JP2013037360A - Image forming apparatus - Google Patents

Abstract

An image forming apparatus capable of realizing low cost is provided.
A transfer roller that transports a sheet, a transfer belt that carries an image to be transferred to the sheet and moves in one direction, a transfer counter roller that stretches the transfer belt, and a transfer belt on the transfer counter roller. The transfer roller 34 that rotates in contact with the transfer roller and the transfer belt stretched around the outer peripheral surface of the transfer counter roller at a position nearer to the direction opposite to the moving direction of the transfer belt than the contact portion of the transfer roller and transfer counter roller A guide 50 that forms a conveyance path for a sheet conveyed by the conveyance roller in a direction perpendicular to the belt, and a control unit that controls the conveyance roller so that the leading end of the sheet abuts the transfer belt substantially perpendicularly along the guide. An image forming apparatus.
[Selection] Figure 3

Description

  Embodiments described herein relate generally to an image forming apparatus.

  A sheet feeding device that conveys the sheets one by one, a registration roller that positions the leading edge by abutting the sheet P against the image forming unit, and a driving unit that rotates and stops the registration rollers There is known an image forming apparatus having However, a motor for driving the registration rollers and a clutch for intermittent operation are required for the driving mechanism, which causes a problem that the apparatus becomes expensive.

JP 2006-111423 A

  The problem to be solved by the embodiments of the present invention is to provide an image forming apparatus capable of realizing low cost.

  In order to solve the above problems, an image forming apparatus according to an embodiment of the present invention includes a conveyance roller that conveys a sheet, a transfer belt that carries an image to be transferred to the sheet, and moves in one direction, and the transfer belt. A transfer counter roller that stretches, a transfer roller that rotates while holding the transfer belt sandwiched between the transfer counter roller, and a contact portion between the transfer roller and the transfer counter roller that is opposite to the moving direction of the transfer belt. A guide that forms a transport path for paper transported by the transport roller in a direction perpendicular to the transfer belt stretched around the outer peripheral surface of the transfer counter roller at a position in the vicinity of the direction, along the guide; And a control unit that controls the conveyance roller so that the leading edge of the sheet abuts the transfer belt substantially vertically.

1 is a block diagram of an image forming apparatus according to a first embodiment. 1 is a configuration diagram of an image forming apparatus according to a first embodiment. FIG. 5 is an enlarged view of a secondary transfer position in the first embodiment. FIG. 6 is a perspective view of a secondary transfer position before sheet alignment in the first embodiment. FIG. 4 is a perspective view of a secondary transfer position during sheet alignment in the first embodiment. FIG. 6 is a perspective view of a secondary transfer position after sheet alignment in the first embodiment. It is an enlarged view of a secondary transfer position in the second embodiment. It is an enlarged view of a secondary transfer position in the third embodiment. 10 is a flowchart of paper conveyance in the fourth embodiment.

An image forming apparatus according to an embodiment will be described below with reference to the accompanying drawings.
(First embodiment)

  The image forming apparatus according to the first embodiment does not have a registration roller, and is in the vicinity of a contact portion upstream of a pair of rollers formed by a transfer roller and a transfer counter roller, and is stretched around the outer peripheral surface of the transfer counter roller. A guide that forms a conveyance path for conveying a sheet by a conveyance roller in a direction perpendicular to the transferred transfer belt is provided. In the following description, the transfer roller is described as a secondary transfer roller, and the transfer counter roller is described as a drive roller.

  FIG. 1 is a block diagram of the image forming apparatus 100. The image forming apparatus 100 includes a control unit 101, a scanner unit 104, a control panel unit 106, a printer unit 110, a communication control unit 113, and a thickness sensor 116. A specific hardware configuration of the image forming apparatus 100 will be described separately with reference to FIG.

  The control unit 101 controls the overall operation of the image forming apparatus 100. The control unit 101 includes a main CPU 102 that controls the image forming apparatus 100 and a storage unit 103. The storage unit 103 is, for example, a memory such as an HDD (Hard Disk Drive) that is a semiconductor storage device or a magnetic storage device. The storage unit 103 stores a program for operating the main CPU 102.

  The scanner unit 104 includes a scanner CPU 105 and a reading unit 112. The scanner CPU 105 controls the scanner unit 104. The reading unit 112 reads an image of a document.

