JP2006221089A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To decrease a current capacity during cleaning in an image forming apparatus in which an image carrying body and a rotating body are individually driven, and to efficiently eliminate developer image contamination of the rotating body by increasing the cleaning effect by one cleaning sheet. <P>SOLUTION: The apparatus has a cleaning mode in which a heating body 20 is energized while a cleaning sheet is held by a transfer nip T and a fixing nip N to repeat driving and stopping of an image carrying body driving means 12 and a rotating body driving means 29. During the cleaning mode, a control means 30 starts to drive the image carrying body driving means and the rotating body driving means at different timings. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus that forms an image on a recording material.

  2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a laser beam printer that forms an image on a recording material using an electrophotographic process method, a rotating drum type photosensitive member (hereinafter referred to as a photosensitive drum) is used as an image carrier. The developer image (toner image) to be carried is transferred onto a recording material by a transfer means, and the recording material is introduced into a fixing device and heated while being nipped and conveyed at a nip portion between fixing rotating members as a rotating body. A developer image is heat-fixed on the recording material.

  Incidentally, as the above-described fixing device, a heat roller type or an on-demand type is known.

  The fixing device of the heat roller type is a nip portion (fixing nip portion, heating nip portion) by pressing and contacting a pair of rollers (fixing roller and pressure roller) as a fixing rotating member having a heating body (heat source). In this nip portion, a recording material such as paper is introduced and nipped and conveyed to heat and melt an unfixed toner image (hereinafter also referred to as toner or toner layer) on the recording material. And fixed as a permanently fixed image.

  Of the pair of rollers described above, the fixing roller that contacts the surface of the recording material (the side carrying the toner) is a cylindrical roller whose surface is made of a material having good releasability, and is disposed inside. The toner is heated by a halogen heater (heating body). On the other hand, the pressure roller in contact with the back surface of the recording material is configured by providing an elastic layer on the core bar, and applies an appropriate pressure to the toner layer.

  Here, it is ideal that all the toner on the surface of the recording material is heated and melted and fixed on the surface of the recording material. However, if there is a cold offset toner that does not completely melt, a toner that is too hot and hot offset, or a toner that is electrostatically offset to the fixing roller (hereinafter referred to as toner contamination) on the surface of the recording material, these The toner stains adhere to the roller peripheral surface of the fixing roller and the pressure roller, which has poor releasability.

  When the releasability of the fixing roller is worse than that of the pressure roller, toner stains adhere to the peripheral surface of the fixing roller. In this case, since the fixing roller is always heated to the toner melting temperature during image formation, the toner stain is in a molten state. Since the melted toner stain is mixed with the toner image on the surface of the recording material and moves to the recording material when the next recording material comes, it is difficult for the fixing roller to be continuously soiled. However, in some cases, toner contamination may be present on the peripheral surface of the fixing roller, and in such a case, there is a possibility that the image is stained.

  On the other hand, when the releasability of the pressure roller is lower than that of the fixing roller, the toner stain once offset to the peripheral surface of the fixing roller moves to the peripheral surface of the pressure roller through the nip portion during rotation of the roller. The temperature of the pressure roller is lower than that of the fixing roller, and the moved toner stain does not necessarily exist in a completely melted state on the pressure roller. Further, since the toner image on the surface of the recording material does not come into contact with the pressure roller, toner contamination is rarely carried by the toner image. However, once the toner stains move to the peripheral surface of the pressure roller, there is a drawback that the toner stains on the peripheral surface of the fixing roller adhere to the toner stains and accumulate the toner stains. If toner stains are accumulated on the pressure roller peripheral surface, the releasability of the pressure roller peripheral surface is reduced, so that the recording material is wound around the pressure roller. There was a problem that the back side of the recording material was soiled at once.

  Next, the film heat fixing type fixing device enables quick start and power saving as compared with the above-described heat roller type. In the film heating and fixing method, instead of the halogen heater and fixing roller in the heat roller method, a quick start by reducing the heat capacity using a heater (heating body) such as ceramic and a thin flexible film such as polyimide. It enables power saving.

  In such a film heat fixing type fixing device, since a thin flexible film is used as a fixing film, since the heat capacity is small and the temperature responsiveness is good, it is not necessary to preheat the fixing film, and fine temperature control becomes possible. The energization of the heater can be turned off except when the recording material is introduced into the nip portion (hereinafter referred to as “sheet feeding”).

  However, in the fixing device of the film heating and fixing method, when the temperature control as described above is performed, the pressure roller is not heated except when the paper is passed, so that the temperature is less likely to rise compared to the heat roller method. For this reason, the toner stain that is offset to the peripheral surface of the fixing film and transferred to the peripheral surface of the pressure roller through the nip portion is not melted on the peripheral surface of the pressure roller, but is almost fixed on the peripheral surface of the pressure roller. Exists.

  In such a state, when the recording material is nipped and conveyed at the nip portion, the toner contamination on the circumferential surface of the pressure roller can hardly be removed. The toner stains could not be removed by cleaning with the cleaning paper disclosed in Patent Document 1, that is, the paper on which the solid image was fixed. In some cases, the toner of the solid image on the cleaning paper is peeled off by the toner on the peripheral surface of the pressure roller, which may promote the pressure roller contamination.

Therefore, in an on-demand fixing device, a cleaning sheet is sandwiched by a nip formed between a pressure roller as a fixing member and a fixing film, and rotation of the pressure roller and the fixing film is stopped. Heat the heater to melt toner stains on the pressure roller peripheral surface, and then perform step feed to rotate the pressure roller and fixing film by the amount corresponding to the fixing nip to clean the pressure roller peripheral surface with a sheet. A method is disclosed in US Pat.
JP-A-3-58074 Japanese Patent Laid-Open No. 2000-047509

  In recent years, the speed of image forming apparatuses has increased, and the driving torque of image forming apparatuses has increased. Compared to the case where the photosensitive drum and the fixing member, which is the rotating body of the fixing device, are rotated using a single motor in order to obtain the required driving torque, the photosensitive drum and the fixing device are rotated using two motors. In the case where the fixing member as a body is individually rotated and driven, the cost of the entire image forming apparatus can be reduced, the space can be reduced, and the size of the apparatus can be reduced. An image forming apparatus using a motor is employed. In some cases, when two small motors are used, the cost can be reduced compared to when one large motor is used. That is, in the configuration of one motor, it is necessary to use a large motor, and a large space is required for arranging the motor, which affects the size of the apparatus. On the other hand, in the two-motor configuration, the driving torque of each motor can be reduced, so that a small motor can be used. Therefore, it can be arranged in a small space, and a configuration that does not affect the size of the apparatus can be taken.

