JPH0540378A - Image formation device - Google Patents

Abstract

PURPOSE:To provide the image formation device which disallows the head of recording paper to comes out of a couple of conveying rollers when returned as to an image formation device which corrects the skew or writes a registration mark by drawing the recording paper from a roller and returning the recording paper by the reversible conveying rollers. CONSTITUTION:A recording paper detection sensor 15 is provided right nearby the downstream side of the conveying roller couple 6 and when the recording paper 1 for the skew correction or registration mark writing is drawn from the roller by the conveying rollers 6 and returned, the driving of the conveying rollers 6 is stopped if a detection sensor 15 detects no paper.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses an image forming apparatus, particularly a recording paper roll, and is reciprocally conveyed a plurality of times to form images of different colors on the same image area of the recording paper to form a color print. The present invention relates to an image forming apparatus.

[0002]

2. Description of the Related Art As one method of an image forming apparatus for performing color printing, a recording paper pulled out from a recording paper roll is reciprocated a plurality of times along a conveying path, and recording is performed by a single writing head for each forward movement. It is known that an electrostatic latent image to be developed with different colors is written on the same area of paper, and the written electrostatic latent image is developed with one of a plurality of different colors to perform color printing. ..

FIG. 4 shows an overall schematic structure of a color electrostatic plotter as an example of a full-color image forming apparatus of this system.

Roll 1 of electrostatic recording paper wound in a roll
Is set on the roll paper holder 2 and pulled out in the transport direction indicated by arrow A. In the conveyance path of the recording paper 1, the return roller pair 3, the writing head 4, the yellow (Y), magenta (M), and cyan (C) three-color developing devices 5Y, 5M ,.
A developing unit 5 composed of 5C, a conveying roller pair 6, a cutter 7, a paper discharge roller pair 8 and the like are provided.

The conveying roller pair 6 is a stepping motor 1
The recording sheet 1 is driven in both forward and reverse directions by 1 and the recording sheet 1 is conveyed without slipping in the conveying direction (direction A) during normal rotation.

The return roller pair 3 is provided so that the recording paper 1 does not sag in the writing head 4 and the developing section 5.
A torque for pulling the recording sheet 1 in a direction opposite to the conveying direction is applied through a torque limiter (not shown) to apply tension to the recording sheet 1 and the recording sheet is conveyed at a predetermined speed without sagging. In this state, the electrostatic latent image is written on the recording paper 1 by the writing head 4, and the electrostatic latent image is developed by the developing unit 5. That is, the electrostatic latent image written by the writing head during the first forward transport is developed by the Y developing device 5Y, and when this is completed, the transport roller pair 6 is reversed and the recording paper 1 returns to the initial position, The image is written again, the M image is developed by the M developing device 5M, and the C image is similarly developed.
After the development of the three colors is completed, the front and rear edges of the image are cut by the cutter 7 to complete a full color print.

Recording is performed at a position a certain distance ahead of the front end of each image forming area of the recording paper so that the writing area of the electrostatic latent image by the writing head for the second time and thereafter exactly coincides with the image writing area for the first time. Prior to the first electrostatic latent image writing, the registration mark 12 extending in the width direction of the paper is drawn out from the recording paper roll by the conveying roller pair 6 while the registration mark latent image is written on the recording paper at a predetermined timing. And the registration mark 12 is developed by a developing device of any color.
Is formed. After the registration mark is formed, the recording paper is rewound by the pair of conveying rollers 6. The image writing is started at the time when one edge of the registration mark 12 on the recording paper is detected by the registration sensor 13 fixed to the apparatus, or at a predetermined timing thereafter. Since the registration sensor 13 is an optical fiber type photo sensor and is further focused by a lens, the detection accuracy is high. As a result, the image forming areas of the three electrostatic latent images to be developed with the three color developers are the recording paper. It matches with the conveyance direction with high accuracy, and color shift in the conveyance direction is prevented.

By the way, when a roll-shaped recording paper is reciprocated a plurality of times to superimpose images of a plurality of colors to form a full-color image, one highly accurate conveyance roller is used to prevent color misregistration in the width direction. It is configured to control feeding. However, skew (oblique feed) occurs in the roll-shaped recording paper due to the cylindrical accuracy of the transport roller, uneven load distribution in the width direction, and the like.

When a roll-shaped recording paper is reciprocally moved to form a plurality of images to form a color prelint, the skew generated during the forward movement is returned to the original position during the backward movement, and one color print is produced. There is no misalignment between multiple images (for example, three) that would hinder color superimposition, but when the recording paper is pulled out from the roll and repeated printing is performed, a slight misalignment is accumulated. The skew of the recording paper gradually increases, and the recording paper comes out of the working range of the writing device and the developing device.
Recording becomes impossible. Therefore, when the recording paper is repeatedly recorded from the roll wound with the recording paper, when the skew reaches a predetermined amount, it is necessary to detect the skew and correct the skew.

As a skew detecting means for the recording sheet, a skew detecting sensor 9 is provided outwardly at a certain distance from both end positions of the correct conveying width of the recording sheet, and one of the sensors detects the edge of the recording sheet. If detected, the skew is corrected.

