JP2006027799A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high quality image by correcting the carried amount of a carrying roller to reduce the disturbance of the image resulting from a variation in the carrying speed of a paper sheet based on the difference of carrying routes used and a difference in the type and thickness of the paper sheet in an image forming device having two or more types of carrying routes. <P>SOLUTION: This ink jet recording device 1 comprises the first carrying route C and the second carrying route D. In the first carrying route C, the paper sheet from the paper feed unit 21 is attracted onto an electrification belt 12, wound around a carrying roller 10 at a winding angle of approximately 90°, and carried in a horizontal direction. In the second carrying route D, the paper sheet from a manual paper feed part 27 is wrapped around the carrying roller 10 at a small winding angle, and fed in a horizontal direction. Since the paper winding angles of the first carrying route C and the second carrying route D are different from each other, the driving amount of the carrying roller 10 is determined based on the winding angle and the thickness of the paper sheet. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a printer, a copying machine, and a facsimile machine, and more specifically, in a transport apparatus having a plurality of transport paths for transporting a recording medium to an image forming position, regardless of which transport path is used. The present invention relates to an image forming apparatus in which the quality of formed images is not different.

  In an image forming apparatus such as a printer, a copying machine, or a facsimile machine, a paper feeding unit including a plurality of paper feeding trays provided below the image forming apparatus main body, and a manual paper feeding unit provided above the image forming apparatus main body As described above, an image forming apparatus having a plurality of conveyance paths for conveying a recording medium such as paper to a recording head position is widely used. In an image forming apparatus having at least two types of conveyance paths, the former conveyance path has a winding angle around the conveyance roller at the time of paper feeding (a large winding angle of about 60 ° or more), and a paper feed amount In general, the latter conveyance path has a wrapping angle of the paper around the conveyance roller of a certain value or less (a small wrapping angle of 60 ° or less).

  When there are two types of conveyance paths with different winding angles of the paper with respect to the conveyance roller, the conveyance path radius that determines the conveyance amount of the paper by winding the paper in the former conveyance path with a large winding angle is the conveyance roller. It is a value obtained by adding almost half of the thickness of the paper to the radius. Further, the transport amount in the latter transport path with a small winding angle is determined only by the transport roller diameter, and almost half of the thickness of the sheet is not added. For this reason, even if the conveyance rollers are driven to rotate at the same speed, a difference in the conveyance amount occurs due to the difference in the conveyance path and the thickness of the paper, and a difference occurs in the image depending on the type of the conveyance path and the thickness of the paper. It is a cause.

A technique for adjusting the driving amount of a conveyance roller with respect to conveyance of a sheet using a conveyance roller is known, and Patent Document 1 discloses an image for the purpose of eliminating an abnormal image or a paper passing defect caused by a paper type. It is disclosed that information on the manufacturer, model number, and amount of paper information is input from an operation unit of the forming apparatus, and each control condition is changed based on the information.
Also, in Patent Document 2, in order to accurately cut a roll paper at a target cutting position regardless of the paper type, when the cut line printed by the recording head is sent to the cutter blade, the paper type is included in the rotation amount of the transport roller. It is disclosed that a unique correction value is added to each.
Further, Patent Document 3 is provided with a document speed detecting means for detecting a document speed during document reading for the purpose of obtaining a normal image even when the document slips due to paper type or deterioration with time. It is disclosed that correction according to the detected document speed is performed on image data.
JP 2003-84507 A JP 2003-260833 A JP 2002-232656 A

  The present invention has been made in view of the above circumstances, and the invention of claim 1 is directed to a conveyance path to be used in an image forming apparatus having at least two types of conveyance paths in which a recording medium is conveyed by a conveyance roller. Based on the difference and the difference in the type and thickness of the recording medium to be conveyed, the conveyance amount of the conveyance roller is corrected and conveyed, so that the conveyance amount of the recording medium with respect to the recording head is constant, and the conveyance speed of the recording medium is An object of the present invention is to provide an image forming apparatus capable of reducing image disturbance due to change and obtaining a high-quality image.

  According to the second aspect of the present invention, in addition to the object of the first aspect of the invention, the data input to the image forming apparatus is stored in the data storage means by storing the correction value of the feed amount of the conveying roller for the type and thickness of the recording medium. The purpose is to reduce.

