JPH11161039A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of efficiently executing the feed control of a recording material to a joint not only at the time of forming an image on one surface side (1st face) but also at the time of forming the image on the both surface sides (2nd face). SOLUTION: The feed control of a recording material to a joint 5a of a recording material carrier means 5 is performed for every number of the recording material which can be arranged on the peripheral length of the means 5 in accordance with the length of the carrying direction of the recording material. Thus, more efficient and easier control is executed in comparison with the case that the feed control of the recording material is performed for every different size. Desirably, it is good to satisfy L1+L2=N×LS+Li when it is assumed that the length except a paper reversing part of a circulation path is L1+L2, the peripheral length of the recording material carrier means 5 is Ls, the specified space of the recording material is Li and N is an integer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic system or an electrostatic recording system capable of forming an image on both sides of a recording material, for example, having a plurality of image forming means. A plurality of images of different colors are formed on the respective image carriers by the image forming means, and these images are sequentially transferred onto the same recording material carried and conveyed by the recording material carrying means. The present invention relates to a color image forming apparatus such as a color copying machine and a color printer.

[0002]

2. Description of the Related Art In an image forming apparatus provided with an endless transfer belt having a seam, when a recording material is carried at a seam position and an image is transferred from the photoconductor, transfer loss occurs and an image defect occurs. It may be.

Therefore, in order to prevent this, a mechanism for detecting a seam is provided in advance, and the seam is detected, and based on the result and the recording material size, the recording material is applied to the transfer belt so as not to be placed on the seam. An image forming apparatus that controls feeding has been proposed (for example, Japanese Patent Application Laid-Open No. H5-2347).

[0004]

However, in the conventional image forming apparatus having the above-mentioned structure, no consideration is given to the case where an image is formed on both sides of a recording material such as a double-sided copy or a double-sided print. Was.

Accordingly, the present invention provides an image capable of efficiently controlling the feeding of the recording material to the seam not only when forming an image on one side (first side) but also when forming an image on both sides (second side). An object is to provide a forming apparatus.

[0006]

An object of the present invention is to provide an image bearing member on which an image is formed and a recording material formed in an endless shape having a joint and onto which the image formed on the image bearing member is transferred. And a circulating path for reversing and circulating the recording material to form images on both sides of the recording material, and transferring the image on the image carrier at the transfer position to the recording material. Transfer means for transferring the recording material to the recording material carrying means, and a plurality of recording materials can be fed onto the recording material carrying means at intervals, in accordance with the length of the recording material in the conveyance direction, The problem is solved by an image forming apparatus characterized in that the feeding control of the recording material to the joint of the recording material carrying means is performed for each number of recording materials that can be arranged in the circumference of the recording material carrying means.

As described above, by controlling the feeding of the recording material to the seam of the recording material supporting means for each number of recording materials which can be arranged in the circumferential length of the recording material supporting means, the feeding of the recording material for different sizes is performed. Efficient and simple control can be performed as compared with the case where transmission control is performed. Specifically, for example, for each of the number of recording materials that can be arranged in the circumferential length of the recording material holding means, for the substantially longest recording material that can be fed while avoiding the seam with the number of recording materials, The position of the recording medium is determined in advance, and when feeding the same number of recording materials of other sizes, the leading end of the recording material is adjusted to the predetermined position of the leading end of the substantially longest recording material. Just send it.

Preferably, the length of the circulation path excluding the sheet reversing portion is L1 + L2, the peripheral length of the recording material supporting means is Ls, the interval between predetermined recording materials is Li, and the peripheral length of the recording material supporting means is L1 + L2. When Ls and N are integers, L1 + L2 = N × LS.
It is good to set to + Li.

Thus, it is not necessary to stop unnecessary conveyance of the recording material on the second side which has been reversed and circulated in order to avoid a seam.

[0010]

FIG. 1 shows a main part of image formation in an electrophotographic full-color copying machine according to an embodiment of the present invention. The present invention is equally applicable to image forming apparatuses having various configurations such as an electrophotographic system and an electrostatic recording system other than the embodiment.

