JP2010066600A - Image forming method and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming method for obtaining a full-page image free from wrapping to a fixing roller or any image failure. <P>SOLUTION: The image forming method does not form an image of a leading end side image which is from a leading end in the transporting direction of the recording medium to an optional position toward a rear end in the full-page image that is input, but sets the optional position as the image forming starting position and forms the rear end side image from the image forming starting position to the rear end side of the image to the recording medium, next switches the transporting direction for the recording medium in front-and-rear direction and forms the leading end side image which is the remaining image. For example, when forming a consolidated image, the method starts printing from the rear end side image in the transporting direction of the recording medium with a boundary indicated by a broken line as a starting position for the image formation, transports to a transferring portion again through a front and back reversal section and prints as the image that has the leading end side image rotated 180°. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming method for printing on the entire surface of a recording medium, an image forming apparatus such as a copier, a printer, a facsimile machine, a plotter, and a multifunction machine including at least one of these.

In an electrophotographic image forming apparatus, an electrostatic latent image formed on an image carrier is visualized as a toner image by a developing unit, and the toner image is transferred to a recording medium and then fixed by a fixing unit. ing.
If there is an image at the leading end of the recording medium, the recording medium moves together with the fixing roller due to the close contact between the toner and the fixing roller during fixing, and so-called winding around the fixing roller occurs. When the wound recording medium is peeled off with a separation claw, a vertical stripe-shaped defect image is obtained.
Generally, a predetermined leading edge margin width is provided on the leading end side in the conveyance direction of the recording medium, and the above winding does not occur. The leading edge margin width is set as a device specific value.

JP 2007-024990 A JP 2006-208758 A JP 2006-195347 A JP 2005-017570 A

In this type of image formation, the leading edge margin width cannot always be secured, and there is printing of “entire image” in which an image exists in the leading edge margin width region.
In such a full-surface image printing, the margin width at the front end cannot be secured, and thus the above-described problem due to winding cannot be avoided.

  The main object of the present invention is to provide an image forming method capable of obtaining an entire image free from winding around the fixing roller and image defects.

  In order to achieve the above object, the present invention has a function of preventing wrapping by securing a leading edge margin in the first image forming stage by dividing the entire image and dividing the image forming process onto the recording medium twice. In addition, in the second image forming stage, the wrapping difficulty caused by the fact that the fixed image precedes is used to suppress the wrapping at the fixing portion as a whole.

  Specifically, the invention according to claim 1 is an image forming method using an image forming apparatus having an optical unit, a developing unit, a transfer unit, and a fixing unit for forming an input image on a recording medium, In the image forming method for printing on the entire surface of the recording medium, among the entire input image, the front end side image from the front end to the rear end in the conveyance direction of the recording medium is not formed, and first the arbitrary position Is used as the image formation start position, the rear end side image from the image formation start position to the rear end of the image is formed on the recording medium, and the conveyance direction of the recording medium is then switched back and forth, and the front end side image which is the remaining image is changed. It is characterized by image formation.

According to a second aspect of the present invention, in the image forming method according to the first aspect, the image forming apparatus is provided at a transport path for transporting the fixed recording medium again to the transfer unit, and at an arbitrary position on the transport path. And a front / rear reversing unit for switching the front and rear of the recording medium, and the recording medium is automatically conveyed.
According to a third aspect of the present invention, in the image forming method according to the second aspect, the front / reverse reversing unit has a configuration in which the front and back of the recording medium are reversed and switched back and forth, and then returned to the transport path. It is characterized by that.

According to a fourth aspect of the present invention, in the image forming method according to the second aspect, the recording medium is transported along the transport path without being switched back, and the front / reverse reversing unit turns the recording medium halfway along the transport path. It has the structure which replaces front and back.
According to a fifth aspect of the present invention, in the image forming method according to the third aspect, when double-sided printing other than a full-surface image is performed, only the switchback is performed without reversing the front and back of the recording medium at the front-rear reversing unit. To do.
According to a sixth aspect of the present invention, in the image forming method according to the first or second aspect, in the double-sided printing of the entire surface image, the rear end side image is first formed on the first surface of the recording medium, and then the front-reverse reversing unit. Then, only the switchback is performed to form the rear end side image on the second surface, and then the remaining image on the second surface is imaged. Finally, only the switchback is performed at the front / rear inversion unit to the first surface. The remaining image is formed.