In the invention of claim 2, since the correction value for each recording medium is stored in the data storage means and the conveyance amount of the recording medium is determined, the time change occurs due to wear of the conveyance roller and each bearing. As a result, an error occurs between the correction value stored in the data storage means and the actual feed amount, and the image may be disturbed.
Accordingly, the invention of claim 3 is to remove the error by changing the correction value stored in the data storage means when an error occurs between the correction value stored in the data storage means and the actual feed amount. Objective. Also, by changing only the correction value of the conveyance amount of the conveyance roller for a specific recording medium, the correction value of the conveyance amount set for another type of recording medium stored in the data storage unit is also changed at the same time. By doing so, it is an object to greatly reduce the trouble of correcting the error of the data stored in the data storage means.

  According to the invention of claim 4, in addition to the object of the invention of claim 1, the recording medium thickness is automatically measured, thereby saving the trouble of inputting the recording medium type data in claims 2 and 3 to the image forming apparatus. The purpose is to prevent erroneous input.

According to the first to fourth aspects of the present invention, the trailing edge of the recording medium causes the conveyance roller to be wound when the winding angle of the conveyance roller is corrected to a certain value (approximately 60 ° or more) when the recording medium is fed. The same correction is made after leaving. However, the amount of conveyance after the trailing edge of the recording medium leaves the winding of the conveying roller is determined only by the diameter of the conveying roller, and almost half of the thickness of the recording medium is not added. It has become.
An object of the present invention is to reduce image disturbance at the rear end of the recording medium by correcting the recording medium feed error at the rear end of the recording medium.

  According to a first aspect of the present invention, there is provided an image forming unit that forms an image on a recording medium, a conveyance path that conveys the recording medium to an image forming position by a conveyance roller, and a discharge path that discharges the recording medium after image formation. An image forming apparatus that controls a conveyance amount of the recording medium by monitoring a driving amount of the conveyance roller, wherein the conveyance path includes two or more types of conveyance paths having different winding angles of the recording medium with respect to the conveyance roller. The driving amount of the conveyance roller is corrected based on the winding angle of the recording medium around the conveyance roller and the thickness of the recording medium.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the correction value of the driving amount of the conveying roller set according to the type of the recording medium and the type of the conveying path are set. Data storage means for storing a correction value of the driving amount of the transport roller, and driving of the transport roller based on the data of the recording medium input to the image forming apparatus and the data stored in the data storage means A correction amount of the amount is calculated, and the driving amount of the transport roller is corrected based on the calculation result.

  According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, an image of a specific pattern is formed on a specific recording medium stored in the data storage means, and an output result of the image of the specific pattern The error amount of the correction value is read on the basis of the data, and the correction value of the driving amount of the transport roller stored in the data storage unit is input to the data storage unit to change, and the other stored in the data storage unit The correction value of the driving amount of the conveying roller set for the type of recording medium is also changed at the same time.

  According to a fourth aspect of the present invention, in the image forming apparatus according to the first aspect, a sensor for measuring the thickness of the recording medium is disposed upstream of the image forming unit, and the output of the sensor and the conveying roller of the recording medium. A correction amount of the driving amount of the transport roller is calculated based on a winding angle with respect to the roller, and the driving amount of the transport roller is corrected based on the calculation result.

  According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the conveyance is performed in accordance with a decrease in a winding angle with respect to the conveyance roller when the rear end portion of the recording medium is separated from the conveyance roller. The correction amount of the driving amount of the roller is changed.

  According to the first aspect of the present invention, the conveyance amount of the recording medium to the image forming unit is always constant by correcting the feeding amount of the recording medium by the conveyance roller according to the difference in the conveyance path and the type and thickness of the recording medium. It is possible to provide an image forming apparatus that does not disturb the image due to the difference in the conveyance path, the type of the recording medium, and the thickness.

  According to the second aspect of the invention, the data input to the image forming apparatus is reduced by storing the correction value of the driving amount of the conveying roller for each recording medium type and conveying path type in the data storage means. Can do.

