JPH0792746A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device of enhanced productivity for double-side image formation by reducing the loss of time required for image formation as much as possible even in the event of the retrying of refeed. CONSTITUTION:If refeed is retried, the time t4 required for starting the retry after a refeed error has been detected, is added to a normal inter-sheet time t2 during a flow in which sheets are put in a first-side copy intermediate tray. That is, when refeed is retried, sheets in a double-side conveying path 18 just before being ejected into the intermediate tray 19 are stopped for the period of time t4, to prefer a refeed flow to put sheets in the intermediate tray 19.

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 a printer or a copying machine, and more particularly to an image forming apparatus equipped with an intermediate stacking means for temporarily accommodating sheets having one side image formed thereon.

[0002]

2. Description of the Related Art Conventionally, as an image forming apparatus such as a copying machine, an apparatus equipped with a double-sided copying mode for performing double-sided copying on a sheet and a multiplex copying mode for performing multiplex copying has been used.
For example, in the copying machine shown in FIG. 5, the sheet S on which an image is formed by passing between the photosensitive drum 51 and the transfer charger 52.
Is guided to the fixing device 54 via the conveyor belt 53 and the toner image is fixed. In the double-sided copy mode and the multiplex copy mode, the inner discharge roller pair 55 or the outer discharge roller pair 56 temporarily stacks and stores them on the intermediate tray 58 via the re-feeding path 57a and the double-sided conveying path 57b. .

The structure of the double-sided transport path 57b and the intermediate tray 58 will be described. First, the double-sided transport path 57b is generally set to a sheet size in order to reliably stack and store sheets S of various sizes on the intermediate tray 58. A plurality of discharge ports are formed by rotating the sheet discharge flapper 59 accordingly. Further, discharge rollers 60 are provided corresponding to the discharge ports formed by the rotation of the sheet discharge flapper 59.

Further, in order to improve the stackability of the sheets S on the intermediate tray 58, a pair of side regulating plates 61 are provided in a direction (width direction) orthogonal to the sheet conveying direction. The sheet S is aligned in the width direction by reciprocating 61 in the width direction. That is, at the moment when the sheet S is discharged from the double-sided conveyance path 57b, the side regulation plate 61 waits in a state where the interval is the sheet width + α (α = 5 to 10 mm), and the sheet S is placed on the intermediate tray 58. Sheet width + β after being stored (β = 0 to 1 mm)
The sheet S is reciprocally moved to align the sheet S in the width direction. Further, when the sheet S stored on the intermediate tray 58 is re-fed for double-sided copying or multiple copying, the side regulating plate 61 has a space of sheet width + β for preventing skewing of the sheet S.
The feeding operation is performed in the closed state, and it also functions as a sheet guide. The opening / closing timing of the side regulation plate 61 is determined by detecting the leading edge of the sheet by the sheet detection sensor 62 provided on the upstream side of the double-sided transport path 57b and counting the sheet storage time with a timer.

In recent years, some copying machines equipped with the above-mentioned structure are equipped with the following structure in order to improve the productivity (copying speed) of double-sided or multiplex copying. That is, in general, when performing double-sided copying, the first document is surface-copied for a set number of sheets, then stored in the intermediate tray 58, the documents are exchanged, and then the sheet S on the intermediate tray 58 is re-fed. Then, the next original is often copied on the back side and discharged to a discharge tray (or sorter) outside the main body of the apparatus.

However, in the above configuration, it takes time from the intermediate tray 58 to re-feeding after the surface copying is completed, and the sheet interval time is increased during that time, so that the productivity of double-sided copying is not high. Further, when a two-sided copy of a stack of originals including an odd number of single-sided originals is made, a contradiction occurs in the page order of the sheet S after the double-sided copying is completed. In many cases, a configuration is provided in which the copy sequence is divided depending on whether the number of originals is an even number or an odd number.
For this reason, the original count time is added in addition to the copying operation, and the productivity of double-sided copying is reduced as a total job.

Therefore, in order to solve the above problem, when the sheets S stored in the intermediate tray 58 are re-fed, the sheet S is fed in order from the lowermost sheet S (hereinafter referred to as "lower separation feeding"). Productivity) of double-sided copying by adopting a "feeding system") and further by providing a sheet reversing path on the downstream side of the fixing device 54 and providing a discharge reversing mechanism for discharging the copy surface downward to the outside of the apparatus main body. Attempts have been made to improve.

Specifically, by adopting the lower separation feeding method, the first original is copied by the set number of sheets, and the lowermost part on the intermediate tray 58 is stored while being stored in the intermediate tray 58. Sheet S can be re-fed (first-out feed), and the time between the last sheet of the front side copying and the first sheet of the back side copying can be shortened.

