooling) 43 and the heater (for heating) 44 according to the output from the thermocouple 42 and the storage data of the correction data memory 14.

The temperature of the recording head is controlled by the thermocouple 4.
If it is performed based on only the output of No. 2, as described as the problem of the conventional technique, it takes time from detecting the temperature change of the recording head 16 to applying the control, so that it is not possible to cope with the abrupt change. May not be. Therefore, as in the present embodiment, since the temperature change of the recording head during printing can be predicted in advance by the correction data stored in the correction data memory 14, for example, the cooling fan is rotated from immediately before the position where the temperature rise is expected. By doing so, it is possible to prevent temperature changes during printing.

Embodiment 3 FIG. 6 shows a third embodiment of the present invention.

In the third embodiment described here, the print density is adjusted by controlling the head drive voltage applied to the recording head 16. That is, the head voltage control unit 51 controls the head drive voltage supplied from the head power supply 52.

Then, by lowering the head drive voltage,
Since the ink ejection energy in the recording head is lowered, the ink ejection amount is reduced, and as a result, the print density is lowered.

In the present embodiment, the head driving voltage is lowered based on the correction data stored in the correction data memory 13, so that the change in print density due to the head temperature rise during printing can be offset.

In each of the above-described embodiments, when the reader unit (reading unit) scans the document in the main scanning direction and further moves in the sub-scanning direction to read the document and print with the inkjet multi-head, The next reading area is prescanned during the backward movement in the main scanning direction, based on the data of this prescan, the degree of head temperature rise due to the continuous high density portion during the next printing is determined and stored as correction data. Since the correction is performed so as to cancel the density change due to the temperature rise of the print head based on the correction data, it is possible to obtain a high-quality image without density unevenness.

In each of the above-mentioned embodiments, the recording head is reciprocated in the main scanning direction. However, when the CCD sensor is arranged over the width of the document in the main scanning direction, such reciprocation is unnecessary. Become.

In each of the above-described embodiments, the case where the ink jet printer is used as the printer has been described, but it goes without saying that the present invention can be applied to a thermal printer.

(Others) The present invention is particularly provided with means for generating heat energy as energy used for ejecting ink (for example, an electrothermal converter or a laser beam) even in the ink jet recording system. The present invention brings about excellent effects in a recording head and a recording apparatus of the type in which the state of ink is changed by the heat energy. This is because such a system can achieve high density recording and high definition recording.

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 is a so-called on-demand type,
It can be applied to any of the continuous type, but especially in the case of the on-demand type, it can be applied to the sheet holding the liquid (ink) or the electrothermal converter arranged corresponding to the liquid path. By applying at least one drive signal corresponding to the recording information and giving a rapid temperature rise exceeding nucleate boiling, heat energy is generated in the electrothermal converter, and film boiling is caused on the heat acting surface of the recording head. Liquid (ink) corresponding to this drive signal in a one-to-one correspondence
It is effective because bubbles can be formed inside. Due to the growth and contraction of the bubbles, the liquid (ink) is ejected through the ejection opening to form at least one droplet. It is more preferable to make this drive signal into a pulse shape, because the bubble growth and contraction are immediately and appropriately performed, so that the ejection of the 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, more 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-angle liquid passage) as disclosed in the above-mentioned specifications, US Pat. No. 4,558,333, US Pat. No. 4,558,333, which discloses a configuration in which a heat acting portion is arranged in a bending region.
The structure using the specification of No. 59600 is also included in the present invention. In addition, Japanese Unexamined Patent Publication No. 59-123670 discloses a configuration in which a common slit is used as a discharge portion of the electrothermal converter for a plurality of electrothermal converters, and an opening for absorbing a pressure wave of thermal energy is provided. The effect of the present invention is effective even if the configuration corresponding to the ejection portion is disclosed in JP-A-59-138461. That is, according to the present invention, recording can be surely and efficiently performed regardless of the form of the recording head.

Further, the present invention can be effectively applied to a full line type recording head having a length corresponding to the maximum width of a recording medium which can be recorded by the recording apparatus. Such a recording head may have a configuration that satisfies the length by a combination of a plurality of recording heads or a configuration as one recording head integrally formed.

In addition, even in the case of the serial type as in the above example, the recording head fixed to the main body of the apparatus or the ink jet from the main body of the apparatus is electrically connected to the main body of the apparatus by being mounted on the main body. The present invention is also effective when a replaceable chip-type recording head that can be supplied or a cartridge-type recording head in which an ink tank is integrally provided in the recording head itself is used.