  According to the invention of claim 3, when an error occurs between the drive amount correction value stored in the data storage means and the actual drive amount due to a temporal change or the like, the correction value stored in the data storage means is changed. In addition, by having the function of eliminating the error, when an error occurs in the data stored in the data storage unit, the error can be corrected. Further, by changing only the correction value for the conveyance amount of a specific recording medium, the correction value for the conveyance amount set for other types of recording media stored in the data storage means is also changed at the same time. By configuring, it is possible to greatly reduce the trouble of correcting the error of the data stored in the data storage means having the configuration of claim 2.

  According to the invention of claim 4, by automatically measuring the thickness of the recording medium, the trouble of inputting the data of the type of the recording medium in the inventions of claims 2 and 3 to the image forming apparatus can be saved, and an erroneous input is made. Can be prevented.

  According to the fifth aspect of the invention, by correcting the recording medium feed error at the rear end of the recording medium, it is possible to reduce image disturbance at the rear end of the recording medium.

  In an image forming apparatus having at least two or more types of conveyance paths in which a recording medium is conveyed by a conveyance roller, the present invention is based on the difference in the conveyance path to be used and the difference in the type and thickness of the conveyed recording medium. By correcting the transport amount of the transport roller and transporting the recording medium to the image forming unit at a constant speed, image disturbance caused by changes in the transport speed of the recording medium can be reduced, and high-quality images can be obtained. The image forming apparatus is configured to provide an image forming unit that forms an image on a recording medium, and a conveyance path that conveys the recording medium to an image forming position by a conveyance roller. An image forming apparatus that controls a conveyance amount of the recording medium by monitoring a driving amount of the conveyance roller. The conveyance path includes two or more types of conveyance paths having different winding angles of the recording medium with respect to the conveyance roller, and the conveyance roller is based on the winding angle of the recording medium with respect to the conveyance roller and the thickness of the recording medium. The driving amount is corrected.

The image forming apparatus of the present invention will be described below based on examples.
FIG. 1 is a side sectional view showing the overall configuration of the ink jet recording apparatus according to the first embodiment, and FIG. 2 is a side sectional view showing a sheet conveying apparatus and a discharging apparatus portion in FIG.
The inkjet recording apparatus 1 according to the first exemplary embodiment discharges a sheet after image formation, an image forming unit that forms an image on a recording medium such as a sheet, a conveyance path that includes a conveyance roller that conveys the sheet to an image forming position, and the like. It consists of a discharge route. The ink jet recording apparatus 1 shown in FIG. 1 shows an example in which an electrostatic conveyance method using a charged conveyance belt is adopted as a conveyance device at a portion facing a recording head in a conveyance path provided with a conveyance roller. .

  The conveyance path includes a conveyance roller 10, a tension roller 11, and a conveyance unit that is wound between the conveyance roller 10 and the tension roller 11, and includes a charging conveyance belt 12 that is an endless belt. The electrification transport belt 12 is formed with an insulating layer (not shown) on the surface layer so as to retain electric charge, and may be an endless belt formed in an endless shape, or an endless shape in which both ends of a long belt are connected to each other. A belt may be used. The conveyance roller 10 belongs to a drive system, is driven by a driving unit such as a motor (not shown), and the conveyance roller 10 is driven and controlled by a conveyance control device, thereby conveying a predetermined amount of paper at a predetermined timing.

  The ink jet recording apparatus 1 includes a recording head 13 serving as a recording unit that performs recording by ejecting droplets of ink or the like onto a sheet (not shown) conveyed by a charging conveyance belt 12, and a recording head. When the liquid droplets 13 are ejected, a carriage 9 for reciprocating (main scanning) in a direction perpendicular to the paper surface of FIG.

  A conveyance guide plate 14 serving as a guide member for guiding the charging conveyance belt 12 from the inside is arranged at a position between the conveyance roller 10 and the tension roller 11 and facing the recording head 13 inside the charging conveyance belt 12. The charging means is provided at a position opposite to the conveying roller 10 to charge the charging conveyance belt 12 that electrostatically attracts and conveys the sheet, specifically, the insulating layer that forms the surface layer of the charging conveyance belt 12. A charging roller 15 is provided.

  In addition, a pressure roller 16 is disposed on the upstream side of the recording head 13 in the moving direction A of the charging conveyance belt 12 so as to press the sheet against the conveyance roller 10 via the charging conveyance belt 12. A separation claw 17 is provided on the downstream side of the recording head 13 in the moving direction A so as to separate the paper from the charging conveyance belt 12 so as to be pressed against the tension roller 11 via the charging conveyance belt 12. .

