JP2001080804A - Recording medium carrying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a change in the carrying speed of a recording medium just under a printing member without increasing contact pressure of a spur roller even when inverse directional force of the carrying direction acts on the recording medium by rotating the spur roller only in the carrying direction of the recording medium. SOLUTION: A spur roller 1 is formed by projecting contact teeth 11 in a radial shape on the outer periphery, and plural spur rollers 1 are arranged at prescribed intervals on a shaft 12 of a two-layer structure. A one-way clutch for setting the shaft rotating direction only in one direction is arranged on a movable shaft 122, the movable shaft 122 can rotate in the carrying direction of a recording medium P, and cannot rotate in the inverse direction to thereby restrain the degradation of a printing grade by a fluctuation in the carrying speed of the recording medium P just under a printing member 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image,
The present invention relates to a recording device for recording characters and the like and a recording medium transport device for transporting a recording medium printed by the recording device.

[0002]

2. Description of the Related Art FIG. 6 shows an example of a conventional recording medium conveying device.

The printing member 6 is, for example, an ink jet head having a plurality of nozzles formed thereon. By performing scanning in the width direction of the recording medium P, printing in the main scanning direction is formed. The recording medium P is conveyed in the sub-scanning direction (conveying direction) by the conveying roller 2 disposed downstream of the printing member 6.

[0006] This recording medium conveying apparatus uses a conveying roller 2 as a means for conveying a printed recording medium P, and the conveying roller 2 is driven by a driving means such as a motor (not shown). Further, a spur roller 1 for nipping the recording medium P with the transport roller 2 is disposed at a position facing the transport roller 2.

The spur roller 1 is rotatably supported in both forward and reverse directions, and is driven to rotate clockwise in FIG. 6 by friction with the transport roller 2 or friction between the recording medium P and the roller.

FIG. 7 shows the structure of a spur roller.
The spur roller 1 has a plurality of contact teeth 11 radially protruding from the outer periphery thereof, and a plurality of spur rollers 1 are provided on the shaft 12 at predetermined intervals. The configuration of the spur roller 1 in this manner is such that, when an ink jet head is used as the printing member 6, even if the ink formed on the recording medium P is not dried, the spur roller 1 is arranged on the printing surface of the recording medium P. This is to enable the recording medium P to be held between the conveyance roller 2 and the recording medium P in contact with the recording medium P.

The recording medium P sent from the upstream side (right side in the drawing) is sandwiched between the conveying roller 2 and the spur roller 1 while using the frictional force acting between the conveying roller 2 and the recording medium P as shown in FIG. Is transported in the transport direction indicated by the arrow.

By using such a recording medium transport device,
Even when the ink printed on the recording medium P is not sufficiently dried, the printing surface and the spur roller 1 are in point contact with each other, so that the recording medium P can be conveyed without soiling the printing surface.

However, when the second transport roller 3 used for transporting the recording medium P is located downstream of the transport roller 2 in the transport direction, the transport speed of the recording medium P is affected by the second transport roller 3. There is a disadvantage that.

In the following, the relationship between the transport speed of the second transport roller 3 and the transport speed of the transport roller 2 is as follows: (transport speed of the second transport roller 3) = (transport speed of the transport roller 2) -a ( a> 0) In the state, the transport speed of the recording medium P is easily affected by the transport speed of the second transport roller 3 having a strong pressing force.

That is, until the recording medium P is held between the second conveying roller 3 and the pressure roller 4, the spur roller 1 is driven by the driving of the conveying roller 2 in the clockwise direction in FIG. .

However, when the recording medium P is sandwiched between the second conveying roller 3 and the pressure roller 4, as shown in FIG. The force returned in the opposite direction comes to work.

At this time, since the spur roller 1 is configured to be rotatable in both the clockwise direction and the counterclockwise direction, the recording medium P is moved in the conveying direction at the contact position between the spur roller 1 and the conveying roller 2. When the spur roller 1 moves in the opposite direction, a force is generated in the spur roller 1 to rotate in the counterclockwise direction due to the frictional force with the recording medium P. As a result, as soon as the recording medium P reaches the second conveying roller 3, the contact position between the conveying roller 2 and the spur roller 1 and the conveying speed of the recording medium P upstream from the contact position change. . For this reason, there is a problem that the print quality is deteriorated in the sub-scanning direction.

