JP2010001098A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct a curl of inverted paper carried from a paper feeding portion before image formation. <P>SOLUTION: The image forming device includes a paper feeding cassette 4 feeding paper; an image forming portion 40 forming an image on the paper carried from the paper feeding cassette 4 on the basis of image data; a detecting portion 80 detecting an image on the back surface of the paper carried from the paper feeding cassette 4; a curl correcting portion 90 correcting a curl of the paper carried in a carrying path between the image forming portion 40 and the paper feeding cassette 4; and a control portion determining whether the carried paper is inverted paper or not according to a detection result by the detecting portion 80, and making the curl correcting portion 90 correct the curl of the inverted paper 90 when the paper is the inverted paper. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus.

  Conventionally, an image forming apparatus such as an electrophotographic copying machine is known. In this image forming apparatus, since fixing is performed by heating and pressing after the toner image is formed on the paper, a phenomenon that the paper after fixing is curled is known.

  For this reason, an image forming apparatus having a paper curl correction function has been considered. For example, an image amount to be formed on a sheet is acquired from image information input for image formation, a curl correction direction is determined according to the image amount, and a sheet after fixing processing is determined by two curl correction units. An image forming apparatus that performs curl correction in the curled correction direction and discharges the paper to a post-processing apparatus is considered (for example, see Patent Document 1). This is because, even if fixing is performed by the same fixing device, the direction of curl changes depending on the amount of image on the paper. The curl correction device is composed of a pair of rollers having different radii, and the sheet passes through the nip portion of the pair of rollers, so that the sheet is curled in the direction of the roller having a small radius to correct the sheet.

Further, an image forming apparatus that detects the length of the sheet in the conveyance direction after the fixing process with an optical sensor, corrects the curl of the sheet after the fixing process with a curl correction roller according to the detected length, and discharges the sheet. It is considered (for example, refer to Patent Document 2).
JP 2000-229758 A JP 2002-326754 A

  In recent years, in an image forming apparatus, in order to make effective use of resources in consideration of environmental problems, an opportunity to form an image on a white paper surface (front surface) of paper (back paper) that has been formed and discharged on one side has increased. ing. Unlike the opened paper, the backing paper is printed once, so curl wrinkles at the time of fixing often remain on the paper. When such a backing paper is set in a paper feed cassette or a manual feed tray and transported from the paper feed cassette or the manual feed tray to the image forming unit, the paper is caught by the guide or roller shaft of the transport path due to the curl and the paper is transported. There was a possibility of causing a defect (jam: JAM).

  Further, since the leading edge of the curled paper does not enter the registration roller, the function of the registration roller is impaired, and there is a possibility that the skew correction in the paper feeding / conveyance is not sufficiently performed. Furthermore, there is a possibility that print misalignment may occur due to a shift in timing of transferring the toner image in the image forming unit.

  However, in the conventional image forming apparatus having the curl correction function, since the curl correction apparatus is provided downstream of the fixing unit, it is possible to improve the stacking of the paper (printed matter) after being discharged, but the back paper is an image. The curl correction could not be performed before being conveyed to the forming unit.

  For this reason, there is a possibility that the productivity and quality of the printed matter may be deteriorated due to a jam or the like caused by the curling of the backing paper. In order to solve this, there is a method in which the user corrects the curling of the back paper by hand when setting the back paper in the paper feed cassette or the manual feed tray, but the work burden on the user is large.

  An object of the present invention is to perform curl correction on a backing paper conveyed from a paper feeding unit before image formation.

In order to solve the above-described problem, an image forming apparatus according to a first aspect of the present invention provides:
A paper supply unit for supplying paper;
An image forming unit that forms an image on a sheet conveyed from the sheet feeding unit based on image data;
A detection unit for detecting an image on the back side of the sheet being conveyed from the sheet feeding unit;
A curl correction unit that corrects curl of a sheet conveyed along a conveyance path between the image forming unit and the sheet feeding unit;
A control unit that determines whether or not the paper being conveyed is a back paper according to a detection result by the detection unit, and when the paper is a back paper, a control unit that causes the curl correction unit to curl the back paper; .

