JP4758360B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to a copying machine, a printer, a facsimile, a plotter, or the like employing an image forming system such as an electrophotographic system, an electrostatic recording system, an ionography, a magnetic recording system, etc. for recording on a single sheet-like recording medium. The present invention relates to an image forming apparatus such as a multifunction peripheral having a function.

  Copiers, printers, facsimiles, plotters, etc. that employ image forming methods such as electrophotographic methods, electrostatic recording methods, ionography, magnetic recording methods, etc., which record on a single-sheet recording medium, or a plurality of these functions Image forming apparatuses such as multifunction peripherals, and in particular, transfer apparatuses using a transfer member that transfers a visible image on an image carrier such as a photosensitive drum or an intermediate transfer body onto a sheet-like transfer medium (for example, paper) and the like In the image forming apparatus, when the transfer medium enters the transfer pressure contact portion between the image carrier or the intermediate transfer member and the transfer member, speed fluctuations of the image carrier or the intermediate transfer member occur and image degradation occurs. The following proposals have been made regarding a transfer device and an image forming apparatus that suppress this image deterioration, that is, the speed fluctuation of the image carrier or the intermediate transfer member (see, for example, Patent Documents 1 to 3).

  For example, in Japanese Patent Application Laid-Open No. 2004-109706, a damper device that applies a load (viscous load) proportional to a rotational speed to a drive source or a drive roller constituting an endless belt drive system is provided, or an endless belt is provided. It has been proposed to absorb the impact force by providing a damper device or a flywheel that applies a load (viscous load) to the shaft of the roller member that contacts the endless belt near the drive roller.

  In Japanese Patent Application Laid-Open No. 61-198180, the rotation center axis of the carrier drum is used for the purpose of making the impact, pressure distribution uniform when the transfer material enters between the carrier drum and the transfer roller and when it is discharged. It has been proposed to convey the transfer material to the contact portion between the carrier drum and the transfer roller at a certain angle (crossing angle θ) with respect to the perpendicular direction.

  Japanese Patent Laid-Open No. 6-266147 discloses a cardboard sheet in which at least one of the leading edge and the trailing edge is obliquely cut in order to suppress a jitter that occurs when the cardboard sheet for copying machines and printers enters or leaves the roller pair. It has been proposed to use

JP 2004-109706 A JP-A-61-198180 JP-A-6-266147

  However, in the technique described in Japanese Patent Application Laid-Open No. 2004-109706, a space is required to provide the damper device and the flywheel, and the device is expensive. Therefore, there is a problem that the device becomes expensive and large in size. is there.

  The technique described in Japanese Patent Laid-Open No. 61-198180 can be configured more simply than the technique described in Japanese Patent Application Laid-Open No. 2004-109706, but a reliable operation is obtained in order to change the transport angle when the transfer material passes. There is a problem that it is difficult.

  Further, the technique described in Japanese Patent Laid-Open No. 6-266147 solves the problems of the techniques described in Japanese Patent Application Laid-Open No. 2004-109706 and Japanese Patent Application Laid-Open No. 61-198180 to some extent. Although possible, there is a problem in that a specially shaped paper is required and general paper cannot be used.

  The present invention has been made in view of the above-described circumstances, and uses a transfer member that transfers a visible image on an image carrier such as a photosensitive drum or an intermediate transfer member onto a sheet-like transfer medium. In the transfer device and the image forming apparatus, when the transfer medium enters the transfer pressure contact portion between the image carrier and the transfer member, the transfer device and the image deterioration prevent the image carrier and the intermediate transfer member from changing in speed. It is a main object to realize and provide an image forming apparatus that does not have any.