  In the lower part of the recording apparatus main body, a sheet feeding tray 18 loaded with sheets, a sheet feeding roller 19 for feeding sheets from the sheet feeding tray 18, and a sheet fed from the sheet feeding roller 19 are separated and sent out by one sheet. The separation pad 20 is provided. The paper feed tray 18, the paper feed roller 19, and the separation pad 20 constitute a paper feed unit 21.

  A guide that is positioned upstream of the pressure roller 16 and that opposes the conveying roller 10 and guides the sheet separated and fed by the separation pad 20, that is, the sheet fed from the sheet feeding unit 21 substantially vertically upward. A member 29 and a guide roller 32 are disposed, and further, a sheet that is positioned on the upstream side of the pressure roller 16 in the moving direction A of the charging and conveying belt 12 and guided substantially vertically upward by the guide member 29. A guide member 22 that is transported between the charging transport belt 12 and the pressure roller 16 is disposed by changing the direction approximately 90 ° and transporting in a substantially horizontal direction.

  The guide member 22 has an arcuate conveyance path between the guide member 22 and the charging conveyance belt 12 wound around the conveyance roller 10 so as to change the direction of the sheet guided substantially vertically upward by approximately 90 °. Therefore, the surface facing the charging / conveying belt 12 has an arc shape having a radius of curvature larger than that of the charging / conveying belt 12.

  Located on the downstream side of the recording head 13 in the moving direction A of the charging conveyance belt 12, a roller pair 23 for conveying the sheet separated from the charging conveyance belt 12 by the separation claw 17 is provided. The roller pair 23 is shown in FIG. 1 as having a simple circular cross section. However, the cross section star spur roller 24 having a protrusion on the circumference, a roller 25 facing and abutting against the spur roller 24, and a roller pair. 23, and a paper discharge tray 26 on which the paper fed by 23 is stacked.

  The spur roller 24 is engaged with the recording head side surface of the sheet on the downstream side of the recording head 13 in the moving direction A of the charging conveyance belt 12. When recording on cardboard, postcard, envelope, or other thick paper, it simply assists in feeding the paper, and the paper is biting between the spur roller 24 and the roller 25, that is, the spur roller 24 is paper. The gap between the surface of the sheet and the recording head 13 is not determined by the engagement.

  Further, the inkjet recording apparatus 1 manually feeds the paper substantially horizontally in the direction B shown in FIG. 1 to the image forming unit that performs recording by discharging droplets such as ink from the recording head 13 onto the paper. And a manual feed sensor 28 that detects the leading edge and the trailing edge of the paper fed from the manual paper feeder 27.

As described above, the inkjet recording apparatus 1 according to the first exemplary embodiment illustrated in FIG. 1 includes the first conveyance path C from the sheet feeding tray 18 to the conveyance roller 10 and the second conveyance path 10 from the manual sheet feeding unit 27 to the conveyance roller 10. Transport path D.
In the first conveyance path C, the paper separated and sent by the separation pad 20, that is, the paper sent out from the paper feeding unit 21, is guided almost vertically upward by the guide member 29, and the paper is charged by the charging belt. 12, and is wound around the transport roller 10 at a winding angle of approximately 90 °, changes its direction, and is transported in a substantially horizontal direction.
The second conveyance path D is fed from the manual sheet feeding unit 27, and the sheet is wound around the conveyance roller at a small wrapping angle of 60 ° or less, and substantially horizontally in the B direction with respect to the image forming unit that records on the sheet. Transport the paper toward you.

The operation of the ink jet recording apparatus of Example 1 will be described.
FIG. 3 is a side sectional view showing the relationship between the transport roller and the paper in the first transport path C.
As shown in FIG. 3, in the first conveyance path C, the sheet 41 expands on the front surface of the sheet 41 and contracts on the back surface due to the thickness of the sheet 41 and the winding of the sheet around the conveyance roller 10. Therefore, the diameter 43 of the first conveyance path C of the sheet for which the conveyance amount of the sheet 41 is determined is a value obtained by adding approximately ½ of the thickness Dy of the sheet 41 to the radius Rh of the conveyance roller 10. The actual feed radius Ro according to 10 is Ro = Rh + Dy / 2.
In addition, the actual feeding radius Ro by the conveying roller 10 in the second conveying path D that guides the sheet in the direction B substantially horizontally with respect to the image forming unit is Ro = Rh.

