JP2015206898A - Fixing apparatus and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing apparatus configured to prevent a motor for applying a driving force from being damaged during repair control which eliminates gloss streak, and an image forming apparatus.SOLUTION: A fixing apparatus includes a control section. The control section 100, during non-fixation mode, controls a fixing nip width changing section 68 to change a fixing nip width d to be smaller than a fixing nip width d for fixation, and starts a drive motor M3 while causing a brake torque generation section 66 to generate braking force D in an upper pressure roller 63, to execute repair control for rotating a fixing belt 61 and a lower pressure roller 65. The control section 100, during repair control, executes limitation control for reducing the braking force D generated by the braking torque generation section 66 when a rotation torque of the driving motor M3 detected by the torque detection section 104 is equal to or larger than a predetermined torque.

Description

  The present invention relates to a fixing device and an image forming apparatus.

  In general, an electrophotographic image forming apparatus (printer, copier, facsimile, etc.) includes a fixing device that fixes toner by applying heat and pressure to a sheet onto which a toner image is transferred. The fixing device includes a heating unit that heats and melts toner carried on a sheet, and a pressure unit that presses the sheet against the heating unit.

  Such fixing devices include the following. First, in the fixing device described in Patent Document 1, a nip portion is formed by a fixing roller and a part of an endless belt stretched by a plurality of rollers, and an outlet portion of the nip portion is formed from the inner peripheral side of the endless belt. A pressure roller is provided in pressure contact with the fixing roller via an endless belt. According to this fixing device, a braking force is applied to the conveyance of the endless belt in the area of the pressure roller to eliminate a speed difference from the fixing roller and to prevent image displacement (see Patent Document 1).

  The fixing device described in Patent Document 2 includes a pressure roller and a plurality of rollers around which the fixing belt is wound, and rotates one of the plurality of rollers in a direction that hinders the rotation driving. The brake is applied to the fixing belt by being rotated. According to this fixing device, the fixing belt is pulled between one roller and the other roller, and a nip portion is formed by the pulled portion and the pressure roller, thereby fixing the fixing belt to the pressure roller. Can be closely attached to the outer peripheral surface of the substrate (see Patent Document 2).

JP-A-6-250560 Japanese Patent Laid-Open No. 9-138598

  However, in the fixing devices described in Patent Documents 1 and 2, when a thick paper or a paper with a rough surface is continuously passed, the surface of the fixing belt becomes rough at both side edges of the thick paper or a paper with a rough surface, and thereafter When large-size paper is passed, a glossy streak appears in which the gloss of the image fixed at that portion appears lower than that of other portions.

  In order to solve this problem, for example, a driving force is applied to one of a fixing surface side member and a back surface side member constituted by a roller or a fixing belt, a braking force is applied to the other, and at the time of non-fixing than at the time of fixing. Control to repair the roller surface is effective by making the nip width small and idling for a certain period of time.

  However, when the nip width increases due to a change in temperature environment and the braking force increases, the motor that applies the driving force may be overloaded and the motor may be damaged.

  The present invention has been made in order to solve the conventional problems, and an object of the present invention is to prevent the motor that applies the driving force from being damaged during the repair control for eliminating the glossy streak. It is an object of the present invention to provide a fixing device and an image forming apparatus that can perform the above operation.

  In order to achieve the above object, a fixing device according to the present invention includes a fixing surface side member disposed on a fixing surface side of a sheet on which a toner image is formed, and the sheet in a state of being pressed against the fixing surface side member. A back-side member that forms a fixing nip portion that is nipped and conveyed, a drive motor that rotationally drives the back-side member, torque detection means that detects rotational torque of the drive motor, and fixing of the fixing nip portion By controlling the fixing nip width changing portion, the fixing nip width changing portion for changing the nip width, the braking force generating means for generating the braking force in the direction that prevents the rotation of the fixing surface side member, and the fixing nip width changing portion when not fixing. The drive motor is operated in a state where the fixing nip width is smaller than the fixing nip width at the time of fixing and the braking force is generated on the fixing surface side member by the braking force generating means. When the restoration control for rotating the fixing surface side member and the back surface side member is executed, and the rotational torque of the drive motor detected by the torque detection means during the restoration control becomes a predetermined torque or more. Control means for executing restriction control for reducing the braking force generated by the braking force generation means.

  According to this fixing device, the fixing surface side member and the fixing surface side member are operated by operating the driving motor in a state where the fixing nip width is smaller than that at the time of fixing during non-fixing and a braking force is generated on the fixing surface side member. The repair control for rotating the back side member is executed, and the limit control for reducing the braking force is executed when the rotational torque of the drive motor is equal to or greater than a predetermined torque. For this reason, even if the braking force increases due to, for example, a change in temperature environment, the braking force generated by the braking force generation means is reduced when the rotational torque of the drive motor becomes equal to or greater than a predetermined torque. Therefore, by setting the predetermined torque to a value that does not damage the driving motor, it is possible to prevent the motor that applies the driving force from being damaged during the repair control for eliminating the glossy streak.

  Further, in the fixing device according to the present invention, it is preferable that the braking force generating means includes a plurality of braking force generating motors that generate a braking force in a direction that prevents rotation of the fixing surface side member.

  According to this fixing device, since the plurality of braking force generation motors that generate the braking force in a direction that hinders rotation of the fixing surface side member are provided, the size is large and the cost is high as in the case where the braking force is generated by one motor. This eliminates the need to use a motor and can reduce the cost while saving space. In addition, by providing a plurality of motors, each of the plurality of motors can be controlled, and the braking force can be adjusted more finely.

  Further, in the fixing device according to the present invention, the control means includes the plurality of braking force generation motors when a rotational torque of the drive motor detected by the torque detection means during the repair control is equal to or greater than a predetermined torque. It is preferable to execute the restriction control by turning off at least one of the above.

  According to this fixing device, when the rotational torque of the drive motor is equal to or greater than a predetermined torque, the restriction control is executed by turning off at least one of the plurality of braking force generation motors. Control can be facilitated without adjusting the torque of the motor and reducing the braking force.

  Further, in the fixing device according to the present invention, the braking force generation means includes a single braking force generation motor that generates a braking force in a direction that prevents rotation of the fixing surface side member, and the single braking force generation motor. Adjusting means that adjusts the braking force of the driving motor, and the control means adjusts the rotational speed of the drive motor detected by the torque detecting means during the repair control to be equal to or greater than a predetermined torque. It is preferable that the limit control is executed by reducing the braking force of the single braking force generation motor by controlling.

  According to this fixing device, when the rotational torque of the drive motor is equal to or greater than the predetermined torque, the limit control is executed by controlling the adjusting unit to reduce the braking force of the single braking force generation motor. Without using a plurality of braking force generating motors, it is possible to prevent the motor that applies the driving force from being damaged.

  Further, in the fixing device according to the present invention, the control means, after executing the restriction control, has a rotation torque of the drive motor detected by the torque detection means equal to or less than a second predetermined torque smaller than the predetermined torque. In this case, it is preferable to execute an increase control for increasing the braking force generated by the braking force generation means more than the braking force after the limit control.