According to a second aspect of the present invention, there is provided an image forming apparatus.
A paper supply unit for supplying paper;
An image forming unit that forms an image on a sheet conveyed from the sheet feeding unit based on image data;
A curl correction unit that corrects curl of a sheet conveyed along a conveyance path between the image forming unit and the sheet feeding unit;
An operation unit for accepting an operation input of setting information indicating that a backing paper is set as paper in the paper feeding unit;
In accordance with the setting information input to the operation unit, it is determined whether or not the sheet conveyed from the sheet feeding unit is a backing paper. If the sheet is a backing sheet, the sheet is conveyed from the sheet feeding unit. A control unit that causes the curl correction unit to correct the curling of the backing paper.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect,
A registration roller for conveying the paper to the image forming unit;
The curl correcting unit corrects curl of a sheet conveyed along a conveyance path between the registration roller and the sheet feeding unit.

According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects,
The curl correction unit includes a first roller and a second roller, and the state where the first roller and the second roller are in pressure contact with each other, and the first roller and the second roller are The separated state can be switched.

  According to the first aspect of the present invention, it is possible to determine whether or not the conveyed paper is the back paper according to the image on the back side of the paper detected by the detection unit, and the conveyance from the paper supply unit. The curled paper can be curled before image formation.

  According to the second aspect of the present invention, it is determined whether or not the paper to be conveyed is the back paper according to the setting information indicating that the back paper is set in the paper feed unit input to the operation unit. And the curl correction can be performed on the backing paper conveyed from the paper supply unit before image formation.

  According to the third aspect of the present invention, it is possible to prevent misalignment of prints and jams in the image forming unit based on misalignment of skew correction in the registration roller and sheet misalignment of the registration roller.

  According to the invention described in claim 4, the configuration of the curl correction unit can be simplified, the state where the first roller and the second roller are pressed against each other when curl correction is performed, and the case where the curl correction is not performed are spaced apart from each other. The state can be switched freely.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Preferred first and second embodiments of the invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to the illustrated example. The embodiment of the present invention represents the most preferable embodiment of the invention, and the use and terms of the invention are not limited to this.

(First embodiment)
A first embodiment according to the present invention will be described with reference to FIGS. First, the apparatus configuration of the present embodiment will be described with reference to FIG. FIG. 1 shows a schematic configuration of an image forming apparatus 1 according to the present embodiment.

  The image forming apparatus 1 detects an image on the back side of the paper being transported to form an image, and performs curl correction to form an image when the paper is the back paper according to the detection result. This is an image forming apparatus that forms an image without performing curl correction when is not a back paper. This is because the backing paper is more likely to have curls than the opened paper (new paper). The image forming apparatus 1 is a color page printer, particularly a tandem type color page printer.

  As shown in FIG. 1, the image forming apparatus 1 includes a housing 2, a paper discharge tray 3, a paper feed cassette 4 as a paper feed unit, a manual feed tray 5 as a paper feed unit, an image forming unit 40, and a transport unit 60. , A detection unit 80, a curl correction unit 90, and the like. The image forming unit 40 includes an image forming main body 40a and a fixing unit 40b.

  The transport unit 60 includes a paper feed roller 61, transport rollers 62A, 62B, 63A, 63B, registration rollers 65A, 65B, a pressure roller 66, and transport rollers 67A, 67B. These rollers are in this order in the paper feed cassette. 4 to the paper discharge tray 3 are provided on a paper conveyance path 60a. Further, the transport unit 60 includes transport rollers 68A, 68B, 69A, 69B, 70A, and 70B, and these rollers are provided on the reversing path 60b in this order. Further, the transport unit 60 includes paper feed rollers 64A and 64B.

  The conveyance rollers 62A and 62B are a pair of rollers that are pressed against each other and have a nip portion, and are rotated so that the sheet passes through the nip portion. Conveying rollers 63A and 63B, registration rollers 65A and 65B, conveying rollers 63A and 63B, conveying rollers 67A and 67B, conveying rollers 68A and 68B, conveying rollers 69A and 69B, conveying rollers 70A and 70B, The paper rollers 64A and 64B have the same configuration as the transport rollers 62A and 62B, respectively.

  The paper feed cassette 4 stores paper P and supplies the paper P. The paper P is an open paper or a backing paper on which an image is formed (printed) on one side. When the paper P is a back paper, the paper P is set in the paper feed cassette 4 so that the white paper surface of the back paper faces up. This is because an image is formed on the white side of the backing paper. The paper P set in the paper feed cassette 4 is taken out from the uppermost portion one by one by the rotational drive of the paper feed roller 61 and is transported to the transport rollers 62A and 62B. The sheet P is conveyed to the registration rollers 65A and 65B via the conveyance rollers 63A and 63B. Similarly, the paper P is set on the manual feed tray 5, and the paper P is taken out from the top one by one by the rotational driving of the paper feed rollers 64A and 64B and conveyed to the registration rollers 65A and 65B. The registration rollers 65A and 65B are rotationally driven to transport the paper P transported from the transport rollers 63A and 63B to the image forming main body 40a, adjust the transport timing, and perform skew correction of the paper P.

