JPH10147025A - Ink jet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet printer which is capable of printing data with a well-balanced lower margin and is free from the disorder of a printed image caused by the ejection of continuously printed matter. SOLUTION: A paper feed roller takes out recording papers P one by one on a paper feed tray and sends them to the downstream. The recording papers P are sent to a printing part B while being brought into contact under pressure with a platen 17 with a pressing roller 23. A printing head 16 is transferred back and forth in the main scan direction and at the same time, ejects an ink droplet to form (record) an image on the recording papers P. On the other hand, a pair of conveying rollers 15 convey the recording papers P intermittently, synchronized with the shuttle action of the printing head 16. A paper ejecting roller 25a sends the recording papers P downstream through a point contact by a serrated protrusion. A pair of second conveying rollers 27 are set at a standby position where ink dries and strongly hold the recording papers P which have no fear through drying that an image may be damaged. Further, the paired conveying rollers 27 convey the recording papers P whose rear ends are disengaged with the paired conveying rollers 15, keeping the papers P well poised and the printing heat 16 continues its printing action.

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, and more particularly, to an ink jet printer which performs printing with well-balanced upper and lower margins.

[0002]

2. Description of the Related Art Conventionally, in an ink jet type printer, the inks used are inconsistent in that they are difficult to dry so as not to cause clogging in a jet nozzle, and dry quickly after being attached to the paper surface. Properties are needed. However, it is difficult to obtain an ink satisfying such requirements.

[0003] After all, the first condition is to prevent clogging in the spray nozzle, so that the quick drying property after adhering to the paper surface has to be sacrificed. Due to the slow drying properties of this ink, inkjet printers use special recording paper with high internal porosity and good water absorption in order to prevent damage such as bleeding of the printed image on the paper surface by the discharge roll. A method has been adopted in which ink is quickly absorbed into the paper.

However, this method requires the use of special recording paper as described above, and thus cannot use plain paper. Since this raises the cost of use, in recent years, printed paper has been ejected using rollers with thin, fine, serrated protrusions on the peripheral surface to prevent bleeding even when the ink on the paper is not dry. Mechanisms have been devised and are widely used.

FIG. 3 is a side view showing the structure of a main part of such an ink jet printer. As shown in FIG. 1, in the ink jet printer, a print head 1 and a platen plate 2 are arranged to face each other. The print head 1
Slidably supported by the slide shaft 3, the injection nozzle portion 1
It moves in the direction perpendicular to the paper surface according to the print width while ejecting ink from a.

[0006] A transport roll pair including a transport roller 4a and a transport roller 4b is disposed upstream (rightward in the figure) of a printing section (printing area) where the injection nozzle section 1a and the platen plate 2 face each other. The paper 5 is carried into the printing unit by the roll pair. There is a distance A1 between the center 1b of the printing unit and the center 4c of the pair of transport rolls. The print head 1 is composed of an ejection nozzle and an ink cartridge, and has a considerable depth (in the horizontal direction in the figure). The distance A1 is
The distance is determined by the relationship between the structure of the print head 1 and the pair of transport rolls, and cannot be further reduced.

The paper 5 on which printing (image recording) is performed by the printing unit is provided with a toothed roller 6 provided with fine and thin serrated protrusions on the peripheral surface provided on the downstream side in the vicinity of the printing unit and the toothed roller 6. The paper is discharged out of the apparatus by a paper discharge mechanism including a pressing roller 7 opposed to the attaching roller 6.

[0008]

By the way, the pair of transport rolls composed of the transport roller 4a and the transport roller 4b has a strong force to pinch the paper 5 and has a sufficient transport force. However, in the paper discharging mechanism including the other toothed roller 6 and the pressing roller 7, since the peripheral surface of the toothed roller 6 has a saw-tooth shape, the portion that presses the paper 5 comes into point contact, and Since the paper 5 cannot be strongly pinched, it is impossible to give a sufficient transport force to the paper 5.

Therefore, if the trailing end of the sheet 5 comes out of the pair of transport rolls disposed upstream of the printing unit and the transport force of the pair of transport rolls is lost, the transport force for the sheet 5 can be reduced only by the transport force of the discharge mechanism. And the paper conveyance posture becomes unstable due to slippage or the like, and the paper conveyance speed and the conveyance direction axis fluctuate, thereby causing a problem that the recorded image is disturbed. Therefore, if an attempt is made to print the trailing edge of the sheet with a slight margin in the same manner as in the case of other printing apparatuses, the image quality cannot be guaranteed after the sheet is separated from the pair of transport rolls. For this reason, in many cases, printing is not performed in a portion where image disturbance occurs, that is, a trailing end portion of the sheet 5 corresponding to the distance A1 as an unrecorded area.