  The control panel unit 106 includes a panel CPU 107, a display unit 108, and an operation unit 109. The panel CPU 107 controls the control panel unit 106. The display unit 108 displays the processing mode of the image forming apparatus 100. The processing mode is copying, scanning, FAX transmission, or the like. The control unit 101 displays various settings such as the number of printed sheets, the size of the paper P, and the type of the paper P on the display unit 108. The operation unit 109 can select a processing mode. The display unit may be a touch panel type or may serve as an operation unit. The operation unit 109 has various keys.

  The printer unit 110 includes a printer CPU 111 that controls the printer unit 110. The communication control unit 113 transmits and receives various types of information. The communication control unit 113 includes a communication control CPU 114 that controls the communication control unit 113 and a communication interface (I / F) 115. The communication control CPU 114 is connected to an external server or a client PC via the communication I / F 115 and receives print data and the like.

  The thickness sensor 116 detects the thickness of the paper P. The thickness sensor 116 is an ultrasonic sensor, for example.

  FIG. 2 is a configuration diagram illustrating the image forming apparatus according to the first embodiment. In FIG. 2, reference numeral 100 denotes an image forming apparatus, for example, an MFP (Multi-Function Peripherals), a printer, a copying machine, or the like, which is a multifunction peripheral. In the following description, an MFP will be described as an example.

  The MFP 100 includes an automatic document feeder (ADF) 12, a control panel unit 106, a scanner unit 104, a printer unit 110, a paper feed cassette (paper feed unit) 18, and a paper discharge unit 40.

  The ADF 12 is provided on the document table so as to be freely opened and closed, and automatically conveys the document to the scanner unit 104. The control panel unit 106 includes an operation unit 109 having various keys and a touch panel display unit 108.

  The scanner unit 104 is provided below the ADF 12 and reads a document conveyed by the ADF 12 or a document placed on a document table to generate image data. The scanner unit 104 is an example of a print document input unit. In addition to this, for example, a document created by a PC (external input unit) as an external terminal is received via the communication I / F 115 shown in FIG. It is also possible to print as

  The paper feed cassette 18 has a plurality of cassettes that accommodate paper P of various sizes. The paper discharge unit 40 accommodates the discharged paper P on which an image has been formed.

  The printer unit 110 includes an image forming unit and a laser exposure device, which will be described later. The printer unit 110 processes image data read by the scanner unit 104 and image data created by a PC and forms an image on the paper P supplied from the paper feed cassette 18. Form. The paper P on which an image is formed by the printer unit 110 is discharged to the paper discharge unit 40. The printer unit 110 is, for example, a color tandem color laser printer.

  The laser exposure device 19 includes a polygon mirror 19a, an imaging lens system 19b, and a mirror 19c. The laser exposure device 19 irradiates a photosensitive drum (described later) that rotates a laser beam emitted from a semiconductor laser element and that is modulated by image data. Scan in the direction.

  The printer unit 110 includes image forming units 20Y, 20M, 20C, and 20K for each color of yellow (Y), magenta (M), cyan (C), and black (K). The image forming units 20Y, 20M, 20C, and 20K are arranged on the lower side of the transfer belt 21 from the upstream side to the downstream side in the moving direction of the transfer belt 21.

  In the following description, since the image forming units 20Y, 20M, 20C, and 20K have the same configuration, the image forming unit 20Y will be described as a representative.

  The image forming unit 20Y includes a photosensitive drum as an image carrier, and a charging charger, a developing device, a primary transfer roller, and a cleaner are disposed around the photosensitive drum. A laser beam modulated with image data corresponding to yellow is irradiated from the laser exposure device 19 to the exposure position of the photosensitive drum, and an electrostatic latent image is formed on the photosensitive drum.

  The charging charger of the image forming unit 20Y uniformly charges the entire surface of the photosensitive drum. The surface of the charged photosensitive drum is irradiated with the laser beam described above to form an electrostatic latent image. The developing device supplies a two-component developer composed of yellow toner and a carrier to the photosensitive drum by a developing roller to which a developing bias is applied. The electrostatic latent image on the photosensitive drum is developed by the supplied developer and becomes a visible toner image. Through a transfer process described later, the cleaner removes residual toner on the surface of the photosensitive drum using a blade.