According to a seventh aspect of the present invention, in the image forming method according to the first or second aspect, when the aggregated printing is performed to print the aggregated image, the image forming start position is set as the position of the boundary of the aggregated pages.
According to an eighth aspect of the present invention, in the image forming method according to the first or second aspect, when the aggregated image for printing the aggregated image is not used, the input full-face image has a width equal to or larger than the predetermined leading edge margin width from an arbitrary end. When there is a non-image part, the image forming start position is a position that is directed from the end toward the rear end side by the predetermined front end margin width.
According to a ninth aspect of the present invention, in the image forming method according to the first or second aspect, instead of the aggregated printing for printing the aggregated image, the input full-surface image has a non-printing width not less than the predetermined leading edge margin width from an arbitrary end. When there is no image portion and there are a plurality of objects in the input whole image, the image forming start position is set to a line position including the boundary of the object that is the longest in the main scanning direction. .

According to a tenth aspect of the present invention, in the image forming method according to the first or second aspect, instead of the aggregated printing for printing the aggregated image, a non-exceeding width equal to or greater than the predetermined leading edge margin width from an arbitrary end within the input entire image. When there is no image part and there are a plurality of objects in the input whole image, the image forming start position is set so that the length of the line connecting the image forming start position passing through the image part is the shortest. The position of the line including the boundary of the object.
In the image forming method according to claim 11, in the image forming method according to claim 1 or 2, instead of the aggregate printing for printing the aggregated image, the input full-surface image is not more than the predetermined leading edge margin width from an arbitrary end. When there is no image portion and the input entire image is one object, the image formation start position is set to an arbitrary width of the recording medium by the predetermined margin width at the time of image formation that is not the entire image. It is set as the position which went to the rear end side from the front-end | tip of.
The invention according to claim 12 is characterized in that the image forming method according to any one of claims 1 to 11 can be implemented in the image forming apparatus.

  According to the present invention, it is possible to suppress wrapping in fixing in a full-surface image that forms an image on the leading end of a recording medium. Since it is not necessary to forcefully remove the image with a separation nail, a vertical stripe-shaped defect image does not occur, which can contribute to an improvement in image quality in image formation of the entire surface.

Embodiments of the present invention will be described below with reference to the drawings.
First, a schematic configuration of the image forming apparatus according to the present embodiment will be described with reference to FIGS. FIG. 2 is a diagram illustrating a schematic configuration of the photoconductor unit.
The image forming apparatus (printer) includes four image forming units 1Y, 1C, 1M, and 1K for forming images of each color of yellow (Y), cyan (C), magenta (M), and black (K). ing. Note that the color order of Y, C, M, and K is not limited to that shown in FIG. 1, and may be another order of arrangement.
Each of the image forming units 1Y, 1C, 1M, and 1K includes photosensitive drums 2Y, 2C, 2M, and 2K as image carriers, and a charging unit, a developing unit, and a cleaning unit. The arrangement of the image forming units 1Y, 1C, 1M, and 1K is set so that the rotation axes of the photosensitive drums are parallel to each other and arranged at a predetermined pitch in the transfer sheet moving direction.

Below the image forming units 1Y, 1C, 1M, and 1K, a light source, a polygon mirror, an f-θ lens, a reflection mirror, and the like are provided, and on the surface of each photosensitive drum 2Y, 2C, 2M, and 2K based on the image data. An optical writing unit 3 as an optical means for irradiating while scanning laser light is used as a belt driving device having a transfer conveyance belt 4 that conveys the toner image of each image forming unit in a superimposed manner. A primary transfer unit 5 is arranged.
A cleaning device 6 composed of a brush roller and a cleaning blade is disposed on the outer peripheral surface of the transfer / conveying belt 4 so as to come into contact therewith. The cleaning device 6 removes foreign matters such as toner adhering to the transfer / conveying belt 4.
On the right side of the primary transfer unit 5, a secondary transfer unit 7 serving as a transfer unit that transfers a toner image onto a transfer sheet is disposed, and a fixing unit 8 serving as a belt fixing type fixing unit is provided above the secondary transfer unit 7. .