This image forming apparatus has four image forming sections Pc, Pm, Py, and Pk in the apparatus, and a sheet feeding section 1 is disposed below the image forming sections, and a fixing device 2 is disposed on the left side. Further, a sorter 3 is disposed on the left side of the fixing device 2. This sorter 3
Has a staple function and a shift tray function.

A circulating path 9 for circulating and conveying the paper is formed between the paper feeding section 1 and the fixing device 2.
In a position between the sheet and the sorter 3, the circulation path 9 is provided with a sheet reversing section 9a for reversing and discharging the sheet. The sheet reversing section 9a also serves as a means for switching between discharging the sheet as a recording material to the sorter 3 and guiding the sheet to the circulation path 9 for backside copying.

An endless transfer belt 5 as a recording material carrying means for carrying and carrying the sheet is provided below a plurality of rollers (not shown) below the carrying path from the sheet feeding section 1 to the fixing device 2 in a well-known manner. Is suspended between them.

The transfer belt 5 is driven in the direction of the arrow, carries the paper fed through the paper feed unit 1, and sequentially transports the paper to the image forming units Pc, Pm, Py, and Pk.

Each of the image forming units Pc, Pm, Py, and Pk has substantially the same configuration, and is a photosensitive drum 6c, 6m, 6y, 6c as an image carrier that is driven to rotate in the direction of the arrow shown in the figure.
6k, and image forming means (not shown) are arranged around each photosensitive drum.

Although any structure can be adopted as these image forming means, in this embodiment, each photosensitive drum 6c,
Charging charger for uniformly charging 6m, 6y, 6k,
A developing device for developing the electrostatic latent image formed on each photoconductor drum, a transfer charger for transferring the developed toner image to paper, and a cleaner for removing toner remaining on the photoconductor drum are provided for each photoconductor drum. They are arranged sequentially in the direction of rotation. Image exposure devices 7c, 7m, 7y, and 7k are provided above the photosensitive drums 6c, 6m, 6y, and 6k.

The developing unit of the image forming unit Pc contains cyan toner, the developing unit of the image forming unit Pm contains magenta toner, the developing unit of the image forming unit Py contains yellow toner. Black toner is stored in each of the developing devices of the unit Pk.

Each of the image exposure devices 7c, 7m, 7y, and 7k includes a semiconductor laser, a polygon mirror, an fθ lens, etc., receives an electric digital image signal, and charges a laser beam modulated according to the signal. Charger,
The photosensitive drums 6c, 6m, 6y, and 6k are scanned in the generatrix direction between the photosensitive drums 6c, 6m, 6y, and 6k to expose the drum surface to form an electrostatic latent image on each photosensitive drum. The image signal corresponding to the cyan component of the color image is supplied to the image exposure device 7c of the image forming unit Pc, and the image signal corresponding to the magenta component of the color image is supplied to the image exposure device 7m of the image forming unit Pm. The image exposing device 7y receives an image signal corresponding to the yellow component of the color image, and the image exposing device 7k of the image forming unit Pk receives an image signal corresponding to the black component of the color image. A paper suction unit (not shown) is provided between the paper feeding unit 1 and the paper feeding unit 5 to reliably suck the paper supplied from the paper feeding unit. On the other hand, a static eliminator (not shown) is provided between the image forming unit Pk and the fixing device 2, and the static eliminator separates the sheet adsorbed on the transfer belt 5.

The transfer belt 5 is semiconductive (or conductive).
The end portions of a film sheet made of a resin having the following characteristics are joined endlessly by means of fusion or the like, and are driven endlessly at a constant speed in a direction indicated by an arrow by a driving roller (not shown). Since the endless seam has a belt thickness different from that of the other parts of the belt, it adversely affects the reliable transfer from the photosensitive drums 6c, 6m, 6y, and 6k to the sheet. Therefore, when the paper is supplied to the transfer belt 5, it is necessary to control the supply of the paper so that the paper is not placed on the joint, as described later.

The paper supply section 1 is provided with a plurality of paper supply ports 1a to 1d in which a paper supply cassette for storing paper sheets of different sizes and a manual feed tray are set, and papers are supplied one by one from each paper supply port. And a timing roller 8 for feeding the paper fed from the paper feed port onto the transfer belt 5 at a predetermined timing.

