JP2013238638A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of preventing uneven quality of fixing in a sheet width direction.SOLUTION: The image forming apparatus includes: a fixing unit having a fixing roller 210 for fixing a toner image on a recording sheet by heating and a pressurizing roller 220 for pressurizing the recording sheet against the fixing roller 210; an external heating roller 230 for externally heating the fixing roller 210; a first drive part 180 for swinging the fixing unit in a sheet width direction that is orthogonal to the conveyance direction of the recording sheet; a second drive part 182 for swinging the external heating roller 230 in the sheet width direction; and a control part 200 for controlling the first drive part 180 and the second drive part 182 to change relative positions of the fixing unit and the external heating roller 230 in the sheet width direction. Specifically, the control part 200 controls the first drive part 180 and the second drive part 182 to swing the fixing unit and the external heating roller 230 in opposite directions to each other.

Description

  The present invention relates to an image forming apparatus.

  In general, in an image forming apparatus that forms an image by an electrophotographic process, the surface of an image carrier (photosensitive drum or the like) is charged to a predetermined potential, and this is subjected to image exposure to form an electrostatic latent image. Then, the latent image on the surface of the photosensitive drum is developed by a developing unit using a developer (toner) and visualized as a toner image. The obtained toner image is transferred to a recording sheet conveyed to a photosensitive drum, the recording sheet carrying the toner image is conveyed to a fixing device, and an unfixed toner image on the recording sheet is heated and fixed by the fixing device, and the sheet An image is formed on top.

  By the way, in the image forming apparatus, when a large amount of recording paper of the same size is processed in the fixing device, the edge portion of the recording paper always contacts the same position on the fixing roller. For this reason, there is a problem that the edge contact position of the fixing roller is scratched along the circumference, and the image quality is deteriorated due to the scratch.

  In order to solve this problem, an image forming apparatus in which the position at which the edge portion of the recording paper comes into contact with the fixing roller is always changed by swinging the fixing device in the paper width direction perpendicular to the paper conveyance direction. Has been developed (see, for example, Patent Document 1).

JP 2006-91224 A

  However, in the technique described in Patent Document 1, since the entire fixing device is swung, the relative position between the position of the recording paper in the paper width direction and the heating range of the fixing device in the paper width direction varies. . As a result, there is a problem that a fixing temperature difference occurs at both ends of the recording paper in the paper width direction, and the fixing quality in the paper width direction becomes non-uniform.

  An object of the present invention is to provide an image forming apparatus capable of preventing non-uniform fixing quality in the paper width direction.

An image forming apparatus according to the present invention includes:
A fixing unit having a fixing member that heats and fixes a toner image on the recording paper, and a pressure roller that presses the recording paper between the fixing member; and
An external heating roller for heating the fixing member from the outside;
A first swinging unit that swings the fixing unit in a sheet width direction orthogonal to the conveyance direction of the recording sheet;
A second swinging portion that swings the external heating roller in the paper width direction;
A control unit that controls the first swinging unit and the second swinging unit such that a relative position between the fixing unit and the external heating roller in the sheet width direction changes;
Is provided.

  According to the present invention, it is possible to provide an image forming apparatus capable of preventing non-uniform fixing quality in the paper width direction.

1 is a control block diagram of an image forming apparatus showing an embodiment according to the present invention. FIG. 3 is a diagram illustrating a configuration of a fixing unit illustrating an embodiment according to the present invention. FIG. 3 is a diagram illustrating a configuration of a fixing unit illustrating an embodiment according to the present invention. It is a figure which shows operation | movement of the fixing | fixed part which shows embodiment which concerns on this invention. 6 is a flowchart illustrating an operation example of the image forming apparatus according to the exemplary embodiment of the present invention. FIG. 3 is a diagram illustrating a configuration example of a fixing unit according to an embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. An image forming apparatus 100 shown in FIG. 1 forms an image on a recording sheet by an electrophotographic process. The image forming apparatus 100 includes a document reading unit 110, an operation display unit 120, an image processing unit 130, an image writing unit 140, an image forming unit 150, a conveying unit 160, a fixing unit 170, a first driving unit 180, and a second driving unit. 182, a third drive unit 184, a contact / separation state detection unit 190, and a control unit 200.