  Further, in the image forming apparatus in which the photosensitive drum and the fixing member of the fixing device are individually driven to rotate, the driving of the photosensitive drum can be controlled independently of the driving of the fixing member, so that unnecessary rotation with respect to the photosensitive drum can be eliminated. The life can be extended by reducing the wear of the photosensitive drum. Also, the recording material conveyance speed for nipping and conveying the recording material at the transfer nip portion between the photosensitive drum and the transfer roller in contact with the photosensitive drum, and the recording material conveyance speed for nipping and conveying the recording material at the fixing nip portion of the fixing device Can be controlled independently of each other, so that the recording material conveyance behavior can be stabilized.

  In recent years, in order to reduce the size of the image forming apparatus, an image forming apparatus that shortens the distance between the transfer nip portion between the photosensitive drum and the transfer roller and the fixing nip portion of the fixing device has been realized.

  However, in the image forming apparatus in which the distance between the transfer nip portion and the fixing nip portion of the fixing device as described above is short, and the main body driving motor for driving the photosensitive drum and the fixing driving motor for driving the fixing member are individually driven. When performing the fixing cleaning mode in which the fixing member is repeatedly driven and stopped (step feed) as in the conventional example, the distance between the transfer nip portion and the fixing nip portion is short, so the sheet used for cleaning is separated from the transfer nip portion. It is necessary to drive and stop the sheet while being sandwiched by both the fixing nip portion. Therefore, when the sheet is moved, it is necessary to start (start) the main body motor and the fixing motor at the same time.

  When starting to drive the motor, a larger starting current flows than during normal rotation. Therefore, if the two motors are started simultaneously as described above, the motor operation becomes unstable. Further, it is necessary to increase the capacity of the power supply of the image forming apparatus in correspondence with the starting currents of the two motors, and there is a problem that the power supply and the entire apparatus are increased in size. When the power source capacity is increased, it is necessary to adopt a corresponding element and electric circuit configuration, and the power source unit becomes larger. This is because an increase in the power supply unit affects the size of the apparatus.

  In order to reduce the starting current, which is the above problem, the cleaning operation may be performed by driving and stopping only the fixing motor. In this case, after the sheet trailing edge passes through the transfer nip portion, the cleaning operation is performed with the sheet sandwiched only by the fixing nip portion. However, in this configuration, since the cleaning operation area for one sheet is an area corresponding to the distance from the recording material discharge position of the transfer nip portion to the fixing nip portion, the cleaning efficiency of one sheet is reduced. Further, in order to obtain the required cleaning effect, it is necessary to perform cleaning using a plurality of sheets, and there is a problem that the time required for cleaning increases and the number of sheets used for cleaning increases.

  Accordingly, an object of the present invention is to reduce the current capacity during the cleaning operation and increase the cleaning effect of one cleaning sheet in an image forming apparatus that individually drives the image carrier and the rotating body. An object of the present invention is to provide an image forming apparatus capable of efficiently removing developer image contamination on a rotating body.

  A typical image forming apparatus according to the present invention includes an image carrier that is rotationally driven, a transfer member that contacts the image carrier to form a transfer nip portion, and a fixing nip portion that contacts the image carrier. A rotating body and a heating body that generates heat when energized and heats the rotating body, and sandwiches and conveys the recording material at the transfer nip portion to transfer the developer image carried by the image carrier to the recording material by a transfer member. In the image forming apparatus in which the recording material is nipped and conveyed at the fixing nip portion together with the transfer nip portion, and the developer image is heated and fixed on the recording material through the rotating member, the image bearing member that rotationally drives the image bearing member A driving unit; a rotating unit driving unit that rotates the rotating unit; a control unit that controls on / off of energization of the heating unit; and a drive unit that controls driving of the image carrier driving unit and the rotating unit driving unit; And fixing nip A cleaning mode in which energization of the heating body is turned on while the sheet is sandwiched and the image carrier driving means and the rotating body driving means are repeatedly driven and stopped. The image forming apparatus is characterized in that the image carrier driving means and the rotating body driving means are driven at different timings.

  In addition, another configuration of a typical image forming apparatus according to the present invention includes an image carrier that is rotationally driven, a transfer member that abuts the image carrier and forms a transfer nip portion, and a fixing nip that abuts each other. And a heating member that heats and rotates the rotating member by energization, and sandwiches and conveys the recording material at the transfer nip portion to transfer the developer image carried on the image carrier by the transfer member. In an image forming apparatus that transfers to a recording material, nipping and conveying the recording material at the fixing nip portion together with the transfer nip portion, and heating and fixing the developer image to the recording material through the rotating body, the image carrier is rotationally driven. Image carrier driving means for rotating, rotating body driving means for rotating the rotating body, control means for controlling on / off of energization to the heating body and controlling driving of the image carrier driving means and the rotating body driving means, The transfer nip and fixing nip A cleaning mode in which energization of the heating body is turned on and off while the sheet for sandwiching is sandwiched and the image carrier driving means and the rotating body driving means are repeatedly driven and stopped. At this time, the control means is an image forming apparatus characterized in that the energization to the heating body is turned off and the driving of the image carrier driving means and the rotating body driving means is started at different timings.

  According to the present invention, in the cleaning mode, the driving currents at the start of driving of both the driving units do not overlap by making the driving start timings of the rotating body driving unit and the image carrier driving unit different from each other. The overall current capacity can be reduced, the drive of both drive means can be stabilized, and the power supply and the device can be downsized. That is, since the current capacity can be reduced, the power source can be reduced in size, and the drive means having a small drive torque can be used as each of the drive means described above, so that it can be arranged in a space that does not affect the size of the apparatus, and the apparatus can be reduced in size . Further, the entire area of the sheet can be used as a cleaning operation area, so that the cleaning effect can be increased, and the developer stains adhering to the rotating body can be efficiently removed. Further, the cleaning effect can be further improved by turning off the energization to the heating body.

  Hereinafter, embodiments of the present invention will be described.