FIG. 4 is a conceptual diagram illustrating a procedure for determining the amount of paper transport and transporting the paper in the ink jet recording apparatus according to the first embodiment.
In the ink jet recording apparatus according to the first embodiment, the thickness data 50 of the paper 41 input to a conveyance control apparatus (not shown) and the conveyance path selection to use either the first conveyance path C or the second conveyance path D are used. 51, the calculation unit 52 calculates the correction value of the conveyance amount by the conveyance roller, outputs the result to the conveyance motor drive unit 53, drives the conveyance roller 54, and performs the sheet conveyance 55.

FIG. 5 is a conceptual diagram illustrating a procedure for determining the amount of paper transport and transporting the paper in the inkjet recording apparatus according to the second embodiment.
In the conceptual diagram of the second embodiment shown in FIG. 5, based on the paper type data 57 of the paper 41, the transport path selection 51, and the paper thickness data stored in the data storage unit 56, the transport amount is calculated by the calculation unit 52. The correction value is calculated, and the result is output to the transport motor drive unit 53 to transport the paper.

FIG. 6 is a conceptual diagram illustrating a procedure for determining the amount of paper transport and transporting the paper in the inkjet recording apparatus according to the third embodiment.
The ink jet recording apparatus according to the second embodiment cannot be changed when an error occurs in the data stored in the data storage unit 56 due to the wear of the transport roller 10 or the like, which causes the image to be distorted.
In the ink jet recording apparatus of the third embodiment, as shown in FIG. 6, a specific sheet is conveyed using data stored in the data storage unit 56, and a specific pattern is used for the specific sheet using a recording head. , The data correction 59 is performed on the stored transport amount data based on the output result of the specific pattern, and the data is input to the image forming apparatus, thereby being stored in the data storage unit 56. It has a function capable of changing the correction value of the sheet conveyance amount, and is configured to correct the error when an error occurs in the data stored in the data storage means 56.

  Further, by changing the correction value of the conveyance amount of the specific sheet, the correction value of the conveyance amount set for another type of sheet stored in the data storage unit 56 is also changed at the same time. In this configuration, it is possible to significantly reduce the trouble of correcting the error of the data stored in the data storage means 56 having the second configuration.

FIG. 7 is a conceptual diagram illustrating a procedure for determining the amount of paper transport and transporting the paper in the inkjet recording apparatus according to the fourth embodiment.
In the ink jet recording apparatuses according to the first to third embodiments, since the paper thickness data is input to the image forming apparatus, it is necessary to input the data again every time the paper is changed. Further, there is a possibility that image disturbance due to an input error may occur.
In the ink jet recording apparatus according to the fourth embodiment, as shown in FIG. 2, a reflection type paper thickness detection sensor 30 is attached upstream of the image forming unit to automatically detect the thickness of the paper, and the paper thickness detection sensor shown in FIG. By inputting the data to the calculation unit 52 as 58, it is possible to omit input of paper thickness or paper type data to the image forming apparatus and prevent erroneous input.

  In the image forming apparatuses according to the first to fourth embodiments, the paper trailing edge is wound around the conveyance roller 10 when the winding angle around the conveyance roller 10 is corrected to a certain value (approximately 60 ° or more) when the paper is fed. The same correction is made even after leaving. However, the amount of conveyance after the trailing edge of the paper leaves the winding of the conveyance roller 10 is determined only by the diameter of the conveyance roller, and a thickness that is almost half of the thickness of the paper is not taken into account. It is a factor that can be disturbed.

  In the ink jet recording apparatus according to the fifth embodiment, as shown in FIGS. 1 to 3, if the trailing edge of the sheet passes through the pressure roller 16, an error occurs in the feed amount. Therefore, the timing at which the rear end of the paper passes through the pressure roller 16 is predicted from the timing at which the registration sensor 31 passes through the rear end of the paper, and the feed amount after the rear end of the paper passes through the pressure roller 16 is shown in FIG. By changing the feed diameter 43 after the paper thickness correction shown in FIG. 3 to the conveyance roller diameter, the image disturbance is reduced.