Further, by providing the discharge reversing mechanism, the skip feeding described below can be performed, and the document counting by the ADF can be omitted. FIG. 6 shows a flow of the operation of feeding the original and the sheet at the time of skip feeding (FIG. 6 shows the case of 10 single-sided originals). The manuscript is 9, 7, 5, 3, in the first circulation as in the manuscript circulation flow by the ADF.
The first document is skipped without being copied, and the sheet S on which only the 10, 8, 6, 4, and 2 documents have been surface-copied is stored in the intermediate tray 58. The second and subsequent manuscript circulations are 10, 9,
8, ..., 2, 1 are performed one by one, and as shown in the second side copy intermediate tray discharge flow, 10, 7, 6, 4, and 2, 9, 7, 5, 3,
1 is copied and discharged outside the apparatus.

Further, 10, 8, 6, during the second document circulation
The sheets S obtained by surface-copying the originals 4 and 2 are stored in the intermediate tray 58 as in the case of the first surface-copying when the originals are circulated.
That is, when the document is circulated for the second time and thereafter, one sheet S for front side copying and one sheet S for back side copying are alternately fed toward the image forming means. Here, since the conventional document counting is performed at the same time as the first document circulation, the original document counting is unnecessary, and in the case of an odd number of documents, double-sided copying is performed by performing the reverse discharge using the discharge reverse mechanism. Sheets can be arranged without page order inconsistency.

Further, during the above-mentioned first-out feeding and skip feeding, the opening / closing timing of the side regulating plate 61 on the intermediate tray is earlier by t _{1 than} when the first side copy intermediate discharge tray is stored, as shown in FIG. The sequence is such that it opens at time and closes at time t ₃ earlier than when the second copy is discharged. By performing the opening / closing timing of the side regulation plate 61, stable sheet storage and sheet refeeding without skewing are possible.

[0012]

However, the above-mentioned prior art has the following problems.
In the first-out feeding and the skip feeding, basically, the sheet S is stored on the intermediate tray 58 and the sheet is re-fed at the same time. Therefore, the feed error of the sheet S is accumulated at a level that does not affect the jam detection timing. If the theoretical inter-sheet time t ₂ greatly fluctuates, the side regulation plate 61 closes when the sheet is stored, causing a storage failure of the intermediate tray 61, or the side regulation plate 61 opens when the sheet is re-fed and the rear surface is opened. The sheet S may be skewed during copying.

Further, when the sheet S on the intermediate tray 58 is re-fed, there is a bad condition such as curling of the sheet S itself, and a feed error is likely to occur, so a single feed error causes a jam. Although there are many apparatuses that employ the re-feed retry mode in which the feeding operation is performed again without the occurrence of (paper jam), the above-mentioned problem also occurs during this re-feed.

FIG. 7 is a flow chart showing a problem when a re-feed retry occurs. In the figure, "Second side copy intermediate tray discharge flow"
Is a normal re-feed flow without re-feed retry,
"Second side copy intermediate tray discharge flow 1" shows a flow when a feeding retry occurs. That is, the second side copy is performed with a delay of t _{4 with} respect to the normal re-feed flow,
At the time of copying the second side (during re-feeding), the side regulation plate 61 is open, and the skew of the sheet S is likely to occur.

Therefore, as shown in "Second side copy intermediate tray discharge flow 2" for a normal re-feeding flow as a response when a feeding retry occurs, only the sheet interval time t ₂ + sheet width time = t ₅ A mode in which refeeding is started after a delay (hereinafter referred to as “storage priority mode”) is provided to delay the refeeding flow in accordance with the opening / closing timing of the side regulation plate 61. However, from the viewpoint of further improving the productivity of double-sided copying, a stable re-feeding system that does not require the storage priority mode has been desired.

An object of the present invention is to solve the above-mentioned problems of the prior art and to provide an image forming apparatus in which the loss time required for image formation is minimized even when a re-feed retry occurs and the productivity of double-sided image formation is improved. To do.

[0017]

Representative means for solving the above-mentioned problems of the prior art and applied to the embodiments described below are an image forming means for forming an image on a sheet according to image information, and a single-sided means. Intermediate stacking means for temporarily storing the image-formed sheets, a plurality of transport path switching means for discharging sheets to the intermediate stacking means for each size, and a plurality of re-transporting means for transporting the sheets to the intermediate stacking means. A guide means for aligning the sheets on the intermediate stacking means, a re-feeding means for feeding the sheets from the intermediate stacking means to form an image on the sheet again, and a conveyance path switching means. A sheet detection unit corresponding to each conveyance path provided on the upstream side in the sheet conveyance direction, and the drive of the re-conveyance unit provided in each conveyance path is controlled independently of the drive of other units. Characterized by .