In the full-color copying machine shown in FIG. 1, when a sheet is guided by a sheet feed guide and conveyed onto the transfer belt 5, the sheet is electrostatically reliably placed on the transfer belt 5 by the action of the sheet suction means. Is adsorbed. Then, as the transfer belt 5 moves in the direction of the arrow, the image forming portion Pc
A visible image of cyan (C) on the photosensitive drum 6c of
A magenta (M) visible image is formed on the photosensitive drum 6m of the image forming unit Pm.
y is a yellow (Y) visible image in the image forming unit Pk.
A black (K) visible image is shared and formed on the photosensitive drum 6k. These visible images are transferred to the image forming units Pc, Pm,
While being conveyed in the direction of the fixing device 2 while sequentially passing under the photosensitive drums 6c, 6m, 6y, and 6k of Py and Pk,
The image is transferred onto the paper by the transfer chargers of the respective image forming units, and a color image is synthesized. After the paper has passed through the image forming unit Pk, the charge is removed by the charge removing charger,
The paper is separated from the transfer belt 5. The sheet separated from the transfer belt 5 is discharged to the sorter 3 after the transferred multiple composite image is fixed by the fixing device 2.

Alternatively, in the case where the back side copy is further performed for the two-sided copy, the sheet is turned over by the sheet reversing section 9a without being discharged to the sorter 3, and then conveyed to the circulation path 9, where it is transferred to the back side of the sheet in the same manner as described above. After image formation,
It is discharged to the sorter 3.

Thus, a series of copying cycles is completed.

FIG. 2 shows a part of the operation panel 200 of the full-color copying machine shown in FIG. The copier is
By using the operation panel 200, various copy modes can be set and a copy operation can be started, and the setting status of the copy mode and the like and the device status can be known by the display.

A copy number setting unit 201 sets the number of copies,
Alternatively, it is a key group for clearing the set number of copies.

A print key 202 is a key for starting a copy operation, and a copy interrupt key 203 is a key for interrupting a copy operation during operation.
Reference numeral 04 denotes a key for adjusting the density of an image to be copied.
A magnification setting key 205 is a key for setting the magnification of the image to be copied, and a color mode selection key 206 is a key for setting whether to print the color of the image to be copied in full color or in black. .

A double-sided key 207 is a key for setting whether to print an image to be copied on only one side or both sides of a sheet. A key for selecting which cassette of the paper feed cassettes to use for the copy operation.

The number display section 210 is a display section for displaying the set number or the number of remaining copies during a copy operation. The magnification display section 211 is a display section for displaying the set magnification, and a liquid crystal display. A unit 212 is a multipurpose display unit that displays a lot of information such as various set copy modes and the state of the apparatus, other than the number of magnifications.

FIG. 3 is a block diagram showing the overall control of the full-color copying machine shown in FIGS.

The full-color copying machine includes an image reader (IR) for reading image information of a document as a function of the copying machine, in addition to an image forming main portion and a panel portion described in detail in FIGS. A document feeder (ADF) that feeds and conveys the originals one by one to an image reading unit of an image reader sequentially. However, the configuration is not limited to this.

A system controller 301 is a control section that controls the entire image forming apparatus.

The ADF control unit 302 feeds and conveys the documents one by one to the image reading portion of the image reader, and when the image reading is completed, discharges the document to the document discharge unit so that the document is fed to the document discharge unit. Is a control unit that controls

The IR control section 303 is a control section for controlling the scanning speed and position of the scanner for reading the image of the document.

The image processing control unit 304 controls the multi-memory image processing unit 312 according to the copy sequence and the copy mode.
Is a control unit for giving an operation instruction and the like. Specifically, control for recording the image signal processed by the scanner image processing unit 311 on a page basis of the document, and selection of the stored image signal of the page basis document in an order according to the copy sequence, Control for sending the image signal to the gradation processing unit 313 and control for rotating the image direction by 90 degrees or 180 degrees according to a copy mode or the like are performed.