1 is a side sectional view showing an overall configuration of an ink jet recording apparatus of Example 1. FIG. FIG. 2 is a side cross-sectional view showing a sheet conveying device and a discharging device portion in FIG. 1. FIG. 6 is a side cross-sectional view illustrating a relationship between a conveyance roller and a sheet in a first conveyance path C. FIG. 3 is a conceptual diagram illustrating a procedure for determining a sheet conveyance amount and conveying a sheet in the inkjet recording apparatus according to the first exemplary embodiment. FIG. 10 is a conceptual diagram illustrating a procedure for determining a sheet conveyance amount and conveying a sheet in the inkjet recording apparatus according to the second embodiment. FIG. 10 is a conceptual diagram illustrating a procedure for determining a sheet conveyance amount and conveying a sheet in the inkjet recording apparatus according to the third exemplary embodiment. FIG. 10 is a conceptual diagram illustrating a procedure for determining a sheet conveyance amount and conveying a sheet in the inkjet recording apparatus of Example 4.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Inkjet recording apparatus, 9 ... Carriage, 10 ... Conveyance roller, 11 ... Tension roller, 12 ... Charge conveyance belt, 13 ... Recording head, 14 ... Conveyance guide plate, 15 ... Charge roller, 16 ... Pressure roller, 17 ... Separation claw, 18 ... paper feed tray, 19 ... paper feed roller, 20 ... separation pad, 21 ... paper feed unit, 22 ... guide member, 23 ... roller pair, 24 ... spur roller, 25 ... roller, 26 ... paper discharge tray , 27 ... manual paper feed unit, 28 ... manual feed sensor, 29 ... guide member, 30 ... paper thickness detection sensor, 31 ... registration sensor, 32 ... guide roller, 41 ... paper, 42 ... paper center, 50 ... paper thickness data, 51: Conveyance path selection, 52: Calculation unit (calculation of correction value of conveyance roller feed amount), 53 ... Conveyance motor drive unit, 54 ... Conveyance roller, 55 ... Paper conveyance, 56 ... Data storage means, 7 ... paper type data, 58 ... paper thickness detection sensor.

Claims (5)

  An image forming unit that forms an image on a recording medium; a conveyance path that conveys the recording medium to an image forming position by a conveyance roller; and a discharge path that discharges the recording medium after image formation. In the image forming apparatus that controls the conveyance amount of the recording medium by monitoring the amount, the conveyance path includes two or more types of conveyance paths having different winding angles of the recording medium with respect to the conveyance roller. An image forming apparatus, wherein the driving amount of the conveying roller is corrected based on a winding angle with respect to the conveying roller and a thickness of the recording medium.   The image forming apparatus according to claim 1, wherein the correction value of the driving amount of the transport roller set according to the type of the recording medium and the correction of the driving amount of the transport roller set according to the type of the transport path. Data storage means for storing the value, and a correction amount for the driving amount of the transport roller is calculated based on the data of the recording medium input to the image forming apparatus and the data stored in the data storage means. An image forming apparatus that corrects the driving amount of the conveying roller based on the calculation result.   3. The image forming apparatus according to claim 2, wherein an image of a specific pattern is formed on a specific recording medium stored in the data storage unit, and the correction value is calculated based on an output result of the image of the specific pattern. An error amount is read and input to the data storage means to change the correction value of the driving amount of the transport roller stored in the data storage means, and to other types of recording media stored in the data storage means An image forming apparatus characterized in that the correction value of the driving amount of the conveying roller set in this way is also changed at the same time.   The image forming apparatus according to claim 1, wherein a sensor for measuring the thickness of the recording medium is disposed upstream of the image forming unit, and the conveyance is performed based on an output of the sensor and a winding angle of the recording medium with respect to the conveyance roller. An image forming apparatus that calculates a correction amount of a driving amount of a roller and corrects the driving amount of the transport roller based on the calculation result.   The image forming apparatus according to claim 1, wherein the correction amount of the driving amount of the conveying roller with a decrease in a winding angle with respect to the conveying roller when the rear end portion of the recording medium moves away from the conveying roller. An image forming apparatus characterized in that