JP2009175601A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress image a defect such as an offset caused by the contamination of a film by automatically removing the contamination of the non-paper passing portion of a fixing film caused by the printing of small-size paper etc. <P>SOLUTION: The image forming apparatus includes: a fixing device holding and conveying a recording material carrying an image to thermally fix it in a nip formed of a heating device arranged on a recording material conveying path and a pressure member brought into contact with the heating device through the fixing film and rotated, and a control means controlling an image forming operation. When the number of passed recording materials whose widths are smaller than the maximum paper passing width reaches a predetermined number (Yes in S2), the control means allows a fixing film cleaning sheet whose width is the maximum paper passing width or near the maximum paper passing width to pass through the fixing device (S5). <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic recording apparatus having a pressure heating fixing mechanism for fixing an unfixed image on a recording material as a permanent image by pressurizing and heating, and an image forming apparatus such as an electrophotographic copying machine and a printer, particularly a fixing film thereof. It is about removal of dirt.

  Conventionally, in an image forming apparatus such as a copying machine or a laser printer that forms an image on a recording material using an electrophotographic process method, a rotating drum type photosensitive member (hereinafter referred to as a “photosensitive drum”) as an image carrier. The developer image (toner image) carried by the toner is transferred onto the recording material by a transfer means. Then, the recording material is introduced into the fixing device, and heated and pressed while being nipped and conveyed at the nip portion between the fixing rotating members as rotating bodies, whereby the developer image is heated and fixed on the recording material.

As the above-mentioned fixing device, a heat roller heating method or a film heating method is known.
The fixing device of the film heat fixing method uses a heater (heating body) such as ceramic and a flexible thin layer film such as polyimide or SUS instead of the halogen heater and the fixing roller in the heat roller heating method to increase the heat capacity. It is small. This enables quick start and power saving.
Flexible thin film as a fixing film has a small heat capacity and good temperature responsiveness, so there is no need to preheat the fixing film, and only when it is introduced into the nip of the recording material (hereinafter referred to as “when passing paper”) It became possible to energize the heater.

In the fixing process described above, a part of the toner on the recording material adheres to the fixing film. Further, a part of the toner scattered in the image forming apparatus adheres to the fixing film. In addition, paper dust released from the paper that is the recording material adheres to the fixing film, so that the surface of the fixing film becomes dirty (hereinafter, this phenomenon is referred to as “film contamination”), and the releasability of the dirty portion of the film is reduced. This causes image defects such as offset. In order to avoid adhesion of toner and paper powder on the fixing film, a technique for improving the releasability of the fixing film (Patent Document 1) and a technique for applying a bias having the same polarity as the toner to the fixing film (Patent Document 2) Etc. have been proposed.
JP-A-11-249463 Japanese Patent Laid-Open No. 9-80832

  Even in the image forming apparatus in which the above-described measures are taken, a recording material having a width smaller than the maximum sheet passing width of the image forming apparatus (hereinafter referred to as “small size”), for example, the B5 size in the image forming apparatus corresponding to the LTR width. When about 1,000 sheets of the following recording material are passed, film contamination occurs in a portion where the recording material does not pass (hereinafter, this portion is referred to as a “non-sheet passing portion”), causing image defects such as offset. There is. The above-mentioned film contamination is caused by scattering toner and paper powder from the transfer portion adhering to the fixing film.

  In the paper passing portion, the toner adhering to the fixing film moves to the recording material every time the recording material passes and does not remain on the surface of the fixing film. However, since the recording material does not pass through the non-sheet-passing portion, the toner adhering to the surface of the fixing film adheres to the surface of the fixing film as it is, becomes film stain, and causes image defects such as offset in the non-sheet-passing portion.

  The present invention has been made under such circumstances, and it automatically removes stains on the non-sheet passing portion of the fixing film caused by small size printing and the like, such as offset caused by film stains. It is an object to provide an image forming apparatus capable of suppressing image defects.

  In order to solve the above-described problems, in the present invention, an image forming apparatus is configured as described in (1) below.

