JP2007034132A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of banding in an image forming apparatus having transfer and fixing processes. <P>SOLUTION: The distance between a transfer position and an intermediate conveyance means is made slightly smaller than the shortest image-receiving medium; the distance between the transfer position and a fixing part is made slightly smaller than the longest image-receiving medium; the image receiving medium is conveyed with the intermediate transport means in a holding state, when an image is formed on the shortest image-receiving medium; and the image-receiving medium is conveyed with the intermediate conveyance means in an open state, when an image is formed on the longest image-receiving medium, and the image-receiving medium is conveyed with the intermediate conveyance means in a holding state, after the end of transfer, when an image is formed on a middle-length image receiving medium. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus having a transfer process for transferring an image to an image receiving medium and a fixing process after transfer, and more specifically, image formation capable of preventing image unevenness in image transfer and miniaturizing the apparatus. Relates to the device.

As in electrophotographic image recording, after an image is formed on an image forming medium, or after an image is further transferred from the image forming medium to an intermediate transfer member, the image receiving medium (recording sheet) is transferred from the image forming medium or intermediate transfer member. An image forming method is known in which an image is transferred to the image and then the transferred image is fixed by pressurization or the like.
In image formation in which such transfer is performed, if load variation of the image receiving medium occurs during image transfer, image unevenness (so-called banding) occurs, and image quality deteriorates. Examples of load fluctuation factors that cause banding include an impact when the image receiving medium enters the downstream process during transfer (tip entry load), a speed difference between the downstream conveyance speed and the transfer speed, and the like.

Particularly in recent years, as disclosed in Patent Document 1 and the like, high-quality prints close to silver halide photographic prints can be created even in electrophotographic image formation by means such as giving gloss to the surface of an image receiving medium. Has been done.
In such a high-quality print, image unevenness becomes a big problem, and it is extremely important to eliminate the occurrence of banding. In addition, in such a high-quality print, a thick image receiving medium is preferred, so that the tip inrush load is large and banding is likely to occur.

In order to suppress such banding, various methods have been proposed for reducing or eliminating load fluctuations that occur during image transfer to an image receiving medium.
For example, in Patent Document 2, in an image forming apparatus that performs transfer and fixing by press contact such as electrophotography, the distance between the transfer position and the fixing position is made longer than the corresponding longest image receiving medium, thereby causing banding or the like. An image forming apparatus with reduced image quality degradation is disclosed.
Japanese Patent Application Laid-Open No. 2004-228561 discloses an apparatus in which an applied pressure is variable by using an electromagnetic force in addition to a spring in an image fixing apparatus using pressure. Using this, it is conceivable to reduce the banding by initially reducing the applied pressure and increasing the applied pressure after the image receiving medium has entered the fixing device.

JP 2004-109860 A JP-A-3-253882 JP 58-126561 A

  However, as disclosed in Patent Document 2, if the distance (conveyance length) between the transfer position and the fixing position is made longer than the longest image receiving medium, it is necessary to increase this distance, which increases the size and cost of the apparatus. It becomes a factor that causes

  In fixing an electrophotographic image formation, it is necessary to maintain a certain level of pressure. For this reason, when the method disclosed in Patent Document 3 in which the pressure is changed during fixing, the load relationship between the respective processes (units) fluctuates due to load fluctuations in the fixing unit that occur during fixing conveyance. The banding caused by will occur.

  An object of the present invention is to solve the above-described problems of the prior art, and an image for transferring an image to an image receiving medium and then fixing the image transferred to the image receiving medium as in electrophotographic image formation. In formation, image quality deterioration due to banding can be prevented, and it can be suitably applied to applications that require high quality images corresponding to photographic image quality, and also prevents the enlargement of the apparatus, An object of the present invention is to provide an image forming apparatus capable of configuring the apparatus compactly.

  In order to achieve the above object, an image forming apparatus of the present invention includes a transfer unit that transfers an image to an image receiving medium at a predetermined transfer position, and a transfer unit that is disposed downstream of the transfer unit and pressurizes the image receiving medium. A fixing unit that fixes the image formed thereon, and at least one intermediate conveyance unit that is disposed between the transfer unit and the fixing unit and can nipping and conveying the image receiving medium and can be in a nipping state and an open state. The conveyance length of the image receiving medium from the transfer position to the image fixing position in the fixing unit is shorter than the length in the conveyance direction of the longest image receiving medium in the conveyance direction, and the middle of the most upstream from the transfer position The conveyance length of the image receiving medium to the conveyance means, the conveyance length of the image reception medium between the intermediate conveyance means, and the conveyance length from the intermediate conveyance means at the most downstream to the fixing position in the fixing unit are in the conveyance direction. When forming an image on the longest image receiving medium, the intermediate conveying unit is opened, and the transfer unit receives the image on the fixing unit. When transferring the image to the position where the transfer is completed when the leading edge of the medium reaches, and when forming an image on the shortest image receiving medium, the intermediate conveying means is held in a sandwiched state, and The transfer unit provides an image forming apparatus that transfers an image to a position where the transfer has been completed when the leading edge of the image receiving medium reaches the upstream intermediate conveying unit.

  In such an image forming apparatus, it is preferable that the intermediate transporting units can be driven independently of each other, and the transfer unit is provided with a blank at an end in a direction orthogonal to the transporting direction. An image is transferred to a medium, and at least an image transfer surface side sandwiching unit of the intermediate transport unit is movable in a direction orthogonal to the transport direction, and sandwiches a blank portion at a side end of the image receiving medium. Is preferred.

  In the image forming apparatus of the present invention, when the image is formed on an image receiving medium whose length in the transport direction is shorter than the longest image receiving medium and longer than the shortest image receiving medium, It is preferable that a transfer is performed on the image receiving medium by providing a blank at the rear end in the transport direction, and the intermediate transport unit is initially in an open state and is in a sandwiched state after the transfer in the transfer unit is completed. .

  Alternatively, when forming an image on an image receiving medium whose length in the conveying direction is shorter than the longest image receiving medium and longer than the shortest image receiving medium, the intermediate conveying means is initially open. It is preferable that after the leading edge of the image receiving medium reaches the intermediate conveying means, the image receiving medium gradually enters a clamping state.

  Alternatively, when recording a plurality of images at intervals in the transport direction on an image receiving medium having a length in the transport direction shorter than the longest image receiving medium and longer than the shortest image receiving medium, It is preferable that the transport unit is initially in an open state, and is held when the image receiving medium reaches the intermediate transport unit and the transfer position is between images in the transport direction.

  Further, it is preferable that the intermediate transport unit is provided with a load reducing unit that makes a transport load on the image receiving medium smaller than a transport load on the image receiving medium in the transfer unit.

  According to the present invention having the above configuration, after an image is formed on an image forming medium or an intermediate transfer body, as in electrophotographic image formation, the image is transferred to an image receiving medium (recording sheet), and then transferred. In an image forming apparatus that fixes a printed image by pressurization (or further heating), banding (image unevenness) due to load fluctuation of the image receiving medium during transfer can be prevented, and the apparatus can be used in accordance with the corresponding image receiving medium. It can be made compact.

  Hereinafter, an image forming apparatus of the present invention will be described in detail based on a preferred embodiment shown in the accompanying drawings.