  The control unit 200 includes a CPU (Central Processing Unit) 201, a ROM (Read Only Memory) 202, a RAM (Random Access Memory) 203, and the like. The CPU 201 reads a program corresponding to the processing content from the ROM 202 and develops it in the RAM 203, and centrally controls the operation of each block of the image forming apparatus 100 in cooperation with the developed program. At this time, various data stored in the storage unit 172 are referred to. The storage unit 172 includes, for example, a nonvolatile semiconductor memory (so-called flash memory) or a hard disk drive.

  The control unit 200 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 171. I do. For example, the control unit 200 receives image data transmitted from an external device, and forms an image on a recording sheet based on the image data (input image data). The communication unit 171 includes a communication control card such as a LAN card, for example.

  The document reading unit 110 optically scans the document conveyed on the contact glass, forms an image of reflected light from the document on a light receiving surface of a CCD (Charge Coupled Device) sensor, and reads the document. The document is conveyed onto the contact glass by an automatic document feeder (ADF). However, the document may be manually placed on the contact glass.

  The operation display unit 120 has a touch panel screen. Input operations for various instructions and settings performed by the user can be performed via a touch panel screen. The instruction / setting information is handled by the control unit 200 as job information.

  The image processing unit 130 includes a circuit that performs analog-digital (A / D) conversion processing and a circuit that performs digital image processing. The image processing unit 130 generates digital image data from the analog image signal acquired by the CCD sensor of the document reading unit 110 by A / D conversion processing, and outputs the digital image data to the image writing unit 140.

  The image writing unit 140 emits a laser beam based on the digital image data generated by the image processing unit 130 and irradiates the photoconductive drum of the image forming unit 150 with the emitted laser beam, whereby a photoconductor An electrostatic latent image is formed on the drum (exposure process).

  The image forming unit 150 is configured to execute a charging process performed before the exposure process, a development process performed after the exposure process, a transfer process after the development process, and a cleaning process after the transfer process in addition to the exposure process described above. It has. In the charging process, the image forming unit 150 uniformly charges the surface of the photosensitive drum by corona discharge from the charging device. In the developing process, the image forming unit 150 forms a toner image on the photosensitive drum by attaching toner contained in the developer in the developing device to the electrostatic latent image on the photosensitive drum.

  In the transfer process, the image forming unit 150 primarily transfers the toner image on the photosensitive drum onto the intermediate transfer belt. Further, the image forming unit 150 transfers the toner image on the intermediate transfer belt onto the recording paper conveyed by the conveyance unit 160.

  In the cleaning process, the image forming unit 150 removes the toner remaining on the photosensitive drum after the transfer process by bringing a brush or the like into contact with the photosensitive drum.

  The fixing unit 170 includes a fixing roller and a pressure roller extending in parallel with the fixing roller. The pressure roller is disposed in pressure contact with the fixing roller. A fixing nip portion is formed at a portion where the fixing roller and the pressure roller are in contact with each other. The fixing unit 170 fixes the toner image on the recording paper by applying heat and pressure to the toner image on the recording paper introduced into the fixing nip (heating fixing) (fixing step). As a result, a fixed toner image is formed on the recording paper. The recording paper heated and fixed by the fixing unit 170 is discharged to the outside of the image forming apparatus 100.

  Next, a specific configuration of the fixing unit 170 will be described with reference to FIG. The fixing unit 170 includes a fixing roller 210 that functions as a fixing member, a pressure roller 220, and an external heating roller 230.

  The fixing roller 210 is supported so that the outer peripheral surface can be rotated. A heater lamp 240 for heating the fixing roller 210 is disposed near the center of the fixing roller 210 along the rotation axis direction of the fixing roller 210. The power supplied to the heater lamp 240 is, for example, 1500 [W]. When the heater lamp 240 is energized under the control of the control unit 200, the heater lamp 240 emits light and emits infrared rays. By the infrared radiation, the inner peripheral surface of the fixing roller 210 is heated by absorbing infrared rays, and the entire fixing roller 210 is heated. The fixing roller 210 is heated to a predetermined temperature (for example, 180 [° C.]), and heats the recording paper 270 on which an unfixed toner image passing through the fixing nip 260 is formed.

