JP2008015412A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent an image carrier and a recording material conveying member from being damaged when a rotating body is cleaned. <P>SOLUTION: A temperature control means 41 performs control to start heating of a heating body 43 in a cleaning mode for cleaning the rotating body 22. Furthermore, a driving control means 51 controls driving of first driving means 52 (Y to K) and a second driving means 53 so that sheet Pc for cleaning is conveyed by the recording material conveying member 7 to a fixing nip part N. In addition, driving of a transfer material driving means 55 is controlled so that transfer members 5 (Y to K) are moved and the recording material conveying member is separated from the image carrier. Moreover, driving of a third driving means 54 is controlled so that the sheet held in the fixing nip part N is conveyed while repeating rotating and stopping by the rotating bodies 22 and 21. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as an electrophotographic copying machine or an electrophotographic printer.

  As an image heating device (fixing device) mounted on an electrophotographic printer or copying machine, a heater having an energizing heating element on a ceramic substrate, a flexible member that moves while contacting the heater, and a flexible member Some of them have a heater and a pressure roller that forms a nip portion. Patent Documents 1 and 2 describe this type of fixing device. The recording material carrying the unfixed toner image is heated while being nipped and conveyed by the nip portion of the fixing device, whereby the image on the recording material is heated and fixed on the recording material. This fixing device has an advantage that the time required for starting energization of the heater and raising the temperature to the fixable temperature is short. Accordingly, a printer equipped with this fixing device can shorten the time (FPOT: first printout time) after the print command is input until the first image is output. This type of fixing device also has an advantage that power consumption during standby for waiting for a print command is small.

  In the fixing device described above, it is ideal that all of the unfixed toner images carried on the recording material are appropriately heated and melted and fixed on the recording material. However, a cold offset toner that does not melt, a hot offset toner that melts too much, a toner that is electrostatically offset to the flexible member, and the like may exist on the recording material. In that case, the hot offset toner is transferred to a flexible member in contact with the recording material, and the toner transferred to the flexible member is moved to the outer peripheral surface (surface) of the pressure roller through the nip portion by the movement of the flexible member. ). Since the pressure roller is not heated except when the heater is energized, the toner transferred to the surface of the pressure roller is not melted and is almost fixed on the surface of the pressure roller.

  Patent Documents 3 and 4 describe methods for cleaning the surface of the pressure roller.

  In Patent Document 3, the heater is energized in a state where the cleaning sheet is sandwiched in the fixing nip, and the step roller that rotates the pressure roller by the amount corresponding to the fixing nip after melting the toner on the surface of the pressure roller, The surface of the pressure roller is cleaned with a sheet.

When the above-mentioned step feed cleaning is performed by an image forming apparatus using separate drive motors for the photosensitive drum as an image carrier provided in the image forming unit and the fixing device, the sheet feed amount due to the difference in starting characteristics of each drive motor Make a difference. In such a case, Patent Document 4 proposes a method for preventing sheet pulling between the photosensitive drum and the fixing device and the accompanying step-out or breakage of the drive motor / gear. That is, at the time of step feeding of the pressure roller, the driving time of the photosensitive drum driving motor is made longer than the driving time of the fixing device driving motor. As a result, the sheet feeding amount on the photosensitive drum side is made larger than the sheet feeding amount on the fixing device side to prevent the sheet from being attracted between the photosensitive drum and the fixing device.
JP-A-63-313182 JP-A-4-44075 JP 2000-47509 A JP 2003-295731 A

  By the way, as an electrophotographic color image forming apparatus, a toner formed on a plurality of photosensitive drums is transferred onto a recording material conveyed by an electrostatic conveyance belt, thereby forming a multicolor image on the recording material. A direct transfer multicolor image forming apparatus has been put into practical use.

  In many cases, the color image forming apparatus is provided with a drive motor for each of an electrostatic conveyance belt and a plurality of photosensitive drums from the viewpoint of the response to an increase in the drive torque of the apparatus main body and the merit of independent drive control.

  In the above-described color image forming apparatus, when performing step feed cleaning as described above, due to variations in the starting characteristics between the drive motors respectively provided on the plurality of photosensitive drums, an inquiry of the recording material between the photosensitive drums, Excessive press-in of the recording material occurs. In the case of inquiries, there is a risk that the drive motor / gear may be stepped out or damaged, and the outer peripheral surface (surface) of the photosensitive drum and the electrostatic conveyance belt may be damaged. In the case of excessive push-in, there is a risk that the recording material will be wrinkled and the surface of the photosensitive drum and the electrostatic conveyance belt may be damaged by the wrinkle of the recording material.

  In addition, there is a possibility that a difference occurs in the step feed amount of the recording material due to a difference in starting characteristics between the drive motor on the photosensitive drum side and the drive motor on the electrostatic conveyance belt side, and the photosensitive drum and the electrostatic conveyance belt surface may be damaged.

  The method proposed in Patent Document 4 only prevents paper inquiries between the photosensitive drum and the fixing device, and does not consider the above-described problems.

  An object of the present invention is to provide an image forming apparatus capable of preventing the image carrier and the recording material conveying member from being damaged when the rotating body is cleaned.