FIG. 1 is a conceptual diagram illustrating an example of a printer that uses the image forming apparatus of the present invention.
The printer 10 shown in FIG. 1 records an image on a recording sheet A (image receiving medium) by an electrophotographic method to create a print. Basically, the printer 10 includes a recording sheet supply unit 12 and an image forming unit 14. And a cutting / arranging portion 16. Further, even if there is no particular illustration or reference between these parts and each part, a conveying means for the recording sheet A such as a pair of conveying rollers and a guide member, or a recording sheet A can be provided as necessary. It has various members such as a sensor for detection that are arranged in a known printer. Furthermore, although not shown in the figure, it has control means for controlling the drive and operation of each part of the printer 10.

The printer 10 records an image corresponding to the print size on the recording sheet A, and then cuts the recording sheet A into a print size, thereby obtaining a (finished) print. In the illustrated example, as a preferable mode, as necessary, a plurality of images such as two images or four images are recorded on one recording sheet A, so-called multi-sided printing is performed, and a single recording sheet A is used. Create multiple prints.
Further, in the printer 10, in order to prevent the contamination of the apparatus due to unfixed toner and the adverse effect between the images when a plurality of images are recorded, the image is formed on the recording sheet A with a blank in the periphery. To do. Accordingly, the peripheral portion of the recording sheet A, that is, the leading and trailing ends in the transport direction, and both end portions in the direction orthogonal to the transport direction are blank.
In the following description, for the sake of convenience, the direction perpendicular to the transport direction is defined as the width direction, and the size of the recording sheet A in this direction is defined as the width. Further, the conveyance direction of the recording sheet A is defined as the conveyance direction, and the size of the recording sheet A in the conveyance direction is defined as the length. Furthermore, the front end and the rear end correspond to the transport direction.

The recording sheet supply unit 12 (hereinafter referred to as the supply unit 12) is a part that supplies the cut sheet-like recording sheet A to the image forming unit 14.
In the illustrated example, the supply unit 12 includes two loading portions of a magazine 20 that accommodates a recording sheet roll 20 a formed by winding a long recording sheet A, and a cassette 24 that accommodates a cut sheet-like recording sheet A. And a loading unit.
In the loading section of each magazine 20, recording sheet rolls 20a having different widths (different sizes) are usually accommodated. On the other hand, the cassette 52 is a case for storing the recording sheet A and loading it into the printer, similar to those used in various printers.

  In the printer 10, the recording sheet A is not particularly limited, but basically, like a recording sheet in which a transparent resin layer made of a thermoplastic resin is formed on at least one surface of a substrate made of paper or the like, It is suitable for recording sheets (sheets for photographic image quality printing) that can produce photographic quality prints with excellent gloss. As an example, this recording sheet is formed by forming a toner image on a transparent resin layer, and then subjecting the toner to a transparent resin by heating and pressing with a belt having excellent surface smoothness (which may also be used for fixing a toner image). By being melted in the layer and then cooled and fixed, a print having excellent gloss like a silver salt photographic print can be produced (see JP-A-5-216322, etc.).

  Although not shown in the drawings, the size of the recording sheet roll 20a (that is, the width (width dimension)) accommodated in the magazine 20 and the cassette 24 are accommodated in each loading unit by a dip switch, a barcode, or the like. Detection means for detecting the size of the recording sheet A and the type of the recording sheet A is arranged.

A drawer roller pair 22 and a cutter 28 are arranged downstream of each magazine 20 loaded in the loading unit (downstream in the conveyance direction of the recording sheet A).
The drawing roller pair 22 is a roller pair that pulls out a recording sheet from the recording sheet roll 20 a accommodated in the magazine 20. The cutter 28 is a known sheet-like material cutting means such as a guillotine cutter.

The drawing of the recording sheet from the recording sheet roll 20a by the drawing roller pair 22 is stopped when the length of the recording sheet downstream from the cutter 28 reaches a predetermined length. Next, the cutter 28 cuts the recording sheet into a recording sheet A having a predetermined size cut sheet, and supplies the recording sheet A to a predetermined conveying means.
Here, as described above, in the printer 10, an image is formed on the recording sheet A so that the periphery is blank. In the present invention, the image is formed according to the print size (image size) or the like. By adjusting the cut-out length of the recording sheet A, blanks at the leading end and the trailing end (particularly the trailing end) of the recording sheet A may be formed and / or the length of the blank may be adjusted.

  Further, the recording sheet A accommodated in the cassette 24 is pulled out by a known means used in various printers and supplied to a predetermined conveying means.

Both the recording sheet A cut to a predetermined size by the cutter 28 and the recording sheet A drawn from the cassette 24 are conveyed to the image forming unit 14 by a pair of conveying rollers.
A print head 26 that records a back print on the back surface (non-image recording surface) of the print is disposed between the two transport roller pairs immediately upstream of the image forming unit 14.
The print head 26 is not particularly limited, and various known printing means such as an impact printer using an ink ribbon and an ink jet printer can be used.

The image forming unit 14 forms an image on the recording sheet A by electrophotography, and includes an exposure unit 30, a toner image forming unit 32, a transfer unit 34, and a first intermediate conveyance roller pair 36 (hereinafter referred to as a first pair). A first conveying roller pair 36), a second intermediate conveying roller pair 37 (hereinafter referred to as a second conveying roller pair 37), a fixing unit 38, and a reversing unit 40.
The image forming unit 14 is related to the image forming apparatus of the present invention, and the transfer position of the image onto the recording sheet A in the transfer unit 34 and the distance (transport distance) between the first transport roller pair 36 correspond to each other. The interval between the transfer position and the fixing portion 38 is slightly shorter than the corresponding recording sheet A having the longest length. This will be described in detail later.

The exposure unit 30 includes an exposure control unit 42 and an exposure unit 44.
The exposure control unit 42 obtains an image (image data) to be reproduced from an image supply source and performs predetermined image processing, and then the number of images to be recorded on one recording sheet A (number of recording surfaces). Accordingly, an image is assigned to be recorded on one recording sheet A. As described above, in the printer 10, one or more images are formed on the recording sheet A so that the periphery of each image is blank. Therefore, the exposure control unit 42 satisfies a predetermined interval between the images so as to satisfy this. The image is assigned so that there is a blank space at the leading edge and the trailing edge of the recording sheet A, and both ends in the width direction (hereinafter referred to as side edges).

On the other hand, the exposure unit 44 is a light beam (recording light) light source, an optical deflector, an fθ lens, an optical path changing mirror, and a light beam adjusting light for exposing an electrophotographic photosensitive drum 46 of the toner image forming unit 32 described later. This is a known light beam scanning optical system having the above-described lens.
That is, the exposure unit 44 applies the light beam E modulated according to the image data (that is, the image to be recorded) supplied from the exposure control unit 42 in the width direction (the conveyance direction of the recording sheet A (= electrophotographic photosensitive drum). The light is deflected and emitted in the main scanning direction that coincides with the direction orthogonal to the rotation direction of 46), is reflected by the mirror 44a, enters the predetermined exposure position, and records a latent image on the electrophotographic photosensitive drum 46. .

