JP2008129138A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of improving the durable lifetime of a cleaning member that cleans a rotating body by contacting with the rotating body. <P>SOLUTION: The image forming apparatus includes an image carrier 1; a transfer means 5 for transferring a thermal-melting toner image that is carried by the image carrier, according to image information, to a recording material P; the rotating bodies 21 and 22 that hold and carry the recording material at a nip part N between them and thermally fix the toner image to the recording material. The image forming apparatus also includes cleaning members 24 and 25 that function as the cleaning members for cleaning the rotating bodies, for recovering the toner that stuck to the rotating bodies, by contacting with the rotating bodies; and a control means 102, having an edgeless printing mode of transferring the toner image to the recording material beyond the edge of the recording material. The control means is configured so as to decide the timing of cleaning by the cleaning member in the edgeless printing mode, based on the image information corresponding to the toner image lying in the vicinity of the edge of the recording material beyond the edge of the recording material. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that transfers a toner image formed and supported on an image carrier such as an electrophotographic photosensitive member onto a transfer material.

  In image forming apparatuses such as electrophotographic copying machines and electrophotographic printers, margins (such as silver halide photography) are reduced due to the recent diversification of printer demand and the spread of digital image recording apparatuses such as digital still cameras. There is an increasing demand for printing without borders. Borderless printing has already been put to practical use in an inkjet image forming apparatus in recent years. Thus, an apparatus capable of borderless printing (printing) has been desired even in an electrophotographic image forming apparatus.

  In an electrophotographic image forming apparatus, when borderless printing is performed on a transfer material, the toner image is transferred to the transfer material so as to protrude from the leading edge, rear edge, left edge, and right edge of the transfer material. Accordingly, a part of the toner image is also transferred to the edge surfaces (side surfaces) of the front end portion, rear end portion, left end portion, and right end portion of the transfer material. The transfer material is nipped and conveyed at a nip portion between the outer peripheral surface (surface) of the fixing roller of the fixing device (fixing device) and the outer peripheral surface (surface) of the pressure roller. In the conveying process, the unfixed toner image is heated and fixed to the transfer material by receiving heat and pressure at the nip portion.

  When the transfer material is nipped and conveyed at the nip portion of the fixing device, the toner image transferred onto the edge surface of the transfer material may adhere to the surface of the fixing roller and the pressure roller. The toner may adhere again to the transfer material as the fixing roller and the pressure roller rotate, and may contaminate the transfer material.

In Patent Document 1, the toner attached to the surface of the pressure roller is collected and collected by the cleaning roller, and when the number of transfer materials onto which the toner images are transferred reaches a predetermined number, the collected toner is discharged to the cleaning paper, A technique for cleaning the cleaning roller itself has been proposed.
JP 2003-57985 A

  However, in the system described in the above publication, the cleaning roller itself needs to be cleaned once every several hundred sheets, which tends to be complicated for the user. Further, since the cleaning roller is in contact with the pressure roller, there is a tendency that the durability of the cleaning roller is shortened.

  An object of the present invention is to provide an image forming apparatus capable of improving the durability life of a cleaning member that comes into contact with a rotating body and cleans the rotating body.

The configuration for solving the above problems includes an image carrier, transfer means for transferring a heat-meltable toner image carried by the image carrier in accordance with image information to a recording material, and the recording material by a nip portion. A rotating body that heats and fixes a toner image to a recording material while nipping and conveying, and a cleaning member that cleans the rotating body, and that collects the toner that contacts the rotating body and adheres to the rotating body An image forming apparatus comprising: a member; and a control unit having a borderless printing mode for transferring a toner image by protruding an edge of the recording material from the recording material,
The control means determines the cleaning timing of the cleaning member itself on the basis of image information corresponding to a toner image around the edge that protrudes from the edge of the recording material when the marginless printing mode is executed.

  ADVANTAGE OF THE INVENTION According to this invention, provision of the image forming apparatus which can improve the durable life of the cleaning member which contacts a rotary body and cleans a rotary body is realizable.

  Hereinafter, the present invention will be described with reference to the drawings.

(1) Example of Image Forming Apparatus FIG. 1 is a structural model diagram of an example of an image forming apparatus according to the present invention. This image forming apparatus is a color image forming apparatus (full color laser beam printer) that forms an image on a transfer material (hereinafter referred to as a recording material) such as recording paper and an OHP sheet using an electrophotographic image forming system.

  In the following description, with respect to the image forming apparatus, the fixing device, and the constituent members thereof, the longitudinal direction is a direction orthogonal to the recording material conveyance direction on the surface of the recording material. The longitudinal direction is also the axial direction of the photosensitive drum. The short direction is the recording material conveyance direction on the surface of the recording material.

  The image forming apparatus shown in the present embodiment has two print modes, a print mode with margins for printing with margins and a borderless print mode for printing without margins. The mode switching is processed using a known method such as input to a host computer (not shown) or an operation panel, for example, in the same manner as the printing mode switching of special paper such as cardboard or OHP sheet.

  The image forming apparatus according to the present exemplary embodiment includes a controller (control unit) 102 including a CPU and a memory such as a ROM and a RAM in an image forming apparatus main body 101 constituting a housing of the image forming apparatus. A print signal S1 with a border or a print signal S2 without a border is input to the controller 102 from a host computer or an operation panel.

  Further, in the image forming apparatus main body 101, first to fourth four toner images of yellow, magenta, cyan, and black are formed as image forming means for forming an image on a recording material. It has image forming stations SY, SM, SC, and SK. Each station S (Y to K) has a drum-shaped electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) 1 as an image carrier. Around each photosensitive drum 1, there are a charging roller 2 as a charging means, a laser scanner unit 3 as an exposure means, a developing device 4 as a developing means, a transfer roller 5 as a transferring means, and a cleaning means. A cleaning device 6 is provided. An electrostatic conveyance belt 7 as a recording medium conveyance unit is disposed so as to face the photosensitive drum 1 of each station S (Y to K). The conveyor belt 7 is stretched around two axes of a driving roller 8a and a driven roller 8b. A transfer roller T is formed between the photosensitive drum 1 and the conveyor belt 7 by disposing the transfer roller 5 so as to face each photosensitive drum 1 with the conveyor belt 7 interposed therebetween.

  Next, an image forming operation corresponding to the borderless printing mode will be described.

  When the controller 102 inputs the borderless printing signal S1, predetermined members of each station S (Y to K) are sequentially driven in accordance with a predetermined borderless printing control sequence. The photosensitive drum 1 of each station S (Y to K) is rotated at a predetermined peripheral speed (process speed) in the direction of the arrow by a rotation drive system (not shown). In synchronization with the photosensitive drum 1, the conveying belt 7 is also rotated by the driving roller 8 a by the rotational driving system in the direction of the arrow at a peripheral speed corresponding to the rotational peripheral speed of each photosensitive drum 1.

  First, in the first color yellow Y station SY, the outer peripheral surface (surface) of the photosensitive drum 1 is uniformly charged to a predetermined polarity and potential by the charging roller 2. Next, the scanner unit 3 scans and exposes the surface of the photosensitive drum 1 with a laser beam corresponding to the image data (image information). As a result, an electrostatic latent image corresponding to the image data is formed on the surface of the uniformly charged photoreceptor drum 1. The latent image is developed by the developing device 4 with yellow toner (developer), and a heat-meltable yellow toner image (development image) is formed on the surface of the photosensitive drum 1. A similar image forming process is performed in each of the magenta M, cyan C, and black K stations S (M to K). A toner image (development image) of each color is formed on the surface of the photosensitive drum 1 of each station S (Y to K).

  On the other hand, the recording material P stacked and stored in the feeding cassette 9 is sent to the registration roller pair 11 by the pickup roller 10. Next, the recording material P is conveyed between the conveying belt 7 and the electrostatic transfer roller 12 by the roller pair 11 in the vicinity of the driven roller 8b. The electrostatic transfer roller 12 electrostatically attracts the recording material P to the outer peripheral surface (front surface) of the transport belt 7. The recording material P is conveyed from the transfer portion T on the upstream side in the rotation direction to the transfer portion T on the downstream side in the rotation direction by the rotation of the conveyance belt 7. In the conveying process, the toner images on the photosensitive drums 1 are transferred onto the recording material P in order by the transfer portion T by the transfer roller 5 on the surface of the recording material P.

  In each station S (Y to K), the transfer residual toner remaining on the surface of the photosensitive drum 1 after the transfer of the toner image to the recording material P is removed by a cleaning blade 13 a provided in the photosensitive drum cleaning device 6. Thus, the photosensitive drum 1 is repeatedly used for the next image formation.

  Here, transfer of the toner image onto the recording material P in borderless printing will be described. 2A is an explanatory view showing a transfer area of a toner image onto the recording material P by borderless printing, and FIG. 2B is an explanatory view showing toner transferred onto the edge surface of the recording material P. FIG.

  In borderless printing, as shown in FIG. 2A, a mask area Am for determining a printing area for the recording material P is set to have a predetermined width for each of the front end portion, the rear end portion, the left end portion and the right end portion of the recording material P. The area is larger than the recording material P by the additional area An of (2 mm). Then, a toner image corresponding to the mask area Am including the area of the additional area An is formed on the surface of the photosensitive drum 1, and the toner image is transferred onto the surface of the recording material P by the transfer roller 7. In addition, an image having no margin on the edge of the recording material P can be formed. By performing borderless printing by such a method, when the recording material P passes through the transfer nip portion T, the recording material P is skewed due to a conveyance failure or the recording material P is relative to the longitudinal direction of the transfer roller 7. Even if position variations occur, borderless printing can always be performed on the recording material P satisfactorily.

  In borderless printing, the toner in the added region An outside the recording material P is transferred to the outer peripheral surface (front surface) of the transfer belt 7 when the toner image is transferred. The toner transferred to the surface of the transfer belt 7 is removed by a cleaning blade 13 a provided on the transfer belt cleaner 13.

  The recording material P separated from the surface of the transfer belt 7 and exiting the transfer portion is introduced into the nip portion N of the fixing device (fixing means) 14. The fixing device 14 sandwiches and conveys an unfixed toner image on the recording material P by a fixing roller 21 and a pressure roller 22 as rotating bodies at a nip portion N. In the conveying process, heat and pressure are applied to the toner image to heat and fix the toner image on the surface of the recording material P.

  By the way, in borderless printing, a part of the toner in the added area An outside the edge of the recording material P (hereinafter referred to as an edge portion) at the time of transfer of the toner image is the leading edge, the trailing edge, It is transferred to the edge part (side face part) at the left end part and the right end part (FIG. 2B). Therefore, in the process of nipping and conveying the recording material P at the nip portion N of the fixing device 14, the toner in the edge portion adheres as an offset toner to the outer peripheral surface (surface) of the fixing roller 21 and the outer peripheral surface (surface) of the pressure roller 22. Sometimes. Alternatively, the toner may adhere to either the surface of the fixing roller 21 or the surface of the pressure roller 22 as an offset toner. Therefore, in order to collect the offset toner on the surface of the fixing roller 21, a cleaning roller 24 as a collecting member is provided so as to be in contact with or separated from the surface of the fixing roller 21. Further, in order to collect the offset toner on the surface of the pressure roller 22, a cleaning roller 25 as a collecting member is provided so as to be able to contact or separate from the surface of the pressure roller 22. The configuration of the fixing device 14 will be described later.

  The recording material P exiting the fixing device 14 is discharged by a discharge roller 15 onto a discharge tray 16 provided on the upper portion of the apparatus main body 101.

  Reference numeral 17 denotes a conveying means. The conveying unit 17 includes a pickup roller 10, a registration roller pair 11, a discharge roller 15, and the like.

(2) Fixing Device FIG. 3 is a cross-sectional side model view of an example of the fixing device 14 having a variable pressure device. FIG. 4 is a view of the fixing roller 21, the pressure roller 22, and the cleaning rollers 24 and 25 as viewed from the recording material P introduction side. FIG. 5 is a vertical side view of the fixing roller 21, the pressure roller 22, and the cleaning rollers 24 and 25.

  The fixing device 14 shown in this embodiment includes a fixing roller 21, a pressure roller 22, a halogen heater (heating source) 23, and cleaning rollers 24 and 25. The fixing device 14 includes variable pressure devices (pressure variable devices) 31 and 32 and a thermistor (temperature detector) 27.

  The fixing roller 21 is a roller having a diameter of 40 mm and a thickness of 3.0 mm, in which an elongated cylindrical aluminum is used as a core metal 21a, and a PFA release layer 21b is coated on the surface layer. Both ends of the cored bar 21a are rotatably held by side plates (not shown) provided at both ends in the longitudinal direction of the apparatus frame 71 via bearings 31L and 31R.

  The halogen heater 23 provided inside the cored bar 21a of the fixing roller 21 is supported in a state where the seal portions 23L and 23R at both ends are fixed to the side plate of the frame 71 via a heater holder (not shown).

  The pressure roller 22 has a silicon sponge elastic layer 22b on the outer peripheral surface of an elongated solid stainless steel core 22a, and a PFA release layer 23 on the outer peripheral surface of the elastic layer 22b. The pressure roller 22 has a diameter of 30 mm and a product hardness of 60 °. The pressure roller 22 is disposed below the fixing roller 21 so as to face the fixing roller 21 in parallel, and both ends of the cored bar 22a are rotatably held on the side plate of the frame 71 via bearings 32L and 32R. Both ends of the cored bar 22a are pressed against the fixing roller 21 by a pressurizing spring (pressing means) (not shown) with a pressing force of 250N. As a result, the surface of the pressure roller 22 is brought into contact with the surface of the fixing roller 21 to elastically deform the elastic layer 22b, whereby a nip portion (fixing nip portion) N having a predetermined width (6.0 mm) is formed between the surface of the fixing roller 21. Forming.

  The thermistor 27 is supported on the side plate of the frame 71 via a support member (not shown). The thermistor 27 is arranged at the substantially longitudinal central portion of the fixing roller 21 (substantially central portion (FIG. 4) of the conveyance area of the maximum size recording material P) by the supporting member. As a result, the surface temperature of the fixing roller 21 can be accurately detected, and stable fixing performance can be ensured.

  In the fixing device 14 of this embodiment, the rotation drive control circuit (rotation drive control means) 41 rotates the fixing motor (drive source) M1 in response to the drive command signal S2 from the controller 102. The motor M1 rotates the rotation drive gear G (FIG. 4) provided on the cored bar 22a of the pressure roller 22 to rotate the pressure roller 22 in the arrow direction. The pressure roller 22 applies a rotational force to the fixing roller 21 through the nip portion N. As a result, the fixing roller 21 is driven to rotate in the direction of the arrow as the pressure roller 22 rotates.

  On the other hand, the temperature control circuit (temperature control means) 42 turns on the power supply circuit (power supply means) 43 in response to the power supply command signal S3 from the controller 102. As a result, the power feeding circuit 43 applies power to the heater 23. The heater 23 generates heat when electric power is applied to heat the fixing roller 21. The temperature of the fixing roller 21 is detected by the thermistor 27 and input to the temperature control circuit 42. The temperature adjustment control circuit 42 outputs a power supply control signal S4 to the power supply circuit 43 and performs on / off control of the power supply circuit 43, so that the temperature detected by the thermistor 27 becomes a predetermined temperature (target temperature). To control. In this embodiment, the power feeding circuit 43 is controlled so that the temperature detected by the thermistor 27, that is, the surface temperature of the fixing roller 21 is about 180 ° C. The recording material P carrying the unfixed toner image t in a state where the surface of the fixing roller 21 is adjusted to a predetermined temperature is introduced into the nip portion N by the entrance guide 72. The recording material P is nipped and conveyed by the nip portion N, and the unfixed toner image t is heated and fixed on the recording material P by being heated and pressurized in the conveyance process. Then, the recording material P that has exited the nip portion N is sent out from the fixing device 14 by the discharge roller 73. Separation claws 74 and 75 are provided on the nip portion N on the discharge roller 73 side. The separation claw 74 prevents the recording material P from being wrapped around the fixing roller 21, and the separation claw 75 prevents the recording material P from being wound around the pressure roller 22.

  Next, the cleaning rollers 24 and 25 and the variable pressure devices 31 and 32 will be described.

  The cleaning rollers 24 and 25 are each formed in an elongated pipe shape. The cleaning roller 24 collects the offset toner attached to the surface of the fixing roller 21 by attaching it. The cleaning roller 25 collects the offset toner attached to the surface of the pressure roller 22 by attaching it. The materials of the cleaning rollers 24 and 25 have lower surface releasability than the corresponding fixing roller 21 and pressure roller 22 in terms of the function of attaching and collecting offset toner on the surface of the fixing roller 21 and the pressure roller 22. Is needed. Further, since the offset toner must be cooled and collected instantaneously, it is necessary that the thermal conductivity be high. In this embodiment, as the cleaning rollers 24 and 25, elongated pipe-shaped aluminum rollers having a diameter of 10 mm are used.

  The variable pressure device 31 includes a cleaning roller holding member 31a, a spring seat member (pressure means holding member) 31b, a tension coil spring (pressure means) 31c, and a cam (displacement member) 31d. The holding member 31a passes through the hollow portion 24a (FIG. 5) of the cleaning roller 24, and supports an elongated shaft portion 31a1 that rotatably supports the cleaning roller 24, a holding portion 31a2 that holds both ends of the shaft portion 31a1, (FIGS. 4 and 5). The holding portion 31a2 is held at its end a opposite to the shaft portion 31a1 by a rear plate 51a (FIG. 3) on the recording material discharge side of the frame 71 so as to be swingable. The fixing roller 21 is centered on the end a. Swings in the radial direction. The spring seat member 31b disposed below the holding portion 31a2 has an end b on the same side as the end a side of the holding portion 31a2 held by the rear plate 51a so as to be swingable, and is held around the end a. It swings in a direction approaching or separating from the member 31a. One end of the spring 31c is connected to the spring seat member 31b and the other end is connected to the holding portion 31a2. The cam 31d having a substantially elliptical cross-sectional shape is disposed between the holding portion 31a2 and the spring seat member 31b and between the end portions a and b of the holding portion 31a2 and the spring seat member 31b and the spring 31c. . The cam 31d is fixed to a rotating shaft 31e that is rotatably held on a side plate of the frame 71.

  The variable pressure device 32 includes a cleaning roller holding member 32a, a spring seat member (pressure means holding member) 32b, a tension coil spring (pressure means) 32c, and a cam (displacement member) 32d. The holding member 32a passes through the hollow portion 25a (FIG. 5) of the cleaning roller 25, and supports an elongated shaft portion 32a1 that rotatably supports the cleaning roller 25, a holding portion 32a2 that holds both ends of the shaft portion 32a1, and (FIGS. 4 and 5). The holding portion 32a2 has an end c opposite to the shaft portion 32a1 held by a rear plate 51a (FIG. 3) on the recording material discharge side of the frame 71 so as to be swingable, and a pressure roller centering on the end c. 22 oscillates in the radial direction. The spring seat member 32b disposed above the holding portion 32a2 has an end portion d on the same side as the end portion c of the holding portion 32a2 that is swingably held by the rear plate 51a, and the holding member is centered on the end portion d. It swings in a direction toward or away from 32a. One end of the spring 32c is connected to the spring seat member 32b and the other end is connected to the holding portion 32a2. The cam 32d having a substantially elliptical cross-sectional shape is arranged between the holding portion 32a2 and the end portions c and d of the spring seat member 32b and the spring 32c between the holding portion 32a2 and the spring seat member 32b. . The cam 32d is fixed to a rotating shaft 32e that is rotatably held on a side plate of the frame 71.

  The variable pressure devices 31 and 32 are cams 31d and 32d by a cleaning motor (second drive source) M2 (FIG. 3) via a rotation drive gear (not shown) provided on the corresponding rotation shafts 31e and 32e, respectively. Is rotated by a predetermined angle. That is, the rotation drive control circuit 44 drives the cleaning motor M2 in response to the drive command signal S5 from the controller 102. Accordingly, the cleaning motor M2 rotates the cams 31d and 32d by a predetermined angle in a predetermined direction via the rotation drive gear and the rotation shafts 31e and 32e.

  FIG. 6 is a diagram for explaining the operation of the variable pressure devices 31 and 32.

  As shown in FIG. 6 (a), the cams 31d and 32d are rotated from the standby position shown in FIG. 6 (b) in the direction of the arrow, and the small diameter portions 31d1 and 31d1 provided on the outer peripheral surfaces of the cams 31d and 32d, respectively. It stops at the position where 32d1 and holding portions 31a1 and 32a1 come into contact. The holding member 31a swings in a direction away from the fixing roller 21 around the end a in accordance with the rotation of the cam 31d, thereby separating the cleaning roller 24 from the surface of the fixing roller 21. Further, the holding member 32a swings in a direction away from the pressure roller 22 around the end c in accordance with the rotation of the cam 32d, thereby separating the cleaning roller 25 from the surface of the pressure roller 22.

  In the standby position shown in FIG. 6B, the cams 31d and 32d are in positions where the small diameter portions 31d1 and 32d1 do not contact any of the holding members 31a and 32a and the spring seat members 31b and 32b, respectively. The holding member 31a that is not in contact with the cam 31d swings toward the spring seat member 31b by the tensile force of the spring 31c, and the surface of the cleaning roller 24 is brought into contact with the surface of the fixing roller 21 by the applied pressure Fa according to the tensile force. The nip portion Na is formed. The cleaning roller 24 is driven to rotate as the fixing roller 21 rotates. The offset toner adhering to the surface of the fixing roller 21 adheres to the surface of the roller 24 through the cleaning nip portion Na and is collected. The holding member 32a that is not in contact with the cam 32d is swung to the spring seat member 32b side by the tension force of the spring 32c, and the surface of the cleaning roller 25 contacts the surface of the pressure roller 22 by the applied pressure Fb corresponding to the tension force. Thus, the cleaning nip portion Nb is formed. The cleaning roller 25 rotates following the rotation of the pressure roller 22. The offset toner adhering to the surface of the pressure roller 22 adheres to the surface of the roller 25 through the cleaning nip portion Nb and is collected.

  As shown in FIG. 6C, the cams 31d and 32d are rotated in the direction of the arrow from the standby position shown in FIG. 6B, and the small diameter portions 31d1 and 32d1 and the spring seat members 31b and 32b come into contact with each other. Stop at position. As the cam 31d rotates, the spring seat member 31b swings in a direction away from the holding member 31a around the end b, and further extends the spring 31c to increase the tensile force. As a result, the spring seat member 31b brings the surface of the cleaning roller 24 into contact with the surface of the fixing roller 21 with a pressing force corresponding to the tensile force of the spring 31c at the cleaning nip Na, that is, a pressing force Fa1 larger than the pressing force Fa. The cleaning roller 24 is rotated following the rotation of the fixing roller 21 and collects the offset toner attached to the surface of the fixing roller 21 by being attached to the surface of the roller 24 through the cleaning nip portion Na. As the cam 32d rotates, the spring seat member 32b swings in a direction away from the holding member 32a around the end c, and further extends the spring 32c to increase the tensile force. As a result, the spring seat member 32b brings the surface of the cleaning roller 25 into contact with the surface of the pressure roller 22 with a pressing force corresponding to the tensile force of the spring 32c at the cleaning nip portion Nb, that is, a pressing force Fb1 larger than the pressing force Fb. . The cleaning roller 25 is driven to rotate with the rotation of the pressure roller 22, and the offset toner attached to the surface of the pressure roller 22 is attached to the surface of the roller 25 through the cleaning nip portion Nb and collected.

(3) Image contamination of the recording material P generated by the collected toner When a large amount of recording material P is continuously introduced into the nip portion N in borderless printing, the surface temperature of the cleaning rollers 24 and 25 is about the melting point temperature of the toner. May exceed 160 ° C. In this case, the toner reverse flow phenomenon occurs in which the offset toner ta (FIG. 3) adhering to the surface of the cleaning roller 24 melts and adheres to the surface of the fixing roller 21. Further, a toner reverse flow phenomenon occurs in which the offset toner ta (FIG. 3) adhering to the surface of the cleaning roller 25 melts and adheres to the surface of the pressure roller 22. The toner that has flowed back to the surface of the fixing roller 21 and the surface of the pressure roller 22 adheres to the recording material P again after the rotation of the fixing roller 21 and the pressure roller 22 and causes image contamination. Therefore, when the toner adhering to the surfaces of the cleaning rollers 24 and 25 exceeds a certain amount, it is necessary to clean the cleaning rollers 24 and 25 themselves.

(4) Control Sequence for Borderless Printing Mode In this embodiment, therefore, the cleaning roller 24 is based on the image data around the edge portion of the recording material P (image data of the added area An) when the borderless printing mode is executed. 25 itself is determined. That is, the edge toner adhesion amount that adheres to the edge portion of the recording material P is calculated from the image data around the edge portion of the recording material P, the type and thickness of the recording material P. The current toner adhesion amount of the cleaning rollers 24 and 25 is calculated by integrating the edge toner adhesion amount and the value obtained from the length in the conveyance direction of the recording material P (integral toner amount integration value). When the toner adhesion amount of the cleaning rollers 24 and 25 exceeds a certain value (determination reference value), the cleaning rollers 24 and 25 are automatically cleaned.

  The control sequence for the borderless printing mode is stored in the memory of the controller 102. FIG. 7 is a flowchart of an example of the control sequence.

  In S1, a borderless print signal S1 is input to start image formation in the borderless print mode.

  In S2, the average value u of the image data around the edge portion at the tip of the recording material P is calculated. In the present embodiment, the periphery of the edge portion at the tip of the recording material P is an area of ± 1 mm with respect to the edge of the recording material P. This area may be appropriately selected according to the printing accuracy, paper feeding accuracy, and the like.

  In S3, the average value u is multiplied by the toner adhesion coefficient c and the thickness d corresponding to the type of the recording material selected by the user such as gloss paper or film paper as the recording material P, and the longitudinal direction of the recording material P is determined. A value A corresponding to the amount of attached toner per unit length is calculated. Since gloss paper and film paper have more toner adhering to the edge portion than plain paper, the toner adhesion coefficient c is set to 1.2. For ordinary paper such as plain paper and plain paper thick paper, the toner adhesion coefficient is 1.0.

In S4, it is determined whether the edge toner adhesion amount A is less than or equal to a certain value (reference value). When the edge toner adhesion amount A is less than a certain value (N), the process proceeds to S5, and the cleaning rollers 24 and 25 are brought into contact with the rollers 21 and 22 with a low pressure (FIG. 6B). When the edge toner adhesion amount A is equal to or larger than a certain value (Y), the process proceeds to S6, and the cleaning rollers 24 and 25 are brought into contact with the rollers 21 and 22 with a high pressure (FIG. 6C). In this embodiment, the edge toner adhesion amount A is less than or equal to the value of (toner amount M per unit area corresponding to a solid color) × (average thickness d of recording material for borderless printing). Therefore, the pressure applied to the cleaning rollers 24 and 25 is determined. As the thickness d of the recording material P, a representative paper thickness value corresponding to the paper type selected by the user is used. In this embodiment, the toner carrying amount M per unit area when the solid color is solid is approximately 0.5 mg / cm ^2. For example, the thickness d of the recording material P in the thick paper mode is 0.1 mm. Accordingly, M × d is 0.005 mg / cm or more. The pressure applied to the cleaning rollers 24 and 25 is determined based on whether or not the recording material edge toner adhesion amount per unit length is less than or equal to 0.005 mg / cm. In this embodiment, when the edge toner adhesion amount A is less than a certain value, the pressing force on one side in the longitudinal direction of the cleaning rollers 24 and 25 is set to 9.8 N, and the cleaning rollers 24 and 25 are set to 19.6 N on both sides. The rollers 21 and 22 are in contact with each other. If the edge toner adhesion amount A is a certain value or more, the pressure on one side of the cleaning rollers 24 and 25 in the longitudinal direction is set to 14.7 N, and the cleaning rollers 24 and 25 are moved to the rollers 21 and 2 with a pressure of 29.4 N on both sides. 22 is contacted. In this way, by changing the pressure applied to the cleaning rollers 24 and 25 according to the edge toner adhesion amount A, the cleaning efficiency of the cleaning rollers 24 and 25 is switched.

  In S7, after the image formation of the recording material P is completed, the cleaning rollers 24 and 25 are separated from the rollers 21 and 22 (FIG. 6A). Further, the driving of the fixing motor M1 is stopped and the rotation of the fixing roller 21 and the pressure roller 22 is stopped.

  In S8, when the borderless printing is continued, each time an image is formed on one recording material P, a value obtained by multiplying the edge adhesion amount A calculated in S3 by the length L in the conveying direction of the recording material P (A X) is calculated.

  In S9, every time the image formation of one recording material P is completed, it is determined whether the edge toner amount integrated value B is less than or equal to a certain value. When the edge toner integrated value B is equal to or greater than a certain value, it indicates that the amount of toner attached to the surfaces of the cleaning rollers 24 and 25 has increased. Therefore, the cleaning roller cleaning mode is executed (S10). Then, after executing the cleaning mode, the series of control sequences is terminated. The cleaning roller cleaning mode will be described later. When the toner integrated value B is less than a certain value, the post-rotation process is executed (S11). And after performing a rotation process after that, a series of control sequences are complete | finished. Here, the post-rotation step refers to a predetermined post-operation (such as a cleaning step) by continuing to drive the rotational drive system for a while after printing of the last recording material P is completed and rotating the photosensitive drum 1. It is a process of performing.

  A flowchart of an example of the cleaning roller cleaning mode is shown in FIG.

  In S21, the cleaning rollers 24 and 25 are brought into contact with the rollers 21 and 22, respectively. In this embodiment, as shown in FIG. 6C, the cleaning rollers 24 and 25 are brought into contact with the rollers 21 and 22 with a high pressure of 29.4 N on both sides.

  In S <b> 22, the fixing motor M <b> 1 is driven to rotate the fixing roller 21 and the pressure roller 22, and power is supplied to the heater 23 to heat the fixing roller 21 and the pressure roller 22. As the fixing roller 21 and the pressure roller 22 are rotated, the cleaning rollers 24 and 25 are also driven and the temperature of the fixing roller 21 and the pressure roller 22 is increased.

  In S23, the surface temperature of the fixing roller 21 detected by the thermistor 27 is taken in, and it is determined whether or not the detected temperature is lower than 180 ° C., which is a temperature for performing normal printing. If the detected temperature is 180 ° C. or higher, the process proceeds to S24. Since the detected temperature 180 ° C. is higher than the melting point temperature (160 ° C.) of the toner adhering to the surfaces of the cleaning rollers 24 and 25, the adhering toner melts and flows back to the rollers 21 and 22. Thereby, the toner adhered on the surfaces of the cleaning rollers 24 and 25 can be sufficiently adhered to the surfaces of the fixing roller 21 and the pressure roller 22. In this embodiment, the surface temperature of the fixing roller 21 is maintained at 180 ° C., which is higher than the melting point temperature (160 ° C.) of the toner, and the toner adhering to the surfaces of the cleaning rollers 24 and 25 is caused to flow back to the rollers 21 and 22. However, the surface temperature of the fixing roller 21 is not limited to this.

  In S 24, a cleaning material (not shown) having a maximum width size that can be used in the image forming apparatus is fed from the feeding cassette 9 by the transport unit 17. The cleaning material is nipped and conveyed at the nip portion N via the transfer nip portion T. In the conveying process, the backflow toner on the surface of the fixing roller 21 and the surface of the pressure roller 22 adheres to the cleaning material surface and is collected. When the cleaning material is discharged onto the discharge tray 16, a series of cleaning roller cleaning modes is completed.

  The image forming apparatus of this embodiment determines the cleaning timing of the cleaning rollers 24 and 25 themselves based on the image information around the edge portion of the recording material P as described above. Therefore, even when image formation is performed in the borderless printing mode, the cleaning timing of the cleaning rollers 24 and 25 themselves can be delayed when printing an image pattern in which the toner amount at the edge portion of the recording material P is not large. As a result, the number of cleanings of the cleaning rollers 24 and 25 when performing borderless printing can be reduced, and durability can be improved. Further, since the pressing force of the cleaning rollers 24 and 25 is switched according to the amount of adhesion of the edge toner, the pressing force of the cleaning rollers 24 and 25 is minimized, and damage to the fixing roller 21 and the pressure roller 22 is minimized. can do. Also by this, the durability of the cleaning rollers 24 and 25 can be improved.

  The image forming apparatus of this embodiment cleans the cleaning rollers 24 and 25 on an operation panel (not shown) attached to the upper portion of the apparatus main body 101 to notify the user before executing the cleaning roller cleaning mode. Display to execute. In this embodiment, the operation panel is used to notify the user. However, in recent years, there are few cases where the user is in the vicinity of the image forming apparatus in a networked environment. You may notify the user.

  Further, instead of executing the cleaning roller cleaning mode, the cleaning rollers 24 and 25 that collect the toner adhering to the fixing roller 21 and the pressure roller 22 may be replaced with new cleaning rollers 24 and 25. For convenience of the replacement work, the shaft portions 31a1, 32a1 of the holding members 31a, 32a and the holding portions 31a2, 32a2 can be detachably connected with screws or the like. At the time of replacement, the holding members 31a and 32a are disassembled into the shaft portions 31a1 and 32a1 and the holding portions 31a2 and 32a2, and the cleaning rollers 24 and 25 that collect the adhered toner are pulled out from the shaft portions 31a1 and 32a1. Then, new cleaning rollers 24 and 25 may be inserted into the shaft portions 31a1 and 32a1.

  Another example of the image forming apparatus will be described.

  In this embodiment, members and portions common to the image forming apparatus of Embodiment 1 are denoted by the same reference numerals, and the description thereof is incorporated. The same applies to Example 3 and Example 4.

  The image forming apparatus shown in the present embodiment has the same configuration as the image forming apparatus 100 of the first embodiment, except that a cleaning blade is used instead of the cleaning rollers 24 and 25 in the fixing device 14 of the first embodiment. FIG. 9 is an explanatory view showing another example of the variable pressure device, and is a cross-sectional side view of an example of the fixing device 14 having the variable pressure device.

  A cleaning blade 24 </ b> A is held by the holding portion 31 a 2 of the holding member 31 a of the pressure application varying device 31. The blade 24A is brought into contact with or separated from the surface of the fixing roller 21 by the variable pressure device 31. A cleaning blade 25 </ b> A is held by the holding portion 32 a 2 of the holding member 32 a of the pressure application varying device 32. The blade 25A is brought into contact with or separated from the surface of the pressure roller 22 by the variable pressure device 32. The blades 24A and 25A determine the pressure applied to the fixing roller 21 and the pressure roller 22 corresponding to the edge toner adhesion amount A of the recording material P. As the blades 24A and 25A, metal scrapers are used.

  In the image forming apparatus of this embodiment, the offset toner adhering to the surface of the fixing roller 21 and the pressure roller 22 during the borderless printing mode is scraped off by the blades 24A and 25A, and the waste toner box 26A provided in the frame 71 is used. , 26B will be stored. Non-flammable fibers are attached to the waste toner boxes 26A and 26B, and the toner ta stored in the boxes 26A and 26B soaks into the fibers so that there is no fear of toner leakage.

  In the case of the present embodiment using the blades 24A and 25A as the cleaning members, the surfaces of the rollers 21 and 22 may be damaged if the blades 24A and 25A are brought into contact with the corresponding rollers 21 and 22 with an excessive pressure. However, since the blades 24A and 25A are brought into contact with the rollers 21 and 22 with a minimum necessary pressure, the surfaces of the rollers 21 and 22 are not damaged.

  Another example of the image forming apparatus will be described.

  In the image forming apparatus shown in the present embodiment, in order to switch the cleaning efficiency of the cleaning rollers 24 and 25 of the fixing device 14, a cleaning roller temperature control device (temperature) that maintains the temperature of each of the cleaning rollers 24 and 25 at the melting temperature of the toner. Control means) 51. Further, a temperature detecting means 52 is provided for detecting the temperature of each of the cleaning rollers 24 and 25. As the temperature detection means 52, a contact thermistor using a thermocouple is used. The thermistor 52 is arranged in contact with the longitudinal center of the cleaning rollers 24 and 25.

  FIG. 10 is a structural model diagram of an example of the temperature control device 51. Although FIG. 10 shows the temperature control device 52 on the cleaning roller 24 side, the temperature control device 51 on the cleaning roller 25 side has the same configuration as the temperature control device 51 on the cleaning roller 24 side.

  In the image forming apparatus of the present embodiment, an air cooling unit is used as the temperature control device 51. The temperature control device 51 is driven by the controller 102 based on the temperature detected by the thermistor 52. The temperature control device 51 includes a fan (blower member) 53, a fan motor (drive source) M3, and a duct (ventilating member) 54. When the borderless printing mode is executed, when the cleaning roller 24 reaches a certain temperature or more according to the temperature detection result of the thermistor 52, the fan 53 is rotated to blow outside air outside the apparatus main body 101 to the cleaning roller 24. Is kept below a certain temperature. That is, when the borderless printing mode is executed, the controller 102 captures the detected temperature of the thermistor 52 and outputs a drive command signal S6 to the rotation drive control circuit (rotation drive control means) 45 so as to keep the detected temperature below a certain temperature. To do. The motor M3 is rotationally driven by the rotational drive control circuit 45 in response to a drive command signal S6 from the controller 102, and rotates the fan 53. The fan 53 blows outside air through the duct 54 from the outlet 54 a to the cleaning roller 24. In the present embodiment, the rotation of the fan 53 is controlled by the controller 102 in accordance with the edge toner adhesion amount A. That is, when the edge toner adhesion amount A is small (less than a certain value), the rotation of the fan 53 is controlled so that the surface temperature of the cleaning roller 24 is 160 degrees or less. When the edge toner adhering amount A is large (when it is greater than a certain value), the rotation of the fan 53 is controlled so that the surface temperature of the cleaning roller 24 is 150 degrees or less in order to further improve the cleaning ability.

  According to the image forming apparatus of the present embodiment, the temperature of the cleaning rollers 24 and 25 can be minimized according to the edge toner adhesion amount A. Therefore, the time for which the user waits for cooling of the cleaning rollers 24 and 25 can be shortened. .

  Further, according to the image forming apparatus of the present embodiment, the cleaning efficiency of the cleaning rollers 24 and 25 is switched according to the edge toner adhesion amount A, so that the pressing force of the cleaning rollers 24 and 25 can be set to one stage. In that case, since the end portions b and c of the spring seat members 31b and 32b may be fixed to the frame 71 in the variable pressure devices 31 and 32, the bearing structure of the end portions b and c of the spring seat members 31b and 32b is simplified. Can be

  Another example of the image forming apparatus will be described.

  The image forming apparatus shown in the present embodiment is a cleaning roller cleaning device (cleaning member) that controls the amount of winding of the web in contact with the cleaning rollers 24 and 25 in order to switch the cleaning efficiency of the cleaning rollers 24 and 25 of the fixing device 14. Cleaning means) 61. Similarly to the third embodiment, the spring seat members 31b and 32b end portions b and c of the pressure application variable devices 31 and 32 are fixed to the frame 71, and the application pressure of the cleaning rollers 24 and 25 is set to one level.

  FIG. 11 is a structural model diagram of an example of the cleaning device 61. Although FIG. 11 shows the cleaning device 61 on the cleaning roller 24 side, the cleaning device 61 on the cleaning roller 25 side has the same configuration as the cleaning device 61 on the cleaning roller 24 side.

  In the cleaning device 61, a web 62, which is a heat-resistant fiber of a strip-like nonwoven fabric that is long in the recording material conveyance direction, is in contact with the surface of the cleaning roller 24 by a web pressing roller 63. The web pressing roller 63 is rotatably held by the web unit 64. The web pressing roller 63 is pressed against the surface of the cleaning roller 24 by a spring 66 provided between a spring seat surface 65 attached to the web unit 64 and the longitudinal end of the web pressing roller 63. . Both ends of the web 62 are connected to web take-up rollers 67 and 68 rotatably held by the web unit 64, and the one web take-up roller 67 is rotated by a stepping motor (not shown). As a result, the web 62 is wound from the winding roller 68 to the winding roller 67. By winding the web 62, the toner adhering to the surface of the cleaning roller 24 adheres to the web 62 and is collected.

  The web pressing roller 63 has an aluminum core bar 63a having a diameter of 10 mm. Around the mandrel 63a, a silicon rubber layer (elastic layer) 63a of about 1 mm is formed in order to increase the contact area with the surface of the cleaning roller 24 and increase the scraping ability of the toner adhering to the surface of the cleaning roller 24. It is coated. The web unit 64 is detachably attached to the apparatus main body 101. When the web 62 reaches the end of its useful life (time to be replaced), the web unit 64 is notified to the user via an operation panel (not shown) or a network, and the user can replace the web unit 64 with a new web unit 64. .

  In this embodiment, the winding amount of the web 62 is determined according to the edge toner adhesion amount A when the borderless printing mode is executed. That is, when the edge toner adhesion amount A is small (less than a certain value) and large (when it is greater than a certain value), the winding amount of the web 62 is 10 μm to 100 μm per borderless print. The winding amount of the web 62 is variable. If a jam occurs during image formation for borderless printing, the toner adhered to the surface of the cleaning roller 24 is collected by the web 62 after the jam recovery, and the web winding amount at that time is set to 100 μm. Yes.

  According to the image forming apparatus of the present embodiment, the web 62 can be used to the maximum of the durable life by minimizing the winding amount of the web 62 by the edge toner adhesion amount A.

  In this embodiment, the cleaning rollers 24 and 25 are cleaned by the web 62, but the surface of the fixing roller 21 and the surface of the pressure roller 22 may be directly cleaned by the web 62 without using the cleaning rollers 24 and 25. In that case, the web pressing roller 63 is held movably by the web unit 64. Then, the web pressing roller 63 is moved in accordance with the edge toner adhesion amount A by a predetermined pressing force varying device to vary the pressing force of the web pressing roller 63 against the cleaning rollers 24 and 25. Even if such a configuration is adopted, the same effect can be obtained.

[Other]
1) In the first and second embodiments, the pressurizing variable devices 31 and 32 change the pressurizing force of the cleaning rollers 24 and 25 in two stages by swinging the spring seat members 31b and 32b by the cams 31e and 32e. ing. The pressurizing force of the cleaning rollers 24 and 25 is not limited to two stages. For example, by using an electromagnetic solenoid as the pressurizing variable devices 31 and 32, the pressurizing force of the cleaning rollers 24 and 25 can be continuously changed. Also good.

  2) The pressurizing variable devices 31, 32, the cleaning roller temperature control device 51, and the cleaning roller cleaning device 61 can be applied not only to a color image forming apparatus but also to a monochrome image forming apparatus.

1 is a configuration model diagram of an example of an image forming apparatus. (A) is an explanatory view showing a transfer area of a toner image onto a recording material by borderless printing, and (b) is an explanatory view showing toner transferred onto the edge surface of the recording material. It is a cross-sectional side model figure of an example of the fixing device which has a pressing force variable apparatus. FIG. 3 is a diagram of a fixing roller, a pressure roller, and a cleaning roller as viewed from the recording material introduction side. It is a vertical side view model diagram of a fixing roller, a pressure roller, and a cleaning roller. It is operation | movement explanatory drawing of a pressurization variable apparatus. It is a flowchart of an example of the control sequence of borderless printing mode. It is a flowchart of an example of a cleaning roller cleaning mode. It is explanatory drawing showing the other example of a pressing force variable apparatus, Comprising: It is a cross-sectional side model figure of an example of the fixing device which has the pressing force variable apparatus. It is a structural model figure of an example of a cleaning roller temperature control apparatus. It is a composition model figure of an example of a cleaning roller cleaning device.

Explanation of symbols

1: photosensitive drum, 5: transfer roller, 17: conveying means, 21: fixing roller, 22: pressure roller, 24, 25: cleaning roller, 24A, 25A: cleaning blade, 31, 32: variable pressure device, 51: Cleaning roller temperature control device, 61: Cleaning roller cleaning device, 102: Controller, N: Nip part, P: Recording material

Claims (8)

An image carrier, transfer means for transferring a heat-meltable toner image carried by the image carrier according to image information to a recording material, and heating the toner image while nipping and conveying the recording material by a nip portion. A rotating member fixed on the recording material; a cleaning member for cleaning the rotating member; a cleaning member that contacts the rotating member and collects toner adhering to the rotating member; and An image forming apparatus having control means having a borderless printing mode for transferring a toner image by protruding from the edge,
The control means determines the cleaning timing of the cleaning member itself based on image information corresponding to a toner image around the edge that protrudes from the edge of the recording material when the marginless printing mode is executed. .   The control means includes a value obtained by using the image information corresponding to the toner image around the edge protruding from the edge of the recording material, the type and thickness of the recording material, and the length in the conveyance direction of the recording material. The image forming apparatus according to claim 1, wherein a cleaning timing of the cleaning member itself is determined based on an integrated value.   The image forming apparatus according to claim 1, further comprising: a pressing force varying unit configured to vary a pressing force for pressing the cleaning member and bringing it into contact with the rotating body in order to switch the cleaning efficiency of the cleaning member. apparatus.   A conveying unit configured to convey a recording material, and the control unit presses the cleaning member against the rotating body by the pressurizing variable unit when the cleaning timing is determined; A cleaning member cleaning mode is performed in which the cleaning material is transported to the nip portion by the transporting means, and the toner recovered by the cleaning member is attached to the cleaning material through the rotating body and recovered. The image forming apparatus according to claim 3.   The image forming apparatus according to claim 1, further comprising a temperature control unit configured to maintain the cleaning member at a toner melting temperature in order to switch the cleaning efficiency of the cleaning member.   The image forming apparatus according to claim 1, further comprising a cleaning member cleaning unit that includes a web in contact with the cleaning member and controls a winding amount of the web in order to switch a cleaning efficiency of the cleaning member. .   The image according to any one of claims 1 to 6, wherein the cleaning member is a cleaning roller that can contact or be separated from the rotating body and that rotates in contact with the rotating body. Forming equipment.   The image forming apparatus according to claim 1, wherein the cleaning member is a cleaning blade that can contact or be separated from the rotating body and is in contact with the rotating body.

Images