  A toner cartridge 2 that supplies toner to each developer of the image forming unit is provided above the image forming units 20Y, 20M, 20C, and 20K. The toner cartridge 2 is adjacent to toner cartridges 2Y, 2M, 2C, and 2K for each color of yellow (Y), magenta (M), cyan (C), and black (K). Of the toner cartridges of the respective colors, only the black (K) cartridge 2K has a large capacity. This is because black toner consumption is the largest in normal image formation.

  In FIG. 2, the endless transfer belt 21 moves cyclically, and for example, semiconductive polyimide is used from the viewpoint of heat resistance and wear resistance. The transfer belt 21 is stretched around the driving roller 31 and the driven rollers 32 and 33, and is in contact with the photosensitive drum. The transfer belt 21 is rotated in the direction of arrow t by driving of the driving roller 31. The drive roller 31 is driven by, for example, a motor. A primary transfer voltage is applied by a primary transfer roller to a position of the transfer belt 21 facing the photosensitive drum, and the toner image on the photosensitive drum is primarily transferred to the transfer belt 21. The intermediate transfer belt 21 carries the aforementioned color toner images (color images).

  A secondary transfer roller 34 is disposed facing the drive roller 31 that stretches the transfer belt 21. When the paper P passes between the transfer belt 21 and the secondary transfer roller 34, a secondary transfer voltage is applied to the paper P by the secondary transfer roller 34, and the toner image on the transfer belt 21 is secondarily transferred to the paper P. To do. The secondary transfer roller 34 is in contact with the driving roller 31 with the transfer belt 21 interposed therebetween. In the vicinity of the driven roller 33 of the transfer belt 21, a belt cleaner 35 for cleaning (residual toner) that has not been transferred to the paper P in the secondary transfer process is provided.

  In addition, a pickup roller 38, a separation roller 36, a thickness sensor 116, a conveyance roller pair 37, and a guide 50 are provided between the paper feed cassette 18 and the secondary transfer roller 34, and the secondary transfer roller 34 conveys the sheet. A fixing device 39 is provided downstream in the direction.

  The pickup roller 38 takes out the paper P in the paper feed cassette 18. The separation roller 36 separates the paper P fed from the pickup roller 38 one by one. The conveyance roller pair 37 conveys the paper P that has passed through the separation roller 36 to a secondary transfer position located downstream. The fixing device 39 fixes the toner image transferred onto the paper P onto the paper P by heat and pressure.

  The controller 101 shown in FIG. 2 drives the pickup roller 38, the separation roller 36, the transport roller 37, the driving roller 31, and the fixing device 39 by a motor.

  A paper discharge unit 40 and a reverse conveyance path 41 are provided downstream of the fixing device 39. The paper P on which the toner image is fixed by the fixing device 39 is discharged to the paper discharge unit 40. The reverse conveyance path 41 reverses the paper P and guides it in the direction of the secondary transfer roller 34, and is used when performing duplex printing.

  Hereinafter, alignment of the paper P supplied from the paper feed cassette 18 toward the transfer belt 21 (secondary transfer position) according to the present embodiment will be described. In the following description, “upstream” and “downstream” are relative positions along the sheet conveyance direction.

  FIG. 3 is an enlarged view of the secondary transfer region. In the secondary transfer area, a driving roller 31, a secondary transfer roller 34, and a guide 50 that stretch the transfer belt 21 are arranged. The guide 50 is located downstream of the conveying roller 37 and upstream of the contact position between the driving roller 31 and the secondary transfer roller 34. The contact position between the drive roller 31 and the secondary transfer roller 34 here is a contact position (secondary transfer position) between the transfer belt 21 and the secondary transfer roller 34 on which the drive roller 31 is stretched. The guide 50 is located on the drive roller 31 side of the paper P conveyance path. The downstream end of the guide 50 is preferably a position that does not contact the transfer belt 21 and is in the vicinity of the contact position between the drive roller 31 and the secondary transfer roller 34.

  The contact position of the drive roller 31 and the secondary transfer roller 34 is arranged at a position shifted from the vertical position from the contact position of the transport roller pair 37. As shown in FIG. 3, the drive rollers 31 and the secondary transfer roller 34 are arranged so that the contact position of the drive roller 31 and the secondary transfer roller 34 is shifted from the vertical position in the moving direction (arrow t) of the transfer belt 21. A transfer roller 34 is disposed.