  The fixing roller 210 swings in the paper width direction orthogonal to the conveyance direction of the recording paper 270. The swing mechanism that performs this operation will be described later.

  The fixing roller 210 has a three-layer structure in which a metal core, an elastic layer, and a release layer are formed in this order from the inside. For the metal core, for example, a metal such as iron, stainless steel, aluminum, copper, or an alloy thereof is used. For example, silicon rubber is used for the elastic layer. For the release layer, for example, PFA (copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether) and fluororesin such as PTFE (polytetrafluoroethylene) are used.

  The pressure roller 220 presses the outer peripheral surface of the fixing roller 210 and rotates. Similar to the fixing roller 210, the pressure roller 220 has a three-layer structure in which a core metal, an elastic layer, and a release layer are formed in order from the inside. For the metal core, for example, a metal such as iron, stainless steel, aluminum, copper, or an alloy thereof is used. For example, silicon rubber is used for the elastic layer. For the release layer, for example, PFA (copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether) and fluororesin such as PTFE (polytetrafluoroethylene) are used.

  The fixing roller 210 is rotationally driven by a drive motor (not shown), and is configured so that the recording paper 270 can pass through the fixing nip portion 260. The pressure roller 220 rotates following the rotation of the fixing roller 210. Therefore, the fixing roller 210 and the pressure roller 220 rotate in opposite directions as shown in FIG.

  The outer heating roller 230 is supported so that the outer peripheral surface can go around. A heater lamp 250 that heats the external heating roller 230 is disposed near the center of the external heating roller 230 along the direction of the rotation axis of the external heating roller 230. The power supplied to the heater lamp 250 is, for example, 500 [W]. When the heater lamp 250 is energized under the control of the control unit 200, the heater lamp 250 emits light and emits infrared rays. Due to infrared radiation, the inner peripheral surface of the external heating roller 230 is heated by absorbing infrared rays, and the entire external heating roller 230 is heated. The external heating roller 230 is heated to a predetermined temperature (for example, 180 [° C.]) and contacts the fixing roller 210 to heat the fixing roller 210 from the outside.

  The external heating roller 230 contacts or separates from the fixing roller 210 by moving in the direction of arrow A in FIG. A contact / separation mechanism that performs this operation will be described later. FIG. 2 shows a state in which the external heating roller 230 is in contact with the fixing roller 210. The external heating roller 230 swings in the paper width direction. The swing mechanism that performs this operation will be described later.

  Next, the swinging mechanism of the fixing roller 210 and the external heating roller 230 and the contact / separation mechanism of the external heating roller 230 will be described with reference to FIG. FIG. 3 is a view of the fixing unit 170 as viewed from the right side in FIG.

  As shown in FIG. 3, the external heating roller 230 is held by the holding unit 300 so as to be swingable in the paper width direction. The holding unit 300 includes a holding body 310, springs 320 and 330, and second holding bodies 340 and 350.

  One end of the spring 320 is connected to the left end inside the holding body 310, and the other end is connected to the left end of the second holding body 340, and the second holding body starts from the left end inside the holding body 310. A biasing force is generated at the left end of 340.

  One end of the spring 330 is connected to the right end inside the holding body 310, and the other end is connected to the right end of the second holding body 350, and the second holding body starts from the right end inside the holding body 310. A biasing force is generated at the right end of 350.

  The second holding bodies 340 and 350 hold the external heating roller 230 via, for example, a bearing (not shown).

  The urging forces of the springs 320 and 330 are set to the same value. Therefore, in the state before the swing of the external heating roller 230 is started, the center position of the external heating roller 230 in the paper width direction coincides with the center position of the holding body 310 in the paper width direction.

  A slide cam 360 is provided at the shaft central portion of the holding body 310. The slide cam 360 can rotate around the fulcrum 365. The third drive unit 184 rotates the slide cam 360 when receiving a drive command from the control unit 200. The holding body 310 (external heating roller 230) moves in the vertical direction (that is, the contact separation direction) in the drawing by the rotation of the slide cam 360. The 3rd drive part 184 is constituted by combination of a motor, a gear, etc., for example. Note that the slide cam 360 and the third drive unit 184 function as a contact separation unit.