[Embodiment 1]
(1) Example of Image Forming Apparatus FIG. 1 is an overall configuration diagram of an example of an image forming apparatus according to the present invention. The image forming apparatus shown in this embodiment is a laser beam printer using an electrophotographic process method.

  In the following description, a material used for normal image formation will be described as a recording material, and a material used for cleaning the fixing device will be described as a sheet to distinguish them.

  The image forming apparatus shown in FIG. 1 includes a photosensitive drum 1 as an image carrier. The photosensitive drum 1 is rotationally driven at a predetermined process speed (PS = 200 mm / s) in the clockwise direction indicated by an arrow by a main body driving motor 12 as an image carrier driving means.

  Around the photosensitive drum 1, in order along the rotation direction, a charging roller 2 as a charging device, an exposure device 3, a developing device 4, a transfer roller (transfer member) 5 as a transfer device, and a cleaning blade as a cleaning device. 6 is arranged.

  In addition, a paper feed cassette 7 that stores a recording material P such as paper is disposed at the lower part of the apparatus main body. A paper feed roller 15, a transport roller 8, and a top sensor 9 are sequentially arranged along the transport path of the recording material P. A photosensitive drum 1, a transfer roller 5, a conveyance guide 10, a fixing device 11, a paper discharge roller 13, and a paper discharge tray 14 are arranged.

  Next, the operation of the image forming apparatus having the above-described configuration will be described.

  The photosensitive drum 1 that is rotationally driven in the direction of the arrow by the main body drive motor 12 is uniformly charged to a predetermined polarity and a predetermined potential by the charging roller 2. The photosensitive drum 1 after charging is exposed L based on image information by an exposure device (laser scanner) 3 of a laser optical system on its peripheral surface. That is, the exposure device 3 exposes the uniformly charged surface treated surface of the rotating photosensitive drum 1 with the laser beam L that is ON / OFF controlled according to the time-series electric digital image signal of the image information. As a result, the potential of the exposed portion of the uniformly charged surface of the photosensitive drum 1 is attenuated, and an electrostatic latent image corresponding to the image information is formed on the surface of the photosensitive drum. The electrostatic latent image is developed by the developing device 4. The developing device 4 includes a developing roller 4a. A developing bias is applied to the developing roller 4 to attach toner to the electrostatic latent image on the photosensitive drum 1 and develop (visualize) the toner image.

  On the other hand, the recording material P stored in the paper feeding cassette 7 is fed by the paper feeding roller 15 and is conveyed by the conveying roller 8 to the transfer nip T between the photosensitive drum 1 and the transfer roller 5. At this time, the leading edge of the recording material P is detected by a top sensor 9 provided between the conveying roller 8 and the transfer nip T, and is synchronized with the toner image on the photosensitive drum 1. A transfer bias is applied to the transfer roller 5, whereby the toner image on the photosensitive drum 1 is transferred to a predetermined position on the recording material P.

  The recording material P carrying the unfixed toner image on the surface by transfer is transported along the transport guide 10 to the fixing device 11 where the unfixed toner image is heated and pressurized to be permanently fixed on the recording material P. As established.

  The recording material P after the toner image is fixed is discharged onto a paper discharge tray 14 on the upper surface of the apparatus main body by a paper discharge roller 13.

  On the other hand, after the toner image is transferred, the toner remaining on the surface without being transferred to the recording material P is removed by the cleaning blade of the cleaning device 6, and the next image formation is performed.

  By repeating the above operation, image formation can be performed one after another.

  The main body drive motor 12 rotationally drives the photosensitive drum 1, the transfer roller 5, the paper feed roller 15, the transport roller 8, the paper discharge roller 13, and the like. As the main body drive motor 12, for example, a stepping motor, a DC motor, or the like can be used. In addition to continuously rotating the photosensitive drum 1 and the rollers 8, 13, and 15, the intermittent drive is performed at predetermined angles. It is also possible to do this. That is, the recording material P can be stepped while repeating rotation and stop of the photosensitive drum 1 and the rollers 8 and 15.

(2) Fixing device 11
FIG. 2 is a structural model diagram of an example of the fixing device 11, and FIG. 3 is an enlarged model diagram of a fixing nip portion. The fixing device shown in this embodiment is a film fixing type device using a sleeve-like film.

  The fixing device 11 includes a fixing rotating body (hereinafter, referred to as a fixing film) 25 made of a sleeve-like flexible film, and a roller-shaped pressing rotating body as rotating bodies that contact each other to form a fixing nip N. (Hereinafter referred to as a pressure roller) 26. Further, a ceramic heater (hereinafter referred to as a heater) 20 as a heating element for heating the unfixed toner image t on the recording material P via the fixing film 25, a temperature control means 27 for controlling the temperature of the heater 20, And a fixing motor 29 as a rotating body driving means.

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

  The fixing film 25 has a small heat capacity and is formed of a heat-resistant resin such as polyimide in a cylindrical shape, and a release layer 25a such as a fluororesin is provided on the surface. The fixing film 25 has a total thickness of 100 μm or less, and includes the heater 20 and the heater holder 22 in the hollow portion. The fixing film 25 is pressed against the heater 20 by the elasticity of the pressure roller 26, so that the back surface of the fixing film 25 is brought into contact with the lower surface of the heater 20.

  Reference numeral 31 denotes a U-shaped rigid pressure stay with a downward vertical cross section made of metal, and is attached to the upper surface between the arc portions 22 a and 22 a of the heater holder 22 in the fixing film 25. The pressure stay 31 is a member elongated in the longitudinal direction, and both ends thereof are supported by a device chassis side plate (not shown) via a pressure spring.

  The pressure roller 26 has a heat-resistant elastic layer 26b having elasticity such as silicone rubber on the outer peripheral surface of a metal cored bar 26a, and a release layer 26c made of fluorine resin or the like on the surface layer. Yes. The pressure roller 26 is arranged in parallel with the fixing film 25, and both ends of the cored bar 26a are rotatably supported by a device chassis side plate (not shown). The pressure roller 26 presses the fixing film 25 against the heater 20 from below by the outer peripheral surface thereof, and fixes the unfixed toner image t on the recording material P between the fixing film 25 and a predetermined width necessary for heat fixing. A nip portion N is formed.

  As shown in FIG. 3, the distance S between the fixing nip portion N and the recording material discharge position of the transfer nip portion T is shorter than the length Ps of the recording material P in the recording material conveyance direction Y. Accordingly, the recording material P may be conveyed while being held between the fixing nip portion N and the rear end side of the transfer nip portion T in the conveyance process.

  As the fixing drive motor 29, for example, a stepping motor, a DC motor, or the like can be used. In addition to continuously rotating the pressure roller 26, it can also be intermittently performed by a predetermined angle. That is, the recording material P can be stepped while the pressure roller 26 is repeatedly rotated and stopped.

  The temperature control means 27 includes a thermistor 21 which is a temperature detection means attached to the back surface of the heater 20, and an energization control circuit unit 23 including a CPU and a memory such as a ROM or a RAM. The energization control circuit unit 23 controls the triac 24 based on the temperature of the heater 20 detected by the thermistor 21 to control the energization amount from the AC power supply 28 to the resistor pattern 20 b of the heater 20.

  In the fixing device 11, the pressure roller 26 is rotationally driven by the fixing drive motor 29 in the counterclockwise direction indicated by an arrow at a predetermined peripheral speed. A rotational force acts on the sleeve-like fixing film 25 by a pressure frictional force in the fixing nip N between the outer peripheral surface of the pressure roller 26 and the outer peripheral surface of the fixing film 25 by the rotational driving of the pressure roller 26. As a result, the fixing film 25 rotates following the clockwise direction of the arrow around the outer periphery of the heater holder 22 while the back surface slides on the lower surface of the heater 20.

  The fixing film 25 is conveyed by a predetermined peripheral speed, that is, from the transfer nip T, while being in close contact with and sliding on the lower surface of the heater 20 in the clockwise direction by the rotation driving of the pressure roller 26 at least when the unfixed toner image is fixed. The recording material P is rotationally driven without wrinkles at substantially the same peripheral speed as the conveyance speed of the recording material P to come.

  The energization control circuit unit 23 controls the triac 24 to energize the resistor pattern 20 b of the heater 20 from the AC power supply 28. As a result, the heater 20 rises in temperature, and the thermistor 21 detects the heater temperature. The energization control circuit unit 23 takes in the detected temperature of the heater 20 from the thermistor 21, controls the triac 24 based on the detected temperature, and controls the energization amount from the AC power source 28 to the resistor pattern 20b of the heater. The temperature of 20 is maintained at a predetermined fixing temperature (target temperature).

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

  Thereafter, the recording material P passes through the fixing nip portion N, is separated from the fixing film 25 and is discharged.

(3) Description of Cleaning Mode Next, the cleaning mode in this embodiment will be described.

  In the image forming apparatus according to the present embodiment, in addition to the printing operation for forming an image on the recording material P as described above, a cleaning mode for removing dirt such as toner adhering to the pressure roller 26 of the fixing device 11 is provided. Have. The cleaning mode is a mode set by a user specifying an operation panel (not shown) of the main body of the image forming apparatus or an input signal to the image forming apparatus from a host computer or the like. A cleaning operation is performed by introducing the recording material P and a cleaning sheet (hereinafter, a recording material used for cleaning is referred to as a sheet) into the fixing nip N via the transfer nip T.

  This cleaning mode is executed by the control device 30 (FIG. 1) as control means. The control device 30 includes a CPU and a memory such as a ROM or a RAM. Various programs necessary for executing the cleaning mode are stored in the memory, and the CPU executes the cleaning mode according to the various programs.

  Next, the operation in the cleaning mode in this embodiment will be described with reference to the flowchart of FIG.

  First, in the start state (S1), the fixing device 11 is in a standby state. In this state, the mode is switched to the cleaning mode by a signal from the operation panel of the main body of the image forming apparatus or the host computer (YES in S2). The image forming apparatus sequentially drives the main body drive motor 12 (S3) and then drives the fixing drive motor 29 (S4). The paper feed roller 15 starts feeding a cleaning sheet (S5) and transports the sheet. The leading edge of the sheet is nipped and conveyed between the photosensitive drum 1 and the transfer roller 5 at the transfer nip T, and is conveyed toward the fixing nip N in this state.

  Here, the time for the leading edge of the sheet to reach the fixing nip portion N is calculated from the conveying speed of the sheet and the time when the leading edge of the sheet passes the top sensor 9. Alternatively, the fixing paper discharge sensor 16 (FIG. 1) disposed downstream of the fixing device detects the leading edge of the sheet. Then, immediately after the time for the sheet leading edge to reach the fixing nip N has elapsed, or when the fixing paper discharge sensor 16 (FIG. 1) detects the sheet leading edge, it is determined that the sheet leading edge has exited the fixing nip N ( (YES in S6), the process proceeds to S7. In S7, the main body drive motor 12 and the fixing drive motor 29 are stopped in that order, and the sheet is slackened at least by the width of the fixing nip portion N between the transfer nip portion T and the fixing nip portion N, and the sheet is conveyed to that state. Stop. In this state, the front side of the sheet is nipped by the fixing film 25 and the pressure roller 26 at the fixing nip portion N, and the rear end side is nipped by the photosensitive drum 1 and the transfer roller 5 at the transfer nip portion T. In this state, an energization command signal is output to the energization control circuit unit 23 of the temperature control means 27 to turn on the energization of the heater 20 (S8), and heating in the fixing nip N is started.

  In the flowchart of FIG. 5, the heater 20 is turned on at this point, but it may be turned on before that, and further, an adhering substance such as toner on the circumferential surface of the pressure roller 26 is softened. In order to easily adhere to the cleaning sheet, the circumferential surface of the pressure roller 26 may be warmed to some extent before the sheet enters the fixing nip portion N. In this case, it is necessary to rotate the pressure roller 26 several times while the heater 20 is maintained at the same high temperature as that during printing.

  In any case, the fixing drive motor 29 is stopped (that is, the rotation of the fixing film 25 and the pressure roller 26 is stopped), the heating of the heater 20 is started, and the timer count is started (timer start). It is checked whether or not the timer time t has passed a heating time of a time t1 or more until the toner adhering to the circumferential surface of the pressure roller 26 can be softened and adhered to the sheet (S10). Alternatively, it may be determined that the temperature of the heater 20 detected by the thermistor 21 exceeds a predetermined temperature. The predetermined temperature is preferably the softening point or melting point of the toner. In this way, once the adhering matter on the circumferential surface of the pressure roller is softened, the fixing drive motor 29 is activated to convey the sheet by the width of the fixing nip N (S11). Then, the deposits are peeled off from the circumferential surface of the pressure roller 26 and transferred to the back surface of the sheet.

  In this way, by softening the toner on the circumferential surface of the pressure roller 26 while the sheet is stopped, the softened toner can enter the irregularities on the back surface of the sheet, and the circumferential surface of the pressure roller 26 can be cleaned.

  In this embodiment, the fixing drive motor 12 is driven by the fixing nip width and then stopped (S11). Thereafter, the main body drive motor 29 is driven by the nip width and stopped (S12). The operations from S9 to S13 are repeated until the fixing paper discharge sensor 16 detects that the trailing edge of the sheet exits the fixing nip portion N (S13). That is, the process returns to S9 until it is detected that the trailing edge of the sheet passes the fixing paper discharge sensor 16, resets the counter, stops the driving of the main body driving motor 29 for a predetermined time, and then returns to the trailing edge of the sheet. The operations from S10 to S13 are repeated until the end is detected by the fixing paper discharge sensor 16.

  When the trailing edge of the sheet used for cleaning exits the nip N (YES in S13), an energization stop command signal is output to the energization control circuit unit 23 of the temperature control means 27 to turn off the energization of the heater 20 (S14). Heating in the fixing nip N is stopped. Then, the main body drive motor 12 is rotated at a regular process speed (S15), and when it is determined that the discharge of the sheet from the image forming apparatus is completed (YES in S16), the cleaning mode is ended (S17).

  Next, specific examples of each member related to the cleaning mode in the image forming apparatus according to the first exemplary embodiment of the present invention will be described.

  The image forming process speed of the image forming apparatus is 200 mm / sec, and the sheet is conveyed at 200 mm / sec.

  The pressure roller 26 used in the fixing device 11 is formed with a diameter of 25 mm, a rubber thickness of the elastic layer 26 b of 3.5 mm, and a width of the fixing nip portion N of 8 mm. The distance from the transfer nip T formed by the transfer roller 5 and the photosensitive drum 1 to the fixing nip N is 130 mm. In addition, the softening point of the toner used in this embodiment is 110 ° C.

  During normal printing, the temperature of the heater 20 is controlled between 180 ° C. and 200 ° C. This is because the heater 20 is maintained at a high temperature when the pressure roller 26 is cold, and conversely, the heater 20 is controlled at a low temperature when the pressure roller 26 is warm, thereby heating the sheet. This is to keep the supply constant.

  A specific example of the cleaning mode of this embodiment will be described based on the flowchart of FIG.

  When the cleaning mode is set, the main body drive motor 12 and the fixing drive motor 29 are sequentially driven to start sheet feeding.

  When the sheet reaches the fixing nip portion N, the driving of the main body driving motor 12 and the fixing driving motor 29 is stopped, and the sheet is stopped while being sandwiched between the transfer nip portion P and the fixing nip portion N.

  In this state, heating of the heater 20 is started, and the temperature of the heater 20 is controlled to 160 ° C. This control temperature is set to a temperature higher than the softening point temperature 110 ° C. of the toner.

  Thereafter, after 1 sec has passed by the count of the timer, the driving of the fixing drive motor 29 is started, and step feeding is performed so that the sheet is conveyed by a width of 8 mm at the fixing nip portion N.

  After the step feed of the fixing drive motor 29 is completed, the main body drive motor 12 is also started to drive to feed the sheet by 8 mm.

  If the trailing edge of the sheet has not reached the fixing nip N, the counter is reset, and the steps of 1 sec stop, fixing drive motor step feed, and main body drive motor step feed are repeated sequentially.

  When the trailing edge of the sheet reaches the fixing nip N, the heating of the heater 20 is terminated, the main body drive motor 12 is normally rotated to discharge the sheet, and the cleaning mode is terminated.

  In this embodiment, when A4 size paper is used as the cleaning sheet, step feed 8 mm can be performed from the leading edge to the trailing edge of one sheet (length 297 mm), so that 37 cleaning operations can be performed. it can. By this method, 90% or more of the toner or the like adhering to the pressure roller 26 is removed, and the remaining 10% is not peeled off from the pressure roller 26 during normal image formation and adhered to the recording material. An excellent cleaning effect can be obtained.

[Comparative Example 1]
Next, as Comparative Example 1, the operation in the cleaning mode when step feed of the fixing drive motor 29 and step feed of the main body drive motor 12 are simultaneously performed will be described with reference to the flowchart of FIG.

  In Comparative Example 1, the operations from S101 to S110 are the same as the operations from S1 to S10 in the cleaning mode of this embodiment, but the subsequent operations, that is, the main body drive motor 12 and the fixing drive motor 12 are simultaneously fixed to the fixing nip width. The operation of stopping after driving for a minute (S111) is different from the cleaning mode of this embodiment. The operations from S112 to S116 are the same as the operations from S13 to S17 in the cleaning mode of this embodiment.

  As a specific example, the driving of the main body driving motor 12 and the fixing driving motor 29 is stopped in a state where the sheet is sandwiched between the transfer nip portion T and the fixing nip portion N, and heating of the heater 20 is started in this state, The temperature of the heater 20 is controlled to 160 ° C. Thereafter, after 1 second has elapsed due to the count of the timer, the driving of the main body driving motor 12 and the fixing driving motor 29 is started simultaneously, and step feeding is performed so that the sheet is conveyed by a width of 8 mm at the fixing nip portion N. If the trailing edge of the sheet has not reached the fixing nip N, the counter is reset, stopped for 1 second, and step feeds of the main body driving motor 12 and the fixing driving motor 29 are sequentially repeated. When the trailing edge of the sheet reaches the fixing nip portion N, the heating of the heater 20 is terminated, the main body drive motor 12 is normally rotated to discharge the sheet, and the cleaning mode is terminated.

  In the first comparative example, in the step feeding process in the cleaning mode, the main body drive motor 12 and the fixing drive motor 29 are simultaneously started, so that the drive start currents flowing through the two motors 12 and 29 are instantaneously overlapped and large. Current flows through the device and the motor drive becomes unstable. Further, when dealing with the instantaneous motor start-up current, it is necessary to increase the capacity of the power source of the image forming apparatus, and the size of the image forming apparatus is increased.

[Comparative Example 2]
Next, as Comparative Example 2, the operation of the configuration in which only the fixing drive motor 29 is driven at the time of step feeding in the cleaning mode will be described with reference to the flowchart of FIG.