The panel control unit 305 is a control unit that performs key input processing and display of the operation panel 200 as described with reference to FIG.

A mechanical control unit (hereinafter, referred to as a “mechanical control unit”) 306 controls the sheet feeding and conveyance and the control of the transfer belt 5 described with reference to FIG.
Control of 6y, 6k and peripheral image forming means, fixing unit 2
It is a control unit that performs control such as the above. Details will be described later.

The sorter control unit 307 is a control unit for controlling sheet transport / discharge in the sorter 3, moving bins, controlling the position of the shift tray, and controlling the stapling operation.

The image input unit 310 includes a sensor unit such as a CCD for reading an image of a document and a circuit unit for digitizing the signal. In this embodiment, the CM
It has a circuit configuration that simultaneously processes each component of YK.

The scanner image processing unit 311 includes a circuit for performing a scaling process, an image shift process, and an erase process on a digitized image signal according to a copy mode or the like. The multi-memory image processing unit 312 includes a memory for storing image information and a circuit for rotating an image or compressing and expanding an image.

The gradation processing unit 313 is composed of a circuit for performing conversion (such as conversion from eight gradations to three gradations) into gradation data according to the circuit configuration.

The frame memory 314 is composed of a circuit for temporarily storing image signals of a plurality of pages at the time of double-sided copying, and outputting image signals of a required page at a required timing.

The registration correction unit 315 calculates the color image C
The image signal corresponding to each of the MYK components is constituted by a circuit which delays the image signal by a time corresponding to a timing shift in which the sheet sequentially passes under the image forming units Pc, Pm, Py, and Pk. With this circuit, the image signals of the respective CMYK components can be simultaneously processed in parallel from the image input unit 310 to the gradation processing unit 313 or the frame memory 314.

The image exposure device 316 includes reference numerals 7c and 7 in FIG.
m, 7y, and 7k, and the photoconductors 6c, 6m, and 6 corresponding to each of the CMYK components in accordance with the corresponding image signals.
and a circuit for forming an electrostatic latent image on y and 6k.

Next, the feeding timing when the paper is fed onto the transfer belt 5, which is a main part of the present invention, will be described.

First, the timing control for transporting the sheet to the transfer belt 5 while avoiding the seam will be described.

FIG. 4 is a diagram showing a configuration of a portion near the timing roller 8 and the transfer belt 5. As shown in FIG. 4, the photosensitive drum 6c in the rotation direction of the transfer belt 5
A seam detection sensor 10 for detecting a seam 5 a of the transfer belt 5 is provided at a predetermined position on the upstream side of the transfer belt 5. Here, the time for transporting the sheet from the timing roller 8 to the lower portion of the photosensitive drum 6c in the first image forming section Pc is defined as Tt, and the sheet supply of the timing roller 8 is started from the timing of requesting the image processing circuit to send an image signal. Assuming that a time equal to or longer than the time until the start is α, the joint detection sensor 10 determines that Tb = Tt ′ + α with respect to the photosensitive drum 6c.
(Where Tt ′ = Tt).

Therefore, when the time α has passed after the seam detection sensor 10 detects the seam 5a (the seam 5a is
When the sheet is fed to the transfer belt by driving the timing roller 8 at the point A), the timing at which the seam 5a coincides with the leading end of the sheet is reached. However, the seam 5a of the transfer belt 5 actually has a certain width,
The width is assumed to be extremely small and zero, and the seam position is assumed to be the same as the reference of the leading end of the sheet (paper reference).

If the length of the sheet / system speed is Tp, and the point upstream of the point A by Tp is point B, the sheet conveyed to the timing roller 8 is supplied to the transfer belt 5 by the transfer belt. This is performed only when the fifth joint 5a does not exist between the point B and the point A. This is the basic idea of this control. That is, point A is the timing when the leading edge of the sheet matches the seam 5a as described above, point B is the timing when the trailing edge of the sheet matches the seam 5a,
This is because if the sheet is supplied at a timing when the seam exists between the point and the point A, the sheet is put on the seam.

Next, control for performing double-sided copying will be described.