In order to solve the above-described problems and achieve the above-described object, the invention according to each claim employs the following characteristic means and configuration.
According to the first aspect of the present invention, after the visible image formed on the image carrier is transferred to the intermediate transfer member by the primary transfer unit, the visible image transferred on the intermediate transfer member is transferred via the conveyance path. In the image forming apparatus for forming an image by transferring to a single sheet-like transfer medium conveyed by a secondary transfer means by a secondary transfer means, the transfer pressure contact portion of the transport path connected to the transfer pressure contact portion The first cutting means capable of cutting in such a shape that the contact area of the transfer medium with respect to the transfer pressure contact portion gradually decreases from the portion near the rear end to the front end of the transfer medium from the front end to the front end. Features.

  According to the second aspect of the present invention, the visible image formed on the image carrier is transferred to a single-sheet-shaped transfer medium conveyed through a conveyance path by a transfer means at a transfer pressure contact portion to form an image. In the image forming apparatus, the contact area of the transfer medium with respect to the transfer pressure contact portion is upstream of the transfer pressure contact portion of the transport path connected to the transfer pressure contact portion and is closer to the rear end of the front end portion of the transfer medium. 1st cutting means which can be cut | judged to the shape which becomes small gradually from a part to the front-end | tip is arrange | positioned.

  According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the first cutting means is used so that the transfer pressure contact portion extends from one side end to the other side end of the front end portion of the transfer medium. It is characterized by cutting at a certain angle.

  According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, the guide member that contacts the other side end opposite to the one side end of the transfer medium that first enters the transfer pressure contact portion, It is characterized by being arranged so as to be orthogonal to the transfer pressure contact portion.

  According to a fifth aspect of the present invention, in the image forming apparatus according to the first or second aspect, the first cutting means is used as a reference with respect to the transfer pressure contact portion with respect to the center in the transport direction at the front end portion of the transfer medium. The leading edge of the transfer medium is cut so that it protrudes downstream in the transport direction from the center of the transfer medium to the both ends, or protrudes upstream in the transport direction from both ends of the transfer medium to the center. It is characterized by.

According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, a fixing unit that fixes the image transferred at the transfer pressure contact portion, and a fixing path through the conveyance path. And a discharge means for discharging the fixed transfer medium connected in this manner, and a leading end portion of the transfer medium cut by the first cutting means is disposed on the transport path between the discharge means and the fixing means. A second cutting means capable of cutting is arranged.
According to a seventh aspect of the present invention, in the image forming apparatus according to the sixth aspect, the second cutting means is used to perform the first cutting so that the front end of the transfer medium is perpendicular to the transfer medium transport direction. It is characterized in that the leading end of the transfer medium cut by the means is cut.

According to the present invention, a novel image forming apparatus can be provided by solving the above-described problems. The main effects of the invention are as follows.
That is, according to the present invention, when the sheet-like transfer medium enters the transfer pressure contact portion between the image carrier and the transfer means, or the sheet-like transfer medium enters the transfer pressure contact portion between the intermediate transfer body and the secondary transfer means. In addition, it is possible to easily construct a transfer device that prevents speed fluctuations that occur in an image carrier and an intermediate transfer member and an image forming device that does not have image degradation.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention including examples will be described with reference to the drawings. In each embodiment and the like, components (members and components) having the same function, shape, and the like will be omitted by giving the same reference numerals after being described once. In the figure, components that are configured in a pair and do not need to be specifically distinguished and described are described by appropriately describing one of them for the sake of simplification of description. In order to simplify the drawings and the description, even if the components are to be represented in the drawings, the components that do not need to be specifically described in the drawings may be omitted as appropriate. When quoting and explaining constituent elements such as published patent gazettes, the reference numerals are shown in parentheses to distinguish them from those of the embodiments.

First, the overall configuration of a tandem indirect transfer / electrophotographic color copying machine to which the present invention is applied will be described with reference to FIG. This copying machine includes a transfer member for transferring a visible image on an image carrier such as a photosensitive drum or an intermediate transfer member to a single-sheet recording medium (hereinafter also referred to as “transfer medium” or “sheet”). It is an example of the image forming apparatus provided with the used transfer apparatus.
In the figure, reference numeral 100 denotes a copying apparatus main body, 200 denotes a paper feed table on which the copying apparatus main body 100 is placed, 300 denotes a scanner mounted on the copying apparatus main body 100, and 400 denotes an automatic document feeder (400) mounted on the scanner 300. ADF) is shown respectively.

