JP2015169678A - image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the increase of the size of a heater 60 for heating a fixing belt, while suppressing useless energy consumption caused by the application of heat to an area which does not come into contact with a recording sheet in the fixing belt.SOLUTION: In the heater 60 including a heat generation unit 62 including a plurality of heat generation areas arranged side by side in a substrate short side direction being a direction orthogonal to a surface movement direction along the surface of the fixing belt and generating the heat independently from each other and a heater substrate 61 holding the heat generation unit 62, a fixation power source not shown in the figure is connected in parallel to two heat generation areas in pairs of heat generation areas (62a and 62g, 62b and 62f, and 62c and 62e) comprising two heat generation areas being at line-symmetric positions with each other with respect to a center line L1 in a substrate long side direction and paired with each other.

Description

  The present invention relates to a fixing member having a fixing member heated for image fixing processing, an abutting member that contacts a surface of the fixing member to form a fixing nip, and a heating unit that heats the fixing member. . The present invention also relates to an image forming apparatus such as a copying machine, a facsimile machine, and a printer using such a fixing device.

  Conventionally, as this type of image forming apparatus, the one described in Patent Document 1 is known. FIG. 12 is a schematic configuration diagram illustrating a fixing device 300 mounted on the image forming apparatus disclosed in Patent Document 1. The fixing device 300 includes an endless fixing film 301, a driving roller 302, a driven roller 303, a heater holder 304, a heater 305, a pressure roller 302, and the like. The fixing film 301 wound around the driving roller 302, the driven roller 303, and the heater holder 304 moves endlessly in the clockwise direction in the drawing as the driving roller 302 rotates. A pressure roller 302 as a contact body disposed outside the loop of the fixing film 301 as a fixing member, and a heater 305 held by a heater holder 304 disposed in the hollow of the fixing film 301 are: A fixing film 301 is sandwiched between them. Thus, a fixing nip is formed by the contact between the front surface of the fixing film 301 and the pressure roller 302 as a contact body. A recording sheet P carrying an unfixed toner image Tp is fed into the fixing nip. The heater 305 functions as a sandwiching body that sandwiches the fixing film 301 between the pressure roller 302 and also functions as a heating unit that heats the fixing film 301. Then, the toner image Tp on the recording sheet P in the fixing nip is heated through the fixing film 301. The toner image Tp pressurized and heated in the fixing nip is fixed on the surface of the recording sheet P.

  On the other hand, the present inventors are developing an image forming apparatus in which the heater 600 shown in FIG. The heater 600 in the figure heats the fixing film while being in contact with the inner surface of the fixing film, similarly to the heater (305 in FIG. 12) mounted on the fixing device of the image forming apparatus of Patent Document 1. The heater 600 includes a rectangular heater substrate 610, an energizing heat generating unit 620 as a heat generating body including six heat generating regions (621 to 627), a plurality of electrode pads Ep, and the like. The energization heat generation unit 620 includes a first heat generation area 621, a second heat generation area 622, a third heat generation area 623, a fourth heat generation area 624, a fifth heat generation area 625, a sixth heat generation area 626, and a seventh heat generation area 627. doing. These seven heat generating regions are arranged at different positions in the movement orthogonal direction (left and right direction in the figure) which is a direction orthogonal to the surface movement direction on the surface of the fixing film (not shown). The first heat generation region 621 and the seventh heat generation region 627 are disposed at positions symmetrical with respect to each other with respect to the center line L1 in the movement orthogonal direction of the heater substrate 610 to form a heat generation region pair. The fixing power source 630 is connected in series via the first switch 635. Further, the second heat generation area 622 and the sixth heat generation area 626 are arranged at symmetrical positions with respect to the center line L1 to form a heat generation area pair, and the second switch with respect to the fixing power source 630 is provided. 634 are connected in series with each other. The third heat generation area 623 and the fifth heat generation area 625 are disposed at positions symmetrical to each other with respect to the center line L1 to form a heat generation area pair. 633 are connected to each other in series. The fourth heat generation region 634 is disposed at the center in the movement orthogonal direction and is connected to the fixing power source 630 alone via the fourth switch 632.

  In the image forming apparatus under development, the energizing heat generating unit 620 is provided with a plurality of heat generating regions for the purpose of energy saving. Specifically, in general, the image forming apparatus can use recording sheets of various sizes. With respect to the fixing film of the fixing device, it is only necessary to heat the area that is in close contact with the recording sheet in the fixing nip. If the area that is not in close contact is unnecessarily heated, useless energy is consumed. Therefore, a plurality of heat generating regions (621 to 627) are provided so that only the region to be in close contact with the recording sheet can be heated intensively.

  In addition, in the image forming apparatus under development, a plurality of heat generating area pairs each including two heat generating areas arranged in line-symmetric positions with respect to the center line L1 are provided. This is because the image is formed by the center reference method. Specifically, as a method for determining the reference position of an image, there are a side reference method and a center reference method. The side reference method is a method of forming an image with reference to one end position in the width direction of the sheet conveyance path regardless of the size of the recording sheet to be used. The center reference method is a method for forming an image based on the center position in the width direction of the sheet conveyance path in the image forming apparatus regardless of the size of the recording sheet used. In the center reference method, all usable recording sheets are conveyed in accordance with the center position in the width direction of the sheet conveying path (= the above-mentioned movement orthogonal direction). Regions that do not come into contact with the sheet are generated on both ends in the width direction (= the direction perpendicular to the movement). For this reason, a pair of heat generating regions consisting of two heat generating regions on both sides at positions symmetrical to each other with respect to the center line L1 is provided, and these two heat generating regions are connected in series to the fixing power source 630 so that electric power is supplied. The supply is turned on and off at the same time.

  In such a configuration, wasteful energy consumption is achieved by cutting off the power supply to a plurality of heat generating area pairs that do not correspond to the recording sheet entering the fixing nip or reducing the amount of power supply than usual. Can be reduced.

  However, in the image forming apparatus under development, as shown in FIG. 13, a pair of heat generating regions in which two heat generating regions are connected in series, or a fourth heat generating region 624 disposed independently in the center in the width direction, The fixing film surfaces are arranged so as to be shifted from each other in the direction of movement of the fixing film (the direction of the arrow in the figure). With this arrangement, the heater substrate 610 needs to have a relatively large size in the moving direction of the fixing film, so that there is a problem that the heater 600 is enlarged.