A typical configuration of an image forming apparatus according to the present invention includes a rotatable image carrier that carries a developed image, a first drive unit that rotationally drives the image carrier, and a recording that faces the image carrier. A rotatable recording material conveying member for conveying the material; a second driving means for rotationally driving the recording material conveying member; and a transfer member for forming a transfer nip portion with the recording material conveying member sandwiched between the image carrier. Two rotating bodies that contact each other to form a fixing nip portion, a third driving unit that rotationally drives any of the rotating bodies, and a heating body that heats any of the rotating bodies. Then, the development image is transferred by the transfer member at the transfer nip portion to the recording material conveyed by the recording material conveyance member, and the recording material onto which the development image has been transferred is sandwiched and conveyed by the fixing nip portion, and the heat of the heating body Image forming apparatus for fixing a developed image on a recording material In,
Transfer member moving means for moving the transfer member so as to separate or contact the recording material conveying member with the image carrier;
Drive control means for controlling the drive of the first, second and third drive means and for controlling the drive of the transfer member drive means;
Temperature control means for controlling the heating body; and
Have
In the cleaning mode in which the rotating body is cleaned, the temperature control means performs control to start heating the heating body, and the drive control means causes the recording material conveying member to feed a cleaning sheet to the fixing nip. The transfer member controls the drive of the first drive means and the second drive means so as to be conveyed to a portion, and moves the transfer member to separate the recording material conveyance member from the image carrier. The driving of the third driving unit is controlled so as to control the driving of the driving unit and to convey the sheet held by the fixing nip portion while being repeatedly rotated and stopped by the rotating body. An image forming apparatus.

  According to the image forming apparatus of the present invention, the recording material conveying member is separated from the image carrier and the cleaning sheet is conveyed while being repeatedly rotated and stopped by the rotating body. It is possible to prevent the image carrier and the recording material conveying member from being damaged.

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

(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. This image forming apparatus is an electrophotographic color image forming apparatus (full color laser beam printer).

  The color image forming apparatus shown in this embodiment forms a toner image as a developed image on a plurality of drum type electrophotographic photosensitive members as an image carrier, and the toner images are conveyed by an electrostatic conveyance belt. A direct transfer multicolor image forming apparatus that forms a multicolor image by transferring to a material.

  The color image forming apparatus according to the present exemplary embodiment forms first to fourth toner images of each color of yellow Y, magenta M, cyan C, and black K on the apparatus main body 101 constituting the housing of the color image forming apparatus. It has four image forming stations SY, SM, SC, and SK. The station S (Y to K) has a drum-shaped electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) 1 (Y to K) as an image carrier. Around the photosensitive drum 1 (Y to K), a charging roller 2 (Y to K) as a charging unit, a laser scanner unit 3 (Y to K) as an exposure unit, and a developing device 4 (developing unit) ( Y to K) and a cleaning device 5 (Y to K) as a cleaning means. An electrostatic transportation belt (recording material conveying means) 7 is provided so as to face the photosensitive drum 1 (Y to K) of the station S (Y to K). The conveyor belt 7 is stretched around three axes of a driving roller 8a and driven rollers 8b and 8c. The transfer roller 5 (Y to K) is disposed so as to face the photosensitive drum 1 (Y to K) with the conveying belt 7 interposed therebetween, whereby the outer peripheral surface (front surface) of the photosensitive drum 1 (Y to K) and the conveying belt 7 are arranged. A transfer nip portion T (Y to K) is formed between the outer peripheral surfaces (surfaces) of the sheet. A suction roller (electrostatic transfer member) 9 is provided in the vicinity of the driven roller 8b so as to face the surface of the conveyance belt 7. A bias is applied to the suction roller 9 during image formation. By applying an electric charge to the recording material P by this applied bias, the recording material P is electrostatically attracted to the conveyance belt 7.

  Each member will be described in more detail.

  The photosensitive drum 1 (Y to K) is rotationally driven at a predetermined peripheral speed V1 [mm / s] (process speed) in the clockwise direction of the arrow. The photosensitive drum 1 (Y to K) is a negatively charged OPC photosensitive member having a diameter of 30 mm. The process speed of the color image forming apparatus of this embodiment is 180 mm / sec.

The charging roller 2 (Y to K) is a roller having an actual resistance of 1 × 10 ⁶ Ω to which a DC voltage of −1.2 kV is applied from a power source (not shown). The charging method is a DC contact charging method in which charging is performed by contacting the surface of the photosensitive drum 1 so as to be driven and rotated at a total pressure of 9.8 N. The surface of the photosensitive drum 1 is charged to −600V.

  The scanner unit 3 (Y to K) is a polygon scanner using a laser diode, and forms an image of a laser beam modulated by an image signal on the surface of the photosensitive drum 1 (Y to K) through a lens group, thereby forming an electrostatic latent image. Form an image. Writing of laser exposure is performed by delaying a predetermined time from a position signal in a polygon scanner called BD for each scanning line in the main scanning direction (bus line direction of the photosensitive drum). In the sub-scanning direction (circumferential direction of the photosensitive drum), it is delayed by a predetermined time from the TOP signal (detection signal) starting from the top sensor (recording material detection means) Sa. Thus, the station S (Y to K) is configured such that exposure can always be performed at the same position on the recording material P.

  The developing device 4 (Y to K) stores yellow Y, magenta M, cyan C, and black K toners. These toners are so-called non-mag toners that do not contain a magnetic material, and develop a latent image by a one-component contact development method. The developing device 4 (Y to K) includes a developing sleeve 4 (Ya to Ka) disposed so as to face the surface of the photosensitive drum 1 (Y to K) and a developing blade (not shown). The developing blade coats toner on the outer peripheral surface (surface) of the developing sleeve 4 (Ya to Ka). The developing sleeve 4 (Ya to Ka) is driven to rotate at a constant speed with the photosensitive drum 1 (Y to K), and a bias of about −500 V is applied from a power source (not shown), and toner is supplied from the surface of the developing sleeve 4 (Ya to Ka). Is transferred to the surface of the photosensitive drum 1 (Y to K) to develop the electrostatic latent image.

  The conveyor belt 7 is grounded via a driving roller 8a and driven rollers 8b and 8c. As the driving roller 8a rotates, the conveyor belt 7 is rotationally driven in a counterclockwise direction indicated by an arrow at a predetermined peripheral speed V2 [mm / s] corresponding to the rotational peripheral speed of the photosensitive drum 1 (Y to K).

