JP2005096223A - Inkjet printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet printer that does not require the monitoring of the position of a recording medium, and records good images entirely on the recording surface of the recording medium irrespective of whether the recording medium is astride transport roller pairs or is transported by one roller alone. <P>SOLUTION: The inkjet printer transports a recording medium P by the first transport roller pair 2 arranged on the upstream side of the transport direction of the recording medium P, a second transport roller pair 3 arranged on the downstream side of the transport direction and records an image on the recording medium by a recording head 1 arranged between the first transport roller pair 2 and the second transport roller pair 3. When the amount of transport of the recording medium P by the first transport roller pair 2 is A1, the amount of transport of the recording medium P by the second transport roller pair 3 is A2 and the minimum dot space in the resolution of an image recorded on the recording medium is D, the inkjet printer satisfies the relationship of A1+D/2>A2>A1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an ink jet printer, and more particularly, to an ink jet printer in which a recording medium is conveyed by a pair of conveying rollers disposed on the upstream side and the downstream side of the recording head.

  In an ink jet printer in which a recording medium is conveyed by a pair of conveying rollers disposed on the upstream side and the downstream side in the conveying direction with the recording head interposed therebetween, the recording medium between the conveying roller pair is used during image recording by the recording head. Therefore, the transport amount by the downstream transport roller pair is made larger than the transport amount by the upstream roller pair.

  In this case, if the trailing edge of the recording medium passes through the upstream conveying roller pair, the recording medium is conveyed by the downstream conveying roller pair alone. There is a problem that the image is significantly deteriorated due to the occurrence of overlapping or white spots.

  Therefore, conventionally, it is monitored whether the recording medium is applied to both the upstream-side conveyance roller pair and the downstream-side conveyance roller pair or only one of them is fed, and each conveyance roller is determined according to the result. A technique for controlling the conveyance amount of a pair is known (Patent Document 1).

However, in such a technique, in order to control the conveyance amount of each conveyance roller pair, it is necessary to constantly monitor the position of the recording medium, and a sensor and a complicated control mechanism for detecting the position of the recording medium are necessary. Thus, there has been a problem in that the printer is complicated and expensive.
Japanese Patent No. 3045755

  The present invention has been made in view of such conventional circumstances, and it is not necessary to monitor the position of the recording medium, and the recording medium is applied to both of the conveyance roller pairs or is sent by only one of them. It is an object of the present invention to provide an ink jet printer capable of recording a good image over the entire recording surface of a recording medium regardless of whether the recording medium is used.

  According to the first aspect of the present invention, the recording medium is conveyed by the first conveying roller pair disposed on the upstream side in the conveying direction of the recording medium and the second conveying roller pair disposed on the downstream side in the conveying direction. In an ink jet printer that records an image on a recording medium by a recording head disposed between the first conveying roller pair and the second conveying roller pair, the recording medium is conveyed by the first conveying roller pair. The relationship A1 + D / 2> A2> A1 is satisfied, where A1 is the amount, A2 is the conveyance amount of the recording medium by the second conveyance roller pair, and D is the minimum dot interval in the resolution of the image recorded on the recording medium. This is an ink jet printer.

  According to a second aspect of the present invention, there is provided the ink jet printer according to the first aspect, further comprising adjusting means for adjusting a conveying amount by applying a load to the driven rollers of the second conveying roller pair.

  According to a third aspect of the present invention, there is provided a drive source for each of the first transport roller pair and the second transport roller pair, and control for adjusting each transport amount by individually controlling each drive source. 2. The ink jet printer according to claim 1, further comprising means.

  According to the present invention, it is not necessary to monitor the position of the recording medium, and the recording of the recording medium can be performed regardless of whether the recording medium is applied to both the conveying roller pair or only one of them is fed. It is possible to provide an ink jet printer capable of recording a good image over the entire surface.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a side view showing a state of a recording unit of an ink jet printer, and FIG. 2 is a plan view thereof.

  In the figure, P is a recording medium, 1 is a recording head (not shown in FIG. 2), 2 is a first conveying roller pair, 3 is a second conveying roller pair, 4 is a drive motor, and 5 is driven. An encoder 6 provided on the drive shaft of the motor 4 is a sensor for detecting the encoder 5.

  The first conveying roller pair 2 includes a driving roller 21 that rotates when a driving force is transmitted from the driving motor 4 via the belt 7, and a driven roller 22 that contacts and is driven by the driving roller 21. The conveying roller pair 3 includes a driving roller 31 that rotates when a driving force is transmitted from the driving roller 21 of the first conveying roller pair 2 via the belt 8, and a driven roller that contacts and is driven by the driving roller 31. 32.