  The present invention has been made in view of the above background, and an object thereof is to provide the following fixing device and image forming apparatus. That is, a fixing device or the like that can suppress wasteful energy consumption caused by heating a region of the fixing member such as a fixing film that does not come into contact with the recording sheet, and can suppress an increase in the size of the heating unit.

  In order to achieve the above object, the present invention provides a fixing member that is heated for image fixing processing, a contact member that contacts the surface of the fixing member to form a fixing nip, and heats the fixing member. A fixing device that heats the recording sheet that has entered the fixing nip to fix the image on the recording sheet. A heating element comprising a plurality of heat generating regions that generate heat independently from each other along the surface in a direction perpendicular to the surface moving direction along the surface, and a plurality of heat generating regions for supplying power, respectively. A plurality of connected individual electrodes, and a heating body and a holding body that holds the plurality of individual electrodes are provided in the heating unit, and are connected to each other on the basis of the center position of the holding body in the movement orthogonal direction. In the position of the universal respect the two heating regions in said two consists heat generating region heating regions pair paired together, is characterized in that it has connecting said fixing power in parallel.

  According to the present invention, there is an excellent effect that it is possible to suppress an increase in the size of the heating unit while suppressing wasteful energy consumption by heating a region of the fixing member such as a fixing film that does not contact the recording sheet.

1 is a schematic configuration diagram illustrating a printer according to an embodiment. FIG. 2 is an internal configuration diagram illustrating an internal configuration of a fixing device of the printer. The top view which shows the heater of the fixing device from the front surface side. The partial top view which shows partially the both ends in the board | substrate longitudinal direction of the same heater. FIG. 2 is a block diagram showing a part of an electric circuit in the printer. FIG. 6 is a schematic diagram for explaining the relationship between the size of a recording sheet, the power supply to each heat generation area of the heat generating unit of the identification fixing device, and the fixing temperature. The top view which shows the heater of the printer which concerns on a 1st modification. The top view which shows the heater of the printer which concerns on a 2nd modification. The internal block diagram which shows the internal structure of the fixing device of the printer which concerns on a 3rd modification. 6 is a graph showing an example of the relationship between the fixing temperature and the position of the fixing belt in the longitudinal direction of the substrate. 6 is a graph showing the relationship between the fixing temperature and the position of the fixing belt in the longitudinal direction of the substrate in the printer. 1 is a schematic configuration diagram illustrating a fixing device mounted on an image forming apparatus disclosed in Patent Document 1. FIG. FIG. 3 is a schematic plan view showing a heater 600 mounted on a fixing device of an image forming apparatus under development together with an electric circuit.

  Hereinafter, an embodiment of a printer that forms an image by an electrophotographic method will be described as an image forming apparatus to which the present invention is applied. The printer according to the embodiment described below is merely an example of an image forming apparatus to which the present invention is applied, and the embodiment of the present invention is not limited to the correspondence of the printer according to the embodiment.

First, a basic configuration of the printer according to the embodiment will be described.
FIG. 1 is a schematic configuration diagram illustrating a printer according to an embodiment. The printer according to the embodiment includes a drum-shaped photoreceptor 1 serving as a latent image carrier, a charger unit 2 of a charging device, a surface potential sensor 3, a developing device 4, a transfer device 5, a static elimination cleaning device 6, a registration roller pair 21, a light A writing device 8 is provided. Further, a paper feed cassette 20, a transport belt unit 24, a fixing device 31, a paper discharge path 32, a paper discharge roller pair 33, a paper discharge tray 34, and the like are also provided.

  The drum-shaped photoreceptor 1 has an organic photosensitive layer on the surface of a drum base, and is rotationally driven in a clockwise direction in the drawing by a driving unit (not shown). Around the photosensitive member 1, a charging device 2, a surface potential sensor 3, a developing device 4, a transfer roller 27, a static elimination cleaning device 6 and the like are disposed.

  The charging device 2 is disposed so as to face the photoconductor 1 with a predetermined gap therebetween, and uniformly charges the surface of the photoconductor 1 that is rotationally driven. In the present printer, the charging device 2 is one that charges the photosensitive member 1 by the scorotron method.

  The surface of the photoconductor 1 uniformly charged by the charging device 2 is optically scanned by the writing light L emitted from the optical writing device 8. Of the entire area of the photoreceptor 1, the area irradiated with the writing light L by optical scanning carries an electrostatic latent image by attenuating the potential.

A surface potential sensor 3 serving as a surface potential detecting means for detecting the surface potential of the photoreceptor 1 by a known technique sequentially sets a position facing the charging device 2 and an optical scanning position in the entire area of the peripheral surface of the photoreceptor 1. The surface potential of the area after passing is detected. By charging the surface of the photosensitive member 1 by the charging device 2 in a state of not performing optical scanning by the optical writing device 8, it is possible to detect the charge potential V _D of the background portion of the photosensitive member 1 to the surface potential sensor 3 .

  The surface of the photoconductor 1 that has passed through the position facing the surface potential sensor 3 in accordance with the rotational drive enters the position facing the developing device 4. The developing device 4 includes a well-known one-component developing device or two-component developing device, and electrostatically adheres the toner to the electrostatic latent image on the photoconductor 1 in the area where the photoconductor 1 faces itself. The latent image is developed to obtain a toner image. The toner image developed in this manner enters a transfer nip formed by contact between the photosensitive member 1 and a conveyance belt 25 described later as the photosensitive member 1 rotates.

  A conveyor belt unit 24 having an endless conveyor belt 25, a driven roller 26, a transfer roller 27, a driving roller 28, and the like is disposed below the photoreceptor 1. The conveyor belt unit 24 moves the conveyor belt 25 stretched by the driven roller 26 and the driving roller 28 endlessly in the counterclockwise direction in the drawing by the rotational driving of the driving roller 28. A transfer roller 27 to which a transfer bias is applied by a transfer bias power source (not shown) is disposed in a loop of the conveyance belt 25 made of a rubber belt. The conveyance belt unit 24 forms a transfer nip by bringing a stretched portion between the driven roller 26 and the transfer roller 27 out of the entire area of the conveyance belt 25 in the circumferential direction into contact with the photosensitive member 1.

  A paper cassette 20 is mounted on the printer body. The paper feed cassette 20 stores a plurality of recording sheets P such as recording sheets in a bundle of sheets. A sheet feeding roller 20 a is in contact with the top recording sheet P in the sheet bundle accommodated in the sheet feeding cassette 20. The paper feed roller 20a is driven to rotate at a predetermined timing to send out the recording sheet P from the paper feed cassette 20 toward the paper feed path.