Therefore, as a recording medium conveying device for solving such a problem, the recording medium P is provided with a pinching force larger than that of the second conveying roller 3 by the conveying roller 2 so that the second conveying roller 3 There has been proposed a recording medium transport device which is not affected by the above.

The specific transport procedure of this recording medium transport apparatus will be described with reference to FIG.

Recording medium P printed by printing member 6
Is transported by the transport rollers 2 to the downstream side in the transport direction.
At a position where the recording medium P is sufficiently dried on the downstream side, there is a second conveyance roller 3 for conveying the recording medium P further downstream. The transport roller 3 is driven by driving means (not shown). Alternatively, it is also possible to use a driving means for driving the transport roller 2 and connect the transport roller 2 and the second transport roller 3 with a plurality of gears or the like. Thus, the two transport rollers 2 and 3 can be driven by a single driving unit.

The transport roller 2 and the second transport roller 3 are
Both are made of rubber material. At a position opposing the second transport roller 3, there is a pressure roller 4 made of resin.
The transporting force of the second transporting roller 3 is large enough to transport the recording medium P along the upward guide 5 as shown.

When the recording medium P is conveyed while being sandwiched between the second conveying rollers 3, the conveying speed of the recording medium P immediately below the printing member 6 is affected by the conveying speed of the paper feed roller 7.

For example, when the relationship (transport speed of the second transport roller 3) = (transport speed of the transport roller 2) −a (a> 0) is satisfied, (recording medium passing through the second transport roller 3) Transfer speed) =
(Transport speed when only the transport roller 2 passes) -b (0 <b <
a) It is possible that

In this case, the value of b can be made close to 0 by increasing the contact pressure of the spur roller 1 at a position facing the transport roller 2 with the transport roller 2 and increasing the clamping force of the recording medium P. is there. As a result, it is possible to reduce unevenness in the conveyance speed of the recording medium immediately below the printing member, and perform printing on the recording medium P with little image displacement.

[0021]

However, when a sufficient contact pressure is applied to the spur roller 1 to pinch the recording medium P, the contact teeth 11 arranged on the spur roller 1 pierce the recording medium P deeply. Therefore, there is a problem that traces of the contact teeth 11 remain on the recording medium P and the print quality of the recording medium P deteriorates.

On the other hand, for the purpose of improving the recording speed of the image forming apparatus, there is a method in which the transport speed of the recording medium P at the time of ejection is faster than the transport speed before ejection at the time of printing or the like. It is disclosed in 198,099.

However, as in the above method, the second
The transport speed of the transport roller 3 is set to be higher than the transport speed of the transport roller 2, that is, (the transport speed of the second transport roller 3) = (the transport speed of the transport roller 2) + a (a> 0). When the speed of each transport roller is set to, the transport speed of the recording medium P during printing is governed by the transport speed of the second transport roller 3 and its accuracy.
There has been a problem that high-quality image formation cannot be performed.

[0024]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has a conveying roller which is driven to rotate, and contact teeth protruding radially on the outer periphery. And a spur roller disposed so as to be pressed against the transport roller.With the rotation of the transport roller, the recording medium is sandwiched between the transport roller and the spur roller, and recording is performed by the frictional force between the transport roller and the recording medium. In a recording medium transport apparatus that transports a medium downstream, the spur roller is configured to be rotatable only in the recording medium transport direction.

Therefore, according to the recording medium conveying apparatus of the present invention, even if the recording medium tries to move in the direction opposite to the conveying direction, the spur roller holding the recording medium does not rotate in the direction opposite to the conveying direction. The medium will travel only in the transport direction. As a result, it is possible to reduce unevenness in the conveyance speed of the recording medium immediately below the printing member without increasing the contact pressure of the spur roller.

As a specific means for rotating the spur roller only in the recording medium conveying direction, a one-way clutch is used.

Further, as a specific means for allowing the spur roller to rotate only in the recording medium conveying direction, the spur roller is configured so that a pawl can be engaged with at least one gear provided on the shaft of the spur roller. .

[0028]

Embodiments of the present invention will be described below with reference to the drawings. Note that members having the same functions as those of the above-described conventional recording medium conveyance device are denoted by the same reference numerals.

FIG. 1 is a schematic diagram in the case where the recording medium transport device of the present invention is applied to, for example, an ink jet printer.