FIG. 4A is a diagram showing the printing state of paper by a conventional ink jet printer. As shown in FIG. 4A, the rear end 5-1 of the paper 5 corresponds to the distance A1 described above. A blank portion 5-2 having a length corresponding to the length is left. This margin 5
-2 is considerably longer than the margin A2 at the leading end, and the printable area 5-3 of the paper 5 is correspondingly smaller. That is, there is waste in using the paper. This not only contradicts the recent trend of energy saving, but also has a problem that the balance of the upper and lower margins is poor in appearance, and the overall appearance of the printed surface is impaired and dissatisfaction remains.

There is no problem with a handy type in which sheets are manually inserted one by one and picked up by hand each time a printed sheet comes out. In the case of a desk-top type that continuously provides printing and paper output by providing a paper output tray downstream of the paper output mechanism, the printed paper is deposited where the trailing end of the paper exits the paper press mechanism. Therefore, at this time, the trailing edge of the sheet has not been dried yet, so that the leading edge of the next sheet is in sliding contact with the undried portion of the trailing edge of the preceding sheet, causing a problem that the image is disturbed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional circumstances,
An object of the present invention is to provide an ink jet printer that can print on the trailing edge of a sheet with a sufficient margin and that the printed image is not disturbed even when continuous printing is performed.

[0013]

The construction of the ink jet printer of the present invention will be described below. The present invention provides a paper feed mechanism for feeding recording paper to a platen, and a paper feed mechanism provided with a serrated protrusion on a peripheral surface provided on the downstream side in the vicinity of a printing area of the platen to rotate the paper while pressing the paper against an opposing member. It is assumed that an ink jet printer has a discharge roller for discharging and prints an image on a recording paper by discharging ink from a print head.

The ink jet printer according to the present invention comprises a pressing means for pressing the recording paper fed by the paper feed mechanism against the platen, and a member for pressing the recording paper from the printing area of the platen to the image surface so as not to affect the image. A second paper feed mechanism disposed at a position where the ink dries.

[0015] The pressure contact means is composed of a plurality of rollers disposed at the tip of the support member, for example. The print head is connected to a carriage section of the print head. Also,
For example, the paper is pressed against the platen by electrostatic attraction.

The second paper feed mechanism is configured to convey the recording paper by attracting the recording paper to the back surface thereof, for example, as described in claim 5.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a side sectional view schematically showing the overall configuration of an ink jet printer according to an embodiment, and FIG. 2 is an enlarged view of a main part thereof. As shown in FIG. 1, the ink jet printer 10 includes a paper feed tray 12 on one side (right side in the figure) of a housing 11 in which a main body device is housed, and a paper discharge tray on the other opposite side. 13 is provided. A plurality of recording papers P are placed on the paper supply tray 12. Each time the paper feed roller 14 disposed near the paper feed end (attachment end) of the paper feed tray 12 makes one rotation, the uppermost sheet of recording paper P is taken out from the paper feed tray 12 and It is configured to be fed into.

The recording paper P fed by the paper feed roller 14 (hereinafter also referred to as FIG. 2) is transported by the transport roller 15a and the transport roller 1
The sheet is sent to the printing section B by a pair of conveying rollers 15 composed of 5b. In the printing section B, a print head unit 16 and a platen plate 17 are arranged to face each other. Print head unit 1
Reference numeral 6 includes an ejection nozzle portion and an ink tank portion, not particularly shown. The print head unit 16 is slidably held by a guide shaft 18, and is mainly driven by the power of the head drive motor 21 through a toothed belt 19 and a toothed pulley 22 fixed to the tip of the rotation shaft of the head drive motor 21. It is configured to reciprocate in the scanning direction (the width direction of the sheet, the direction perpendicular to the drawing).