Under the image forming apparatus, paper feed cassettes 10a and 10b on which a recording medium 9 as a transfer medium is placed are provided. In addition, a manual feed tray 10c that feeds paper manually from the side of the image forming apparatus is provided.
In addition, toner replenishing containers 11Y, 11C, 11M, and 11K are provided, and a waste toner bottle and a power supply unit (not shown) are also provided.
The developing devices 12Y, 12C, 12M, and 12K as developing means are all configured in the same way, and are two-component developing type developing devices that differ only in the color of the toner to be used, and are composed of toner and a magnetic carrier. The agent is contained.
The developing devices 12Y, 12C, 12M, and 12K include a developing roller facing the photosensitive drum 2, a screw that conveys and stirs the developer, a toner concentration sensor, and the like. The developing roller is composed of an outer rotatable sleeve and an inner magnet. In accordance with the output of the toner density sensor, toner is supplied from the toner supply device.

A predetermined voltage is applied to the charging roller 13 from a power source (not shown) to charge the surface of the opposing photosensitive drum 2. The surface of the photosensitive drum 2 charged to a predetermined potential is subsequently scanned with laser light based on image data by the optical writing unit 3 to write an electrostatic latent image. When the surface of the photosensitive drum 2 carrying the electrostatic latent image reaches the developing device 12, toner is supplied to the electrostatic latent image on the surface of the photosensitive drum 2 by the developing roller 14 disposed to face the photosensitive drum 2. A toner image is formed.
The above operation is performed at a predetermined timing in the same manner for all of the photosensitive units 15Y, 15C, 15M, and 15K, and toner images of predetermined colors are formed on the surfaces of the photosensitive drums 2Y, 2C, 2M, and 2K, respectively. .
The recording medium 9 is conveyed from any of the paper feed cassettes 10 a and 10 b or the manual feed tray 10 c and stops once when it reaches the registration roller pair 16.
The toner images on the photosensitive drums 2 are sequentially transferred onto the transfer conveyance belt 4 at the image forming operation timing of the photosensitive units 15Y, 15C, 15M, and 15K. The toner image is transferred from a primary transfer roller 17Y, 17C, 17M, 17K disposed opposite to each of the photosensitive drums 2Y, 2C, 2M, 2K across the transfer conveyance belt 4 from a power source (not shown). 2 is performed by applying a voltage having a polarity opposite to the polarity of the toner on the surface 2.

Then, the toner image that has passed through the position facing the photosensitive drum 2 and overlaid with the four color toner images is transferred onto the recording medium 9 sent out by the registration roller pair 16 as a secondary transfer unit 7 as a transfer means. It is transcribed with.
The recording medium 9 is subsequently conveyed to the fixing unit 8 where the image is fixed by receiving heat and pressure. The recording medium 9 on which the image is formed is discharged to the in-body discharge type discharge tray 18 by each pair of conveying rollers.
Up to this point, an example (image forming method) of a general image forming apparatus using an electrophotographic method has been described.

In the case of a full-surface image, the recording medium 9 is fixed and then conveyed to a front / reverse reversing unit 21 disposed on the upper side of the paper discharge tray 18 where the front and back are reversed and the front / rear side is switched. To the secondary transfer site.
In this embodiment, the front / reverse reversing unit 21 is disposed inside the image forming apparatus, but may be externally attached to the outside of the apparatus main body while being connected to the duplex unit 25. The front / reverse reversing unit 21 also serves as a front / back reversing mechanism (switchback mechanism) of the duplex unit 25.
FIG. 3 is an enlarged view of the front / reverse inversion portion 21 of FIG. 1. The recording medium 9 is
A rear end side image B of the entire surface image is formed, and after fixing, it is conveyed from the right to the left in the drawing by the first conveyance assist roller 22a as indicated by an arrow (1). Then, the recording medium 9 is conveyed in the direction of the arrow (2) by the first reverse assist roller 23a arranged in a direction orthogonal to the first conveyance assist roller 22a.
Next, the front and back of the recording medium 9 are switched by the reverse assist wall 24 and the second reverse assist roller 23b.
The recording medium 9 whose front and back are reversed is conveyed by the second conveyance assist roller 22b with the front F and the rear R being switched in the direction of the arrow (5), and is conveyed to the duplex unit 25 shown in FIG. After the pair 16, the second image formation (image formation of the front end side image A (see FIG. 9A)) on the same surface of the recording medium 9 is entered.

