JPH0789069A - Ink jet printer - Google Patents

Abstract

PURPOSE:To perform printing of high quality by suppressing a wavy wrinkle occurring on a sheet. CONSTITUTION:The ink jet printer comprises a plurality of ribs 11, etc., disposed between a contact part of a leaf plate 7 for a feed roller 6 and an opposed part of a nose 4 of an ink jet head 3 for a sheet guide surface 8 and so arranged at an predetermined interval in a lateral direction of a sheet as to be interfered with a guide route 33.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet printer configured to press a sheet against a feed roller by a leaf plate and convey the sheet by rotating the feed roller.

[0002]

2. Description of the Related Art A conventional ink jet printer is shown in FIG.
As shown in, the carrier 2 having the inkjet head 3 is moved in the width direction of the paper P conveyed along the paper guide surface 8 by the paper feeding mechanism 5 while the ink is ejected from the nose portion 4 of the inkjet head 3. It is generally configured to eject and print.

The above-mentioned paper feed mechanism 5 is composed of a feed roller 6 which is rotationally driven by a motor (not shown), and a leaf plate 7 which presses the paper P against the feed roller 6.

More specifically, the feed roller 6 is divided into three parts in the direction orthogonal to the paper surface of FIG. 9 so as to save the material cost and to keep the friction surface with the paper P to the minimum necessary to reduce the load on the motor. It is said to have been constructed. Further, the leaf plate 7 is configured to press the paper P sent to the feed roller 6 by automatic paper feed or manual paper feed using a spring force or the like to the feed roller 6. Further, the leaf plate 7 is configured so that the flatness of the paper P can be secured by pushing the paper P against the paper guide surface 8.

Here, the paper guide surface 8 is shown in FIG.
As shown in FIG. The paper guide unit 21 is formed with a space 22 for disposing the feed roller 6 divided into three parts, and the space 22 penetrates into the area of the paper guide surface 8.

Therefore, the paper P sent to the paper guide surface 8 while being pressed against the feed roller 6 by the leaf plate 7 is driven by the ink ejected from the nose portion 4 of the ink jet head 3 which reciprocates in the width direction. After being printed, the paper is conveyed along the paper guide surface 8 and discharged to a paper discharge unit (not shown) on the downstream side.

[0007]

By the way, in the above-mentioned ink jet printer, the paper P is the leaf plate 7.
The sheet is pressed against the feed roller 6 by means of the pressing force, and continuous wrinkles are generated in the width direction of the sheet P by the pressing force, and as a result, the distance between the sheet P and the nose portion 4 of the inkjet head 3 is kept constant at the printing position. In some cases, the printing quality may deteriorate without being printed.

Further, in the ink jet printer having the structure in which the feed roller 6 is divided into a plurality (three) as described above, there is a place where the conveying force is applied to the paper P and a place where the conveying force is not applied, and such a force is applied. Wavy wrinkles may occur on the paper P depending on the difference in the condition.

Further, the wrinkles are also generated by the water content of the ink ejected from the ink jet head 3 and adhering to the printing surface of the paper P. In particular, when high-density printing is performed in which a large amount of ink is attached, a difference in expansion and contraction between the printing surface and the back surface of the paper P causes wavy wrinkles on the paper P.
Such wavy wrinkles spread to the surroundings and reach the printing position. Therefore, the print quality is impaired even by the wrinkle generated by the water content of the ink.

Here, FIG. 11 shows an example of wavy wrinkles caused by the various factors mentioned above. Due to the amplitude of such wrinkles, the nose portion 4 is different from the normal spacing between the surface of the paper P and the nose portion 4 of the inkjet head 3.
Will approach or separate from the surface of the paper P, which will cause deterioration of print quality. Such deterioration of print quality
For example, it occurs remarkably in the case of ruled line printing.

Further, when the positive portion of the wrinkle is extremely close to the nose portion 4 of the ink jet head 3, ink stains may even occur on the paper P. In particular, regarding the wavy wrinkles that occur on the paper P due to the water content of the ink, the higher the printing density of the paper P, the greater the amplitude thereof, resulting in the deterioration of the printing quality and the frequent ink stains on the paper P. .

Therefore, the inventor of the present application increases the pressing force of the leaf plate 7 or a paper guide surface portion (a portion shown by diagonal lines in FIG. 10) 8a facing the nose portion 4 of the ink jet head 3 during printing. I tried to secure the flatness of the paper by smoothing the paper with higher accuracy, but there was almost no effect.