The toner image forming unit 32 is a known toner image forming unit by electrophotography, and is an electrophotographic photosensitive drum 46 (hereinafter referred to as a photosensitive drum 46), a charging unit 48, a cleaning unit 50, and a toner supply unit 52. Have
The photosensitive drum 46 is a known electrophotographic photosensitive drum, and rotates in the direction of arrow a (the direction opposite to the conveyance direction of the recording sheet A) with the central axis coinciding with the width direction. As described above, since the light beam E from the exposure unit 44 is deflected in the width direction, the photosensitive drum 46 is two-dimensionally scanned and exposed by the light beam E modulated according to the recorded image.
The toner supply unit 52 supplies a C (cyan) toner supply unit 54C, an M (magenta) toner supply unit 54M, a Y (yellow) toner supply unit 54Y, and a K (black) toner supply to a rotatable drum-shaped main body 52a. The four toner supply portions of the portion 54K are provided at intervals of a rotation angle of 90 °.

  The transfer unit 34 presses the transfer belt 60 against the photosensitive drum 46 from the inside, a transfer belt 60 that is an endless belt partly contacting the photosensitive drum 46, three rollers 62 that stretch the transfer belt 60, and the inside. A pressing roller 64, a transfer roller 66, and a conveyance guide 68 are included. The transfer belt 60 is an intermediate transfer member for a toner image, and rotates in the direction of arrow b (the same direction as the conveyance direction of the recording sheet A). Further, the transfer roller 66 is movable together with one of the rollers 62 to a position where the transfer belt 60 (recording sheet A) is sandwiched and a position where the transfer roller 60 is separated from the transfer belt 60.

The photosensitive drum 46 is uniformly charged in the width direction by the charging means 48 while rotating in the direction of arrow a in the figure, and is scanned two-dimensionally by the light beam E modulated according to the image data as described above. Exposure is performed to form an electrostatic latent image. Next, the electrostatic latent image is developed by a toner supply unit, for example, a Y toner supply unit 54Y, located at the development position of the toner supply unit 52 (a position facing the photoconductive drum 46), and the surface of the photoconductive drum 46 is developed. A Y toner image is formed.
Further, the transfer belt 60 that is partly in contact with the photosensitive drum 46 and pressed by the pressing roller 64 rotates in the direction of arrow b in synchronization with the rotation of the photosensitive drum 46. Accordingly, the toner image of the photosensitive drum 46 developed by the toner supply means 52 is transferred to the transfer belt 60 at this contact portion (pressing portion by the pressing roller 64). In the region where the transfer of the toner image onto the transfer belt 60 of the photoconductive drum 46 is completed, the remaining toner is removed by the cleaning unit 50.

In the illustrated example, such toner image formation and transfer to the transfer belt 60 are performed by supplying four toners including a Y toner supply unit 54Y, an M toner supply unit 54M, a C toner supply unit 54C, and a K toner supply unit 54K. The parts are operated sequentially.
For example, after the Y toner image is transferred to the transfer belt 60 as described above, the toner supply means 52 (main body 56a) is then rotated by 90 ° in the direction of the arrow c, so that the M toner supply unit 54M is positioned at the development position. Then, the toner image is aligned with the Y toner image on the transfer belt 60, and similarly, a latent image is formed on the photosensitive drum 46 to form an M toner image and transferred to the transfer belt 60. Thereafter, similarly, the C toner image is transferred to the transfer belt, and the K toner image is transferred to the transfer belt. During this time, the transfer roller 66 is separated from the transfer belt 60.
Therefore, in the illustrated example, toner images of Y, M, C, and K are formed in alignment on the surface of the transfer belt 60, that is, four (full) color images are formed.

On the other hand, a cut sheet-like recording sheet A having a predetermined size is supplied from the supply unit 12 and waits at a registration roller pair 70 immediately upstream of the transfer roller 66, for example.
When a color image is formed on the transfer belt 60, the recording sheet by the registration roller pair 70 is synchronized with the rotation of the transfer belt 60 so that the recording sheet A and the color image formed on the transfer belt 60 are aligned. The conveyance of A is started, the transfer roller 66 is pressed against the transfer belt 60 (roller 62), and the recording sheet A is nipped and conveyed between the transfer belt 60 and the transfer roller 66. By this nipping and conveying, the four color toner images formed on the surface of the transfer belt 60 are transferred to the recording sheet A, and an image is formed on the surface of the recording sheet A.

  As described above, this image is impositioned according to the number of images to be recorded, and since the periphery of each image is imprinted so that no image is recorded, the recording sheet A A predetermined blank is formed around each image formed (transferred), and the front and rear ends and both side ends of the recording sheet A are blank.

The recording sheet A on which the image has been formed is guided by the conveyance guide 68 and conveyed to the first conveyance roller pair 36 and the second conveyance roller pair 37.
The first conveyance roller pair 36 and the second conveyance roller pair 37 convey the recording sheet A on which the toner image is formed by the transfer unit 34 to the fixing unit 38.

As shown in FIG. 2, in the printer 10, the first conveying roller pair 36 includes a long roller 81 having an axial length larger than the maximum width recording sheet A, and the recording sheet A together with the long roller 81. Are provided with two short rollers 83.
In the first conveying roller pair 36, the long roller 81 is a driving roller, and the short roller 83 is a driven roller. Further, the long roller 81 is disposed on the lower side (non-image forming surface side), and the short roller 83 is disposed on the upper side.

In the illustrated example, the recording sheet A is positioned in the width direction of the recording sheet A by a so-called center resist that matches the center in the width direction with the center in the width direction of the conveyance path.
The two short rollers 83 of the first conveying roller pair 36 are spaced apart from each other in the width direction by the same distance from the center in the width direction indicated by the alternate long and short dash line in FIG. Thus, the interval can be changed. In the illustrated example, the first conveying roller pair 36 thereby corresponds to the recording sheets A having various widths.
Here, as described above, in the printer 10, the recording sheet A before being cut (transferred) on which the image is recorded is blank on both side edges. The first conveying roller pair 36 adjusts the interval of the short rollers 83 according to the position information of the image on the recording sheet A (image recording position information by the exposure unit 44) in addition to the width information of the recording sheet A, As shown in FIG. 3 to be described later, a short roller 83 holds the blank portion at the side end of the recording sheet A. This prevents adverse effects on the image transferred to the recording sheet A and contamination with unfixed toner.

Further, the short roller 83 moves up and down as indicated by an arrow z in FIG. 2 so as to be able to contact / separate from the long roller 81, that is, it can be held and released.
Here, in the printer 10 of the illustrated example, as a preferable aspect, the first transport roller pair 36 moves the short roller 83 downward from the open state at a stretch and enters the sandwiched state, and the short roller 83 from the open state. Both operations, that is, gradually moving downward and moving from the open state to the clamping state, are possible. This will be described in detail later.

There is no particular limitation on the method of bringing the two short rollers 83 into and away from each other with respect to the center in the width direction, and various known methods can be used. For example, a method of screwing a frame that supports the short roller 83 to a shaft forming a reverse screw, and a shaft of the short roller 83 at a portion where the moving directions of the timing belt stretched around the two pulleys are opposite to each other. A method of fixing the supporting frame can be used.
Further, the method for bringing the short roller 83 into the open state and the clamping state is not particularly limited. For example, the two short rollers 83 (frames that pivotally support the short roller 83) that can be brought into contact with and separated from each other as described above are used. Various known methods such as a method of holding the unit and biasing the unit toward the long roller 81 with a spring or the like and swinging the unit up and down using a cam or the like can be used. is there.