By such a reversing operation (front / reverse reversal + switchback) of the front / rear reversing unit 21, the leading end side of the recording medium 9 at the first image formation becomes the rear end side at the second image formation, and the front and back sides. Is the same surface as the first image formation.
Therefore, in the second image formation, the remaining input image (image data) on which the latent image is formed is an image obtained by rotating the image read in the first image formation 180 degrees back and forth.
In the case where the front / reverse reversing unit 21 has a function of only switchback, it is not different from the conveyance by the conventional duplex unit, and the second image cannot be formed on the same surface of the recording medium 9. Therefore, in this embodiment, (front-reverse inversion + switchback) in the front-rear inversion portion 21 is essential.
However, depending on the arrangement position with respect to the duplex unit 25, the function of the front / reverse reversing unit 21 is not limited to the above function (front / reverse reversal + switchback) as described later.

By starting the image formation from the rear end side image without forming the image from the front end side of the recording medium 9, the front end portion of the recording medium 9 conveyed to the fixing unit 8 becomes a non-image portion or a fixed image portion. It is possible to prevent the fixing unit 8 from being wound around a fixing roller (not shown).
That is, when there is no unfixed image (toner) on the leading end side or there is an image (toner) once fixed on the leading end side when passing through the fixing roller of the fixing unit 8, the fixing roller does not wrap around. A full image can be obtained. First, if there is a margin on the leading edge side, the margin portion of the recording medium does not wrap around the guide as in the leading margin.
In addition, the image once fixed has irregularities, and heat is not easily transmitted to the toner in the second fixing, so that it is difficult to cause wrapping.
At this time, the fixing conditions such as the fixing temperature and the pressure of the fixing nip are not changed at all from normal printing with margins.

A specific example of a flowchart for selecting an image forming start position for the input image and printing the entire image is shown below. This includes that the normal image forming method is selected when the margin width is sufficient on one side. FIG. 4 is a block diagram showing a control mechanism that forms an image by selecting an image formation start position (hereinafter also referred to as “output start position”) from the input image in the flowchart.
As shown in FIG. 4, the control unit (microcomputer; hereinafter also referred to as “control unit”) 30 selects the image formation start position based on information from the image formation start position detection unit (image processing unit) 31. The determination subject in the following control flow is the control means 30.

A first control example will be described based on FIGS. Here, as shown in FIG. 5, an example will be described in which there is a margin at the edge of the sheet that is equal to or larger than the set value a (predetermined margin width), that is, a non-image portion that is equal to or larger than the margin.
First, as shown in FIG. 6, the size of the input image, whether vertical or horizontal, and whether there is a margin at the end of the input image are recognized (S110).
Next, it is determined whether or not there is a margin equal to or greater than the set value a on at least one of the four sides (S111).
As a result, if there is no margin at all, the flow proceeds to a full output flow described later (S113). “Full output” refers to upstream and downstream of the image formation start position in the conveyance direction of the recording medium 9, an upstream area (rear end side image) is formed in the first image formation, and lower in the second image formation. An output method for creating a basin (front-end image).
On the other hand, if there is a margin, it is determined whether a tray can be prepared in which the edge with the margin is in the transport direction while maintaining the input image size and orientation (S112). For example, when the input image is A3, this means that there is A3 in the usable paper feed tray. Therefore, when only a size of A4 or less is set in the usable paper feed tray, the process proceeds to S113.

Further, “a tray with a marginal end in the conveyance direction” means that there is a paper feed cassette in which the margin portion of the input image is the leading edge in the sheet conveyance direction. For example, if an A4 landscape sheet is set, if the input image is an A4 landscape image and has a margin as shown in FIG. 5, YES is obtained in S112. Here, “can be prepared” means whether there is a paper cassette of the size as a setting of the apparatus.
On the other hand, for example, when an A4 landscape sheet is set and the input image at that time has an A4 landscape and a margin position at a position opposite to that shown in FIG. Since printing forms an image at the leading edge, the input image is rotated by 180 ° and printed (S114).
Then, it is determined whether or not the paper is stored in the paper feed cassette having the paper (S115). If the paper is stored, the printing operation is started (S117). If there is no paper, insert the paper. (S116) is displayed on the operation unit, and if the paper is confirmed, the printing operation is started (S117).
As described above, wrapping around the fixing unit can be prevented by selecting the sheet and the input image so that there is no image at the front end in the sheet conveyance direction.