In view of the above circumstances, it is an object of the present invention to provide an ink jet printer capable of reducing the amplitude of the wrinkle that occurs on the paper.

[0014]

SUMMARY OF THE INVENTION An ink jet printer according to the present invention includes a guide path for guiding a sheet from a paper feed direction to a paper discharge direction, a feed roller whose outer peripheral surface is in contact with the guide path, and the feed roller. A leaf plate that abuts on the guide path via a guide path, a flat paper guide surface that is disposed downstream of the contact portion between the feed roller and the leaf plate and forms a part of the guide path, and ejects ink. An inkjet head disposed so as to face the paper guide surface via a guide path, and a contact portion of the leaf plate with the feed roller and a nose portion of the inkjet head with respect to the paper guide surface. A plurality of protrusions located between the opposing portions and arranged at predetermined intervals in the width direction of the paper so as to interfere with the guide path. Characterized by providing.

[0015]

According to the present invention having the above-described structure, the sheet is pressed against the feed roller by the leaf plate, and the feed roller is rotationally driven in this state to convey the sheet along the guide path. In such a sheet conveying process, the sheet fed by the feed roller is guided by a flat sheet guide surface, and ink is ejected from the nose portion of the inkjet head onto the sheet in the middle of the guide to perform printing.

At this time, even if wavy wrinkles are continuously generated in the width direction of the paper due to the pressing force of the leaf plate, the water content of the attached ink, etc., the amplitude of the wavy wrinkles depends on the contact of the paper with the protrusions. Will be reduced.

That is, of the wrinkled wrinkles on the paper, the portion close to the protrusion is lifted by the protrusion,
In addition, the portions far from the protrusions are pushed downward toward the sheet guide surface by the troughs between the protrusions. As a result, the wrinkles on the paper are averaged and the amplitude thereof is greatly reduced. Therefore, at the printing position, the distance between the nose portion of the inkjet head and the paper becomes constant, so that the printing quality is improved.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIGS. 1 to 5, the inkjet printer of the present embodiment has the same basic configuration as that of the conventional example (FIGS. 9 and 10), but at least a region where the nose portion 4 of the inkjet head 3 moves. A plurality of protrusions (ribs 11, 12, 15 in this embodiment) are provided in the print area portion 8a of the paper guide surface 8 corresponding to the above and are spaced apart in the paper width direction and can reduce the amplitude of the wavy wrinkles generated on the paper. It has been configured.

Here, the print area portion 8a is a portion between the contact portion of the leaf plate 7 with the feed roller 6 and the facing portion of the nose portion 4 of the ink jet head 3 with respect to the paper guide surface 8. It includes a portion overlapping with the abutting portion and the facing portion. The same components as those in the conventional example (FIGS. 9 and 10) are designated by the same reference numerals, and the description thereof will be omitted or simplified.

First, as shown in FIG. 4, a paper feed tray 32 is provided in the main body case (31) of the present ink jet printer.
A substantially U-shaped guide path 33 is formed to connect the sheet discharge section 39 and the sheet discharge section 39. The paper P stored in the paper feed tray 32 is urged by the spring SP toward the feed roller 6.

In the present embodiment, the guide path 33 has a feed roller 6 for feeding and feeding the paper P stored in the paper feed tray 32, and a paper P having a paper guide surface 8 and fed by the feed roller 6. And a paper guide unit 21 that conveys the paper and discharges the paper to the paper discharge unit 39. As shown in FIG. 5, the paper guide unit 21 is detachably provided and has a paper discharge mechanism 34 on the downstream side of the guide path 33 with respect to the paper guide surface 8.

As shown in FIG. 4, the paper discharge mechanism 34 is composed of a paper discharge roller 35 and a biasing roller 36 which are arranged opposite to each other via a guide path 33. Further, as shown in FIGS. 2 and 4, the leaf plate 7 is arranged at a position where it does not hinder the reciprocating movement of the carrier 2 having the inkjet head 3 mounted thereon, and the spring 37 connected to the rear end thereof.
It is abutted against the feed roller 6 with a predetermined pressure by the urging force acting from.

Further, each rib 11 is arranged so that the wrinkle of the paper P is suppressed to a minimum amplitude in the print area portion 8a of the paper guide surface 8 along the paper width direction (the arrow Y direction in FIG. 1). It is arranged. More specifically, each rib 11 is 5.98 downstream from the leaf plate 7 in the guide path 33.
It is arranged such that the end portion is located at a position advanced by mm.