  The image forming main body 40a includes a yellow image forming unit 40Y, a magenta image forming unit 40M, a cyan image forming unit 40C, a black image forming unit 40K, an intermediate transfer belt 47, a secondary transfer driving roller 48, a driven roller 49, and a cleaning unit 50. Have The fixing unit 40 b includes a fixing roller 51 and a pressure roller 52.

  The yellow image forming unit 40Y includes a photosensitive drum 41, a charging unit 42, an exposure unit 43, a developing unit 44, a primary transfer roller 45, and a cleaning unit 46 which are sequentially arranged around the photosensitive drum 41. ) Is formed on the intermediate transfer belt 47.

  Specifically, in the yellow image forming unit 40Y, the photosensitive drum 41 charged by the charging unit 42 is irradiated with light according to yellow image data from the exposure unit 43, and an electrostatic latent image is formed. . Then, the developing unit 44 attaches a charged yellow toner to the surface of the photosensitive drum 41 on which the electrostatic latent image is formed, and the electrostatic latent image is developed to form a toner image. The photosensitive drum 41 and the primary transfer roller 45 are rotated, and the yellow toner image formed on the photosensitive drum 41 is primarily transferred onto the intermediate transfer belt 47 to the transfer position where the primary transfer roller 45 is disposed. After the yellow toner image is primarily transferred to the intermediate transfer belt 47, the cleaning unit 46 removes residual charges, residual toner, and the like on the surface of the photosensitive drum 41.

  The magenta image forming unit 40M has an apparatus configuration similar to that of the yellow image forming unit 40Y, and forms a magenta (M) image on the intermediate transfer belt 47. Similarly, the cyan image forming unit 40 </ b> C forms a cyan (C) image on the intermediate transfer belt 47. Similarly, the black image forming unit 40 </ b> K forms a black (K) image on the intermediate transfer belt 47.

  The intermediate transfer belt 47 is an endless belt. The secondary transfer driving roller 48 is disposed on the conveyance path 60a side in the housing 2 and is driven to rotate. The driven roller 49 is disposed at a horizontal position with the secondary transfer driving roller 48. The primary transfer rollers 45 of each color of YMCK are sequentially arranged between the driven roller 49 and the secondary transfer drive roller 48. The intermediate transfer belt 47 is hung on the secondary transfer drive roller 48, the primary transfer roller 45, and the driven roller 49, and rotates around by the rotational drive of the secondary transfer drive roller 48. The driven roller 49 and the primary transfer roller 45 rotate according to the circumferential movement of the intermediate transfer belt 47.

  The pressure roller 66 is pressed against the secondary transfer driving roller 48 via the intermediate transfer belt 47. The sheet P conveyed from the registration rollers 65A and 65B passes between the secondary transfer driving roller 48 and the pressure roller 66 and is formed on the intermediate transfer belt 47 formed by the image forming units 40Y, 40M, 40C, and 40K. The toner image is secondarily transferred and conveyed to the fixing unit 40b. The cleaning unit 50 removes residual toner and the like on the intermediate transfer belt 47.

  The fixing roller 51 is rotatable and has a heat source to heat the paper P. The pressure roller 52 is pressed against the fixing roller 51 to form a nip portion. The fixing unit 40b fixes the toner image secondarily transferred to the paper P by heating and pressurizing when the conveyed paper P passes through the nip portion, and transports the toner image to the transport rollers 67A and 67B.

  The transport rollers 67A and 67B discharge the paper P transported from the fixing unit 40b to the paper discharge tray 3 by the rotational drive of the transport roller 67B. In the double-sided image formation, after the first surface of the paper P is formed, the transport rollers 67A and 67B discharge the paper P halfway to the paper discharge tray 3 side by the rotational driving of the transport roller 67B. The paper P is transported to the transport rollers 68A and 68B in the reverse path 60b by the reverse rotation of the transport roller 67B. The transported paper P is reversed and is transported in turn by transport rollers 68A and 68B and transport rollers 69A, 69B, 70A and 70B in the reverse path 60b, and transported to the registration rollers 65A and 65B in the transport path 60a. Is done. Then, the image forming unit 40 forms an image on the second surface (blank surface) of the sheet P.

