JP2883452B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrostatic plotter for forming an image on roll paper, and more particularly to a skew correction mechanism for roll paper.

[0002]

2. Description of the Related Art In an image forming apparatus for forming an image by transporting roll paper by a transport roller pair, skew occurs when the roll paper is slightly bent when the roll paper is set on the transport roller pair. If image formation is continued in this state, the skew gradually increases, the image is distorted, and the image quality is reduced. In particular, in a slit developing type electrostatic plotter, when the skew of the roll paper increases, the roll paper deviates from the developable region, a negative pressure is not formed in the slit, and development becomes impossible, and the operation of the apparatus stops. In such a case, the operator must manually reset the roll paper.

In order to solve such a problem, an apparatus has been proposed in which a roll paper is set and then reciprocated several times between a feeding direction and a rewinding direction to correct the paper to a correct position. (See Japanese Patent Application Laid-Open No. 2-10066).

However, if the roll paper can be corrected to the correct position by such a method, it is necessary to cause a slip between the roll paper and the pair of conveying rollers, and if the skew can be corrected reliably in a short time. Not necessarily. Further, in the color image forming apparatus, if a pair of transport rollers that easily causes slippage is used, a high-quality full-color image without color shift cannot be created.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems in the prior art, and even when a transport roller pair for transporting roll paper without slipping is used.
An object of the present invention is to provide an image forming apparatus that can surely correct the skew of roll paper.

[0006]

In order to solve the above-mentioned problems, a first aspect of the present invention is a transporter having switching means for holding and releasing a roll paper held by a roll paper holder having a rotational resistance. An image is formed by the image forming means while applying a return force to the roll paper by a return roller pair provided with a switching means for similarly nipping and releasing the sheet, and then the sheet is transported by the discharge roller pair in the transport direction. In the image forming apparatus for feeding roll paper, the discharge roller pair includes a pair of narrow rollers, and further, skew detection means for detecting skew of the roll paper and control means are provided. When the means detects a skew, each of the switching means is operated so as to release the nip, and thereafter, the discharge roller pair is controlled to rotate for a predetermined time. Is configured to claim 2,
In addition to the above, the control means operates the respective switching means in the nipping direction after the rotational drive for skew correction of the discharge roller pair, and then moves the transport roller pair in the roll paper transport direction during image formation. Is rotated in the opposite direction.

[0007]

According to the present invention, in the first aspect of the present invention,
When the skew of the roll paper is detected by the skew detection means, the control means controls each switching means so as to release the nipping of the pair of conveying rollers and the pair of return rollers. Pulls the skewed roll paper while receiving the rotational resistance of the roll paper holder, a moment acts on the roll paper in the direction to correct the skew,
A so-called self-centering action occurs, and the width of the discharge roller pair is narrow, so that the roller paper moves in a direction perpendicular to the transport direction in the area of the discharge roller pair, and the skew is corrected.

According to the invention of claim 2, in addition to the above,
A discharge roller that releases the pinching release of the switching unit after the rotation drive for the skew correction of the discharge roller pair, and further rotationally drives the conveyance roller pair to be in the opposite direction to the roll paper conveyance direction during image formation. After the rotation drive for skew correction of the pair, each of the transport roller pair and the return roller pair sandwiches the roll paper again by the respective switching means. Since the rotation is performed in the opposite direction, the portion of the roll paper that has not been subjected to image formation after the skew is corrected can be rewound, and the roll paper is not wasted.

[0009]

1 and 2 show the configuration of an electrostatic plotter as an example of an image forming apparatus to which the present invention can be applied. A roll paper 1, which is an electrostatic recording paper wound in a roll, is set in a roll paper holder 2 and pulled out in a transport direction indicated by an arrow A. In the transport direction of the roll paper 1, the return roller pair 3, the write head 4 as a printing unit, and the three colors of yellow (Y), magenta (M), and cyan (C), which are examples of a developing unit, are sequentially arranged. A developing unit 5, a transport roller pair 6, a cutter 7, a paper discharge roller pair 8, and the like.

As the transport roller pair 6, a grit roller is used as the lower roller 6a, and a rubber roller is used as the upper roller 6b. The roll paper 1 is sandwiched between the two rollers, and is rotated in the transport direction (A direction) during normal rotation. The roll paper 1 is transported without causing a slip.