  Here, the recording medium P is an example of a sheet-shaped recording medium that has been cut into a predetermined size in advance, and the second conveying roller pair between the driving roller 21 and the driven roller 22 of the first conveying roller pair 2. By passing in the order between the three driving rollers 31 and the driven roller 32, the first conveying roller pair 2 and the second conveying roller pair 3 are driven to the left in the figure.

  The recording head 1 is mounted on a carriage (not shown), and can be reciprocated along a direction (main scanning direction) perpendicular to the drawing sheet orthogonal to the conveyance direction (sub-scanning direction) of the recording medium P by a movement mechanism (not shown). Yes. A large number of nozzles are arranged along the sub-scanning direction on the nozzle surface 1a of the recording head 1 facing the recording medium P. From each of these nozzles, the first conveying roller pair 2 and the second conveying are arranged. By ejecting ink toward the recording surface of the recording medium P positioned between the roller pair 3, a desired inkjet image is recorded in cooperation with the movement in the main scanning direction.

  Here, each conveyance amount when the recording medium P is conveyed by the first conveyance roller pair 2 and the second conveyance roller pair 3 is, for example, the outer diameter of the driving roller 31 of the second conveyance roller pair 3. The second conveying roller pair 3 is set to be larger than the first conveying roller pair 2 by making it larger than the outer diameter of the driving roller 21 of the first conveying roller pair 2 or the like. As a result, the recording medium P is moderately tensioned between the first conveying roller pair 2 and the second conveying roller pair 3, so that the recording surface at the time of image recording by the recording head 1 does not sag. It is designed to be kept smooth.

In the present invention, the recording medium P is recorded by the recording head 1 by A1 (mm) as the conveyance amount by the first conveyance roller pair 2 and A2 (mm) as the conveyance amount by the second conveyance roller pair 3 of the recording medium P. When the minimum dot interval in the resolution of the image is D (mm),
A1 + D / 2>A2> A1
It is characterized by satisfying the relationship.

  Here, the transport amounts A1 and A2 are transport amounts of the recording medium P when the recording medium P is transported independently by the first transport roller pair 2 or the second transport roller pair 3, respectively. Each of the first transport roller pair 2 and the second transport roller pair 3 has the same number of pulses as the recording width W of one main scanning of the recording head 1 along the sub-scanning direction of the recording medium P. This is the actual feed distance (unit: mm) of each recording medium P when driving is controlled.

 The minimum dot interval D is a minimum interval (unit: mm) between dots formed on the recording medium P by one ink droplet ejected at the resolution of the image recorded by the recording head 1.

  FIG. 4 shows the change in the dot landing position due to the change in the conveyance amount, and the image when the rear end of the recording medium is separated from the upstream conveyance roller pair and is conveyed only by the downstream conveyance roller pair. This shows the printing status of the joint.

  First, as shown in FIG. 4A, when the transport amount of the upstream transport roller pair and the transport amount of the downstream transport roller pair are exactly the same, the trailing edge of the recording medium is the upstream transport roller pair. Even if the image is conveyed by only the conveying roller pair on the downstream side away from the image, the joint of the image is not conspicuous. However, in this case, it is difficult to keep the recording surface smooth because the recording medium cannot be kept in tension between the upstream conveying roller pair and the downstream conveying roller pair.

  As shown in FIG. 4B, when the transport amount of the downstream transport roller pair is set to 3 / 4D larger than the transport amount of the upstream transport roller pair, the recording surface of the recording medium is strained. Although the state is maintained, the dot opening before and after the trailing edge of the recording medium is separated from the upstream conveying roller pair becomes a white stripe. For example, when the resolution is 720 DPI (the dot interval is 35 μm) and the dot diameter is 50 μm, the white stripe is 12 μm in width and becomes noticeable with the naked eye.

  On the other hand, as shown in FIG. 4C, when the conveyance amount of the downstream conveyance roller pair is set to be 1 / 2D larger than the conveyance amount of the upstream conveyance roller pair, the recording surface of the recording medium is strained. In addition to maintaining the state, the dot opening before and after the trailing edge of the recording medium moves away from the upstream conveying roller pair still appears as a white stripe. This white stripe has the same resolution and dot as described above, for example. In the case of the diameter, the width is about 2 μm and becomes so small that it cannot be confirmed with the naked eye.