  According to this fixing device, when the rotational torque of the drive motor becomes equal to or less than the second predetermined torque that is smaller than the predetermined torque after the limit control is executed, the braking force generated by the braking force generating means is increased more than the braking force after the limit control. Increase control is executed. For this reason, it is possible to prevent the braking force from being reduced to such an extent that the glossy streak cannot be eliminated by the restriction control, and appropriate repair can be performed while preventing damage to the motor that applies the driving force.

  Further, in the fixing device according to the present invention, the control unit detects the torque detected by the torque detecting unit when the limit control is executed to set the braking force generated by the braking force generating unit to a minimum value. When the rotational torque of the drive motor is equal to or greater than a predetermined torque, it is preferable to output an error signal indicating an abnormal state.

  According to this fixing device, when the braking force is set to the minimum value, an error signal indicating an abnormal state is output when the rotational torque of the drive motor exceeds a predetermined torque. For this reason, for example, an abnormal state in which the rotational torque of the drive motor reaches a predetermined torque or more due to the engagement of various rollers in the fixing device can be notified.

  An image forming apparatus according to the present invention includes an image forming unit that forms a toner image on a sheet, and the toner image formed by the image forming unit is fixed on the sheet. And a fixing device.

  According to this image forming apparatus, since the image forming unit that forms a toner image on a sheet and the fixing device that fixes the toner image formed by the image forming unit on the sheet are provided, gloss lines are eliminated. It is possible to prevent the motor that applies the driving force from being damaged during the repair control, and to output a printed matter with improved image gloss.

  According to the present invention, it is possible to provide a fixing device and an image forming apparatus that can prevent a motor that applies a driving force from being damaged during repair control for eliminating glossy stripes.

1 is a diagram schematically showing an overall configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a diagram illustrating a main part of a control system of the image forming apparatus according to the present embodiment. FIG. 2 is a diagram schematically illustrating a configuration of a fixing unit. FIG. 4 is a diagram illustrating in detail a part of the configuration of the fixing unit illustrated in FIG. 3. 6 is a flowchart illustrating an operation of the fixing device according to the first embodiment. 6 is a timing chart for explaining the operation of the fixing device according to the first embodiment, showing the operating state of the braking force generating motor during the repair control. FIG. 10 is a diagram schematically illustrating a configuration of a fixing unit according to a second embodiment. FIG. 8 is a diagram illustrating in detail a part of the configuration of the fixing unit illustrated in FIG. 7. 6 is a first flowchart illustrating an operation of a fixing device according to a second embodiment. 10 is a second flowchart showing the operation of the fixing device according to the second embodiment. FIG. 9 is a timing chart for explaining the operation of the fixing device according to the second embodiment, showing the operating state of the braking force generation motor during the repair control.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments.

  FIG. 1 is a diagram schematically showing an overall configuration of an image forming apparatus 1 according to the first embodiment of the present invention. FIG. 2 is a diagram illustrating a main part of a control system of the image forming apparatus 1 according to the first embodiment. An image forming apparatus 1 shown in FIGS. 1 and 2 is a color image forming apparatus of an intermediate transfer system using an electrophotographic process technology. That is, the image forming apparatus 1 transfers the toner images of Y (yellow), M (magenta), C (cyan), and K (black) formed on the photosensitive drum 413 to the intermediate transfer belt 421 (primary transfer). Then, after superposing four color toner images on the intermediate transfer belt 421, the toner images are transferred to the paper S (secondary transfer) to form an image.

  Further, in the image forming apparatus 1, the photosensitive drums 413 corresponding to the four colors of YMCK are arranged in series in the running direction of the intermediate transfer belt 421, and the respective color toner images are sequentially transferred to the intermediate transfer belt 421 in one step. Tandem system is adopted.

  As shown in FIGS. 1 and 2, the image forming apparatus 1 includes an image reading unit 10, an operation display unit 20, an image processing unit 30, an image forming unit 40, a paper transport unit 50, a fixing unit 60, and a control unit 100. Prepare.

  The control unit 100 includes a CPU (Central ProGessing Unit) 101, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, and the like. The CPU 101 reads a program corresponding to the processing content from the ROM 102 and develops it in the RAM 103, and centrally controls the operation of each block of the image forming apparatus 1 in cooperation with the developed program. At this time, various data stored in the storage unit 72 is referred to. The storage unit 72 includes, for example, a nonvolatile semiconductor memory (so-called flash memory) or a hard disk drive.

  The control unit 100 transmits and receives various data to and from an external device (for example, a personal computer) connected to a communication network such as a LAN (Local Area Network) or a WAN (Wide Area Network) via the communication unit 71. Do. For example, the control unit 100 receives image data transmitted from an external device, and forms an image on the paper S based on the image data (input image data). The communication unit 71 is composed of a communication control card such as a LAN card, for example.

  The image reading unit 10 includes an automatic document feeder 11 called an ADF (Auto Document Feeder), a document image scanning device 12 (scanner), and the like.

  The automatic document feeder 11 transports the document D placed on the document tray by a transport mechanism and sends it out to the document image scanning device 12. The automatic document feeder 11 can continuously read images (including both sides) of a large number of documents D placed on a document tray all at once.

  The document image scanning device 12 optically scans a document conveyed on the contact glass from the automatic document feeder 11 or a document placed on the contact glass, and reflects light from the document to a CCD (Charge Coupled Device). ) An image is formed on the light receiving surface of the sensor 12a, and an original image is read. The image reading unit 10 generates input image data based on the reading result by the document image scanning device 12. The input image data is subjected to predetermined image processing in the image processing unit 30.

  The operation display unit 20 is configured by, for example, a liquid crystal display (LCD) with a touch panel, and functions as a display unit 21 and an operation unit 22. The display unit 21 displays various operation screens, an image status display, an operation status of each function, and the like in accordance with a display control signal input from the control unit 100. The operation unit 22 includes various operation keys such as a numeric keypad and a start key, receives various input operations by the user, and outputs an operation signal to the control unit 100.

  The image processing unit 30 includes a circuit that performs digital image processing on input image data according to initial settings or user settings. For example, the image processing unit 30 performs gradation correction based on the gradation correction data (gradation correction table) under the control of the control unit 100. Further, the image processing unit 30 performs various correction processes such as color correction and shading correction, a compression process, and the like on the input image data in addition to the gradation correction. The image forming unit 40 is controlled based on the image data subjected to these processes.

  The image forming unit 40 is based on the input image data, and image forming units 41Y, 41M, 41C, 41K, and an intermediate transfer unit 42 for forming an image using colored toners of Y component, M component, C component, and K component. Etc.

  The Y component, M component, C component, and K component image forming units 41Y, 41M, 41C, and 41K have the same configuration. For convenience of illustration and explanation, common constituent elements are denoted by the same reference numerals, and Y, M, C, or K are added to the reference numerals when distinguished from each other. In FIG. 1, only the components of the Y-component image forming unit 41Y are denoted by reference numerals, and the constituent elements of the other image forming units 41M, 41C, and 41K are omitted.

  The image forming unit 41 includes an exposure device 411, a developing device 412, a photosensitive drum 413, a charging device 414, a drum cleaning device 415, and the like.