  As described above, by arranging the driving roller 31, the secondary transfer roller 34, the conveying roller pair 37, and the guide 50, the sheet P conveyed by the conveying roller pair 37 is stretched around the outer peripheral surface of the driving roller 31. It proceeds substantially perpendicular to the transferred belt 21. The control unit 101 controls the transport roller 37 to transport the paper P so that the leading edge of the paper P comes into contact with the transfer belt 21 and the paper P is further bent. When the leading edge of the paper P contacts the transfer belt 21, even if the paper P is inclined in the front-rear direction of the paper surface, the leading edge of the paper P abuts the transfer belt 21, so that the leading edge of the paper P Regulated on the surface. The straight line (solid line) shown in FIG. 3 indicates the paper P that is in contact with the transfer belt 21 stretched around the outer peripheral surface of the drive roller 31 substantially perpendicularly.

  On the other hand, since the transfer belt 21 is conveyed in the direction of the arrow t, the paper P pressed against the surface of the transfer belt 21 by the conveyance roller 37 is the drive roller 31 and the secondary transfer roller as shown by the broken line shape in FIG. It advances to the contact position of 34. That is, the leading edge of the paper P advances to the contact position of the drive roller 31 and the secondary transfer roller 34 with the rotation of the transfer belt 21 conveyed in the arrow t direction. At this time, the front end of the paper P is abutted against the surface of the transfer belt 21 so that the paper P with the front end positioned is in contact with the drive roller 31 and the secondary transfer roller 34 while maintaining the aligned state. Transported to position. Then, the sheet is conveyed downstream while being in contact with the transfer belt 101 by the contact position of the driving roller 31 and the secondary transfer roller 34.

  Further, since the sheet P conveyed by the conveying roller 37 is conveyed along the guide 50, the sheet P travels substantially perpendicular to the transfer belt 21 stretched around the outer peripheral surface of the driving roller 31. Therefore, the sheet P can be conveyed to the contact position between the driving roller 31 and the secondary transfer roller 34 without having a registration roller for aligning the paper P.

  By arranging the guide 50 along the paper transport path as described above, the paper P is prevented from being bent toward the image forming unit 20K shown in FIG. In addition, jamming of the paper P can be reduced.

  The tilt alignment correction of the paper P will be described with reference to FIGS. 4 to 6 show the pressing portion of the sheet P against the transfer belt 21 as seen from the lower surface so that the alignment mechanism is clear. FIG. 4 is a perspective view of the secondary transfer position before paper alignment, FIG. 5 is a perspective view of the secondary transfer position during paper alignment, and FIG. It is a figure which shows the perspective view of the secondary transfer position after position.

  As shown in FIG. 4, the sheet P conveyed in an inclined manner is abutted almost vertically against the transfer belt 21 stretched on the outer peripheral surface of the driving roller 31 by the conveying roller 37 as shown in FIG. 5. . Accordingly, the position of the leading edge of the paper P is regulated on the surface of the transfer belt 21. Further, as shown in FIG. 6, the leading edge of the sheet P advances to the contact position between the driving roller 31 and the secondary transfer roller 34 along the arrow t which is the conveying direction of the transfer belt 21, and the leading edge of the sheet P is aligned. In this state, the sheet is conveyed downstream of the contact position between the drive roller 31 and the secondary transfer roller 34. That is, the sheet P is transported to the contact position (secondary transfer position) between the drive roller 31 and the secondary transfer roller 34 in a state where the sheet P is aligned, and the secondary transfer process is executed here.

With the image forming apparatus 100 according to the present embodiment, it is possible to eliminate the need for paper alignment by registration rollers, and it is possible to greatly simplify the paper transport mechanism to the secondary transfer position, thereby realizing cost reduction. can do. Further, the size of the image forming apparatus 100 can be reduced by greatly simplifying the paper transport mechanism up to the secondary transfer position. Further, since the elements for transporting the paper P are simplified, the occurrence of jamming of the paper P can be reduced. Further, since the drive motor for the registration roller is reduced, it is possible to contribute to power saving of the image forming apparatus 100.
(Second embodiment)

  The image forming apparatus of the second embodiment does not have a registration roller, and includes guides for guiding a sheet upstream of a pair of rollers formed by a driving roller and a secondary transfer roller. The same components as those in the first embodiment are denoted by the same reference numerals.

