JP2003058016A - Double-sided image forming device and method for carrying recoding paper in double-sided image formation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such problems that image formation productivity is lowered and carrying control gets complicated because paper feeding intervals are not equal and a part of them gets larger in a consecutive double-sided image forming stage in the conventional double-sided image forming device. SOLUTION: The circulation reference time that recording paper circulates once in a circulation path is set to a short value, thus the paper feeding intervals in the consecutive double-sided image formation stage are uniformized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double-sided image forming apparatus, and more particularly, to control of conveyance of recording paper in a circulation conveyance path for forming a back side image.

[0002]

2. Description of the Related Art A double-sided image forming function provided in a high-speed image forming apparatus typified by an electrophotographic apparatus is one in which a recording sheet is fed from a sheet feeding section to a transfer section to form an image on the surface thereof.
Double-sided image formation is performed by feeding the image to the circulation conveyance path for forming the back side image, reversing the front and back sides of the circulation conveyance path and re-feeding the sheet to the transfer section to form an image on the back side.

In many double-sided image forming apparatuses, continuous double-sided image formation is carried out by repeating front-side image formation and back-side image formation in a continuous double-sided image formation process using a plurality of recording sheets as a unit. That is, for the number of sheets that can be accommodated in the circulation conveyance path, a plurality of recording sheets are fed into the circulation conveyance path by continuously performing surface image formation, and then, the recording paper is fed from the paper feed unit. The paper is stopped, and the recording paper on which the front surface image is formed is fed from the circulation conveyance path to the transfer portion to form the back surface image.

[0004]

The conveyance control of the recording paper in the continuous double-sided image forming process will be described with reference to FIGS. FIG. 1 shows an outline of a double-sided image forming apparatus.

The recording paper P is carried out one by one from a paper feed unit consisting of the storage unit 1 and the first paper feed unit 2, and is fed to the second paper feed unit 3. The image formed on the photoconductor 5 is transferred to the transfer unit 4.
At, the image is transferred to the recording paper P fed by the second paper feeding means 3, and the transferred image is fixed by the fixing means 6. In the single-sided image forming mode, the recording paper P after fixing is discharged to the paper discharge unit 7.

In the double-sided image forming mode, the recording paper P having an image formed on the front surface is sent to the circulation conveyance path 10 and turned upside down by the reversing section 10a, and then returns to the second paper feeding means 3.
The recording paper P is re-fed from the second paper feeding means 3 to the transfer section 4 to form a back side image. The recording paper P on which an image is formed on the back surface is discharged to the paper discharge unit 7 via the fixing unit 6. The recording paper on the surface of which an image is formed simultaneously travels in the plural-sheet circulating conveyance path 10 as indicated by P1, P2, and P3 in the figure.

FIG. 2 is a time chart of the conveyance control in the continuous double-sided image forming process, showing the passage time of the recording paper in the second paper feeding means 3.

The recording paper P is continuously fed by the second paper feeding means 3 at the paper feed interval T. The paper feed interval T is composed of a recording paper passage time t1 and a gap t2 between the recording papers. The recording paper passage time t1 is a time set for each recording paper size, and the gap t2 is a preset length of time.

FIG. 2 shows an example in which three sheets of recording paper run simultaneously in the circulating conveyance path 10, and P1 is applied to the three sheets of recording paper.
Surface image formation is continuously performed as indicated by f, P2f, and P3f. Next, P1r, P2r, and
Backside image formation is continuously performed as indicated by P3r. By repeating such front side image formation and back side image formation, a large number of continuous double sided image formations are performed.

The control means 11 manages the paper feed interval T in the front surface image formation by the logical product of the following three conditions.

Time-up of the interval timer built in the control means 11 The time set by the interval timer is preset for each size of the recording paper.

Completion of preparation for feeding by the second paper feeding means 3 The recording paper P is fed from the first paper feeding means 2 to the second paper feeding means 3, and the preparation for feeding paper by the second paper feeding means 3 is completed. is doing.

Preparation for image output or preparation for forming an image on the photoconductor 5 has been completed or image formation has been performed on the photoconductor 5.

Depending on the relationship between the distance between the image writing position on the photoconductor 5 and the transfer portion 4 and the distance between the second sheet feeding means 3 and the transfer portion 4, the image output preparation completion condition is set. There may be a condition that image output is being performed.

On the other hand, the paper feeding interval in the back side image formation is not directly controlled. That is, the recording paper P fed from the circulation conveyance path 10 to the second paper feed unit 3 by the front surface image formation is only received and conveyed by the second paper feed unit 3, and the second paper feed is performed in the back surface image formation. There is no control over the activation of the means 3. Therefore, the paper feed interval in the back side image formation becomes a value T which is almost equal to the paper feed interval in the front side image formation.

