JPH04250044A - Ink jet recording device - Google Patents

Abstract

PURPOSE:To prevent image quality deterioration and contamination of a recording sheet by adjusting a gap between a recording medium and a recording head in a device to discharge ink, allowing an ink jet head to scan. CONSTITUTION:A mode selection switch 30 selects between the routine mode or the OHP mode. If the routine mode is set, a roller switching control part 31 selects a roller with a small diameter, and an image data control part 32 and a main system activation control part 33 records an image by performing a single subscan against a single scan on routine image data. On the other hand, if the OHP mode is selected, the main system activation control part 33 controls the action so that a single subscan is performed against two rounds of scan. Further, the image data control part 32 stores image data equal to a single scan in the routine mode in a buffer once and then converts the odd- order number image data to zero and outputs it during the initial scan, for example. Subsequently, the roller switching control part 31 selects a roller of large diameter.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus.

0002

2. Description of the Related Art Conventionally, inkjet recording apparatuses that eject ink from a head to record an image on paper are well known.

FIG. 2 is a perspective view of an image recording section of an inkjet recording apparatus, in which 4a and 4b are paper discharge rollers, 4c and 4
d is a paper feed roller, 5 is a platen, 6 is a recording head unit, 7a and 7b are paper presser guides, and 8 is a carriage.

[0004] The recording paper is fed by paper feed rollers 4c and 4d.
It is transported to the platen 5. At that time, the paper press roller 7a,
7b falls to the platen side and presses down the recording paper.

A recording head unit 6 is mounted on the carriage 8 . The recording head unit 6 is equipped with four recording heads each having 128 nozzles, each of which discharges cyan, magenta, yellow, and black ink.

The carriage 8 scans in the d direction (main scanning direction) along the rail 8a by a motor (not shown). While the carriage is scanning, four heads eject ink to form an image on recording paper on a platen. At this time, the rollers 9a and 9b perform scanning while rolling on the paper presser guide. The gap between the head and the recording paper is maintained by the roller diameter and the thickness of the guide.

[0007] When image recording in the main scanning direction is completed once,
The rollers 4c and 4d scan the recording paper by the width thereof in the sub-scanning direction substantially perpendicular to the main-scanning direction to record the next image.

[0008] When all image recording is completed,
The paper ejection rollers 4a and 4b eject the recording paper, and all operations are completed.

[0009]

[Problem to be Solved by the Invention] In such an inkjet recording device, after performing main scanning once to record an image, the main scan is performed again at the same location without moving the recording paper in the sub-scanning direction. In some cases, scanning is performed to record an image.

[0010] For example, when printing on OHP paper, if a large amount of ink is printed at once, the absorption of the ink may not keep up and the image may deteriorate. In this case, if you print with even-numbered nozzles among the multiple nozzles in the first main scan, and print with odd-numbered nozzles in the second main scan without performing sub-scanning, image deterioration will not occur. You can record without having to do anything.

However, in such cases, due to the insufficient absorption speed of the OHP paper, the ink ejected during the first printing may remain in a bulge on the surface of the OHP. If printing is performed for the second time in such a state, the surface of the head may come into contact with the raised ink, especially in inkjet recording methods that use heat to precisely position the distance between the paper and the recording medium. However, there was a problem in that the recording paper was stained.

Furthermore, in order to avoid this problem, if the gap between the paper and the head is designed to be wide in advance, when ordinary recording paper is used, the gap will become unnecessarily large, making it difficult to print high-definition images. It is difficult to record. Furthermore, if the gap is large, the precision with which the ink lands on the paper deteriorates, causing streaks in the image and deteriorating the image quality, which is a problem that needs to be solved.

[0013]

[Means for Solving the Problems] The present invention has been made in view of the above problems, and includes an inkjet recording apparatus that ejects ink from the inkjet head toward a recording medium while scanning the inkjet head. In a normal printing mode, an inkjet printing apparatus characterized by having means for adjusting the gap between the printing medium and the printing head according to differences in printing conditions performs multiple main scans without deteriorating the image quality. This is to prevent image stains.

[0014]

[Embodiment] Next, an embodiment will be explained with reference to the drawings. Figure 1
FIG. 1 is a block diagram of a first embodiment of the present invention. The mode selection switch 30 is a switch for selecting one of two modes: normal mode and OHP mode.

In the normal mode, the roller switching control section 31
A roller with a small diameter is selected, and the image data control section 32 and main body operation control section 33 record normal image data in an operation of one sub-scan for one main scan.

When the OHP mode is selected, the main body operation control section 33 controls the operation to perform two main scans and one sub-scan.

Further, the image data control section stores image data for one main scan in the normal mode in the buffer once, and then outputs the image data by replacing the odd numbered image data with zero during the first main scan. During the second main scan, even-numbered image data is replaced with zero and output.