The upstream side portion 11a of each rib 11 is
As shown in FIG. 1, the paper P is chamfered at a predetermined angle (30 ° in this embodiment) with respect to the paper guide surface 8 so that the leading end of the paper P does not abut and the paper is fed smoothly. Therefore, this chamfered portion is the end of the rib 11.

Each rib 11 has a paper guide surface 8
Is set to a value that takes into consideration the head gap of the nose portion 4 of the inkjet head 3 and the thickness of the paper. Specifically, the height of each rib 11 is 1.35 mm.

The intervals E, F, G, between the ribs 11 are
H is E = 4.6 mm, F = 4.25 mm, G
= 4.54 mm and H = 4.75 mm. Further, the second rib 11 and the third rib 11 from both ends of the space 22 formed in the paper guide unit 21 are formed to be somewhat longer than the other ribs 11 in the conveyance direction of the paper P. There is.

Further, each rib 12 is disposed on the paper guide surface 8 portion corresponding to the feed roller 6, and in FIG. 1, the rib 12 on the left side and the rib 12 on the right side of the central portion are spaced by 7 mm. Are arranged at intervals of 9.1 mm.

Reference numeral 15 is an auxiliary rib, which is arranged at a position corresponding to both ends of the paper P fed by the feed roller 6. Particularly, in this embodiment, the surfaces of the ribs (11, 12, 15) are polished.

Next, the operation of this embodiment will be described.
The paper P moves in the length direction of each rib (11, 12, 15) while being supported by the plurality of ribs (11, 12, 15), and the nose of the inkjet head 3 with respect to the paper P. Ink is ejected from the section 4 to print.

At this time, as shown in FIG. 6A, due to the pressing force of the leaf plate 7 and the ink adhered to the print area, the print area 8a of the paper P including the ink adhered area (that is, the print area) is affected. Continuous wavy wrinkles occur in the width direction of the sheet P. On the other hand, as shown in FIG. 6B, the portion of the wrinkle that is close to the paper guide surface 8 is lifted by the plurality of ribs 11 and 12 and the auxiliary rib 15, and the portion that is far from the paper guide surface 8 is Each rib 11,1
The valley portion between the two promotes the depression toward the paper guide surface 8.

As a result, the wrinkles are averaged and the amplitude thereof is greatly reduced (at least by half compared with the prior art).

The rib 12 maintains a constant head gap between the nose portion 4 of the ink jet head 3 and the paper guide surface 8 at the printing position, and the rib 11
The effect of suppressing the wavy wrinkles is secured in the entire printing area.

The ribs 15 supporting both ends of the paper P maintain a constant head gap between the nose portion 4 of the ink jet head 3 and the paper guide surface 8 at both ends of the paper P at the printing position.

Further, the second rib 11 and the third rib 11 from both ends from the space portion 22 formed in the paper guide unit 21 have the paper P more than the other ribs 11.
It is formed to be somewhat longer in the transport direction. As a result, the bottom portion of the large wrinkle that is generated on the paper P due to the pressing force of the leaf plate 7 is supported, and the wrinkle amplitude is reduced more effectively. And, like this, the other ribs 11
The rib 11 formed longer than this also more effectively reduces the amplitude of the wavy wrinkles caused by the moisture of the ink attached to the paper P.

Here, the inventor of the present application made an experiment as to how the amplitude state of the wavy wrinkles on the paper P changes depending on the presence or absence of the ribs (11, 12, 15). In this experiment, a letter size sheet of Xerox-4024.201b was used as the sheet, and the head gap Gs between this sheet and the nose portion 4 of the inkjet head 3 was set.
Is set to 1 mm and the printing speed at the printing position is 67.73.
It was set to be mm / sec. As a result, FIG.
Experimental results as shown in (A), (B), (C), and (D) were obtained. In the figure, w is the paper width.

FIG. 8 is a graph in which the amplitude of the wavy wrinkles generated on the paper P is replaced by the voltage, and FIG. 8A shows high density printing by this ink jet printer, and one line from the printing position at this time. The figure which shows the measurement result in the position of the minute upstream side, (B) is high density printing with the former ink jet printer which does not have rib (11,12,15), 1 line from the printing position at this time The figure which shows the measurement result in the position of the upstream side, (C) the figure which shows the measurement result in the printing position when the paper is inserted in guide route (33) without printing with this ink jet printer, (D) 3A and 3B are views showing measurement results at the print position when the paper is inserted into the guide path 33 without printing with the conventional inkjet printer.