The transfer roller 5 (Y to K) includes a metal core 5 (Ya to Ka) and conductive rubber 5 (Yb to Kb) provided on the outer peripheral surface of the core 5 (Ya to Ka). (FIG. 5). As the conductive rubber 5 (Yb to Kb), epichlorohydrin rubber capable of applying a high voltage adjusted to a volume resistivity of 1 × 10 ⁷ Ωcm is used.

  The transport belt 7, the driving roller 8 a and the driven rollers 8 b and 8 c, and the transfer roller 5 (Y to K) are integrated as a transport belt unit (hereinafter referred to as an ETB unit) 16. The ETB unit 16 is rotatably provided in the apparatus main body 101 so that the transport belt 7 is separated from or contacts the photosensitive drum 1 (Y to K) of the station S (Y to K). The configuration of the ETB unit 16 will be described in detail in section (3) below.

The suction roller 9 is a solid rubber roller having a diameter of 12 mm in which carbon black is dispersed in EPDM rubber for resistance adjustment. The suction roller 9 can be configured to apply a bias for suction to a metal core 9a (FIG. 5). Yes. The suction roller 9 is applied with a voltage of +1 KV as a bias during image formation. The resistance value of the suction roller 9 is adjusted to 1 × 10 ⁶ Ω when a metal foil having a width of 1 cm is wound around the outer periphery of the roller and a voltage of 500 V is applied between the core metal 9a.

  When the image forming apparatus according to the present exemplary embodiment captures a print signal (print signal), the image forming apparatus executes a predetermined image formation control sequence and starts an image forming operation. Reference numeral 51 denotes a rotation drive control unit (drive control means) that controls the rotation drive system of the image forming apparatus. The drive control unit 51 includes a CPU and a memory such as a RAM and a ROM. The memory stores a drive control sequence for image formation, a drive control sequence for a cleaning mode for cleaning the image heating and fixing device (fixing device) 13, and the like. When the drive control unit 51 takes in the print signal S1, the photosensitive drum motor (first driving means) 52 (Y to K) (FIG. 6) is rotationally driven to rotate the photosensitive drum 1 (Y to K). As a result, the photosensitive drum 1 (Y to K) is rotated in the direction of the arrow at a predetermined peripheral speed (process speed) (FIG. 1). At the same time, the drive control unit 51 rotates the drive roller 8a by rotationally driving a conveyor belt motor (hereinafter referred to as an ETB motor) (second drive means) 53 (FIG. 6). As a result, the conveyor belt 7 is rotated in the direction of the arrow at a peripheral speed corresponding to the rotational peripheral speed of the photosensitive drum 1 (Y to K) (FIG. 1).

  First, in the first color yellow Y station SY, the surface of the photosensitive drum 1Y is uniformly charged to a predetermined polarity and potential by the charging roller 2Y. Next, the scanner unit 3Y scans and exposes the surface of the photosensitive drum 1Y with a laser beam corresponding to the image information. As a result, an electrostatic latent image corresponding to the image information is formed on the surface of the uniformly charged photosensitive drum 1Y. The latent image is developed with yellow toner by the developing device 4Y, and a yellow toner image (developed image) is formed on the surface of the photosensitive drum 1Y. 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 (Y to K) of each station S (Y to K).

  On the other hand, the recording material P stacked and stored in the feeding cassette 10 is sent to the registration roller pair 12 by the pickup roller 11. Next, the recording material P is transported between the transport belt 7 and the suction roller 9 by the roller pair 12. The recording material P receives charges from the suction roller 9 and is electrostatically attracted to the surface of the conveying belt 7. The bias applied to the transfer roller 51 is calculated from the impedance of the conveyance belt 7 calculated from the current flowing through the suction roller 9 in the conveyance process of the recording material P and the impedance of the recording material P. In the present embodiment, in the single-sided printing in the normal environment, a DC bias of about +1.5 kV is applied from the power source to each station S (Y to K).

  The recording material P adsorbed on the surface of the transport belt 7 is transported in the order of stations SY, SM, SC, and SK as the transport belt 7 rotates. In the conveyance process of the recording material P, the toner image on the surface of the photosensitive drum 1 (Y to K) is transferred to the transfer roller 5 (Y to K) by the transfer unit T (Y to K) of each station S (Y to K). The recording material P is sequentially transferred onto the recording material P by the applied bias. The recording material P is separated from the conveyor belt 7 in the vicinity of the driving roller 8a and is conveyed to an image heating fixing device (fixing device) 13.

  As the recording material P passes through the fixing device 13, the toner image is heated and fixed on the recording material P. The recording material P exiting the fixing device 13 is discharged as a printed matter to a discharge tray 15 at the top of the apparatus main body 101 by a discharge roller pair 14.

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

(2) Fixing device 13
In the following description, with respect to the fixing device and its constituent members, the longitudinal direction means a direction orthogonal to the recording material conveyance direction on the surface of the recording material. The width direction (short direction) refers to the recording material conveyance direction on the surface of the recording material. The width means a dimension in the recording material conveyance direction.

  FIG. 2 is a schematic longitudinal sectional view of the fixing device 13. FIG. 3 is a front model view of the fixing device 13. FIG. 4 is an explanatory diagram of the heater.

  The fixing device 13 is a cylindrical fixing film (first rotating body) 21 having flexibility as two rotating bodies that are in contact with each other to form the fixing nip portion N, and is fixed in contact with the film 21. And an elastic pressure roller (second rotating body) 22 that forms the nip portion N. The fixing device 13 includes a ceramic heater (heating member) 23 for heating the film 21, a heater holder (heating member holding member) 24 for holding the heater 23, and a fixing flange (regulating member) for restricting movement of the film 21 in the longitudinal direction. ) 25a and 25b. The film 21, the pressure roller 22, the heater 23, and the holder 24 are all elongated members in the longitudinal direction.