As shown in FIG. 5, when it is not the aggregate printing for printing the aggregate image, and the non-image portion having a predetermined leading edge margin width or more from an arbitrary end is included in the input entire image, the image formation starts. The position is a position from the end toward the rear end side by a predetermined front end margin width. That is, the position of the predetermined margin width becomes the image forming start position, which is not different from the conventional image forming method with a margin.
Even in the case of printing an entire image, an image having a non-image portion at one end may be output. In such a case, the normal “image formation method with margins” is performed as in the above flow. However, when this non-image portion is larger than the leading edge margin setting value, the position (inside the leading edge margin setting value from the end ( A position indicated by a broken line) is output as a whole image start position. As a result, even when color misregistration occurs, it becomes inconspicuous.

In an electrophotographic image forming apparatus, when performing duplex printing, the recording medium is transported to a switchback mechanism, and the recording medium is turned upside down. However, it is not possible to create a full image by the full output only with the configuration of the conventional duplex unit 25.
In the present embodiment, the front and back reversing unit 21 replaces the front and back of the recording medium 9 and reverses the front and back, so that the remaining image is placed on the same surface of the recording medium 9 with the fixed image in the re-imaging. It is possible to create an image.

A second control example will be described based on FIGS.
Here, as shown in FIG. 7, an example in which two images are aggregated will be described.
When the mode for combining two images is selected in the print option, it is determined in S120 that the pages are combined, and in S121, a tray is prepared to make the combined boundary perpendicular to the transport direction while maintaining the input image size. Determine if you can.
Here, “the input image size remains unchanged” is as described in S112 of FIG. Further, “make the aggregated boundaries perpendicular to the conveyance direction” indicates that the boundary line (broken line) is orthogonal to the conveyance direction as shown in FIG. Therefore, in the case of FIG. 9B, since the boundary is the same as the transport direction, the process proceeds to S122 in FIG.

Furthermore, “a tray can be prepared” is as described in S112 of FIG. Further, “the tray is prepared” in S123 is as described in S115 of FIG.
When the condition is satisfied by changing the direction of the tray when the tray is not prepared, for example, “Please change the direction of the paper” is displayed on the operation unit (liquid crystal display unit). (S124).
In S125, printing is started from the image B (rear end side image) in FIG. 9A with the aggregated boundary (the position indicated by the broken line) as the image formation start position, and passes through the front / reverse reversing unit 21 described above. Then, it is conveyed again to the secondary transfer site, and the image A (front end side image) is printed as an image rotated by 180 °.
In this way, even if two images are aggregated, the input image is selected and printed so that there is no image at the leading edge in the sheet conveyance direction in the first image formation, and thus to the fixing unit. Can be prevented.
In the second image formation, it is difficult to wrap around the image because the fixed image precedes as described above.
Further, by setting the boundary between pages as the image forming start position, even if color misregistration occurs, it can be made inconspicuous.

A third control example will be described based on FIGS. 10 and 11.
Here, as shown in FIG. 10, an example of an input image composed of only one object (independent image) with no margin will be described.
If the aggregation mode is not set in S122, it is determined that the input image is composed of only one object, and the flow shown in S126 and after.
In this case, since there is an image at the front end in the sheet conveyance direction, an image B in FIG. 9A (rear side) is set with a position (a position indicated by a broken line) from the front end of the sheet toward the rear end corresponding to the front margin setting value. Printing is started from the end-side image), and is conveyed again to the secondary transfer portion via the front-reverse reversing unit 21 described above, and the image A (tip-side image) is printed as an image rotated by 180 °.
In this way, even if the image has no margin at the end of the sheet, the input image is selected and printed so that there is no image at the leading edge in the sheet conveyance direction, thereby preventing the fixing portion from being wound. be able to.

A fourth control example will be described based on FIGS.
Here, as shown in FIG. 12, an example of an input image composed of a plurality of objects will be described.
First, it is determined whether or not there is one or more lines that do not cross the object inside the end margin setting value in each continuous line passing through the boundary of the object (S133).
Here, when there is a corresponding line (YES), the same flow as that after S121 in FIG. 7 described above is followed except that a line that does not cross the object is set as the output start position.
By doing this, even if there is an object in the leading edge margin width, the input image is printed separately at the upstream and downstream in the transport direction at the boundary position with each object, so that the winding around the fixing unit is prevented. Can be prevented.
In the case of NO in S133 and S134 in FIG. 13, the process proceeds to “Border selection full output” described below (S135).