  A slide cam 370 is provided at the left end of the shaft of the holding body 310. The slide cam 370 can rotate around the fulcrum 375. The second drive unit 182 rotates the slide cam 370 when receiving a drive command from the control unit 200. The holding member 310 (external heating roller 230) moves in the left-right direction (that is, the paper width direction) in the drawing by the rotation of the slide cam 370. The 2nd drive part 182 is comprised by the combination of a motor, a gear, etc., for example. The second drive unit 182 functions as a second swing unit.

  In the vicinity of both end portions of the holding body 310, an irradiation unit 190a and a light receiving unit 190b constituting the contact / separation state detection unit 190 are provided. The irradiation unit 190a irradiates the sensor light toward the light receiving unit 190b. The light receiving unit 190b receives the sensor light emitted from the irradiation unit 190a. While receiving the sensor light emitted from the irradiation unit 190a, the light receiving unit 190b notifies the control unit 200 to that effect.

  In the present embodiment, when the external heating roller 230 is in contact with the fixing roller 210, the irradiation unit 190a and the light receiving unit 190b are blocked by the external heating roller 230. For this reason, the light receiving unit 190b cannot receive the sensor light emitted from the irradiation unit 190a. On the other hand, when the external heating roller 230 is separated from the fixing roller 210, the irradiation unit 190a and the light receiving unit 190b are not blocked by the external heating roller 230. Therefore, the light receiving unit 190b can receive the sensor light emitted from the irradiation unit 190a.

  The fixing roller 210 and the pressure roller 220 are held by a holding body 380 so as to be rotatable and swingable in the paper width direction in a state where they are pressed against each other.

  A slide cam 390 is provided at the center of the shaft of the holding body 380. The slide cam 390 can rotate around the fulcrum 395. When receiving a driving command from the control unit 200, the first driving unit 180 rotates the slide cam 390. As the slide cam 390 rotates, the holding body 380 (the fixing roller 210 and the pressure roller 220, hereinafter referred to as a fixing unit) moves in the left-right direction (that is, the sheet width direction) in the drawing. The 1st drive part 180 is comprised by the combination of a motor, a gear, etc., for example. The first driving unit 180 functions as a first swinging unit.

  Next, a specific operation of the fixing unit 170 will be described with reference to FIG. FIG. 4A shows a state in which the first drive unit 180 that has received a drive command from the control unit 200 rotates the slide cam 390, so that the fixing unit moves in the left direction of the drawing indicated by an arrow. When the fixing unit moves, a surface frictional force acts between the external heating roller 230 and the fixing roller 210, and the external heating roller 230 moves with the fixing unit in the left direction of the drawing against the urging force of the springs 320 and 330. To do.

  When the movement amount of the external heating roller 230 exceeds a predetermined value, the third driving unit 184 rotates the slide cam 360 to move the holding body 310 (external heating roller 230) upward in the drawing (that is, in the separation direction). Move to. This state is shown in FIG. As shown in FIG. 4B, when the external heating roller 230 is separated from the fixing roller 210, a restoring force acts on the springs 320 and 330, and the external heating roller 230 has the center position of the external heating roller 230 at the holder 310. Move to the right in the figure until it coincides with the center position. The control unit 200 determines that the external heating roller 230 is separated from the fixing roller 210 by receiving a notification from the light receiving unit 190b that the sensor light emitted from the irradiation unit 190a is received.

  In FIG. 4C, the second drive unit 182 rotates the slide cam 370 to move the holding body 310 (external heating roller 230) in the right direction in the drawing (that is, the direction opposite to the moving direction of the fixing unit). The state after being moved by the same amount as the moving amount of the fixing unit is shown. The control unit 200 completes the movement of the external heating roller 230 based on the detection results of various sensors that detect the amount of rotation of the motor, gear, and the like that constitute the second drive unit 182 and the swing position of the holding body 310. Judge that you did.

  FIG. 4D shows that the third driving unit 184 rotates the slide cam 360 to move the holding body 310 (external heating roller 230) downward in the drawing (that is, the contact direction). The state after bringing the fixing roller 210 into contact again is shown.

  As described above, even when the temperature of the fixing roller 210 in contact with the right end portion of the recording paper decreases due to the movement of the fixing unit in the left direction in the drawing, the decreased temperature is opposite to the moving direction of the fixing unit. The heat from the external heating roller 230 moved in the direction can be complementarily increased. Therefore, the temperature distribution in the sheet width direction of the fixing roller 210 can be made uniform. Accordingly, it is possible to prevent occurrence of a fixing temperature difference in the sheet width direction of the recording sheet, and in turn, to prevent uneven fixing quality in the sheet width direction.

  FIG. 5 is a flowchart illustrating an operation example of the image forming apparatus 100 according to the present embodiment. The process shown in FIG. 5 is performed every time the fixing unit is swung. It is assumed that the external heating roller 230 is in contact with the fixing roller 210 before the process of step S100.

  First, the control unit 200 determines whether or not the amount of movement of the external heating roller 230 exceeds a predetermined value (step S100). The control unit 200 can determine whether the amount of movement of the external heating roller 230 exceeds a predetermined value by detecting the amount of rotation of the slide cam 390 (that is, the amount of movement of the fixing unit).

  If the controller 200 determines that the amount of movement of the external heating roller 230 does not exceed the predetermined value (step S100, NO), the image forming apparatus 100 ends the processing in FIG. On the other hand, when the control unit 200 determines that the amount of movement of the external heating roller 230 exceeds the predetermined value (step S100, YES), the control unit 200 controls the third drive unit 184 and the slide cam 360. , The external heating roller 230 is separated from the fixing roller 210 (step S120).

  Next, the control unit 200 controls the second driving unit 182 to rotate the slide cam 370, thereby moving the external heating roller 230 in the direction opposite to the moving direction of the fixing unit and the same moving amount as the fixing unit. Move by the amount (step S140). Finally, the control unit 200 controls the third driving unit 184 and rotates the slide cam 360 to move the external heating roller 230 in the contact direction, thereby bringing the external heating roller 230 and the fixing roller 210 into contact again. (Step S160). When the process of step S160 is completed, the image forming apparatus 100 ends the process in FIG.

  As described above in detail, the present embodiment includes the fixing roller 210 that heats and fixes the toner image on the recording paper, and the pressure roller 220 that presses the recording paper between the fixing roller 210. The fixing unit, the external heating roller 230 that heats the fixing roller 210 from the outside, the first drive unit 180 that swings the fixing unit in the paper width direction orthogonal to the conveyance direction of the recording paper, and the external heating roller 230 And a control unit 200 that controls the first drive unit 180 and the second drive unit 182 so that the relative position between the fixing unit and the external heating roller 230 in the paper width direction changes. With. Specifically, the control unit 200 controls the first driving unit 180 and the second driving unit 182 so that the fixing unit and the external heating roller 230 are swung in directions opposite to each other.

  According to the present embodiment configured as described above, even if the temperature of the fixing roller 210 contacting the right end portion of the recording sheet is decreased due to, for example, the leftward movement of the fixing unit, the decreased temperature is fixed. The heat can be complementarily increased by the heat from the external heating roller 230 moved in the direction opposite to the moving direction of the unit. Further, the movement of the fixing unit increases the portion of the fixing unit that does not contact the recording paper, but the heat of the portion can be transferred to the external heating roller 230. Therefore, the temperature distribution in the sheet width direction of the fixing roller 210 can be made uniform. Accordingly, it is possible to prevent occurrence of a fixing temperature difference in the sheet width direction of the recording sheet, and in turn, to prevent uneven fixing quality in the sheet width direction.

  In the present embodiment, the third heating unit 184 is provided to bring the external heating roller 230 into contact with the fixing roller 210 or separate from the fixing roller 210. When the control unit 200 controls the second driving unit 182 to swing the external heating roller 230, the control unit 200 controls the third driving unit 184 to separate the external heating roller 230 from the fixing roller 210. Accordingly, when the external heating roller 230 swings, a surface frictional force acts between the external heating roller 230 and the fixing roller 210, that is, the stress that the external heating roller 230 and the fixing roller 210 receive each other is prevented from increasing. it can. Therefore, the lifetime of the external heating roller 230 and the fixing roller 210 can be extended.