  The heater 23 has a heat-resistant substrate 23a such as alumina elongated in the longitudinal direction, and a resistor pattern (electric heating element) 23b is formed along the longitudinal direction on one surface (heater surface) of the substrate 23a. Then, energizing electrode portions 23c are formed at both ends of the pattern 23b. A glass layer is formed on one surface of the substrate 23a as a protective layer 23d for protecting the pattern 23b so as to cover the pattern 23b. The heater 2 is formed so that the heat generation area of the pattern 23 b is larger than the maximum width of the recording material P introduced into the fixing nip portion N.

  The holder 24 is formed in a vertical cross-sectional saddle shape with heat-resistant resin, and is disposed in the film 21. In the holder 24, the substrate 23a of the heater 23 is held in a groove provided at the center of the lower surface in the width direction with the glass layer 23c facing downward. The holder 24 not only holds the heater 23 but also serves as a guide function for guiding the rotation of the film 21.

  The film 21 is loosely fitted on the holder 24 holding the heater 23 with a sufficient circumferential length. The film 21 is formed of a heat-resistant resin such as polyimide in a cylindrical shape, which is used as a base layer 21a, and has a release layer 21b such as a fluororesin on the base layer 21a. The total thickness of the film 21 is 100 μm or less, and the heat capacity is smaller than that of the pressure roller 22. Further, grease is applied to the inner peripheral surface (back surface) of the film 21 in contact with the heater 23 and the holder 24 in order to reduce sliding resistance with respect to the heater 23 and the holder 24.

  The pressure roller 22 has a heat-resistant release layer 22b having elasticity such as silicone rubber on the outer peripheral surface of a metal cored bar 22a. The pressure roller 22 is rotatably supported at both ends of the cored bar 22a by first side plate pairs 32a and 32b of the apparatus frame via bearings 31a and 31b. On the upper side of the pressure roller 22, both end portions of the holder 24 holding the heater 23 are held by the second side plate pairs 33a and 33b of the apparatus frame. The first side plate pair 32a, 32b is pressed against the second side plate pair 33a, 33b with a predetermined pressure by a not-shown pressurizing spring (pressurizing means). As a result, the surface of the pressure roller 22 is pressed against the heater 23 with the film 21 in between, and the back surface of the film 21 abuts against the surface of the protective layer 23d of the heater 23, thereby causing a predetermined width between the surface of the film 21 and the surface of the pressure roller 22. A fixing nip portion N is formed. Further, the flanges 25 a and 25 b attached to the second side plate pair 33 a and 33 b in a state of being fitted to the end portion of the holder 24 have restriction surfaces 25 a 1 and 25 b 1 facing the longitudinal end portion of the film 21. And the movement of the film 21 in the longitudinal direction is regulated by the end of the rotating film 21 coming into contact with the regulation surfaces 25a1, 25b1.

  Reference numeral 41 denotes a temperature control unit (temperature control means) that performs control to heat the heater 23 of the fixing device 13. The temperature control unit 41 includes a CPU and a memory such as a RAM and a ROM. The memory stores a temperature control sequence corresponding to the image formation control sequence, a temperature control sequence for a cleaning mode for cleaning the fixing device 13, and the like.

  When the temperature control unit 41 receives the print signal S1, the temperature control unit 41 controls the TRIAC (power supply control means) 42 to maintain the heater temperature (fixing nip portion temperature) at a predetermined fixing temperature (target temperature), and from the AC power source 43 to the heater 23. The pattern 23b is energized through the electrode portion 23c. The heater 23 is quickly heated to generate heat by being energized to the pattern 23b. The heat generation temperature of the heater 23 is detected by a thermistor (temperature detection means) 44 provided on the other surface (heater back surface) of the substrate 23a, and the temperature control unit 41 takes in the detection signal S2. The temperature control unit 41 controls the triac 42 based on the detection signal S <b> 2 and controls the energization amount to the heater 23 supplied from the AC power source 43 to maintain the heater temperature at the fixing temperature.

  When the drive control unit 51 takes in the print signal S1, the drive motor G1 (see FIG. 3) provided at the end of the core bar 22a of the pressure roller 22 rotates the fixing motor (third drive unit) 54. ). As a result, the pressure roller 22 rotates in the counterclockwise direction indicated by the arrow at a predetermined peripheral speed (FIG. 2). The rotational peripheral speed of the pressure roller 22 corresponds to the rotational peripheral speed of the photosensitive drum 1 (Y to M). The rotational force of the pressure roller 22 is transmitted to the surface of the film 21 through the fixing nip N. The film 21 receives a rotational force from the pressure roller 22 and rotates following the clockwise direction of the arrow as the pressure roller 22 rotates. As the fixing device motor 54, for example, a stepping motor or a DC motor can be used. As a result, the pressure roller 22 can be continuously rotated in the direction of the arrow, or can be intermittently performed by a predetermined angle. That is, by repeatedly rotating and stopping the pressure roller 22, a cleaning sheet Pc, which will be described later, can be stepped at the fixing nip portion N.

  In a state where the pressure roller 22 and the film 21 are rotated and the heater temperature is maintained at the fixing temperature, the recording material P carrying the toner image t is introduced into the fixing nip portion N, and the recording material P is transferred to the fixing nip portion N. Nipped and conveyed (FIG. 2). Here, K is the conveyance direction of the recording material P. The toner image t is heated and fixed on the surface of the recording material P by applying heat and pressure to the toner image t in the conveying process.