The return roller pair 3 is used to prevent the roll paper 1 from sagging in the writing head 4 and the developing unit 5.
The roll paper 1 is reversed by a torque limiter (not shown) so as to be sent in a return direction opposite to the transport direction, and the roll paper 1 is stretched. Then, in this state, an electrostatic latent image is written on the roll paper 1 by the writing head 4 and is developed by the developing unit 5. That is, in the developing section 5, first, the Y image is developed by the Y developing device 5Y, and when this is completed, the conveying roller pair 6 is reversed, and the roll paper 1 returns to the initial position,
The image is written again, the M image is developed by the M developing unit 5M, and the C image is developed in the same manner.

The discharge roller pair 8 rotates faster than the transport roller pair 6 via a torque limiter (not shown) so that the roll paper 1 does not sag on the downstream side of the transport roller pair 6. When the development of the three colors is completed, the leading and trailing edges of the image portion of the roll paper 1 are cut by the cutter 7 and discharged by the discharge roller pair 8 to obtain a full-color image. In this case, since the roll paper 1 is pressed and transported by the transport roller pair 6 which does not cause slip, a full-color image without color shift is obtained. However, when the roll paper 1 is set with a slight bend. In this case, the skew occurs, and the skew gradually increases, so that the roll paper 1 comes out of the developable area of the developing device 5.

In order to detect such a skew, a skew detecting sensor 9 as skew detecting means is provided outside both ends in the width direction of the roll paper 1. When skew is detected, the following skew is detected. Skew correction is performed before the image is created.

FIG. 3 shows the state of the transport system when skew correction is performed. As shown in the drawing, the return roller pair 3 and the transport roller pair 6 are in a nip release state in which the nipping of the roll paper 1 has been released, and the roll paper 1 is transported only by the discharge roller pair 8. At this time, the friction member 10 is
Lightly braked by. This friction member 1
Reference numeral 0 indicates that after the roll paper 1 is set in the transport system, the mouth is closed from the top of the apparatus (not shown), so that the roll paper 1 descends from above and comes into contact with the roll paper holder 2.

FIG. 4 shows a self-centering operation in which the skew is corrected. That is, when the roll paper 1 is pulled by the discharge roller pair 8 in the transport direction as shown in the drawing, the roll paper holder 2 is braked by the friction member 10, so that when the roll paper 1 is skewed, The one end 1a is pulled by the roll paper holder 2 with a force F. As a result, the roll paper 1 is conveyed while receiving a couple F as shown in FIG. The skew is corrected by slipping in the width direction at the position of the receiving and discharging roller pair 8.

According to an experiment, when a paper discharge roller pair having a width of 40 mm is used and a skew detection sensor is provided on the upstream side near the conveyance roller pair, the widthwise displacement of the roll paper 1 is equivalent to 2 mm by the sensor. When the skew was detected, the result was obtained that the skew was completely corrected by feeding the roll paper 1 by about 500 mm. In the embodiment shown in FIG. 4, the paper discharge roller pair 8 is provided substantially at the center of the roll paper 1 in the width direction. In this way, the skew correction moment of the same magnitude can be obtained regardless of the skew of the roll paper 1 in any direction. However, the position of the discharge roller pair 8 needs to be always at the center. There is no.

After the skew correcting operation is performed, the nip between the return roller pair 3 and the transport roller pair 6 is returned to enable the next image formation. In this case, it is desirable that the transport roller pair 6 be rotated in the reverse direction so that the roll paper 1 is returned by the length sent for skew correction. In this way, the roll paper 1 is not consumed.

FIG. 5 shows another embodiment of the discharge roller pair 8. It is desirable that the width of the discharge roller pair 8 is narrow for skew correction. The narrower the width, the more effective the self-centering action, the shorter the transport distance of the roll paper 1 for skew correction, and waste of paper. And time for repairs is reduced. For this reason, the structure is further improved by providing an O-ring 8b on the inner upper roller 8a of the paper discharge roller pair 8 as shown in the figure.

FIG. 6 shows an example of the mechanism of the switching means for holding and releasing the return roller pair 3 and the conveying roller pair 6 and other switching means. For the sake of simplicity, the case of the transport roller pair 6 will be described. Bearing 6b- for supporting the shaft end 6b-1 of the upper roller 6b of the conveying roller pair 6.
2 is a pressure spring 6b-4 provided in the guide groove 6b-3.
Is pressed in the nip direction for holding the roll paper 1. On the other hand, a lever 6b-6 rotatably supported on the rotating shaft 6b-5 is provided, and a bearing portion 6b-
2 and the other end is connected to a solenoid 6b-7.