  The photosensitive drum 413 has an undercoat layer (UCL) and a charge generation layer (CGL) on the peripheral surface of an aluminum conductive cylinder (aluminum tube) having a drum diameter of 80 mm, for example. It is a negatively charged organic photoconductor (OPC) in which a generation layer (CTL) and a charge transport layer (CTL) are sequentially stacked. The charge generation layer is made of an organic semiconductor in which a charge generation material (for example, phthalocyanine pigment) is dispersed in a resin binder (for example, polycarbonate), and generates a pair of positive charges and negative charges by exposure with the exposure device 411. The charge transport layer consists of a material in which a hole transport material (electron donating nitrogen-containing compound) is dispersed in a resin binder (for example, polycarbonate resin), and transports positive charges generated in the charge generation layer to the surface of the charge transport layer. To do.

  The control unit 100 controls the drive current supplied to a motor (not shown) that rotates the photosensitive drum 413, so that the photosensitive drum 413 rotates at a constant peripheral speed.

  The charging device 414 uniformly charges the surface of the photoconductive drum 413 to a negative polarity. The exposure device 411 is composed of, for example, a semiconductor laser, and irradiates the photosensitive drum 413 with laser light corresponding to the image of each color component. A positive charge is generated in the charge generation layer of the photosensitive drum 413 and is transported to the surface of the charge transport layer, whereby the surface charge (negative charge) of the photosensitive drum 413 is neutralized. An electrostatic latent image of each color component is formed on the surface of the photosensitive drum 413 due to a potential difference from the surroundings.

  The developing device 412 is, for example, a two-component developing type developing device, and forms a toner image by visualizing the electrostatic latent image by attaching toner of each color component to the surface of the photosensitive drum 413.

  The drum cleaning device 415 includes a drum cleaning blade that is slidably contacted with the surface of the photosensitive drum 413, and removes transfer residual toner remaining on the surface of the photosensitive drum 413 after primary transfer.

  The intermediate transfer unit 42 includes an intermediate transfer belt 421, a primary transfer roller 422, a plurality of support rollers 423, a secondary transfer roller 424, a belt cleaning device 426, and the like.

  The intermediate transfer belt 421 is an endless belt, and is stretched around a plurality of support rollers 423 in a loop shape. At least one of the plurality of support rollers 423 is configured by a driving roller, and the other is configured by a driven roller. For example, it is preferable that the roller 423A disposed downstream of the K component primary transfer roller 422 in the belt traveling direction is a drive roller. This makes it easy to keep the belt running speed constant in the primary transfer portion. As the driving roller 423A rotates, the intermediate transfer belt 421 travels in the direction of arrow A at a constant speed.

  The primary transfer roller 422 is disposed on the inner peripheral surface side of the intermediate transfer belt 421 so as to face the photosensitive drum 413 of each color component. The primary transfer roller 422 is pressed against the photosensitive drum 413 with the intermediate transfer belt 421 interposed therebetween, whereby a primary transfer nip for transferring the toner image from the photosensitive drum 413 to the intermediate transfer belt 421 is formed.

  The secondary transfer roller 424 is disposed on the outer peripheral surface side of the intermediate transfer belt 421 so as to face a roller 423B (hereinafter referred to as “backup roller 423Bl”) disposed on the downstream side in the belt traveling direction of the drive roller 423A. The secondary transfer roller 424 is pressed against the backup roller 423B with the transfer belt 421 interposed therebetween, whereby a secondary transfer nip for transferring the toner image from the intermediate transfer belt 421 to the paper S is formed.

  When the intermediate transfer belt 421 passes through the primary transfer nip, the toner images on the photoconductive drum 413 are primarily transferred onto the intermediate transfer belt 421 in sequence. Specifically, a primary transfer bias is applied to the primary transfer roller 422, and an electric charge having a polarity opposite to that of the toner is applied to the back side of the intermediate transfer belt 421 (the side in contact with the primary transfer roller 422). It is electrostatically transferred to the intermediate transfer belt 421.

  Thereafter, when the sheet S passes through the secondary transfer nip, the toner image on the intermediate transfer belt 421 is secondarily transferred to the sheet S. Specifically, a toner image is applied by applying a secondary transfer bias to the secondary transfer roller 424 and applying a charge having a polarity opposite to that of the toner to the back side of the paper S (the side in contact with the secondary transfer roller 424). Is electrostatically transferred to the paper S. The sheet S to which the toner image is transferred is conveyed toward the fixing unit 60.

  The belt cleaning device 426 includes a belt cleaning blade that is in sliding contact with the surface of the intermediate transfer belt 421 and removes transfer residual toner remaining on the surface of the intermediate transfer belt 421 after the secondary transfer. Instead of the secondary transfer roller 424, a configuration (so-called belt-type secondary transfer unit) in which a secondary transfer belt is looped around a plurality of support rollers including the secondary transfer roller is adopted. Also good.

  The fixing unit 60 includes an upper fixing unit 60A having a fixing surface side member disposed on the fixing surface (surface on which the toner image is formed) of the paper S, and the back surface (surface opposite to the fixing surface) of the paper S. A lower fixing unit 60B having a rear surface side member to be arranged and a heating source 60C are provided. When the back surface side support member is pressed against the fixing surface side member, a fixing nip portion that holds and conveys the sheet S is formed.

  The fixing unit 60 fixes the toner image on the paper S by heating and pressurizing the paper S, to which the toner image has been secondarily transferred and conveyed, at the fixing nip part. The fixing unit 60 is disposed in the fixing device F as a unit. The fixing device F may be provided with an air separation unit that separates the sheet S from the fixing surface side member or the back surface side support member by blowing air. Details of the fixing unit 60 will be described later.

  The paper transport unit 50 includes a paper feed unit 51, a paper discharge unit 52, a transport path unit 53, and the like. In the three paper feed tray units 51a to 51c constituting the paper feed unit 51, paper S (standard paper, special paper) identified based on basis weight, size, or the like is stored for each preset type. . The conveyance path unit 53 includes a plurality of conveyance roller pairs such as registration roller pairs 53a.

  The sheets S stored in the sheet feed tray units 51 a to 51 c are sent one by one from the top and are conveyed to the image forming unit 40 by the conveyance path unit 53. At this time, the registration roller portion provided with the registration roller pair 53a corrects the inclination of the fed paper S and adjusts the conveyance timing. In the image forming unit 40, the toner image on the intermediate transfer belt 421 is secondarily transferred onto one side of the sheet S at a time, and a fixing process is performed in the fixing unit 60. The sheet S on which the image has been formed is discharged out of the apparatus by a discharge unit 52 having a discharge roller 52a.

  Next, the configuration of the fixing unit 60 will be described with reference to FIG. FIG. 3 is a diagram schematically illustrating the configuration of the fixing unit 60.

  The fixing unit 60 and the control unit 100 function as a fixing device. The fixing unit 60 and the control unit 100 may be configured as a unit and attached to the image forming apparatus 1, or may be separately incorporated in the image forming apparatus 1 and function as a fixing device. .