(3) ETB unit 16
FIG. 5 is an explanatory diagram showing the relationship among the photosensitive drum 1 (Y to K), the ETB unit 16, the fixing device 13, the drive control system, and the temperature control system. FIG. 6 is a structural model view of the ETB unit 16 as viewed from the photosensitive drum 1 (Y to K) side.

  The ETB unit 16 has a frame-like frame 17. On the frame 17, both ends of the shaft 8a1 of the driving roller 8a and the shafts 8b1 and 8c1 of the driven rollers 8b and 8c are rotatably held via bearings (not shown). Further, both ends of the core 5 (Ya to Ka) of the transfer roller 5 (Y to K) and both ends of the core 9a of the suction roller 9 are rotatably held on the frame 17 via bearings (not shown). Has been. The shaft 8a1 of the drive roller 8a is rotatably held by holding side plates 19a and 19b provided outside the frame 17 via a bearing (not shown). Therefore, the ETB unit 16 can swing around the shaft 8a1. An electromagnetic solenoid (transfer member moving means) 55 is coupled to the driven roller 8c provided on the opposite side to the shaft 8a1 serving as the center of oscillation in the frame 17. The solenoid 55 is driven by the drive control unit 51 during the cleaning mode (when the cleaning mode is executed). In this embodiment, the electromagnetic solenoid 55 is used as the transfer member moving means. However, the transfer member moving means is not limited to the electromagnetic solenoid 55, and any mechanism or means may be used as long as it can swing the ETB unit 16. .

(4) Cleaning Mode Performed by Temperature Controller 41 and Drive Controller 51 FIG. 7 is a flowchart of the cleaning mode. FIG. 8 is a view showing the position of the transfer roller 5 (Y to K) in the cleaning mode and the cleaning sheet Pc fed stepwise at the fixing nip N. FIG.

  In FIG. 7, first, at start (S101), the fixing device 13 is in a standby state.

  When the user determines that cleaning is necessary in the standby state of the fixing device 13, the user performs an operation of outputting a cleaning mode command signal S <b> 2 from an operation panel (not shown) provided in the apparatus main body 101. Alternatively, the user performs an operation of outputting a cleaning mode command signal S2 from a host computer (not shown) or the like. The temperature control unit 41 and the drive control unit 51 capture the command signal S2 and switch to the cleaning mode (S102).

  The drive control unit 51 switched to the cleaning mode first starts feeding the cleaning sheet Pc from the feeding cassette 10 (S103). That is, the photosensitive drum motor 52 (Y to K) is rotationally driven to rotate the photosensitive drum 1 (Y to K). At the same time, the ETB motor 53 is driven to rotate and the conveying belt 7 is rotated by the driving roller 8a. Further, the fixing motor 54 is rotated to rotate the pressure roller 22 and the film 21. Then, the sheet Pc is fed from the feeding cassette 10 to the registration roller pair 12 by the pickup roller 11, and the sheet Pc is fed between the conveyance belt 7 and the suction roller 9 by the roller pair 12. The sheet Pc receives charges from the suction roller 9 and is attracted to the surface of the conveyance belt 7, and is sent to the fixing nip portion N of the fixing device 11 by the conveyance belt 7.

  Here, the time for the leading edge of the sheet Pc to reach the fixing nip N can be calculated from the conveyance speed of the sheet Pc and the time when the leading edge of the sheet Pc passes the top sensor Sa. Whether the leading edge of the sheet Pc has exited the fixing nip N can be detected by disposing a sensor downstream of the fixing nip N in the recording material conveyance direction K and detecting the leading edge of the sheet Pc by the sensor. good.

  When it is detected that the leading edge of the sheet Pc has exited the fixing nip N (Yes in S104), the driving of the photosensitive drum motor 52 (Y to K), the ETB motor 53, and the fixing device motor 54 is stopped (S105).

  Next, the solenoid 55 is turned on, the ETB unit 16 is swung in the clockwise direction of the arrow A (FIG. 5) with respect to the photosensitive drum 1 (Y to K), and the ETB unit 16 is separated from the photosensitive drum 1 (Y to K). (S106). As a result, a predetermined gap is generated between the conveyance belt 7 and the photosensitive drum 1 (Y to K), and the transfer nip portion T (Y to K) between the conveyance belt 7 and the photosensitive drum 1 (Y to K) is opened ( FIG. 8). This is because the sheet Pc is not clamped at the transfer nip portion T (Y to K) when the sheet Pc is stepped. This prevents the sheet Pc from being attracted between the fixing nip N and the transfer nip T (Y to K).

  Next, a position where the ETB unit 16 is separated from the photosensitive drum 1 (Y to K) by an output signal from a detection means such as a sensor (not shown) provided in the apparatus main body 101, that is, the transport belt 7 is the photosensitive drum 1 (Y It is confirmed that the position is apart from (˜K) (S107).

  In S108, the temperature control unit 41 energizes the heater 23 (heater ON). Then, the timer time t is set to 0 in S109, the timer is started in S110, and heating by the heater 23 in the fixing nip N is started.

  In this embodiment, the heater 23 is turned on after confirming that the ETB unit 16 is separated from the photosensitive drum 1 (Y to K). However, the heater 23 may be turned on before the ETB unit 16 is separated, and the sliding torque of the film 21 may be reduced by controlling the temperature at a lower temperature than during printing (image formation). This utilizes the fact that the viscosity of the grease applied to the inner surface of the film 21 decreases with increasing temperature. Further, the surface of the pressure roller 22 is warmed to some extent before the sheet Pc enters the fixing nip portion N in order to soften deposits such as offset toner on the surface of the pressure roller 22 so as to be easily attached to the paper as the sheet Pc. It is good to leave. In this case, it is necessary to rotate the pressure roller 22 several times while maintaining the heater 23 at the same high temperature as that during printing. In any case, the timer starts counting simultaneously with the stop of the fixing device motor 54 (that is, the stop of the rotation of the film 21 and the pressure roller 22).

