JP2009020407A - Fixing device and image forming apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device capable of surely removing toner adhering to the surface of a fixing roller and to provide an image forming apparatus using the fixing device. <P>SOLUTION: A fixing unit 27 is provided with: the fixing roller 27A which fixes a toner image on a sheet formed with an unfixed toner image, in such a manner that the sheet passes through a nip portion 127 where a heating roller 123 and a pressure roller 124 are in press-contact with each other; and a cleaning unit 131 having a function of bringing a web sheet 133 into contact with the heating roller 123, to clean the surface of the roller and periodically winding a portion used for cleaning the heating roller 123, In the fixing unit 27, after completing fixing processing or before performing fixing processing, the web sheet 133 is brought into contact with the heating roller 123 and wound for a predetermined time. When the web sheet 133 is wound, the heating roller 123 is rotated in a direction reverse to the moving direction of the web sheet 133. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fixing device and an image forming apparatus using the fixing device, and more particularly, a fixing device including a web cleaning type cleaning unit that presses a web member against an outer peripheral surface of a rotating roller member to clean the surface of the roller body. The present invention relates to an image forming apparatus and an image forming apparatus for outputting an image by fixing a toner image on a recording medium by the fixing device.

  2. Description of the Related Art Conventionally, in an image forming apparatus such as a facsimile or printer using an electrophotographic method, a photosensitive drum that is rotationally driven is charged by a charger, and an electrostatic latent image is formed on the photosensitive drum by light irradiation according to image information. Then, a toner image is formed by attaching toner to the electrostatic latent image by a developing device, and the toner image is transferred to a recording medium such as a sheet material or paper to output an image.

  In this image forming apparatus, a fixing device for fusing and fixing unfixed toner on a recording medium to be conveyed is disposed, and a pair of rollers including a heating roller and a pressure roller at a portion for melting and fixing the unfixed toner A heat fixing roller system in which a member is used and heat is applied to the toner on the recording medium in the pressure contact area (fixing nip portion) of both rollers to fix the toner onto the recording medium is often used.

  In the fixing device configured as described above, the unfixed toner is melted and fixed at the fixing nip portion by the heating roller and the pressure roller, but all toner is fixed on the recording medium during the fixing process. However, it is difficult to say that a part of the toner is in a molten state and attached to the surface of the heating roller, and rotates together with the heating roller. When the next printing process is performed in this state, there arises a problem that the back side of the paper and the printing stain are caused.

Therefore, as a mechanism for reducing the toner remaining on the surface of the heating roller, a so-called cleaning web type cleaning device is known in which a web member is pressed against the heating roller to clean the roller surface.
For example, as a conventional technique, a cleaning device is proposed that removes residual toner on the surface of the heating roller by pressing a cleaning unit (for example, a web member) against the heating roller after the fixing process is completed, rotating it for a predetermined time, and then stopping. (Patent Document 1).
JP-A-2-284184

  However, in a cleaning device mechanism using a conventional web cleaning technique, residual toner that has not been removed by the cleaning means (cleaning web) may adhere to the surface of the heating roller at the end of the fixing process (stop of the heating roller). is there. When the printing operation is resumed, the surface of the residual toner is moved by the rotation of the heating roller, and when the printing is finished, if the toner remains in the cleaning nip portion, the residual toner is solidified on the surface of the heating roller. The solidified toner adheres to the recording medium and is output in the next transfer process, resulting in a problem of paper smearing.

  The present invention has been made in view of the above-described conventional problems, and provides a fixing device that can reliably remove toner adhering to the surface of a fixing roller and an image forming apparatus using the same. Objective.

The configurations of the fixing device according to the present invention and the image forming apparatus using the same for solving the above-described problems are as follows.
The fixing device according to claim 1 includes a pair of roller members each having at least one roller member provided with a heat generating unit, and a recording in which an unfixed toner image is formed in a nip portion where the roller members are pressed against each other. A fixing roller that melts the toner image by passing the medium and fixes the toner image on the recording medium, and a web member that contacts the outer peripheral surface of the rotating fixing roller to clean the roller surface, and cleaning the fixing roller In a fixing device having a cleaning mechanism having a function of periodically winding a portion used for the recording medium, after the fixing process of the toner image onto the recording medium by the fixing roller is completed, or the recording medium by the fixing roller Before the toner image is fixed to the web, the web member is brought into contact with the fixing roller and wound up for a predetermined time; When taking came, it is characterized in that it has a, a function of rotating such that the direction opposite to the moving direction of the web member at a contact portion between said web member the fixing roller.

  According to a second aspect of the present invention, in addition to the configuration described in the first aspect, the fixing device includes a sheet number counting unit that detects the number of sheets to be fixed, and the number of fixing process has reached a predetermined number or more by the sheet number counting unit. When detected, the web member is wound up.

  According to a third aspect of the present invention, in addition to the configuration described in the first or second aspect, the fixing device includes a printing rate calculation unit that calculates a printing rate of a surface to be printed on the recording medium, and is calculated by the printing rate calculation unit. The web member winding operation is performed when the printed printing rate has reached a predetermined value or more set in advance.

  According to a fourth aspect of the present invention, in addition to the configuration described in the third aspect, when the printing rate calculated by the printing rate calculation means reaches 80% or more, the web member is wound up. Is executed.

  According to a fifth aspect of the present invention, there is provided an image forming apparatus comprising: a photosensitive drum on which an electrostatic latent image is formed and a toner image is formed based on the electrostatic latent image; and toner on the photosensitive drum. A developing unit having a developing roller to be supplied; a transfer unit for transferring a toner image formed on the photosensitive drum to a conveyed recording medium; and at least one roller member having a heating unit. A fixing unit that melts the toner image and fixes the toner image on the recording medium by passing a recording medium on which an unfixed toner image is formed through a nip portion where the roller members are pressed against each other. A fixing device having a roller and a cleaning mechanism that cleans the roller surface by bringing a web member into contact with the outer peripheral surface of the rotating fixing roller, and is formed on the surface of the photosensitive drum by electrophotography. In the image forming apparatus to output the transferred toner image on the recording medium, as the fixing device, it is characterized in the use of the fixing device according to any one of claims 1 to 4.

  According to the first aspect of the present invention, at least one roller member is provided with a pair of roller members provided with heat generating means, and an unfixed toner image is formed at a nip portion where the roller members are pressed against each other. A fixing roller that melts the toner image by passing the recording medium and fixes the toner image on the recording medium; and a web member that contacts the outer peripheral surface of the rotating fixing roller to clean the roller surface; In the fixing device having a cleaning mechanism having a function of periodically winding a portion used for cleaning, after the fixing process of the toner image onto the recording medium by the fixing roller is completed, or the recording by the fixing roller. A function of bringing the web member into contact with the fixing roller and winding it for a predetermined time before the toner image is fixed to the medium; A function of rotating the fixing roller so as to be in a direction opposite to the moving direction of the web member at the contact portion with the web member at the time of winding, so that at the end of printing (stop of the heating roller) The remaining toner adhering to the surface of the fixing roller is surely removed by cleaning the portion where the residual toner adhered without being removed by the cleaning means (cleaning web) is returned to the upstream side by the cleaning means. Therefore, it is possible to realize a fixing device that can reliably prevent toner contamination of the recording medium due to residual toner on the fixing roller when the printing operation is resumed.

In addition to the common effects obtained by the inventions according to claims 1 to 5, the following effects can be obtained according to the inventions described in each claim.
Specifically, according to the invention described in claim 2, in addition to the configuration described in claim 1, a sheet counting unit for detecting the number of fixing processes is provided, and the number of fixing processes is set to a predetermined number or more by the sheet counting unit. When it is detected that the web member has been wound, the winding operation of the web member is executed, so that it is determined whether or not the cleaning means is wound during the non-heating period according to the degree of dirt. It is possible to save the use of the means.
In the present invention, the number of sheets to be fixed is counted by the number of sheets counting means. However, as the function of the number of sheets counting means, the number of sheets to be printed and the number of output processes in the image forming apparatus may be detected.

  According to the invention described in claim 3, in addition to the effect obtained by the invention described in claim 1 or 2, it is provided with a printing rate calculation means for calculating a printing rate of the surface to be printed of the recording medium, and the printing Since the web member winding operation is executed when the printing rate calculated by the rate calculation means reaches a predetermined value or more, the surface of the recording medium on which printing is performed (the surface of each page) ) Printing rate (for example, the ratio of black pixels to all pixels in one page), the web member is estimated at an optimal timing by estimating the degree of dirt on the nip portion (cleaning nip portion) for cleaning. Therefore, it is possible to save the use of the web member.

  According to the invention described in claim 4, in addition to the effect obtained by the invention described in claim 3, when the printing rate calculated by the printing rate calculation means reaches 80% or more, the web Since the member winding operation is executed, the web member can be wound at an optimal timing by performing cleaning when a state close to black solid with a printing rate of 80% or more is detected. As a result, the use of the web member can be saved.

  According to the invention described in claim 5, an image forming unit including a photosensitive drum on which an electrostatic latent image is formed and a toner image is formed based on the electrostatic latent image, and toner is applied to the photosensitive drum. A developing unit having a developing roller to be supplied; a transfer unit for transferring a toner image formed on the photosensitive drum to a conveyed recording medium; and at least one roller member having a heating unit. A fixing unit that melts the toner image and fixes the toner image on the recording medium by passing a recording medium on which an unfixed toner image is formed through a nip portion where the roller members are pressed against each other. And a fixing device including a roller and a cleaning mechanism that cleans the surface of the roller by bringing a web member into contact with the outer peripheral surface of the rotating fixing roller, and is formed on the surface of the photosensitive drum by electrophotography. In an image forming apparatus that transfers and outputs a toner image onto a recording medium, the fixing device according to any one of claims 1 to 4 is used as the fixing device, so that the toner image adheres to the surface of the fixing roller. Since the residual toner thus removed can be surely removed, it is possible to realize an image forming apparatus capable of reliably preventing toner contamination of the recording medium due to the residual toner on the fixing roller when the printing operation is resumed.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is an explanatory diagram showing the overall configuration of an image forming apparatus employing a fixing unit according to an embodiment of the present invention, and FIG. 2 is a schematic diagram showing the configuration of the fixing device.

  As shown in FIGS. 1 and 2, the image forming apparatus 100 according to the present embodiment forms an image by an electrophotographic printing process, and includes a photosensitive drum 21 that is a rotating body, and a photosensitive drum 21. A charger 22 for charging the surface, an optical writing unit (exposure device) 23 for forming an electrostatic latent image on the photosensitive drum 21, and a photosensitive member by developing the electrostatic latent image with a developer. A developing unit 24 for forming a toner image on the drum 21 and a transfer unit (transfer device) for transferring the toner image on the photosensitive drum 21 to a sheet (for example, a sheet-like recording medium such as recording paper or OHP). 25, and a fixing roller 27A for fixing an unfixed toner image on the sheet to the sheet, and a cleaning unit (crusher) for removing residual toner adhering to the surface of the fixing roller A. An image forming apparatus comprising a fixing unit (fixing device) 27 having a Ningu mechanism) 131, a fixing unit 27, those having the characteristic configuration according to the present invention.

First, the overall configuration of the image forming apparatus 100 according to the present embodiment will be described.
The image forming apparatus 100 acquires image data read from a document, or acquires image data received from the outside, and forms a monochrome image indicated by the image data on a sheet. In other words, it includes a document conveying unit (ADF) 101, an image reading unit 102, a printing unit 103, a sheet conveying unit 104, and a paper feeding unit 105.

  When at least one document is set on the document set tray 11, the document transport unit 101 pulls out the document one by one from the document set tray 11 and transports the document to the document reading window 102 a of the image reading unit 102. The document is guided and passed, and the document is discharged to the discharge tray 12.

  A CIS (Contact Image Sensor) 13 is disposed above the document reading window 102a. When the document passes through the document reading window 102a, the CIS 13 repeatedly reads the image on the back side of the document in the main scanning direction and outputs image data indicating the image on the back side of the document.

  Further, the image reading unit 102 exposes the document surface by the lamp of the first scanning unit 15 when the document passes through the document reading window 102a, and the mirror of the first and second scanning units 15 and 16 from the document surface. The reflected light is guided to the imaging lens 17, and an image of the document surface is formed on a CCD (Charge Coupled Device) 18 by the imaging lens 17. The CCD 18 repeatedly reads an image on the document surface in the main scanning direction and outputs image data indicating the image on the document surface.

  Further, when the document is placed on the platen glass on the upper surface of the image reading unit 102, the first and second scanning units 15 and 16 are moved while maintaining a predetermined speed relationship with each other. The document surface on the platen glass is exposed, the reflected light from the document surface is guided to the imaging lens 17 by the first and second scanning units 15 and 16, and the image on the document surface is connected to the CCD 18 by the imaging lens 17. Image.

The image data output from the CIS 13 or the CCD 18 is subjected to various types of image processing by an image processing device 248 (see FIG. 4) and then output to the printing unit 103.
The printing unit 103 records a document image indicated by the image data on a sheet. The photosensitive drum 21, the charger 22, the optical writing unit 23, the developing unit 24, the transfer unit 25, and the cleaning unit 26 described above. And a fixing unit 27 and the like.

  The photosensitive drum 21 has a cylindrical shape and is disposed below the optical writing unit 23. The surface of the photosensitive drum 21 is moved in a predetermined direction (in the direction of arrow A in the figure) by a driving unit and a control unit (not shown). 26 is cleaned, and the cleaned surface is uniformly charged by the charger 22. The charger 22 may be of a charger type or of a roller type or a brush type that contacts the photosensitive drum 21.

  The optical writing unit 23 is a laser scanning unit (LSU) including two laser irradiation units 28a and 28b and two mirror groups 29a and 29b. In the optical writing unit 23, image data is input, laser light corresponding to the image data is emitted from the laser irradiation units 28a and 28b, and the laser light is exposed through the mirror groups 29a and 29b. The surface of the photosensitive drum 21 is irradiated by irradiating the photosensitive drum 21 to expose the surface, and an electrostatic latent image is formed on the surface of the photosensitive drum 21.

  The optical writing unit 23 employs a two-beam system including two laser irradiation units 28a and 28b in order to cope with high-speed printing, thereby reducing the burden associated with increasing the irradiation timing. As the optical writing unit 23, an EL writing head or an LED writing head in which light emitting elements are arranged in an array can be used instead of the laser scanning unit.

  The developing device 24 visualizes the electrostatic latent image formed on the photosensitive drum 21 with toner, and supplies the toner to the surface of the photosensitive drum 21 to develop the electrostatic latent image. An image is formed on the surface of the photosensitive drum 21. The transfer unit 25 transfers the toner image on the surface of the photosensitive drum 21 onto the sheet conveyed by the sheet conveying unit 104. The fixing unit 27 heats and pressurizes the sheet to fix the toner image on the sheet. Thereafter, the sheet is further conveyed to the sheet discharge tray 47 by the sheet conveying unit 104 and discharged. The cleaning unit 26 removes and collects toner remaining on the surface of the photosensitive drum 21 after development and transfer.

Here, the transfer unit 25 includes a transfer belt 31, a drive roller 32, a driven roller 33, an elastic conductive roller 34, and the like, and the transfer belt 31 is stretched between the rollers 32 to 34 and other rollers. Rotating. The transfer belt 31 has a predetermined resistance value (for example, 1 × 10 ⁹ to 1 × 10 ¹³ Ω / cm), and conveys a sheet placed on the surface thereof. The elastic conductive roller 34 is pressed against the surface of the photosensitive drum 21 via the transfer belt 31, and presses the sheet on the transfer belt 31 against the surface of the photosensitive drum 21.

  An electric field having a polarity opposite to the charge of the toner image on the surface of the photosensitive drum 21 is applied to the elastic conductive roller 34, and the toner image on the surface of the photosensitive drum 21 is transferred onto the transfer belt 31 by the electric field having the opposite polarity. It is transferred to the sheet. For example, when the toner image has a charge of (−) polarity, the polarity of the electric field applied to the elastic conductive roller 34 is set to (+) polarity.

  As shown in FIG. 2, the fixing unit 27 includes a pair of fixing rollers (here, a heating roller 123 and a pressure roller 124) 27A that are rotating bodies. Inside the heating roller 123, a main heater 128 and a sub heater 129 are provided as heat sources for setting the surface of the heating roller 123 to a predetermined temperature (heating temperature: approximately 160 to 200 ° C.). A pressure roller heater 138 is provided as a heat source for assisting heating by the roller 123.

  Further, pressure means (not shown) are arranged at both ends of the pressure roller 124 so that the pressure roller 124 is pressed against the heating roller 123 with a predetermined pressure. When the sheet is conveyed to a pressure contact portion (referred to as a fixing nip portion) 127 between the heating roller 123 and the pressure roller 124, the sheet is conveyed by the heating roller 123 and the pressure roller 124, and the indeterminate state on the sheet. The received toner image is heated and melted and pressed to fix the toner image on the sheet.

  The sheet conveyance unit 104 includes a plurality of pairs of conveyance rollers 41, a pair of registration rollers 42, a conveyance path 43, a reverse conveyance path 44, a plurality of branching claws 45, a pair of discharge rollers 46, and the like. ing.

  In the conveyance path 43, the sheet is received from the sheet feeding unit 105 and conveyed until the leading edge of the sheet reaches the registration roller 42. At this time, since the registration roller 42 is temporarily stopped, the leading edge of the sheet reaches and contacts the registration roller 42, and the sheet bends. The leading edge of the sheet is aligned parallel to the registration roller 42 by the elastic force of the bent sheet. Thereafter, the rotation of the registration roller 42 is started, the sheet is conveyed to the transfer unit 25 of the printing unit 103 by the registration roller 42, and the sheet is further conveyed to the sheet discharge tray 47 by the sheet discharge roller 46.

  The registration roller 42 is stopped and rotated by switching the clutch between the registration roller 42 and the drive shaft between an on state and an off state, and switching a motor that is a driving source of the registration roller 42 on and off.

When recording an image on the back side of the sheet, the plurality of branch claws 45 are rotated to switch the branch path between the transport path 43 and the reverse transport path 44, and the front and back sides of the sheet are reversed by the reverse transport path 44. Then, the sheet is returned to the registration roller 42 in the conveyance path 43 via the reverse conveyance path 44. Thereby, an image is also recorded on the back surface of the sheet.
In the conveyance path 43 and the reverse conveyance path 44, sheet detection sensors for detecting the position of the sheet and the like are arranged in various places, and the conveyance roller and the registration roller are driven and controlled based on the position of the sheet detected by each sensor. The sheet is conveyed and positioned.

The paper feed unit 105 includes a plurality of paper feed trays 51. Each paper feed tray 51 is a tray for storing sheets, and is provided below the image forming apparatus 100. Each paper feed tray 51 is provided with a pick-up roller or the like for pulling out the sheets one by one, and sends the pulled sheet to the transport path 43 of the sheet transport unit 104.
Since the image forming apparatus 100 according to the present embodiment performs high-speed printing, the interval between continuously conveyed sheets is narrow (for example, narrow at an interval of about 50 mm). In addition, since the image forming apparatus 100 of the present embodiment is intended for high-speed printing, each of the paper feed trays 51 has a capacity capable of storing 500 to 1500 sheets of standard size sheets.

  Further, on the side surface of the image forming apparatus 100, a large-capacity paper feed cassette (LCC) 52 capable of storing a large amount of a plurality of types of sheets and a manual feed tray 53 for mainly supplying irregular-size sheets are provided. .

  The paper discharge tray 47 is disposed on the side surface opposite to the manual feed tray 53. Instead of the paper discharge tray 47, a post-processing device for paper discharge sheets (stapling, punching, etc.) and a plurality of stages of paper discharge trays can be arranged as options.

  Next, a characteristic configuration of the fixing unit 27 according to the present embodiment will be described in detail with reference to the drawings.

  As shown in FIG. 2, the fixing unit 27 according to the present embodiment includes a pair of a heating roller 123 and a pressure roller 124 as a fixing roller 27A. The heating roller 123 and the pressure roller 124 are arranged to face each other and are configured to rotate in the direction of arrow B and the direction of arrow C in the drawing, respectively. A fixing nip 127 is formed at a pressure contact portion between the heating roller 123 and the pressure roller 124.

  The heating roller 123 has a configuration in which an elastic layer 123a is provided on the peripheral surface of a cylindrical metal core bar, and includes a main heater 128 and a sub heater 129 made of a halogen heater lamp in the inner space of the core bar. . Around the heating roller 123, there are a temperature detector 130 composed of a non-contact type thermistor in the vicinity, and a web sheet type cleaning unit (cleaning mechanism) 131 for wiping off residual toner adhering to the outer peripheral surface of the heating roller 123. Is provided.

  The heating roller 123 detects the surface temperature of the outer periphery by the temperature detector 130, and the operation (energization) of the main heater 128 and the sub heater 129 is controlled so that the surface temperature is in the range of 160 to 200 ° C.

  The cleaning unit 131 mainly includes a feed roller 132 for feeding a web sheet (web member) 133 from the web sheet roll 133a, a tension roller 134 for applying a predetermined tension to the web sheet 133 fed from the feed roller 132, a web A pressure roller 136 that presses the sheet 133 against the outer peripheral surface of the heating roller 123 and a winding roller 137 that winds the used web sheet 133 are configured. A cleaning nip portion 139 for cleaning the surface of the heating roller 123 is formed at a pressure contact portion between the heating roller 123 and the pressing roller 136. The cleaning unit 131 is a regular replacement part that is replaced according to a predetermined replacement cycle.

  On the other hand, the pressure roller 124 also has a configuration in which an elastic layer 124a is provided on the peripheral surface of a cylindrical metal core, similar to the heating roller 123, and is formed by a halogen heater lamp in the inner space of the core. A pressure roller heater 138 is provided.

  Further, peeling claws 135 </ b> A and 135 </ b> B are disposed in contact with the outer peripheral surfaces of the heating roller 123 and the pressure roller 124, respectively, and the sheet subjected to the heating and pressure treatment is wound around the heating roller 123 and the pressure roller 124. Considered not to stick.

  The web sheet 133 is composed of fibers having a thickness of 50 to 150 μm, and the molten toner adhered to the heating roller 123 in contact with the outer peripheral surface of the heating roller 123 is allowed to penetrate into the fiber texture of the web sheet 133. Thus, the web sheet 133 is collected.

  Further, the web sheet 133 moves by a predetermined amount by driving the feed roller 132 and the take-up roller 137 when the number of sheets to be printed (the number of sheets passing through the fixing mechanism) reaches a predetermined number, and is unused. The web sheet 133 is controlled to clean the surface of the heating roller 123. The moving direction of the web sheet 133 is moved in the direction opposite to the rotating direction of the heating roller 123 in contact (the direction of arrow B in FIG. 2) (the direction of arrow D in FIG. 2).

Next, the winding operation of the web sheet 133 by the cleaning unit 131 of this embodiment will be described with reference to the drawings.
FIG. 3 is an explanatory diagram schematically showing the configuration of the fixing unit according to the present embodiment.

In the present embodiment, winding of the web sheet 133 by the cleaning unit 131 is controlled by a control unit 240 (see FIG. 4) described later.
In the present embodiment, the take-up roller 137 and the feed roller 132 constituting the cleaning unit 131 provided in the fixing unit 27 have the same radius r as shown in FIG.

  In the initial state where a new cleaning unit 131 is mounted, the unused web sheet 133 is wound around the feed roller 132, and the radius of the web sheet roll 133a fed from the outermost side is R1. The thickness of the web sheet 133 is uniform, and the thickness is t.

One end of the web sheet 133 is fixed to the winding roller 137, and the radius when the web sheet 133 is wound is substantially equal to the radius r of the shaft portion.
Under this condition, the winding amount wound around the winding roller 137 by one winding operation (that is, the feeding amount from the feeding roller 132) is L (≧ Ln).

In the initial state, when the rotation angle of the winding roller 137 that rotates when winding the winding amount L in the first (n = 1) winding (sending) operation is θ, θ is Is given by
θ = 360 ° × L / (2πr) (1)

On the other hand, the feeding roller 132 rotates following the rotation of the winding roller 137. Accordingly, the feeding roller 132 is configured such that the web sheet roll 133a has the same distance (feeding amount L) as the distance (winding amount L) that the web sheet 133 has moved along the outer circumference of the winding roller 137 (in the circumferential direction). Is moved (rotated) in the circumferential direction. The rotation angle θ1 is given by the following equation.
θ1 = 360 ° × L / (2πR1) (2)

  Thus, the web sheet 133 is taken up by the take-up roller 137, whereby a new web sheet 133 is sent out from the web sheet roll 133 a mounted on the feed roller 132.

  Next, a characteristic electrical configuration of the fixing unit 27 of the present embodiment will be described with reference to the drawings. FIG. 4 is a block diagram showing an electrical configuration relating to the control of the fixing function by the fixing unit of the present embodiment.

As shown in FIG. 4, the control unit 240 of the fixing unit 27 includes a CPU (Central Processing Unit) 241 and a storage unit 242. The storage unit 242 stores various control programs and necessary functions, and includes a ROM (Read Only Memory) and a RAM (Random Access Memory).
The control unit 240 reads various control programs from the storage unit 242 by the CPU 241, and controls the fixing function in the fixing unit 27 by executing the read control programs.

  The control unit 240 may be configured to control not only the fixing unit 27 illustrated in FIG. 2 but also the overall operation of the image forming apparatus 100 illustrated in FIG. In that case, the control unit 240 has a function of further performing process control related to printing of the image forming apparatus 100. When the control unit 240 only controls the fixing unit 27 shown in FIG. 2, the control unit 240 communicates with a control unit (not shown) that controls the overall operation of the image forming apparatus 100 to perform heating unit (fixing roller 27A). ) Drive control may be performed.

In the present embodiment, the control unit 240 controls the overall operation of the image forming apparatus 100.
In the present embodiment, as shown in FIG. 4, the control unit 240 includes a main heater 128 and a sub heater 129 that are heat sources of the heating roller 123, a pressure roller heater 138 that heats the pressure roller 124, a temperature detector 130, and a motor. 243, the winding roller driving unit 245, the time measuring unit 246, and the image processing device 248 are connected to control the operation of each unit.

  The main heater 128, the sub heater 129, and the pressure roller heater 138 are connected to the controller 240 via respective drivers 128a, 129a, and 138a. The controller 240 controls on / off of energization to each heater. In addition, on / off control of energization to each heater 128, 129, 138 can be performed independently.

  The temperature detector 130 detects the surface temperature of the heating roller 123. The controller 240 controls on / off of energization of the main heater 128, the sub heater 129, and the pressure roller heater 138 based on the detection signal from the temperature detector 130 to control the surface temperature of the heating roller 123 and the pressure roller 124. Adjustments are made.

The motor 243 is a drive motor that rotationally drives the heating roller 123 and the pressure roller 124, and is connected to the control unit 240 via the driver 243a and controlled in operation.
The take-up roller drive unit 245 is a drive motor that drives the take-up roller 137, and is connected to the control unit 240 via a driver 245a and controlled in operation.
The timer unit 246 measures the driving time of the winding roller driving unit 245 and sends out the web sheet 133 by a predetermined length.

  In the present embodiment, the control unit 240 is connected to the image processing device 248 via the printing rate calculation unit 247. Based on the image data printed from the image processing device 248, the printing rate of the image printed by the printing rate calculation means 247 is calculated to control the operation of the cleaning unit 131.

  In the present embodiment, the control unit 240 is provided with a sheet count function for counting the number of sheets to be fixed. The number counting function may be, for example, one count when image data for one page is sent from the image processing device 248.

  In the present embodiment, the sheet count function is configured as a part of the control function of the control unit 240. However, a sheet processing apparatus is provided by separately providing a device for electrically or mechanically detecting a sheet to be processed. The number of sheets may be counted.

  Next, characteristic operation control of the cleaning unit 131 of the present embodiment will be described based on a flowchart. FIG. 5 is a flowchart showing an operation of performing the printing process of the image forming apparatus according to the present embodiment.

  First, in the image forming apparatus 100, when a copy start button (not shown) is pressed to instruct the start of printing processing (step S1), printing processing is performed in the image forming unit (step S2), and printing is performed on one page. It is determined whether the printing rate of the image information is 80% or more (step S3).

If it is determined in step S3 that the printing rate of image information printed on one page is 80% or more, the reverse flag for rotating the fixing roller 27A in the reverse direction to the normal rotation direction is turned ON. (Step S4). When the printing process is completed (step S5), the page number count is incremented by +1 by the number counting function of the control unit 240 (step S6).

  On the other hand, if it is determined in step S3 that the printing rate of the image information printed on one page is not 80% or more, the printing process is performed as it is, and the process proceeds to step S5 and step S6.

Next, it is confirmed whether or not data for the next page exists (step S7).
If it is determined in step S7 that the next page of data exists, the process returns to step S2 and the printing process is repeated.

  On the other hand, if it is determined in step 7 that there is no data for the next page, it is confirmed whether or not the page count value is 30 (sheets) or more as the total number of pages subjected to the printing process (step 7). Step S8).

  If it is determined in step S8 that the page count value is 30 (sheets) or more, the reverse rotation flag is turned on and the process proceeds to step S10 (step S9). On the other hand, if it is determined that the page count value is not 30 (sheets) or more, the process proceeds to step S10.

  In step 10, it is confirmed again whether or not the reverse rotation flag is ON. If it is determined that the reverse rotation flag is ON, the web sheet for cleaning the toner remaining on the surface of the heating roller 123 in the cleaning processing step. 133 is contacted for a predetermined time, and the heating roller 123 is driven in the direction opposite to the normal rotation direction (reverse rotation) to perform a cleaning process (step S11), and the processing operation of the image forming apparatus 100 is stopped (step S12). ).

  On the other hand, if it is determined in step 10 that the reverse rotation flag is not ON, the processing operation of the image forming apparatus 100 is stopped without performing the above-described cleaning process (step S12).

Here, a characteristic cleaning action by the cleaning unit 131 of the present embodiment will be described in detail with reference to the drawings.
FIG. 6 is an explanatory view showing a state in which the toner adhered to the heating roller of the fixing unit of the present embodiment remains, and FIG. 7 is an explanatory view showing a state in which the heating roller is rotated reversely to perform cleaning.

  As shown in FIG. 6, in the fixing unit 27, the toner adhering to the surface of the heating roller 123 is downstream of the pressing roller 136 in the rotation direction of the heating roller before the next fixing process is performed after the fixing process or after the cleaning process. If present on the side, the toner may be transferred to the pressure roller 124 side in the next fixing process or may be transferred onto the next conveyed sheet to cause toner contamination.

  Therefore, in the cleaning operation in the fixing unit 27 of the present embodiment, as shown in FIG. 7, after the fixing process or before the next fixing process is performed in the cleaning process of step S <b> 11 of the operation control described above, as shown in FIG. With the web sheet 133 in contact with the surface of the sheet 123 for a predetermined time, the heating roller 123 is rotated in the direction reverse to the normal rotation direction (arrow b direction) while the unused web sheet 133 is moved by the winding roller 137. By cleaning the surface of the heating roller 123 while winding in the D direction, the toner remaining on the downstream side in the rotation direction of the heating roller from the contact portion (cleaning portion) with the web sheet 133 is removed by the unused web sheet 133. Can do.

  As described above, according to the present embodiment, in the cleaning operation of the cleaning unit 131 of the fixing unit 27 in the image forming apparatus 100, the web sheet 133 is brought into contact with the heating roller 123 while being wound for a predetermined time. The unused portion is fed out and the heating roller 123 is rotated so as to be opposite to the moving direction of the web sheet 133, so that the unused web sheet 133 is in contact with the web sheet 133 (cleaning portion). Further, the toner remaining on the downstream side in the rotation direction of the heating roller can be surely removed. In this way, high-quality image output can be realized with a simple configuration and simple control that eliminates toner contamination due to residual toner adhering to the heating roller 123.

  In addition, according to the present embodiment, the web sheet 133 used for cleaning is wound up every time a predetermined number of printing processes are performed, and cleaning is performed using the unused web sheet 133. Therefore, the cleaning performance can be always maintained. Stable printing quality can be ensured.