  The upper fixing unit 60A includes an endless fixing belt (fixing surface side member) 61, a heating roller 62, an upper pressure roller (fixing surface side member) 63, and a stretching member 64 (belt heating method). The fixing belt 61 is stretched between the heating roller 62, the upper pressure roller 63, and the stretching member 64 with a predetermined belt tension (for example, 400 [N]).

  The fixing belt 61 has, for example, an outer diameter of 120 [mm], a heat-resistant silicone rubber having a thickness of 200 [μm] using an outer peripheral surface of a base made of PI (polyimide) having a thickness of 70 [μm] as an elastic layer. The surface layer is coated or coated with a tube of PFA (perfluoroalkoxy), which is a heat-resistant resin having a thickness of 30 [μm], on the surface layer. The fixing belt 61 forms a fixing nip portion NP together with the lower pressure roller 65.

  The fixing belt 61 contacts the paper S on which the toner image is formed, and heat-fixes the toner image on the paper S at a fixing temperature (for example, 160 to 200 [° C.]). Here, the fixing temperature is a temperature at which the amount of heat necessary to melt the toner on the paper S can be supplied, and varies depending on the paper type of the paper S on which an image is formed.

  The heating roller 62 heats the fixing belt 61. The heating roller 62 includes a heating source 60 </ b> C (halogen heater) that heats the fixing belt 61. The outer diameter of the heating roller 62 is 58 [mm], and for example, the outer peripheral surface of a cylindrical metal core made of aluminum or the like is covered with a resin layer coated with PTFE.

  The temperature of the heating source 60C is controlled by the control unit 100. The heating roller 62 is heated by the heating source 60C, and as a result, the fixing belt 61 is heated.

  The upper pressure roller 63 is, for example, an outer diameter of 70 [mm], and a solid cored bar made of metal such as iron is used as an elastic layer with a heat resistant silicon rubber (thickness 20 [mm]). (Hardness: Asker-C35 [°]), and further coated with a resin layer coated with PTFE, which is a low-friction, heat-resistant resin having a thickness of 5 to 30 [μm].

  The upper pressure roller 63 is brought into pressure contact with the lower pressure roller 65 driven and rotated by the main drive source (drive motor M3) in the fixing unit 60 via the fixing belt 61. A braking torque generator 66 is connected to the upper pressure roller 63.

  The braking torque generation unit 66 receives a control command from the control unit 100 and generates a braking torque (braking force) in a direction that prevents the rotation of the upper pressure roller 63 as indicated by an arrow G. A plurality of braking force generation motors M1, M2 are provided. The braking force generation motors M1 and M2 are composed of, for example, DC brushless motors of the same type and the same size. Such braking force generation motors M1 and M2 cause the upper pressure roller 63 that rotates following the lower pressure roller 65 to generate a braking force D for rotation in the transport direction (referred to as positive rotation). Apply torque that prevents forward rotation. That is, the motors M1 and M2 generate a braking force D on the upper pressure roller 63.

  A gear mechanism portion is provided between the braking force generation motors M1 and M2 and the upper pressure roller 63, and the braking force of both the motors M1 and M2 is increased in a combined state via the gear mechanism portion. It may be transmitted to the roller 63.

  Furthermore, it demonstrates in detail. FIG. 4 is a diagram illustrating in detail a part of the configuration of the fixing unit 60 illustrated in FIG. 3. As shown in FIG. 4, the fixing unit 60 includes motor substrates B <b> 1 and B <b> 2. Since the configuration of the first motor board B1 is the same as that of the second motor board B2, only the first motor board B1 will be described below as an example.

  The first motor board B1 is equipped with an inverter circuit I for driving the braking force generation motor M1. The inverter circuit I is for driving on and off six (plural) FETs (Field-Effect Transistors) Sa to Sf based on a control signal from the control unit 100. Further, the braking force generation motor M1 includes three coils Lu to Lw serving as stators together with a rotor (not illustrated) serving as a permanent magnet.

  Specifically, the six FETs Sa to Sf are P-type MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors), and the first to third FETs Sa to Sc are connected to the power source and the bases are the control unit 100. Is connected to input a control signal from. The drains of the first to third FETs Sa to Sc are connected to the sources of the fourth to sixth FETs Sd to Sf. Each base of the fourth to sixth FETs Sd to Sf is connected to input a control signal from the control unit 100, and each drain is connected to the ground side.

  Further, signal lines u, v, and w are provided at connection points between the drains of the first to third FETs Sa to Sc and the sources of the fourth to sixth FETs Sd to Sf. v and w are respectively connected to one end of three coils Lu to Lw which are stators. The other ends of the three coils Lu to Lw are connected by a neutral point P, and the braking force generation motor M1 is a so-called star connection.

  In such a configuration, the braking force generation motor M1 can apply an assist force in a direction opposite to the braking force D (that is, a force in a direction that supports the rotation of the drive motor M3). When the assist force is applied, the inverter circuit I receives the control signal from the control unit 100, drives the six FETs Sa to Sf on and off, supplies the drive voltages to the three coils Lu to Lw, and rotates the rotor. .

  On the other hand, when the braking force D is applied, the inverter circuit I turns off the first to third FETs Sa to Sc and turns on the fourth to sixth FETs Sd to Sf. As a result, the coils Lu to Lw are short-circuited, that is, a so-called three-phase short-circuit state is generated, and a torque that maintains the position of the rotor is generated. As a result, a braking force D is generated.

  Refer to FIG. 3 again. The lower fixing unit 60B includes, for example, a lower pressure roller 65 that is a back surface side support member (roller pressure method). The lower pressure roller 65 has an outer diameter of 70 [mm], and heat resistant silicon having a thickness of 1 to 3 [mm] using an outer peripheral surface of a cylindrical cored bar made of aluminum or the like as an elastic layer. It is coated with rubber (hardness: JIS-A30 [°]) and further coated with a resin layer of a PFA tube having a thickness of 30 to 100 [μm].

  The drive motor M3 receives the control command from the control unit 100 and rotates the lower pressure roller 65 in the direction of arrow E (counterclockwise direction). Drive control of the drive motor M3 (for example, rotation on / off, peripheral speed, etc.) is performed by the control unit 100.

  A motor M4 is connected to the rotary shaft end portion 65A of the lower pressure roller 65 via a pressing spring 80 and a rotatable slide cam 82. In response to a control command from the control unit 100, the motor M4 rotates the slide cam 82 about the shaft 84. When the motor M4 rotates the slide cam 82, the pressing spring 80 biases the lower pressure roller 65 in the direction of arrow F. The lower pressure roller 65 is pressed against or separated from the fixing belt 61 according to the rotational position of the slide cam 82. When the lower pressure roller 65 is in pressure contact with the fixing belt 61, the lower pressure roller 65 bites into the elastic layer of the upper pressure roller 63 via the fixing belt 61 according to the rotational position of the slide cam 82. The amount changes. As a result, the fixing nip width d of the fixing nip portion NP formed between the fixing belt 61 and the lower pressure roller 65, that is, the length of the fixing nip portion NP along the conveyance direction of the paper S changes. Specifically, the fixing nip width d increases as the amount of biting of the lower pressure roller 65 with respect to the elastic layer of the upper pressure roller 63 increases. On the other hand, the fixing nip width d decreases as the amount of biting by the lower pressure roller 65 decreases.