It should be noted that the recording medium conveying apparatus of the present invention is not limited to an ink jet printer, but can be applied to other types of image forming apparatuses such as a printing apparatus using a liquid toner.

As shown in FIG. 2, the spur roller 1 has contact teeth 11 protruding radially on the outer periphery thereof, and a plurality of spur rollers 1 are provided at predetermined intervals on a shaft 12 having a two-layer structure. ing.

As shown in FIG. 3, the shaft 12 is composed of a fixed shaft 121 at the center indicated by a hatched portion and a movable shaft 122 slidably fitted on the outer periphery of the fixed shaft 121. I have. Each spur roller 1 is connected to the movable shaft 122.
, And each spur roller 1 is also rotatable with the rotation of the movable shaft 122.

As shown in FIG. 2, the movable shaft 122 is provided with a one-way clutch 13 for rotating the shaft only in one direction. This one-way clutch 13
Accordingly, the movable shaft 122 can rotate in the transport direction of the recording medium P (the direction of the arrow in FIGS. 1 and 3), but cannot rotate in the opposite direction, and is provided on the movable shaft 122. Each spur roller 1 is similarly constructed.

A second transport roller 3 is provided on the downstream side in the transport direction. Assuming that the surface of the printed recording medium P is sufficiently dry at the position of the second transport roller, the recording medium P is transported by the pressure roller 4 along the upward guide 5.

The pressure roller 4 is made of a resin material.
It has a sufficient pressure force to convey the recording medium P along the guide 5. Here, it is desirable that the transport speed of the second transport roller 3 be set lower than that of the transport roller 2.

The printing member 6 is of a serial type composed of a plurality of nozzles, and is configured to move in the width direction of the recording medium P (generally, this direction is referred to as a main scanning direction) by conveying means (not shown). And enables wide printing at a time. The printing member 6 is configured to perform desired recording on the recording medium P with ink. The printing member 6 may be composed of only a monochrome cartridge containing black ink, or may be composed of a color cartridge containing a plurality of color inks such as yellow, magenta, and cyan in addition to the monochrome cartridge. Good. The color cartridge may be an integrated type, or may be an independent divided type for each color.

Next, a description will be given of an image forming process by an ink jet printer to which the recording medium conveying apparatus of the present invention configured as described above is applied.

The recording medium P printed by the printing member 6 is
The sheet is conveyed to the downstream side in the conveying direction by the conveying roller 2. When the recording medium P is transported to the second transport roller 3, the recording medium P is transported upward along the guide 5 by the pressure force of the second transport roller 3, and discharged with the print surface facing downward. You. With the print surface facing downward, the recording media P are arranged in the order in which they were printed.

Here, in the above-described conventional recording medium transport apparatus, the spur roller 1 has a structure capable of rotating in both the clockwise direction and the counterclockwise direction. When the recording medium P
Is returned in the reverse direction of the transport direction, resulting in deterioration of print quality.

However, in the present embodiment,
Since the spur roller 1 cannot rotate in the reverse direction of the transport direction, even if the recording medium P is in the state shown in FIG. It will not be returned. Therefore, it is possible to suppress the deterioration of the print quality due to the variation in the transport speed of the recording medium P immediately below the printing member 6.

At this time, the contact pressure of the spur roller 1 with respect to the transport roller 2 may be such that it has a sufficient clamping force to transport the recording medium P to the second transport roller 3, and is determined for each condition. . That is, the pinching force is determined by the difference between the conveyance speed a between the second conveyance roller 3 and the conveyance roller 2, the specifications of the recording medium conveyance device such as the distance between the two, the type of the recording medium
This is because it may vary depending on the specifications of the recording medium P such as mechanical strength and the frictional force between the transport roller 2 and the recording medium P.

In the apparatus disclosed in Japanese Patent Application Laid-Open No. Hei 10-198099, which is exemplified as a conventional recording medium conveying apparatus, the recording medium P is conveyed by the conveying roller 2 and the spur roller 1.
Is set to be larger than the holding force of the second conveyance roller 3 and the pressure roller 4, but in the recording medium conveyance device of the present invention, it is not necessary to satisfy such a relationship between the two. Absent. Furthermore, in the present invention, in order to prevent the contact teeth 11 from sticking onto the recording medium P and to reliably discharge the recording medium P, the recording medium P is conveyed by the transport roller 2 and the spur roller 1.
Is preferably set smaller than the holding force of the second transport roller 3 and the pressure roller 4.