In the center of the copying apparatus main body 100, an endless belt-like intermediate transfer member 10 is provided. Although not shown in the drawing, the intermediate transfer member 10 is formed by forming a base layer made of a material that is difficult to stretch, such as canvas, on a fluorine-based resin or a rubber material that has a large elongation, and an elastic layer is provided thereon. . This elastic layer is made of, for example, fluorine rubber or acrylonitrile-butadiene copolymer rubber. The surface of the elastic layer is, for example, coated with a fluorine resin and covered with a smooth coat layer.
As shown in FIG. 9, the intermediate transfer member 10 is configured to be able to rotate and convey clockwise in the drawing by being wound around three support rollers 14, 15, and 16 in the illustrated example.

In this illustrated example, an intermediate transfer member cleaning device 17 for removing residual toner remaining on the intermediate transfer member 10 after image transfer is provided on the left side of the second support roller 15.
Further, four image forming units 18 of yellow, cyan, magenta, and black are provided on the intermediate transfer member 10 stretched between the first support roller 14 and the second support roller 15 along the conveyance direction. A tandem image forming apparatus 20 is arranged side by side. An exposure device 21 is further provided above the tandem image forming apparatus 20.

  On the other hand, a secondary transfer device 22 as a secondary transfer unit is disposed on the opposite side of the intermediate transfer body 10 from the tandem image forming device 20. In the illustrated example, the secondary transfer device 22 is configured by spanning a secondary transfer belt 24 that is an endless belt between two rollers 23 and 23, and further the third support roller 16 via the intermediate transfer body 10. The image on the intermediate transfer member 10 is transferred to the sheet at the transfer pressure contact portion formed here. Incidentally, a switching means (not shown) is provided on the roller 23 side, and the secondary transfer belt 24 on the roller 23 side can be brought into and out of contact with the intermediate transfer member 10 at an appropriate time by driving.

A fixing device 25 is provided on the left side of the secondary transfer device 22 as a fixing unit for fixing the transferred image on the sheet. The fixing device 25 is configured by pressing a pressure roller 27 against a fixing belt 26 that is an endless belt.
The secondary transfer device 22 described above also has a sheet transport function for transporting the image-transferred sheet to the fixing device 25. Of course, a transfer roller or a non-contact charger may be disposed as the secondary transfer device 22, but in such a case, it is difficult to provide the sheet conveying function together.
In the illustrated example, a sheet reversing device 28 for reversing the sheet so as to record an image on both sides of the sheet is substantially parallel to the tandem image forming device 20 and below the secondary transfer device 22 and the fixing device 25. Is arranged.

Next, the operation will be described. When making a copy using the color copying machine shown in FIG. 9, a document is set on the document table 30 of the automatic document feeder 400 or the automatic document feeder 400 is opened and the contact glass of the scanner 300 is opened. A document is set on the document 32, the automatic document feeder 400 is closed, and the document is pressed by it.
When a start switch (not shown) is pressed, when the document is set on the automatic document feeder 400, the document is transported and moved onto the contact glass 32, and then the document is set on the contact glass 32. When the scanner 300 is immediately driven, the first traveling body 33 and the second traveling body 34 travel. Then, the first traveling body 33 emits light from the light source and further reflects the reflected light from the document surface toward the second traveling body 34, and is reflected by the mirror of the second traveling body 34 and passes through the imaging lens 35. The light enters the reading sensor 36 and reads the document content.

  Further, when a start switch (not shown) is pressed, one of the three support rollers 14, 15, 16 is rotationally driven by a drive motor (not shown), and the other two support rollers are driven to rotate. The transfer body 10 is rotated and conveyed. At the same time, in each image forming unit 18, the photosensitive member 40 as an image carrier is rotated, and black, yellow, magenta, and cyan single-color images are formed on the respective photosensitive members 40. Then, along with the conveyance of the intermediate transfer member 10, these single color images are sequentially transferred by a transfer roller 62 as a primary transfer unit, and a composite color image is formed on the intermediate transfer member 10.