  That is, the motor M4, the slide cam 82, and the pressing spring 80 function as a fixing nip width changing portion 68 that changes the fixing nip width d of the fixing nip portion NP.

  The lower pressure roller 65 is pressed against the upper pressure roller 63 via the fixing belt 61 by a fixing nip width changing unit 68 with a predetermined fixing load (for example, 2650 [N]). In this manner, a fixing nip portion NP that holds and conveys the paper S is formed between the fixing belt 61 and the lower pressure roller 65.

  When the lower pressure roller 65 is driven to rotate in the direction of arrow E, the fixing belt 61 is driven to rotate in the direction of arrow B (clockwise direction). Accordingly, the upper pressure roller 63 is driven to rotate in the direction of arrow C (clockwise direction).

  Refer to FIG. 2 again. In the first embodiment, the control unit 100 includes a torque detection unit (torque detection means) 104. The storage unit 72 stores data indicating the correlation between the drive current value to the drive motor M3 and the rotational torque of the drive motor M3. The torque detection unit 104 detects the rotational torque of the drive motor M3. The torque detection unit 104 determines the drive motor from the value of the drive current to the drive motor M3 based on the data stored in the storage unit 72 according to the program stored in the ROM 102. The rotational torque of M3 is detected.

  Here, in the first embodiment, the control unit 100 performs repair control, limit control, and increase control.

  The repair control is control for repairing the surface of the fixing belt 61 in order to eliminate the gloss streak. This repair control is performed at the time of non-fixing when the sheet S is not conveyed to the fixing nip NP. At this time, the control unit 100 controls the fixing nip width changing unit 68 to make the fixing nip width d smaller than the fixing nip width d at the time of fixing. That is, the control unit 100 drives the motor M4 to rotate the slide cam 82, thereby reducing the urging force that the lower pressure roller 65 is urged in the arrow F direction by the pressing spring 80. As a result, the control unit 100 reduces the fixing nip width d (finely pressed state).

  Further, the control unit 100 operates the driving motor M3 in a state where the braking force D is generated in the upper pressure roller 63 by the braking torque generation unit 66 (a plurality of braking force generation motors M1 and M2), thereby fixing the fixing belt. 61 and the lower pressure roller 65 are rotated. At this time, the braking torque generator 66 suppresses the driven rotation of the upper pressure roller 63 and the fixing belt 61, and the fixing belt 61 rotates at a lower peripheral speed than the lower pressure roller 65. That is, a peripheral speed difference is generated between the fixing belt 61 and the lower pressure roller 65.

  As described above, when the thick paper or the paper S having a rough surface passes through the fixing nip portion NP, a paper edge scratch occurs at a position where both side portions of the paper S are in contact with the surface of the fixing belt 61. When an image is formed on the paper S having a larger image forming range than the portion where the paper edge is scratched, a uniform fixing process is not performed in the paper width direction due to the paper edge scratch. Glossy streaks appear in the image.

  The restoration control eliminates such glossy streaks, and each time the rotational speed of the fixing belt 61 and the lower pressure roller 65 is set to rotate, the both are rubbed to cause a paper edge scratch. The surface of the fixing belt 61 is recovered. In particular, since the fixing nip width d is smaller than the fixing nip width d at the time of fixing, the fixing nip width d is in a slippery state, and the fixing belt 61 and the lower pressure roller 65 are sufficiently slid to cause gloss lines. The fixing belt 61 can be repaired by solving.

  The limit control is control for reducing the braking force D generated by the braking torque generator 66 during the repair control. Here, the braking force D of the braking force generation motors M1, M2 may increase due to a change in temperature environment. In this case, the drive motor M3 may be overloaded and the motor M3 may be damaged. Therefore, the control unit 100 determines the braking force generated by the braking torque generation unit 66 when the rotational torque of the drive motor M3 detected by the torque detection unit 104 during the repair control is equal to or greater than a predetermined torque (for example, 0.5 Nm). Limit control to reduce D is executed.

  By executing such restriction control, it is possible to prevent the drive motor M3 from being damaged even if the braking force D of the braking force generation motors M1, M2 increases due to a change in temperature environment or the like.

  Specifically, in the first embodiment, the control unit 100 performs the limit control by turning off one of the plurality of braking force generation motors M1, M2. In the first embodiment, since there are two braking force generation motors M1 and M2, one is turned off. However, when there are three or more braking force generation motors, the two braking force generation motors are turned off. You may make it do. That is, the control unit 100 executes the restriction control by turning off at least one of the plurality of braking force generation motors and maintaining the other in the on state.

  As described above, the control unit 100 can easily perform the limit control by finely adjusting the holding torque of the plurality of braking force generation motors M1 and M2 by turning off at least one of the plurality of braking force generation motors M1 and M2. We are trying to make it.

  Further, the increase control is a control for increasing the braking force D generated by the braking torque generation unit 66 after executing the limit control. When the limit control is executed, the braking force D may become too small so that the fixing belt 61 cannot be sufficiently repaired by the repair control. The control unit 100 performs increase control when the rotational torque of the drive motor M3 detected by the torque detection unit 104 is equal to or less than a second predetermined torque (for example, 0.3 Nm) that is smaller than the predetermined torque. As a result, the control unit 100 increases the braking force D generated by the braking torque generation unit 66 more than the braking force D after the limit control, and the braking force is reduced to such an extent that gloss lines cannot be eliminated. Thus, the drive motor M3 is prevented from being damaged and appropriately repaired.

  Next, the operation of the fixing device according to the first embodiment will be described. FIG. 5 is a flowchart showing the operation of the fixing device according to the first embodiment. Note that the processing shown in FIG. 5 is control (restoration control) that is started when the mode is changed to the refresh mode. The transition to the refresh mode is performed when the refresh mode button displayed on the operation display unit 20 is operated during non-fixing. The transition to the refresh mode is performed when a job being executed is completed (that is, when non-fixing is performed) at a stage where a predetermined number of images (for example, 10,000) has been formed since the end of the previous refresh mode, and It may be performed at least one of when a predetermined time has elapsed since the end of the previous refresh mode (when the job is being executed at the elapsed time, the job is ended).

  As shown in FIG. 5, when the mode is changed to the refresh mode, the control unit 100 controls the fixing nip width changing unit 68 to move the lower pressure roller 65 toward the fixing belt 61 and the upper pressure roller 63. Then, a fine press-bonded state is set (S1). The fixing nip width d in this fine press-bonded state is made smaller than the fixing nip width in the press-bonded state during fixing.

  Next, the control unit 100 turns on the braking force generation motors M1, M2 and the drive motor M3 (S2). Here, turning on the braking force generation motor M1 means turning off the first to third FETs Sa to Sc of the inverter circuit I provided on the first motor substrate B1, turning on the fourth to sixth FETs Sd to Sf, and holding torque. It is said that it will be in the state which generates. The same applies to the braking force generation motor M2. The drive motor M3 is rotated at, for example, 2000 rpm.

  Next, the torque detector 104 detects the rotational torque of the drive motor M3 from the drive current to the drive motor M3 (S3). Thereafter, the control unit 100 determines whether the rotational torque detected in step S3 is equal to or greater than a predetermined torque (S4).