  The detection unit 80 is a detection unit such as a line sensor provided between the conveyance rollers 62A and 62B and the conveyance rollers 63A and 63B on the conveyance path 60a, and an image on the back surface of the image forming surface of the conveyed paper P. Is detected.

  The curl correction unit 90 is provided at a position between the detection unit 80 and the transport rollers 63A and 63B on the transport path 60a, and corrects the curl of the paper P transported at the position. The curl correcting unit 90 performs curl correction when the paper P is a back paper, and does not perform curl correction when the paper P is not a back paper (opened paper).

  The position where the curl correction unit 90 is provided is not limited to the example of FIG. 1, and the position between the paper supply unit (the paper supply cassette 4 or the manual feed tray 5) and the image forming unit 40 in the transport path 60 a. The position may be any position (position upstream of the paper feed unit and downstream of the image forming unit 40 in the transport direction of the transport path 60a), and a position between the paper feed unit and the registration rollers 65A and 65B is more preferable. This is because when the paper P is curled, there is a possibility that the skew of the skew correction of the registration rollers 65A and 65B, the print misalignment of the image forming unit 40 based on the paper misalignment of the registration rollers 65A and 65B, and jamming may occur. It is.

  Next, the curl correction unit 90 will be described in detail with reference to FIGS. FIG. 2 shows a configuration of the curl correction unit 90 in a normal state. FIG. 3 shows a configuration of the curl correction unit 90 at the time of curl correction.

  As shown in FIG. 2, the curl correction unit 90 includes a rubber roller 91 as a first roller, a metal roller 92 as a second roller, a curl correction cam 93, and a spring portion 94. The rubber roller 91 has a rubber part 91a and a shaft part 91b. The rubber part 91a is made of rubber and can be deformed, and is provided around the shaft part 91b. The rubber part 91a may be configured by an elastic body other than rubber. The shaft portion 91b is a shaft of the rubber roller 91 and has a portion exposed at an end portion in the axial direction.

  The metal roller 92 is a roller provided at a position separated from the rubber roller 91 in a normal state, and can be moved in the direction of the rubber roller 91 by the rotation of the curl correction cam 93. The metal portion 92a is made of metal and does not deform, and is provided around the shaft portion 92b. The metal material of the metal part 92a is steel such as SUM (sulfur free-cutting steel) and SUS (stainless steel). The metal portion 92a may be made of a resin such as POM (polyacetal) other than metal. The shaft portion 92 b is a shaft of the metal roller 92.

  The curl correcting cam 93 is a mechanical element that is driven to rotate and has a curve in which the distance from the rotating shaft to the spring portion 94 changes according to the rotation angle. The spring portion 94 is pressed between the shaft portion 92 b of the metal roller 92 and the curl correction cam 93, and transmits the pressure applied by the rotation of the curl correction cam 93 to the metal roller 92.

  Normally, the curl correction cam 93 is rotationally driven so as to minimize the distance to the spring portion 94, the pressure applied to the metal roller 92 (shaft portion 92b) is lowered, and the rubber roller 91 and the metal roller 92 are separated from each other. The For this reason, the conveyed paper P passes through the space between the rubber roller 91 and the metal roller 92 and is not subjected to curl correction.

  As shown in FIG. 3, at the time of curl correction, the curl correction cam 93 is rotationally driven to maximize the distance to the spring portion 94, the pressure applied to the metal roller 92 is increased, and the metal roller 92 is applied to the rubber roller 91. Pressed. Then, a concave nip portion N is formed between the rubber roller 91 and the metal roller 92. For this reason, the conveyed paper P passes through the nip N between the rubber roller 91 and the metal roller 92 and is subjected to curl correction.

  Next, the detection unit 80 will be described in detail. FIG. 4 shows the configuration of the detection unit 80.

  As shown in FIG. 4, the detection unit 80 is a line sensor having a plurality of pairs of light emitting elements 81 and light receiving elements 82. The light emitting element 81 irradiates the conveyed paper P with light. The light receiving element 82 converts the reflected light emitted from the light emitting element 81 and reflected by the paper P into an electric signal indicating an image of the paper P, and outputs it to the control unit 11 described later.

  Next, the circuit configuration of the image forming apparatus 1 will be described. FIG. 5 shows a circuit configuration of the image forming apparatus 1.

  As shown in FIG. 5, the image forming apparatus 1 includes a control unit 11, an operation unit 20, a display unit 30, an image memory 12, a ROM (Read Only Memory) 13, a communication unit 14, an image forming unit 40, a transport unit 60, The detection unit 80, the curl correction unit 90, and the like are connected to each other via the bus 15.