  In S111, it is confirmed whether or not the timer time t has passed a heating time t1 or more until the toner or the like attached to the surface of the pressure roller 22 can be softened and attached to the sheet P1. Alternatively, it may be determined whether the temperature of the heater 23 detected by the thermistor 43 exceeds a predetermined temperature so that the toner or the like attached to the surface of the pressure roller 22 can be softened and attached to the sheet P1. In this case, the predetermined temperature is preferably the softening point or melting point of the toner.

  After softening the deposit on the surface of the pressure roller 22 in this way, the drive controller 51 does not activate the ETB motor 53 and the photosensitive drum motor 52 (Y to K), but activates only the fixing device motor 54 ( S112). In that case, the fixing device motor 54 steps-feeds the sheet Pc by the width of the fixing nip portion N while repeating rotation and stoppage by the pressure roller 22 and the film 21. Thereby, the deposit on the surface of the pressure roller 22 is peeled off from the surface of the pressure roller 22 and transferred to the surface of the sheet Pc.

  In this way, by softening the toner on the surface of the pressure roller 22 while the sheet Pc is stopped (S107 to S111), the softened toner can enter the unevenness of the surface of the sheet Pc and adhere to the surface of the sheet Pc.

  The entire surface of the pressure roller 22 can be cleaned by repeating the above-described softening of the toner and feeding the width of the fixing nip portion N of the sheet Pc for one rotation of the pressure roller 22.

  In the present embodiment, the fixing motor 54 is stopped (S113) after the sheet Pc is fed for the driving time of 15 ms for the fixing motor 54 in S112. As a result, the sheet Pc is conveyed (step-feed) by the pressure roller 22 and the film 21 while being repeatedly rotated and stopped. Then, S108 to S114 are repeated until the trailing edge of the sheet Pc enters the fixing nip portion N (No in S113). Further, the ETB motor 53 and the photosensitive drum motor 52 (Y to K) are stopped from S108 to S114.

  When the trailing edge of the sheet P1 enters the fixing nip portion N in S114 (Yes), the drive control unit 51 drives the fixing device motor 54 to rotate at a regular constant speed (S115). When it is determined that the discharge of the sheet Pc from the fixing nip N has been completed (S116), the solenoid 55 is turned off, and the ETB unit 16 is brought into contact with the surface of the conveyor belt 7 with the surface of the photosensitive drum 1 (Y to K). (S117).

  In S118, the ETB unit 16 comes close to the photosensitive drum 1 (Y to K) by an output signal from a detection means such as a sensor (not shown), that is, the position where the transport belt 7 contacts the photosensitive drum 1 (Y to K). Make sure that there is. After the confirmation, the temperature control unit 41 and the drive control unit 51 end the cleaning mode (S119).

  The timing to end the cleaning mode is after the entire surface of the pressure roller 22 has stopped in the fixing nip N at least once even if the trailing edge of the sheet Pc does not enter the fixing nip N. But you can.

  Next, the following experiment was performed for the step feed cleaning in the image forming apparatus of the present embodiment and the step feed cleaning proposed in Japanese Patent Laid-Open No. 2000-47509. The results are shown in Table 1.

  In Table 1, (1) shows an evaluation of a halftone image after step feed cleaning was repeated 10 times for each of the image forming apparatus of the present embodiment (Example 1) and the image forming apparatus of Patent Document 3 (Comparative Example). It is. (2) is a cleaning that causes gear out-of-step / damage of the rotational drive system when step feed cleaning is performed for each of the image forming apparatus of the present embodiment (Example 1) and the image forming apparatus of Patent Document 3 (comparative example). Is the number of times.

  As shown in Table 1, in (1), the image after 10 repetitions had no image defect after the cleaning of this example shown in Example 1. On the other hand, in the comparative example, vertical streak marks were seen on the image. Further, when the inside of the image forming apparatus was examined, vertical scratches in the recording material conveyance direction were observed on the photosensitive drum surface and the conveyance belt surface. In (2), in the cleaning mode of this example shown in Example 1, no abnormality was found in the drive gear of the photosensitive drum 1 (Y to K) even after repeating 100 times. On the other hand, in the comparative example, the drive gear of the photosensitive drum was stepped out at the 20th cleaning.

  According to this embodiment, the conveyance belt 7 is separated from the photosensitive drum 1 (Y to K), and the sheet Pc is conveyed by the pressure roller 22 and the film 21 while being repeatedly rotated and stopped, and the surface of the pressure roller 22 is conveyed. Cleaning is performed with the sheet Pc. That is, during such step feed cleaning, the transfer nip T (Y to K) is opened and the sheet Pc is not nipped at the transfer nip T (Y to K). Therefore, it is possible to prevent the sheet Pc from being attracted between the transfer nip T (Y to K) and the fixing nip N. Further, it is possible to prevent the surface of the photosensitive drum 1 (Y to K) or the surface of the conveyor belt 7 from being damaged by the sheet Pc. As a result, it is possible to prevent the occurrence of image defects due to the surface damage of the photosensitive drum 1 (Y to K) or the surface damage of the conveying belt 7. Further, the photosensitive drum motor 52 (Y to K), the ETB motor 53, the fixing device motor 54, and the rotational drive system such as a gear that transmits the driving force from the motor to the driving target member in each motor may be out of step or damaged. Can be prevented.

  Another image forming apparatus according to the present invention will be described.

  In the present embodiment, members and portions that are the same as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. The same applies to Example 3.

  FIG. 9 is an overall model diagram of the image forming apparatus of this embodiment. FIG. 10 is an explanatory diagram showing the relationship among the photosensitive drum 1 (Y to K), the ETB unit 16, the fixing device 13, the drive control system, and the temperature control system. FIG. 11 is a view showing a holding structure of the conveying belt 7 and the transfer roller 5 (Y to K) as viewed from the photosensitive drum 1 (Y to K) side.