  Furthermore, according to the present embodiment, the degree of contamination of the cleaning portion of the web sheet 133 is estimated based on the printing rate of the surface of the sheet to be printed, and the web is printed at an optimal timing according to the printing situation together with the number of printed sheets. Since the sheet 133 can be wound, the use of the web sheet 133 can be saved.

  In this embodiment, the cleaning unit 131 is disposed corresponding to the heating roller 123 of the fixing unit 27. However, the present invention does not limit the roller member to be cleaned, and corresponds to, for example, the pressure roller 124. Thus, a fixing unit (fixing device) according to the present invention may be configured.

  The preferred embodiments of the present invention have been described above. However, it goes without saying that the present invention is not limited to the above-described examples, and those skilled in the art will recognize various modifications within the scope of the claims. It is obvious that modifications can be conceived, and it is understood that they also belong to the technical scope of the present invention.

  For example, in the above-described embodiment, the present invention is applied to an image forming apparatus in which a monochrome developing device is installed. However, the present invention may be applied to a color image forming apparatus in which a plurality of developing devices are installed. Is possible. Furthermore, it is possible to develop the present invention in correspondence to an apparatus using a roller member that has a need to clean the roller member.

1 is an explanatory diagram illustrating an overall configuration of an image forming apparatus employing a fixing unit according to an embodiment of the present invention. FIG. 2 is a schematic diagram illustrating a configuration of the fixing unit. FIG. 2 is an explanatory diagram schematically showing a configuration of the fixing unit. FIG. 2 is a block diagram showing an electrical configuration relating to control of a fixing function by the fixing unit. 4 is a flowchart illustrating an operation of performing a printing process of the image forming apparatus. FIG. 4 is an explanatory diagram illustrating a state where toner adhered to a heating roller of the fixing unit remains. It is explanatory drawing which shows the state which reversely rotates the said heating roller and performs cleaning.

Explanation of symbols

21 Photosensitive drum 24 Developer (developing part)
25 Transfer unit (transfer section)
27 Fixing unit (fixing device)
27A Fixing roller 100 Image forming apparatus 123 Heating roller (roller member)
124 Pressure roller (roller member)
127 Nip part 128 Main heater (heat generating means)
129 Sub-heater (heat generation means)
130 Temperature detector 131 Cleaning unit (cleaning mechanism)
132 Feed roller 133 Web sheet (web member)
133a Web sheet roll 134 Tension roller 136 Pressure roller 137 Winding roller 138 Pressure roller heater (heating means)
240 Control Unit 243 Motor 245 Winding Roller Drive Unit 246 Timekeeping Unit 247 Print Rate Calculation Unit 248 Image Processing Device

Claims (5)

The toner image is formed by passing a recording medium having an unfixed toner image formed in a nip portion provided with a pair of roller members provided with heat generating means on at least one roller member and pressing the roller members together. A fixing roller for melting and fixing on the recording medium, a web member is brought into contact with the outer peripheral surface of the rotating fixing roller to clean the roller surface, and a portion used for cleaning the fixing roller is periodically taken up. In a fixing device having a cleaning mechanism having a function,
After the fixing process of the toner image to the recording medium by the fixing roller is completed or before the fixing process of the toner image to the recording medium by the fixing roller is performed, the web member is brought into contact with the fixing roller. A function to wind up for a predetermined time,
A function of rotating the fixing roller so as to be in a direction opposite to a moving direction of the web member at a contact portion with the web member when winding the web member;
A fixing device. A sheet counting means for detecting the number of fixing processes;
The fixing device according to claim 1, wherein the web member winding operation is executed when the number counting unit detects that the number of sheets to be fixed reaches a predetermined number or more. A printing rate calculating means for calculating the printing rate of the surface to be printed of the recording medium;
3. The fixing device according to claim 1, wherein the web member is wound up when the printing rate calculated by the printing rate calculation unit reaches a predetermined value or more. .   The fixing device according to claim 3, wherein the web member is wound up when the printing rate calculated by the printing rate calculation unit reaches 80% or more. An image forming unit including a photosensitive drum on which an electrostatic latent image is formed and a toner image is formed based on the electrostatic latent image; a developing unit including a developing roller that supplies toner to the photosensitive drum; A transfer unit that transfers a toner image formed on the photosensitive drum to a transported recording medium, and a pair of roller members including a heating unit in at least one roller member, and the roller member A fixing roller that melts and fixes the toner image on the recording medium by passing a recording medium on which an unfixed toner image is formed in a nip portion where the two are pressed against each other, and an outer peripheral surface of the rotating fixing roller. A fixing device having a cleaning mechanism for cleaning the surface of the roller by contacting the web member is provided, and a toner image formed on the surface of the photosensitive drum is transferred onto a recording medium by an electrophotographic method. In the image forming apparatus,
An image forming apparatus using the fixing device according to claim 1 as the fixing device.

Images