  If it is determined that the torque is not equal to or greater than the predetermined torque (S4: NO), for example, after waiting for a specific time (for example, 5 seconds), the process proceeds to step S3. On the other hand, when it is determined that the torque is equal to or greater than the predetermined torque (S4: YES), the control unit 100 executes limit control and turns off the braking force generation motor M2 (S6). That is, the control unit 100 turns off the fourth to sixth FETs Sd to Sf of the inverter circuit provided on the second motor board B2 for the braking force generation motor M2.

  Thereafter, the torque detector 104 detects the rotational torque of the drive motor M3 from the drive current to the drive motor M3 (S6). Next, the control unit 100 determines whether or not the rotational torque detected in step S6 is equal to or greater than a predetermined torque (S7).

  When it is determined that the torque is not equal to or greater than the predetermined torque (S7: NO), the control unit 100 determines whether it is equal to or less than a second predetermined torque that is smaller than the predetermined torque (S8). If it is determined that the torque is not equal to or less than the second predetermined torque (S8: NO), for example, after waiting for a specific time (for example, 5 seconds), the process proceeds to step S6. If it is determined that the torque is equal to or lower than the second predetermined torque (S8: YES), the process proceeds to step S2. That is, increase control for increasing the braking force D is executed.

  By the way, when it is determined that the rotational torque detected in step S6 is equal to or larger than the predetermined torque (S7: YES), the control unit 100 outputs an error signal (S9). Here, since the braking force generation motor M2 is turned off in the process of step S5, the braking force D generated by the braking torque generation unit 66 is the lowest value. In such a state, when the detected rotational torque is equal to or greater than the predetermined torque, it can be determined that an abnormal state such as biting of various rollers is detected. Therefore, the control unit 100 outputs an error signal. When this error signal is output, the fact is displayed on the display unit 21 or outputted as audio. Thereby, the user can know that it is in an abnormal state.

  Thereafter, the control unit 100 also turns off the braking force generation motor M1 in the same manner as described above (S10), and the process shown in FIG. 5 ends. After the end, for example, the control unit 100 stops the driving motor M3 and releases the fine press-bonding state. Although not shown, the process shown in FIG. 5 is also terminated when a specified time (for example, 3 minutes) has elapsed after the start.

  FIG. 6 is a timing chart for explaining the operation of the fixing device according to the first embodiment, and shows the operating state of the braking force generation motors M1, M2 during the repair control. In FIG. 6, the brakes 1, 2 are on when the holding torque is generated by the braking force generation motors M1, M2, and the off is the holding torque is generated by the braking force generation motors M1, M2. A state that does not occur.

  As shown in FIG. 6A, if the mode is changed to the refresh mode at time 0, the control unit 100 enters the fine press-fit state, turns on the braking force generation motors M1 and M2, and drives the drive motor M3. Let Furthermore, the control unit 100 detects rotational torque from the drive current of the drive motor M3. Then, if the detected torque increases after time t1 and reaches 0.5 Nm, which is a predetermined torque at time t2, the control unit 100 turns off the braking force generation motor M2. After that, when the detected torque is maintained below the predetermined torque and above the second predetermined torque, the repair control ends at time t5 when a specified time has elapsed from time 0.

  Further, as shown in FIG. 6B, after time t1, the restoration control ends at time t5 when a predetermined time has elapsed from time 0 even when the detected torque is maintained below the predetermined torque and above the second predetermined torque. .

  Further, as shown in FIG. 6C, when the detected torque increases after time t1 and reaches a predetermined torque of 0.5 Nm at time t2, the control unit 100 causes the braking force generation motor M2 to move. Turn off. After that, if the detected torque continues to increase and reaches a predetermined torque of 0.5 Nm at time t4, the control unit 100 also turns off the braking force generation motor M1. Then, the control unit 100 outputs an error signal, and the repair control ends.

  Further, as shown in FIG. 6D, when the detected torque increases after time t1 and reaches a predetermined torque of 0.5 Nm at time t2, the control unit 100 turns the braking force generation motor M2 on. Turn off. Thereafter, if the detected torque decreases and reaches the second predetermined torque of 0.3 Nm at time t3, the control unit 100 turns on the braking force generation motor M2. After that, when the detected torque is maintained below the predetermined torque and above the second predetermined torque, the repair control ends at time t5 when a specified time has elapsed from time 0.

  As described above, according to the fixing device according to the first embodiment, the non-fixing state is smaller than the fixing nip width d at the time of fixing and the braking force D is generated in the upper pressure roller 63. In addition, the restoration control for rotating the fixing belt 61 and the lower pressure roller 65 by operating the driving motor M3 is executed, and the limiting control for reducing the braking force D when the rotational torque of the driving motor M3 exceeds a predetermined torque. Execute. For this reason, even if the braking force D increases due to, for example, a change in temperature environment, the braking force D by the braking force generation motors M1 and M2 is reduced when the rotational torque of the drive motor M3 exceeds a predetermined torque. Therefore, by setting the predetermined torque to a value that does not damage the drive motor M3, it is possible to prevent the drive motor M3 from being damaged during the repair control for eliminating the glossy streak.

  In addition, since a plurality of braking force generation motors M1 and M2 that generate the braking force D in a direction that hinders the rotation of the upper pressure roller 63 are provided, the size and cost are large as in the case where the braking force D is generated by one motor. It is not necessary to use a high motor, and the cost can be reduced while saving space. In addition, by providing a plurality of braking force generation motors M1, M2, each of the plurality of braking force generation motors M1, M2 can be controlled, and the braking force D can be adjusted more finely.

  In addition, when the rotational torque of the drive motor M3 is equal to or greater than a predetermined torque, the restriction control is executed by turning off at least one of the plurality of braking force generation motors M1 and M2. Control can be facilitated without adjusting the torque of the motors M1 and M2 and reducing the braking force D.

  In addition, when the rotational torque of the drive motor M3 becomes equal to or less than a second predetermined torque that is smaller than the predetermined torque after the limit control is executed, the braking force D by the braking force generation motors M1 and M2 is increased more than the braking force D after the limit control. Increase control is executed. For this reason, it is possible to prevent the braking force D from being reduced to such an extent that the glossy streak cannot be eliminated by the restriction control, and appropriate repair can be performed while preventing the drive motor M3 from being damaged.

  In addition, when the braking force D generated by the braking force generation motors M1 and M2 is set to the minimum value, an error signal indicating an abnormal state is output when the rotational torque of the drive motor M3 exceeds a predetermined torque. For this reason, for example, it is possible to report an abnormal state in which the rotational torque of the drive motor M3 reaches a predetermined torque or more due to the engagement of various rollers in the fixing device.

  Further, according to the image forming apparatus 1 according to the first embodiment, the image forming unit 40 that forms a toner image on the paper S and the toner image formed by the image forming unit 40 are fixed on the paper. Since the fixing device is provided, it is possible to prevent the drive motor M3 from being damaged during the repair control for eliminating the gloss streak and to output a printed matter with improved image gloss.