(1) A recording material carrying an image is nipped and conveyed in a nip portion formed by a heating device arranged in a recording material conveyance path and a pressure member rotating in contact with the heating device via a fixing film. In an image forming apparatus provided with a fixing device for heat fixing and a control means for controlling an image forming operation,
The control means passes a fixing film cleaning sheet having a maximum sheet passing width or a sheet width close to the maximum sheet passing width to the fixing device when the number of sheets having a recording width smaller than the maximum sheet passing width reaches a predetermined number. An image forming apparatus for paper.

  According to the present invention, by removing the toner on the fixing film with the fixing film cleaning sheet, it is possible to avoid image defects caused by the toner adhering to the fixing film. In addition, since the fixing film cleaning process is automatically performed, it is possible to improve without impairing usability.

  Hereinafter, the best mode for carrying out the present invention will be described by way of examples. Each embodiment is an example of a laser printer, but the present invention can be applied to an appropriate type of image forming apparatus. Further, the fixing device in the embodiment is only an example, and the present invention can be applied to an image forming apparatus including an appropriate fixing device having a fixing film.

  An “image forming apparatus” that is Embodiment 1 will be described. In this embodiment, removal of dirt on a non-sheet passing portion of a fixing film that occurs when a small size sheet is passed will be described.

First, the configuration of the entire image forming apparatus of the present embodiment and the image forming process will be described.
FIG. 1 is an overall configuration diagram of the image forming apparatus according to the present exemplary embodiment. The image forming apparatus of this embodiment is a laser printer using an electrophotographic process method.
The image forming apparatus shown in FIG. 1 includes a photosensitive drum 1 as an image carrier. The photosensitive drum 1 is rotationally driven at a predetermined process speed in a clockwise direction indicated by an arrow by a main body drive motor 12 as an image carrier driving means.
Around the photosensitive drum 1, the charging roller 2, the exposure device 3, the developing device 4, the transfer roller (transfer member) 5 as the transfer device, and the cleaning device 6 are sequentially cleaned along the rotation direction. A blade 6 is arranged.
In addition, a paper feed cassette 7 that stores a recording material P such as paper is disposed at the lower part of the apparatus main body. Then, in order along the conveyance path of the recording material P (corresponding to the recording material conveyance path in the claims), the paper feed roller 15, the conveyance roller 8, the top sensor 9, the photosensitive drum 1 and the transfer roller 5, the conveyance guide 10, A fixing device 11, a paper discharge roller 13, and a paper discharge tray 14 are disposed.

The operation of the image forming apparatus configured as described above will be described.
The image forming process speed of the image forming apparatus is 200 mm / sec, and the recording material is conveyed at 200 mm / sec.
The photosensitive drum 1 that is rotationally driven in the direction of the arrow by the main body drive motor 12 is uniformly charged to a predetermined polarity and a predetermined potential by the charging roller 2. The photosensitive drum 1 after charging is exposed L based on image information by an exposure device (laser scanner) 3 of a laser optical system on the outer peripheral surface of the drum. That is, the exposure device 3 exposes the uniformly charged surface treated surface of the photosensitive drum 1 with the laser beam L that is ON / OFF controlled according to the time-series electric digital image signal of the image information. By this exposure L, the exposed portion potential of the uniformly charged surface of the photosensitive drum 1 is attenuated, and an electrostatic latent image corresponding to the image information is formed on the outer peripheral surface of the photosensitive drum. The electrostatic latent image is developed by the developing device 4. The developing device 4 includes a developing roller 4a. A developing bias is applied to the developing roller 4a to attach toner to the electrostatic latent image on the photosensitive drum 1 and develop (develop) it as a toner image.

  The recording material P stored in the paper feed cassette 7 is fed by the paper feed roller 15, and is transported to the transfer nip T between the photosensitive drum 1 and the transfer roller 5 by the transport roller 8. Before the recording material P is conveyed to the transfer nip T, the leading edge of the recording material P is detected by the top sensor 9 provided between the conveyance roller 8 and the transfer nip T, and the recording material P is synchronized with the toner image on the photosensitive drum 1. It is done. A transfer bias is applied to the transfer roller 5, and the toner image on the photosensitive drum 1 is transferred onto the recording material P.

The recording material P carrying the unfixed toner image in the transfer process is transported to the fixing device 11 along the transport guide 10, and is heated and pressed to make the unfixed toner image as a permanently fixed image on the recording material P. It is fixed.
The recording material P after the toner image is fixed is discharged onto a discharge tray 14 on the upper surface of the apparatus main body by a discharge roller 13.

After the toner image is transferred, the toner remaining on the surface without being transferred to the recording material P is removed by a cleaning blade (not shown) of the cleaning device 6 and the next image formation is performed.
By repeating the above operation, image formation can be performed one after another (corresponding to the image formation operation in the claims).

Next, the fixing device 11 will be described in detail.
FIG. 2 is a sectional view of the fixing device 11, and FIG. 3 is an enlarged sectional view of a fixing nip portion. The fixing device shown in this embodiment is a film fixing type device using a cylindrical fixing film.
The fixing device 11 includes a fixing rotating body (hereinafter, referred to as “fixing film”) 25 that is a cylindrical flexible film as a rotating body that forms a fixing nip portion N in contact with each other, and a roller-shaped pressurizing member. A rotating body (hereinafter referred to as a “pressure roller”, which corresponds to a pressure member in the claims) 26. A ceramic heater (hereinafter referred to as a “heater”) 20 as a heating element that heats the unfixed toner image t on the recording material P via the fixing film 25; a temperature control means 27 that controls the temperature of the heater 20; And a fixing motor 29 as a rotating body driving means.

  The heater 20 is a resistance heating element. As shown in FIG. 3, the heater 20 generates heat when energized on a highly heat conductive / insulating / heat resistant substrate 20a such as alumina. For example, a resistor pattern (resistance layer) such as Ag / Pd. ) 20b is formed by printing. And the surface of the heater 20 is coat | covered with the glass layer 20c as a surface protective layer. The heater 20 is formed in an elongated shape in the longitudinal direction (width direction of the fixing film) perpendicular to (crossing) the conveyance direction Y of the recording material P, that is, in the width direction of the recording material P, and from the width dimension of the recording material P Is also long. The heater 20 is supported on the lower surface of the heater holder 22 disposed in the hollow portion of the fixing film 25 with the resistor pattern 20b facing downward. The heater holder 22 is a member having a shape elongated in the longitudinal direction by a heat-resistant resin, and the back surface of the fixing film 25 is guided by two left and right arc portions 22a and 22a. The heater holder 22 not only functions as a support member that supports the heater 20 but also functions as a guide member that guides the rotation of the fixing film 25.

  The fixing film 25 has a small heat capacity and is formed of a heat-resistant resin such as polyimide in a cylindrical shape, and a release layer 25a such as a fluororesin is provided on the surface. More specifically, the fixing film 25 has a base layer (about 50 μm) made of polyimide (PI) and a release layer (about 12 μm) 25a made of fluororesin (PEA, PTFE, etc.) on the surface, A primer layer having a role of connecting two layers with the release layer is provided. The fixing film 25 composed of the base layer, the primer layer, and the release layer has a thickness of about 70 μm, and the heater 20 and the heater holder 22 are provided in the hollow portion. The fixing film 25 is pressed against the heater 20 by the elasticity of the pressure roller 26, and the surface of the fixing film 25 that contacts the heater is in contact with the lower surface of the heater 20.

  The pressure stay 31 is a U-shaped rigid pressure stay with a downward vertical cross section made of metal, and is attached to the side without the heater between the arc portions 22 a and 22 a of the heater holder 22 in the fixing film 25. The pressure stay 31 is a member elongated in the longitudinal direction, and both ends thereof are supported by a device chassis side plate (not shown) via a pressure spring. The pressure stay 31 uniformly transmits the pressure applied by the pressure spring to the heater 20 via the heater holder 22, and the fixing film 25 is sandwiched between the heater 20 and the pressure roller 26 to determine the position on the recording material P. A fixing nip portion N having a predetermined width necessary for heating and fixing the received toner image t is formed.

The fixing film 25 is conveyed by a predetermined peripheral speed, that is, from the transfer nip T, while being in close contact with and sliding on the lower surface of the heater 20 in the clockwise direction by the rotation driving of the pressure roller 26 at least when the unfixed toner image is fixed. The recording material P is rotationally driven without wrinkles at substantially the same peripheral speed as the conveyance speed of the recording material P to come.
The pressure roller 26 has a heat-resistant elastic layer 26b having elasticity such as silicone rubber on the surface of the metal core 26a, and a release layer 26c made of fluororesin or the like on the surface layer. ing. More specifically, the pressure roller 26 has a diameter of 25 mm, the rubber thickness of the elastic layer 26b is 3.5 mm, and the fixing nip portion N has a width of 8 mm.
The pressure roller 26 is arranged in parallel with the fixing film 25, and both ends of the cored bar 26a are rotatably supported by a device chassis side plate (not shown).

  The pressure roller 26 is rotated by a fixing motor 29 in a counterclockwise direction indicated by an arrow at a predetermined peripheral speed. When the pressure roller 26 is driven to rotate, a rotational force acts on the sleeve-like fixing film 25 by a pressure frictional force at the fixing nip N between the pressure roller 26 and the surface of the fixing film 25 that does not contact the heater. By the rotation driving described above, the fixing film 25 is driven to rotate in the clockwise direction indicated by the arrow on the outer periphery of the heater holder 22 while the surface in contact with the heater slides on the lower surface of the heater 20.

The temperature control means 27 includes a thermistor 21 that is a temperature detection means attached to a surface of the heater 20 that is not in contact with the fixing film, and an energization control circuit unit 23 that includes a CPU and a memory such as a ROM and a RAM.
The energization control circuit unit 23 controls the bidirectional three-terminal thyristor 24 to energize the resistor pattern 20 b of the heater 20 from the AC power supply 28. The heater 20 is heated by energization, and the thermistor 21 detects the heater temperature at that time. The energization control circuit unit 23 takes in the detected temperature of the heater 20 from the thermistor 21, controls the bidirectional three-terminal thyristor 24 based on the detected temperature, and controls the energization amount from the AC power source 28 to the heater resistor pattern 20b. To do. As a result, the temperature of the heater 20 is maintained at a predetermined fixing temperature (target temperature).

In a state where the heater 20 is heated to the fixing temperature and the pressure roller 26 is rotationally driven, the recording material P is introduced into the fixing nip portion N from the leading end, whereby the recording material P is fixed to the fixing film at the fixing nip portion N. 25 and the pressure roller 26. During the conveyance process, the heater 20 heats the unfixed toner image t through the fixing film 25 to heat and press-fix the toner image t on the surface of the recording material P.
After completion of the fixing process, the recording material P passes through the fixing nip portion N and is separated from the fixing film 25 and discharged.

The fixing film cleaning operation in this embodiment will be described.
The image forming apparatus according to the present exemplary embodiment has a fixing film cleaning operation for removing dirt attached to the fixing film 25 of the fixing device 11 in addition to the normal printing operation described above. The fixing film cleaning operation is automatically performed when a certain condition is satisfied, and stains attached to the fixing film are removed to reduce image defects.

In the above-described fixing film cleaning operation, a fixing film cleaning paper (corresponding to a fixing film cleaning sheet in the claims) is used. As the fixing film cleaning paper, the maximum sheet passing width of the image forming apparatus or a size close to the maximum sheet passing width is used. By letting the fixing device 11 pass paper for cleaning the fixing film, the dirt attached to the fixing film 25 due to friction with the surface of the paper that has been passed through is peeled off and attached to the paper for cleaning the fixing film. As a result, the fixing film 25 is cleaned.
The effect of removing dirt adhering to the fixing film 25 is higher when the toner is on the fixing film cleaning paper. The reason why the effect is further increased is that the toner melted in the fixing nip N acts like an adhesive, and the dirt on the fixing film is adhered to the paper for cleaning the fixing film. Therefore, a pattern such as a horizontal line, halftone, or solid black may be printed on the paper for cleaning the fixing film (corresponding to a sheet on which a pattern is printed in the claims).

In the case where there are a plurality of places for setting recording materials (the paper feed cassette 7 and the multi paper feed tray 33) as in the image forming apparatus of this embodiment, many users often use LTR and A4 size frequently used for the paper feed cassette 7. In many cases, paper having a size close to the maximum sheet passing width is set, and small-size paper (A5, EXE, postcard, envelope, etc.) with low use frequency is set in the multi-feed tray 33 and used.
In addition, it can be easily predicted that a situation in which small-size paper is collectively printed continuously, such as printing on a guide letter or New Year's card, will frequently occur. When small-size paper is continuously printed, film fouling due to adhesion of scattered toner or the like occurs in the non-sheet-passing area where the recording material does not pass through the fixing film 25.

The fixing film cleaning operation in the present embodiment for the purpose of reducing the film contamination caused by the continuous passage of the small size paper as described above will be described.
The fixing film cleaning operation is performed by the control device 30 (FIG. 1) as a control means. The control device 30 includes a CPU and a memory such as a ROM and a RAM. Various programs necessary for executing the fixing film cleaning operation are recorded in the memory, and the CPU executes the fixing film cleaning operation according to the various programs.

The fixing film cleaning operation will be described with reference to the flowchart of FIG.
When a print signal is received from the outside in the standby state (see step 1 (hereinafter referred to as S1)), a small size count number (corresponding to the number of sheets passed in the claims) is confirmed. When the small size count is n = 10 (“Yes” in S2, equivalent to when the predetermined number of sheets, the predetermined number of sheets passed in the claims, the number of sheets printed on the former recording material reaches the predetermined number) Then, it is determined whether the received print signal is a small size print (S3). When the print signal is a small size (“Yes” in S3), the small size print signal is printed (S4, corresponding to the former recording material in the claims), and then the paper for cleaning the fixing film is automatically passed. Paper is made (S5). After the fixing film cleaning paper is passed, the small size count is reset and n = 0 (S6). When the small size count is reset, the job ends (S11).

  If the small size count is not n = 10 (“No” in S2), it is determined whether the received print signal is a small size print (S7). When the print signal is a small size (“Yes” in S7), the small size print signal is printed (S8), and then the small size count is incremented by “1” (S9).

  With the addition of the small size count, the job ends (S11).

  If the received signal is not a small size print (“No” in S3 or S7), the received signal is executed (S10). With the execution of the received signal, the job ends (S11).

  As the paper for cleaning the fixing film, paper having a maximum sheet passing width or a size close to the maximum sheet passing width is used. By using paper of the maximum paper passing width or a size close to the maximum paper passing width, cleaning paper passes through the edge of the fixing film, which was the non-passing area when printing small size paper. Dirt can be removed. Since the paper with the maximum paper passing width or the size close to the maximum paper passing width is usually set in the paper feed cassette 7, the user prepares the paper with the maximum paper passing width or the size close to the maximum paper passing width and passes the paper again. There is little need to direct.

  In S10, the fixing film cleaning sheet is passed through the first sheet (corresponding to the first sheet when printing on the latter recording material in the claims), and then a print other than a small size (claim) (Corresponding to the latter recording material). By doing in this way, the film stain | pollution | contamination in printing other than small size can be reduced more.

  As described above, according to the present embodiment, the film contamination in the non-sheet passing portion region attached by the printing of the small size paper can be reduced without bothering the user, and the film contamination occurs. Image defects can be suppressed.

An “image forming apparatus” that is Embodiment 2 will be described. In the present embodiment, in the image forming apparatus in which the sheet passing position of the recording material is used as the center reference, the paper is not placed at the center that is the original sheet passing area without using the restriction plate of the sheet feeding port, and from the left or right end. The removal of film stains in the non-sheet-passing portion that occurs when the sheets are fed together (hereinafter, this state is referred to as “one-sided feeding”) will be described.
Since the hardware configuration of the image forming apparatus of the present embodiment is the same as that of the first embodiment, the description thereof will be omitted.

As a configuration unique to the present embodiment, a sensor (hereinafter referred to as a “flag”) as a sheet passing detection means is provided in the sheet passing area in the image forming apparatus, and the information in the flag is used in the sheet passing area of the recording material. The position in the longitudinal direction (direction perpendicular to the sheet passing direction on the plane on the recording material) can be detected. Therefore, it is possible to detect the misalignment of the recording material.
The fixing film cleaning operation in this embodiment will be described with reference to the flowchart of FIG.
When a print signal is received from the outside in the standby state (S51), the shift count number is confirmed. When the shift count number is n = 10 (“Yes” in S52), the received signal is printed (S53). Subsequently, the fixing film cleaning paper is automatically passed (S54). After the fixing film cleaning paper is passed, the misalignment count is reset and n = 0 (S55). The job is terminated (S59) when the misalignment count is reset.

If the misalignment count is not n = 10 (“No” in S52), the received signal is printed (S56). It is determined based on the information from the flag whether the received signal print is justified (S57). If the print is justified (“Yes” in S57), the justification count is incremented by “1” (S58). The job is completed (S59) when the shift count is added.
If the print is not justified (“No” in S7), the job ends (S9).

  By the way, when there are a plurality of places (recording cassette 7 and multi-feed tray 33) where the recording material is set as in the image forming apparatus according to the present embodiment, many users use the sheet feeding cassette 7 (second claim in the claims). LTR or A4 size large-size paper that is frequently used is set in the paper feed unit), and small-size paper (A5, EXE, postcard, envelope, etc.) that is not frequently used is loaded into the multi-feed tray 33 (in the claims) It is often used by being set in the first paper feed unit.

  When setting the paper in the multi-feed tray 33, some users may set the paper close to either the right or left edge instead of the original paper passing area without using the paper regulating plate. is there. When a print job is performed with the paper close to either the left or right edge, the paper passes through a location outside the original paper passing area, and what is the non-paper passing part when the original paper passing area is passed? A different part becomes a non-sheet passing part. The temperature of the non-sheet passing portion when the paper is just fed is higher than the temperature of the non-paper passing portion when the paper is passed at the normal position. The toner adhering to the top tends to adhere more firmly to the fixing film. As a result, if the sheet is continuously fed, the non-sheet passing portion of the sheet is caused to be smudged by scattered toner or the like, causing image defects.

  As the paper for cleaning the fixing film, paper having a maximum sheet passing width or a size close to the maximum sheet passing width is used. By using paper of the maximum sheet passing width or a size close to the maximum sheet passing width, the paper also passes through the fixing film edge, which was a non-passing part when one-sided passing, so the stains on the non-passing part are removed. be able to. Since the paper having the maximum paper passing width or the size close to the maximum paper passing width is usually set in the paper feeding cassette 7, it is almost unnecessary for the user to prepare again.

  The fixing film cleaning paper may be white paper, but in order to improve the cleaning effect, an image such as a horizontal line, halftone, solid black, etc. may be printed on the entire surface or only on a non-sheet passing portion of small size paper. This is because the fixing film cleaning paper having a certain amount of toner has a greater effect of removing dirt on the fixing film.

  In this way, in the present embodiment, the film contamination in the non-sheet passing portion area that is attached by printing with the side-by-side passing paper can be reduced without bothering the user's hand, and occurs along with the film contamination. Image defects can be suppressed.

An “image forming apparatus” that is Embodiment 3 will be described. In this embodiment, a small image forming apparatus having only one paper feed port (corresponding to only one paper feed unit in the claims) reduces film contamination in a non-sheet passing portion that occurs during small size printing. Will be described.
FIG. 6 is an overall configuration diagram of the image forming apparatus according to the present exemplary embodiment.
Main parts related to image formation include a paper feed roller 34, a photosensitive drum 35, a transfer roller 36, a charging roller 37 as a charging device, an exposure device 38, a developing device 39, a pressure roller 40, and a heating unit 41. There is a paper feed port 43 for setting the recording material P at the bottom of the main body. The pressure roller 40 and the heating unit 41 constitute a fixing device 42.
Since the detailed image forming process is the same as that of the first embodiment, the description thereof is omitted.

The fixing film cleaning operation in this embodiment will be described with reference to the flowchart of FIG.
When the print signal (S101) is received from the outside in the standby state, the small size count is confirmed. When the small size count is n = 10 (“Yes” in S102), it is determined whether the received print signal is a small size print (S103). When the print signal is a small size (“Yes” in S103), the small size print signal is printed (S104), and the job is ended (S112). When the print signal is not a small size (“No” in S103), the print signal is executed (S105), and then the fixing film cleaning paper is passed (S106). After the fixing film cleaning paper is passed, the small size count is reset and n = 0 (S107). When the small size count is reset, the job ends (S112).
If the small size count is not n = 10 (“No” in S102), it is determined whether the received print signal is a small size print (S108). If the print signal is a small size (“Yes” in S108), the small size print signal is printed (S109), and then the small size count is incremented by “1” (S110). With the addition of the small size count, the job ends (S112).

  If the received signal is not a small size print (“No” in S108), the received signal is executed (S111), and the job ends (S112).

  The actual fixing film cleaning operation is performed when the next large-size paper printing operation is received. In a small-sized machine, there is almost no paper feed port in most cases, so there is no paper of a size close to the maximum paper passing width at the paper feed port during small size printing. Therefore, even when the counter reaches n = 10 during the small size printing, the printing operation of the small size paper is continued as it is. When the next printing operation for paper having a size close to the maximum sheet passing width is received, the fixing film cleaning operation is performed. Fixing film dirt is removed by fixing film cleaning operation, and image defects can be reduced.

  In this fixing film cleaning operation, paper having a maximum sheet passing width or a size close to the maximum sheet passing width is used. As a result, the paper passes through the edge of the fixing film, which was a non-sheet passing portion when printing small-size paper, so that the stain on the non-sheet passing portion can be removed. The fixing film cleaning paper may be white paper. In order to further improve the cleaning effect, an image such as a horizontal line, a halftone, or a solid black may be printed on the entire surface or only on a non-sheet passing portion of small size paper. This is because the fixing film cleaning paper having a certain amount of toner has a greater effect of removing dirt on the fixing film.

  In this way, in this embodiment, for a small-sized image forming apparatus having only one paper feeding port, fixing film stains in the non-sheet passing portion that occur during small size printing are reduced while minimizing the burden on the user. can do.

Sectional drawing which shows schematic structure of the image forming apparatus which is Example 1. FIG. Sectional drawing which shows schematic structure of the fixing apparatus used in Example 1. FIG. 2 is an enlarged view of the nip portion of the fixing device shown in FIG. Flowchart of cleaning operation in embodiment 1 Flowchart of cleaning operation in embodiment 2 Sectional drawing which shows schematic structure of the image forming apparatus which is Example 3. FIG. Flowchart of cleaning operation in embodiment 3

Explanation of symbols

11 Fixing device 20 Ceramic heater 25 Fixing film 26 Pressure roller 30 Control device N Nip part P Recording material

Claims (6)

A recording material carrying an image is nipped and conveyed to be fixed by heating at a nip formed by a heating device disposed in the recording material conveyance path and a pressure member that contacts and rotates with the heating device via a fixing film. In an image forming apparatus including a fixing device and a control unit that controls an image forming operation,
The control means passes a fixing film cleaning sheet having a maximum sheet passing width or a sheet width close to the maximum sheet passing width to the fixing device when the number of sheets having a recording width smaller than the maximum sheet passing width reaches a predetermined number. An image forming apparatus characterized by causing paper to form. The image forming apparatus according to claim 1,
A first paper feed unit and a second paper feed unit;
The control means causes the fixing sheet cleaning sheet to pass from the second paper feeding unit when a predetermined number of recording materials having a paper width smaller than the maximum paper feeding width have passed from the first paper feeding unit. An image forming apparatus. The image forming apparatus according to claim 1,
With only one paper feeder,
The control means causes the fixing film cleaning sheet to pass through from the paper feeding unit when a predetermined number of recording materials having a paper width smaller than the maximum paper passing width have passed from the paper feeding unit. Forming equipment. The image forming apparatus according to claim 2 or 3,
When the recording material having the maximum paper passing width or the paper width close to the maximum paper passing width is printed after printing on the recording material having a paper width smaller than the maximum paper passing width, the control means sets the number of prints on the former recording material to a predetermined value. The fixing film cleaning sheet is passed through the first sheet when printing on the latter recording material. The image forming apparatus according to claim 1,
The image forming apparatus, wherein the fixing film cleaning sheet is a white paper. The image forming apparatus according to claim 1,
The image forming apparatus, wherein the fixing film cleaning sheet is a sheet on which a pattern is printed.

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