  The control unit 11 centrally controls each unit of the image forming apparatus 1. The control unit 11 includes a CPU (Central Processing Unit) and a RAM (Random Access Memory). In the control unit 11, the CPU expands various programs stored in the ROM 13 in the RAM, and the CPU executes various processes using the programs expanded in the RAM.

  During normal image formation, the control unit 11 receives image data input from an external device (not shown) via the communication unit 14 and feeds the paper from the paper cassette 4 to the transport unit 60 for transport. Based on the received image data, the image forming unit 40 forms an image on a sheet. In addition, the control unit 11 executes a first curl correction process to be described later using a first curl correction program stored in the ROM 13.

  The operation unit 20 includes a key operation unit having various keys, receives various operation inputs from the user to the key operation unit, and outputs an operation signal of the operation input to the control unit 11. The display unit 30 includes a display panel such as an LCD (Liquid Crystal Display), and performs various displays according to display signals input from the control unit 11.

  The image memory 12 is a storage unit that temporarily stores information such as image data received from an external device. The ROM 13 is a storage unit dedicated to reading information. The ROM 13 stores various programs such as a first curl correction program and various data.

  The communication unit 14 is connected to an external device (not shown) such as a PC (Personal Computer) via a communication line such as a LAN (Local Area Network). Communicate.

  As described with reference to FIG. 1, the image forming unit 40 includes the image forming main body 40 a and the fixing unit 40 b, and forms an image on the paper conveyed by the conveying unit 60 (toner on the paper) according to an instruction from the control unit 11. Image transfer and fixing). As described with reference to FIG. 1, the transport unit 60 includes various rollers such as a paper feed roller 61, and feeds paper from the paper feed cassette 4 or the manual feed tray 5 in accordance with instructions from the control unit 11. The paper is transported on the path 60 a and the reverse path 60 b and discharged to the paper discharge tray 3.

  As described with reference to FIG. 1, the detection unit 80 includes the light emitting element 81 and the light receiving element 82, detects an image on the back side of the sheet conveyed by the conveyance unit 60, and outputs the image signal to the control unit 11. As described with reference to FIG. 1, the curl correction unit 90 includes a rubber roller 91, a metal roller 92, and the like, and performs curl correction on the paper conveyed by the conveyance unit 60 in accordance with instructions from the control unit 11.

  Next, curl correction processing will be described as an operation of the image forming apparatus 1 with reference to FIG. FIG. 6 shows the flow of the first curl correction process.

  In the first curl correction process, it is determined whether or not the paper before image formation fed from the paper feed cassette 4 is a back paper. If the paper is a back paper, the curl correction is performed on the back paper. It is. For example, after an image formation is instructed on the paper in the paper cassette 4 from an external device, an area having a certain length from the front end of the paper P taken out from the paper cassette 4 and conveyed is detected by the detection unit 80. The first curl correction process is executed by the control unit 11 using the reading as a trigger.

  First, based on the image signal of the paper whose fixed area is detected by the detection unit 80, it is determined whether or not the paper being transported is a back paper (step S1). For example, when the image signal of a certain area of the paper detected by the detection unit 80 includes a print portion of one or more characters, it is determined that the paper is the back paper. For this reason, when the paper is an open paper and there is a little dirt or scratch, it is not determined that the paper is a backing paper.

  When the paper being transported is the back paper (step S1; YES), the curl correction unit 90 is set to the curl correction state, the paper being transported (back paper) is curled (step S2), and the first curl is set. The correction process ends. Specifically, in step S2, as shown in FIG. 3, in the curl correction unit 90, the curl correction cam 93 is rotationally driven to form a concave nip portion between the rubber roller 91 and the metal roller 92. Put into a state. The paper (back paper) that has been subjected to curl correction by the curl correction unit 90 is conveyed to the registration rollers 65A and 65B by the control of the control unit 11, and the image formation timing is adjusted, and the image formation unit 40 forms the image. The paper is discharged to the paper discharge tray 3. For this reason, it is possible to prevent a skew correction shift in the registration rollers 65A and 65B, a print shift in the image forming unit 40, and a jam.