  The image forming apparatus shown in the present embodiment is configured so that the stretched state of the conveying belt 7 is convex toward the photosensitive drum 1 (Y to K) (FIG. 9). Both ends of the shafts 8a1, 8b1, and 8c1 of the driving roller 8a and the driven rollers 8b and 8c that stretch the conveyance belt 7 are rotatably held by the holding side plates 19a and 19b via bearings (not shown). (FIG. 10, FIG. 11). Further, both end portions of the core 9a of the suction roller 9 are rotatably held by the holding side plates 19a and 19b via a bearing (not shown). Long holes 19cY, 19cM, 19cC, and 19cK extending in the radial direction of the photosensitive drum 1 (Y to K) are formed in the holding side plates 19a and 19b at positions corresponding to the photosensitive drum 1 (Y to K). Both ends of the metal core 5 (Ya to Ka) of the transfer roller 5 (Y to K) are rotatably held in the long hole 19c (Y to K) via a bearing (not shown). Electromagnetic solenoids (transfer member moving means) 56Y, 56M, 56C, and 56K are coupled to the core 5 (Ya to Ka) of the transfer roller 5 (Y to K), respectively. The solenoid 56 (Y to K) is driven by the drive control unit 51 in the cleaning mode.

  A flowchart of the cleaning mode in the image forming apparatus according to the present exemplary embodiment will be described.

  FIG. 12 is a flowchart of the cleaning mode. FIG. 13 is a view showing the position of the transfer roller 5 (Y to K) in the cleaning mode and the cleaning sheet Pc fed stepwise at the fixing nip portion N.

  In FIG. 12, S201 to S205 are the same as S101 to S105 in the flowchart (FIG. 7) of the first embodiment.

  In S206, the solenoid 56 (Y to K) is turned on and the transfer roller 5 (Y to K) is moved in the opposite direction (arrow B direction) to the photosensitive drum 1 (Y to K) with respect to the photosensitive drum 1 (Y to K). Move (S206). As the transfer roller 5 (Y to K) moves, the conveying belt 7 also moves in the direction of arrow B between the driving roller 8a and the driven roller 8b. As a result, a predetermined gap is generated between the conveyance belt 7 and the photosensitive drum 1 (Y to K), and the transfer nip portion T (Y to K) between the conveyance belt 7 and the photosensitive drum 1 (Y to K) is opened ( FIG. 13).

  Next, based on an output signal from a detection means such as a sensor (not shown) provided in the apparatus main body 101, it is confirmed that the transfer roller 5 (Y to K) is in a position separated from the photosensitive drum 1 (Y to K). . That is, it is confirmed that the conveying belt 7 is at a position separated from the photosensitive drum 1 (Y to K) (S207).

  S208 to S216 are the same as S108 to S116 in the flowchart of the first embodiment.

  In S217, the solenoid 56 (Y to K) is turned off, and the transfer roller 5 (Y to K) is returned to the original position where the surface of the conveying belt 7 is in contact with the surface of the photosensitive drum 1 (Y to K).

  In S218, a position where the transfer roller 5 (Y to K) comes close to the photosensitive drum 1 (Y to K) by an output signal from a detection unit such as a sensor (not shown), that is, the transport belt 7 is the photosensitive drum 1 (Y to K). Make sure that you are in contact with the position. After the confirmation, the temperature control unit 41 and the drive control unit 51 end the cleaning mode (S219).

  Also in this embodiment, the conveyance belt 7 is separated from the photosensitive drum 1 (Y to K), and the sheet Pc is conveyed while being repeatedly rotated and stopped by the pressure roller 22 and the film 21, and the surface of the pressure roller 22 is conveyed to the sheet. It can be cleaned with Pc. Therefore, it is possible to obtain the same effect as that of the first embodiment.

  Another image forming apparatus according to the present invention will be described.

  In the image forming apparatus shown in this embodiment, the ETB motor 53 and the fixing device motor 54 are driven during the step feed cleaning described in the first embodiment, and the sheet is formed by the conveyance belt 7, the pressure roller 22 and the film 21. Pc is step-fed. Except for this configuration, the image forming apparatus is configured in the same manner as the image forming apparatus of the first embodiment.

The gist of the image forming apparatus shown in the present embodiment is that the cleaning sheet Pc is conveyed in the same manner as in a normal image forming operation until the leading edge thereof passes through the fixing nip portion N. Therefore, depending on the configuration of the conveyance mechanism, the electric resistance of the conveyance belt 7 and the sheet, the electric resistance of the sheet Pc, and the transfer / adsorption bias, the sheet can be used even when the conveyance belt 7 is separated from the photosensitive drum 1 (Y to K). Pc may remain adsorbed on the conveyor belt 7. In this state, when the sheet feeding Pc is stepped by the pressure roller 22 and the film 21 by driving the fixing device motor 54, the surface of the conveying belt 7 is damaged by the sheet Pc.

  Therefore, in this embodiment, the ETB motor 53 is driven and the sheet Pc is stepped by the conveying belt 7 when the sheet Pc is stepped by driving the fixing device motor 54. Further, due to the difference in the starting characteristics between the fixing device motor 54 and the ETB motor 53, the feeding amount of the sheet Pc on the conveying belt 7 side is larger than that on the fixing device 13 side in order to prevent damage to the surface of the conveying belt 7 due to the tension on the fixing device 13 side. It is set to be. In this embodiment, the driving time of the ETB motor is 20 ms, and the driving time of the fixing device motor 54 is 15 ms.