In the double-sided control, the sheet must be conveyed while avoiding the seam even for the sheet which is conveyed in reverse circulation. However, in order to avoid the sheet, the sheet is stopped unnecessarily or the sheet interval is increased. This leads to a decrease in productivity.

First, a description will be given of a two-sided conveying mechanism for preventing the productivity from lowering. If the circulation path length satisfies the following condition, as will be described later, the reversely circulated sheet on the second side is also required to avoid a seam. It is not necessary to stop necessary conveyance.

L1 + L2 = N.times.Ls + Li (Letter Y) where L1: distance from timing roller 8 to reversal point P in circulation path 9 L2: distance from reversal point P to timing roller 8 in circulation path 9 Ls: transfer belt Perimeter Li (letterY): paper interval on the transfer belt of horizontally traversing letter-size paper N: integer or even integer In the above, the reversal point P is, as shown in FIG. The position of the sheet sent from the fixing device 2 is the position of the trailing edge of the sheet during the pause and reversal (after the reversal, the trailing edge of the sheet becomes the leading edge).

For the sake of simplicity, the description will be made on the assumption that N = 3. Ls = 3 × ３Lp (LetterY) + Li
(LetterY)｝. Here, Lp (Letter Y) is the length in the traveling direction of the transverse letter-size paper, and Y means transverse. This equation is a relational equation for improving the utilization efficiency of the transfer belt when the paper sheet is continuously fed and conveyed in a transversely sized letter size (see JP-A-6-35261).
This means that three transverse letter size papers are arranged on the transfer belt.

The idea is that if the time for temporarily stopping at the position of the timing roller 8 is extremely long, it is impossible to stop the sheet near the fixing unit 2 from the timing roller 8, so that the sheet near the fixing unit and the downstream side Papers overlap. Therefore, the number of sheets that can be incorporated in the two-sided path is 1 /
It is limited to about 2 and it is not possible to increase the productivity on both sides.

Therefore, in order to increase the productivity, it is preferable to minimize the pause time at the optimum paper interval.

In order to realize this, it is necessary to satisfy the following conditions.

1. The length of the circulating path on both sides is such that the sheet which has been reversely circulated and conveyed again to the timing roller 8 can be conveyed again from the timing roller 8 without stopping other than the primary stop for skew correction.

2. The paper feeding interval control of the first side is performed so that the paper recirculated and conveyed again to the timing roller 8 is only temporarily stopped for skew correction.

The details are as follows.

Assuming that image formation is performed one by one for each sheet that can be stored in the circulation path 9, as shown in FIGS. 5 (a) and 5 (b), the first sheet placed on the transfer belt 5 immediately after the joint 5a May be any length as long as it can be placed immediately after the seam when it is placed on the transfer belt 5 again via the circulation path 9 on both sides. To this end, the length of the circulation path 9 (L1 + Lp +
L2) must be an integral multiple of the circumference of the transfer belt 5. However, since the circulation path length varies depending on the paper size Lp, the above conditions cannot be satisfied for papers of all sizes. Also, it is difficult to realize a device that can variably set the circulation path length to be an integral multiple of the circumference of the transfer belt 5 according to the paper size.

However, the circulation path length (L1 + Lp + L2)
Focusing on only the element (L1 + L2) that does not depend on the paper, and assuming that (L1 + L2) is an integral multiple of the circumference of the transfer belt 5, as shown in FIGS. 9 is conveyed to the transfer belt 5 at the joint 5
a is shifted backward by the sheet length Lp.

Here, 3 shown by a black triangle in FIG.
The position of Ls + Lp is the length of the reversal circulation path on both sides, but 3Ls = L1 as shown in FIGS.
If + L2 -Li, the positional relationship between the transfer belt 5 and the sheet is the same on the first side and the second side. This means that when the sheet conveyed through the circulation path 9 is again placed on the transfer belt 5, the sheet can be conveyed around the joint 5a without unnecessary stoppage.