  When the paper being transported is not the back paper (step S1; NO), the curl correction unit 90 is set to a state where no curl correction is performed, and the paper being transported (opened paper) passes through the curl correction unit 90 without being curled. (Step S3), and the first curl correction process ends. Specifically, in step S3, as shown in FIG. 2, the curl correction unit 90 is driven to rotate the curl correction cam 93 so that the rubber roller 91 and the metal roller 92 are separated from each other. The paper (opened paper) that has not been curled by the curl correcting unit 90 is conveyed to the registration rollers 65A and 65B by the control of the control unit 11, and the image forming timing is adjusted, and the image forming unit 40 forms an image. The paper is then discharged to the paper discharge tray 3 or a double-sided image is formed. Since the paper is not curled, there is no skew correction deviation in the registration rollers 65A and 65B, print deviation in the image forming unit 40, or jamming.

  As described above, according to the present embodiment, the detection unit 80 detects an image on the back side of the sheet being conveyed from the paper feed cassette 4, and the curl correction unit 90 determines whether the registration rollers 65 </ b> A and 65 </ b> B and the paper feed cassette 4 are connected. The control unit 11 determines whether or not the paper being conveyed is a backing paper according to the detection result by the detection unit 80. The curl is corrected by the curl correction unit 90, and when the paper is not the back paper, the back paper is passed through the curl correction unit 90 without being curled. For this reason, the curl of the backing paper conveyed from the paper feed cassette 4 can be corrected before the image formation, and the skew correction deviation in the registration rollers 65A and 65B, the print deviation in the image forming unit 40, and the occurrence of jamming can be prevented.

  Further, the curl correction unit 90 includes a roller pair of a rubber roller 91 and a metal roller 92, and the rubber roller 91 and the metal roller 92 are pressed or separated by the curl correction cam 93 and the spring portion 94. Therefore, the configuration of the curl correction unit 90 can be simplified, and the state in which the rubber roller 91 and the metal roller 92 are pressed against each other when curl correction is performed can be freely switched between the state in which the rubber roller 91 and the metal roller 92 are not separated from each other.

(Second Embodiment)
A second embodiment according to the present invention will be described with reference to FIGS. In the present embodiment, the same device components as those in the first embodiment are denoted by the same reference numerals, description thereof is omitted, and different portions are mainly described.

  First, the apparatus configuration of the present embodiment will be described with reference to FIGS. FIG. 7 shows a schematic configuration of the image forming apparatus 1A of the present embodiment.

  The image forming apparatus 1A performs curl correction when the paper is the back paper according to the setting information as to whether the back paper is set as the paper in the paper feed cassette 4 set by an operation input by the user. The image forming apparatus performs image formation without performing curl correction when a sheet is not a back sheet.

  As illustrated in FIG. 7, the image forming apparatus 1 </ b> A includes the same components as the image forming apparatus 1, but does not include the detection unit 80.

  Next, the circuit configuration of the image forming apparatus 1 will be described. FIG. 8 shows a circuit configuration of the image forming apparatus 1A. As shown in FIG. 8, the image forming apparatus 1 </ b> A has a configuration in which the ROM 13 is replaced with the ROM 13 </ b> A and a flash memory 16 is further added in the image forming apparatus 1.

  The ROM 13A stores a setting program and a second curl correction program. The flash memory 16 is a non-volatile storage unit that can read and write data.

  Next, the operation of the image forming apparatus 1A will be described with reference to FIGS. FIG. 9 shows the flow of the setting process. FIG. 10 shows the flow of the second curl correction process.

  The control unit 11 executes setting processing according to the setting program stored in the ROM 13A. The setting process is a process for setting whether or not to set the back paper in the paper feed cassette 4 in accordance with a user operation input. For example, the setting process is executed by the control unit 11 when a setting process execution instruction is input to the operation unit 20 as a trigger.

  As shown in FIG. 9, first, the operation unit 20 accepts an operation input of setting information as to whether or not a backing paper is set in the paper feed cassette 4 from the user (step S11). When the back paper is set in the paper feed cassette 4 or newly set, the user inputs setting information to the effect that the back paper is set to the operation unit 20, and the open paper is loaded in the paper feed cassette 4. When set or newly set, setting information indicating that the backing paper is not set is input to the operation unit 20. Then, the setting information input in step S11 is stored in the flash memory 16 (step S12), and the setting process ends.

  After the setting process is executed, the control unit 11 executes the second curl correction process using the second curl correction program stored in the ROM 13A. The second curl correction process determines whether or not the paper fed from the paper feed cassette 4 is a backing paper based on the setting information stored in the flash memory 16. This is processing for setting curl correction. For example, the control unit 11 executes the second curl correction process triggered by an instruction from the external device to form an image on the paper in the paper feed cassette 4.

  As shown in FIG. 10, first, the setting information stored in the flash memory 16 is read out, and it is determined whether or not the back paper is set as the paper in the paper cassette 4 according to the setting information. (Step S21).