For example, if there is a relationship of (transport speed of second transport roller 3) = (transport speed of transport roller 2) -a (a> 0), second transport roller 3 and pressure roller 4
Thus, the force for nipping the recording medium P may be set to be larger than the force for nipping the conveyance roller 2 and the spur roller 1.

FIGS. 4 and 5 are views for explaining another embodiment of the recording medium conveying apparatus of the present invention.

In this embodiment, similarly to the embodiment shown in FIG. 1, after the recording medium P conveyed by the conveyance roller 2 arrives at the second conveyance roller 3, it is conveyed along the guide 5. Is done.

A different point from the embodiment shown in FIG. 1 is that the shaft 12 comprises only the movable shaft 122 and serves as a rotation direction regulating member for the movable shaft 122 of the spur roller 1 as shown in FIG.
Instead of a one-way clutch, a gear 14 fixed to a movable shaft 122 and a pawl 15 that can be locked to each tooth of the gear 14 in order to restrict the rotation of the gear 14 in the reverse direction in the transport direction are used. is there. Therefore, the spur roller 1 provided on the shaft 12 can be rotated only in the transport direction of the recording medium P.

The relationship between the transport speed of the second transport roller 3 and the transport speed of the transport roller 2 is as follows: (transport speed of the second transport roller 3) = (transport speed of the transport roller 2) −a (a> 0) At some point, the transport speed of the recording medium P is easily affected by the transport speed of the second transport roller 3 having a strong pressure. As a result, the transport speed may change as soon as the recording medium P arrives at the second transport roller 3. However, since the spur roller 1 cannot be rotated in the reverse direction of the transport direction by the gear 14 and the pawl 15, the recording medium P is not returned to the reverse direction of the transport direction immediately below the printing member 6. As a result, also in this embodiment, the same effect as in the above-described embodiment can be obtained.

[0048]

As described above, according to the recording medium conveying apparatus of the present invention, the spur roller can be rotated only in the conveying direction of the recording medium, so that the force in the direction opposite to the conveying direction acts on the recording medium. In this case, it is possible to reduce the variation in the conveyance speed of the recording medium immediately below the printing member without increasing the contact pressure of the spur roller, and it is possible to suppress the deterioration of the printing quality.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of a recording medium transport device according to the present invention applied to an ink jet printer.

FIG. 2 is a perspective view showing a configuration of a spur roller and a one-way clutch.

FIG. 3 is a diagram illustrating a configuration of a shaft provided with a spur roller and a rotation direction of the spur roller.

FIG. 4 is a perspective view for explaining another embodiment of the recording medium transport device of the present invention.

FIG. 5 is a diagram showing a configuration of a gear and a pawl, and a rotation direction of the gear.

FIG. 6 is a schematic diagram showing a configuration of a conventional recording medium transport device.

FIG. 7 is a perspective view showing a conventional spur roller whose rotation direction is not regulated.

FIG. 8 is a diagram illustrating a state of the recording medium when the recording medium reaches a second conveyance roller.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Spur roller 11 Contact tooth 12 axis 121 Fixed axis 122 Movable axis 13 One-way clutch 14 Gear 15 Stopper 2 Transport roller 3 Second transport roller 4 Pressure roller 6 Printing member P Recording medium

Claims (3)

[Claims] A transport roller that is rotatably driven; and a spur roller that has contact teeth radially protruding from an outer periphery thereof and is arranged to press the contact teeth against the transport roller. A recording medium transporting device that transports a recording medium downstream by a frictional force between the transport roller and the recording medium while nipping the recording medium between the transport roller and the spur roller with the rotation of the roller, wherein the spur roller transports the recording medium. A recording medium transport device configured to be rotatable only in a direction. 2. The recording medium conveying device according to claim 1, wherein the spur roller is configured to be rotatable only in a recording medium conveying direction by using a one-way clutch. 3. The spur roller is configured to be rotatable only in a recording medium conveyance direction by enabling a stop pawl to be engaged with at least one gear provided with respect to an axis of the spur roller. The recording medium transport device according to claim 1, wherein: