JP2016166977A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device that can remove a foreign substance attached to a fixing roller without including an additional member to remove the foreign substance, and an image forming apparatus.SOLUTION: A fixing device comprises: a width acquisition part that acquires a width in a direction orthogonal to a direction of conveyance of a recording medium; and a control part 7 that, in performing fixing processing on a second recording medium after fixing processing on a first recording medium, when determining that the width of the second recording medium acquired by the width acquisition part 62 is larger than the width of the first recording medium, from a leading end on the downstream with respect to the direction of conveyance to a position by the same length as the circumference of a fixing member on a side in contact with a toner image, causes a position at which a toner image is not formed within a range from the leading end of a third recording medium at which a toner image is not formed to a position by the same length as the circumference to pass through a position corresponding to an end in a direction orthogonal to a direction of conveyance of the first recording medium at a nip part.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a fixing device and an image forming apparatus.

  Conventionally, in an electrophotographic image forming apparatus, a toner image formed on an image carrier (for example, a photosensitive drum) is transferred to a recording medium such as paper, and the toner image transferred to the recording medium is fixed. A fixing device is known. As this fixing device, for example, there is a configuration in which a recording medium onto which a toner image is transferred is conveyed while being nipped at a nip portion formed by pressing a heated fixing roller with a pressure roller.

  In such a fixing device, when fixing processing is performed on papers having different paper widths, for example, when fixing processing is performed on paper having a wide paper width after performing fixing processing on paper having a narrow paper width, An image defect may occur on a wide paper.

  More specifically, when fixing a paper having a narrow paper width, foreign matters such as paper dust at the edge of the paper in a direction orthogonal to the conveyance direction of the paper adheres to the fixing roller, and the paper edge of the paper ends on the surface of the fixing roller. Traces are generated. When fixing processing is performed on a sheet having a wide sheet width with the fixing roller in such a state, particularly when an unfixed image is formed at a position where the mark of the end of the sheet is generated, The trace of the paper edge is transferred to a paper having a wide paper width, and an image defect occurs on the paper having a wide paper width.

  For this reason, there is disclosed an image forming apparatus that includes a polishing member that comes in contact with and separates from a fixing roller and removes paper dust adhered to the fixing roller by the polishing member (see Patent Document 1). Further, an image forming apparatus is disclosed that removes paper dust adhering to a fixing roller by fixing a recording medium on which a black solid image is transferred with a fixing device (see Patent Document 2).

JP 2007-248680 A JP 2007-057702 A

However, in the image forming apparatus described in Patent Document 1, it is necessary to separately provide a polishing member, resulting in a complicated structure and high cost, and the polishing member directly contacts the fixing roller. There was a problem that it may cause scratches.
Further, when the abrasive member is brought into contact with the fixing roller, the heat of the fixing roller is deprived, and the temperature of the fixing roller needs to be adjusted again, leading to a decrease in productivity.

On the other hand, in the image forming apparatus described in Patent Document 2, paper powder adhering to the fixing roller is removed by fixing the recording medium on which the black solid image has been transferred by the fixing device. In addition, there is a possibility that the transfer of traces at the end of the paper may be promoted, and the amount of toner consumption increases due to the use of a recording medium on which a black solid image is transferred.
In addition, the image forming apparatus described in Patent Document 2 has a problem that a paper dust amount measuring unit for measuring the amount of paper dust needs to be provided separately, resulting in complicated structure and high cost. It was.

  An object of the present invention is to provide a fixing device and an image forming apparatus that can remove foreign matters attached to a fixing member without providing a separate member for removing foreign matters.

In order to achieve the above object, a fixing device according to claim 1 is provided.
In the fixing device for fixing the toner image to the recording medium by passing the recording medium on which the toner image is formed through a nip formed by heating and pressing at least one of a pair of fixing members.
A width acquisition unit for acquiring a width in a direction perpendicular to the conveyance direction of the recording medium;
When performing the fixing process of the second recording medium after the fixing process of the first recording medium, the width of the second recording medium acquired by the width acquisition unit is larger than the width of the first recording medium. If it is determined that the toner image is not formed with the same length as the peripheral length of the fixing member on the side in contact with the toner image from the downstream end with respect to the transport direction, A control unit that allows a position where a toner image up to the same length as the circumference to be formed passes through a position corresponding to an end portion of the nip portion in a direction orthogonal to the conveyance direction of the first recording medium;
It is characterized by having.

According to a second aspect of the present invention, in the fixing device according to the first aspect,
Provided with a type acquisition unit that acquires the type of recording medium,
The control unit is configured such that the width of the second recording medium acquired by the width acquisition unit is larger than the width of the first recording medium, and the second recording medium acquired by the type acquisition unit When it is determined that the type is a predetermined type, the third recording medium is allowed to pass.

According to a third aspect of the present invention, in the fixing device according to the first or second aspect,
Provided with a type acquisition unit that acquires the type of recording medium,
The control unit is configured such that a width of the second recording medium acquired by the width acquisition unit is larger than a width of the first recording medium, and the first recording medium acquired by the type acquisition unit When it is determined that the type is a predetermined type, the third recording medium is allowed to pass.

According to a fourth aspect of the present invention, in the fixing device according to any one of the first to third aspects,
A number acquisition unit for acquiring the number of fixing processes of the recording medium;
The control unit fixes the first recording medium acquired by the number acquisition unit when the width of the second recording medium acquired by the width acquisition unit is larger than the width of the first recording medium. If it is determined that the number of processed sheets is equal to or greater than a predetermined number, the third recording medium is allowed to pass.

According to a fifth aspect of the present invention, in the fixing device according to any one of the first to fourth aspects,
An image acquisition unit for acquiring the position of an image formed on a recording medium;
The control unit is configured such that a width of the second recording medium acquired by the width acquisition unit is larger than a width of the first recording medium, and the second recording medium acquired by the image acquisition unit When it is determined that the position of the image includes the position of the end in the direction orthogonal to the conveyance direction of the first recording medium, the third recording medium is allowed to pass.

According to a sixth aspect of the present invention, in the fixing device according to any one of the first to fifth aspects,
An image acquisition unit that acquires information on screen processing of an image formed on a recording medium;
The control unit is configured such that the width of the second recording medium acquired by the width acquisition unit is larger than the width of the first recording medium, and the screen processing acquired by the image acquisition unit is based on an error diffusion method. When it is determined that the screen processing is performed, the third recording medium is allowed to pass.

According to a seventh aspect of the present invention, in the fixing device according to any one of the first to sixth aspects,
A position adjusting unit for adjusting a position in a direction perpendicular to the conveyance direction of the recording medium;
When the control unit determines that the width of the third recording medium acquired by the width acquisition unit is smaller than the width of the first recording medium, the control unit controls the position adjustment unit to perform the third recording medium. The position of the medium is adjusted so that the medium passes through the end portion in the direction orthogonal to the conveyance direction of the first recording medium.

The invention according to claim 8 is the fixing device according to claim 7, wherein
The control unit controls the position adjusting unit to allow the third recording medium to pass through the nip portion so as to pass through one side of the end portion.

According to a ninth aspect of the present invention, in the fixing device according to the seventh aspect,
The control unit controls the position adjusting unit so that at least one of the plurality of third recording media passes through one side of the end and at least one passes through the other side of the end. As described above, the nip portion is passed through.

According to a tenth aspect of the present invention, in the fixing device according to the seventh aspect,
The control unit controls the position adjusting unit to pass the third recording medium through the nip portion so that the surface of the third recording medium passes through one side of the end portion and the back surface passes through the other side of the end portion. It is characterized by that.

According to an eleventh aspect of the present invention, in the image forming apparatus,
An image forming unit for forming a toner image on a recording medium;
The fixing device according to claim 1, further comprising: a fixing device that fixes the toner image onto the recording medium through the recording medium on which the toner image is formed.

  According to the present invention, it is possible to remove the foreign matter attached to the fixing member without providing a separate member for removing the foreign matter.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment to which the present invention is applied. FIG. 2 is a block diagram illustrating a functional configuration of the image forming apparatus in FIG. 1. FIG. 2 is an enlarged schematic view of a fixing device. It is a flowchart explaining the control operation of a control part. It is a flowchart explaining the other control operation of a control part. It is a flowchart explaining the other control operation of a control part. FIG. 10 is an explanatory diagram illustrating a paper position adjustment operation by a position adjustment unit.

(Embodiment)
Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples.
FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus 100 according to an embodiment to which the present invention is applied. FIG. 2 is a block diagram illustrating a functional configuration of the image forming apparatus 100.

As shown in FIGS. 1 and 2, the image forming apparatus 100 according to the present exemplary embodiment includes image data acquired by reading a color image formed on a document, or an external information device (for example, a personal computer) via a network. An image is formed by superimposing colors on a sheet (recording medium) M based on image data input from a computer.
In addition, the image forming apparatus 100 travels the photosensitive drums 43Y, 43M, 43C, and 43K corresponding to four colors of yellow (Y), magenta (M), cyan (C), and black (K) on the intermediate transfer belt 47a. This is a tandem type image forming apparatus that is arranged in series in the direction and sequentially transfers toner images of respective colors to a transfer medium in one procedure.

  Specifically, the image forming apparatus 100 of the present embodiment includes an image reading unit 1, an operation display unit 2, an image processing unit 3, an image forming unit 4, a transport unit 5, a fixing device 6, and a control. The unit 7 is provided.

  The image reading unit 1 includes an automatic document feeder 11 called an ADF (Auto Document Feeder), a document image scanning device (scanner) 12, and the like.

  The automatic document feeder 11 conveys the document placed on the document tray by the conveyance mechanism and sends it out to the document image scanning device 12. The automatic document feeder 11 can continuously read images (including both sides) of a large number of documents placed on the document tray at once.

The document image scanning device 12 optically scans a document conveyed on the contact glass from the automatic document feeder 11 or a document placed on the contact glass, and reflects light from the document to a CCD (Charge Coupled Device). ) An image is formed on the light receiving surface of the sensor 12a, and an original image is read. The image (analog image signal) read by the image reading unit 1 is subjected to predetermined image processing in the image processing unit 3.
Here, the image means not only image data such as graphics and photographs but also text data such as characters and symbols.

The operation display unit 2 includes a liquid crystal display (LCD) with a touch panel and the like, and functions as the display unit 21 and the operation unit 22.
The display unit 21 displays various operation screens, image status display, operation status of each function, and the like in accordance with a display control signal input from the control unit 7.
The operation unit 22 includes various operation keys such as a numeric keypad and a start key, receives various input operations by the user, and outputs an operation signal to the control unit 7.

The image processing unit 3 includes a circuit that performs analog-digital (A / D) conversion processing, a circuit that performs digital image processing, and the like.
The image processing unit 3 generates digital image data (RGB signals) by subjecting the analog image signal from the image reading unit 1 to A / D conversion processing. The image processing unit 3 performs color conversion processing, gradation reproduction processing (screen processing, etc.), correction processing (shading correction, etc.) according to initial settings or user settings, compression processing, and the like on the digital image data. . The image forming unit 4 is controlled based on the digital image data (YMCK signal) subjected to these processes.

  The image forming unit 4 includes exposure devices 41Y, 41M, 41C, and 41K, developing devices 42Y, 42M, 42C, and 42K, and a photosensitive drum 43Y, which are provided corresponding to different color components Y, M, C, and K. 43M, 43C, 43K, charging devices 44Y, 44M, 44C, 44K, lubricant application removing units 45Y, 45M, 45C, 45K, primary transfer rollers 46Y, 46M, 46C, 46K and intermediate transfer unit 47, etc. It is prepared for.

In the Y component unit of the image forming unit 4, the charging device 44Y charges the photosensitive drum 43Y. The exposure device 41Y is composed of, for example, a semiconductor laser, and irradiates the photosensitive drum 43Y with laser light corresponding to the Y component. As a result, an electrostatic latent image of the Y component is formed on the surface of the photosensitive drum 43Y. The developing device 42Y contains a Y-component developer (for example, a two-component developer composed of a toner having a small particle diameter and a magnetic material), and causes the Y-component toner to adhere to the surface of the photosensitive drum 43Y. Thus, the electrostatic latent image is developed (formation of a toner image).
Similarly, in the units for M component, C component, and K component, each color toner image is formed on the surface of the corresponding photosensitive drum 43M, 43C, 43K.

  The lubricant applying / removing portions 45Y, 45M, 45C, and 45K apply lubricant to the surfaces of the photosensitive drums 43Y, 43M, 43C, and 43K, and excessively adhere to the surfaces of the photosensitive drums 43Y, 43M, 43C, and 43K. Remove the lubricant and foreign matter.

The intermediate transfer unit 47 is configured by a plurality of support rollers 47b,... Being stretched with an endless intermediate transfer belt 47a serving as a transfer target.
When the intermediate transfer belt 47a is brought into pressure contact with the photosensitive drums 43Y, 43M, 43C, and 43K by the primary transfer rollers 46Y, 46M, 46C, and 46K, the toner images of the respective colors are sequentially superimposed and primarily transferred onto the intermediate transfer belt 47a. . Then, the intermediate transfer belt 47a subjected to the primary transfer is pressed against the paper M by the secondary transfer roller 48, whereby the toner image is secondarily transferred to the paper M.
The toner remaining on the intermediate transfer belt 47a after the secondary transfer is removed by a blade or the like of the cleaning device 49.

The transport unit 5 includes a paper feeding device 51, a transport mechanism 52, a paper discharge device 53, and the like.
The paper feeding device 51 includes three paper feeding tray units 51a to 51c. In these paper feed tray units 51a to 51c, standard paper and special paper identified based on the basis weight, size, and the like of the paper M are stored for each preset type. The sheets M accommodated in the sheet feeding tray units 51a to 51c are sent out one by one from the uppermost part, and are conveyed to the image forming unit 4 by a conveying mechanism 52 including a plurality of conveying rollers such as a registration roller 52a. At this time, the registration unit in which the registration roller 52a is disposed corrects the inclination of the fed paper M and adjusts the conveyance timing.
The paper feeding device 51 is provided with a manual tray unit 51d for manually supplying the paper M.

  Then, in the image forming unit 4, the toner image on the intermediate transfer belt 47 a is secondarily transferred onto the image forming surface of the paper M at once, and a fixing process is performed in the fixing device 6. The sheet M on which the image has been formed is discharged to a discharge tray 53b outside the apparatus by a discharge device 53 having a discharge roller 53a.

The fixing device 6 performs a fixing process for fixing the toner image transferred to the paper M.
Hereinafter, the fixing device 6 will be described in detail with reference to FIGS.

  FIG. 3 is an enlarged schematic view of the fixing device 6. As shown in FIG. 2, the fixing device 6 includes a fixing unit 61, a paper width acquisition unit (width acquisition unit) 62, a paper type acquisition unit (type acquisition unit) 63, a number acquisition unit 64, and an image acquisition unit 65. The position adjustment unit 66 is provided.

  The fixing unit 61 includes a pair of fixing members, a fixing roller 61a and a pressure roller 61b, and an external heating roller 61c that contacts the pressure roller 61b and heats the pressure roller 61b. A fixing heater 61d is provided inside the fixing roller 61a, and an external heating heater 61e is provided inside the external heating roller 61c. Further, the fixing roller 61a and the pressure roller 61b constitute a nip portion N that sandwiches and conveys the paper M.

The fixing roller 61a is disposed on the image forming surface side of the paper M, and the fixing roller 61a rotates in accordance with driving of a driving unit such as a motor (not shown).
The fixing roller 61a has a configuration in which an elastic layer made of silicone rubber or the like is formed on the outer peripheral surface of a cylindrical cored bar made of iron or the like, and a fixing device such as a halogen heater is used as the fixing heater 61d. The heater 61d is incorporated, and the sheet M is contacted with the image forming surface of the sheet M on which the toner image is transferred, and the sheet M is heated at a predetermined fixing temperature. That is, the fixing roller 61a contacts the image forming surface of the paper M while rotating and heats the paper M.
The predetermined fixing temperature is a temperature at which the amount of heat necessary to melt the toner when the paper M passes through the nip portion N, and varies depending on the paper type of the paper M on which an image is formed.

  The pressure roller 61b is disposed to face the fixing roller 61a, and is pressed against the fixing roller 61a with a predetermined pressing force. That is, the pressure roller 61b functions as a pressure unit that sandwiches and presses the paper M together with the fixing roller 61a.

  The pressure roller 61b has a configuration in which an elastic layer made of silicone rubber or the like is formed on the outer peripheral surface of a cylindrical metal core made of iron or the like. Further, since the surface of the pressure roller 61b is relatively hard with respect to the surface of the fixing roller 61a, the pressure roller 61b is pressed against the elastic layer on the surface of the fixing roller 61a while being pressed against the fixing roller 61a. A nip portion N having a biting shape is formed.

  The paper width acquisition unit 62 acquires information related to the paper width of the paper M conveyed to the fixing device 6. For example, the sheet width of the sheet M may be actually detected by an optical sensor such as a photodiode array, or the sheet width information of the sheet M is acquired from the job information stored in the storage unit of the control unit 7. There may be.

  The paper type acquisition unit 63 acquires information regarding the type of paper M conveyed to the fixing device 6. For example, it is possible to detect the type of paper on which the marks at the end of the paper are easily transferred by various sensors, and conversely, the type of paper that is likely to generate paper dust, or a job stored in the storage unit of the control unit 7. The type information of the sheet M may be acquired from the information.

  The number acquisition unit 64 acquires information regarding the number of sheets processed in the previous printing operation. For example, the number of passing sheets M may be actually detected by an optical sensor such as a photodiode, or the number information may be acquired from the job information stored in the storage unit of the control unit 7.

  The image acquisition unit 65 acquires information on screen processing applied to a halftone image such as an image position or a screen pattern to be printed this time. For example, a toner image actually formed on the sheet M may be detected by an image sensor or the like, or image information to be printed this time may be acquired from the image processing unit 3 or the image forming unit 4. Good. Screen processing is processing that creates color gradations with the number and density of color points. Further, information about whether or not the screen processing applied to the halftone image is the error diffusion method is acquired from the image processing unit 3.

  The position adjusting unit 66 is provided on the upstream side of the nip portion N, and adjusts the position of the sheet M passing through the nip portion N by moving the position of the conveyed sheet M in a direction orthogonal to the conveying direction. It is. For example, the sheet M is configured by a pair of rollers that sandwich the conveyed sheet M, and the pair of rollers is moved in a direction orthogonal to the conveyance direction by a driving unit such as an actuator while the sheet M is sandwiched. Adjust the position of M.

The control unit 7 includes, for example, a CPU (Central Processing Unit) 71, a ROM (Read Only Memory) 72, a RAM (Random Access Memory) 73, and the like.
The CPU 71 reads out a program corresponding to the processing content from the ROM 72 and expands it in the RAM 73, and cooperates with the expanded program in each block (image reading unit 1, operation display unit 2, image processing unit 3) of the image forming apparatus 100. The image forming unit 4, the conveying unit 5, the fixing device 6 and the like are centrally controlled. At this time, for example, various data stored in a storage unit (not shown) constituted by a nonvolatile semiconductor memory (flash memory) or a hard disk drive is referred to.

Here, the control unit 7 is connected to an external communication network such as a LAN or a WAN (Wide Area Network) via a communication unit (not shown) configured by a LAN (Local Area Network) card, for example. Various data may be transmitted / received to / from an apparatus (for example, a personal computer).

  Further, the control unit 7 controls the paper width acquisition unit 62, the paper type acquisition unit 63, the number-of-sheets acquisition unit 64, the image acquisition unit 65, and the like to acquire acquisition information from each acquisition unit, and controls the position adjustment unit 66. Thus, the position of the sheet M that has been conveyed is moved in a direction perpendicular to the conveyance direction, and the position of the sheet M that passes through the nip portion N is adjusted.

The storage unit such as the RAM 73 of the control unit 7 stores job information for image forming processing, for example,
Stored is information including paper width information, type information of the paper M stored in the paper feed tray units 51a to 51c, information on the number of papers M to be processed in the job, and the like.

  Here, the operation of the fixing device 6 will be described with reference to the flowchart shown in FIG. As shown in the flowchart of FIG. 4, the control unit 7 controls the paper width acquisition unit 62 to acquire the paper width of the paper M (step S41). For example, the paper width acquisition unit 62 acquires the paper width information of the paper M from the job information stored in the storage unit of the control unit 7.

  Then, the control unit 7 determines whether or not the acquired paper width is wider than the previous paper width (step S42), and the acquired paper width is wider than the previous paper width. If it is determined that this is not the case (step S42: No), the process proceeds to step S44.

  On the other hand, when it is determined that the acquired paper width is wider than the previous paper width (step S42: Yes), the paper M (cleaning sheet) on which no toner image is formed is passed through the nip portion N. (Step S43).

  Here, the sheet M (cleaning sheet) on which the toner image is not formed is, specifically, the same length as the peripheral length of the fixing roller 61a on the side in contact with the toner image from the leading end portion downstream in the transport direction. In the paper M on which the toner image is not formed, the control unit 7 determines that the position where the toner image from the leading edge of the paper M to the same length as the circumferential length is not formed is the position of the previous paper in the nip N. A position corresponding to an end portion in a direction orthogonal to the transport direction is passed.

  In this way, by passing the nip portion N without forming a toner image on the paper M (cleaning sheet) having a paper width wider than the previous paper width, a direction orthogonal to the conveyance direction of the paper attached to the fixing roller 61a. Foreign matter such as paper dust at the end of the paper is transferred to the paper M (cleaning sheet) having a wide paper width and removed from the fixing roller 61a.

  Finally, the control unit 7 performs a normal fixing process to fix the toner image transferred onto the paper M (step S44).

  In other words, even when the toner image is fixed on the paper M having a paper width wider than the previous paper width, foreign matters such as paper dust adhered to the fixing roller 61a are removed from the paper M (cleaning) on which the toner image is not formed. Since the image is transferred to the sheet and removed, it is possible to prevent image defects from occurring on a sheet having a wide sheet width.

  As described above, according to the image forming apparatus 100 of the present embodiment, the paper width acquisition unit 61 that acquires the width in the direction orthogonal to the conveyance direction of the paper M, and the acquisition result of the paper width acquisition unit 61 determines the previous paper M. A control unit 7 for passing the paper M on which no toner image is formed to the nip portion N when it is determined that the width in the direction orthogonal to the current paper conveyance direction is larger than the width in the direction orthogonal to the conveyance direction; Since the foreign matter such as paper dust adhering to the fixing roller 61a is transferred to the paper M on which the toner image is not formed and is removed, a separate member is not provided to remove the paper dust. The foreign matter adhering to the fixing roller 61a can be removed.

(Modification 1)
In the description of the embodiment, when the control unit 7 determines that the width in the direction orthogonal to the transport direction of the current sheet M is larger than the width in the direction orthogonal to the transport direction of the previous sheet M, the toner image is Although the paper M not formed is passed through the nip portion N, the paper M on which no toner image is formed may be passed through the nip portion N in combination with other conditions.
Note that the paper M on which no toner image is formed is the same as that described in the embodiment, and the passing method of the nip portion N by the control unit 7 is also the same.

  Here, the operation of the fixing device 6 of Modification 1 will be described with reference to the flowchart shown in FIG. As shown in the flowchart of FIG. 5, the control unit 7 controls the paper width acquisition unit 62 to acquire the paper width of the paper M (step S51). For example, the paper width acquisition unit 62 acquires the paper width information of the paper M from the job information stored in the storage unit of the control unit 7.

  Then, the control unit 7 determines whether or not the acquired paper width is wider than the previous paper width (step S52), and the acquired paper width is wider than the previous paper width. If it is determined that this is not the case (step S52: No), the process proceeds to step S59.

  On the other hand, when the control unit 7 determines that the acquired paper width is wider than the previous paper width (step S52: Yes), the control unit 7 controls the paper type acquisition unit 63 to acquire the paper width. It is determined whether or not the paper type of the current paper is a predetermined paper type (step S53). Specifically, it is determined whether or not the current paper M is the type of paper on which the trace of the previous paper edge is easily transferred. Examples of the paper on which the trace of the end of the previous paper is easily transferred include plain paper and uneven paper having a rough surface.

  When the control unit 7 determines that the paper type of the current paper acquired by controlling the paper type acquisition unit 63 is a predetermined paper type (step S53: Yes), the paper on which no toner image is formed M (cleaning sheet) is passed through the nip portion N (step S58), and the process proceeds to step S59.

  For example, when the paper M of this time is determined by the paper type acquisition unit 63 to be the type of paper on which the trace of the paper edge is easily transferred, there is a possibility that an image defect occurs on a paper having a wide paper width. Since it is high, the paper M on which no toner image is formed is passed through the nip portion N.

  Further, for example, when the paper type acquisition unit 63 determines that the current paper M is the type of paper on which the paper edge trace is difficult to transfer, an image defect may occur on a wide paper. Therefore, the sheet M on which no toner image is formed can be prevented from passing through the nip portion N.

  Further, when the control unit 7 determines that the paper type of the current paper obtained by controlling the paper type obtaining unit 63 is not a predetermined paper type (step S53: No), the paper type obtaining unit 63 is turned on. It is determined whether or not the paper type of the previous paper acquired by control is a predetermined paper type (step S54). Specifically, it is determined whether or not the previous paper M is a type of paper that is likely to produce paper dust. Examples of the paper that easily generates paper dust include plain paper and uneven paper having a rough surface.

  When the control unit 7 determines that the paper type of the previous paper acquired by controlling the paper type acquisition unit 63 is a predetermined paper type (step S54: Yes), the paper on which no toner image is formed M (cleaning sheet) is passed through the nip portion N (step S58), and the process proceeds to step S59.

  For example, when it is determined that the previous paper M is a type of paper that is likely to generate paper dust, the paper dust adheres to the fixing roller 61a, and there is a high possibility that an image defect will occur on a wide paper. Therefore, the paper M on which no toner image is formed is passed through the nip portion N.

  Further, for example, if it is determined that the previous paper M is a type of paper that does not easily generate paper dust, paper dust is less likely to adhere to the fixing roller 61a, and image defects may occur on paper having a wide paper width. Therefore, the sheet M on which no toner image is formed can be prevented from passing through the nip portion N.

  When the control unit 7 determines that the paper type of the previous paper acquired by controlling the paper type acquisition unit 63 is not a predetermined paper type (step S54: No), the control unit 7 determines the number of sheets. It is determined whether or not the previous number of sheets acquired by controlling the acquisition unit 64 is greater than or equal to a predetermined number (step S55). The predetermined number is, for example, 500.

  If the control unit 7 determines that the previous number of sheets acquired by controlling the number acquisition unit 64 is equal to or greater than the predetermined number (step S55: Yes), the sheet M (cleaning) on which no toner image is formed (cleaning) Sheet) is passed through the nip portion N (step S58), and the process proceeds to step S59.

  For example, when the number of times of the fixing process of the previous paper M is a predetermined number or more, the amount of paper dust adhering to the fixing roller 61a increases, and there is a high possibility that an image defect will occur on a paper with a wide paper width. Therefore, the paper M on which no toner image is formed is passed through the nip portion N.

  Further, for example, when the number of previous fixing processes of the paper M is a predetermined number or less, the amount of paper dust adhering to the fixing roller 61a is small, and there is a possibility that an image defect occurs on a paper having a wide paper width. Therefore, the sheet M on which no toner image is formed can be prevented from passing through the nip portion N.

  When the control unit 7 determines that the previous number of sheets acquired by controlling the number acquisition unit 64 is not equal to or greater than the predetermined number (step S55: No), the control unit 7 determines that the image acquisition unit 65 It is determined whether or not the current image position acquired by controlling is included in the paper edge in the direction orthogonal to the transport direction of the previous paper M (step S56).

  When the control unit 7 determines that the current image position acquired by controlling the image acquisition unit 65 includes the previous paper edge (step S56: Yes), the paper M on which no toner image is formed (cleaning) Sheet) is passed through the nip portion N (step S58), and the process proceeds to step S59.

  For example, when the image position of the current paper M includes a paper edge in a direction orthogonal to the previous paper M conveyance direction, paper dust attached to the paper edge in the fixing roller 61a is transferred. As a result, there is a high possibility that an image defect will occur on a sheet having a wide sheet width.

  Further, for example, when the image position of the current paper M does not include the paper edge in the direction orthogonal to the transport direction of the previous paper M, the paper dust adhering to the paper edge in the fixing roller 61a. Even if the toner is transferred, there is no effect on the formed image, and it is unlikely that an image defect will occur on a wide paper. Therefore, the paper M on which no toner image is formed is prevented from passing through the nip portion N. be able to.

  When the control unit 7 determines that the current image position acquired by controlling the image acquisition unit 65 does not include the previous paper edge (step S56: No), the control unit 7 controls the image acquisition unit 65. It is determined whether or not the screen pattern of the current image acquired by control is a screen pattern by an error diffusion method (step S57).

  When the control unit 7 determines that the screen pattern of the current image acquired by controlling the image acquisition unit 65 is a screen pattern by the error diffusion method (step S57: Yes), the sheet on which the toner image is not formed M (cleaning sheet) is passed through the nip portion N (step S58), and the process proceeds to step S59.

  For example, when a screen pattern by the error diffusion method is formed on the current sheet M, there is a high possibility that an image defect will occur on a sheet with a wide sheet width. Let N pass.

  Further, for example, when the screen pattern by the error diffusion method is not formed on the current sheet M, it is unlikely that an image defect occurs on a sheet having a wide sheet width. It can be prevented from passing through part N.

  Finally, when the control unit 7 determines that the screen pattern of the current image acquired by controlling the image acquisition unit 65 is not a screen pattern by the error diffusion method (step S57: No), the normal fixing process is performed. The toner image transferred to the paper M is fixed (step S59).

  In the flowchart shown in FIG. 5, when it is determined that the width in the direction orthogonal to the transport direction of the current sheet M is larger than the width in the direction orthogonal to the transport direction of the previous sheet M, and five other conditions Based on the above, it is controlled whether or not the paper M on which the toner image is not formed passes through the nip portion N. Of course, not all conditions are judged, but orthogonal to the transport direction of the previous paper M. The determination may be made based on the case where it is determined that the width in the direction orthogonal to the transport direction of the current sheet M is larger than the width in the direction in which the paper M is conveyed, and at least one other condition.

  As described above, in addition to the case where the control unit 7 has a width in the direction orthogonal to the transport direction of the current sheet M larger than the width in the direction orthogonal to the transport direction of the previous sheet M, the paper type acquisition unit 63. The paper type of the current paper M acquired by the above, the paper type of the previous paper M acquired by the paper type acquisition unit 63, the number of fixing processes of the previous paper M acquired by the number acquisition unit 64, and the image acquisition unit Whether or not the paper M on which no toner image is formed passes through the nip portion N according to the image position of the current paper M acquired by 65 and the screen pattern of the current paper M by the image acquisition unit 65. By controlling, consumption of the paper M on which no toner image is formed can be suppressed.

  In the description of the embodiment, the sheet M (cleaning sheet) that removes foreign matters such as paper dust attached to the fixing roller 61a is a sheet that satisfies a predetermined condition from the sheet feeding tray units 51a to 51c by the control unit 7. For example, any one of the paper feed tray units 51a to 51c may be a paper feed tray unit dedicated to the cleaning sheet. In this case, the width of the cleaning sheet is preferably the maximum width that allows paper to pass through the image forming apparatus 100.

  Alternatively, the control unit 7 may cause the display unit 21 of the operation display unit 2 to display information that prompts execution of the cleaning sheet to be executed, and may be performed by an instruction from the operation unit 22 by the user. At that time, for example, the user may prepare a sheet different from the paper stored in the paper feed tray units 51a to 51c and pass the cleaning sheet from the manual feed tray unit 51d. Specifically, it indicates a sheet for the purpose of cleaning or a sheet that has failed printing and is unnecessary. In this case, consumption of the paper M stored in the paper feed tray units 51a to 51c can be suppressed.