  FIG. 14 is a flowchart of the cleaning mode of the image forming apparatus according to the present exemplary embodiment. FIG. 15 shows the position of the transfer roller 5 (Y to K) in the cleaning mode, and also shows the cleaning sheet Pc fed stepwise by the fixing nip portion N and the conveying belt 7.

  In FIG. 14, S301 to S311 are the same as S101 to S111 in the flowchart (FIG. 7) of the first embodiment.

  In step S312, the ETB motor 53 and the fixing device motor 54 are started without starting the photosensitive drum motor 52 (Y to K). That is, when the sheet Pc is stepped by the pressure roller 22 and the film 21 by driving the fixing device motor 54, the ETB motor 53 is driven and the sheet Pc is stepped by the transport belt 7. At this time, the driving time of the ETB motor 53 is 20 ms, and the driving time of the fixing device motor 54 is 15 ms. Therefore, the drive time of the ETB motor 53 is longer than the drive time of the fixing device motor 54. That is, the feed amount of the sheet Pc by the transport belt 7 is larger than the feed amount of the sheet Pc by the pressure roller 22 and the film 21.

  S313 to S319 are the same as S113 to S119 in the flowchart of the first embodiment.

  In the image forming apparatus that executes the cleaning mode of the present embodiment and the image forming apparatus that executes the cleaning mode shown in Embodiment 1, the surface of the transport belt 7 when the cleaning mode is repeated 10 times / 50 times / 100 times The wound was investigated. The results are shown in Table 2.

  As shown in Table 2, in the image forming apparatus of this example, no scratch was found on the surface of the conveyor belt 7 even when the cleaning mode was repeated 100 times. On the other hand, in the image forming apparatus of Example 1, scratches occurred from about 50 times, and many scratches were observed after 100 times.

  As described above, at the time of step feeding of the sheet Pc by driving the fixing device motor 54, the ETB motor 53 is driven to step feed the sheet Pc, and the feeding amount of the sheet Pc on the conveying belt 7 side is set to the fixing device 13 side. It is bigger. This can prevent the surface of the conveyor belt 7 from being damaged.

  Even if the cleaning mode of the image forming apparatus according to the present embodiment is applied to the image forming apparatus instead of the cleaning mode of the image forming apparatus according to the second embodiment, the same effect can be obtained.

1 is an overall configuration diagram of an image forming apparatus according to a first embodiment. Longitudinal cross section model of fixing device Front view of the fixing device Explanatory drawing of heater Explanatory drawing showing the relationship between the photosensitive drum, ETB unit, fixing device, drive control system and temperature control system Configuration model view of the ETB unit from the photosensitive drum side Cleaning mode flowchart A view showing the position of the transfer roller in the cleaning mode and a cleaning sheet stepped at the fixing nip portion. Overall model diagram of image forming apparatus according to Embodiment 2 Explanatory drawing showing the relationship between the photosensitive drum, ETB unit, fixing device, drive control system and temperature control system Diagram showing holding structure of transfer belt and transfer roller as seen from photosensitive drum side Cleaning mode flowchart A view showing the position of the transfer roller in the cleaning mode and a cleaning sheet stepped at the fixing nip portion. Flowchart of Cleaning Mode of Image Forming Apparatus According to Embodiment 3 A diagram showing the position of the transfer roller in the cleaning mode, and a cleaning sheet stepped by the fixing nip portion and the conveyance belt

Explanation of symbols

1Y, 1M, 1C, 1K: photosensitive drum, 5Y, 5M, 5C, 5K: transfer roller, 7: transport belt, 21: film, 22: pressure roller, 41: temperature controller, 51: drive controller, 52Y , 52M, 52C, 52K: photosensitive drum motor, 53: transport belt motor (ETB motor), 54: fixing device motor, 55, 56: electromagnetic solenoid

Claims (3)

A rotatable image carrier for carrying a developed image; a first drive means for rotationally driving the image carrier; a rotatable recording material conveying member opposed to the image carrier for conveying a recording material; A second driving unit that rotationally drives the recording material conveying member; a transfer member that forms a transfer nip portion by sandwiching the recording material conveying member with the image carrier; and two members that contact each other to form a fixing nip portion A recording medium transported by the recording material transporting member, comprising: a rotating body; a third driving unit that rotationally drives any of the rotating bodies; and a heating body that heats any of the rotating bodies. In the image forming apparatus in which the developed image is transferred by the transfer member at the transfer nip portion, the recording material to which the developed image is transferred is sandwiched and conveyed by the fixing nip portion, and the developed image is fixed to the recording material by the heat of the heating body.
Transfer member moving means for moving the transfer member so as to separate or contact the recording material conveying member with the image carrier;
A drive control means for controlling the driving of the first, second and third driving means and for controlling the driving of the transfer member driving means;
Temperature control means for controlling the heating body; and
Have
In the cleaning mode in which the rotating body is cleaned, the temperature control means performs control to start heating the heating body, and the drive control means causes the recording material conveying member to feed a cleaning sheet to the fixing nip. The transfer member controls the drive of the first drive means and the second drive means so as to be conveyed to a portion, and moves the transfer member to separate the recording material conveyance member from the image carrier. The driving of the third driving unit is controlled so as to control the driving of the driving unit and to convey the sheet held by the fixing nip portion while being repeatedly rotated and stopped by the rotating body. Image forming apparatus.   The drive control means conveys the sheet to the fixing nip portion by the recording material conveying member rather than a sheet feed amount for nipping and conveying the sheet by the fixing nip portion while repeating rotation and stop by the two rotating bodies. The image forming apparatus according to claim 1, wherein the driving of the third driving unit is controlled so that a sheet feeding amount is increased. The image forming apparatus according to claim 1, wherein a plurality of the image carrier and the transfer member are provided in parallel along a recording material conveyance direction of the recording material conveyance member.