The paper-dependent elements are absorbed not by the length of the circulation path but by the distance (*) between the paper on the second side and the transfer belt joint 5a shown in FIG. Can be corrected by the relationship between the second sheet and the transfer belt. That is, the circulation path length is (L1 + Lp + L2), and Lp is generated because the leading edge and the trailing edge of the sheet are switched at the reversing portion. This is the distance (*) between the transfer belt and the seam 5a, and the positional relationship between the transfer belt 5 and the paper is changed by changing the distance (*) according to the paper size even if the paper size is different. Is the same.

However, since the sheet interval Li on the first side for avoiding the seam 5a of the transfer belt 5 is not constant for all the sheets, it is necessary to control the sheet interval on the first side in consideration of the sheet interval on the second side. Becomes

The paper interval Li will be described. Here, as the paper, the paper whose productivity is most desired, in other words, the paper that is frequently used is mainly considered. In general,
Letter size paper and JIS A4 size paper are the most frequently used, and this embodiment mainly considers this.

In this embodiment, the peripheral length Ls of the transfer belt
Is set to 960.47 mm. For this perimeter, three sheets can be arranged for the transfer belt perimeter in the case of horizontal letter size paper and horizontal letter A4 size paper, but in the case of horizontal letter size paper, the paper length in the transport direction is larger. Is long (the paper interval is small), and therefore, letter-size paper is used as a basis.

Assuming that the letter-size paper is evenly arranged on the transfer belt, the paper interval is Li (LetterY) = (Ls / 3) -Lp. Note that Li (Letter Y) is an average sheet interval on the transfer belt 5, and the sheet stops at the time of skew correction on the second surface, so that the sheet interval is narrowed at this stop. When the paper interval is narrowed, it is a condition that a minimum necessary paper interval can be secured.

The following explanation is based on the assumption that the circulation path length is L1 + L2 =
The process proceeds assuming that the relationship of N × Ls + Li (LetterY) is set.

In order to make transverse A4 size paper equivalent to transverse letter size paper, as shown in FIGS. 6 (a) and 6 (b), the leading edge of the paper on the belt is positioned at the leading edge of the transverse letter size paper. The paper interval has the same layout as that of. The paper interval is as follows.

Li (A4Y) = Li (Letter Y) + (2
(97 mm-11 inches) Other sizes of paper that can be arranged three times in the circumferential length of the transfer belt can be similarly considered. As can be understood from the above, with respect to the paper having a size that can be arranged three times in the circumferential length of the transfer belt, the paper whose length in the transport direction is substantially the longest is not placed on the first and second sides of the seam. If the position of the leading edge of the sheet is determined in this way, for a sheet having a shorter length, the leading edge may be fed in accordance with the determined leading edge position of the sheet, and control is simplified. Be transformed into

Next, for example, vertical letter size paper (Le
tterT) or vertical A4 size paper (A4T)
A description will be given of a sheet of a size that can be arranged two sheets in the transfer belt circumferential length. Since the length of the A4 size paper is longer in the transport direction than the length of the letter size paper, the A4 size paper will be described as an example.

As shown in FIGS. 7 (a) and 7 (b), when the second sheet conveyed along the circulation path 9 is again placed on the transfer belt 5, of the two sheets placed on the transfer belt circumference, The sheet interval is controlled as follows during sheet feeding and conveyance of the first side so that the joint 5a is positioned between the first sheet A and the subsequent sheet B.

That is, as shown in FIG.
A and the next paper B that are fed immediately after
Is Li1, and the distance between paper B and the next seam 5a is Li2.
Then, Li1 = Ls − ((Lp (A4T) + Li (LetterY))
+ Lp (A4T)) Li2 = Ls- (Lp (A4T) + Li1 + Lp (A4
T)) By controlling the sheet interval in this way, the sheet on the second side is fed to the transfer belt avoiding the seam 5a.

As for the vertically sized letter-size paper and the other sized paper which can be arranged two sheets in the length of the transfer belt circumferential length, the paper leading edge is considered to be the same as the above-described widthwise A4 size paper.
What is necessary is just to feed the paper in the same position as the leading end of the four size paper.