Although there are various types of skew correcting mechanisms in the related art, the following mechanism has been proposed as a skew correcting mechanism capable of surely correcting the skew with a simple structure.

In the image forming apparatus shown in FIG. 4, this mechanism releases the pressure contact between the conveying roller pair 6 and the returning roller pair 3 and conveys the recording paper 1 only by the paper discharge roller 8. The paper discharge roller pair 8 is configured as a short roller provided at the center of the width of the recording paper, and both ends of the holder 2 of the recording paper roll 1 are lightly braked by friction members 10. When the recording paper is skewed, slack is generated in the part of the side end on the side away from the center line of the recording paper that is unwound from the recording paper roll and the tension does not occur, and that A tension F is generated by the brake of the friction member 10 at the opposite side end portion, and a tension F is generated at the portion sandwiched by the paper discharge roller 8 in opposition thereto, and a moment generated by a couple of these two forces. As a result, the skewed paper slips with the paper discharge roller 8 and automatically rotates in a direction in which the skew is corrected, and the skew is corrected. After the skew is corrected, the sheet is rewound by the length of the recording paper pulled out from the roll for skew correction.

By the way, in the image forming apparatus shown in FIG.
The return roller pair 3, the transport roller pair 6, the upper roller of the paper discharge roller pair 8 and the upper blade of the cutter 7 which constitute the transport unit are provided near the end of the recording paper roll 1 of the apparatus main body on the side opposite to the holder 2. It is attached to the upper lid that opens a large opening around the support shaft, and when setting the recording paper, open the upper lid to open the transport unit, and pull the recording paper pulled out from the recording paper roll 1 between the opened pair of transport rollers. After that, the upper lid is closed and pressure is applied so that the sheet can be conveyed.

Therefore, when the recording paper pulled out for the purpose of writing the registration mark or correcting the skew is rewound, if the leading end of the recording paper comes out of the conveying roller pair 6, the recording paper can be conveyed. No, you have to open the top lid of the device and reset it. Further, there is a problem that the recording paper touches the writing head and becomes dirty.

If the recording paper is controlled so as to be returned from the set state by the length pulled out for registration mark writing or skew correction, the tip of the recording paper will not come off from the pair of conveying rollers. When the amount is controlled at the same time as the pull-out amount or the number of pulses given to the conveyance roller drive motor, it is unavoidable that the conveyance amount of the recording paper differs between reciprocations due to slip of the conveyance roller and the recording paper.
The leading edge of the recording paper may come out of the transport roller.

When the resist mark is pulled out for writing, the image can be written immediately if the registration mark on the most front side is returned and stopped until the registration sensor detects it. However, if there is a reading error in the registration sensor, the leading edge of the recording paper may fall out of the conveying roller pair.

[0017]

SUMMARY OF THE INVENTION According to the present invention, in the image forming apparatus having the above-described structure, when the recording paper is pulled out and returned from the state in which the recording paper is set in the apparatus for writing the registration mark and correcting the skew, An object of the present invention is to provide an image forming apparatus in which the leading edge of a recording sheet does not come off from a pair of conveying rollers reliably.

[0018]

In order to solve the above-mentioned problems, the present invention provides a recording paper detecting means arranged in a position immediately downstream of a pair of conveying rollers in the image forming apparatus having the above-mentioned structure, When the sheet is rewound, a control means is provided for controlling to stop the conveying means when the detecting means detects the absence of paper.

[0019]

With the above structure, when the recording paper is pulled out from the set position for the purpose of writing the registration mark or correcting the skew and then returned, when the leading edge of the recording paper passes the detection means and the absence of the paper is detected, the conveying roller is conveyed. Since the pair is controlled so as to be stopped, the leading edge of the recording paper does not come out of the pair of transport rollers.

The timing of stopping the conveying roller is set to the earlier of the time when the detection means detects the absence of paper and the time when the registration sensor detects the first registered registration mark. As a result, not only can the leading edge of the recording paper be reliably prevented from falling out of the pair of conveying rollers, but if the return of the recording paper is stopped by the registration mark detection, the next image forming process can be immediately started from this state. .. Further, even though the registration sensor and the detection means are arranged at the position where the detection of the registration mark should be performed prior to the detection of the recording paper edge (detection of the paper end), the conveyance roller is stopped by the detection of the paper end of the detection means. In that case, it is considered that the writing of the resist mark is defective, and the next image forming process can be normally performed by writing the resist mark.

[0021]

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a diagram showing the configuration of an embodiment in which the present invention is applied to the color electrostatic plotter described in FIG. Therefore, members having the same function are designated by the same reference numeral,
The different points will be mainly described.

In the present embodiment, the recording paper detection sensor 15 is provided at a position immediately downstream of the conveying roller pair 6 in the forward direction (the direction in which the recording paper 1 is pulled out). Also, with this device,
The registration mark 12 is written at a constant interval by the writing head 4 while pulling out the recording paper 1 by the conveying roller pair 6 and developed with a certain written color, and then the conveying roller 6 is reversed to return the recording paper. Be done. The control means controls the conveying roller to stop when the detection sensor 15 detects the absence of the paper during the returning of the recording paper or the registration sensor detects the first registration mark. The other configurations are the same as those described with reference to FIG. 4, and therefore will not be repeatedly described.