  Also in Comparative Example 2, the operations from S121 to S125 are the same as the operations from S1 to S5 in the cleaning mode of the present embodiment. The operations from S132 to S136 are the same as the operations from S13 to S17 in the cleaning mode of this embodiment.

  In Comparative Example 2, the time when the sheet trailing edge exits the transfer nip T formed by the transfer roller 5 and the photosensitive drum 1 is calculated from the sheet conveyance speed and the time when the sheet leading edge passes the top sensor 9. To do. After detecting that the trailing edge of the sheet has exited the transfer nip T (S126), the driving of the main body driving motor 12 and the fixing driving motor 29 is stopped (S127), the heater is heated (S128), the timer is reset, and the timer is started (S129). ), T> ≧ t1? After performing the various operations in (S130), the step driving operation of the fixing drive motor 29 is performed (S131). This is a configuration in which the starting current flowing in the apparatus is reduced by not driving the main body drive motor during step feeding. In this configuration, since the sheet cannot be conveyed by the fixing drive motor 29 when the sheet is sandwiched in the transfer nip T, the rear end of the sheet is the transfer roller 5 upstream of the fixing device 11 in the recording material conveyance direction Y, that is, the transfer nip. After passing through T, the stepping operation of the fixing drive motor 29 is performed.

  A specific example of Comparative Example 2 is shown. When the trailing edge of the sheet exits the transfer nip T, the driving of the main body driving motor 12 and the fixing driving motor 29 is stopped. The pressure roller 26 and the fixing film 25 are stopped in a state where the sheet is sandwiched between the fixing nips N. In this state, heating of the heater 20 is started, and the temperature of the heater 20 is controlled to 160 ° C. Thereafter, after 1 sec has passed by the count of the timer, the driving of the fixing drive motor 29 is started, and step feeding is performed so that the sheet is conveyed by a width of 8 mm at the fixing nip portion N. If the trailing edge of the sheet has not reached the fixing nip N, the counter is reset, and the steps of stopping for 1 second and fixing the driving motor step are repeated. When the trailing edge of the sheet reaches the fixing nip N, the heating of the heater 20 is terminated, the main body drive motor 12 is normally rotated to discharge the sheet, and the cleaning mode is terminated.

  In this comparative example 2, when A4 size paper is used for the cleaning sheet, the transfer nip T and the fixing nip T are performed because a step feed operation (8 mm) is performed after the trailing edge of the sheet passes through the transfer nip T. Step feed is possible in an area of 130 mm from N. Therefore, 16 cleaning operations can be performed on one sheet.

  In this method, since the cleaning operation cannot be performed on the entire sheet, the cleaning frequency is reduced with respect to the cleaning frequency of 37 in the operation of Embodiment 1 of the present invention, and the cleaning efficiency of one sheet is decreased. Further, in order to obtain the same cleaning effect, cleaning with a plurality of sheets is required, and the time required for cleaning and a sheet such as paper used for cleaning are required.

  In the first embodiment, the driving of the main body driving motor 12 is started after the driving of the fixing driving motor 29 is finished during the cleaning operation of the fixing device 11 so that the driving start timings of the two driving motors 12 and 29 do not coincide with each other. ing. Therefore, since the starting currents generated when the two drive motors 12 and 29 are started do not coincide with each other, the sum of the starting currents by the motors of the entire image forming apparatus can be reduced.

  In addition, the cleaning operation can be performed from the leading edge to the trailing edge of the sheet to be cleaned, and the cleaning operation can be effectively performed by securing the cleaning operation area in one sheet.

[Embodiment 2]
The second embodiment of the present invention will be described below.

  Since the configurations and dimensional relationships of the toner, the image forming apparatus, and the fixing device used in this embodiment are the same as those in the first embodiment, the description thereof will be omitted.

  Next, the cleaning mode in the second embodiment will be described with reference to the flowchart of FIG. The difference from the first embodiment is that heating of the heater 20 is stopped at the start (start) of step feed of the main body drive motor 12 and the fixing drive motor 29.

  In the cleaning mode of this embodiment, the operations from S21 to S30 are the same as the operations from S1 to S10 in the first embodiment.

  After softening the deposit on the circumferential surface of the pressure roller in S30, the process proceeds to S31 when the time t of the timer has passed the heating time of time t1 or more.

  In S <b> 31, an energization stop command signal is output to the energization control circuit unit 23 of the temperature control means 27 to turn off the energization of the heater 20 and stop the heating in the fixing nip N. Then, it waits for the temperature of the heater 20 to become lower than a predetermined temperature (target temperature). The predetermined temperature may be any temperature that lowers the toner temperature below the softening point, and may be the softening point. Here, it is determined whether or not the timer count has exceeded a predetermined t2 (a time during which the timer falls below the predetermined temperature (target temperature)) (S32). t2 is a count corresponding to a temperature range in which the temperature of the heater 20 decreases from a predetermined temperature to the softening point temperature of the toner. The determination may be made based on whether the temperature detected by the thermistor 21 is a predetermined temperature lower than the softening point of the toner.

  When the timer counter t exceeds t2 (YES in S32), the fixing drive motor 29 is activated to convey the sheet by the width of the fixing nip portion N (S33). Then, the deposits are peeled off from the circumferential surface of the pressure roller 26 and transferred to the back surface of the sheet.

  As described above, by softening the toner on the circumferential surface of the pressure roller 26 while the sheet is stopped, the softened toner can enter the unevenness on the back surface of the sheet, and the entire circumferential surface of the pressure roller 26 can be cleaned.

  Thereafter, the fixing drive motor 12 is driven by the fixing nip width and then stopped (S33). Then, the main body drive motor 29 is driven and stopped by the nip width until the fixing sheet discharge sensor 16 detects that the trailing edge of the sheet exits the fixing nip portion N (S35). That is, if the trailing edge of the sheet is not detected by the fixing paper discharge sensor 16, the process returns to S28, the heater 20 is heated again, and the counter is reset. The operations from S28 to S35 are repeated until the trailing edge of the sheet is detected by the fixing paper discharge sensor 16.

  When the trailing edge of the sheet used for cleaning exits the fixing nip portion N (YES in S34), the main body drive motor 12 is rotated at a regular process speed (S36), and the discharge of the sheet from the fixing nip portion N is completed. If determined (YES in S37), the cleaning mode is terminated (S38).

  Since specific examples of the members related to the cleaning mode of the image forming apparatus according to the second embodiment of the present embodiment are the same as those of the first embodiment, the description thereof will be omitted.

  A specific example of the cleaning mode of this embodiment will be described based on the flowchart of FIG.

  When the cleaning mode is set, the main body drive motor 12 and the fixing drive motor 29 are sequentially driven to start sheet feeding.

  When the sheet reaches the fixing nip portion N, the driving of the main body driving motor 12 and the fixing driving motor 29 is stopped, and the sheet is stopped while being sandwiched between the transfer nip portion T and the fixing nip portion.

  In this state, heating of the heater 20 is started, and the temperature of the heater 20 is controlled to 160 ° C. This control temperature is set to a temperature higher than the softening point temperature 110 ° C. of the toner. Thereafter, the heating of the heater 20 is stopped after 1 second has elapsed from the count of the timer.

  Thereafter, the timer waits for 3.5 seconds, and waits for the temperature of the toner in the fixing nip N to decrease.

  Thereafter, driving of the fixing drive motor 29 is started, and step feeding is performed so that the sheet is conveyed by a width of 8 mm at the fixing nip portion N.

  If the trailing edge of the sheet has not reached the fixing nip N, the main body drive motor 12 is also started to perform step feed so as to convey the sheet by 8 mm.

  After that, the heater 20 is heated for 1 sec, the heating of the heater 20 is stopped, and the process waits for the temperature of the heater 20 to decrease, and the steps of step feed of the fixing drive motor 29 and step feed of the main body drive motor 12 are sequentially repeated. .

  When the trailing edge of the sheet reaches the fixing nip portion N, the main body drive motor 12 is normally rotated to discharge the sheet, and the cleaning mode ends.

  In this embodiment, when A4 size paper is used as the cleaning sheet, step feed 8 mm can be performed from the leading edge to the trailing edge of one sheet (length 297 mm), so that 37 cleaning operations can be performed. it can. By this method, 98% or more of dirt such as toner adhered to the pressure roller 26 is removed, and the remaining 2% is not peeled off from the pressure roller 26 during normal image formation and adhered to the recording material. An excellent cleaning effect can be obtained.

  In this embodiment, in the cleaning mode of the fixing device 11, the heating of the heater 20 is stopped and then the driving of the fixing driving motor 29 is started, and then the driving of the main body driving motor 12 is started. The drive start timings of the drive motors 29 and 12 are not matched. Therefore, the current flowing through the heater 20 due to the heating of the heater 20 and the starting current generated when the two drive motors 29 and 12 are started do not coincide with each other, thereby reducing the total current of the entire image forming apparatus. Can do.

  In addition, the cleaning operation can be performed from the leading edge to the trailing edge of the sheet to be cleaned, and the cleaning operation can be effectively performed by securing the cleaning operation area in one sheet. Further, in order to cool after the adhering matter such as toner is softened in the stop state of the fixing device 11 (non-drive state of the fixing drive motor 29), based on the difference in surface roughness and surface energy between the pressure roller 26 and the sheet, The deposit adheres more firmly to the sheet than the pressure roller 26. Therefore, a further cleaning effect can be obtained.

[Embodiment 3]
The third embodiment of the present invention will be described below.

  Since the configurations and dimensional relationships of the toner, the image forming apparatus, and the fixing device used in this embodiment are the same as those in the first embodiment, the description thereof will be omitted.

  Next, the cleaning mode in the third embodiment will be described with reference to the flowchart of FIG. The difference from the first embodiment is that heating of the heater 20 is stopped at the start (drive) of the step feed of the main body driving motor 12 and the fixing driving motor 29, and the heating of the heater 20 is stopped. There is a difference in that step feeding of the main body drive motor 12 is performed during the standby time until the temperature of the temperature 20 decreases.

  In the cleaning mode of this embodiment, the operations from S41 to S50 are the same as the operations from S1 to S10 in the first embodiment.

  After the adhering matter on the peripheral surface of the pressure roller is softened in S50, the process proceeds to S51 when the timer time t has exceeded the heating time t1.

  In S <b> 51, an energization stop command signal is output to the energization control circuit unit 23 of the temperature control means 27 to turn off the energization of the heater 20 and stop the heating in the fixing nip N. Then, it waits for the temperature of the heater 20 to become lower than a predetermined temperature (target temperature). The predetermined temperature may be any temperature that lowers the toner temperature below the softening point, and may be the softening point. Here, it is determined whether or not the count of the timer has exceeded a predetermined t2 (a time during which the timer falls below a predetermined temperature (target temperature)) (S53). t2 is a count corresponding to a temperature range in which the temperature of the heater 20 decreases from a predetermined temperature to the softening point temperature of the toner. Until the temperature is lowered, the main body drive motor 29 is driven by the nip width and stopped (S52). The determination may be made based on whether the temperature detected by the thermistor 21 is a predetermined temperature lower than the softening point of the toner.

  When the timer counter t exceeds t2 (YES in S53), the fixing drive motor 29 is activated to convey the sheet by the width of the fixing nip portion N (S54). Then, the deposits are peeled off from the circumferential surface of the pressure roller 26 and transferred to the back surface of the sheet.

  As described above, by softening the toner on the circumferential surface of the pressure roller 26 while the sheet is stopped, the softened toner can enter the unevenness on the back surface of the sheet, and the entire circumferential surface of the pressure roller 26 can be cleaned.

  The operation from S48 to S54 is repeated until the fixing paper discharge sensor 16 detects that the trailing edge of the sheet exits the fixing nip N (S55). That is, if the trailing edge of the sheet is not detected by the fixing paper discharge sensor 16, the process returns to S48, the heater 20 is heated again, and the counter is reset. The operations from S48 to S54 are repeated until the trailing edge of the sheet is detected by the fixing paper discharge sensor 16.

  When the trailing edge of the sheet used for cleaning exits the fixing nip portion N (YES in S55), the main body driving motor 12 is rotated at a regular process speed (S56), and the discharge of the sheet from the fixing nip portion N is completed. If it is determined (YES in S57), the cleaning mode is terminated (S58).

  Next, the specific examples of the members related to the cleaning mode of the image forming apparatus according to the third embodiment of the present embodiment are the same as those of the first embodiment, so that the description thereof is omitted.

  A specific example of the cleaning mode of this embodiment will be described based on the flowchart of FIG.