A fifth control example will be described based on FIGS. 14 and 15.
Here, as shown in FIG. 14, an example of an input image having an object boundary only on the edge side of the leading edge margin setting value will be described.
As shown in FIG. 15, in the boundary selection full face output, it is determined whether or not there is an object boundary only at the end side from the leading margin setting value (S136). .
That is, the image forming start position is set to a position (a position indicated by a broken line) from the front end to the rear end in the conveyance direction of the recording medium by the predetermined front end margin width at the time of image formation which is not a full image (S144). ). Thereby, even when color misregistration occurs, it can be made inconspicuous.
In the case of NO, the process proceeds to S137 in FIG.

A sixth control example will be described based on FIGS. 16 and 17.
Here, as shown in FIG. 16, an example of an input image in which one or more sets of lines connected at the boundary of the object are only inside the leading edge margin setting value will be described.
This example corresponds to “when there is no non-image part within a specified leading edge margin width from an arbitrary edge in the input full image and there are multiple objects in the input full image”. The image start position is the position of a line including the boundary of the object that is the longest in the main scanning direction (direction perpendicular to the conveyance direction of the recording medium).
Thereby, even when color misregistration occurs, it can be made inconspicuous.

A seventh control example will be described based on FIGS. 18 and 19.
Here, as shown in FIG. 18, an input image that does not satisfy the conditions of the fifth example and the sixth example will be described as an example.
As shown in FIG. 19, first, priorities are given to possible start lines in the order of shortest length across the object (S149).
This example corresponds to “when there is no non-image part within a specified leading edge margin width from an arbitrary edge in the input full image and there are multiple objects in the input full image”. The image start position is the position of a line that includes the boundary of the object such that the length of the line connecting the image formation start positions through the image portion is the shortest.
As described above, even in the case of printing the entire image, when a plurality of objects are present in the image, the line including the plurality of boundaries is set as the image forming start position. Thereby, even when color misregistration occurs, it can be made inconspicuous.

As described above, in the present invention, since an entire image is obtained by two image formations, color misregistration may occur. In many cases, an image to be output as a full image has no margin in one object. In addition, it is expected that there is something most desired to be expressed near the center of the image.
By setting the image formation start position to the border of the page or the non-image part larger than the leading margin width, the boundary of the object, or the edge of the recording medium, even if color misregistration occurs due to the second image formation, It can be inconspicuous.

In the above embodiment, single-sided printing of a full-screen image has been described, but double-sided printing is also possible.
In the double-sided printing of the entire image, first, the rear end side image is formed on the first surface of the recording medium 9, and then only the switchback is performed by the front / rear reversing unit 21, which is conveyed by the duplex unit 25, and the front and back sides are reversed. A rear end side image is formed on the second surface.
Next, as in the case of full-side output on one side, the front / reverse reversing unit 21 performs front / back reversal and front / rear switching, and the double-sided unit 25 forms the remaining image on the second side. Only the back is carried and conveyed by the duplex unit 25, and the remaining image on the first surface is formed by inverting the front and back.
In this way, the number of times that the recording medium 9 is reversed upside down by the front / rear reversing unit 21 can be suppressed at a time, and the image forming time of the double-sided image can be shortened.
That is, when an entire image is obtained on one side and then an entire image is obtained on the other side, the recording medium 9 is inverted two times in total in the front / rear inversion unit 21.
As described above, by forming images on both sides halfway, and then forming the remaining images on both sides, it is possible to suppress inversion of the front and back in the front-reverse reversing unit 21 only once, and to shorten the image formation time of both-side images. it can.

The configuration for switching the front and rear of the recording medium 9 is not limited to the configuration of the front and rear inversion unit 21. For example, as shown in FIG. 20, a front / reverse reversing unit 35 having a turntable 26 and a recording medium holder 27 is provided, and this front / rear reversing unit 35 is provided on a transport path 36 having no switchback mechanism as shown in FIG. Therefore, it is possible to reverse the front and back, and to enter the second image formation. In this case, the front / reverse inversion unit 35 does not have a front / back inversion function.
Although not shown, the conveyance roller pair in the vicinity of the front / reverse reversing unit 35 is configured to contact and separate in response to the turntable 26 and the like. In FIG. 21, the code | symbol 37 has shown the branch nail | claw.
The front / reverse reversing unit 35 may be provided at the position of the front / rear reversing unit 21 in FIG. 1 and may be switched back again at an arbitrary position on the conveyance path of the duplex unit 25.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. It is an enlarged view of an image forming unit. It is a perspective view which shows the mechanism of a front-back inversion part. It is a control block diagram. It is a figure which shows the target image in the 1st control example. It is a flowchart in the 1st control example. It is a figure which shows the target image in the 2nd control example. It is a flowchart in the 2nd control example. FIG. 6 is a diagram illustrating a positional relationship of a boundary line of an aggregate image with respect to a conveyance direction of a recording medium. It is a figure which shows the target image in the 3rd control example. It is a flowchart in the 3rd control example. It is a figure which shows the target image in the 4th control example. It is a flowchart in the 4th example of control. It is a figure which shows the target image in the 5th control example. It is a flowchart in the 5th control example. It is a figure which shows the target image in the 6th control example. It is a flowchart in the 6th control example. It is a figure which shows the target image in the 7th control example. It is a flowchart in the 7th example of control. It is a perspective view which shows the other example of the front-back inversion part. It is a figure which shows the conveyance path | route which has arrange | positioned the front-back inversion part shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 Optical means 7 Transfer means 8 Fixing means 9 Recording medium 12 Developing means 21, 35 Front-reverse reversing part 25 Transport path A Front end side image B Rear end side image