  In the above embodiment, the example in which the heater lamp 250 is used as the heat source for heating the external heating roller 230 has been described, but the present invention is not limited to this. For example, an IH heater, a resistance heating element, or the like can be used as a heat source for heating the external heating roller 230. Also, a heat source using ultrasonic waves may be used.

  In the above embodiment, an example in which the fixing nip 260 is formed by the fixing roller 210 and the pressure roller 220 has been described as a configuration method of the fixing unit 170, but the present invention is not limited to this. For example, as shown in FIG. 6, a belt system in which the fixing roller 210 is pressed by the pressure roller 220 via the fixing belt 290 functioning as a fixing member to form the fixing nip portion 260 can be employed. The fixing belt 290 is stretched between the heating roller 280 including the heater lamp 240 and the fixing roller 210. The external heating roller 230 including the heater lamp 250 contacts the fixing belt 290 and heats the fixing belt 290 from the outside. According to this belt system, the contact time (contact area) between the external heating roller 230 and the fixing member can be increased as compared with the roller system, and the fixing member can be efficiently heated.

  In the above embodiment, the example in which the slide cams 370 and 390 are used as the swinging mechanism of the fixing unit and the external heating roller 230 has been described. However, the present invention is not limited to this. For example, a rack and pinion mechanism in which a small-diameter circular gear (pinion) and a rack with teeth attached to a flat bar can be adopted as the swinging mechanism of the fixing unit and the external heating roller 230. . The rack incorporates a fixing unit or an external heating roller 230. Note that the fixing unit and the swing mechanism of the external heating roller 230 are preferably provided in the main body of the image forming apparatus 100. When the swinging mechanism is provided in the fixing unit 170, the configuration of the fixing unit 170 is increased in size, and when the fixing unit 170 is replaced, parts that do not need to be replaced (for example, parts that configure the swinging mechanism) are discarded. This is because it is uneconomical.

  In the above embodiment, the example in which the external heating roller 230 is separated from the fixing roller 210 after the fixing unit is moved has been described. However, the present invention is not limited to this. For example, the fixing unit may be moved after the external heating roller 230 is separated from the fixing roller 210.

  In the above embodiment, the control unit 200 may control the second driving unit 182 to swing the external heating roller 230 based on the position of the fixing unit in the paper width direction. Further, the control unit 200 may control the first driving unit 180 to swing the fixing unit based on the position of the external heating roller 230 in the paper width direction.

  In the above embodiment, the control unit 200 may control the second driving unit 182 so as not to swing the external heating roller 230. For example, when the heat generation width of the heater lamp 240 of the fixing roller 210 is sufficiently wider than the width of the recording paper, the occurrence of a fixing temperature difference in the paper width direction of the recording paper is prevented without swinging the external heating roller 230. be able to.

  In the above embodiment, the control unit 200 may control the first driving unit 180 so as not to swing the fixing unit. For example, if the recording paper is prevented from being damaged by the swinging of the recording paper in the paper width direction, the temperature distribution of the fixing roller 210 in the paper width direction is made uniform by swinging only the external heating roller 230. Can be

  In the above embodiment, the example in which the fixing unit and the external heating roller 230 are swung in the opposite directions has been described, but the present invention is not limited to this. For example, the fixing unit and the external heating roller 230 may be swung with different swing amounts in the same direction. In short, the entire recording paper in the paper width direction may be heated by the heater lamp 240 of the fixing roller 210 and the heater lamp 250 of the external heating roller 230.