[0018]

According to the above-mentioned means, the driving of the re-conveying means provided in each conveying path for conveying the sheets to the intermediate stacking means is controlled independently of the driving of the other means. For example, a re-feeding retry mode is provided, and the re-conveying means is controlled to stop driving for a predetermined time by a feeding failure signal.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming apparatus using the above means will be described below with reference to the drawings. This embodiment will be described using a copying machine as an image forming apparatus. 1 is a cross-sectional explanatory view showing the re-conveying path, FIG. 2 is a top view showing the re-conveying path, FIG. 3 is a flow showing the sheet re-feeding operation, and FIG. 4 is a cross-sectional explanatory view showing the overall configuration of the copying machine. Is.

First, the schematic construction of the copying machine will be described with reference to FIG. Reference numeral 1 denotes a copying machine main body, and a feeding deck 2 accommodating a large amount of sheets S finely is provided on one side surface thereof. Further, a plurality of feeding cassettes 3 and 4 accommodating and storing a predetermined amount of sheets S are detachably mounted on the lower portion of the copying machine body 1.

At the locations where the feeding deck 2 and the feeding cassettes 3 and 4 are installed, feeding devices 5, 6 and 7 of the retard separation type are provided.
Is equipped with. The sheets S stacked in the feeding deck 2 and the feeding cassettes 3 and 4 are fed by the corresponding feeding devices 5, 6 and 7, respectively, and the nip portion of the registration roller pair 8 which is first stopped rotating. The slant is corrected by hitting against.

Next, the registration roller pair 8 which rotates at a timing with the latent image formed on the photosensitive drum 9 conveys the toner image between the photosensitive drum 9 and the transfer charger 10 to form a toner image from the photosensitive drum 9. The image is transferred to the sheet S (image formation). Then, the sheet S is conveyed to the fixing device 12 by the conveying belt 11, and heat and pressure are applied to the sheet S to fix the transferred image.

The copying machine according to the present embodiment is equipped with a double-sided copying mode for performing double-sided copying on the sheet S and a multiplex copying mode for performing multiplex copying. In the normal copying mode, the sheet S after the fixing process is conveyed and discharged by the inner discharge roller pair 13 and the outer discharge roller pair 14 to the discharge tray 15 provided outside the apparatus. In the double-sided copy mode and the multiplex copy mode, the sheet is temporarily discharged onto the intermediate tray 19 by the inner discharge roller pair 13 or the switchback roller pair 16 via the re-feed path 17 and the double-sided transport path 18.

Here, the double-sided conveying path 18 and the intermediate tray 19
The configuration will be described with reference to FIGS. 1 and 2. Figure 1
At S, the sheet S on which the image has been formed by passing between the photosensitive drum 9 and the transfer charger 10 is guided to the fixing device 12 via the conveyance belt 11 and the toner image is fixed. In the double-sided copy mode and the multiplex copy mode, the sheet is temporarily discharged onto the intermediate tray 19 via the re-feeding path 17 and the double-sided conveying path 18.

The structure of the double-sided conveyance path 18 and the intermediate tray 19 will be described.
In order to securely stack and store sheets S of various sizes on top, a sheet discharge flapper is generally used according to the sheet size.
A plurality of discharge ports are formed by rotating 20. Further, intermediate discharge rollers 21 are provided corresponding to the discharge ports formed by the rotation of the sheet discharge flapper 20.

In order to improve the stackability of the sheets S on the intermediate tray 19, a pair of side regulating plates 22 are provided in a direction (width direction) orthogonal to the sheet conveying direction. The sheet S is aligned in the width direction by moving the 22 back and forth in the width direction. That is, at the moment when the sheet S is discharged from the double-sided conveyance path 18, the side regulation plate 22 has a space of sheet width + α (α = about 5 to 10 mm).
When the sheet S is stored in the intermediate tray 19, the sheet S is accommodated on the intermediate tray 19 and reciprocally moved to close the sheet width + β (β = 0 to 1 mm) to align the sheet S in the width direction. Further, when the sheet S stored on the intermediate tray 19 is re-fed for double-sided or multiple copying, the side regulating plate is used.
In order to prevent the skew of the sheet S, the sheet 22 performs the feeding operation in a state where the interval is closed to the sheet width + β, and also serves as a sheet guide. The side regulating plate 22 is opened and closed by detecting the leading edge of the sheet by the sheet detection sensor 23 provided on the upstream side of the double-sided conveyance path 18 and counting the sheet storage time with a timer. In addition, in FIG. 1, 25
Is a re-feed roller for feeding the sheet S from the intermediate tray 19,
26 is a re-conveying roller pair.

The drive of the intermediate discharge roller 21 is transmitted from the dedicated motor 24 shown in FIG. 2, and the drive is controlled independently of the other drive system of the apparatus. That is, when the sheet S is being conveyed in the conveying path upstream of the double-sided conveying path 18 in the sheet conveying direction, the sheet S inside the double-sided conveying path 18 can be stopped and controlled. Further, in order to reliably detect the sheet position inside the double-sided transport path 18 for each size, sheet detection sensors 23 are arranged upstream of the plurality of sheet discharge flappers 20.