  Near the end of the paper feed path, there is a registration roller pair 21 that rotates a pair of registration rollers in contact with each other. When the recording sheet P hits its registration nip, the registration roller pair 21 temporarily stops the rotation of the registration roller. Then, the rotation of the registration roller is resumed at the timing when the recording sheet P is superimposed on the toner image on the photosensitive member 1 by the transfer unit, and the recording sheet P is sent out toward the transfer nip.

  The recording sheet P sent out from the registration roller pair 21 enters the transfer nip while entering between the pre-nip upper guide plate 22 and the pre-nip lower guide plate 23 and being guided toward the transfer nip. In the transfer nip, a transfer electric field is formed between the recording sheet P sent to the transfer nip and the electrostatic latent image on the photosensitive member 1 to electrostatically move the toner from the photosensitive member 1 side to the recording sheet P side. The A toner image on the photoreceptor 1 is transferred to the surface of the recording sheet P that has been fed into the transfer nip by the action of a transfer electric field.

  The recording sheet P that has passed through the transfer nip sequentially passes over the nip outlet guide plate 29 and the pre-fixing guide plate 30 and then enters the fixing device 50. The fixing device 50 fixes the toner image on the recording sheet P by sandwiching the sent recording sheet P in a fixing nip, which will be described later, and applying heat and pressure.

  The surface of the photoreceptor 1 that has passed through the transfer nip enters a position facing the neutralization cleaning device 6. The neutralization cleaning device 6 includes a neutralization lamp (not shown) and a cleaning member (not shown). The transfer residual toner adhering to the surface of the photoconductor 1 is scraped off from the surface of the photoconductor 1 by a cleaning blade or a cleaning brush roller that is driven to rotate. The surface of the photoconductor 1 is neutralized by irradiating the surface of the photoconductor 1 with a charge eliminating light from a charge eliminating lamp. The surface of the photoreceptor 1 from which the charge has been removed is uniformly charged again by the charging device 2 to prepare for the next latent image formation.

  The recording sheet P that has passed through the fixing device 50 is discharged out of the apparatus via the paper discharge path 32 and the paper discharge nip of the paper discharge roller pair 33. Then, they are stacked on a paper discharge tray 34 provided outside the apparatus.

  FIG. 2 is an internal configuration diagram illustrating an internal configuration of the fixing device 50. The fixing device 50 includes an endless fixing belt 51, a support member 52, a sandwiching body 53, a pressure roller 54, a heating support roller 55, a first thermistor 56, a second thermistor 57, a heater 60, and the like.

  A fixing belt 51 as a fixing member includes an endless belt-like belt base 51a, an elastic layer 51b laminated on the front surface (loop outer surface), and release promotion laminated on the front surface. Layer 51c. The belt base 51a made of a heat-resistant material such as polyimide has an outer diameter (diameter) of about 40 [mm] and a thickness of about 50 to 100 [μm]. A metal material such as nickel or stainless steel may be used as the material of the belt base 51a. The thickness of the elastic layer 51b made of an elastic material such as silicon rubber is about 50 to 150 [μm] so that the belt as a whole exhibits elasticity in the thickness direction. Further, the thickness of the mold release promoting layer 51c made of a fluorine-based resin such as PFA or PTFE is about 5 to 50 [μm] in order to exhibit good toner release properties on the belt front surface.

  A cylindrical support member 52 disposed in the hollow of the fixing belt 51 is for keeping the shape of the fixing belt 51 in a cylindrical shape while supporting the deformable fixing belt 51 from the inside.

  The pressure roller 54 disposed outside the loop of the fixing belt 51 is urged toward the fixing belt 51 through a slidable bearing by a spring (not shown) while being rotatably supported by a bearing (not shown). Has been. The sandwiching body 53 disposed inside the loop of the fixing belt 51 sandwiches the fixing belt 51 with the pressure roller 54 biased toward the fixing belt 51. As a result, a fixing nip is formed by the contact between the front surface of the fixing belt 51 and the pressure roller 54.

  On the peripheral surface of the cored bar 54a of the pressure roller 54, an elastic layer 54b is coated to improve the adhesion with the fixing belt 51 in the fixing nip. In the iron cored bar 54a, the outer diameter is about 40 [mm] and the thickness is about 2 [mm]. The thickness of the elastic layer 54b made of an elastic material such as silicon rubber is 5 [mm]. A release promoting layer made of a fluororesin or the like for improving the releasability with the toner may be coated on the front surface of the elastic layer 54b with a thickness of about 40 [μm].

  Of the entire region of the back surface (loop inner surface) of the fixing belt 51 in the circumferential direction, the region near the contact position with the sandwiching body 53 and upstream of the contact position in the belt moving direction is located inside the belt loop. The heater 60 arranged in the contact is in contact. The heater 60 heats the fixing belt 51 from the inside by bringing the heating element (not shown) into contact with the inner surface of the fixing belt 51 while generating heat.

  The heating support roller 55 disposed outside the loop of the fixing belt 51 is urged toward the heater 60 via a slidable bearing by a spring (not shown) while being rotatably supported by a bearing (not shown). ing. The fixing belt 51 is sandwiched between the fixing belt 51 and the heater 60 disposed inside the loop of the fixing belt 51, thereby improving the adhesion between the heater 60 and the fixing belt 51.

  An elastic layer 54 b is coated on the peripheral surface of the core bar 55 a of the heat support roller 55. On the front surface of the elastic layer 55b, a release promoting layer made of a fluororesin or the like for improving the releasability with the toner may be coated with a thickness of about 40 [μm].

  Above the fixing belt 51, a first thermistor 56 as temperature detecting means is disposed so as to face the belt front surface with a predetermined gap. Then, the temperature of the region immediately before entering the contact position with the heater 60 is detected from the front surface side of the entire region in the circumferential direction of the fixing belt 51, and a signal of the detection result is sent to a control unit (not shown). .

  A second thermistor 57 is disposed inside the loop of the fixing belt 51 and detects the temperature of the heater 60 from the back side of the heater 60. And the signal of the detection result is sent to a control part. The control unit calculates the required power based on the belt temperature grasped based on the signal from the first thermistor 56 and the heater temperature grasped based on the signal from the second thermistor 57. The necessary power is the power supplied to the heating element of the heater 60 that is required to raise the temperature to the target temperature when the region immediately before entering the contact position with the heater 60 in the fixing belt 51 is entered into the contact position. It is. The controller that has calculated the required power sends a control signal to a fixing power source (not shown) to output a current capable of obtaining the required power from the fixing power source by constant current control. As a result, the temperature of the fixing belt 51 immediately after passing through the contact position with the heater 60 becomes the target temperature.