  Accordingly, when the conveyance amount of the downstream conveyance roller pair is larger than the conveyance amount of the upstream conveyance roller pair, but is set smaller than 1 / 2D, the trailing edge of the recording medium is located on the upstream side. White stripes due to opening of dots before and after leaving the pair of conveying rollers are less noticeable.

  That is, when the transport amounts (A1) and (A2) satisfy the above relationship, the recording medium P is maintained in an appropriate tension state between the first transport roller pair 2 and the second transport roller pair 3. Thus, image recording by the recording head 1 can be performed, and the rear end of one recording medium P passes through the first conveying roller pair 2 so that the recording medium P is the second conveying roller pair 3 alone. Even if it is transported by the recording medium P, it is possible to record a good image without causing a situation such as illegal dot overlap or white streaking of the image over the entire recording surface of the recording medium P. can do.

  In addition, since it is not necessary to adjust and control the conveyance amount of each roller pair by detecting the position of the trailing edge of the recording medium P, it is not necessary to separately provide a means for detection and a means for adjustment control. The printer structure can be simplified and the cost can be reduced.

  The conveyance amount (A2) by the second conveyance roller pair 3 is sufficiently larger than the conveyance amount (A1) by the first roller pair 2, and specifically, it is set so that A2 ≧ A1 + D / 2. In this case, in this case, a load is applied to the driven roller 32 of the second transport roller pair 3 so that the transport amount (A2) is equal to the above formula with respect to the transport amount (A1) by the first transport roller pair 2. : It is preferable to have adjusting means for adjusting so as to satisfy A1 + D / 2> A2> A1, and FIGS. 1 and 2 show one mode in this case.

  The adjusting means here is constituted by a variable torque limiter 9 provided so as to contact the driven roller 32 of the second conveying roller pair 3. That is, the variable torque limiter 9 abuts on the driven roller 32 and applies a constant load thereto, so that the conveyance amount (A2) of the recording medium P by the second conveyance roller 3 becomes the first conveyance roller pair 2. Is adjusted so as to satisfy the relationship of the above formula: A1 + D / 2> A2> A1.

  In the above embodiment, both the first transport roller pair 2 and the second transport roller pair 3 are driven together by using one drive motor 4, but as shown in the schematic diagram of FIG. Each of the first conveyance roller pair 2 and the second conveyance roller pair 3 is provided with dedicated drive sources M1 and M2, and each drive source M1 and M2 is individually controlled to thereby each conveyance amount (A1). , (A2) is preferably provided with a control means 10 for adjusting the relationship of the above formula: A1 + D / 2> A2> A1. This control means 10 can be comprised by the controller which controls rotation of each drive source M1, M2, for example.

  Here, the recording medium P is exemplified as a sheet-like one, but the present invention is not limited to this, and the present invention is not limited to this, and a printer using a roll-shaped recording medium that is continuously fed out from the original winding wound in a roll shape. Is equally applicable.

Side view showing the recording section of an inkjet printer Plan view showing the state of the recording section of an inkjet printer Schematic which shows the mode of the recording part of the inkjet printer which concerns on other embodiment. The figure which shows the change of the landing position of the dot by the change of the conveyance amount

Explanation of symbols

P: recording medium 1: recording head 2: first conveying roller pair 21: driving roller 22: driven roller 3: second conveying roller pair 31: driving roller 32: driven roller 4: driving motor 5: encoder 6: sensor 7, 8: Belt 9: Variable torque limiter (adjustment means)
10: Control means M1, M2: Drive source

Claims (3)

The recording medium is conveyed by a first conveyance roller pair disposed on the upstream side in the conveyance direction of the recording medium and a second conveyance roller pair disposed on the downstream side in the conveyance direction, and the first conveyance roller pair And an ink jet printer for recording an image on a recording medium by a recording head disposed between the second conveying roller pair,
When the conveyance amount of the recording medium by the first conveyance roller pair is A1, the conveyance amount of the recording medium by the second conveyance roller pair is A2, and the minimum dot interval in the resolution of the image recorded on the recording medium is D,
A1 + D / 2>A2> A1
An inkjet printer characterized by satisfying the above relationship.   2. The ink jet printer according to claim 1, further comprising an adjusting unit configured to adjust a transport amount by applying a load to a driven roller of the second transport roller pair.   A drive source is provided for each of the first transport roller pair and the second transport roller pair, and control means for adjusting each transport amount by individually controlling each drive source is provided. The ink jet printer according to claim 1.

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