JP2960816B2 - Electrophotographic double-sided copying method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic double-sided copying method, and more particularly, to an improvement of an electrophotographic double-sided copying method suitable for improving efficiency in double-sided copying.

[0002]

2. Description of the Related Art In recent years, progress in electrophotographic processes has been remarkably remarkable, and techniques such as full-color copying and double-sided copying have already been generalized, and copy efficiency tends to be further improved. By the way, looking at the conventional double-sided copying technology, although the technology has been established, the loss time at the operation stage is large, and the customer is not necessarily satisfied in this regard. Further, in the conventional technology, paper of different sizes is not mixed and subjected to double-sided processing. After processing all papers of the same size once, the size is set again and then processed. Even if an intermediate unit having a matching function (a part for reversing and temporarily storing single-sided copied paper) is provided, it is very difficult to feed paper of different sizes, which may cause a paper feeding error or oblique feeding. Easy to cause.

Here, a conventional double-sided copying technique will be described with reference to a flowchart shown in FIG. In the figure, N is a desired number of copies. First, step 1 (S
After paper is fed from the cassette in step 1), step 2
In step (S2), the first surface is transferred. Next, this is stored in the intermediate tray of the intermediate unit in step 3 (S3), and the operation between step 4 (S4) and step 1 (S1) is repeated until copying of N sheets is completed. This S1
→ The range between S4 and S4 is a range in which one-sided copying is performed. In this way, the copy processing unit is in a "waiting" state and does not operate until all of the N copies whose one-sided copy has been completed on the intermediate tray are completed in step 5 (S5). If the accommodation of N sheets is completed, step 6 (S
At 6), re-feeding from the intermediate tray to the copy processing section is started, and the transfer of the second side is performed at step 7 (S7), so that double-sided copying is completed, and step 8 (S8).
Then, steps 9 (S9) and 6 (S6) are repeated until all the N sheets of double-sided copying are completed in step 9 (S9), and the process is terminated.

[0004]

As shown in the flowchart of FIG. 20, according to the conventional double-sided copying technique, after one-sided copying is completed in steps 1 to 4, all the one-sided copying is performed in step 5. Since the sheet is stored in the intermediate tray and the remaining surfaces are copied again in steps 6 to 9, the step 5 is a complete loss time. This loss time (t) is governed by the total length l of the transport unit and the transport speed v from the transfer unit of the copying machine to the intermediate tray through the reversing unit that reverses the sheet conveyed after being single-sided copied and conveyed (t). = L /
v), and the total copy time is [N sheet feed (single-sided copy) time + loss time + N sheet re-feed (double-sided copy) time], so that t is substantially constant as a value unique to the apparatus. Therefore, as N becomes smaller, the time required for double-sided copying per sheet becomes longer.

For example, an automatic document feeder (Au
to Document Feeder, ADF), read one document at a time, and copy one or more copies. If the original for the front side is indicated by F and indicated by ○, the original for back side is indicated by R and indicated by Δ, If you have many copies to copy,

(Equation 1) After the required number of copies of the front side of the first document have been completed, the process proceeds to the back side for that amount, and after that, the front side copy of the second document is performed. However, if the required number of copies is extremely small, for example, only one copy,

(Equation 2) Then, every time the surface is switched from the front side to the back side, the accommodating operation to the intermediate tray is performed, which results in a loss time and lowers the copy efficiency.

A ternary diagram shown in FIG. 21 is a graph of the above relationship based on actual measurement values from the number of original pages and the number of copies. The figure shows the number of original pages M on the X axis, the number of copies N on the Y axis, and the efficiency of the copying machine on the Z axis.
As can be seen from the figure, it is apparent that the copying efficiency hardly depends on the number M of documents, but is highly dependent on the number of copies N, and it is extremely difficult to achieve an efficiency of nearly 100%. is there. As described above, in the conventional double-sided copying technology, the copying efficiency is limited solely by the number of copies N. Further, in general, double-sided copying when sheets of different sizes are mixed is extremely complicated or impossible. Since copying is performed for each size, improvement in copying efficiency has not been solved in this aspect. Therefore, an object of the present invention is to eliminate the loss time in duplex copying to achieve an improvement in copying efficiency, and to store and feed different-sized papers in an intermediate tray so that they can be aligned. It is an object of the present invention to provide an electrophotographic double-sided copying method that does not cause a feeding error or a skewed feeding even when mixed.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the gist of the present invention is to perform double-sided copying in which copying paper sizes of different sizes can be mixed by an electrophotographic process. The one-sided copied sheet is stored in the intermediate tray, and the aligning operation for adjusting the posture of the one-sided copied sheet is performed by the aligning means including the movable side end regulating plate and the rear end regulating plate provided on the intermediate tray. Performed, when it is detected that the next sheet having a different size from the one-sided copied sheet has been conveyed toward the intermediate tray,
In the electrophotographic two-sided copying method in which the one-sided copied paper is preferentially completed in the two-sided copying and discharged, if the detected next sheet is larger in size than the one-sided copied sheet stored in the intermediate tray, the The two-sided electrophotographic copying method is characterized in that the rear end regulating plate is moved to the size of the next sheet when the aligning operation on the copied sheet is completed.

[0008]

According to the present invention, when two-sided copying is performed on a sheet in which different sizes of copying paper are mixed by an electrophotographic process, the single-sided copied sheet is stored in an intermediate tray, and the movable tray provided on the intermediate tray is provided. An aligning operation for adjusting the posture of the single-sided copied paper is performed by the aligning means including the side end regulating plate and the rear end regulating plate. Then, when a sheet of a different size from the sheet previously stored in the intermediate tray and single-sided is conveyed toward the intermediate tray, this is detected, and the sheet stored earlier is given priority. The remaining surface is conveyed to the photosensitive drum, and printing is performed on the remaining surface. Then, the subsequent different-sized paper is copied on one side and stored in the intermediate tray, and the paper is fed for printing after the posture is controlled by the aligning means. In this manner, since the alignment operation is performed, accurate paper feeding without occurrence of a paper feeding error or skew feeding is performed without time loss. Furthermore, if the size of the paper conveyed to the intermediate tray next is larger than the size of the single-sided copied paper stored in the intermediate tray, the rear end regulating plate is set to the next paper size when the alignment operation is completed. Since it is moved and put on standby, only the side end regulating plate needs to be moved during the next alignment operation. Therefore, it is not necessary to move all the regulation plates at the same time, and it is possible to reduce the operation noise, average the power consumption, and quickly move.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing the overall configuration of a digital copying machine which is an embodiment of a double-sided image forming apparatus provided with a sheet conveying device used in the present invention. As shown in FIG. 1, a digital copying machine 30 of this embodiment includes a scanner unit 31 and
A laser printer unit 32, a multi-stage paper feed unit 33, and a sorter 34 are provided. The scanner unit 31 includes a document table 35 made of transparent glass, a double-sided automatic document feeder (RDF) 36, and a scanner unit 40. The multi-stage paper feed unit 33 includes a first cassette 51,
It has a second cassette 52, a third cassette 53, and a fifth cassette 55 that can be added by selection. In the multi-stage paper feed unit 33, sheets are fed out one by one from the sheets stored in the cassettes of each stage, and the laser printer unit 32
Conveyed toward.

The RDF 36 sets a plurality of originals at once, automatically feeds the originals one by one to the scanner unit 40, and transfers one side or both sides of the original to the scanner unit 40 according to an operator's selection. It is configured to read. The scanner unit 40 includes a lamp reflector assembly 41 for exposing a document, a plurality of reflection mirrors 43 for guiding a reflected light image from the document to a photoelectric conversion element (CCD) 42, and a device for forming a reflected light beam from the document on the CCD 42. Lens 44 is included. Scanner unit 3
1 is configured such that when scanning a document placed on the document table 35, the scanner unit 40 reads the document image while moving along the lower surface of the document table 35, and uses the RDF 36. In this case, the document image is read while the document is being conveyed while the scanner unit 40 is stopped at a predetermined position below the RDF 36.

Image data obtained by reading the original image by the scanner unit 40 is sent to an image processing unit (not shown), which will be described later, and is subjected to various processes, and then temporarily stored in a memory of the image processing unit. The image data in the memory is provided to the laser printer unit 32 in response to the output instruction to form an image on a sheet. The laser printer unit 32 includes a manual document tray 45, a laser writing unit 46, and an electrophotographic process 47 for forming an image. The laser writing unit 46 includes a semiconductor laser that emits a laser beam corresponding to the image data from the above-described memory, a polygon mirror that deflects the laser beam at an equal angular speed, and a laser beam that is deflected at an equal angular speed. It has an f-θ lens and the like for correcting so that it is deflected at a constant speed on the body drum 48. The electrophotographic process 47 includes a charger, a developing device,
Transfer unit, peeling unit, cleaning unit, static eliminator and fixing unit 4
9 are arranged.

A transport path 50 is provided downstream of the fixing unit 49 in the transport direction of the sheet on which an image is to be formed. The transport path 50 is connected to a transport path 57 leading to the sorter 34 and a multi-stage paper pickup unit 33. It branches into a conveying path 58 which communicates therewith, and the conveying path 58 continues to a duplex unit 101 described later. The multi-stage paper feed unit 33 includes a common conveyance path 56, which is configured to carry out the sheets from the first cassette 51, the second cassette 52, and the third cassette 53 toward the electrophotographic processing unit 47. It is configured.
The common transport path 56 joins with the transport path 59 from the fifth cassette 55 on the way to the electrophotographic processing section 47 and communicates with the transport path 60. The conveyance path 60 joins a double-sided conveyance path and a conveyance path 61 from the manual document tray 45 at a junction 62 so as to communicate with an image forming position between the photosensitive drum 48 and the transfer unit of the electrostatic photographic processing unit 47. Is composed of
The junction 62 of these three transport paths is provided at a position near the image forming position.

Therefore, in the laser writing unit 46 and the electrophotographic processing unit 47, the image data read from the above-mentioned memory is transferred to the laser writing unit 46.
The donor image formed as an electrostatic latent image on the surface of the photosensitive drum 48 by being scanned with the laser beam by the laser beam, and visualized by the toner is placed on the surface of the sheet conveyed from the multi-stage sheet feeding unit 33. Electrotransfer and fixation. The sheet on which the image has been formed in this manner is sent from the fixing device 49 to the sorter 34 via the transport paths 50 and 57, or is transported to the reverse transport path 50a via the transport paths 50 and 58. The common transport path 56 is an embodiment of the first transport path of the present invention. The first cassette 51, the second cassette 52, and the third cassette 53 are one embodiment of the sheet feeding unit of the present invention.

Next, the digital copying machine 30 of this embodiment
The configuration and function of the image processing unit included in the above will be described.
FIG. 2 is a block diagram of the image processing unit included in the digital copying machine 30 of FIG. Digital copier 30
Includes an image data input unit 70, an image processing unit 71, an image data output unit 72, a memory 73 including a RAM (random access memory), and a central processing unit (CPU) 74. I have. The image data input unit 70 includes a CCD unit 70a, a histogram processing unit 70
b and an error diffusion processing unit 70c. The image data input unit 70 binarizes the image data of the original read from the CCD 42 in FIG. 1 and processes the image data by an error diffusion method while obtaining a histogram as a binary digital amount. Is stored once.

That is, in the CCD section 70a, after an analog electric signal corresponding to each pixel density of image data is A / D converted, MTF correction, monochrome correction or gamma correction is performed.
The signal is output to the histogram processing unit 70b as a digital signal of 256 gradations (8 bits). Histogram processing unit 7
In the case of 0b, the digital signal output from the CCD unit 70a is added for each pixel density of 256 gradations to obtain density information (histogram data), and the obtained histogram data is sent to the CPU 74 as necessary. The data is sent to the error diffusion processing unit 70c as pixel data. In the error diffusion processing unit 70c, the 8-bit / pixel output from the CCD unit 70a is processed by an error diffusion method, which is a kind of pseudo halftone processing, that is, a method of reflecting a binarization error in the binarization determination of an adjacent pixel. Digital signal is 1 bit (binary)
, And a redistribution calculation for faithfully reproducing the local area density in the document is performed. The image processing section 71 includes multi-value processing sections 71a and 71b, a synthesis processing section 71c, a density conversion processing section 71d, a scaling processing section 71e, an image processing section 71f, an error diffusion processing section 71g, and a compression processing section 71h.
Contains.

The image processing section 71 is a processing section for finally converting the input image data into image data desired by the operator, and stores the converted image data in the memory 73 until the converted image data is finally stored. The processing unit is configured to perform the processing. However, the above-described processing units included in the image processing unit 71 function as needed, and may not function in some cases. That is, the multi-value processing section 71a
And 71b, the data binarized by the error diffusion processing unit 70c is converted again into 256 gradations. Combination processing unit 71
In c, a logical operation for each search, that is, an operation of a logical sum, a logical product, or an exclusive logical sum is selectively performed. The data to be subjected to this calculation is the search data stored in the memory 73 and the bit data from the pattern generator (PG).

The density conversion processing section 71d arbitrarily sets the relationship between the input density and the output density for the 256-level digital signal based on a predetermined tone conversion table. The scaling unit 71e calculates the pixel data (density value) for the target pixel after scaling by performing an interpolation process based on the input known data in accordance with the designated scaling factor. After the multiplication, the main scanning is scaled. In the image processing section 11f, various image processings are performed on the input pixel data, and information collection such as feature extraction can be performed on the data sequence. The error diffusion processing unit 71g performs the same processing as the error diffusion processing unit 70c of the image data input unit 70. Compression processing unit 71h
In, binary data is compressed by encoding called run length. As for the compression of the image data, the compression functions in the final processing loop when the final output image data is completed.

The image data output section 72 includes a restoration section 72a, a multi-value processing section 72b, an error diffusion processing section 72c, and a laser output section 72d. The image data output unit 72 restores the image data stored in the memory 73 in a compressed state, converts the image data back into the original 256 gradations, and generates an error in the quaternary data that provides a smoother halftone expression than the binary data. Spread,
It is configured to transfer data to the laser output unit 72d. That is, the decompression unit 72a decompresses the image data compressed by the compression processing unit 71h. The multi-value processing section 72b performs the same processing as the multi-value processing sections 71a and 71b of the image processing section 71. Error diffusion processing unit 72
c, the error diffusion processing unit 70c of the image data input unit 70
Is performed.

In the laser output section 72d, digital pixel data is converted into a laser on / off signal based on a control signal from a sequence controller (not shown), and the laser is turned on / off. The data handled by the image data input unit 70 and the image data output unit 72 is basically two data in order to reduce the capacity of the memory 73.
Although stored in the memory 73 in the form of value data, it is also possible to perform processing in the form of quaternary data in consideration of deterioration of image data.

FIG. 3 is a schematic sectional view showing the vicinity of the duplex unit 101 shown in FIG. The paper sent from each paper storage unit (not shown) is conveyed from below the right side of the unit. When the sensor detects a sheet from the sheet storage unit, the transport rollers are temporarily stopped, and restarted at a timing with the other transport units. The sheet that has passed the conveyance junction is conveyed to the image forming position via the conveyance roller H and the registration roller I. The registration roller I starts its operation in accordance with the leading end of the toner image formed on the photosensitive drum 48, and feeds the paper sandwiched between the nips. The paper on which a predetermined image is recorded on the recording surface side of the paper is discharged to the paper discharge tray side after passing through the fixing device 49, guided to the duplex unit 101 side, or switched according to a copy mode. This time the inverted paper guide 2
First, according to the present invention, the conveyed sheet is guided to the duplex unit 101 side.

The sheet conveyed from the upper left portion of the duplex unit 101 is once led to the intermediate tray 3. At this time, when the sensor DS1 detects the leading edge of the sheet, the solenoid DS
The state of OL1 is checked, and if the paper presser plate (feeder plate) 1 is acting on the trade-in feed roller B side as shown in the figure, the solenoid DSOL1 is turned off, and the paper presser plate 1 moves from the state in the figure to the arrow. It is turned to the OFF state in the direction. That is, the sheet is retracted upward so as not to hinder the sheet conveyance when the sheet is inserted. As will be described in detail later, the intermediate tray 3 is provided with a side end regulating plate 4 and a rear end regulating plate 5, which are configured to move back and forth and left and right according to the size of the sheet sent to the intermediate tray 3 in advance. I have. The sheet once stored in the intermediate tray 3 is turned on by the solenoid DSOL1 at a timing at which no continuous sheet comes, and the sheet is pressed from above toward the feed roller B side. At this time, since the roller B is rotating in the direction of the arrow,
The sheets stored in the intermediate tray 3 are fed leftward.

The paper fed by the trade-in feed roller B is then separated by the separating roller C without fail into a single sheet, so that double feeding is prevented. The friction member 6 is in contact with the separating roller C. If double feeding of paper occurs, only the bottom sheet is sent to the next step, and the other sheets are prevented from being transferred by the friction member 6. Is what you do. The sensor DS2 is arranged to detect the leading edge of the separated paper. If the sensor DS2 is not turned on within a predetermined time after the trade-in paper feeding in the previous process is performed, the sensor DS2 is processed as a paper feeding error. The Rukoto. If the sensor DS2 is turned on within the predetermined time, it means that the operation is in order, and the process proceeds to the next step. DS via transport roller D and transport roller E
After DS3 is turned on, DS4 is set to O
N, the transport rollers G and F are stopped when the leading edge of the sheet has entered the transport roller G.

In this conveyance path, the length between the conveyance roller G and the conveyance roller F is set to the length of 51 A4 / B sheets. When the sensor DS3 is turned on for the succeeding sheet, 51 sheets of A4 and B sheets are located in the area between the sensor DS3 and the transport roller E. When the sensor DS2 is turned on for the succeeding sheet, the sheet A4.
If the sheet is B5, the roller D reaches the intermediate tray 3 via the sensor DS2 and the separating roller C and stops. When all of the sheets are A4 and B5, the fourth sheet is stopped because the conveyance of all the preceding three sheets has stopped.
It will be housed in. That is, the rear end portion of the third sheet and the fourth sheet are partially overlapped on the intermediate tray 3. When the previous transport roller G restarts with the timing of another transport section, the subsequent paper sheets also restart sequentially.

In the above description, the paper sizes are all A4 and B5. However, the paper sizes may be all A3 and B4, or A3, B4, A4 and B5 may be mixed. When the A3 / B4 sheet stops at the transport roller G first, the length of the transport roller G is twice as long as A4 / B5.
Occupies the conveyance path from the conveyance roller E to the conveyance roller E.
This state is the same regardless of the position at which the conveying roller stops. That is, when the A4 / B5 sheet stops at the transport roller G and the A3 / B4 sheet stops at the sensor DS3, the trailing end of the A3 / B4 sheet reaches the intermediate tray 3 and stops. .

As shown in FIG. 3, when the paper holding plate 1 acts at a predetermined paper feed timing in which the paper is stored in the intermediate tray 3 and presses the paper against the trade-in roller, When the sensor DS1 detects that the sheet enters the intermediate tray 3, the operation of the trade-in feeding roller B and the sheet holding plate 1 is temporarily stopped. That is, when the succeeding paper is sent toward the intermediate tray 3, the paper pressing plate 1 is retracted upward, and priority control is performed so that the subsequent paper does not collide.

Finally, when the feeding of the sheet from the conveying roller G is restarted at the timing of the sheet sent from another conveying path, the sheet is conveyed again to the image forming position via the conveying roller H and the registration roller I. Then, another image different from the front surface is formed on the back surface of the sheet. The sheet on which the toner image has been formed passes through the fixing section and is discharged to the sheet discharge tray side by the switching gate.

In the normal double-sided copy mode, the temporarily stopped sheet is fed again at a predetermined timing in order from the transport roller G. If, for example, more than one cycle of copy time is required for image processing, the paper in the transport path of the duplex unit 101 must be stopped. FIG. 4 is a schematic diagram for explaining the operation of the sheet of the apparatus shown in FIG. 1 centering on the duplex unit 101 of the apparatus. As shown in FIG. The first sheet and the (n + 2) th single-side copied sheet are stopped in the transport path, and the (n + 3) th and subsequent (up to the i-th) single-side copied sheet are accumulated in the intermediate tray 3. However, in order not to reduce the total copying efficiency, if the copy of the first side is possible, for example, paper is fed from the cassette 51 and the copy of the first side is performed. By performing such control, the copy cycle is executed without stopping or delaying, so that the copy efficiency can be improved.

Next, the configuration and operation of the aligning means provided on the intermediate tray 3 shown in FIG. 3 will be described. 5 is a plan view for explaining the concept of the aligning means provided on the intermediate tray 3 in the duplex unit 101 in FIG. 3, and FIG. 6 is a front view of the aligning means. Immediately before the paper is input, the side end regulating plate 4 is moved to a position slightly wider than the set size. For example, if the setting size is A
In the case of the vertical feed of 4, the length is 303 mm, which is 297 mm + 4 mm.
In this case, as the moving means of the side end regulating plate 4, for example, a known means composed of a combination of a rack 7 and a pinion 8 as shown in FIG. 5 can be used. Next, when the recording paper P enters the intermediate tray 3, the side end regulating plates 4 first move inward by the set value, and then (A) in FIG.
As shown schematically in FIG. 7B, the recording paper P is moved from the outside to the inside (for example, 2 mm) by the set value to reduce the deviation of the recording paper P in FIG.
Correct as follows. Similarly, the trailing edge regulating plate 5 also corrects the deviation of the paper. For example, when the paper changes from A4 to A3, the paper moves to a width slightly larger than the paper width of A4 (210 mm). The moving speed of the rear end regulating plate 5 in the intermediate tray 3 needs to be rapidly movable, for example, 200 mm / sec from the viewpoint of improving the copying efficiency. Note that these regulating plates 4 and 5 can be driven by means such as a pulse motor DMOT provided in the duplex unit 101 shown in FIG. 3, for example.

After the alignment operation is completed and the posture at the time of paper feeding is adjusted, the rear end regulating plate 5 does not need to be set at least at the rear end of the paper, and the paper conveyed to the intermediate tray 3 next You only have to move according to the size. However, if the size of the sheet is shorter than the sheets stored in the intermediate tray 3, the movement of the regulating plate 5 is not performed, and the movement is performed when all the sheets in the intermediate tray 3 are discharged. FIG. 8 summarizes the above matching operation in a flowchart. The outline of the contents is as described above. First, after the paper (recording paper P) is stored in the intermediate tray 3 in step 1 (S1), the side end regulating plate 4 and the rear end regulation are performed in step 2 (S2). FIGS. 5 to 7 show the alignment operation of the plate 5 previously described.
It is performed as follows. Next, in step 3 (S3), it is detected whether or not the next sheet exists, and if not, the aligning operation ends there. On the other hand, if there is, the next sheet size is compared in step 4 (S4), and if it is larger than the current storage size, the process proceeds to step 5 (S5). The plate 5 is moved to the position of the next paper size (for example, A4 → A3). If the size is smaller than the current storage size, after all the sheets in the intermediate tray have been ejected in step 6 (S6), the movement of the regulating plates 4 and 5 is started to match the next sheet size. In step 7 (S7), the setting of the side end regulating plate 4 and the rear end regulating plate 5 to the next sheet size is completed, and thereafter, the process returns to step 1 (S1) to perform the same operation.

First, the originals sent by the automatic document feeder (ADF) of the copying apparatus are sequentially read by using the above-described double-sided unit 101 in the same manner as described in the description of the prior art. Let us consider the case of copying more than one copy. In this case, as in the previous case,
In addition, the configuration of the vicinity of the duplex unit 101 shown in FIG. Drawings of a series corresponding to the paper procedure are shown in FIGS. In these figures, ...
Are the order of the sheets (the n-th sheet, the (n + 1) -th sheet in FIG. 4,...)
Etc.). First, FIG. 9 shows the start of copying, and since there is no sheet in the intermediate unit 3 yet, the sheet is fed from, for example, the cassette 51, and the sheet is conveyed toward the photosensitive drum 48, and 1F-1 (1 The first copy on the front side of the document of the first sheet, the same applies hereinafter) is printed. After a predetermined cycle time, a determination is made for the next copy. In this case, however, there is no paper in the intermediate unit 3, so that paper is continuously fed from the cassette 51 as shown in FIG. It is. During that time, the preceding sheet passes through the fixing device 49 and is conveyed toward the duplex unit 101.

In the same procedure as described above, sheets corresponding to 1F-3 and 1F-4 are fed from the cassette 51 and printed (see FIGS. 11 and 12). By the way, in this example, since the number of copies is four, as shown in FIG. 13, after the front side copy of the sheet, that is, the printing of 1F-4 is completed, the sheet is moved to the refeed point indicated by X in the figure. Is reached, the re-feeding is performed from the intermediate unit 3 side. Then, since the sheet has already been turned over and the back side is exposed, the back side 1R of the sheet is shown in FIG.
-1 is printed. Further, at each cycle time, 1R-2 in FIG. 15 and 1R-
3. In FIG. 17, 1R-4 is printed. Further, after 1R-4 printing, the intermediate unit 3 runs out of paper, and automatically switches to paper feeding from the cassette 51.
Paper is fed as shown in FIG. By repeating such an operation, a plurality of copies can be obtained.

The conventional automatic document feeding (A
When displayed in the same way as for DF) ○ ○ ○ ○ △ △ △ △ ○ ○ …… 1F-1 1F-2 1F-3 1F-4 1R-1 1R-2 1R-3 1R-4 2F-1 2F- 2 …… | ← → | Although it can be expressed as ^{cycle time} , especially when the number of copies is small and only one copy is needed, for example, this concept is applied and the following operation is performed to obtain ○ ○ ○ ○ △ △ △ △ ○ ○ …… 1F-1 2F-1 3F-1 4F-1 1R-1 2R-1 3R-1 4R-1 5F-1 6F-1 …… As a result, the time lost as seen in the above means is eliminated, and it becomes truly efficient.

In this case, if all paper sizes are the same, when manual paper feeding is used, when a sensor detects that paper has been set in the manual paper feeding unit, basically when the manual paper feeding unit is used. Priority is given to paper feeding from the printer, so that the paper feeding operation is performed unless the sensor of the registration roller I detects that there is a paper before. That is, after the sheet is detected by the registration roller I, printing is performed on the sheet on the photosensitive drum 48, and the sheet is conveyed to the fixing device 49. Thereafter, the sheet is switched in the direction of the duplex unit 101, is conveyed to the exit side of the duplex unit 101 to perform printing on the other side, and the next sheet is not fed from the manual sheet feeding unit, and is located just before the registration roller I. Only when there is no sheet, the sheet is sent to the photosensitive drum 48 and printed, and the double-sided copy is completed. When the sheets are successively fed from the manual sheet feeding unit in this manner, the sheet is not fed from the duplex unit 101, and the sheet from the manual sheet feeding unit is preferentially fed. The one-sided copied paper stored in the intermediate tray 3 of 101 is on standby, and the paper is fed from the intermediate tray 3 when the presence of the paper is no longer detected in the manual paper feed unit.

However, if the automatic document feeder (ADF) 36 reads that documents of different sizes are mixed, paper of another size is automatically selected, and paper of that size is inserted. Switch to paper feeding from the cassette. In that case, the paper that has already been subjected to the one-sided copy stored in the intermediate tray 3 is preferentially fed and the backside copy is performed. When all the sheets stored in the intermediate tray 3 have been discharged, the next sheet is fed from the cassette, one side is copied as described above with reference to FIG. The matching operation described with reference to FIG. 7 is performed.

As described above, it is possible to carry out copying with excellent copy efficiency. When this is compared with the copy efficiency of the conventional system shown in FIG. Is highly dependent on the number of manuscripts, while the method of the present invention naturally depends on the number of copies, and the efficiency is further improved as compared with the conventional case. The dependence on the number of originals, which has no relation to the original, is remarkable, and the copying efficiency is rapidly increased. In other words, according to the method of the present invention, there are many points where the efficiency becomes 100% except for the case of a small number of combinations having both a small number of copies and a small number of document surfaces.

The copying efficiency according to the method of the present invention can be expressed by the following equation.

(Equation 3) Here, M is the number of original pages, N is the number of copies, P is a predetermined number, and A is the remaining number obtained by dividing M × N / 2 by the predetermined number P. If the remainder is 0, A = P. Therefore, if M × N is a multiple of P, the efficiency becomes 100
%. Here, the predetermined number is the length of the used paper divided by the length of the conveyance path from when the photoconductor drum 48 is conveyed to the photoconductor drum 48 again for copying the back side through the paper reversing path of the duplex unit 101. The upper limit value is used as the appropriate upper limit value. Usually, a value equal to or less than the upper limit value is used from the viewpoint of easy control. P = 5 as an example
FIG. 2 shows the relationship between the copy efficiency and the values of M and N in the case of
FIG. 19 shows a ternary graph as in FIG.
When FIG. 19 is compared with FIG. 21, it is clear that the case of the method of the present invention often increases the copying efficiency significantly closer to 100%.

[0037]

According to the present invention, it is possible to improve the copying efficiency by eliminating the loss time at the time of double-sided copying, and to store and feed different size papers in an intermediate tray so that they can be aligned. This makes it possible to provide an electrophotographic copying method that does not cause a paper feeding error or a skewed feed even if papers are mixed, and the effect is immeasurable. Also, the next paper size is
If the paper size is larger than the
When finished, move the trailing edge regulating plate to the next paper size.
So there is no need to move all regulated versions and it works
Enables quick movement with sound reduction and power consumption averaging
Can be.