  FIG. 7 is an enlarged view of the secondary transfer position. At the secondary transfer position, a driving roller 31, a secondary transfer roller 34, a first guide 60, and a second guide 70 that stretch the transfer belt 21 are disposed. The first guide 60 and the second guide 70 are located downstream of the conveying roller pair 37 and upstream of the contact position between the driving roller 31 and the secondary transfer roller 34. That is, it is located along the paper conveyance path between the conveyance roller pair 37 and the position where the paper P abuts against the driving roller 31. The first guide 60 is located on the drive roller 31 side of the paper P conveyance path. The second guide 70 is positioned on the secondary transfer roller 34 side of the paper P conveyance path. The downstream ends of the first guide 60 and the second guide 70 are preferably not in contact with the transfer belt 21 and in the vicinity of the contact position between the drive roller 31 and the secondary transfer roller 34. The first and second guides 60 and 70 are located across the paper conveyance path, but the width of the first and second guides 60 and 70 is such that the paper P moves between the driving roller 31 and the secondary transfer roller 34 as the transfer belt 21 moves. The width is set such that the sheet P does not contact the second guide even if it moves in the contact position direction.

  As described above, by arranging the driving roller 31, the secondary transfer roller 34, the conveyance roller 37, the first guide 60, and the second guide 70, the control unit 101 can convey the sheet conveyed by the conveyance roller 37. P is advanced substantially perpendicularly to the transfer belt 21 stretched around the outer peripheral surface of the drive roller 31. The control unit 101 controls the transport roller 37 to transport the paper P so that the leading edge of the paper P comes into contact with the transfer belt 21 and the paper P is further bent. When the leading edge of the paper P contacts the transfer belt 21, the leading edge of the paper P is pressed against the transfer belt 21 even if the paper P is inclined in the front-rear direction of the paper surface. Regulated by

  On the other hand, since the transfer belt 21 is conveyed in the direction of the arrow t, the sheet P pressed against the surface of the transfer belt 21 by the conveyance roller 37 is the drive roller 31 and the secondary transfer roller as shown by the broken line shape in FIG. It advances to the contact position of 34. That is, the leading edge of the paper P advances to the contact position of the drive roller 31 and the secondary transfer roller 34 with the rotation of the transfer belt 21 conveyed in the arrow t direction. At this time, the front end of the paper P is pressed against the surface of the transfer belt 21, so that the paper P whose tip position is aligned maintains the aligned state, and the contact position between the driving roller 31 and the secondary transfer roller 34. It is conveyed to. Then, at the contact position (secondary transfer position) between the driving roller 31 and the secondary transfer roller 34, it is conveyed downstream while being in contact with the transfer belt 101. That is, in this state, the above-described secondary transfer process is executed.

  Further, since the paper P transported by the transport roller 37 is transported along the first guide 60 and the second guide 70, the paper P is almost the same as the transfer belt 21 stretched around the outer peripheral surface of the drive roller 31. Progress vertically. Therefore, the sheet P can be transported to the contact position between the driving roller 31 and the secondary transfer roller 34 without being provided with a registration roller for aligning the sheet P. By guiding the paper P on both sides of the transport path of the paper P by the first guide 60 and the second guide 70, the paper is more perpendicular to the transfer belt 21 stretched on the outer peripheral surface of the driving roller 31. P can be pressed.

  As described above, the first guide 60 and the second guide 70 are arranged along the paper conveyance path at a predetermined interval, so that the paper P is transferred to the image forming unit 20K side shown in FIG. Deflection to the roller 34 side is suppressed, and not only the alignment of the paper P but also the occurrence of jamming of the paper P can be further reduced than in the first embodiment.