  When the recording sheet P carrying the toner image Tp enters the fixing nip together with the area immediately after being heated by the heater 60 in the fixing belt 51, the recording sheet P is pressed while being heated by the fixing belt 51. By this heating and pressurization, the toner image Tp is fixed on the surface of the recording sheet P.

  As described above, by using a belt-like member or a film-like member as the fixing member, the warm-up time can be shortened and the first print time can be further shortened as compared with a configuration using a roller-like member. The first print time is a time required from when an image formation command is received by the user to when a print job is performed through an image formation preparation operation and the first recording sheet on which the image is formed is discharged from the image forming apparatus. In order to shorten the first print time, it is necessary to shorten the warm-up time. The warm-up time is a time required to raise the temperature of the fixing member to a desired temperature by supplying electric power to a heating means such as a heater when the power is turned on or when returning from the standby state. In a configuration in which a roller-shaped member having a large thickness is used as the fixing member, since the heat capacity of the roller-shaped fixing member is relatively large, a relatively long time is required for the warm-up time. On the other hand, in a configuration using a thin fixing member such as a belt shape or a film shape, a thin fixing member having a relatively small heat capacity is heated to a desired temperature by heating in a short time. For this reason, the warm-up time can be shortened as compared with a configuration using a roller-shaped fixing member.

Next, a characteristic configuration of the printer will be described.
FIG. 3 is a plan view showing the heater 60 from the front surface (contact surface with the fixing belt 51) side. In the figure, the longitudinal direction of the heater 60 is along a movement orthogonal direction which is a direction orthogonal to the surface movement direction on the surface of the fixing belt (51). The short direction of the heater 60 is along the surface movement direction.

  The heater 60 includes a heater substrate 61 as a holding body, a heat generating unit 62 as a heating element, a common electrode 63, seven individual electrodes, and the like. The material of the heater substrate 61 having the heat generating unit 62 laminated on the surface may be ceramic such as alumina or aluminum nitride, but ceramic or glass having low thermal conductivity such as cordierite is desirable. By doing so, the heat of the heat generating unit 62 sandwiched between the heater substrate 61 and the fixing belt 51 is preferentially conducted to the fixing belt 61 rather than the heater substrate 61, so that high-efficiency heating with quick response is performed. It is possible to do it.

  The heat generating unit 62 made of a resistance heating element includes a plurality of heat generating regions that generate heat independently from each other while being in contact with different positions of the fixing belt (519 in the direction orthogonal to the movement). A first heat generation area 62a, a second heat generation area 62b, a third heat generation area 62c, a fourth heat generation area 62d, a fifth heat generation area 62e, a sixth heat generation area 62f, and a seventh heat generation that are arranged side by side and generate heat independently of each other. The first heat generation area 62a and the seventh heat generation area 62g are symmetrical with respect to the center line L1 in the movement orthogonal direction (substrate longitudinal direction) of the heater substrate 61. Further, the second heat generation region 62b and the sixth heat generation region 62f are also provided in a line symmetrical position with respect to the center line L1 to generate heat. In addition, the third heat generation region 62c and the fifth heat generation region 62e are also provided at symmetrical positions with respect to the center line L1 to form a heat generation region pair. The plurality of heat generating area pairs are formed on the heater substrate 61 because the printer forms an image by the center reference method.

  In the printer, only the fourth heat generation region 62d formed at the center position in the movement orthogonal direction (substrate longitudinal direction) among the seven heat generation regions does not form a heat generation region pair.

  In the vicinity of the heat generating unit 62, a common electrode 63 extending over almost the entire area of the heater substrate 61 in the longitudinal direction of the substrate is formed so as to be aligned with the heat generating unit 62 in the short direction of the substrate. As shown, the common electrode 63 includes a first heat generation area 62a, a second heat generation area 62b, a third heat generation area 62c, a fourth heat generation area 62d, a fifth heat generation area 62e, a sixth heat generation area 62f, and a seventh heat generation area. Each is connected to the region 62g.

  In the heater substrate 61, a first individual electrode 64a, a second individual electrode 64b, and a third individual electrode 64c are formed in a region on one end side (left side in the drawing) of the substrate longitudinal direction from the center line L1. The first individual electrode 64 a is connected to only the first heat generation area 62 a among the seven heat generation areas in the heat generation unit 62. The second individual electrode 64 b is connected to only the second heat generation area 62 b among the seven heat generation areas in the heat generation unit 62. Further, the third individual electrode 64 c is connected to only the third heat generation region 62 c among the seven heat generation regions in the heat generation unit 62.

  On the other hand, in the heater substrate 61, the fourth individual electrode 64d, the fifth individual electrode 64e, the sixth individual electrode 64f, and the seventh individual electrode are disposed in the region on the other end side (right side in the drawing) of the substrate longitudinal direction from the center line L1. Individual electrodes 64g are formed. The fourth individual electrode 64d is connected to only the fourth heat generation region 62d among the seven heat generation regions in the heat generation unit 62. Further, the fifth individual electrode 64 e is connected to only the fifth heat generation region 62 e among the seven heat generation regions in the heat generation unit 62. The sixth individual electrode 64f is connected to only the sixth heat generation region 62f among the seven heat generation regions in the heat generation unit 62. The seventh individual electrode 64g is connected to only the seventh heat generation region 62g among the seven heat generation regions in the heat generation unit 62.

  FIG. 4 is a partial plan view partially showing both end portions of the heater 60 in the longitudinal direction of the substrate. The first individual electrode 64a is connected to the first heat generation region 62a in the heat generation region pair including the first heat generation region 62a and the seventh heat generation region 62g. The seventh individual electrode 64g is connected to the seventh heat generation region 62g in the heat generation region pair. Of the first individual electrode 64a and the seventh individual electrode 64g, the first individual electrode 64a is disposed in a region on one end side (left side in the figure) in the longitudinal direction (movement orthogonal direction) of the heater substrate 61. Yes. The seventh individual electrode 64g is disposed in a region on the other end side (right side in the drawing) in the longitudinal direction of the heater substrate 61 and on a virtual extension line L2 in the substrate longitudinal direction of the first individual electrode 64a. Has been. With such an arrangement, the two first individual electrodes 64a and the seventh individual electrode 64g are accommodated in a space corresponding to one individual electrode in the lateral direction of the substrate (surface movement direction).

  The second individual electrode 64b is connected to the second heat generation region 62b in the heat generation region pair including the second heat generation region 62b and the sixth heat generation region 62f. The sixth individual electrode 64f is connected to the sixth heat generation region 62f in the heat generation region pair. Of the second individual electrode 64b and the sixth individual electrode 64f, the second individual electrode 64b is arranged in a region on one end side (left side in the drawing) in the longitudinal direction of the heater substrate 61. The sixth individual electrode 64f is disposed in a region on the other end side (right side in the drawing) in the longitudinal direction of the heater substrate 61 and in a region on the virtual extension line L3 in the substrate longitudinal direction of the second individual electrode 64b. Has been. With such an arrangement, the two second individual electrodes 64b and the sixth individual electrode 64f are accommodated in a space corresponding to one individual electrode in the lateral direction of the substrate.

  The third individual electrode 64c is connected to the third heat generation region 62c in the heat generation region pair including the third heat generation region 62c and the fifth heat generation region 62e. The fifth individual electrode 64e is connected to the fifth heat generating region 62e in the heat generating region pair. Of the third individual electrode 64c and the fifth individual electrode 64e, the third individual electrode 64c is arranged in a region on one end side (left side in the drawing) in the longitudinal direction of the heater substrate 61. The fifth individual electrode 64e is disposed in a region on the other end side (right side in the drawing) in the longitudinal direction of the heater substrate 61 and on a virtual extension line L4 in the substrate longitudinal direction of the third individual electrode 64c. Has been. With such an arrangement, the two third individual electrodes 64c and the fifth individual electrode 64e are accommodated in a space corresponding to one individual electrode in the lateral direction of the substrate.

  Thus, the three individual electrode pairs respectively corresponding to the three heat generating region pairs are all accommodated in a space corresponding to one individual electrode in the short direction of the substrate. In this way, by placing the two individual electrodes in the heat generating region pair in one space in the short side direction of the substrate, the heater substrate 61 can be compared with the case where one space is secured for each individual electrode. Suppresses the increase in size in the short direction of the substrate.

  In the above configuration, the power supply to a pair of heat generation areas provided in the heat generation unit 62 that does not correspond to the size of the recording sheet P entering the fixing nip is interrupted, or the power supply amount is set to be higher than usual. It can be reduced. Thereby, useless energy consumption due to unnecessarily heating the area of the fixing belt 51 that does not contact the recording sheet P can be suppressed.

  Further, unlike the image forming apparatus under development shown in FIG. 13 in which the heater configuration is shown, two heat generation areas forming a pair of heat generation areas are connected in parallel to the fixing power source 70 without being connected in series. There is no need to provide an electrode which is interposed between two heat generating regions and which is connected in series. For this reason, as shown in the figure, since it is possible to arrange all the heat generating regions in a straight line, unlike the image forming apparatus under development in which they are arranged to be shifted from each other, the heater 60 is arranged. Increase in size can be suppressed.

As shown in FIGS. 3 and 4, the plurality of individual electrodes are arranged in the following manner. That is, the position of the heating region (62) to be connected is closer to the end of the heater substrate 61 in the substrate longitudinal direction, and the individual electrode is closer to the substrate in the shorter direction than the individual electrode farther from the end. The heat generating unit 62 is disposed closer. In such an arrangement, as shown in the drawing, the plurality of individual electrodes (64a to 64g) can be arranged without crossing each other.
Although the example in which the heat generating unit 62 is divided into seven heat generating regions in the direction orthogonal to the sheet conveyance direction (substrate longitudinal direction) has been described, the heat generating region pairs at positions symmetrical with respect to each other with respect to the center position in the direction are described. The number of divisions is not limited to seven as long as the arrangement is provided. It should be noted that a heat generation region may or may not be provided at the center position. When the heat generation area is arranged at the center position, the total number of the heat generation areas is set to an odd number, and two sets in the remaining heat generation areas excluding the heat generation area at the center position are each based on the center position in the direction. What is necessary is just to comprise the heat_generation | fever area | region pair in a mutually symmetrical position. The minimum value of the total number of heat generating regions in such a configuration is three. In this case, one heat generating region pair may be configured by the remaining two heat generating regions excluding the heat generating region at the center position. In addition, when the heat generation area is not provided at the center position, the total number of heat generation areas is set to an even number, and two sets in each of the heat generation areas are respectively symmetrical with respect to the center position in the same direction. What is necessary is just to comprise the heat_generation | fever area | region pair in a. For example, a heating mode corresponding to a large-sized recording sheet can be configured by configuring two heat generating area pairs with four heat generating areas and switching the two heat generating area pairs on simultaneously and turning on only one heat generating area pair. And a heating mode corresponding to a small-sized recording sheet can be switched. In any configuration, as in the printer according to the embodiment, the arrangement positions of all the heat generation areas are arranged in a line in a direction orthogonal to the sheet conveyance direction without shifting in the sheet conveyance direction (substrate short direction). Therefore, the heat generating unit 62 can be downsized.

  FIG. 5 is a block diagram showing a part of an electric circuit in the printer. In FIG. 1, a main control unit 100 controls driving of each device in the printer, and includes a CPU (Central Processing Unit), a RAM (Random Access Memory) as data storage means, and a ROM (Read Only) as data storage means. Memory) and non-volatile memory. And based on the program memorize | stored in ROM, the drive of various apparatuses is controlled or a predetermined calculation process is performed.

  The main controller 100 includes an optical writing device 8, a process motor 10, a developing bias power source 11, a transfer bias power source 12, a registration clutch 13, a fixing device 50, a fixing power source 70, a switch unit 71, an optical writing control unit 105, The operation display unit 110 and the like are electrically connected.

  The optical writing control unit 105 optically scans the surface of the photoreceptor 1 by controlling the driving of the optical writing device 8 based on image information sent from the outside. Examples of the optical writing device 8 that performs optical scanning with the writing light L on the photosensitive member 1 include a well-known laser writing optical system and an LED array.

  The process motor 10 is a motor serving as a drive source for the photosensitive member 1, the developing device (4), the fixing device 50, various rollers, and the like. The rotational driving force of the process motor 10 is transmitted to a registration roller pair (21) (not shown) via a registration clutch 13. When the main control unit 100 turns on the registration clutch 13 at an arbitrary timing, the rotational driving force of the process motor 10 is connected to the registration roller pair (21).

The developing device (4) attaches toner carried on the surface of a developing roller (not shown) to the electrostatic latent image on the photoreceptor 1. In order to selectively attach the toner only to the electrostatic latent image in the entire area of the surface of the photoreceptor 1, the developing roller has the same polarity as the toner, and the absolute value thereof is the absolute value of the latent image potential _VL . A developing bias that is larger than the charging potential V _D of the background portion of the photoreceptor 1 is applied. For example, a developing bias of −550 [V] is applied to the developing roller under the condition that the photoreceptor background portion potential = −800 [V] and the electrostatic latent image potential = −30 [V]. The development bias power supply 11 outputs the development bias. The main control unit 100 outputs the development bias from the development bias power supply 11 at an arbitrary timing by sending an output command signal to the development bias power supply 11.

  Further, the main control unit 100 outputs the transfer bias from the transfer bias power supply 12 by sending an output command signal to the transfer bias power supply 12 at an arbitrary timing. The transfer bias is a voltage for forming a transfer electric field between the recording sheet P and the electrostatic latent image on the photoconductor 1 at a transfer portion where the transfer device (5) and the photoconductor 1 face each other.

  In addition, the main control unit 100 performs a process of forming a toner image on the photoconductor 1 based on the center reference in cooperation with the optical writing control unit 105.

  The operation display unit 110 includes a touch panel and a numeric keypad (not shown). The operation display unit 110 displays an image on the touch panel and sends information input by the touch panel, the numeric keypad, and the like to the main control unit 100.

  The fixing power source 70 outputs power supplied to the heat generating unit (62) of the fixing device 50 by constant current control. The current output from the fixing power source 70 is sent to the individual electrodes (64a to 64g) of the fixing device 50 via the switch unit 71 to reach the heat generating regions (62a to g) of the heat generating unit. The switch unit 71 includes a first switch circuit, a second switch circuit, a third switch circuit, and a fourth switch circuit (not shown). Then, based on a control signal from the main control unit 100, these four switches are individually turned on and off.

  The first switch of the switch unit 71 is a switch for turning on and off the current from the fixing power source 70 with respect to the first individual electrode 64a and the seventh individual electrode 64g. When the first switch is turned on, the current from the fixing power source 70 flows to the first heat generating area 62a via the first individual electrode 64a and flows to the seventh heat generating area 62g via the seventh individual electrode 64g.

  The second switch of the switch unit 71 is a switch for turning on and off the current from the fixing power source 70 with respect to the second individual electrode 64b and the sixth individual electrode 64f. When the second switch is turned on, a current from the fixing power source 70 flows to the second heat generation area 62b via the second individual electrode 64b and flows to the sixth heat generation area 62f via the sixth individual electrode 64f.

  The third switch of the switch unit 71 is a switch for turning on and off the current from the fixing power source 70 with respect to the third individual electrode 64c and the fifth individual electrode 64e. When the third switch is turned on, the current from the fixing power source 70 flows to the third heat generating area 62c via the third individual electrode 64c and flows to the fifth heat generating area 62e via the fifth individual electrode 64e.

  The fourth switch of the switch unit 71 is a switch for turning on and off the current from the fixing power source 70 with respect to the fourth individual electrode 64d. When the third switch is turned on, a current from the fixing power source 70 flows to the fourth heat generating region 62d through the fourth individual electrode 64d.

  FIG. 6 is a schematic diagram for explaining the relationship between the size of the recording sheet P, the power supply to each heat generating area of the heat generating unit 62, and the fixing temperature. The recording sheet P shown in the figure is the third largest among the usable recording sheets P. When the recording sheet P enters the fixing nip, the regions that come into contact with the fixing belt (51) in the longitudinal direction of the substrate are the third heat generating region 62c, the fourth heat generating region 62d, and the fifth heat generating region 62e in the heat generating unit 62. The corresponding area. For this reason, basically, it is not necessary to generate heat in other heat generation regions. However, the power supply to the first heat generation area 62a, the second heat generation area 62b, the sixth heat generation area 62f, and the seventh heat generation area 62g not corresponding to the recording sheet P is cut off, and the temperature of the fixing belt area corresponding to these heat generation areas If the value is extremely reduced, there is a risk of causing problems. Specifically, if the next print job is larger than the recording sheet P shown in the figure and is started immediately after the current print job is finished, the above four fixing belt regions can be quickly reached the target temperature. The temperature cannot be raised, and a fixing failure is caused in the fixing belt region.

  Therefore, the main control unit 100 applies power to the heat generation area pair that does not correspond to the size of the recording sheet P conveyed to the fixing nip and that has a power supply amount larger than zero and corresponds to the size. The process of adjusting to a value smaller than the supply amount of is performed. In the example shown in the figure, the heat generation area pair formed of the first heat generation area 62a and the seventh heat generation area 62g and the heat generation area pair formed of the second heat generation area 62b and the sixth heat generation area 62f do not correspond to the size of the recording sheet P. A pair of heat generating areas. The current supply amount to these heat generation region pairs is larger than zero and smaller than the current supply amount to the heat generation region pair composed of the third heat generation region 62c and the fifth heat generation region 62e and the fourth heat generation region 62d. Thus, by avoiding an excessive temperature decrease in the fixing belt region that does not correspond to the size of the recording sheet P, it is possible to avoid the occurrence of the fixing failure described above.

  In the figure, the fixing temperature of the fixing belt region that does not correspond to the size of the recording sheet P and the fixing temperature of the corresponding fixing belt region are substantially the same value. Not because it is. In the latter fixing belt region, a lot of toner enters and takes heat away, whereas in the former fixing belt region, no toner enters at all. It is the same value.

  In FIG. 3, the example in which the individual electrodes (64a to 64g) are connected to only a partial region in the longitudinal direction of the substrate for each of the plurality of heat generating regions (62a to 62g) has been described. As shown in FIG. You may connect an individual electrode to the whole area of a longitudinal direction. Further, although an example in which a gap is provided between adjacent heat generation regions has been described, as shown in FIG. 8, each of the heat generation regions (62a to 62g) is caused to generate heat individually without providing a gap. May be. Specifically, in this example, the common electrode 63 and the individual electrodes (64a to 64g) are also wound inside the heat generating unit 62. In the heat generating unit 62, the common electrode 63 and any one of the seven individual electrodes (62a to 62g) are alternately arranged in the longitudinal direction of the substrate. The common electrode 63 is always located at the boundary position between the heat generating regions adjacent to each other. Taking the second heat generating region 62b as an example of the plurality of heat generating regions, the current applied to the second individual electrode 64b flows toward the common electrode 63 on both sides of the substrate longitudinal direction inside the heat generating unit 62. . And when it reaches the common electrode 63, it flows along the common electrode 63 having a very small electric resistance, and does not flow into an adjacent heat generation region having a larger electric resistance. For this reason, the current supplied to the second heat generating region 62b does not flow into the adjacent first heat generating region 62a or the third heat generating region 62c. As a result, only the second heat generating region 62bd can be selectively heated.