  When the cleaning mode is set, the main body driving motor 12 and the fixing driving motor 29 are sequentially started to start sheet feeding.

  When the sheet reaches the fixing nip portion N, the driving of the main body driving motor 12 and the fixing driving motor 29 is stopped, and the sheet is stopped while being sandwiched between the transfer nip portion T and the fixing nip portion.

  In this state, the heating of the heater 20 is started, the temperature of the heater 20 is controlled to 160 ° C., and the heating of the heater 20 is stopped after 1 second has elapsed by the timer count. This control temperature is set to a temperature higher than the softening point temperature 110 ° C. of the toner.

  Thereafter, the main body drive motor 12 is driven to perform step feed so as to convey the sheet by 8 mm. Further, after 3.5 seconds have elapsed from the count of the timer, the fixing drive motor 29 is also started to drive, and step feeding is performed so that the sheet is conveyed by a width of 8 mm at the fixing nip portion N.

  When the trailing edge of the sheet has not reached the fixing nip portion N, the heater 20 is heated for 1 second, the heating of the heater 20 is stopped, the step feed of the main body drive motor 12, and the step feed of the fixing drive motor 29. The process is repeated sequentially.

  When the trailing edge of the sheet reaches the fixing nip portion N, the main body drive motor 12 is normally rotated to discharge the sheet, and the cleaning mode ends.

  In this embodiment, when A4 size paper is used as the cleaning sheet, step feed 8 mm can be performed from the leading edge to the trailing edge of one sheet (length 297 mm), so that 37 cleaning operations can be performed. it can. By this method, 98% or more of the dirt such as toner adhering to the pressure roller 26 is removed, and the remaining 2% may be peeled off from the pressure roller 26 and adhered to the recording material P during normal image formation. And an excellent cleaning effect can be obtained.

  In this embodiment, in the cleaning mode of the fixing device 11, after the heating of the heater 20 is stopped, the driving of the main body driving motor 12 is started, and then the driving of the fixing driving motor 29 is started. The drive start timings of the two drive motors 12 and 29 are not matched. Therefore, since the current flowing through the heater 20 with the heating of the heater 20 does not coincide with the starting current generated when the two drive motors 12 and 29 are started, the total current of the entire image forming apparatus can be reduced. it can.

  In addition, the cleaning operation can be performed from the leading edge to the trailing edge of the sheet to be cleaned, and the cleaning operation can be effectively performed by securing the cleaning operation area in one sheet. In addition, since the adhering material such as toner is softened after the fixing device 11 is stopped (the fixing driving motor 29 is not driven), the cooling is performed based on the difference in surface roughness and surface energy between the pressure roller 26 and the sheet. The deposit adheres more firmly to the sheet than the pressure roller 26. Therefore, a further cleaning effect can be obtained.

  In Embodiment 3 of the present embodiment, since the main body drive motor 12 is stepped during the standby time for cooling the fixing device 11, the cleaning mode time can be shortened.

1 is an overall configuration diagram of an example of an image forming apparatus according to the present invention. FIG. 3 is a structural model diagram of an example of a fixing device. The enlarged model figure of the fixing nip part. 4 is an explanatory diagram of a dimensional relationship between a distance between a fixing nip portion and a recording material discharge position of a transfer nip portion and a length of a recording material P. FIG. The flowchart which shows the cleaning operation | movement which concerns on the form 1 of the Example of this invention. 9 is a flowchart showing a cleaning operation according to Comparative Example 1. 9 is a flowchart showing a cleaning operation according to Comparative Example 2. The flowchart which shows the cleaning operation | movement which concerns on the form 2 of the Example of this invention. 10 is a flowchart showing a cleaning operation according to Embodiment 3 of the embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Photosensitive drum, 5 ... Transfer roller, 9 ... Top sensor, 11 ... Fixing device,
12 ... Main body drive motor, 16 ... Fixing paper discharge sensor, 20 ... Heater,
21 ... Thermistor, 26 ... Pressure roller, 29 ... Fixing drive motor,
30 ... Control device, N ... Fixing nip, A ... Transfer nip

Claims (3)

An image carrier that is driven to rotate, a transfer member that contacts the image carrier to form a transfer nip portion, a rotating member that contacts each other to form a fixing nip portion, and a heat generator that generates heat when energized to heat the rotor And a heating member. The recording material is nipped and conveyed at the transfer nip portion, and the developer image carried by the image carrier is transferred to the recording material by the transfer member. The recording material is sandwiched at the fixing nip portion together with the transfer nip portion. In an image forming apparatus that conveys and heats a developer image through a rotating body to heat and fix it on a recording material.
Image carrier driving means for rotationally driving the image carrier;
A rotating body driving means for rotating the rotating body;
Control means for controlling on / off of energization to the heating body and controlling driving of the image carrier driving means and the rotating body driving means;
A cleaning mode in which the heating member is energized with the cleaning sheet held between the transfer nip portion and the fixing nip portion, and the driving and stopping of the image carrier driving unit and the rotating unit driving unit are repeated.
Have
In the cleaning mode, the control means starts driving the image carrier driving means and the rotating body driving means at different timings. An image carrier that is driven to rotate, a transfer member that contacts the image carrier to form a transfer nip portion, a rotating member that contacts each other to form a fixing nip portion, and a heat generator that generates heat when energized to heat the rotor And a heating member. The recording material is nipped and conveyed at the transfer nip portion, and the developer image carried by the image carrier is transferred to the recording material by the transfer member. The recording material is sandwiched at the fixing nip portion together with the transfer nip portion. In an image forming apparatus that conveys and heats a developer image through a rotating body to heat and fix it on a recording material.
Image carrier driving means for rotationally driving the image carrier;
A rotating body driving means for rotating the rotating body;
Control means for controlling on / off of energization to the heating body and controlling driving of the image carrier driving means and the rotating body driving means;
Cleaning mode that repeats driving and stopping of the image carrier driving means and rotating body driving means by turning on / off the power to the heating body with the cleaning sheet held between the transfer nip part and the fixing nip part. When,
Have
In the cleaning mode, the control unit turns off the energization to the heating body, and starts driving the image carrier driving unit and the rotating body driving unit at different timings.   The image forming apparatus according to claim 1, wherein a distance between the transfer nip portion and the fixing nip portion is shorter than a length in a sheet conveyance direction.

Images