With the image forming apparatus 100 according to the second embodiment described above, it is possible to eliminate the need for paper alignment by registration rollers, and it is possible to greatly simplify the paper transport mechanism up to the secondary transfer position. Cost reduction can be realized. Further, the size of the image forming apparatus 100 can be reduced by greatly simplifying the paper transport mechanism up to the secondary transfer position. Since the elements for transporting the paper P are simplified, the occurrence of jamming of the paper P can be further reduced. Further, since the drive motor for the registration roller is reduced, it is possible to contribute to power saving of the image forming apparatus 100.
(Third embodiment)

  The image forming apparatus according to the third embodiment does not have a registration roller, and includes a guide for guiding a sheet upstream of a pair of rollers formed by a driving roller and a secondary transfer roller. Also serves as a guide. The same components as those in the first embodiment are denoted by the same reference numerals.

  FIG. 8 is an enlarged view of the secondary transfer position. At the secondary transfer position, a driving roller 31, a secondary transfer roller 80, and a guide 50 that stretch the transfer belt 21 are disposed.

  The secondary transfer roller 80 also serves as a guide located on the secondary transfer roller 80 side with a position where the paper P abuts against the transfer belt 21. For example, as shown in FIG. 8, the diameter of the secondary transfer roller 80 is made larger than the diameter of the drive roller 31. For example, the diameter of the secondary transfer roller 80 is 28 mm, and the diameter of the drive roller 31 is 18 mm. However, the diameter of the secondary transfer roller 80 may not be larger than the diameter of the driving roller 31 as long as the diameter also serves as a guide for the paper P. For example, the diameter of the secondary transfer roller 80 and the diameter of the drive roller 31 may be the same as long as the diameter of the sheet P also serves as a guide for the paper P. The diameter may be large.

  As described above, the secondary transfer roller 80 also serves as a guide for the paper P, so that not only the alignment of the paper P but also the jam of the paper P can be reduced.

With the image forming apparatus 100 according to the third embodiment described above, it is possible to eliminate the need for paper alignment by registration rollers, and the paper transport mechanism up to the secondary transfer position can be greatly simplified. Cost reduction can be realized. Further, the size of the image forming apparatus 100 can be reduced by greatly simplifying the paper transport mechanism up to the secondary transfer position. Since the elements for transporting the paper P are simplified, the occurrence of jamming of the paper P can be further reduced. Further, since the drive motor for the registration roller is reduced, it is possible to contribute to power saving of the image forming apparatus 100.
(Fourth embodiment)

  The image forming apparatus according to the fourth embodiment does not have a registration roller and includes a guide for guiding a sheet upstream of a roller pair formed by a driving roller and a secondary transfer roller. Furthermore, when the paper is thin, the drive roller is stopped until the paper abuts on the transfer belt stretched around the outer peripheral surface of the drive roller, and the paper leading edge is aligned by bringing the paper into contact with the transfer belt. Then, control is performed to rotate the drive roller. However, the control for stopping the driving roller is performed after the primary transfer of the toner image is completed. The same components as those in the first embodiment are denoted by the same reference numerals.

  Thin paper is less stiff and flexible than plain paper. Therefore, if the paper P is thin and the transport amount after reaching the transfer belt 21 stretched around the outer peripheral surface of the driving roller 31 is small, the leading edge of the paper P may not be sufficiently aligned. Therefore, the control unit 101 stops the driving roller 31 until the paper P comes into contact with the transfer belt 21 stretched around the outer peripheral surface of the driving roller 31, and makes the paper P come into contact with the transfer belt 21. After the tip of the head is aligned, the drive roller 31 is controlled to rotate.

  FIG. 9 is a flowchart of paper conveyance. In 200, the control unit 101 determines whether or not the paper P is a thin paper. For example, the thickness of the paper P is detected by the thickness sensor 116 (see FIG. 2), for example. The detection result detected by the thickness sensor 116 is sent to the control unit 101, and the control unit 101 determines whether the thickness of the paper P is thinner than a threshold value. The threshold value of the thickness of the paper P determined to be thin paper is, for example, 0.04 mm. The threshold value can be arbitrarily changed.

  The determination of whether the paper P is thin is not limited to the detection result of the thickness sensor 116. For example, the user can select the paper type on the operation unit 109, and the control unit 101 may determine whether or not the user has selected thin paper.

  When the control unit determines that the paper P is not a thin paper but a plain paper or a thick paper (No in 200), in 203, the driving roller 31 is rotated to complete the image formation. The thickness of plain paper is 0.1 mm, for example, and the thickness of cardboard is 0.2 mm.