When the skew correction operation is performed for a predetermined time,
CP for controlling, for example, an electrostatic plotter as control means
A signal is sent from U11 to the solenoids 3b-7 and 6b-7, which are actuated to pull the levers 3b-6 and 6b-6 to release the roller nip. As a result, the skew is corrected as described above.

When a large pressing force is applied by the pressurizing spring 6b-4, the pressure can be released by a one-turn clutch and a cam.

When the operation of correcting the skew of the roll paper 1 is completed, the CPU 3 sends the solenoids 3b-7 and 6b-
, Stop the operation, and pressurize the spring 3b-4.
The return roller pair 3 and the transport roller pair 6 are again brought into the nip state by the urging force of 6b-4 and 6b-4, so that image formation is possible. In this case, if a signal is sent from the CPU 11 to the driving means (not shown) for the transport roller pair 6 to reverse the transport roller pair 6, the roll paper 1 is rewound as described above. The skew of the unwound roll paper 1 is confirmed by the skew detection sensor 9 installed on the upstream side of the transport roller pair 6 in the transport direction.

Even if the skew of the roll paper 1 is corrected as described above, even if the skew of the roll paper 1 is
If the parallelism with the axis is not the same, skew occurs again, so it is necessary to maintain the parallelism of both axes as much as possible. For this reason, a taper is provided in the flange portion of the roll paper holder 2 to support the inner surface end of the roll paper 1.

[0024]

As described above, according to the present invention, when skew occurs in the roll paper, the holding of the pair of return rollers and the pair of transport rollers is released,
By transporting the roll paper with the transport roller pair while applying rotation resistance, even if the transport roller pair does not cause slip, without providing a special mechanism such as a jogger or relying on operator operation The skew of the roll paper can be automatically corrected.

According to the invention of claim 2, in addition to the above,
By reversing the pair of transport rollers, the roll paper can be rewound to prevent waste.

[Brief description of the drawings]

FIG. 1 is a side view illustrating a schematic structure of an electrostatic plotter that is an example of an image forming apparatus according to an embodiment.

FIG. 2 is a plan view of the above.

FIG. 3 shows a state in which a nip between a return roller pair and a transport roller pair is released in FIG.

FIG. 4 is an explanatory diagram of a self-centering operation in which a skew is corrected.

FIG. 5 is a plan view showing an embodiment in which an O-ring is provided on an upper roller of a pair of paper discharge rollers.

FIG. 6 is an explanatory view of a nip releasing mechanism.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 roll paper 2 roll paper holder 3 return roller pair 4 writing head (printing means) 5 developing unit (developing means) 6 transport roller pair 8 discharge roller pair 9 skew detection sensor 10 friction member (rotational resistance) 11 CPU (control) Means) 3b-7, 6b-7 solenoid (other switching means,
Switching means)

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tadahiro Suzuki 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Kazuaki Iizuka 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Inventor Seiichi Miyagawa 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh Co., Ltd. (72) Shigeru Suzuki 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company (56) References JP-A-1-167153 (JP, A) JP-A-62-2245 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) B65H 23 / 00-23/34 B65H 20/02 G03G 15/00

Claims (2)

(57) [Claims] 1. A switching means for holding a roll paper held by a roll paper holder having a rotation resistance between a pair of transport rollers provided with a switching means for holding and releasing the holding, and also for holding and releasing the holding. In an image forming apparatus in which an image is formed by an image forming unit while applying a return force to roll paper with a pair of return rollers provided, and the roll paper is fed in a transport direction by a pair of discharge rollers, the pair of discharge rollers has a width of one pair. A skew detecting means for detecting skew of the roll paper and a control means, the control means operating the respective switching means so as to release the nip when the skew detecting means detects the skew; An image forming apparatus configured to control to rotate the discharge roller pair for a predetermined time after that. 2. The control means activates each of the switching means in the nipping direction after rotationally driving the paper discharge roller pair for skew correction, and thereafter causes the transport roller pair to move in the roll paper transport direction during image formation. The image forming apparatus according to claim 1, wherein the image forming apparatus is driven to rotate in a direction opposite to that of the image forming apparatus.