  On the other hand, when a start switch (not shown) is pressed, one of the paper feed rollers 42 of the paper feed table 200 is selected and rotated, so that a sheet is fed from one of the paper feed cassettes 44 provided in the paper bank 43 in multiple stages. The fed sheets are separated one by one by the separation roller 45 and fed to the paper feed path 46, and further conveyed by the conveyance roller 47 and guided to the paper feed path 48 in the copier body 100, The resist roller pair 49 is abutted against the nip portion and temporarily stopped.

  On the other hand, when the sheet is conveyed by using the manual feed tray 51, the sheet on the manual feed tray 51 is fed out by rotating the paper feed roller 50 provided in the manual feed tray 51 placement section. Are separated one by one by the separation roller 52 and fed to the manual paper feed path 53, and are stopped once abutting against the front portion of the nip portion of the registration roller pair 49 as described above.

Then, the registration roller pair 49 is rotated in time with the composite color image on the intermediate transfer body 10, so that the sheet is transferred to the transfer pressure contact portion formed between the intermediate transfer body 10 and the secondary transfer device 22. Then, the image is transferred by the secondary transfer device 22 and a color image is recorded on the sheet.
The sheet after the image transfer is conveyed by the secondary transfer device 22 and sent to the fixing device 25, and heat and pressure are applied by the fixing device 25 to fix the transferred image. Then, the sheet is conveyed and discharged by a discharge roller pair 56 as discharge means and stacked on a discharge tray 57. Alternatively, it is switched by the switching claw 55 and conveyed to the sheet reversing device 28 where it is reversed and guided again to the transfer position / transfer pressure contact portion, and an image is recorded on the back surface, and then discharged by the discharge roller pair 56. It is discharged onto the tray 57.

On the other hand, the intermediate transfer body 10 after image transfer is prepared for re-image formation by the tandem image forming apparatus 20 by removing residual toner remaining on the intermediate transfer body 10 after the image transfer by the intermediate transfer body cleaning device 17. It becomes.
Here, the registration roller pair 49 is generally used while being grounded, but it is also possible to apply a bias for removing paper dust from the sheet.

  In the color copying machine as shown in FIG. 9, the driving accuracy of the intermediate transfer belt as the intermediate transfer member has a great influence on the quality of the final image, and higher accuracy driving is desired.

FIG. 10 shows an example of the conventional transfer apparatus shown in FIG. In FIG. 10, symbol X indicates the sheet conveying direction, and Y indicates the sheet width direction orthogonal to the sheet conveying direction. In FIG. 10, the intermediate transfer member 10 (hereinafter also referred to as “intermediate transfer belt 10”) and the secondary transfer belt 24 are not shown (the same applies to FIGS. 2, 7, 8 and the like described later).
Conventionally, the registration roller pair 49, the support roller 16, and the roller 23 are installed in parallel to the axial direction, and the single sheet S is rectangular, and the entire sheet width direction Y of the front end Sa of the sheet S is the same. In other words, the sheet S is conveyed in the sheet conveying direction X so as to directly abut against the registration roller pair 49 and the support roller 16 over the entire sheet width direction Y of the leading portion of the sheet S. In this configuration, when the sheet S enters the transfer pressure contact portion between the intermediate transfer belt 10 and the secondary transfer belt 24 via the support roller 16, it is applied to the intermediate transfer belt 10 via the support roller 16 as a load fluctuation. Therefore, as shown in FIG. 11, a large speed fluctuation occurs in the intermediate transfer belt 10.
In FIG. 11, the elapsed time is plotted on the horizontal axis and the linear velocity is plotted on the vertical axis, and the intermediate transfer belt 10 has a change in speed when the sheet S enters the transfer pressure contact portion with the intermediate transfer belt 10. It shows the transition state of the magnitude and vibration of the linear velocity. Although there are some differences depending on the sheet size, the sheet thickness, etc., it has been confirmed by a number of experiments and the like that the same tendency as shown in FIG. 11 is exhibited regardless of the sheet type.