  Next, a second embodiment of the present invention will be described. The fixing device and the image forming apparatus according to the second embodiment are the same as those of the first embodiment, but are partially different in configuration and processing. Hereinafter, differences from the first embodiment will be described.

  FIG. 7 is a diagram schematically illustrating a configuration of the fixing unit 60 according to the second embodiment. As shown in FIG. 7, in the second embodiment, the braking torque generation unit 66 includes a single braking force generation motor M5. The braking force generation motor M5 is a DC brushless motor similar to that of the first embodiment, but its size is larger than that of the first embodiment and the generated holding torque is also large.

  FIG. 8 is a diagram showing in detail a part of the configuration of the fixing unit 60 shown in FIG. As shown in FIG. 8, in the second embodiment, the fixing unit 60 includes a motor board B <b> 3 connected to the control unit 100. In addition to the configuration shown in FIG. 4, the motor board B3 includes a switch circuit (adjusting means) SW between the drains of the fourth to sixth FETs Sd to Sf and the ground side.

  The switch circuit SW includes a first switch SW0, a second switch SW1, a first resistor R1, a third switch SW2, and a second resistor R2. The second switch SW1 and the first resistor R1, and the third switch SW2 and the second resistor R2 are connected in series, respectively. The first switch SW0, the second switch SW1 and the first resistor R1, and the third switch SW2 and the second resistor R2 are connected in parallel to each other. Each of the switches SW0 to SW2 is configured to be turned on / off in response to a control signal from the control unit 100, and the resistance value of the first resistor R1 is smaller than the resistance value of the second resistor R2.

  When the braking force D is applied, the inverter circuit I turns off the first to third FETs Sa to Sc and turns on the fourth to sixth FETs Sd to Sf, as in the first embodiment. Further, in the second embodiment, the switch circuit SW turns on one of the first to third switches SW0 to SW2 to turn on the holding torque (that is, the braking force D) generated by the braking force generation motor M5. Can be adjusted.

  For example, when the first switch SW0 is turned on and then the second switch SW1 is turned on, the potential on the inverter circuit I side of the resistor R1 increases, and the holding torque of the braking force generation motor M5 is increased. Decreases. As described above, in the second embodiment, the holding torque of the braking force generation motor M5 can be adjusted by adjusting the voltage value on the drain side of the FETSd to Sf which are the switching elements on the lower arm side.

  Specifically, in the second embodiment, when the holding torque when the first switch SW0 is turned on is 100%, the holding torque when the second switch SW1 is turned on is 70%, and the third switch SW2 is turned on. The holding torque when turned on is 40%.

  Although the switch circuit SW is provided in the second embodiment, the switch circuit SW is configured by a single switching element (such as an FET or a transistor), and the FETSd is changed by changing a PWM value for turning on or off the switching element. The holding torque of the braking force generation motor M5 may be adjusted by adjusting a substantial voltage value on the drain side of Sf.

  Further, the holding torque may be adjusted by changing the PWM value for turning on / off the FETs Sd to Sf without providing the switch circuit SW itself.

  As described above, in the second embodiment, the fixing unit 60 can adjust the holding torque of the braking force generation motor M5. For this reason, the control unit 100 operates the switch circuit SW so as to decrease the holding torque in the limit control, and operates the switch circuit SW so as to increase the holding torque in the increase control.

  9 and 10 are flowcharts showing the operation of the fixing device according to the second embodiment. First, when the mode is shifted to the refresh mode, the processing of FIGS. 9 and 10 is started, and the control unit 100 enters the fine press-bonding state (S11). Next, the control unit 100 turns on the braking force generation motor M5 and the drive motor M3 (S12). Here, the turning on of the braking force generation motor M5 means a state in which a holding torque is generated. Further, the control unit 100 turns on the first switch SW0 of the switch circuit SW and maintains the other switches SW1 and SW2 in the off state (S13). As a result, the braking torque generator 66 applies the braking force D.

  Next, the torque detector 104 detects the rotational torque of the drive motor M3 from the drive current to the drive motor M3 (S14). Thereafter, the control unit 100 determines whether or not the rotational torque detected in step S14 is equal to or greater than a predetermined torque (S15).

  If it is determined that the torque is not equal to or greater than the predetermined torque (S15: NO), for example, after waiting for a specific time (for example, 5 seconds), the process proceeds to step S14. On the other hand, when it is determined that the torque is equal to or greater than the predetermined torque (S15: YES), the control unit 100 executes limit control. That is, the control unit 100 turns off the first switch SW0 (S16) and turns on the second switch SW1 (S17). Then, the process proceeds to step S18.

  In the processing of steps S18 to S20, the same processing as that of steps S6 to 8 shown in FIG. 5 is executed. If it is determined that the rotational torque detected in step S18 is equal to or lower than the second predetermined torque (S20: YES), the control unit 100 turns off the second switch SW1 (S21), and the process proceeds to step S13. To do. In step S13, the first switch SW0 is turned on. That is, increase control for increasing the braking force D is executed.

  When it is determined that the rotational torque detected in step S18 is equal to or greater than the predetermined torque (S19: YES), the control unit 100 further executes limit control. That is, the control unit 100 turns off the second switch SW1 (S22) and turns on the third switch SW2 (S23). And a process transfers to step S24 shown in FIG.

  In the processing of steps S24 to S26, the same processing as that of steps S18 to 20 is executed. Then, when it is determined that the rotational torque detected in step S24 is equal to or less than the second predetermined torque (S24: YES), the control unit 100 turns off the third switch SW2 (S27), and the process is the step of FIG. The process proceeds to S17. In step S17, the second switch SW1 is turned on. That is, increase control for increasing the braking force D is executed.

  If it is determined that the rotational torque detected in step S24 is equal to or greater than the predetermined torque (S24: YES), the control unit 100 outputs an error signal (S28). Here, since only the third switch SW2 is turned on in the processing of steps S22 and S23, the braking force D generated by the braking torque generator 66 is the lowest value. In such a state, when the detected rotational torque is equal to or greater than the predetermined torque, the control unit 100 determines that the state is abnormal and outputs an error signal. When this error signal is output, the fact is left outside as in the first embodiment.

  Thereafter, the control unit 100 turns off the braking force generation motor M5 (S29). That is, the control unit 100 turns off the fourth to sixth FETs Sd to Sf of the inverter circuit I provided on the motor board B3 for the braking force generation motor M5. Next, the control unit 100 turns off the third switch SW2 (S30), and the processing illustrated in FIGS. 9 and 10 ends.

  After the end, for example, the control unit 100 stops the driving motor M3 and releases the fine press-bonding state. Although illustration is omitted, the processes shown in FIGS. 9 and 10 are also terminated when a specified time (for example, 3 minutes) has elapsed after the start.

  FIG. 11 is a timing chart for explaining the operation of the fixing device according to the second embodiment, and shows the operating state of the braking force generation motor M5 during the repair control. In FIG. 11, “brake off” refers to a state in which the holding torque is not generated by the braking force generation motor M5. The brake 100% means that only the first switch SW0 is turned on, the brake 70% means that only the second switch SW1 is turned on, and the brake 40% means that only the third switch SW2 is turned on. State.