  When the back paper is set in the paper feed cassette 4 (step S21; YES), the curl correction unit 90 is set to the curl correction state (step S22), and the second curl correction process is ended. Specifically, in step S22, as shown in FIG. 3, in the curl correction unit 90, the curl correction cam 93 is rotationally driven, and a concave nip portion is formed between the rubber roller 91 and the metal roller 92. Put into a state. Under the control of the control unit 11, the paper (back paper) instructed to form an image is conveyed one by one by the conveyance unit 60, curled by the curl correction unit 90, conveyed to the registration rollers 65A and 65B, and imaged. The formation timing is adjusted, an image is formed by the image forming unit 40, and is discharged to the paper discharge tray 3. For this reason, it is possible to prevent a skew correction shift in the registration rollers 65A and 65B, a print shift in the image forming unit 40, and a jam.

  When the paper in the paper feed cassette 4 is not set as the back paper (step S21; NO), the curl correction unit 90 is set to a state where no curl correction is performed, and the paper being transported (opened paper) is curled. Without passing the curl correction unit 90 (step S23), the second curl correction process ends. Specifically, in step S23, as shown in FIG. 2, in the curl correction unit 90, the curl correction cam 93 is driven to rotate so that the rubber roller 91 and the metal roller 92 are separated from each other. Under the control of the control unit 11, the paper (opened paper) instructed to form an image is conveyed one by one by the conveying unit 60, not curled by the curl correcting unit 90, and conveyed to the registration rollers 65A and 65B. The image formation timing is adjusted, and an image is formed by the image forming unit 40 and is discharged to the discharge tray 3 or double-sided image formation is performed. Since the paper is not curled, there is no skew correction deviation in the registration rollers 65A and 65B, print deviation in the image forming unit 40, or jamming.

  As described above, according to the present embodiment, the curl correction unit 90 is provided on the conveyance path between the registration rollers 65A and 65B and the paper feed cassette 4, and the back paper is set in the paper feed cassette 4 in the operation unit 20. When the setting information indicating whether or not the sheet is set is input, the control unit 11 determines whether or not the sheet conveyed from the sheet feeding cassette 4 is the backing paper according to the setting information. The curl correction unit 90 causes the curl correction unit 90 to curl the paper, and if the back paper is not the back paper, the curl correction unit 90 passes the back paper without curling. For this reason, the curl of the backing paper conveyed from the paper feed cassette 4 can be corrected before the image formation, and the skew correction deviation in the registration rollers 65A and 65B, the print deviation in the image forming unit 40, and the occurrence of jamming can be prevented.

  The description in each of the above embodiments is an example of a suitable image forming apparatus according to the present invention, and the present invention is not limited to this.

  For example, at least two of the above embodiments and the following configurations may be appropriately combined.

  In each of the above embodiments, the image forming apparatus is an electrophotographic color printer. However, the present invention is not limited to this. For example, an apparatus such as an electrophotographic black-and-white printer, a black-and-white or color copier, or a multifunction peripheral may be used as the image forming apparatus.

  In each of the above embodiments, the detection unit 80 and the curl correction unit 90 are provided in the conveyance path between the registration rollers 65A and 65B and the paper feed cassette 4, and the paper conveyed from the paper feed cassette 4 is the back paper. In such a case, the curl correction is performed on the backing paper. However, the present invention is not limited to this. For example, in the first embodiment, the detection unit 80 and the curl correction unit 90 are provided on the conveyance path between the registration rollers 65A and 65B (or the image forming unit 40) and the manual feed tray 5 (and the paper feed cassette 4). It is also possible to adopt a configuration in which when the paper conveyed from the manual feed tray 5 (or the paper feed cassette 4) is a backing paper, the backing paper is subjected to curl correction. Similarly, in the second embodiment, a curl correction unit 90 is provided between the registration rollers 65A and 65B (or the image forming unit 40) and the manual feed tray 5 (and the paper feed cassette 4), and the manual feed tray 5 is provided. Alternatively, when setting information indicating that the paper set in the paper feed cassette 4 is the back paper is input to the operation unit 20, the back paper may be curled. In the image forming apparatus, a plurality of paper feed cassettes may be provided.

  In each of the above embodiments, the curl correction unit 90 has a pair of rollers that are in pressure contact with each other during curl correction. However, the present invention is not limited to this. As the curl correction unit, for example, an endless belt hung on a plurality of rollers and a pressure roller are provided, and the belt and the pressure roller are pressed against each other during curl correction, and the sheet passes through the nip portion. Also good. Further, it is also possible to provide a configuration in which an ironing material such as a blade is provided and the paper is ironed with the ironing material at the time of curl correction.