A plurality of press-contact rollers 23 are provided on the upstream side of the printing section B on the conveying path of the recording paper P with a minimum distance D from the printing section B so as not to hinder the reciprocating movement of the print head unit 16.
Is arranged. Each of the press rollers 23 is held at the tip of a leaf spring 24 to form a press unit, and a plurality of sets are fixedly arranged on the frame 26 of the main unit alongside in the main scanning direction. These press-contact rollers 23 are provided in the printing section B.
Is pressed against the platen plate 17 to prevent the paper on the upstream side of the printing unit B from rising and fluttering, and to maintain the paper conveyance posture correctly.
Since the above-mentioned press-contact unit can be disposed by utilizing a narrow gap between the internal devices, the above-mentioned distance D is set at the center 16 of the printing unit.
The distance can be set to be extremely short as compared with the distance E between a and the center 15c of the transport roll pair 15. That is, FIG.
As shown by D in FIG. 4B, the margin 5'-2 at the rear end can be made extremely small as compared with A1 in FIG. 4A.

On the other hand, on the downstream side of the conveying path of the printing section B, the discharge roller 25a and the discharge roller 2 have a distance which does not hinder the reciprocation of the print head unit 16 from the printing section B.
5b is provided. The discharge roller 25a has a large number of thin, fine saw-toothed protrusions formed on the peripheral surface thereof, and the image contact surface of the printed recording paper P is pressed against the discharge roll 25b by the point contact of the sawtooth protrusions. Thus, the recording paper P is discharged backward (downstream side) with a small conveying force while holding the recording paper P in a conveying posture.

On the downstream side, a second transport roller 27a is provided.
And a second transport roller pair 27 composed of a second transport roller 27b and a second transport roller pair 27. The distance at which the ink dries to such an extent that the image is not affected even if there is something that presses from the printing unit B to the image surface of the recording paper P It is arranged at a position having F. The second transport roll pair 27 is configured to strongly hold the printed recording paper P and discharge it onto the paper discharge tray 13.
The distance F is set by changing the drying time based on the characteristics of the ink used and the feed amount of the recording paper P.

In the above configuration, the operation is again shown in FIG.
This will be described with reference to FIG. First, the paper feed roller 14 takes out the uppermost sheet of the recording paper P on the paper feed tray 12 and feeds it to the downstream of the transport path. The pressing roller 23 is provided on the recording paper P
Is pressed against the platen plate 17. The recording paper P is sent to the printing unit B while being pressed against the platen plate 17. When the recording paper P reaches the printing section B, the print head unit 16
Reciprocates in the main scanning direction, ejects ink droplets from the ejection nozzles in accordance with the print data, and forms (records) an image on the recording paper P.

When the print head unit 16 moves 1 in the main scanning direction.
During the reciprocating movement, the transport roll pair 15 stops to hold the recording paper P, and when the print head unit 16 returns to the printing reference position, the transport roll pair 15 rotates by a predetermined amount to rotate the recording paper P. In the sub-scanning direction (conveying direction). By repeating this operation, an image is formed on the recording paper P.

In general, inks used in the ink jet system are water-soluble and do not dry quickly. Therefore, when the printed image portion of the recording paper P reaches the paper discharge mechanism 25, the image formed on the paper surface is in an unfixed state. In order to prevent the unfixed image from being damaged, the paper discharge mechanism 25 pinches the recording paper P by point contact with a large number of serrated protrusions of the paper discharge roller 25a and sends the recording paper P downstream of the conveyance path with a weak conveyance force. I do.

On the downstream side, the second transport roll pair 27, which is waiting at a position where the ink just dries, strongly presses the recording paper P which has no risk of damaging the printed image due to the drying of the ink. It is transported while pinched.

After the printing on the recording paper P progresses and the rear end of the recording paper P is disengaged from the nipping of the pair of transport rolls 15, the above-mentioned pressing roller 23 presses the rear end of the recording paper P against the platen plate 17. And the second conveying roll pair 27 moves the recording paper P at the correct speed at a correct speed against the resistance force caused by the pressure of the pressure roller 9. Inherit transport and discharge.

As a result, the recording paper P is continuously carried out while maintaining the correct conveyance posture and the conveyance speed. On the other hand, the print head unit 16 moves the recording paper P until the rear end of the recording paper P is released from the pressure contact of the pressure roller 9. Continue printing on the trailing edge. The recording paper P on which the image has been formed in this manner is discharged to the paper discharge tray 13, whereby a series of printing operations is completed. As a result, the lower margin of the recording paper P is shortened corresponding to the distance D, for example, as shown in a margin 5'-2 shown in FIG. 4, and forms a balanced margin as a whole. At the same time, no disturbance occurs in the image near the lower margin.