A re-feeding flow of the sheet S using the above structure will be described with reference to FIG. In FIG. 3, "Second side copy intermediate tray discharge flow" is a normal re-feed flow without re-feed retry, and "Second side copy retry intermediate tray discharge flow 2" is a storage priority mode during re-feed retry. It is a re-feeding flow by. Further, "Intermediate tray discharge flow 1 at the time of copy retry for the second side" shows the re-feeding flow in this embodiment.

The present embodiment is different from the conventional example in that
First side copy intermediate tray normal sheet between the time t ₂ in the flow, the refeeding retry occurs during the time obtained by adding the time t ₄ until the refeed retry start from the refeed FDC t ₂ +
It's about to be t ₄ . That is, when re-feed retry occurs, the sheet S inside the double-sided transport path 18 immediately before being discharged to the intermediate tray 19 is stopped for t ₄ and re-feed as in the conventional storage priority mode (see FIG. 7). The sheets are stored in the intermediate tray 19 by prioritizing the re-feeding flow without delaying the flow (hereinafter, referred to as "re-feeding priority mode").

[0030] Incidentally, when performing this embodiment, the sheet S double-sided conveying path 18 upstream with respect to the stopping time t ₄ so as not keep up with the sheet S is stopped normal stop time t _2, t ₂ It is necessary to maintain the relation that> t ₄ .

According to the above construction, by providing the re-feeding priority mode, the re-feeding flow time can be shortened by t ₅ -t ₄ as compared with the conventional storage priority mode, and at the time of double-sided copying. Productivity can be improved.

Although the intermediate discharge roller 21 provided in the double-sided transport path 18 is driven by the dedicated motor 24, the same effect can be obtained by replacing the driving means with an electromagnetic clutch or the like.

[0033]

As described above, according to the present invention, by providing the re-feeding priority mode, the loss time required for image formation is minimized even when the re-feeding retry occurs, and the productivity of double-sided image formation is improved. be able to.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view showing a double-sided conveyance path.

FIG. 2 is a top view showing a double-sided conveyance path.

FIG. 3 is a flowchart showing a sheet re-feeding operation.

FIG. 4 is a cross-sectional explanatory diagram showing an overall configuration of a copying machine.

FIG. 5 is an explanatory cross-sectional view showing a conventional double-sided conveyance path.

FIG. 6 is a conventional document circulation and re-feeding flow.

FIG. 7 is a conventional document circulation and re-feeding flow.

[Explanation of symbols]

 S ... Sheet 1 ... Copying machine main body 2 ... Feeding deck 3,4 ... Feeding cassette 5, 6, 7 ... Feeding device 8 ... Registration roller pair 9 ... Photosensitive drum 10 ... Transfer charger 11 ... Conveyor belt 12 ... Fixing Device 13 ... Inner discharge roller pair 14 ... Outer discharge roller pair 15 ... Discharge tray 16 ... Switchback roller pair 17 ... Refeed path 18 ... Double-sided conveyance path 19 ... Intermediate tray 20 ... Sheet discharge flapper 21 ... Intermediate discharge roller 22 ... Side regulation plate 23 ... Sheet detection sensor 24 ... Exclusive motor 25 ... Refeed roller 26 ... Refeed roller pair

Claims (4)

[Claims] 1. An image forming unit for forming an image on a sheet according to image information, an intermediate stacking unit for temporarily storing the sheet on which one-sided image is formed, and a sheet for each size discharged to the intermediate stacking unit. A plurality of conveying path switching means, a plurality of re-conveying means for conveying the sheet to the intermediate stacking means, a guide means for aligning the sheet on the intermediate stacking means, and for performing image formation on the sheet again Re-feeding means for feeding sheets from the intermediate stacking means, and sheet detecting means corresponding to each transport path provided on the upstream side in the sheet transport direction of the transport path switching means, The image forming apparatus is characterized in that the re-conveying means provided is driven independently of the driving of other means. 2. When the sheet stored in the intermediate stacking member is re-fed to the image forming unit and a feeding failure occurs, the feeding operation is repeated without displaying the fact immediately. 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is equipped with a feeding retry mode, and the driving of the re-conveying means is stopped by a feeding failure signal. 3. The image according to claim 2, wherein the driving of the re-conveying means is stopped and controlled for a time t ₄ from detection of a feeding failure during re-feeding to the start of re-feeding retry. Forming equipment. 4. The time t ₄ from the detection of the feeding failure during the re-feeding to the start of the re-feeding retry is t ₂ > t ₄ with respect to the normal sheet interval time t ₂ . The image forming apparatus according to claim 3.