  When the control unit determines that the paper P is not plain paper or thick paper but thin paper (200: Yes), the rotation of the driving roller 31 is stopped in 201. Thereafter, in 202, the control unit 101 determines whether or not the paper P has reached the transfer belt 21 stretched around the outer peripheral surface of the drive roller 31. For example, the control unit 101 counts the elapsed time after the paper P is fed from the paper feed cassette 18 by the pickup roller 38 and the elapsed time after the paper P passes through the thickness sensor 116, and the predetermined elapsed time. It is determined whether or not the transfer belt 21 stretched on the outer peripheral surface of the drive roller 31 has been reached. If the control unit 101 determines that the predetermined time has not elapsed (No in 202), the determination of 202 is repeated until it is determined that the predetermined time has elapsed.

  If the control unit 101 determines that the predetermined time has elapsed (Yes in 202), the control unit 101 rotates the drive roller in 203 and ends the image formation.

  Further, the fourth embodiment may be combined with the second and third embodiments.

  With the image forming apparatus 100 according to the fourth embodiment described above, it is possible to eliminate the need for paper alignment by registration rollers, and the paper transport mechanism up to the secondary transfer position can be greatly simplified. Cost reduction can be realized. Further, the size of the image forming apparatus 100 can be reduced by greatly simplifying the paper transport mechanism up to the secondary transfer position. Since the elements for transporting the paper P are simplified, the occurrence of jamming of the paper P can be further reduced. Further, since the drive motor for the registration roller is reduced, it is possible to contribute to power saving of the image forming apparatus 100. Furthermore, even if the paper P is a thin paper, the registration roller is unnecessary and the paper P can be aligned.

  In the above description, the secondary transfer counter roller is described as a driving roller, but the present invention is not limited to this. For example, one of the driven rollers 32 and 33 may be a driving roller, and the secondary transfer counter roller may be a driven roller.

  According to the image forming apparatus of at least one embodiment described above, it is possible to eliminate the paper alignment by the registration roller, and the paper transport mechanism to the secondary transfer position can be greatly simplified. Cost reduction can be realized.

  Although several embodiments have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the gist of the invention, and in the invention described in the claims and the equivalents thereof.

2 toner cartridge 21 transfer belt 31 driving rollers 32, 33 driven rollers 34, 80 secondary transfer roller 35 belt crewer 37 transport roller 39 fixing device 50, 60, 70 guide 100 image forming apparatus 101 control unit 102 main CPU
103 Storage Unit 104 Scanner Unit 105 Scanner CPU
106 Control Panel 107 Panel CPU
108 Display Unit 109 Operation Unit 110 Printer Unit 111 Printer CPU
112a, 112b Reading unit 113 Communication control unit 114 Communication control CPU
115 Communication I / F
116 Thickness sensor

Claims (5)

A transport roller for transporting paper;
A transfer belt carrying an image to be transferred to the paper and moving in one direction;
A transfer counter roller that stretches the transfer belt;
A transfer roller rotating in contact with the transfer belt sandwiched between the transfer counter roller,
In a position perpendicular to the transfer belt stretched on the outer peripheral surface of the transfer counter roller at a position near the transfer roller and the transfer counter roller in the direction opposite to the moving direction of the transfer belt. , A guide that forms a conveyance path for paper conveyed by the conveyance roller;
A control unit that controls the conveyance roller so that the leading edge of the paper abuts the transfer belt substantially vertically along the guide;
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the guide is positioned on a side of the transfer counter roller opposite to a moving direction of the transfer belt from a position where the sheet hits the transfer belt.   The image forming apparatus according to claim 1, wherein the guide is positioned on the transfer counter roller side and the transfer roller side across a position where the sheet hits the transfer belt.   4. The image forming apparatus according to claim 2, wherein the transfer roller also serves as the guide located on the transfer roller side across a position where the sheet abuts against the transfer belt.   When the control unit determines that the sheet is a thin sheet, the control unit stops the transfer counter roller until the sheet comes into contact with the transfer belt stretched on the outer peripheral surface of the transfer counter roller. 5. The image forming apparatus according to claim 1, wherein after the alignment, the transfer counter roller is controlled to rotate. 6.

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