  Further, in the embodiment, the example in which the heater 60 heats the region different from the fixing nip in the entire region in the circumferential direction of the fixing belt 51 has been described. However, as illustrated in FIG. 9, the region of the fixing nip is heated. You may make it do. In this case, the pressure roller 54 is caused to function as a heating support roller, and an additional heating support roller is not required. Moreover, the heater 60 is made to function as a sandwiching body, and a dedicated sandwiching body is not required. Thereby, cost reduction can be achieved.

  Next, a printer according to an example in which a more characteristic configuration is added to the printer according to the embodiment will be described. Unless otherwise described below, the configuration of the printer according to the example is the same as that of the embodiment.

In FIG. 6, the example in which the fixing temperature in the fixing belt region not corresponding to the size of the recording sheet P is substantially the same as the fixing temperature in the fixing belt region corresponding to the size of the recording sheet P has been described. Is not limited. Depending on the amount of toner entering the fixing belt area corresponding to the size of the recording sheet P, the temperature of the fixing belt area may become insufficient, and the temperature of the adjacent non-corresponding fixing belt area may be deprived. . Then, as shown in FIG. 10, the fixing temperature becomes lower than the target temperature T ₁ in both ends of the entire fixing belt region A ₁ corresponding to the size of the recording sheet P, thereby causing a fixing failure. Fear comes out.

Therefore, in the printer according to the embodiment, the main control unit 100 performs the following control. That is, among the plurality of heat generating area pairs in the heat generating unit 62, the heat generating area pairs that do not correspond to the size of the recording sheet P conveyed to the fixing nip and are arranged next to the heat generating area pair corresponding to the size. In contrast, the amount of current supplied is different from the usual amount. Specifically, the amount of current supplied is set to the same value as the amount of current supplied to the heat generating area pair corresponding to the size of the recording sheet P. When the recording sheet P shown in FIG. 6 is used, the heat generating area pair that does not correspond to the size of the recording sheet P and is arranged next to the heat generating area pair corresponding to the size is as shown in the figure. It consists of a second heat generation area 62b and a sixth heat generation area f. For this heat generation area pair, the current supply amount is set to the same value as that for the heat generation area pair including the third heat generation area 62c and the fifth heat generation area 62e and the fourth heat generation area 62d. In this way, as shown in FIG. 11, it is possible to suppress the fixing temperature insufficient at both ends regions of the fixing belt area A ₁ corresponding to the size of the recording sheet P.

What has been described above is merely an example, and the present invention has a specific effect for each of the following modes.
[Aspect A]
A fixing member (for example, a fixing belt 51) that is heated for image fixing processing, a contact body (for example, a pressure roller 54) that contacts a surface of the fixing member to form a fixing nip, and the fixing member. Heating means (for example, a heater 60) for heating and a fixing power source (for example, a fixing power source 70) for outputting electric power to be supplied to the heating means, and a recording sheet (for example, a recording sheet P) that has entered the fixing nip. In a fixing device (for example, the fixing device 50) that heats and fixes an image on a recording sheet, a plurality of heaters that generate heat independently of each other along the surface of the fixing member and in the direction perpendicular to the surface moving direction. A heating element (for example, the heating unit 62) having a plurality of heating regions (for example, 62a to 62g) and a plurality of heating regions connected to the plurality of heating regions for supplying power. A plurality of individual electrodes (for example, 64a to 64g) and a holding body (for example, a heater substrate 61) that holds the heating element and the plurality of individual electrodes are provided in the heating means, and the center position of the holding body in the movement orthogonal direction The fixing power source is connected in parallel to the two heat generation regions in the heat generation region pair formed of the two heat generation regions that are in a line-symmetrical position with respect to each other and are paired with each other. is there.

In such a configuration, in the center reference type image forming apparatus, the power supply to the heat generation area provided in the heat generating element that does not correspond to the size of the recording sheet entering the fixing nip is interrupted, or the power supply amount Can be reduced more than usual. As a result, it is possible to suppress wasteful energy consumption due to unnecessary heating of the area of the fixing member that does not contact the recording sheet.
Further, unlike the image forming apparatus under development shown in FIG. 13, the heater structure has two heat generating areas forming a pair of heat generating areas connected in parallel to the fixing power supply instead of being connected in series. It is not necessary to provide an electrode that is interposed between the heat generating regions and connects them in series. For this reason, it becomes possible to arrange another heat generating region pair between the two heat generating regions, and further another heat generating region pair is provided between the two heat generating regions in the other heat generating region pair. It becomes possible to arrange. In this way, it becomes possible to arrange all the heat generating area pairs in a straight line in the direction perpendicular to the movement direction, so that unlike the image forming apparatus under development in which they are arranged to be shifted from each other, heating An increase in the size of the means can be suppressed.

[Aspect B]
The aspect B is the aspect A in which the individual electrode connected to the other heat generation area in the heat generation area pair is connected to the other heat generation area in the movement orthogonal direction of the holding body and the one heat generation area. The individual electrodes are arranged in a region on a virtual extension line in the movement orthogonal direction.

  In such a configuration, since the two individual electrodes constituting the heat generating region pair are positioned on the same line in the movement orthogonal direction, a space corresponding to one in the surface movement direction of the fixing belt (= short direction of the holding body). Fits in. For this reason, compared with the case where one space is secured for each individual electrode, the size of the heating means in the case of adopting the center reference method is suppressed by suppressing the increase in size in the short direction of the holding body. Can be suppressed.

[Aspect C]
The aspect C is the aspect B, in which the individual electrode in which the position of the heat generation region to be connected is closer to the end in the movement orthogonal direction of the holding body than the individual electrode whose position is farther from the end. The heat generating element is disposed closer to the surface moving direction. In such a configuration, as described in the embodiment, a plurality of individual electrodes can be arranged on the holding body without crossing each other.