In the above-described embodiment, the recording paper P is pressed against the platen plate by the pressure roller. However, the present invention is not limited to this. For example, the platen plate may be formed of a conductive material and an appropriate power supply may be used. And apply a bias voltage,
The recording paper may be brought into close contact with the platen plate by electrostatic attraction. Further, in the above-described embodiment, the plurality of pressure-contact rollers are fixedly arranged on the frame. However, the present invention is not limited to this, and is formed in a spherical shape and attached to the tip of a leaf spring in a state like a ballpoint pen. Alternatively, a unit including at least one pressure roller may be attached to the carriage of the print head unit. Also, the second
The recording paper is held between the pair of conveyance rolls 27, and the conveyance is taken over. However, an appropriate power supply is connected to the second conveyance roller, a bias voltage is applied, and the conveyance of the recording paper is continued by electrostatic attraction. You may.

[0029]

As described above in detail, according to the present invention, the second conveying mechanism having the pressing force on the platen portion and having the conveying force at a position where the printed image in the sheet discharging direction is not disturbed is provided. Since it is provided, even after the trailing edge of the paper comes out of the pair of transport rolls on the paper feed side, it is possible to suppress the lifting and fluttering of the trailing edge of the paper and to maintain the transporting force for the paper, whereby By leaving a narrow margin at the end, it is possible to print sufficiently using the paper surface and without disturbing the image, thus contributing to energy saving without wasting paper usage and realizing a visually uniform paper configuration. The aesthetic appearance is improved as a whole without disturbing the image.

Further, since the transporting posture of the paper does not change even after the trailing edge of the paper comes out of the pair of transporting rolls on the paper feeding side, the same accuracy as the leading edge can be obtained up to the portion where the printing which cannot guarantee the image quality is forcibly performed. This makes it possible to print an image, so that good image quality is always obtained irrespective of how margins are taken, thereby eliminating user dissatisfaction.

[Brief description of the drawings]

FIG. 1 is a side sectional view schematically showing an overall configuration of an ink jet printer according to an embodiment.

FIG. 2 is an enlarged view of a main part of the inkjet printer according to one embodiment.

FIG. 3 is a side view showing a configuration of a main part of a conventional ink jet printer.

FIG. 4A is a printing state diagram of paper by a conventional ink jet printer, and FIG. 4B is a printing state diagram of paper by a printing apparatus of the present invention.

[Description of Signs] 1 Print head 1a Injection nozzle portion 1b Center of printing area 2 Platen plate 3 Slide shaft 4a Transport roller 4b Transport roller 4c Center of transport roll pair 5, 5 'Paper 6 Toothed roller 7 Pressing roller 5-1 5-2, 5'-2 Margin of paper 5-3 Printable area 10 Inkjet printer 11 Housing 12 Paper feed tray 13 Paper discharge tray 14 Paper feed roller 15 Transport roll pair Reference Signs List 16 print head unit 17 platen plate 18 guide shaft 19 toothed belt 21 head drive motor 22 toothed pulley 23 pressure roller 24 leaf spring 25 paper discharge mechanism 25a paper discharge roller 25b paper discharge roller 27 transport roller pair 27a second transport roller 27b Second transport roller

Claims (5)

[Claims] A paper feed mechanism for feeding recording paper to a platen;
A discharge roller that is provided on the downstream side in the vicinity of the printing area of the platen and has a serrated protrusion on the peripheral surface and that discharges the paper while rotating the paper while pressing the paper against an opposing member; In an ink jet printer that discharges and records an image on a recording sheet, a pressing unit that presses the recording sheet sent by the paper feed mechanism against a platen, and a member that presses the printing surface of the platen to an image surface affects the image. An ink jet printer comprising: a second paper feed mechanism disposed at a position where the ink is dried to such an extent that the ink is not dried. 2. The ink jet printer according to claim 1, wherein said pressing means comprises a plurality of rollers disposed at a tip of a support member. 3. An ink jet printer according to claim 2, wherein said press contact means is connected to a carriage of said print head. 4. The ink jet printer according to claim 1, wherein said pressing means presses the sheet against a platen by electrostatic attraction. 5. The ink jet printer according to claim 1, wherein the second paper feed mechanism conveys the recording paper by attracting the recording paper to a back surface thereof.