Claims (12)

In an image forming method using an image forming apparatus having an optical unit, a developing unit, a transfer unit, and a fixing unit for forming an input image on a recording medium, and printing on the entire surface of the recording medium,
Of the entire image to be input, the front side image from the front end to the rear end in the conveyance direction of the recording medium is not formed, and first, the arbitrary position is set as the image start position, and the image start position An image forming method, comprising: forming a rear end side image from the image to the rear end of the image on a recording medium; then, changing a conveyance direction of the recording medium forward and backward to form the front end side image which is a remaining image. The image forming method according to claim 1.
The image forming apparatus includes:
A transport path for transporting the fixed recording medium to the transfer means again;
A front-rear reversing unit that is provided at an arbitrary position in the transport path and replaces the front and rear of the recording medium;
And an image forming method for automatically conveying a recording medium. The image forming method according to claim 2.
The image forming method according to claim 1, wherein the front / reverse reversing unit has a configuration in which the front and back of the recording medium are reversed and switched back and forth, and then returned to the transport path. The image forming method according to claim 2.
An image forming method characterized in that a recording medium is conveyed along the conveyance path without being switched back, and the front / reverse reversing unit is configured to turn the recording medium in the middle of the conveyance path to change the front and rear. The image forming method according to claim 3.
An image forming method characterized in that, during double-sided printing other than a full-surface image, only the switchback is performed without reversing the front and back of the recording medium at the front-reverse reversing unit. The image forming method according to claim 1 or 2,
In double-sided printing of the entire image, first, a rear end image is formed on the first surface of the recording medium, and then only the switchback is performed at the front and rear reversing unit to form a rear end image on the second surface. Next, the remaining image on the second surface is formed, and finally the remaining image on the first surface is formed by performing only the switchback at the front and rear inversion unit. The image forming method according to claim 1 or 2,
An image forming method, wherein at the time of aggregate printing for printing an aggregate image, the image forming start position is set as a boundary position of aggregated pages. The image forming method according to claim 1 or 2,
In the case of non-aggregated printing for printing an aggregated image, if there is a non-image part that is equal to or larger than the predetermined leading edge margin width from an arbitrary end in the input entire image, the image forming start position is An image forming method, wherein the position is set toward the rear end side by a predetermined front end margin width. The image forming method according to claim 1 or 2,
When there are a plurality of objects in the input full image when there is no non-image portion that is larger than the predetermined margin width from an arbitrary end in the input full image, instead of the collective printing for printing the integrated image The image forming method is characterized in that the image forming start position is a line position including the boundary of the object that is the longest in the main scanning direction. The image forming method according to claim 1 or 2,
When there are a plurality of objects in the input full image when there is no non-image portion that is larger than the predetermined margin width from an arbitrary end in the input full image, instead of the collective printing for printing the integrated image The image forming method is characterized in that the image forming start position is a position of a line including the boundary of an object such that the length of the line connecting the image forming start positions passing through the image portion is the shortest. The image forming method according to claim 1 or 2,
When the input whole image is a single object when there is no non-image portion having a width equal to or larger than the predetermined leading edge margin width from an arbitrary end in the input whole image instead of the aggregate printing for printing the aggregate image. The image forming method is characterized in that the image forming start position is a position directed from the arbitrary leading edge of the recording medium toward the trailing edge by the predetermined margin width at the time of image formation which is not a full-surface image. .   An image forming apparatus capable of performing the image forming method according to claim 1.

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