As clearly shown in these graphs,
In the conventional device, the amplitude of the wrinkle generated on the paper is large regardless of whether the paper is printed or not.
In particular, when printing is performed on a sheet of paper, wavy wrinkles with a larger amplitude are generated on the sheet of paper P as the head gap G is reduced to about 0.4 mm.

On the other hand, in the ink jet printer of the present invention, the amplitude of the wavy wrinkles on the paper is small, and the head gap G is almost within the normal Gs (= 1 mm) range.

However, according to this embodiment, at least the print area portion 8a of the paper guide surface 8 corresponding to the moving area of the ink jet head 3 is spaced apart in the paper width direction (Y direction), and Since a plurality of ribs (11, 12, 15) capable of reducing the amplitude of the wrinkle that occurs in P is provided, the amplitude of the wrinkle of the paper that has a great adverse effect on the next line during printing and after printing Can be significantly reduced. As a result, it is possible to improve the print quality.

Further, since the head gap (G) at the leading end of the paper P can be accurately secured by the ribs (11, 12, 15), high quality printing can be performed from the beginning of printing.

Further, since the tips of the ribs (11, 12) are inclined at 30 ° with respect to the sheet guide surface 8, the tips of the sheet P are caught by the ribs (11, 12). Can be effectively prevented, and smooth printing can be ensured.

Moreover, since the surface of each rib (11, 12, 15) has been polished, the paper P and each rib (11, 12, 15) are polished.
The frictional noise generated by the friction with (12, 15) is reduced, and the generation of printing noise can be prevented.

Further, the ribs (11, 12) and the auxiliary rib 15 are provided on the paper guide surface 8 of the paper guide unit 21.
Since it is formed integrally with the, the manufacturing is easy and the manufacturing cost is low.

Furthermore, since the feed roller 6 is divided into three, the material cost can be saved, and the feed roller 6 can be saved.
Since the friction surface between the sheet P and the sheet P is kept to the minimum necessary, the load on the motor is reduced.

[0045]

According to the present invention, the sheet of paper is positioned between the contact portion of the leaf plate with the feed roller and the portion of the nose portion of the ink jet head facing the paper guide surface and interferes with the guide path. Since the plurality of protrusions arranged at predetermined intervals in the width direction are provided, the amplitude of the wavy wrinkles generated on the paper on the paper guide surface can be greatly reduced. As a result, it is possible to print the paper with high quality without causing ink stains or print mismatch.

[Brief description of drawings]

FIG. 1 is a perspective view for explaining a main part of an embodiment of the present invention.

FIG. 2 is a side view for explaining a positional relationship among a feed roller, a leaf plate, an inkjet head, a paper guide surface, and a rib.

FIG. 3 is also a side view for enlarging FIG. 2 and explaining the positional relationship among the feed roller, the leaf plate, and the rib.

FIG. 4 is likewise a side view for explaining the overall configuration.

FIG. 5 is a perspective view showing a state in which the paper guide unit is removed.

FIG. 6 is a diagram showing an amplitude state of wavy wrinkles on a sheet of paper.

FIG. 7 is a diagram showing a wavy wrinkle state of a smoothed sheet.

FIG. 8 is a gap (head gap) between a nose portion of an inkjet head and a sheet in the present invention and a conventional example.
It is a figure which shows the experimental result which compared.

FIG. 9 is a side view for explaining a conventional configuration of an inkjet printer.

FIG. 10 is also a perspective view of the paper guide unit.

FIG. 11 is also a diagram showing an amplitude state of wavy wrinkles occurring on a sheet.

[Explanation of symbols]

 3 Inkjet head 4 Nose part 6 Feed roller 7 Leaf plate 8 Paper guide surface 11 Rib (projection part) 12 Rib (projection part) 15 Auxiliary rib (projection part) 33 Guide path

Claims (1)

[Claims] 1. A guide path for guiding a sheet from a paper feed direction to a paper discharge direction, a feed roller whose outer peripheral surface is in contact with the guide path, and a leaf plate which is in contact with the feed roller via the guide path. A flat paper guide surface that forms a part of the guide path and is provided on the downstream side of the contact path between the feed roller and the leaf plate, and a nose portion that ejects ink through the guide path on the paper guide surface. An inkjet head disposed so as to face each other, and is located between a contact portion of the leaf plate with the feed roller and a facing portion of a nose portion of the inkjet head with respect to the paper guide surface, and the guide. An inkjet printer comprising a plurality of protrusions arranged at predetermined intervals in the width direction of the paper so as to interfere with the path.