  In the above embodiment, the control unit 200 controls the first driving unit 180 and the second driving unit 182 so that the number of swings of the external heating roller 230 is less than the number of swings of the fixing unit. Also good. For example, the swinging of the fixing unit may be performed only during paper passing for the purpose of avoiding paper wrinkles and image noise. The paper wrinkles are generated due to deterioration of paper passing properties in the fixing nip portion 260. In this case, the swinging amount of the fixing unit per one time becomes very small (for example, 0.1 [mm] or less). However, the swing of the external heating roller 230 for the purpose of improving the temperature distribution is finely performed at each swing timing of the fixing unit because the effect of improving the temperature distribution cannot be expected with a moving amount of about 1 [mm] or less. There is no need. Therefore, for example, every time the fixing unit is swung 10 times, the external heating roller 230 is swung once, so that the number of times the external heating roller 230 is swung is controlled to be smaller than the number of times the fixing unit is swung. Thereby, unnecessary swinging operation of the external heating roller 230 can be omitted, which is more preferable.

  In the above embodiment, the control unit 200 determines that the rocking width of the external heating roller 230 (for example, ± 8 [mm] reciprocation with respect to the reference position) is the rocking width of the fixing unit (for example, the reference position). The first drive unit 180 and the second drive unit 182 may be controlled so as to be wider than the reciprocation of ± 5 [mm]. In the present embodiment, the external heating roller 230 is an auxiliary heating source for the fixing unit, and thus the power supplied to the heater lamp 250 is set small. In this case, if the swinging width of the external heating roller 230 is the same as the swinging width of the fixing unit, the temperature distribution of the fixing unit cannot be sufficiently compensated. Therefore, the temperature distribution of the fixing unit can be sufficiently supplemented by swinging the external heating roller 230 larger.

  In addition, each of the above-described embodiments is merely an example of actualization in carrying out the present invention, and the technical scope of the present invention should not be construed as being limited thereto. That is, the present invention can be implemented in various forms without departing from the gist or the main features thereof.

DESCRIPTION OF SYMBOLS 100 Image forming apparatus 110 Document reading part 120 Operation display part 130 Image processing part 140 Image writing part 150 Image forming part 160 Conveyance part 170 Fixing part 171 Communication part 172 Storage part 180 1st drive part 182 2nd drive part 184 3rd Drive unit 190 Contact / separation state detection unit 200 Control unit 201 CPU
202 ROM
203 RAM
210 Fixing roller 220 Pressure roller 230 External heating roller 240, 250 Heater lamp 260 Fixing nip part 270 Recording paper 280 Heating roller 290 Fixing belt 300 Holding part 310, 380 Holding body 320, 330 Spring 340, 350 Second holding body 360, 370, 390 slide cam 365, 375, 395 fulcrum

Claims (9)

A fixing member having a fixing member that heats and fixes a toner image on the recording paper, and a pressure roller that presses the recording paper between the fixing member; and
An external heating roller for heating the fixing member from the outside;
A first swinging unit that swings the fixing unit in a sheet width direction orthogonal to the conveyance direction of the recording sheet;
A second swinging portion that swings the external heating roller in the paper width direction;
A control unit that controls the first swinging unit and the second swinging unit such that a relative position between the fixing unit and the external heating roller in the sheet width direction changes;
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the control unit controls the second swinging unit to swing the external heating roller based on a position of the fixing unit in the sheet width direction.   The image forming apparatus according to claim 1, wherein the control unit controls the first swinging unit to swing the fixing unit based on a position of the external heating roller in the sheet width direction.   The image forming apparatus according to claim 1, wherein the control unit controls the first oscillating unit and the second oscillating unit to oscillate the fixing unit and the external heating roller in directions opposite to each other.   The image forming apparatus according to claim 1, wherein the control unit controls the second swinging unit so as not to swing the external heating roller.   The image forming apparatus according to claim 1, wherein the control unit controls the first swing unit so as not to swing the fixing unit. A contact / separation part for bringing the external heating roller into contact with the fixing member or separating the external heating roller from the fixing member;
2. The control unit according to claim 1, wherein when the control unit controls the second swinging unit to swing the external heating roller, the control unit controls the contact separation unit to separate the external heating roller from the fixing member. Image forming apparatus.   2. The control unit according to claim 1, wherein the control unit controls the first swing unit and the second swing unit such that the number of swings of the external heating roller is less than the number of swings of the fixing unit. Image forming apparatus.   2. The control unit according to claim 1, wherein the control unit controls the first swing unit and the second swing unit such that a swing range of the external heating roller is wider than a swing range of the fixing unit. Image forming apparatus.

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