Further, as the constitution of the recording apparatus of the present invention, it is preferable to add the ejection recovery means of the recording head, the preliminary auxiliary means and the like because the effects of the present invention can be further stabilized. Specifically, heating is performed by using a capping unit, a cleaning unit, a pressure or suction unit for the recording head, an electrothermal converter or a heating element other than this, or a combination thereof. Examples thereof include a preliminary heating unit for performing the discharge and a preliminary discharge unit for performing discharge different from the recording.

Regarding the type and number of recording heads mounted, for example, only one is provided corresponding to a single color ink, or a plurality of inks having different recording colors and densities are supported. A plurality of pieces may be provided. That is, for example, the recording mode of the recording apparatus is not limited to the recording mode of only the mainstream color such as black, but it may be either the recording head is integrally formed or a plurality of combinations may be used. The present invention is also extremely effective for an apparatus provided with at least one of full-color recording modes by color mixing.

In addition, in the above-described embodiments of the present invention, the ink is described as a liquid, but an ink that solidifies at room temperature or lower and that softens or liquefies at room temperature may be used. Or, in the inkjet system, it is common to control the temperature of the ink itself within the range of 30 ° C. or higher and 70 ° C. or lower to control the temperature so that the viscosity of the ink is within the stable ejection range. Sometimes, a liquid ink may be used. In addition, the temperature rise due to thermal energy is positively prevented by using it as the energy of the state change of the ink from the solid state to the liquid state, or in order to prevent the evaporation of the ink, it is solidified and heated in the standing state. You may use the ink liquefied by. In any case, by applying thermal energy such as ink that is liquefied by applying thermal energy according to the recording signal and liquid ink is ejected, or that begins to solidify when it reaches the recording medium. The present invention can be applied to the case where an ink having a property of being liquefied for the first time is used. In this case, the ink is
JP-A-54-56847 or JP-A-60-7
As described in Japanese Patent No. 1260, it may be configured to face the electrothermal converter in a state of being held as a liquid or a solid in the concave portion or the through hole of the porous sheet. 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, the ink jet recording apparatus of the present invention may be used as an image output terminal of an information processing apparatus such as a computer, a copying apparatus combined with a reader or the like, and a facsimile apparatus having a transmitting / receiving function. It may be a form or the like.

[0053]

As described above, according to the present invention, when visualizing recording in the main scanning direction, the density distribution in the main scanning direction is grasped in advance, and the drive state of the recording head is corrected based on the result. Since such a configuration is adopted, it is possible to form a high-quality image without color unevenness.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a flowchart showing a head driving procedure in each embodiment of the present invention.

FIG. 3 is an explanatory diagram showing the operation of the first embodiment.

FIG. 4 is an external perspective view of a printer unit according to each embodiment of the present invention.

FIG. 5 is a block diagram showing a second embodiment of the present invention.

FIG. 6 is a block diagram showing a third embodiment of the present invention.

FIG. 7 is a plan view showing a conventionally known image reading device.

FIG. 8 is a schematic configuration diagram showing a conventionally known inkjet type printing apparatus.

[Explanation of symbols]

 10 reader unit 11 read data 12 printer unit 13 density determination unit 14 correction data memory 15 pulse width control unit 16 recording head 40 printer unit 41 head temperature control unit 42 thermocouple 43 cooling fan 44 heater 50 printer unit 51 head voltage control unit 52 Head power supply 61 Sub-scanning rail 62 Document table 63 Main-scanning rail 64 CCD unit 65 Main-scanning home position 66 Sub-scanning home position 71 Recording paper 72 Ejection roller 73 Sub-scanning roller 74 Main scanning motor 75 Recording head unit 76 Platen section 77 Sub Scanning motor

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display location B41J 29/46 D 9113-2C 9012-2C B41J 3/04 104 F

Claims (3)

[Claims] 1. An image forming apparatus for visualizing an image on a recording material in a main scanning direction using a recording head, wherein the density in the main scanning direction is set before driving the recording head to perform the image forming apparatus. An image forming apparatus comprising: a determination unit that determines a distribution; and a correction unit that corrects a recording density of the recording head based on a determination result obtained from the determination unit. 2. The image reading unit according to claim 1, further comprising an image reading unit, before the reading unit reads the original in the main scanning direction.
An image forming apparatus, characterized in that an image in the main scanning direction is pre-scanned, and the density data obtained by the pre-scan is input to the determination unit. 3. The ink jet recording head according to claim 1, wherein the ink jet recording head causes film boiling in the ink as energy used for ejecting the ink. An image forming apparatus having an electrothermal converting element for generating thermal energy.