Next, a description will be given of a sheet of a size that can be arranged only one per circumference of the transfer belt, such as a sheet of 11 × 17 inch size or A3 size sheet. Note that the length of the 11 × 17 inch size paper in the transport direction is longer than the length of the A3 size paper in the vertical direction.

As shown in FIG. 8A, when the sheet is fed so that the leading end of the sheet is located immediately after the seam, the circulation path 9
Is conveyed to the seam.
This can be explained by the following equation. As shown in FIG. 8B, assuming that the distance from the rear end of the second sheet to the next seam is Lx, Lx = Ls − ((Lp (11 × 17T) + Li (Letter)
Y)) + Lp (11 × 17T)) By substituting specific numerical values, Li (LetterY) = (960.47 / 3) −8.5 × 2
Since 5.4 = 104.26, Lx = 960.47 − ((17 × 25.4 + 104.26) + 17 × 25.4) = 960.47−968.86 = −7.39 <0 Since the value of Lx becomes negative, the sheet on the second side is put on the joint 5a.

Then, as shown in FIGS. 8C and 8D,
The first-side sheet is fed to the transfer belt at a distance Ly represented by the following equation from the joint 5a so that the second-side sheet is placed immediately after the seam.

Ly = Ls− (Lp (11 × 17T) + L
i (LetterY)) In this case, the distance Lx between the trailing edge of the first sheet and the next seam is Lx = Ls− (Lp (11 × 17T) + Li (LetterY)) = Ls− (Ls− ( Lp (11 × 17T) + Li (LetterY)) + Lp (11 × 17T)) = Li> 0, and the first sheet is not placed on the next joint.

Similarly, for the A3 size vertical paper or other size paper in which only one sheet can be arranged for the circumference of the transfer belt, the leading edge position of the 11 × 17 inch vertical paper is similarly set. What is necessary is just to feed in a form which matches.

As described above, for each number of sheets that can be placed on the peripheral length of the transfer belt 5, the transfer belt is basically set to a sheet that is substantially the longest in a range that can be fed while avoiding seams. Is determined, the feeding control can be performed for the paper of another size based on the above-mentioned basic paper, and the paper on the first side is conveyed along the circulation path 9 as well as the paper on the first side. The second sheet can also be fed while avoiding the joint of the transfer belt.

The above description is based on the paper interval Li (LetterY) when three transversely sized letter-size papers are placed on the circumference of the transfer belt.
Although the position of the first sheet is determined by using (tterY), the present invention is not limited to this.

Up to this point, a case has been described in which image formation is performed one side at a time for each number of sheets that can be stored in the circulation path 9. Next, the first sheet and the second sheet conveyed through the circulation path 9 will be described. A case where paper and paper are alternately fed to the transfer belt will be described.

In order to alternately feed the first-side sheet and the second-side sheet, a sheet interval may be provided so that the second-side sheet can be placed between the first-side sheets.

As shown in FIGS. 9 (a) and 9 (b), for example, in the case of a horizontally sized letter size sheet, Li (LetterY) = ((Ls / 3) -Lp) × 2 + Lp
(Letter Y) The sheet on the first side is conveyed at the sheet interval, and is conveyed on the reversal circulation path 9 at the sheet interval and is again placed on the transfer belt 5,
Image formation on the second side is performed. Then, the next sheet on the first side is inserted again between the sheets placed on the transfer belt.

At this time, in the case of a transversely piercing letter-size sheet on which an odd number of sheets (three sheets in this embodiment) are placed for one rotation of the transfer belt, L1 + L2 = N × Ls + Li (Letter)
If N is an odd number in (Y), FIG.
= 3, as shown in FIG.
And the first-side sheet cannot be fed into a sheet-insertable space generated between the first-side sheet 50b and the second-side first sheet 50b. The reason for this is that the sheet on the first side is continuously fed, which deviates from the condition that the first and second sides are alternately fed.

Due to the above-mentioned space, it is necessary to leave an unnecessary sheet interval for one sheet in order to insert the next first sheet between the second sheets again on the transfer belt 5. This leads to a decrease in productivity.