(First embodiment)
FIG. 1 shows a color copying machine as an example of an image forming apparatus showing a first embodiment to which the present invention is applied. The color copying machine shown in FIG. 1 is upstream of the transfer pressure contact portion of the conveyance path connected to the transfer pressure contact portion between the intermediate transfer belt 10 and the secondary transfer belt 24, as compared with the conventional one shown in FIG. A sheet cutting device 401 as a first cutting unit that cuts the leading end of the sheet S as a sheet into a predetermined shape near the registration roller pair 49 (here, immediately before the registration roller pair 49). And the leading edge of the sheet S cut in the vicinity of the discharge roller pair 56 on the conveyance path between the fixing device 25 and the discharge roller pair 56 (here, the position immediately before the discharge roller pair 56). The main difference is that a sheet cutting device 402 serving as a second cutting means for cutting the sheet so as to have a substantially original shape is disposed. The color copying machine of this embodiment is the same as the color copying machine shown in FIG. 9 except for the differences.

  In the sheet cutting device 401, as shown in FIG. 2, the leading edge or the leading edge of a rectangular sheet S having, for example, a length L side in the sheet conveying direction X is set to one side end side that is a cutting input end side. Is cut into a trapezoid by inclining about 1-2 mm with a cutting margin C. That is, from one side end to the other side end of the leading edge of the sheet S, the transfer pressure contact portion (the front side to the back side of the paper surface at the transfer pressure contact portion formed between the intermediate transfer belt 10 and the secondary transfer belt 24). The same applies to the center line of the nip portion formed over the entire length of the nip portion, and the support roller 16 disposed in parallel to the nip portion. In FIG. 2, a portion indicated by a two-dot chain line at the leading end portion of the paper S represents a portion that is cut and removed by the paper cutting device 401. L is the length of one side edge and the other side edge of the sheet S before being cut, and L1 is one side of the sheet S cut from the one side edge at the leading edge of the sheet S by the cutting allowance C. It represents the length of the side on the end side, and L−L1 = C (about 1 to 2 mm) (hereinafter the same).

  As a result, the relative angle between the leading edge Sa of the sheet S and the transfer pressure contact portion or the support roller 16 can be obtained, and the leading end Sa (sheet leading end line) of the sheet S extends simultaneously in the sheet width direction Y to the transfer pressure contacting portion. Since the rush can be avoided, the rush load fluctuation (the fluctuation of the amplitude shown in FIG. 11) to the transfer pressure contact portion of the leading end Sa of the sheet S is reduced, and the speed fluctuation at the time of the rush of the intermediate transfer belt 10 is reduced. Can be suppressed.

In the paper cutting device 402, as shown in FIG. 3, it is cut into a trapezoid by the paper cutting device 401, and the leading edge of the paper S shown in FIG. Specifically, the other side end side of the sheet S, which has been cut to the length L1 in FIG. 2, is cut at the same cutting margin C as in FIG. The shape is arranged in a rectangle having a length L1 on both sides of the one side end and the other side end.
As a result, an image-formed sheet S (copy) having a size substantially the same as the original rectangle is obtained. Although the image-formed paper S is cut in a small amount at the margin, there is no problem in general use.

FIG. 4 shows details of the sheet cutting device 401. As shown in FIG. 4, the sheet S is temporarily stopped before the registration roller pair 49. After that, cutting is performed as shown in FIG. 2, which is performed by fixing a cutting device 702 such as a cutter to the paper cutting device 401 and moving the cutting device 702 in a predetermined arrow A direction. . In the drawing, a portion indicated by a two-dot chain line represents a cutting line of the paper S cut by the cutting tool 702.
In order to move the cutting device 702 in the direction of arrow A, the paper cutting device 401 is a guide member (not shown) provided with a groove into which the cutting device 702 is inserted, and an endless machine that can move while the cutting device 702 is fixed. A belt (not shown), a plurality of pulleys (not shown) that wrap around the belt so as to be able to travel, and a drive motor (not shown) as drive means for driving one of the plurality of pulleys. Equipment.