A second transport roller pair 37 is disposed downstream of the first transport roller pair 36. The second transport roller pair 37 transports the recording sheet A transported by the first transport roller pair 36 to the downstream fixing unit 38.
As shown in FIG. 2, the second transport roller pair 37 has the same configuration as the first transport roller pair 36 described above, which includes a long roller 82 and two short rollers 84.

  In the illustrated example, there are two intermediate conveyance roller pairs (intermediate conveyance means), a first conveyance roller pair 36 and a second conveyance roller pair 37. However, the intermediate conveyance roller pair is suitable for conveyance described later for all corresponding lengths of the recording sheet A according to the distance between the transfer unit 34 and the fixing unit 38 and the length of the corresponding recording sheet A. It is possible to have three or more, or only one, between the transfer unit 34 and the fixing unit 38 so that it can be performed.

  In the present invention, the intermediate conveying means may use a belt conveyor instead of the long rollers 81 and 82, and the recording medium A may be nipped and conveyed by the belt conveyor and the short rollers 83 and 84.

A fixing unit 38 is disposed downstream of the second conveyance roller pair 37.
The fixing unit 38 includes a heating roller 85, a roller 86, a fixing belt 88 that is an endless belt stretched between the heating roller 85 and the roller 86, a cooling unit 90 that is included in and in contact with the fixing belt 88, and the heating roller 85. A nip roller 92 that sandwiches the fixing belt 88 is provided.
The heating roller 85 is a known heating roller that includes a heat source having a calorific value corresponding to a recording sheet heating process described later. The fixing belt 88 is a belt having a very high surface (outer surface) smoothness.

  The fixing unit 38 heats / heats the recording sheet A when creating a high-quality print having glossiness corresponding to a silver salt photograph using the above-described photographic quality printing sheet as the recording sheet A. A surface treatment by pressure and an image fixing treatment are performed.

Specifically, the recording sheet A (the photographic quality print recording sheet) onto which the image (toner image) has been transferred in the transfer unit 34 is nipped and conveyed by the fixing belt 88 (heating roller 85) and the nip roller 92. The recording sheet A is heated / pressurized, and then cooled by the cooling unit 90. Thereby, the thermoplastic resin or further toner on the surface of the recording sheet A is first melted, and then the melted thermoplastic resin or further toner is cooled / solidified to be fixed.
At this time, the thermoplastic resin on the surface of the recording sheet A is melted / cooled / solidified while being conveyed under pressure, whereby the surface properties of the fixing belt 88 are transferred. Here, as described above, the fixing belt 88 has very high surface smoothness. Therefore, the recording sheet A has a high surface smoothness and good glossiness, and from this recording sheet A, a print having the same quality as a silver salt photographic print can be obtained.

In the illustrated printer 10, the heating condition and / or the cooling condition in the fixing unit 38 can be adjusted, thereby making it possible to adjust the glossiness applied to the surface of the recording sheet A (print). Good.
Further, by selecting the surface property of the fixing belt 88, mat processing or the like may be performed instead of gloss processing.

  As described above, in the printer 10, the first transport roller pair 36 is disposed downstream of the transfer unit 34 that transfers the image to the recording sheet A, and the second transport roller pair 37 is downstream of the first transport roller pair 36. Further, a fixing unit 38 is disposed downstream of the second conveying roller pair 37.

Here, the image transfer position to the recording sheet A in the transfer section 34 (that is, the contact position (end position of the recording sheet A) between the endless belt 60 (roller 62) and the transfer roller 66) and the first conveying roller pair. The distance between the recording sheet A and the recording sheet A is slightly shorter than the corresponding shortest recording sheet A. That is, the conveyance distance of the recording sheet A from the image transfer position to the recording sheet A to the first conveyance roller pair 36 is slightly shorter than the length of the shortest recording sheet A.
The interval between the image transfer position and the fixing unit 38 (the contact position between the nip roller 92 and the fixing belt 88 (the heating roller 85) (the position where the recording sheet A is sandwiched)) is a record corresponding to the maximum length. It is slightly shorter than the length of the sheet A. That is, the conveyance distance of the recording sheet A from the image transfer position to the recording sheet A to the fixing unit 38 is slightly shorter than the length of the longest recording sheet A.
Further, the distance between the first conveying roller pair 36 and the second conveying roller pair 37 and the contact position (recording) between the second conveying roller pair 37 and the fixing unit 38 (nip roller 92 and fixing belt 88 (heating roller 85)). The distance between the sheet A and the nipping position)) is shorter than the length of the shortest recording sheet A.
Further, as described above, the recording sheet A to which the image has been transferred in the transfer unit 34 has blanks at the front end and the rear end, and further at both side ends.

  The image forming apparatus according to the present invention has such a configuration in image formation including an image transfer process and a fixing process, so that a photographic quality print using the above-described recording sheet for photographic quality prints can be obtained. Corresponding to applications that require creation of high-quality prints, image quality deterioration due to banding can be prevented, and high-quality prints can be stably produced. Further, since the conveyance distance between the image transfer position and the fixing unit is set according to the recording sheet A having the longest length, the size of the apparatus is not increased.

  The operation of fixing the image transferred to the recording sheet A in the printer 10 will be described below with reference to the conceptual diagrams shown in FIGS. Explained.

First, when an image is recorded on the recording sheet A _min having the shortest length, the first conveying roller pair 36 and the second conveying roller pair 37 are both sandwiched, and image fixing and conveyance of the recording sheet A _min are performed. Do. Further, the positions in the width direction of the short rollers 83 and 84 are positions that sandwich the blank portion at the side edge according to the width information of the recording sheet A and the position information of the image.
The recording sheet A _min is transferred with an image by the transfer unit 34, and then the leading end reaches the first conveying roller pair 36.

Here, as described above, the conveyance distance L1 of the recording sheet A from the image transfer position to the recording sheet A to the first conveyance roller pair 36 is slightly shorter than the length of the shortest recording sheet _Amin . Further, the trailing edge (also the leading edge in the illustrated example) of the recording sheet A to which the image has been transferred is blank. Therefore, as schematically shown in FIG. 3, when the leading end of the recording sheet A _min having the shortest length is sandwiched between the first conveying roller pair 36, the transfer unit 34 displays an image (hatched area) on the recording sheet A _min . ) Has been completed, and the transfer roller 66 and the transfer belt 60 (roller 62) sandwich the blank portion at the rear end of the recording sheet _Amin (in other words, this is realized). Transfer the image to the position).
Accordingly, the recording sheet A _min can be properly conveyed to the first conveying roller pair 36, and even if the leading edge of the recording sheet A _min is plunged / clamped by the first conveying roller pair 36 and a load fluctuation occurs, at this time, Since the transfer is completed, image unevenness due to banding does not occur. Also, the short roller 83, so that clamping a blank portion of the side edge of the recording sheet A _min, without adversely affecting the unfixed toner image, and further, nor short rollers 83 itself is contaminated.

The recording sheet A _min on which the image is fixed by the first conveying roller pair 36 is then nipped and conveyed by the second conveying roller pair 37 and conveyed to the fixing unit 38. At this time, since the short roller 84 sandwiches the blank portion at the side end, the unfixed toner image is not adversely affected, and the short roller 84 itself is not contaminated.
The second transport roller pair 37 can be driven independently of the first transport roller pair 36. Therefore, the second conveying roller pair 37 is initially set to a separated (clamping open) state, and after the leading edge of the recording sheet _Amin is nipped by the first conveying roller pair 36, the second conveying roller pair 37 is nipped at an arbitrary timing. Also good.