(Modification 2)
In the description of the embodiment, when the control unit 7 determines that the width in the direction orthogonal to the transport direction of the current sheet M is larger than the width in the direction orthogonal to the transport direction of the previous sheet M, the toner image is Although the paper M not formed is passed through the nip portion N, the paper M used as the paper M on which the toner image is not formed may not necessarily use the paper M having a wide paper width.

  For example, when the wide paper M accommodated in the paper feed tray units 51a to 51c is expensive, or if the remaining amount is used in a small amount, it is assumed that the subsequent image forming process will be hindered. In this case, the paper M having a wide paper width cannot always be used as the paper M on which the toner image is not formed.

  In this case, the sheet M having a narrower width than the sheet M to be fixed this time is used as the cleaning sheet (the sheet on which the toner image is not formed). Foreign matter cannot be removed sufficiently.

For this reason, the control unit 7 includes a position adjustment unit 66 that adjusts the position of the sheet M, which is narrower than the sheet M to be fixed this time, in a direction orthogonal to the transport direction, and the sheet on which no toner image is formed. The position where M passes through the nip portion N is controlled to remove foreign matter adhering to the fixing member (fixing roller).
Note that the paper M on which no toner image is formed is the same as that described in the embodiment, and the passing method of the nip portion N by the control unit 7 is also the same.

  That is, as shown in the flowchart of FIG. 6, the control unit 7 controls the paper width acquisition unit 62 to acquire the paper width of the paper M on which no toner image is formed (step S61).

  Then, the control unit 7 determines whether or not the acquired paper width is wider than the previous paper width (step S62), and the acquired paper width is wider than the previous paper width. If it is determined (step S62: Yes), a sheet M (cleaning sheet) having a wide sheet width on which no toner image is formed is passed through the nip portion N (step S63).

  On the other hand, when the control unit 7 determines that the acquired paper width is not wider than the previous paper width (step S62: No), the control unit 7 determines the paper M (cleaning sheet) on which the toner image is not formed. It is determined whether or not it is allowed to pass through both ends of the sheet in the direction orthogonal to the previous transport direction of the sheet M (step S65).

  When the control unit 7 determines that the sheet M (cleaning sheet) on which the toner image is not formed passes through both the sheet end portions in the direction orthogonal to the transport direction of the previous sheet M (step S65: Yes). Then, the position adjusting unit 66 is controlled to use two sheets M (cleaning sheet) having a narrow sheet width on which no toner image is formed, and adjust the respective positions in the direction orthogonal to the transport direction. Then, the nip portion N is allowed to pass through both of the paper edge portions (step S66).

  For example, the position adjusting unit 66 is provided on the upstream side of the nip portion N, and includes a swing roller SR61 and loop rollers LR61 and LR62 as shown in FIG. The position adjusting unit 66 transports the paper M that has been transported in the direction of the arrow in FIG. 7A to a position where the swing roller SR61 is sandwiched by the loop rollers LR61 and LR62, and then the paper is conveyed by the loop rollers LR61 and LR62. The position of the paper M is adjusted by moving the paper M in the direction of the arrow in FIG. 7B in the state where the paper M is released and only the swing roller SR61 is holding the paper M.

  On the other hand, when the control unit 7 determines that it is not necessary to pass the sheet M (cleaning sheet) on which the toner image is not formed, through both the sheet end portions in the direction orthogonal to the transport direction of the previous sheet M ( Step S65: No), the position adjustment unit 66 is controlled to adjust the position of one sheet M (cleaning sheet) having a narrow sheet width on which no toner image is formed in a direction orthogonal to the transport direction, The nip portion N is passed through either one of the paper end portions (step S67).

  Finally, the control unit 7 performs a normal fixing process to fix the toner image transferred onto the paper M (step S64).

  As described above, the position adjustment unit 66 that adjusts the position in the direction orthogonal to the conveyance direction of the sheet M is provided, and the control unit 7 uses the sheet width acquisition unit 62 to form the sheet M (cleaning sheet) on which no toner image is formed. Is smaller than the width of the previous sheet M, the position adjustment unit 66 is controlled to shift the position of the sheet M (cleaning sheet) on which the toner image is not formed and is orthogonal to the transport direction of the previous sheet M. Even when the paper M having a wide paper width cannot be used as the paper M on which the toner image is not formed, the foreign matter adhering to the fixing roller is removed. can do.

  In the description of the modified example 2, when the paper M (cleaning sheet) on which the toner image is not formed is passed through both the paper end portions in the direction orthogonal to the transport direction of the previous paper M, the position adjustment unit 66, by using two sheets M (cleaning sheet) having a narrow sheet width on which no toner image is formed, the respective positions are adjusted in the direction perpendicular to the transport direction, and the end of the sheet Although the nip portion N is passed through both of the portions, the nip portion N may be passed through both ends of the paper using the front and back surfaces of one sheet M.

  In this case, since only one sheet M (cleaning sheet) on which no toner image is formed is required, consumption of the sheet M on which no toner image is formed can be suppressed.

  In the description of the embodiment, the paper M on which the toner image is not formed is passed through the nip portion N as the paper M for removing foreign matters such as paper dust attached to the fixing roller 61a. It is not necessary that the paper M is not formed. The paper M on which the toner image is not formed may be used up to the distance from the leading end portion on the downstream side in the transport direction to the circumferential length of the fixing roller 61a in contact with the toner image.