Next, the operation of stopping the recording paper at the time of returning the recording paper after correcting the skew or writing the registration mark will be described with reference to FIGS. 2 and 3. FIG. 2 shows various states when stopping the recording paper when returning the recording paper. FIG. 3 is a flowchart showing a flow from the state where the conveying roller is driven in the direction of returning the recording paper to the stopping of the conveying roller.

In FIG. 3, the conveying roller 6 is driven in the direction of returning the recording paper (S1), and it is judged whether or not the registration sensor 13 has detected the first registered registration mark (S2). In the case ((a) of FIG. 2), the drive motor of the carry roller 6 is stopped (S3), and the process proceeds to the next image forming process (S4).

When the skew correction is performed immediately after the recording paper is set and the recording paper is returned, the detection sensor 15 detects the absence of paper because the registration sensor 13 is not written (S5). Even when the recording sheet is returned after the registration mark is written, the detection sensor 15 may be detected before the registration sensor 13 detects the registration mark 12 depending on the positional relationship between the registration mark 12, the registration sensor 13, and the recording sheet detection sensor 15. The absence of paper may be detected ((b) of FIG. 2). Further, if the registration mark is not written even if the writing process is performed, or if the registration mark is not detected by the registration sensor ((c) of FIG. 2), the detection sensor detects that there is no paper. To do. As a result, the drive motor of the transport roller 6 is stopped (S6).

If the registration mark is not yet written, the conveying roller is driven in the direction to pull out the recording paper (S
7) While the recording paper is being conveyed, the registration mark is written by the writing head (S8), developed and visualized (S).
9). After that, the conveyance roller is reversed and the recording paper is returned.

By controlling as described above, the recording paper can be reliably stopped so as not to come off from the conveying roller when the recording paper is pulled out from the roll for writing the registration mark or correcting the skew.

In the above-described embodiment, the stop of the returned recording paper is stopped by the detection of the paper edge by the recording paper detection sensor or the detection of the registration mark written first by the registration sensor, whichever comes first. Although the example in which the control is performed as described above has been described, even if the stop of the transport roller is controlled only by detecting the sheet edge of the recording sheet detection sensor, the recording sheet can be stopped so as not to come off from the transport roller.

[0030]

As described above, according to the present invention as set forth in claim 1, when the recording paper is pulled out from the roll and returned for the skew correction of the recording paper or the writing of the registration mark, the recording paper is conveyed by the roller. It is possible to stop it so that it does not come off from the position. Further, according to the configuration of claim 2, in addition to the above effect, it becomes possible to immediately start writing the image.

[Brief description of drawings]

FIG. 1 is a side view illustrating a configuration of an image forming apparatus according to an exemplary embodiment of the present invention.

2A, 2B, and 2C are diagrams showing various states when stopping the recording paper when returning the recording paper.

FIG. 3 is a flowchart showing a flow of an operation when returning the recording paper of the image forming apparatus according to the present invention.

FIG. 4 is a perspective view showing a configuration of an example of an image forming apparatus to which the present invention is applied.

[Explanation of symbols]

 1 Recording Paper 2 Recording Paper Roll Holder 3 Return Roller 4 Writing Head 5 Developing Device 6 Conveying Roller 7 Cutter 8 Paper Ejecting Roller 9 Skew Detection Sensor 10 Friction Member 12 Registration Mark 13 Registration Sensor 15 Recording Paper Detection Sensor 17 Conveyor Unit Open / Close Switch 18 Power switch

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshiyumi Tamiya 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Kazuaki Iizuka 1-3-6 Nakamagome, Ota-ku, Tokyo No. Stock Company Ricoh

Claims (2)

[Claims] 1. A color different from the same image forming area of the recording paper by the same write head having a conveying means capable of conveying the recording paper pulled out from the recording paper roll in forward and reverse directions. Write by overlapping the electrostatic latent images to be developed with
Each electrostatic latent image written is developed in a different color to perform color printing, and in order to align the writing position of each electrostatic latent image described above, a position a certain distance ahead of the front end of each image forming area of the recording paper. A registration mark is written on the recording paper, and a registration sensor for detecting the registration mark is provided in the main body of the apparatus, and the skew of the recording paper pulled out from the recording paper roll is corrected and the registration mark is written from the recording paper roll. In the image forming apparatus in which the recording sheet is pulled out and the skew of the recording sheet is corrected or the registration mark is written, the recording sheet is rewound to a position immediately before the sheet is removed from the conveying unit. An image forming apparatus provided with a control means for controlling the feeding means to stop when the detection means detects that there is no paper when the recording paper is rewound. Place 2. The timing for stopping the conveying means of the image forming apparatus according to claim 1 is a time when the detecting means detects the absence of paper, and the resist sensor detects the first registered registration mark. The image forming apparatus is characterized in that it is the earlier one of the two.