The recording sheet A _min conveyed to the fixing unit 38 is nipped and conveyed between the fixing belt 88 (heating roller 85) and the nip roller 92 as described above, so that the recording sheet A _min is heated / pressurized and cooled to be subjected to surface treatment and fixing. Is carried downstream.

On the other hand, when an image is recorded on the longest length recording sheet _Amax , as shown by a dotted line in FIG. 3, the first transport roller pair 36 and the second transport roller pair 37 are both separated (clamping and releasing). As a state, image transfer is performed.
Accordingly, the recording sheet A _max on which the image is transferred by the transfer unit 34 passes through the first conveyance roller pair 36 and the second conveyance roller pair 37, and the leading end reaches the fixing unit 38.

Here, as described above, the conveyance distance L2 of the recording sheet A from the image transfer position to the recording sheet A to the fixing unit 38 is slightly shorter than the length of the longest recording sheet _Amax . Further, the trailing edge (also the leading edge in the illustrated example) of the recording sheet A to which the image has been transferred is blank. Therefore, as schematically shown in FIG. 3, at the time when the leading end of the longest recording sheet _Amax is sandwiched between the nip roller 92 and the fixing belt 88 (heating roller 85) of the fixing unit 38, as in the previous example. In the transfer section 34, the transfer of the image to the recording sheet _Amax is completed, and the blank portion at the rear end of the recording sheet _Amax is sandwiched between the transfer roller 66 and the transfer belt 60 (roller 62). (In other words, the image is transferred to a position where this is realized).
Therefore, the recording sheet _Amax can be properly conveyed to the fixing unit 38, and even if the leading end of the recording sheet _Amax enters / fixes into the fixing unit 38 and a load fluctuation occurs, the transfer is completed at this point. Therefore, image unevenness due to banding does not occur.

That is, in the present invention, the conveyance distance from the image transfer position to the first conveyance roller pair 36 is slightly shorter than the length of the shortest recording sheet A _min , and the conveyance distance from the image transfer position to the fixing unit 38 is “Slightly shorter than the length of the longest recording sheet A _max ” means that the conveying distance is shorter than the length of the blank portion at the rear end of the recording sheet A (to realize this, the recording sheet A Control the transfer position of the image.

The recording sheet A _max conveyed to the fixing unit 38 is heated / pressurized and cooled by being nipped and conveyed between the fixing belt 88 (heating roller 85) and the nip roller 92 in the fixing unit 38 as described above. Surface treatment and fixing are performed and conveyed downstream.
When an image is recorded on the longest recording sheet _Amax , the position of the first conveying roller pair 36 in the width direction of the short roller 83 according to the width information of the recording sheet A and the position information of the image, And, the position of the second conveying roller pair 37 in the width direction of the short roller 84 is positioned in the blank portion at the side edge of the recording sheet _Amax , and when the transfer in the transfer unit 34 is completed, the short roller 83 and The recording sheet A _max may be nipped and conveyed by the first conveying roller pair 36 and the second conveying roller pair 37 by descending 84.

Further, when an image is recorded on a recording sheet A _mid longer than the shortest recording sheet A _min and shorter than the longest recording sheet A _max (hereinafter referred to as an intermediate length). 4 and 5, both the first conveyance roller pair 36 and the second conveyance roller pair 37 are set in a separated (clamping open) state. Further, the position in the width direction of the short roller 83 of the first conveying roller pair 36 and the position in the width direction of the short roller 84 of the second conveying roller pair 37 according to the width information of the recording sheet A and the position information of the image. _Is positioned in the blank portion at the side edge of the recording sheet A _mid .

In this state, the leading edge of the recording sheet A _mid on which the image is transferred by the transfer unit 34 reaches the first conveyance roller pair 36, and then reaches the second conveyance roller pair 37.
Here, when an image is recorded on the intermediate-length recording sheet A _mid , three types of operations (modes) are exemplified as the operations of the first conveyance roller pair 36 and the second conveyance roller pair 37.

First, in the first mode, _{even if} the leading edge of the intermediate length recording sheet A _mid1 shown in FIG. 4 reaches the first conveying roller pair 36, the first conveying roller pair 36 is not sandwiched, and the previous recording sheet A _{As in the case of min} and recording sheet A _max , the transfer of the image in the transfer section 34 is completed, and the blank portion at the rear end of the recording sheet A _mid1 is sandwiched between the transfer roller 66 and the transfer belt 60 (roller 62). At this point, the short rollers 83 and 84 are _moved down to place the first conveyance roller pair 36 and the second conveyance roller pair 37 between them, and the recording sheet A _mid1 is conveyed.
At this time, the second conveyance roller pair 37 may be in a sandwiched state at a timing different from that of the first conveyance roller pair 36. For example, when the leading edge of the recording sheet does not reach the second conveying roller pair 37 as in the intermediate length recording sheet A _mid2 shown in FIG. 4, the second conveying roller pair 37 is changed to the first conveying roller pair 36. The leading edge of the recording sheet A _mid2 may pass through the second conveying roller pair 37 at a timing different from that at the time when the recording sheet A _{mid2 reaches} a predetermined position.
Also in this method, since the nipping by the first conveying roller pair 36 and the second conveying roller pair 37 is after the image transfer is completed, the occurrence of image unevenness due to banding can be prevented. Further, since the short rollers 83 and 84 sandwich the blank portion at the side end, the unfixed toner image is not adversely affected, and further, the short rollers 83 and 84 themselves are not contaminated.

In the second mode, as shown in FIG. 5, a predetermined timing is reached after the leading edge of the intermediate-length recording sheet _Amid3 passes the first conveying roller pair 36 regardless of the end of the transfer in the transfer section 34. Then, the short roller 83 of the first conveying roller pair 36 is gradually lowered to the _nipping state, and the recording sheet A _mid3 is conveyed by the first conveying roller pair 36. Further, after the leading edge of the recording sheet A _mid3 has passed the second transport roller pair 37, the short roller 84 of the second transport roller pair 37 is gradually lowered at the predetermined timing in the same manner as the first transport roller pair 36. Thus, the recording sheet A _mid3 is conveyed.
Even in this method, the recording sheet A _mid3 is clamped after the leading edge has passed, and the short rollers 83 and 84 are gradually lowered and clamped, so that occurrence of image unevenness due to banding can be prevented. Further, since the short rollers 83 and 84 sandwich the blank portion at the side end, the unfixed toner image is not adversely affected, and further, the short rollers 83 and 84 themselves are not contaminated.
In addition, when the transfer in the transfer unit 34 is already finished before the leading edge of the recording sheet A _mid3 reaches the second conveying roller pair 37, the short roller 84 of the second conveying roller pair 37 is held in any state. Also good.

As shown in FIG. 6, the third mode corresponds to a case where a plurality of images are allocated and recorded in the transport direction (length direction).
In this mode, _after the leading edge of the intermediate-length recording sheet A _mid4 reaches the first conveying roller pair 36, when the interval between the images in the conveying direction reaches the image transfer position as indicated by a dotted line in FIG. Then, the short roller 83 is lowered, the first conveying roller pair 36 is held, and the recording sheet A _mid4 is conveyed by the first conveying roller pair 36. Further, for the second conveyance roller pair 37, as in the case of the first conveyance roller pair 36, _after the leading edge of the recording sheet A _mid4 reaches the second conveyance roller pair 37, an image transfer position is _defined between the images in the conveyance direction. At the point of time, the short roller 84 is lowered to place the second conveying roller pair 37 between them, and the recording sheet A _mid4 is conveyed by the second conveying roller pair 37.