  As shown in FIG. 11A, if the mode is changed to the refresh mode at time 0, the control unit 100 enters the fine press-fit state, turns on the braking force generation motor M5, and drives the drive motor M3. Furthermore, the control unit 100 detects rotational torque from the drive current of the drive motor M3. Then, if the detected torque increases after time t11 and reaches 0.5 Nm, which is a predetermined torque at time t12, the control unit 100 turns off the first switch SW0 and turns on the second switch SW1. After that, when the detected torque is maintained below the predetermined torque and above the second predetermined torque, the repair control ends at time t15 when a specified time has elapsed from time 0.

  Further, as shown in FIG. 11B, when the detected torque increases after time t11 and reaches a predetermined torque of 0.5 Nm at time t12, the control unit 100 turns off the first switch SW0. At the same time, the second switch SW1 is turned on. Thereafter, if the detected torque decreases and reaches the second predetermined torque of 0.3 Nm at time t13, the control unit 100 turns on the first switch SW0 and turns off the second switch SW1. After that, when the detected torque is maintained below the predetermined torque and above the second predetermined torque, the repair control ends at time t15 when a specified time has elapsed from time 0.

  Further, as shown in FIG. 11C, if the detected torque increases after time t11 and reaches a predetermined torque of 0.5 Nm at time t12, the control unit 100 turns off the first switch SW0. At the same time, the second switch SW1 is turned on. Thereafter, if the detected torque temporarily decreases but increases after the decrease, and reaches a predetermined torque of 0.5 Nm at time t13, the control unit 100 turns off the second switch SW1 and the third switch. Turn on SW2. After that, when the detected torque is maintained below the predetermined torque and above the second predetermined torque, the repair control ends at time t15 when a specified time has elapsed from time 0.

  Further, as shown in FIG. 11D, when the detected torque increases after time t11 and reaches a predetermined torque of 0.5 Nm at time t12, the control unit 100 turns off the first switch SW0. At the same time, the second switch SW1 is turned on. Thereafter, if the detected torque temporarily decreases but increases after the decrease, and reaches a predetermined torque of 0.5 Nm at time t13, the control unit 100 turns off the second switch SW1 and the third switch. Turn on SW2. Furthermore, after that, if the detected torque temporarily decreases but increases after the decrease and reaches 0.5 Nm which is a predetermined torque at time t14, the control unit 100 turns off the third switch SW2 and generates an error. Output a signal. Then, the repair control ends.

  As described above, according to the fixing device and the image forming apparatus 1 according to the second embodiment, the same effects as those of the first embodiment can be obtained.

  Furthermore, according to the second embodiment, when the rotational torque of the drive motor M3 is equal to or greater than a predetermined torque, the braking force D of the single braking force generation motor M5 is reduced by controlling the switch circuit SW, Perform limit control. For this reason, it is possible to prevent the drive motor M3 from being damaged without using the plurality of braking force generation motors M1, M2.

  As described above, the fixing device and the image forming apparatus according to the present invention have been described based on the embodiments. However, the present invention is not limited thereto, and modifications may be made without departing from the spirit of the present invention. The embodiments may be combined.

  For example, in the above-described embodiment, a belt nip type fixing device is used, but the fixing device is not limited to this, and a roller nip type may be used.

  Further, in the present exemplary embodiment, the fixing device is housed in the image forming apparatus 1, but not limited thereto, the fixing device may be housed in another device such as a post-processing device.

  In addition, the various structures and numerical values described above are not limited to those described above, and can be changed as appropriate.

  Furthermore, in the above-described embodiment, the braking torque generation unit 66 is configured to include two motors M1, M2 or a single motor M5, but is not limited thereto, and includes three or more motors. It may be. Further, the fixing circuit 60 shown in the first embodiment may include the switch circuit SW (adjustment means) shown in the second embodiment, and the holding torque may be adjusted for each of the plurality of motors M1 and M2.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Image reading part 11 Automatic document feeder 12 Document image scanning apparatus 12a CCD sensor 20 Operation display part 21 Display part 22 Operation part 30 Image processing part 40 Image forming part 50 Paper conveyance part 60 Fixing part 60a Frame 61 Fixing belt (fixing surface side member)
62 Heating roller 63 Upper pressure roller (fixing surface side member)
64 Tension member 65 Lower pressure roller (back side member)
66 Braking torque generating unit 68 Fixing nip width changing unit 71 Communication unit 72 Storage unit 80 Pressing spring 82 Slide cam 100 Control unit 101 CPU
102 ROM
103 RAM
104 Torque detection unit (torque detection means)
d Fixing nip width M1, M2, M5 Braking force generating motor M3 Drive motor M4 Motor NP Fixing nip S Paper

Claims (7)

A fixing surface side member disposed on the fixing surface side of the paper on which the toner image is formed;
A back side member that forms a fixing nip portion that sandwiches and conveys the sheet in a state of being pressed against the fixing side member;
A drive motor for rotationally driving the back side member;
Torque detecting means for detecting rotational torque of the drive motor;
A fixing nip width changing portion for changing a fixing nip width of the fixing nip portion;
Braking force generating means for generating a braking force in a direction that prevents rotation of the fixing surface side member;
At the time of non-fixing, the fixing nip width changing portion is controlled to make the fixing nip width smaller than the fixing nip width at the time of fixing, and the braking force generating means generates a braking force on the fixing surface side member. In this state, the drive motor is operated to perform the repair control to rotate the fixing surface side member and the back surface side member, and the rotation of the drive motor detected by the torque detection means during the repair control. Control means for executing limit control for reducing the braking force generated by the braking force generation means when the torque is equal to or greater than a predetermined torque;
A fixing device comprising: The fixing device according to claim 1, wherein the braking force generation unit includes a plurality of braking force generation motors that generate a braking force in a direction that prevents rotation of the fixing surface side member. The control means turns off at least one of the plurality of braking force generation motors when the rotational torque of the drive motor detected by the torque detection means during the repair control is equal to or greater than a predetermined torque, The fixing device according to claim 2, wherein the restriction control is executed. The braking force generation means includes a single braking force generation motor that generates a braking force in a direction that prevents rotation of the fixing surface side member, and an adjustment means that adjusts the braking force of the single braking force generation motor; Have
The control means controls the adjustment means to control the single braking force generation motor when the rotational torque of the drive motor detected by the torque detection means during the repair control is equal to or greater than a predetermined torque. The fixing device according to claim 1, wherein the restriction control is executed by reducing power. The control means generates the braking force generation means when the rotational torque of the drive motor detected by the torque detection means becomes equal to or less than a second predetermined torque smaller than the predetermined torque after executing the limit control. The fixing device according to any one of claims 1 to 4, wherein an increase control for increasing a braking force to be applied to a braking force after the limit control is executed. When the control means executes the limit control and sets the braking force generated by the braking force generation means to a minimum value, the rotational torque of the drive motor detected by the torque detection means is greater than or equal to a predetermined torque. The fixing device according to any one of claims 1 to 5, wherein an error signal indicating an abnormal state is output. An image forming unit that forms a toner image on paper;
The fixing device according to claim 1, wherein the toner image formed by the image forming unit is fixed on a sheet.
An image forming apparatus comprising:

Images