The feeding interval of the final recording paper P3f in the front surface image formation, that is, from the start of the recording paper P3f from the second paper feeding means 3 to the second recording paper P1r in the back surface image formation.
Paper feeding interval Tx, which is the time from the paper feeding means 3 to the departure
Is set in the design stage of the transport system so as to be wider than the standard paper feed interval T in consideration of variations in the traveling of the recording paper P in the circulation transport path 10. That is, the sheet feeding interval represented by Tx = T + ΔT is set when the front image formation shifts to the back image formation. The safety coefficient ΔT is set in consideration of variations in the traveling of the recording paper P in the circulation conveyance path 10.

The conveyance control of the recording paper P in the circulation conveyance path 10 is performed as follows. The circulation reference time RT is set as the time for one sheet of recording paper P to leave the second paper feeding means 3 and go around the circulation conveyance path 10 once.
Using the circulation reference time RT represented by n × T, it is determined whether to finish the front surface image formation and shift to the back surface image formation. The circulation reference time RT is RT = T × n0. n is a positive integer such as 1, 2, 3, ..., And n0 is the maximum value of the number of recording sheets that can be accommodated in the circulating conveyance path 10.

The control means 11 determines whether or not the circulation reference time RT ≧ n × T is satisfied before starting the second paper feeding means 3, and determines the number of sheets satisfying the circulation reference time RT ≧ n × T. Surface image formation is performed, circulation reference time RT <n ×
When it is predicted that T will occur, the paper feed from the circulation conveyance path 10 is switched to the back side image formation.

If a standard size is A4 size or a size that is slightly longer than a frequently used size such as 8.5 × 11 inch (1 inch = 25.4 mm), and a transport time conversion width of the standard size is Ty. , Circulation reference time RT = n
It is set to 0xTy.

The transport control in the above-described double-sided image formation is as follows in the concrete example of FIG.

In the specific example of FIG. 2, n0 = 3, the control means 11 forms the surface image of up to three sheets, and the circulating conveyance path 1
Three recording sheets P1f, P2f, and P3f are fed to 0.
When the fourth recording sheet is conveyed, the control means 11 uses the formula R
It is determined whether T ≧ 4 × T is satisfied, and RT <n × T
Therefore, the front surface image formation is completed and the back surface image formation is started. The paper feed interval Tx = T + ΔT, which is slightly wider than the paper feed interval T in the front image formation, is set as the paper feed interval when switching to the back side image.

As is clear from the above description, in the continuous double-sided image forming step, when the front side image formation is changed to the back side image formation, the paper is fed between the last recording sheet for front side image formation and the first recording sheet for back side image formation. The interval is wider than the regular paper feed interval. Therefore, the productivity of image formation in the continuous double-sided image forming step is reduced as the sheet feeding interval is extended.

An object of the present invention is to perform continuous double-sided image formation with the productivity of image formation equivalent to that of continuous single-sided image formation without eliminating the above-mentioned decrease in productivity of image formation in continuous double-sided image formation. An object of the present invention is to provide a double-sided image forming apparatus that can be used.

[0024]

The above-mentioned objects of the present invention are achieved by the following inventions.

1. A first paper feed means; a second paper feed means for receiving the recording paper from the first paper feed means and feeding it to a transfer section; and a second paper feed means including a transfer section and a reversing section as a starting point. 2 has a circulating conveyance path returning to the sheet feeding means, and a control means for controlling the first and second sheet feeding means, and the control means includes a1. After forming a front surface image on a plurality of recording paper sheets and feeding the plurality of recording paper sheets into the circulation conveyance path, the recording paper sheet having the front surface image formed thereon is fed from the circulation conveyance path to a transfer unit to display a back side image. Forming control, a2. Control for setting the paper feed interval in the front surface image formation to a value according to the recording paper size, and a3. In the double-sided image forming apparatus, which performs control for determining the number of recording sheets to be fed to the circulation conveyance path based on the circulation reference time and the sheet feeding interval, the control means includes b0. Control for setting the circulation reference time to a value smaller than an integral multiple of the paper feed interval, b1. Control for setting the paper feed interval formed by the final recording paper for front side image formation and the first recording paper for back side image formation to be equal to the paper feed interval for front side image formation, and b2. A double-sided image forming apparatus, wherein control is performed to set a paper feed interval in the back side image formation to be equal to a paper feed interval in the front side image formation.

2. It is possible to form an image on a plurality of sizes of recording paper, and the control means executes the control a1 to a3 and the control b0 to b2 for a part of the size on the smaller side, and the other sizes. Regarding the above, the double-sided image forming apparatus according to the above 1, wherein the controls a1 to a3 are executed but the controls b0 to b2 are not executed.

3. a1. By feeding the recording paper from the second paper feeding unit to the circulation conveyance unit having the transfer unit and the reversal unit, a surface image is formed on the plurality of recording papers and the plurality of recording papers are fed into the circulation conveyance path. After that, control for feeding the recording paper on which the front surface image is formed from the circulation conveyance path to the transfer portion to form the back surface image, a2. Control for setting the paper feed interval in the front surface image formation to a value according to the recording paper size, and a3. In the method of conveying recording paper in double-sided image formation, which controls the number of recording papers to be fed to the circulation conveyance path from the circulation reference time and the paper feed interval, at least an image of a recording paper size that is frequently used is used. When forming, b1. Control for setting the paper feed interval formed by the final recording paper for front side image formation and the first recording paper for back side image formation to be equal to the paper feed interval for front side image formation, and b2. A method of conveying recording paper in double-sided image formation, wherein control is performed to set a sheet-feeding interval in back-side image formation to be equal to a sheet-feeding interval in front-side image formation.

[0028]

FIG. 3 is a time chart of conveyance control in the double-sided image forming apparatus according to the embodiment of the present invention.

An embodiment of the present invention will be described with reference to FIGS. This embodiment is based on the following control in the conventional continuous double-sided image formation.

A1. After forming a front surface image on a plurality of recording papers P and feeding the plurality of recording papers P into the circulation conveyance path 10, the recording papers P having the surface images formed thereon are fed from the circulation conveyance path 10 to the transfer unit 4. Control to form a back side image, front side image formation is performed to feed a plurality of predetermined recording papers P into the circulation conveyance path 10, and then back side image formation is performed to the circulation conveyance path 1
The recording paper P is fed from 0 to the second paper feeding means. In the illustrated specific example, the back surface image is formed after the front surface image is formed on the three recording papers P1, P2, and P3. In Figure 3,
The recording paper on which the surface image is formed is set to P1f, P2f, P3.
The recording paper on which the back side image is formed is shown by P1r and P2.
r and P3r. P1f and P1r, P2f and P2r,
P3f and P3r are each one recording paper P1, P2, P
It is 3.

A2. In the control front surface image formation in which the paper feed interval T in the front surface image formation is set to a value corresponding to the recording paper size, the second paper feeding means 3 sets the recording paper P at the paper feed interval T including the recording paper passage time t1 and the gap t2. Is fed to the transfer unit 4 to form a front surface image. Then, the paper feed interval T is set to a value corresponding to the recording paper size by the interval timer built in the control means 11.

A3. The number of recording papers P to be sent to the circulation conveyance path 10 is determined from the circulation reference time [RT] at which the recording papers P leave the second paper feeding means 3 and return to the second paper feeding means 3 and the paper feed interval T. The control and control means 11 allows one sheet of recording paper P to pass through the circulating transport path 10
Set the circulation reference time [RT] to make a round, and [RT] ≧ n ×
Surface images are continuously formed on the n recording papers P satisfying T. n is a positive integer such as 1, 2, 3, .... The control means 11 stops new feeding from the recording paper P predicted to have [RT] <n × T to the second feeding means 3 and feeds paper from the circulatory conveying path 10 so that the back surface Transition to image formation.

In the present embodiment, the above a1 to a3
Based on the above control, the following control of b0 to b2 is performed.

B0. Circulation reference time [RT] is the paper feed interval T
Control for setting to a value less than an integer multiple of .circle-solid. That is, the formula [RT] = n ×
The circulation reference time [RT] is set to the value given by T-ΔT. ΔT is a positive number as a safety factor in consideration of variations in recording paper conveyance in the circulation conveyance path 10. As the specific size, a size having a value slightly longer than the most frequently used recording paper size such as A4 size or 8.5 × 11 inch size is selected. For example, in an image forming apparatus that forms 65 images per minute on A4 size recording paper, T = 923 ms, ΔT = 200 ms, [RT] = 3
492 ms is set. For large sizes such as A3 size and B4 size, the circulation reference time is set to a conventional RT equal to an integral multiple of the paper feed interval T instead of [RT], and the same control as the conventional one is performed.

B1. Control for setting the paper feed interval Tx formed by the final recording paper for front side image formation and the first recording paper for back side image formation to be equal to the paper feed interval T for front side image formation, and
The sheet feeding interval Tx from the time when the last recording sheet P3f for front side image formation is started in the second sheet feeding means 3 to the time when the first recording sheet P1r for back side image formation is started in the second sheet feeding means 3 is regular. The control unit 11 manages the activation of the second sheet feeding unit 3 so that it becomes equal to the sheet feeding interval T.

The control of b1 is performed by the formula [RT] = n0 × T-Δ
B0 for setting the circulation reference time [RT] so as to satisfy T
The second control for feeding the leading recording sheet P1r in the back side image formation so that the sheet feeding interval Tx = [RT] − (n−1) × T + ΔT is satisfied. It is realized by controlling the activation of the paper feeding means 3.