Similarly to the second mode, when the transfer at the transfer section 34 has already been completed before the leading edge of the recording sheet A _mid4 reaches the second conveyance roller pair 37, the second conveyance roller pair 37 is used. The short roller 84 may be clamped at any timing.
Also in this method, since the nipping by the first conveying roller pair 36 and the second conveying roller pair 37 is performed other than during transfer, the occurrence of image unevenness due to banding can be prevented. In addition, since these images are finally cut and removed by the cutting / arranging unit 16, even if there is any inconvenience between these images, there is no influence on the product quality of the print. . Further, since the short rollers 83 and 84 sandwich the blank portion at the side end, the unfixed toner image is not adversely affected, and the short rollers 83 and 84 themselves are not contaminated.

In the present invention, when an image is recorded on the recording sheet A _mid having an intermediate length, only one of the first mode and the second mode may be performed. Any of the second modes may be selectable.
Further, the third mode may not be set, and the third mode may be set and selectable when it can be implemented.

When recording an image on the recording sheet A _mid having an intermediate length, in the second mode and the third mode, the recording sheet A _mid is sandwiched by the second conveyance roller pair 37 during image transfer in the transfer unit 34. As a result, the conveyance is performed. Therefore, the nipping and conveying by each pair of conveying rollers (the first conveying roller pair 36 and the second conveying roller pair 37) gives a load fluctuation to the nipping and conveying by the transfer belt 60 and the transfer roller 66 in the transfer unit 34, and banding occurs. There is also a possibility to do.

  In order to prevent such an inconvenience, as a means for reducing the load on each conveyance roller pair, a method of making the clamping force of each conveyance roller pair sufficiently weaker than the clamping force in the transfer unit 34 (each conveyance roller pair is simply a recording medium). (Since it only conveys sheet A, a strong clamping force is not required), and by a method of providing one-way clutch capable of idling only in the conveying direction on long rollers 82 and 83 that are driving rollers of each conveying roller pair In addition, it is preferable to prevent each pair of conveying rollers from giving a load fluctuation to the transfer unit 34 during transfer, and to more reliably prevent the occurrence of banding. Further, by adopting such a configuration, the burden on the fixing unit 38 that performs the surface treatment of the recording sheet A is reduced, and the surface of the recording sheet A caused by slippage between the recording sheet A and the fixing belt 88 or the like. Can prevent quality degradation.

When an image is recorded on the recording sheet A _mid having the intermediate length as described above, the transfer unit 34 performs recording when the leading edge of the recording sheet A reaches the first conveying roller pair 36 as necessary. The cutting length of the recording sheet A in the supply unit 12 may be adjusted so that the sheet A is sandwiched, or the image forming position on the recording sheet A may be adjusted.

In the illustrated example, for the purpose of preventing contamination with toner and the like, as a preferred mode, there are blank portions at all of the four periphery of the front end, rear end, and both side ends of the recording sheet A.
However, the present invention is not limited to this, and when an image is recorded on the recording sheet A having the longest length, blanks at the leading edge and both side edges may be eliminated (that is, the blank may be only at the trailing edge). ). Further, when an image is recorded on the recording sheet A having the intermediate length and the shortest length, the blank at the front end may be eliminated (same as the rear end and the side end).
Depending on the sandwiching method and timing by each pair of transport rollers, the space between the images when performing multiple imposition is not necessarily required.

  Further, in the image forming apparatus of the present invention, the image recording method is not limited to the electrophotography as shown in the example, and a latent image is recorded on a transfer sheet having a color material layer by means of heating or exposure, and this latent image is recorded. Various image recording methods are available that have an image transfer process to a recording sheet (image receiving medium) and a fixing process after the transfer, such as image recording by peeling transfer that performs fixing after transferring the image to the recording sheet. is there.

A reversing unit 40 is provided to branch from the downstream of the fixing unit 38.
The reversing unit 40 is a part for reversing the recording sheet A on which an image is recorded on one side in order to create a so-called double-sided print, and includes a first switching unit 72 disposed downstream of the fixing unit 38 and a fixing unit 38. A branch path 74 that is branched from the conveyance path, a kickback section 76 that is provided downstream of the branch path 74, and a pair of registration rollers that are branched from the branch path 74 and the kickback section 76 and upstream of the transfer section 34. 70, and a second switching means 80 provided at a branch point between the kickback portion 76 and the return conveyance path 78.
Both the first switching means 72 and the second switching means 80 act on (insert into) the conveyance path, and transport a known sheet-like material such as a flapper that guides the recording sheet A to the predetermined conveyance path. Switching means.

In the printer 10, when creating double-sided printing, the first switching unit 72 acts on the conveyance path from the fixing unit 38 to send the recording sheet A to the branch path 74, and conveys the recording sheet A from the branch path 74 to the kickback unit 76. Then, when the upstream end of the recording sheet A reaches the downstream side of the second switching means 80, the conveyance is stopped.
Next, the second switching unit 80 is applied to the kickback unit 76, and the recording sheet A is conveyed in the reverse direction in the kickback unit 76, and is guided by the second switching unit 80 to return and convey the recording sheet A. The recording sheet is turned upside down by being sent to the path 78 and conveyed from the return conveying path 78 to the registration roller pair 70.

A cutting / arranging unit 16 is provided downstream of the reversing unit 40.
The cutting / arranging unit 16 includes a position adjusting unit 100, a cutting unit 102, an arranging unit 104, and a discharge unit 106.

The recording sheet A conveyed to the cutting / arranging unit 16 is first set to a predetermined position in the width direction in the position adjusting unit 100.
As described above, in the printer 10, one or more images are impositioned on the recording sheet A in a state having a blank around the recording sheet A. In response to this, the printer 10 cuts the recording sheet A in the width direction and the conveyance direction according to the print size of the print to be created in the cutting unit 102 described later, and forms individual prints. The position adjusting unit 100 is a part that adjusts the position in the width direction of the recording sheet A on which an image is formed to a predetermined position in order to perform this cutting appropriately.

There are no particular limitations on the position adjustment means in the width direction of the recording sheet A in the position adjustment unit 100, and various known position adjustment means for sheet-like materials can be used.
As an example, there is a method of using a guide plate that abuts the side edge of the recording sheet A and regulates the position in the width direction, and has an axial position adjustment function that moves in the width direction with the recording sheet A being sandwiched. Examples include a method using a pair of transport rollers.

The recording sheet A whose position in the width direction has been adjusted by the position adjusting unit 100 is then cut by the cutting unit 102 in accordance with the print size, and is set as a print P (hard copy) output as a product.
The cutting unit 102 includes a first slitter 110 and a second slitter 112, a guillotine cutter 114, and a registration roller pair 116.

Each of the first slitter 110 and the second slitter 112 cuts the recording sheet A in the transport direction, and is a known slitter using, for example, a rotary cutter or a circular cutter.
Both the first slitter 100 and the second slitter 112 are composed of two cutters arranged in the width direction at the same position in the transport direction and capable of adjusting the position in the width direction. Further, the second slitter 112 is disposed downstream of the first slitter 100.
Both the first slitter 100 and the second slitter 102 are transported by moving each cutter in the width direction according to the width information of the recording sheet A and the position information of the image (position information in the width direction). The recording sheet A is cut in the conveyance direction, and is cut out to the size in the width direction of the print for creating the recording sheet A.