[Brief description of the drawings]

FIG. 1 is a sectional view showing the entire structure of a copying machine used in the present invention.

FIG. 2 is a block diagram illustrating an image processing unit included in the copying machine of FIG.

FIG. 3 is an explanatory diagram illustrating an outline of a configuration of a duplex unit of the copying machine of FIG. 1;

FIG. 4 is a schematic diagram illustrating the operation of a sheet in the duplex unit in FIG. 3;

FIG. 5 is a plan view for explaining the concept of a matching unit.

FIG. 6 is a plan view of the alignment means of FIG. 5;

FIGS. 7A and 7B are schematic diagrams illustrating the operation of a side end regulating plate.

FIG. 8 is a flowchart illustrating an alignment operation.

FIG. 9 is a schematic diagram illustrating a paper feeding procedure in the duplex unit.

FIG. 10 is a schematic diagram illustrating a paper feeding procedure in the duplex unit.

FIG. 11 is a schematic diagram illustrating a paper feeding procedure in the duplex unit.

FIG. 12 is a schematic diagram illustrating a paper feeding procedure in the duplex unit.

FIG. 13 is a schematic diagram illustrating a paper feeding procedure in the duplex unit.

FIG. 14 is a schematic diagram illustrating a paper feeding procedure in the duplex unit.

FIG. 15 is a schematic diagram illustrating a paper feeding procedure in the duplex unit.

FIG. 16 is a schematic diagram illustrating a paper feeding procedure in the duplex unit.

FIG. 17 is a schematic diagram illustrating a paper feeding procedure in the duplex unit.

FIG. 18 is a schematic diagram illustrating a paper feeding procedure in the duplex unit.

FIG. 19 is a diagram showing the relationship between the number of originals and the number of copies in the present invention and the copying efficiency.

FIG. 20 is a flowchart illustrating a conventional duplex copying technique.

FIG. 21 is a diagram showing the relationship between copy efficiency and the number of original pages and the number of copies in a conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 paper holding plate 2 reversing paper guide 3 intermediate tray 4 side end regulating plate 5 rear end regulating plate 6 friction member 7 rack 8 pinion 101 duplex unit 30 copying machine 31 scanner unit 32 laser printer unit 33 multi-stage paper feed unit 34 sorter 35 original Mounting table 36 RDF 40 Scanner unit 51, 52, 53, 55 Cassette 45 Manual feed tray 46 Laser writing unit 47 Electrophotographic process unit 48 Photoconductor drum 49 Fixing unit 50, 56, 57, 58, 59, 60 61 Transport path 62 Junction point 70 Image data input unit 71 Image processing unit 72 Image data output unit 73 Memory 74 CPU I Registration roller DS1, DS2, DS3, DS4 Sensor DSOL1, SDOL2 Solenoid A, B Feeding roller C Separating roller D, E, F, G, H carry Roller DMOT pulse motor P recording paper (paper)

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-267245 (JP, A) JP-A-4-59573 (JP, A) JP-A-4-56970 (JP, A) JP-A-3-56945 54578 (JP, A) Japanese Utility Model 1-65231 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 15/00 510-534 G03G 15/00 106 G03G 15/00 303 G03G 15/36 G03G 21/00 370-540 G03G 21/02-21/04 G03G 21/14 G03G 21/20 B65H 83/00-85/00

Claims (1)

(57) [Claims] When performing double-sided copying by using an electrophotographic process in which copying paper sizes of different types can be mixed, one-sided copied paper is stored in an intermediate tray, and a movable side end regulating plate provided in the intermediate tray and a rear end regulating plate provided in the intermediate tray. When the aligning means including the end regulating plate performs an aligning operation for adjusting the posture of the single-sided copied paper, and detects that the next sheet having a different size from the single-sided copied paper has been conveyed toward the intermediate tray. In the electrophotographic two-sided copying method in which the one-sided copied paper is preferentially completed on both-sided copying and discharged, the detected next sheet is larger in size than the one-sided copied sheet stored in the intermediate tray. An electrophotographic double-sided copying method, wherein the rear end regulating plate is moved to the next sheet size when the alignment operation for the single-sided copied sheet is completed.