  FIG. 8 shows details of the sheet cutting device 402. The sheet S is temporarily stopped before the discharge roller pair 56. Thereafter, the sheet is cut as shown in FIG. 3. This is done by fixing a cutting device 802 such as a cutter to the sheet cutting device 402, and in a predetermined arrow B direction, that is, the axial direction of the discharge roller pair 56 and the sheet width. This is performed by moving the cutting tool 802 in a direction parallel to the direction Y. In the drawing, a portion indicated by a two-dot chain line represents a cutting line of the paper S that is cut by the cutting tool 802. The paper cutting device 402 has substantially the same configuration as the paper cutting device 401.

  Note that the first and second cutting means are not limited to the paper cutting devices 401 and 402 simply shown as described above, and any known sheet cutting device can be selected and employed. For example, a movable blade is formed in the sheet width direction Y according to the cutting line shape, and the movable blade is lifted and lowered by a cam and a drive motor connected thereto with respect to a fixed blade that is also fixed in the sheet width direction Y. The so-called guillotine-type cutting device that is driven and the well-known cutting / cutting device that cuts while moving the rotating blade as the movable blade according to the cutting line shape, etc., take into consideration the cutting shape, its advantages and cost as appropriate May be adopted.

(Modification 1)
As shown in FIG. 2, when the leading edge of the sheet (sheet) whose edge is cut obliquely is conveyed and plunged into a nip portion such as a roller pair, the leading edge of the sheet is simultaneously nipped over the entire sheet width direction. Since the sheet does not enter or contact the part, the sheet may be rotated while being conveyed, or there is a concern. Therefore, as in Modification 1 shown in FIG. 6, a plan view immediately before the nip portion between the pressure roller 27 and the fixing belt 26 forming the nip portion upstream of the registration roller 16 pair and the discharge roller pair 56 is shown. At the one end (length L1) opposite to the other end (length L), which is the longer side of the sheet S cut into a trapezoidal shape, the transfer pressure contact portion, the support roller 16 or the additional pressure is applied. A guide plate 901 as a guide member is installed close to the transfer pressure contact portion, the support roller 16 or the pressure roller 27 so as to be orthogonal to the pressure roller 27. As a result, as shown in FIG. 6, the leading edge Sa of the sheet S cut obliquely enters the registration roller 16 pair, the transfer pressure contact portion, or the nip portion of the pressure roller 27 at the same time in the entire sheet width direction. Even without this, the rotation of the paper S can be suppressed. The first modification is the same as the first embodiment except for the contents described above.
It goes without saying that the first modification also exhibits the basic effects described in the basic effect column of the first embodiment.

(Modification 2)
7 and 8 show another modification 2 that does not require the guide plate 901 shown in FIG.
In the example shown in FIG. 7, with respect to the center of the sheet conveyance direction X at the leading end portion of the sheet S, the transfer pressure contact portion protrudes downstream from the center CL of the sheet S to both side ends in the sheet conveyance direction X. In this case, the sheet cutting device 401 is operated so as to cut the leading end of the sheet S so that the leading end of the sheet S is convex upward and has a certain angle with respect to the transfer pressure contact portion with respect to the center CL. Is. In other words, the leading edge of the sheet S is cut into an isosceles triangle shape that is convex upward in a plan view with the center of the sheet conveying direction X at the leading edge of the sheet S as a reference.
In the example shown in FIG. 8, with respect to the center of the sheet conveyance direction X at the leading edge of the sheet S, the transfer pressure contact portion protrudes upstream of the sheet conveyance direction X from the center CL of the sheet S to both side edges. Then, the sheet cutting device 401 is operated so as to cut the leading end of the sheet S with the leading end of the sheet S protruding downward with respect to the transfer pressure contact portion with respect to the center CL and having a certain angle. It is something to be made. That is, cutting is performed so that the front end portion of the paper S has an isosceles triangle shape that protrudes downward in a plan view, with the center in the sheet conveyance direction X at the front end portion of the paper S as a reference. The second modification is the same as the first embodiment except for the contents described above.