[Aspect D]
Aspect D uses any one of Aspects A to C having a hollow structure as the fixing member, and between the contact member and the back side of the fixing nip in the hollow of the fixing member. A sandwiching body (for example, the sandwiching body 53) that sandwiches the fixing member is provided. In this configuration, the first printing time can be shortened by using a thin fixing member having a small heat capacity.

[Aspect E]
Aspect E is any one of Aspects A to D, wherein all of the individual electrodes are arranged in a region on one end side of a region holding the heating element in the entire area of the holding member in the surface movement direction. In addition, a common electrode commonly connected to the plurality of heat generating regions for power supply is provided in the region on the other end side. In such a configuration, the common electrode can be disposed on the holding body without intersecting the plurality of individual electrodes.

[Aspect F]
Aspect F includes an image forming unit (for example, an image forming unit including the photosensitive member 1 and devices disposed around it), a fixing unit that fixes the image on the recording sheet, and the fixing unit. A fixing power source (for example, a fixing power source 70) that supplies power to the heating element provided in the unit, and adjusts the amount of power supplied by the fixing power source to the plurality of heating regions of the heating element, or drives the image forming unit In an image forming apparatus including a control unit (for example, the main control unit 100) that controls the image, the fixing unit according to any one of aspects A to E is used as the fixing unit, and an image is formed by a center reference method. The amount of power supplied to each of the plurality of heat generating area pairs is controlled individually according to the size of the recording sheet conveyed to the fixing nip, and controls the driving of the image forming means. To perform a process of adjusting to, it is characterized in that constitutes the control means.

[Aspect G]
In the aspect G, in the aspect F, during the fixing process, among the plurality of heat generating area pairs, the heat generating area pairs that do not correspond to the size of the recording sheet conveyed to the fixing nip are supplied with electric power. The control means is configured to perform a process of adjusting the supply amount to a value larger than zero and smaller than the supply amount of power to the pair of heat generating regions corresponding to the size. . In such a configuration, as described in the embodiment, it is possible to suppress the occurrence of fixing failure by suppressing an excessive temperature drop in the fixing member region that does not correspond to the size of the recording sheet entering the fixing nip.

[Aspect H]
Aspect H corresponds to aspect F or G, and does not correspond to the size of the recording sheet conveyed to the fixing nip among the plurality of heat generating area pairs, and is arranged next to the heat generating area pair corresponding to the size. The control means is configured to perform a process of adjusting the power supply amount to the same value as the power supply amount to the heat generation region pair corresponding to the size for the heat generation region pair provided. It is characterized by this. With such a configuration, as described in the embodiment, it is possible to suppress a shortage of fixing temperature in both end regions of the fixing member region corresponding to the size of the recording sheet entering the fixing nip.

50: fixing device 51: fixing belt (fixing member)
53: sandwiching body 54: pressure roller (contact member)
60: Heater (heating means)
61: Heater substrate (holding body)
62: Heat generation unit (heating element)
62a to g: Heat generation area 63: Common electrode 64a to g: Individual electrode 70: Fixing power source 100: Main control unit (control means)
P: Recording sheet

JP-A-6-95540

Claims (8)

A fixing member that is heated for fixing the image; a contact member that contacts the surface of the fixing member to form a fixing nip; a heating unit that heats the fixing member; A fixing power source that outputs the electric power of, and fixing the image on the recording sheet by heating the recording sheet that has entered the fixing nip,
A heating element including a plurality of heat generating regions that generate heat independently of each other along the surface perpendicular to the surface moving direction while being along the surface of the fixing member, and the plurality of heat generating regions for supplying power A plurality of individual electrodes connected to each other, and a heating body and a holding body that holds the plurality of individual electrodes are provided in the heating means,
The fixing power source is connected to the two heat generation regions in the heat generation region pair composed of the two heat generation regions that are in line symmetry with each other with respect to the center position in the movement orthogonal direction of the holding body. A fixing device characterized by being connected in parallel. The fixing device according to claim 1.
The individual electrode connected to one heat generation region in the heat generation region pair is disposed in a region on one end side in the movement orthogonal direction of the holding body and is connected to the other heat generation region in the heat generation region pair. The individual electrode is disposed in a region on the other end side in the movement orthogonal direction of the holding body and in a region on a virtual extension line in the movement orthogonal direction of the individual electrode connected to the one heat generation region. A fixing device characterized. The fixing device according to claim 2.
The individual electrode in which the position of the heat generating region to be connected is closer to the end in the movement orthogonal direction of the holding body, and the individual electrode in which the position is farther from the end in the surface movement direction. A fixing device, which is disposed closer to a heating element. The fixing device according to any one of claims 1 to 3,
As the fixing member, a member having a hollow structure is used, and a sandwiching body for sandwiching the fixing member between the contact member and the back side of the fixing nip in the hollow of the fixing member is provided. Fixing device to do. The fixing device according to any one of claims 1 to 4,
All the individual electrodes are disposed in a region on one end side of the region holding the heat generating body in the entire region in the surface movement direction of the holding body, and a plurality of the heat generating regions for supplying power And a common electrode connected in common to the other end of the fixing device. An image forming unit that forms an image on a recording sheet; a fixing unit that fixes an image on the recording sheet; a fixing power source that supplies power to a heating element provided in the fixing unit; and a plurality of heating regions of the heating unit An image forming apparatus comprising: a control unit that adjusts the amount of power supplied by the fixing power source and controls the driving of the image forming unit.
While using the fixing device according to any one of claims 1 to 5, as the fixing means,
The drive of the image forming means is controlled so as to form an image by a center reference method, and the amount of power supplied to each of the plurality of heat generating area pairs is individually set according to the size of the recording sheet conveyed to the fixing nip. An image forming apparatus characterized in that the control means is configured to perform a process of adjusting. The image forming apparatus according to claim 6.
During the fixing process, the power supply amount is set to be larger than zero for the heat generating area pair that does not correspond to the size of the recording sheet conveyed to the fixing nip among the plurality of heat generating area pairs. The image forming apparatus according to claim 1, wherein the control unit is configured to perform a process of adjusting a value smaller than a supply amount of power to the heat generating area pair corresponding to the size. The image forming apparatus according to claim 6 or 7,
Of the plurality of heat generating area pairs, the heat generating area pairs that do not correspond to the size of the recording sheet conveyed to the fixing nip and that are arranged next to the heat generating area pairs corresponding to the size. The image forming apparatus, wherein the control unit is configured to perform a process of adjusting a power supply amount to the same value as a power supply amount for the heat generating region pair corresponding to the size.

Images