  In the first embodiment, the detection unit 80 reads an image of a certain area from the leading edge of the back surface of the conveyed sheet, and the control unit 11 performs conveyance of the sheet based on the image signal of the certain area. However, the present invention is not limited to this. For example, the detection unit 80 is provided at a position where an image can be read from the entire back surface or a part of the area of the conveyed paper, and the control unit 11 reads the image of the entire surface or a part of the region read by the detection unit 80. Based on the signal, it may be configured to determine whether or not the sheet being conveyed is the back side.

  Further, the detailed configuration and detailed operation of each part constituting the image forming apparatuses 1 and 1A in the above embodiments can be appropriately changed without departing from the gist of the present invention.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to a first embodiment of the present invention. It is a figure which shows the structure of the curl correction part at the normal time. It is a figure which shows the structure of the curl correction part at the time of curl correction. It is a figure which shows the structure of a detection part. 1 is a block diagram illustrating a circuit configuration of an image forming apparatus according to a first embodiment. It is a flowchart which shows a 1st curl correction process. 1 is a diagram illustrating a schematic configuration of an image forming apparatus according to a second embodiment of the present invention. 6 is a block diagram illustrating a circuit configuration of an image forming apparatus according to a second embodiment. FIG. It is a flowchart which shows a setting process. It is a flowchart which shows a 2nd curl correction process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1A Image forming apparatus 2 Housing | casing 3 Paper discharge tray 4 Paper feed cassette 5 Manual feed tray 11 Control part 20 Operation part 30 Display part 12 Image memory 13, 13A ROM
14 Communication unit 15 Bus 16 Flash memory 40 Image forming unit 40a Image forming main unit 40Y Yellow image forming unit 40M Magenta image forming unit 40C Cyan image forming unit 40K Black image forming unit 41 Photosensitive drum 42 Charging unit 43 Exposure unit 44 Developing unit 45 Primary transfer roller 46 Cleaning unit 47 Intermediate transfer belt 48 Secondary transfer driving roller 49 Driven roller 50 Cleaning unit 40b Fixing unit 51 Fixing roller 52 Pressing roller 60 Conveying units 61, 64A, 64B Feeding rollers 62A, 62B, 63A, 63B , 67A, 67B, 68A, 68B, 69A, 69B, 70A, 70B Conveying rollers 65A, 65B Registration roller 66 Pressing roller 60a Conveying path 60b Reversing path 80 Detection unit 81 Light emitting element 82 Light receiving element 90 Curl correction unit 91 Rubber roller 91a Rubber part 91b Shaft part 92 Metal roller 92a Metal part 92b Shaft part 93 Curl correction cam 94 Spring part

Claims (4)

A paper supply unit for supplying paper;
An image forming unit that forms an image on a sheet conveyed from the sheet feeding unit based on image data;
A detection unit for detecting an image on the back side of the sheet being conveyed from the sheet feeding unit;
A curl correction unit that corrects curl of a sheet conveyed along a conveyance path between the image forming unit and the sheet feeding unit;
A control unit that determines whether or not the paper being conveyed is a back paper according to a detection result by the detection unit, and when the paper is a back paper, a control unit that causes the curl correction unit to curl the back paper; And an image forming apparatus. A paper supply unit for supplying paper;
An image forming unit that forms an image on a sheet conveyed from the sheet feeding unit based on image data;
A curl correction unit that corrects curl of a sheet conveyed along a conveyance path between the image forming unit and the sheet feeding unit;
An operation unit for accepting an operation input of setting information indicating that a backing paper is set as paper in the paper feeding unit;
In accordance with the setting information input to the operation unit, it is determined whether or not the sheet conveyed from the sheet feeding unit is a backing paper. If the sheet is a backing sheet, the sheet is conveyed from the sheet feeding unit. An image forming apparatus comprising: a control unit that causes the curl correction unit to perform curl correction on a backing paper. A registration roller for conveying the paper to the image forming unit;
The image forming apparatus according to claim 1, wherein the curl correction unit corrects a curl of a sheet conveyed along a conveyance path between the registration roller and the sheet feeding unit.   The curl correction unit includes a first roller and a second roller, and the state where the first roller and the second roller are in pressure contact with each other, and the first roller and the second roller are The image forming apparatus according to claim 1, wherein the image forming apparatus is switchable between a separated state and a separated state.

Images