  According to the second modification, the leading end of the sheet S is cut into a specific shape as described above, so that the leading end Sa of the sheet S is simultaneously aligned with the registration roller 16 pair and the transfer pressure contact portion over the entire sheet width direction. Alternatively, even if the pressure roller 27 does not enter the nip portion, no inclined force is generated at the time of entry, and therefore the rotation of the sheet S can be suppressed without the guide plate 901 shown in FIG. Also in the second modification, the basic effect described in the basic effect column of the first embodiment, that is, the speed fluctuation generated in the intermediate transfer belt 10 when the sheet enters the transfer pressure contact portion is suppressed, High quality images can be obtained.

The following can be derived from the above-described contents and the above-described effects. That is, the sheet cutting device 401 as the first cutting unit is not limited to cutting the sheet S into the above-described shape, and the above-described transfer is performed from the viewpoint of achieving the above-described effect and functioning as the first cutting unit. It is only necessary that the contact area of the sheet S with the pressure contact portion can be cut into a shape that gradually decreases from the portion near the rear end of the leading end portion of the sheet S to the leading end.
Further, the sheet cutting device 402 as the second cutting unit has the above-described effects and functions as the second cutting unit, so that the leading end shape of the leading end of the sheet S is orthogonal to the sheet conveying direction X. It suffices if it can be cut.

For example, when the cutting shape of the leading edge of the paper S cut by the paper cutting device 401 as described above is not a problem for use by a user or the like, the paper cutting device is not limited to the above embodiment and the first and second modifications. It is also possible to make it unnecessary without installing 402.
Also, if you want to suppress the fluctuation when the sheet enters the image carrier or the intermediate transfer member and do not want to obtain a high-quality image so much, In a case where the highest priority is to obtain a high-quality image by suppressing the change in speed of the intermediate transfer belt 10 when the intermediate transfer belt 10 is inactivated, the sheet cutting devices 401 and 402 are operated properly. Is also possible.

In the above embodiment and the first and second modifications, the tandem type image forming apparatus that transfers the sheet to the intermediate transfer body and then transfers the sheet to the sheet-like recording medium has been described as an example. It goes without saying that the present invention can also be applied and implemented in a direct transfer type tandem color image forming apparatus that sequentially transfers and superimposes the toner. Needless to say, the present invention can be applied to a case where the image carrier is not limited to a tandem type image forming apparatus.
Although the present invention has been described with respect to specific embodiments and modifications, the technical scope disclosed by the present invention is not limited to those exemplified in the above-described embodiments and modifications. It will be apparent to those skilled in the art that various embodiments, modifications, and examples can be configured in accordance with the necessity and application within the scope of the present invention. .

1 is a front view of an entire tandem type indirect transfer / electrophotographic color copying machine showing a first embodiment of the present invention; FIG. 3 is a plan view for explaining a cutting shape of a leading end portion of a sheet cut by a sheet cutting device as a first cutting unit in the first embodiment. FIG. 6 is a plan view illustrating a cutting shape of a leading end portion of a sheet cut by a sheet cutting device as a second cutting unit in the first embodiment. FIG. 3 is a simplified plan view for explaining the configuration and operation of a sheet cutting device as a first cutting unit in the first embodiment. FIG. 5 is a simplified plan view for explaining the configuration and operation of a sheet cutting device as a second cutting unit in the first embodiment. It is a top view explaining the guide plate in the modification 1 of 1st Embodiment. It is a top view explaining the cutting shape of the front-end | tip part of the paper in the modification 2 of 1st Embodiment. FIG. 9 is a plan view for explaining a cutting shape of a leading end portion of a sheet according to a second modification different from the example illustrated in FIG. 7. 1 is a front view of a conventional tandem-type indirect transfer / electrophotographic color copying machine to which the present invention is applied. FIG. FIG. 10 is a plan view for explaining a problem when a sheet is conveyed and rushed into a transfer pressure contact portion in the conventional copying machine of FIG. FIG. 10 is a diagram showing an example of speed fluctuation at the time of entry of the transfer belt when a sheet is entered into the transfer pressure contact portion in the conventional copying machine of FIG. 9.