  In the description of the embodiment, the fixing device 6 includes a fixing roller 61a and a pressure roller 61b that constitute a nip portion N that sandwiches and conveys the paper M, but a heating roller that is a heating member; A fixing belt, and the fixing belt is stretched between a heating roller and a fixing roller 61a, and the fixing roller 61a and the pressure roller 61b sandwich and convey the paper M via the fixing belt. N may be configured.

  In the description of the embodiment, for example, a unit for image formation is provided for each color such as Y (yellow), M (magenta), C (cyan), K (black), and a color image is formed on the paper M. The image forming apparatus 100 to be formed is illustrated as an example, but the present invention is not limited to this. For example, an image forming apparatus that forms a monochrome image may be used.

  In the description of the embodiment, the fixing roller and the pressure roller are described separately, but may be considered as a pair of fixing members.

  In the description of the embodiment, paper is exemplified as the recording medium. However, the recording medium is not limited to paper, and may be any sheet that can form and fix a toner image. , Non-woven fabric, plastic film, leather, etc.

DESCRIPTION OF SYMBOLS 100 Image forming apparatus 4 Image forming part 6 Fixing apparatus 61 Fixing part 61a Fixing roller 61b Pressure roller 61c Outer heating roller 61d Fixing heater 61e Outer heating heater 62 Paper width acquisition part (width acquisition part)
63 Paper type acquisition unit (type acquisition unit)
64 Number acquisition unit 65 Image acquisition unit 66 Position adjustment unit 7 Control unit M Paper (recording medium)
N Nip part SR61 Swing roller LR61, LR62 Loop roller

Claims (11)

In the fixing device for fixing the toner image to the recording medium by passing the recording medium on which the toner image is formed through a nip formed by heating and pressing at least one of a pair of fixing members.
A width acquisition unit for acquiring a width in a direction perpendicular to the conveyance direction of the recording medium;
When performing the fixing process of the second recording medium after the fixing process of the first recording medium, the width of the second recording medium acquired by the width acquisition unit is larger than the width of the first recording medium. If it is determined that the toner image is not formed with the same length as the peripheral length of the fixing member on the side in contact with the toner image from the downstream end with respect to the transport direction, A control unit that allows a position where a toner image up to the same length as the circumference to be formed passes through a position corresponding to an end portion of the nip portion in a direction orthogonal to the conveyance direction of the first recording medium;
A fixing device comprising: Provided with a type acquisition unit that acquires the type of recording medium,
The control unit is configured such that the width of the second recording medium acquired by the width acquisition unit is larger than the width of the first recording medium, and the second recording medium acquired by the type acquisition unit The fixing device according to claim 1, wherein when it is determined that the type is a predetermined type, the third recording medium is passed. Provided with a type acquisition unit that acquires the type of recording medium,
The control unit is configured such that a width of the second recording medium acquired by the width acquisition unit is larger than a width of the first recording medium, and the first recording medium acquired by the type acquisition unit 3. The fixing device according to claim 1, wherein when the type is determined to be a predetermined type, the third recording medium is passed. A number acquisition unit for acquiring the number of fixing processes of the recording medium;
The control unit fixes the first recording medium acquired by the number acquisition unit when the width of the second recording medium acquired by the width acquisition unit is larger than the width of the first recording medium. 4. The fixing device according to claim 1, wherein when it is determined that the number of processed sheets is equal to or greater than a predetermined number, the third recording medium is allowed to pass. 5. An image acquisition unit for acquiring the position of an image formed on a recording medium;
The control unit is configured such that a width of the second recording medium acquired by the width acquisition unit is larger than a width of the first recording medium, and the second recording medium acquired by the image acquisition unit 5. The method according to claim 1, wherein the third recording medium is allowed to pass when it is determined that the position of the image includes an end position in a direction orthogonal to the conveyance direction of the first recording medium. The fixing device according to claim 1. An image acquisition unit that acquires information on screen processing of an image formed on a recording medium;
The control unit is configured such that the width of the second recording medium acquired by the width acquisition unit is larger than the width of the first recording medium, and the screen processing acquired by the image acquisition unit is based on an error diffusion method. 6. The fixing device according to claim 1, wherein when the screen processing is determined, the third recording medium is allowed to pass. A position adjusting unit for adjusting a position in a direction perpendicular to the conveyance direction of the recording medium;
When the control unit determines that the width of the third recording medium acquired by the width acquisition unit is smaller than the width of the first recording medium, the control unit controls the position adjustment unit to perform the third recording medium. 7. The fixing device according to claim 1, wherein the position of the medium is adjusted so as to pass through an end portion in a direction orthogonal to a conveyance direction of the first recording medium. .   The said control part controls the said position adjustment part, The said 3rd recording medium is allowed to pass through the said nip part so that either one side of the said edge part may be passed. Fixing device.   The control unit controls the position adjusting unit so that at least one of the plurality of third recording media passes through one side of the end and at least one passes through the other side of the end. The fixing device according to claim 7, wherein the fixing device is passed through the nip portion.   The control unit controls the position adjusting unit to pass the third recording medium through the nip portion so that the surface of the third recording medium passes through one side of the end portion and the back surface passes through the other side of the end portion. The fixing device according to claim 7. An image forming unit for forming a toner image on a recording medium;
An image forming apparatus comprising: the fixing device according to claim 1, wherein the toner image is fixed to the recording medium through the recording medium on which the toner image is formed. .

Images