In the illustrated example, the printer 10 records a maximum of two images in the width direction (performs a maximum of two faces).
As shown in FIG. 7A, when two images are recorded in the width direction (arrow y direction), each cutter of the first slitter 110 is converted into one image in the width direction, for example, the conveyance direction (arrow x direction). the corresponding place on the left side of the image, and taken along line Cx ₁ while conveying the recording sheet a, is cut corresponding to the size of the corresponding image printed in the width direction. The second slitter 112 of the downstream, the other images of the respective cutter width direction, that is, arranged corresponding to the right side of the image in the conveying direction, along line Cx ₂ while conveying the recording sheet A Then, the corresponding image is cut corresponding to the size in the width direction of the print.
That is, first, the first slitter 110 cuts out an image on the left side in the conveyance direction, and then the second slitter 112 cuts out the image on the right side.

On the other hand, as shown in FIG. 7B, when one image is recorded in the width direction, the second slitter 112 is retracted from the conveyance path of the recording sheet A, and each cutter of the first slitter 110 is moved to the recording sheet A. and arranged corresponding to the image recorded in the recording sheet while conveying the a, and taken along line Cx _1, to cut in response to the size of the corresponding image printed in the width direction.

The guillotine cutter 114 is a known guillotine cutter that cuts the recording sheet A in the width direction.
The registration roller pair 116 stops the conveyance of the recording sheet A at the cutting position by the guillotine cutter 114 according to the position information (position information in the conveyance direction) of the image of the recording sheet A. It is a pair of transport rollers that perform cutting positioning.

For example, as shown in FIG. 7A, when two images are recorded in the conveyance direction, the registration roller pair 116 _first uses the guillotine cutter 114 so that the cutting line Cy ₁ on the leading end side of the leading end image is When the cutting position is reached, the conveyance of the recording sheet A is stopped. Next, the guillotine cutter 114 is operated to cut the recording sheet A at the cutting line Cy ₁ .
After cutting, the registration roller pair 116 resumes the conveyance of the recording sheet A, at the time when the cutting line Cy ₂ on the rear end side of the image becomes cutting position by the guillotine cutter 114, to stop the conveyance of the recording sheet A . Next, similarly, the guillotine cutter 114 is operated to cut the recording sheet A at the cutting line Cy ₁ . Here, the cutting portion 102, since the cut recording sheet A along the line Cx ₁ and the cutting line Cx ₂ by the first slitter 110 and the second slitter 112 first, by cutting with the guillotine cutter 114, the distal end Cut out two prints P on the side.

In the same manner, after cutting, the registration roller pair resumes conveyance of the recording sheet A, conveying at the time when the cutting line Cy ₃ of the distal end side of the second image in the conveyance direction reaches the cutting position by the guillotine cutter 114 Then, the guillotine cutter 114 cuts the recording sheet A at the cutting line Cy ₃ , and then the transport is resumed and the transport is stopped when the rear end side cutting line Cy ₄ reaches the cutting position. guillotine cutter 114 cuts the recording sheet a along the cutting line Cy _4.
As a result, similarly to the above, cutting along the cutting line Cx ₁ and cutting line Cx ₂ and cutting out the two prints P on the rear end side, from the four images recorded on the recording sheet A, four sheets corresponding to the print size Cut out the print P.

On the other hand, as shown in FIG. 7B, when one image is recorded in the conveyance direction, the registration roller pair 116 has the cutting line Cy ₁ on the leading end side of the image at the cutting position by the guillotine cutter 114. At that time, the conveyance of the recording sheet A is stopped, and then the guillotine cutter 114 is operated to cut the recording sheet A at the cutting line Cy ₁ .
After cutting, the registration roller pair 116 resumes the conveyance of the recording sheet A, at the time when the cutting line Cy ₂ in the rear end side of the image becomes cutting position by the guillotine cutter 114, to stop the conveyance of the recording sheet A, Similarly, the guillotine cutter 114 is actuated to cut the recording sheet a along the cutting line Cy _2. As described above, the cutting portion 102, since the cut recording sheet A by the first slitter 110 ahead along line Cx _1, by cutting with the guillotine cutter 114, from one image recorded on the recording sheet A Cut out one print according to the print size.

  The print P cut (cut out from the recording sheet A) by the cutting unit 102 is then conveyed to the arrangement unit 104 and is conveyed from the arrangement unit 104 to the discharge unit 106.

The arrangement unit 104 discharges the print P cut by the cutting unit 102 to the discharge unit 106. Here, when two images are recorded in the width direction on the recording sheet A, the arrangement unit 104 arranges two rows of prints P in the width direction into one row (single row), and outputs the discharge unit 106. To discharge. In the illustrated example, the arrangement unit 104 includes a carry-in roller pair 120, conveyance roller pairs 122, 124 and 132, a discharge roller pair 126, and a single-row roller pair 130.
The discharge unit 106 is a belt conveyor including two rollers 140 and an endless belt 142 stretched around the rollers 140.

The carry-in roller pair 120 of the arrangement unit 104 includes two roller pairs 120 a and 120 b that are arranged in the width direction and can be driven independently of each other.
The one roller pair 120a of the carry roller pair 120 corresponds to the first slitter 110 of the cutting line Cx ₁ cut by the print P (the width direction position) at the time of recording the 2 images in the width direction. The other roller pair 120b corresponds to the second slitter cutting lines Cx ₂ cut by 112 printing P (same as above).

The arrangement unit 104 branches downstream of the carry-in roller pair 120, and includes a lower first conveyance path 134 configured by the conveyance roller pairs 122 and 124, a single-row roller pair 130, and a conveyance roller pair 132. And an upper second transport path 136. The single-row roller pair 130 in the second transport path 136 is a transport roller pair movable in the width direction.
The first conveyance path 134 corresponds to the conveyance path of the roller pair 120a and the roller pair 120b of the carry-in roller pair 120, and the second conveyance path 136 corresponds to the conveyance path of the roller pair 120b. In addition, a guide member (not shown) that guides the print P to the first transport path 134 by acting on the transport path from the roller pair 120a or the roller pair 120b is disposed at the branch position of both transport paths.
Further, the two conveyance paths are joined by a guide member or the like (not shown) downstream of the conveyance roller pair 124 and the conveyance roller pair 132 to reach the discharge roller pair 126.

As shown in FIG. 7A, when two images are recorded in the width direction, the guide member is allowed to act only on the conveyance path from the roller pair 120a of the carry-in roller pair 120.
When the two rows of prints P are conveyed in the cut width direction, the arrangement unit 104 conveys the prints P cut by the first slitter 110 to the first conveyance path 134 by the roller pair 120a and the guide member. On the other hand, the print P cut by the second slitter 112 is conveyed to the second conveyance path 136 by the roller pair 120b.

  In the first transport path 134, the transported print P is transported by transport roller pairs 122 and 124 and sent to the discharge roller pair 126, and the discharge roller pair 126 discharges the print P to the discharge unit 106.