As a result, in the first main scan, the even numbered nozzles are used to record an image, and in the second main scan, the odd numbered nozzles are used to record the image.

Furthermore, when the OHP mode is selected, the roller switching control section 31 switches the rollers of the carriage to ones with a larger diameter. FIG. 3 shows a roller mounting portion of the carriage, in which a small diameter roller 9 and a large diameter roller 34 are supported by a support plate 36. Normally, small diameter roller 9 is used, but in OHP mode,
The support plate 35 rotates 180 degrees around the shaft 36, and the large diameter rollers 34 are used.

[0020] In this way, in the OHP mode, when printing is performed in one sub-scan for two main scans, by changing the roller diameter, the gap between the OHP paper and the head can be made wider than during normal recording. This allows you to obtain clean, high-definition images.

(Other Embodiments) Next, a second embodiment will be explained.

In the first embodiment, the structure of the platen section was not particularly determined, but the second embodiment is an example in which the structure of the platen section is explained in FIG.

[0023] With the platen part configuration as shown in Fig. 2, the OH
When passing P paper, the OHP paper that has just been printed has not absorbed all the ink, so if the paper guide 7a is tilted after printing, the back side of the paper guide 7a will come into contact with the OHP surface, disturbing the image. There is a problem with this.

In this embodiment, a function is added to release the paper discharge side platen 7a in the direction of arrow b during the OHP mode. Although the block diagram is the same as the first embodiment, the main body operation control section can control one sub-scan for two main scans and release the platen 7a in the OHP mode.

The rest is the same as the first embodiment, and in the OHP mode, the rollers are switched to widen the gap between the OHP sheet and the head.

When it is necessary to release the paper discharge side guide 7a, there is a problem in that the OHP paper tends to float off the platen, and contact between the head and the ink on the OHP paper becomes even more likely to occur.However, the present invention solves the problem. Since the gap between the OHP sheet (recording medium) and the recording head can be widened by changing the rollers, recording can be performed with the guide 7a released, and the recording medium can be conveyed smoothly while maintaining high image quality. It can be performed.

Next, a third embodiment will be explained.

In the third embodiment, the present invention is applied to the case where reduced printing is performed on ordinary recording paper.

When performing simple reduction printing, for example, if the reduction ratio is set to 1/2, 128 pixels worth of input image data is reduced to 1/2.
The number is thinned out to /2, and printing is first performed using the upper half of 64 nozzles out of 128 nozzles. Then, the next 128 without sub-scanning.
The input image data for pixels is thinned out to 1/2, and the lower half is 6
After printing with 4 nozzles, sub-scanning for 128 nozzles is performed.

When such printing is performed, if the amount of ink printed by the 64 nozzles in the first upper half is large, the recording paper may cause what is called cockling, and may partially float off the platen.

In such a case, there is a high possibility that the head will come into contact with the paper and stain the image.

The present embodiment deals with such a case.

The block diagram of the third embodiment is also the same as that in FIG. 1, but the mode selection switch is for selecting between normal mode and reduced mode.

In the reduction mode, one scan per two main scans.
By performing sub-scanning operations twice, thinning out the image data, and switching the roller diameter of the carriage to a larger one, contact between the head and the paper is prevented.

As described above, the present invention is widely applicable to cases where one sub-scan is performed after a plurality of main scans, even if OHP paper is not necessarily used.

In the above embodiments, the OHP mode was selected using a switch, but it may also be automatically detected by detecting the reflectance of the recording paper.

[0037]Also, printing in the OHP mode was divided into printing with even-numbered nozzles and printing with odd-numbered nozzles, but it was not divided in this way, but simply one main print. It is also possible to print twice by reducing the amount of ink ejected during scanning to 1/2. (Others) Note that, in particular, in the inkjet recording method, the present invention includes a means (for example, an electrothermal converter, a laser beam, etc.) for generating thermal energy as the energy used for ejecting ink, and This provides excellent effects in recording heads and recording apparatuses that use energy to cause changes in the state of ink. This is because such a system can achieve higher recording density and higher definition.

For its typical configuration and principle, see, for example, US Pat. Nos. 4,723,129 and 4,740.
Preferably, it is carried out using the basic principles disclosed in the '796 specification. This method can be applied to both the so-called on-demand type and continuous type, but
In particular, in the case of the on-demand type, an electrothermal transducer is placed corresponding to the sheet holding the liquid (ink) or the liquid path, and the electrothermal transducer is placed at a temperature that rapidly exceeds nucleate boiling, corresponding to the recorded information. By applying at least one drive signal that provides a rise, the electrothermal transducer generates thermal energy that causes film boiling on the thermally active surface of the recording head, resulting in a liquid ( This is effective because it can form air bubbles within the ink. The growth and contraction of these bubbles causes the liquid (ink) to be ejected through the ejection opening.
Form at least one drop. It is more preferable to use this drive signal in a pulse form, since the growth and contraction of bubbles can be carried out immediately and appropriately, so that ejection of liquid (ink) with particularly excellent responsiveness can be achieved. This pulse-shaped drive signal is described in U.S. Pat. No. 4,463,359 and U.S. Pat.
262 is suitable. Further, if the conditions described in US Pat. No. 4,313,124 concerning the temperature increase rate of the heat acting surface are adopted, even more excellent recording can be achieved.