Explanation of symbols

10 Intermediate transfer belt (intermediate transfer member)
16 Support roller 18 Image forming means 22 Secondary transfer device (secondary transfer means)
24 Secondary transfer belt (secondary transfer means / secondary transfer member)
25 Fixing device (fixing means)
40, 40Y, 40C, 40M, 40K photoconductor (image carrier)
49 Registration roller pair (registration means)
56 Discharge roller pair (discharge means)
401 Paper cutting device (first cutting means)
402 Paper cutting device (second cutting means)
702, 802 Cutting tool 901 Guide plate (guide member / guide means)
S paper (sheet, sheet-like transfer medium, sheet-like recording medium)
Sa Paper leading edge, leading edge X Sheet transport direction Y Sheet width direction

Claims (7)

A single-leaf sheet on which a visible image formed on an image carrier is transferred to an intermediate transfer member by a primary transfer unit, and then the visible image transferred on the intermediate transfer member is conveyed through a conveyance path An image forming apparatus for transferring an image to a transfer medium at a transfer pressure contact portion by a secondary transfer means to form an image,
The contact area of the transfer medium with respect to the transfer pressure contact portion on the upstream side of the transfer pressure contact portion connected to the transfer pressure contact portion is gradually reduced from the portion near the rear end to the front end of the transfer medium. An image forming apparatus comprising a first cutting unit capable of cutting into a shape. In an image forming apparatus for transferring a visible image formed on an image carrier to a single-leaf sheet-like transfer medium conveyed via a conveyance path at a transfer pressure contact portion by a transfer unit, and forming an image.
The contact area of the transfer medium with respect to the transfer pressure contact portion on the upstream side of the transfer pressure contact portion connected to the transfer pressure contact portion is gradually reduced from the portion near the rear end to the front end of the transfer medium. An image forming apparatus comprising a first cutting unit capable of cutting into a shape.   The first cutting means is configured to cut at a fixed angle with respect to the transfer pressure contact portion from one side end to the other side end of the front end portion of the transfer medium. The image forming apparatus described.   The guide member that abuts on the other side end opposite to one side end of the transfer medium that first enters the transfer pressure contact portion is disposed so as to be orthogonal to the transfer pressure contact portion. Item 4. The image forming apparatus according to Item 3.   A first cutting means, with the center of the transfer medium at the front end of the transfer medium as a reference, protruding toward the downstream side of the transfer direction from the center of the transfer medium to both ends with respect to the transfer pressure contact part, or the transfer medium 3. The image forming apparatus according to claim 1, wherein a leading end portion of the transfer medium is cut so as to protrude toward the upstream side in the transport direction from both side ends to the center of the image forming apparatus. A fixing unit that fixes the image transferred at the transfer pressure contact portion, and a discharging unit that discharges the fixed transfer medium connected to the fixing unit via a conveyance path,
2. A second cutting unit capable of cutting the leading end portion of the transfer medium cut by the first cutting unit is disposed on the conveyance path between the discharge unit and the fixing unit. Or the image forming apparatus according to any one of 5 to 5;   The second cutting means is used to cut the front end of the transfer medium cut by the first cutting means so that the front end of the transfer medium is perpendicular to the transport direction of the transfer medium. The image forming apparatus according to claim 6.

Images