B2. Control for setting the paper feed interval in the back side image formation to be equal to the paper feed interval T in the front side image formation, and the second and subsequent recording sheets P2r, P3 in the back side image formation
For r, the activation of the second sheet feeding means 3 is controlled so that the sheet feeding interval T is formed. That is, the control unit 11 feeds the second recording sheet P2r after the sheet feeding interval T from the feeding of the first recording sheet P1r, and the feeding interval T from the feeding of the second recording sheet P2r. The third recording sheet P3r is placed and fed.

As a result, the recording papers P1 and P
The sheet feeding intervals of 2 and P3 are even values T.

By the control of b0 to b2 described above,
As shown in FIG. 3, all recording sheets are fed from the second sheet feeding means 3 to the transfer section 4 at the same sheet feeding interval T. Therefore, in double-sided image formation, image formation is performed with the same productivity as single-sided image formation.

[0040]

According to the first or third aspect of the present invention, the sheet feeding interval in continuous double-sided image formation can be made uniform without degrading the productivity of image formation. as a result,
The productivity of image formation is improved, and the conveyance control of recording paper in post-processing such as binding processing, punching processing and folding processing is stabilized, and smooth post-processing is performed.

According to the second aspect of the present invention, high-speed double-sided image formation is performed for a size that is frequently used.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of a double-sided image forming apparatus.

FIG. 2 is a time chart of conveyance control in conventional continuous double-sided image formation.

FIG. 3 is a time chart of conveyance control in the image forming apparatus according to the embodiment of the invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Storage part 2 1st paper feed means 3 2nd paper feed means 4 Transfer part 10 Circulation conveyance path T, Tx Paper feed interval RT, [RT] Circulation reference time P, P1, P2, P3, P1f, P2f, P3f, P1
r, P2r, P3r recording paper

Continued front page    F term (reference) 2H027 DC19 ED16 ED17 EE02 FA05                       FA13 FA33 ZA10                 2H028 BA06 BA09 BA14 BB04 BD03                 2H072 AB06 CB01 CB03                 3F100 AA01 CA13 CA15 CA17 EA03                       EA06

Claims (3)

[Claims] 1. A first paper feeding means, a second paper feeding means for receiving a recording paper from the first paper feeding means and feeding the recording paper to a transfer portion, and a second paper feeding means including the transfer portion and a reversing portion. And a control means for controlling the first and second paper feeding means, the control means in the continuous double-sided image forming step: a1. After forming a front surface image on a plurality of recording paper sheets and feeding the plurality of recording paper sheets into the circulation conveyance path, the recording paper sheet having the front surface image formed thereon is fed from the circulation conveyance path to a transfer unit to display a back side image. Forming control, a2. Control for setting the paper feed interval in the front surface image formation to a value according to the recording paper size, and a3. In a double-sided image forming apparatus that performs control for determining the number of recording sheets to be fed to the circulation conveyance path based on a circulation reference time and the sheet feeding interval, the control unit includes b0. Control for setting the circulation reference time to a value smaller than an integral multiple of the paper feed interval, b1. Control for setting the paper feed interval formed by the final recording paper for front side image formation and the first recording paper for back side image formation to be equal to the paper feed interval for front side image formation, and b2. A double-sided image forming apparatus, wherein control is performed to set a paper feed interval in the back side image formation to be equal to a paper feed interval in the front side image formation. 2. An image can be formed on recording paper of a plurality of sizes, and the control means executes the control a1 to a3 and the control b0 to b2 for a part of the smaller size. However, for other sizes, the controls a1 to a3 are executed, but the controls b0 to b2 are not executed, and the double-sided image forming apparatus according to claim 1. 3. a1. By feeding the recording paper from the second paper feeding unit to the circulation transportation unit having the transfer unit and the reversing unit,
After forming a front surface image on a plurality of recording paper sheets and feeding the plurality of recording paper sheets into the circulation conveyance path, the recording paper sheet having the front surface image formed thereon is fed from the circulation conveyance path to a transfer unit to display a back side image. Forming control, a2. Control for setting the paper feed interval in the front surface image formation to a value according to the recording paper size, and a3. In the method of conveying recording paper in double-sided image formation, which controls the number of recording papers to be fed to the circulation conveyance path from the circulation reference time and the paper feed interval, at least an image of a recording paper size that is frequently used is used. When forming, b1. Control for setting the paper feed interval formed by the final recording paper for front side image formation and the first recording paper for back side image formation to be equal to the paper feed interval for front side image formation, and b2. A method of conveying recording paper in double-sided image formation, wherein control is performed to set a sheet-feeding interval in back-side image formation to be equal to a sheet-feeding interval in front-side image formation.