On the other hand, L1 + L2 = N × Ls + Li
When N is an even number in (LetterY), FIG.
As shown in the case of N = 2 in (d), no useless space is generated between the last sheet 50a on the first side and the first sheet 50b on the second side. Therefore, the first side sheet and the second side sheet can be fed alternately and regularly, and the productivity is improved.

It is to be noted that a case where an odd number of sheets of other sizes are placed on the circumference of the transfer belt can be similarly considered.

[0089]

According to the present invention, a plurality of recording materials of different sizes can be grouped and controlled according to the number of sheets that can be arranged along the circumference of the recording material carrier. Feeding control for avoiding a seam of the circulating second-side recording material does not need to be performed for recording materials of different sizes, and the control can be simplified.

The relationship between the circumference of the recording material carrier and the length of the circulation path excluding the sheet reversing section is L1 + L2 = N × Ls + Li.
When the condition is satisfied, the recording material can be fed to the second side of the recording material that has been reversed and circulated without performing an unnecessary conveyance stop to avoid a seam. Performance can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming main part of a full-color image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a plan view showing a part of an operation panel.

FIG. 3 is a block diagram illustrating a control configuration of the entire apparatus.

FIG. 4 is a schematic configuration diagram of a portion near a timing roller and a transfer belt.

FIG. 5 is a diagram illustrating a positional relationship between the first and second sheets and the transfer belt when three sheets are arranged in the transfer belt circumferential length.

FIG. 6 is a diagram illustrating a positional relationship between a laterally passing letter size sheet and a laterally passing A4 size sheet with respect to a transfer belt.

FIG. 7 is a diagram illustrating a positional relationship between the first and second sheets and the transfer belt when two sheets are arranged in the transfer belt circumferential length.

FIG. 8 is a diagram illustrating a positional relationship between the first and second sheets and the transfer belt when one sheet is arranged in the transfer belt circumferential length.

FIG. 9 is a diagram illustrating the positional relationship between the first and second sheets and the transfer belt when the first and second sheets are alternately fed;

[Explanation of symbols]

 Pc, Pm, Py, Pk: Image forming unit 1: Feeding unit 2: Fixing unit 3: Sorter 5: Transfer belt (recording material holding unit) 5a: Joints 6c, 6m, 6y, 6k: Photoconductor drum (image holding) Body) 7c, 7m, 7y, 7k Image exposure device 8 Timing roller 9 Circulation path 9a Paper reversing section 10 Seam detection sensor 50 Paper (recording material) 200 Operation panel 301 System controller 302 ADF control Unit 303 IR control unit 304 image processing control unit 305 panel control unit 306 mechanical control unit 307 sorter control unit 310 image input unit 311 scanner image processing unit 312 multi-memory image processing unit 313 gradation processing unit 314: Frame memory 315: Registration correction unit

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hideki Hino 2-3-13 Azuchicho, Chuo-ku, Osaka-shi, Osaka Inside Osaka International Building Minolta Co., Ltd. (72) Inventor Kentaro Nagatani Azuchi-cho, Chuo-ku, Osaka-shi, Osaka 2-3-13 Osaka International Building Minolta Co., Ltd.

Claims (2)

[Claims] An image bearing member on which an image is formed, and a recording material formed in an endless shape having a seam and onto which the image formed on the image bearing member is transferred, are conveyed to a transfer position. A recording material carrying means; a circulation path for reversing and circulating the recording material to form an image on both sides of the recording material; and a transfer means for transferring an image on the image carrier to the recording material at a transfer position. An image forming apparatus capable of feeding a plurality of recording materials onto the recording material carrying means at intervals, wherein the peripheral length of the recording material carrying means varies depending on the length of the recording material in the transport direction. An image forming apparatus, wherein feeding control of a recording material to a seam of a recording material carrying unit is performed for each number of recording materials that can be arranged. 2. The length of the circulation path excluding the sheet reversing portion is L1 + L2, the peripheral length of the recording material supporting means is Ls, the interval between predetermined recording materials is Li, and the peripheral length of the recording material supporting means is Ls. N
2. The image forming apparatus according to claim 1, wherein when L is an integer, L1 + L2 = N.times.LS + Li.