  On the other hand, in the second transport path 136, transport of the transported print P is stopped when the single row roller pair 130 pinches and is separated from the roller pair 120b (the roller pair 120b is also stopped). Next, the single row roller pair 130 is moved in the width direction, and the print P is moved to the position in the width direction corresponding to the roller pair 120a. After the movement in the width direction, the single-row roller pair 130 and the conveyance roller pair 132 are placed so that the print P supplied to the first conveyance path 134 is fed to the conveyance roller pair 126 at the same timing and enters behind it. Then, the conveyance of the print P is started and sent to the discharge roller pair 126. Next, the discharge roller pair 126 discharges the print P to the discharge unit 106.

In the example shown in FIG. 7A, two prints P are also formed in the transport direction.
In this case, the single-row roller pair 130 moves in the opposite direction to the front in the width direction when the previous print P leaves, returns to the original position, and then resumes conveyance by the roller pair 120b. And sent to the second transport path 136. The second transport path 136 transported the print P stops the transport of the print P when the single-row roller pair 130 sandwiches the print P and leaves the roller pair 120b. The printing roller pair 130 is moved in the width direction to move the print P to the position in the width direction corresponding to the roller pair 120a, and then the print P is conveyed by the single-row roller pair 130 and the conveying roller pair 132. The paper is discharged to the discharge unit 106 by the conveyance roller pair 126.
As a result, a plurality of rows of prints P are made into a single row in the width direction and discharged to the discharge unit 106.

On the other hand, as shown in FIG. 7B, when one image is recorded in the width direction, the above-described guide member is applied to the conveyance path from both the roller pairs 120a and 120b.
When the cut print P is conveyed, in the arrangement unit 104, the carry-in roller pair 120 (driven in synchronization with the roller pairs 120a and 120b) and the guide member convey the print P to the first conveyance path 134. In the first conveyance path 134, the print P is conveyed by the conveyance roller pairs 122 and 124 and sent to the discharge roller pair 126, and the discharge roller pair 126 discharges the print P to the discharge unit 106.

  When the discharge unit 106 receives and stacks the prints P that have been transported / discharged by the discharge roller pair 126 on the belt conveyor and stacks the prints by sorting information or the like, A predetermined number of times set according to (maximum length of a matter) is conveyed to the stack of prints P and stopped, and then the next matter of prints P is received.

  The image forming apparatus of the present invention has been described in detail above. However, the present invention is not limited to the above-described embodiments, and various improvements and modifications may be made without departing from the gist of the present invention. Of course.

1 is a conceptual diagram of an example of a printer that uses an image forming apparatus of the present invention. FIG. 2 is a schematic perspective view of an intermediate conveyance roller pair of the printer shown in FIG. 1. FIG. 2 is a conceptual diagram for explaining an example of a fixing operation in the printer shown in FIG. 1. It is a conceptual diagram for demonstrating another example of the effect | action of the fixing in the printer shown in FIG. It is a conceptual diagram for demonstrating another example of the effect | action of the fixing in the printer shown in FIG. It is a conceptual diagram for demonstrating another example of the effect | action of the fixing in the printer shown in FIG. (A) And (B) is a conceptual diagram which shows an example of the image recording in the printer shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Printer 12 (Recording sheet) supply part 14 Image forming part 16 Cutting / arrangement part 20 Magazine 22 Pull-out roller pair 24 Cassette 26 Print head 28 Cutter 30 Exposure part 32 Toner image forming part 34 Transfer part 36 1st intermediate conveyance roller pair ( First conveying roller pair)
37 Second intermediate transport roller pair (second transport roller pair)
38 fixing unit 40 reversing unit 42 exposure control unit 44 exposure unit 46 (electrophotographic) photosensitive drum 48 charging unit 50 cleaning unit 52 toner supply unit 60 transfer belt 62, 86, 140 roller 64 pressure roller 66 transfer roller 68 transport guide 70 , 116 Registration roller 72 First switching means 74 Branch path 76 Kickback part 78 Return conveyance path 80 Second switching means 82 Long roller 84 Short roller 85 Heating roller 88 Fixing belt 90 Cooling part 92 Nip roller 100 Position adjusting part 102 Cutting part 104 Arrangement unit 106 Discharge unit 110 First slitter 112 Second slitter 114 Guillotine cutter 120 Carrying roller pair 122, 124, 132 Conveying roller pair 126 Discharging roller pair 130 Single row roller pair 134 First conveying path 136 Second conveying Road 142 endless belt

Claims (7)

A transfer section for transferring an image to an image receiving medium at a predetermined transfer position;
A fixing unit disposed downstream of the transfer unit and fixing the transferred image by pressurizing the image receiving medium;
And at least one intermediate transport unit disposed between the transfer unit and the fixing unit and configured to sandwich and transport the image receiving medium and to be in a sandwiched state and an open state,
The conveyance length of the image receiving medium from the transfer position to the image fixing position in the fixing unit is shorter than the length in the conveyance direction of the longest image receiving medium in the conveyance direction, and from the transfer position to the most upstream intermediate conveyance means. The transport length of the image receiving medium, the transport length of the image receiving medium between the intermediate transport means, and the transport length from the most downstream intermediate transport means to the fixing position in the fixing unit are the shortest in the transport direction. Shorter than the direction length,
Further, when an image is formed on the longest image receiving medium, the intermediate conveying unit is opened, and the transfer unit finishes the transfer when the leading end of the image receiving medium reaches the fixing unit. When the image is transferred to a position where the image is transferred and the image is formed on the shortest image receiving medium, the intermediate conveying unit is held, and the transfer unit receives the image on the most upstream intermediate conveying unit. An image forming apparatus, wherein an image is transferred to a position where transfer is completed when a leading edge of a medium reaches.   The image forming apparatus according to claim 1, wherein the intermediate conveyance units can be driven independently of each other.   The transfer unit provides a blank at an end in a direction orthogonal to the transport direction to transfer an image to the image receiving medium, and at least the clamping unit on the image transfer surface side of the intermediate transport unit is orthogonal to the transport direction The image forming apparatus according to claim 1, wherein the image forming apparatus is movable in a moving direction and sandwiches a blank portion at a side end of the image receiving medium. When forming an image on an image receiving medium having a length in the conveying direction shorter than the longest image receiving medium and longer than the shortest image receiving medium,
The transfer unit performs transfer to the image receiving medium by providing a blank at the rear end in the transport direction, and the intermediate transport unit is initially in an open state and is in a sandwiched state after the transfer in the transfer unit is completed. The image forming apparatus according to claim 1. When forming an image on an image receiving medium having a length in the conveying direction shorter than the longest image receiving medium and longer than the shortest image receiving medium,
The image forming apparatus according to claim 1, wherein the intermediate conveyance unit is initially in an open state, and gradually enters a clamping state after the leading edge of the image receiving medium reaches the intermediate conveyance unit. When recording a plurality of images at intervals in the transport direction on an image receiving medium having a length in the transport direction shorter than the longest image receiving medium and longer than the shortest image receiving medium,
4. The intermediate conveyance unit according to claim 1, wherein the intermediate conveyance unit is initially in an open state and is held when the image receiving medium reaches the intermediate conveyance unit and the transfer position is between images in the conveyance direction. The image forming apparatus described in 1.   7. The load reducing means is provided in the intermediate transport unit, such that a transport load to the image receiving medium is smaller than a transport load to the image receiving medium in the transfer unit. The image forming apparatus described.

Images