In addition to the configuration of the recording head, which is a combination of ejection ports, liquid paths, and electrothermal converters (straight liquid flow path or right-angled liquid flow path) as disclosed in the above-mentioned specifications, U.S. Pat. No. 4,558,333 and U.S. Pat. No. 4 disclose a configuration in which a heat acting part is arranged in a bending region.
A configuration using the specification of No. 459600 is also included in the present invention. In addition, Japanese Patent Application Laid-open No. 123670 of 1982 discloses a configuration in which a common slit is used as a discharge part for a plurality of electrothermal converters, and a hole that absorbs pressure waves of thermal energy is disclosed. The present invention is also effective as a configuration based on Japanese Patent Application Laid-Open No. 138461 of 1982, which discloses a configuration in which the discharge portion corresponds to the discharge portion.

Furthermore, a full-line type recording head having a length corresponding to the width of the maximum recording medium that can be recorded by the recording apparatus can be produced by combining a plurality of recording heads as disclosed in the above-mentioned specification. Either a configuration that satisfies the length or a configuration as a single recording head formed integrally may be used, but the present invention can more effectively exhibit the above-mentioned effects.

In addition, a replaceable chip-type recording head that is attached to the apparatus main body enables electrical connection with the apparatus main body and ink supply from the apparatus main body, or a print head that is integrated into the print head itself. The present invention is also effective when a cartridge type recording head is used.

Further, it is preferable to add recovery means, preliminary auxiliary means, etc. for the recording head, which are provided as a configuration of the recording apparatus of the present invention, because the effects of the present invention can be further stabilized. Specifically, these include capping means, cleaning means, pressure or suction means, preheating means for the recording head using an electrothermal transducer or another heating element, or a combination thereof. ,
It is also effective to perform a preliminary ejection mode in which ejection is performed separately from printing in order to perform stable printing.

Furthermore, the recording mode of the recording apparatus is not limited to a recording mode of only mainstream colors such as black, but may also include a recording head that is configured integrally or a combination of a plurality of recording heads, or multiple colors of different colors or The present invention is also extremely effective for devices equipped with at least one of the following: , full color by color mixing.

Although the embodiments of the present invention described above are explained using liquid ink, the present invention can be applied to ink that is solid at room temperature or ink that is soft at room temperature. Can be used. The above-mentioned inkjet device generally adjusts the temperature of the ink itself within the range of 30°C to 70°C to keep the viscosity of the ink within a stable ejection range. It is sufficient if the ink is liquid. In addition, the temperature rise caused by thermal energy can be actively prevented by using the energy to change the state of the ink from a solid state to a liquid state, or an ink that solidifies when left standing is used to prevent ink evaporation. In any case, the ink may be liquefied by application of thermal energy in accordance with the recording signal and ejected as liquid ink, or the ink may have already begun to solidify by the time it reaches the recording medium. The present invention is also applicable to the use of ink that is liquefied for the first time. In such a case, the ink is held in a liquid or solid state in the recesses or through holes of the porous sheet, as described in JP-A-54-56847 or JP-A-60-71260. It may also be in a form that faces the electrothermal converter. In the present invention, the most effective method for each of the above-mentioned inks is to implement the above-mentioned film boiling method.

[0045]

[Effects of the Invention] As explained above, by providing a means for adjusting the gap between the recording medium and the recording head depending on the recording conditions, multiple main scans can be performed in the normal mode without deteriorating the image quality. mode can now prevent image smudges.

[Brief explanation of the drawing]

[Fig. 1] Block diagram of an embodiment of the present invention

[Fig. 2] A perspective view of an image recording section of a conventional inkjet recording device.

[Fig. 3] Roller switching section according to the embodiment of the present invention

[Explanation of symbols]

4a, 4b Paper ejection roller 4c, 4d Paper feed roller 5 Platen 6 Head unit 7 Paper presser guide 8 Platen 30 Mode selection switch 31 Roller switching control section

Claims (1)

[Claims] 1. In an inkjet recording apparatus that discharges ink from an inkjet head toward a recording medium while scanning the inkjet head, means for adjusting the gap between the recording medium and the recording head in accordance with recording conditions. An inkjet recording device comprising: