JP2018072492A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a temperature difference on a surface of a pressure roller.SOLUTION: A fixing device fixes a toner image formed on a recording material, and comprises: a heating body for applying heat to the toner image; a pressure body that sandwiches the recording material with the heating body to apply pressure to the recording material; and cooling means that cools portions of the pressure body with a cooling power according to the heat capacities of the portions.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a fixing device and an image forming apparatus for fixing a toner image transferred onto a recording material in an image forming apparatus using an electrophotographic system or the like.

  Conventionally, in image forming apparatuses such as copying machines, printers, facsimiles, etc., as a heating device for thermally fixing an unfixed toner image formed and carried on the surface of a recording material using a heat-fixable toner to the recording material, Heat roller type heating devices are often used.

  In a heat roller type heating device, a recording material is introduced into a pressure nip portion between a heat roller heated by a heat source such as a halogen heater and maintained at a predetermined temperature and an elastic pressure roller pressed against the heat roller. Nipped and conveyed. As a result, the unfixed toner image on the surface of the recording material is thermally fixed by the heat of the fixing roller.

  Furthermore, a film heating type fixing device has been proposed, and a fixing roller is brought into close contact with a heating body via a fixing film which is a heat resistant film, and is rotated to rotate the fixing film. The recording material is conveyed by the frictional force between the pressure roller and the recording material and the frictional force between the recording material and the fixing film, which are generated as the pressure roller and the fixing film rotate. Then, the developer image is fixed on the recording material as a permanent image by the heat applied through the fixing film and the pressure applied to the nip portion.

  In such a fixing device, as disclosed in Patent Document 1, there is a configuration in which the core of the pressure roller is hollow. When the core of the pressure roller is hollow, the heat capacity is reduced, and the surface temperature of the pressure member is more likely to rise than that of a solid pressure roller. Moreover, since the air layer becomes a heat insulating layer by making the core metal hollow, the temperature of the pressure roller is difficult to decrease.

  By using such a hollow pressure roller, the rise of the temperature of the pressure roller is accelerated, and power consumption can be reduced by increasing the temperature quickly.

  Further, as disclosed in Patent Document 1, the core of the pressure roller is formed into a thin pipe shape in order to shorten the rise time of the fixing device and save power. If the core of the pressure roller is thin, the heat capacity of the pressure roller is reduced. As a result, the amount of heat that the pressure roller takes from the fixing roller when the fixing device is started up can be reduced, and the rise time of the fixing device is shortened.

  Further, since the recording material is conveyed by rotating the pressure roller, a shaft for rotating the pressure roller, a pipe-shaped cored bar, and a bearing portion for fixing the shaft are required. In order to avoid an increase in the size of the main body, it is necessary to reduce the longitudinal width of the pressure roller, and a bearing portion may be provided inside the maximum sheet passing area.

JP 2007-140320 A

  However, in the fixing device having the above-described configuration, when a recording material having a small width is passed, the surface temperature of the pressure roller in the non-sheet passing area rises (non-sheet passing portion temperature rise). In particular, when a recording material having a width smaller than that of the bearing portion is passed, the temperature rises remarkably in the non-sheet passing region and the hollow portion. This is because the heat capacity of the hollow portion of the pressure roller is smaller than the heat capacity of the solid portion of the pressure roller, so that the temperature is likely to rise. That is, a temperature difference occurs between the solid part and the hollow part. When a wide paper is passed with a temperature difference between the solid part and the hollow part, gloss unevenness occurs.

  The present invention has been made in view of such a problem, and an object thereof is to reduce a temperature difference generated in a pressure roller having portions having different heat capacities.

  In order to achieve this object, the fixing device of the present invention sandwiches the recording material between a heating body for applying heat to a toner image formed on the recording material and the heating body, and the recording material A pressure body that applies pressure to the pressure body, and a cooling means that cools the pressure body with a different cooling force corresponding to a heat capacity corresponding to each portion of the pressure body sandwiching the recording material. To do.

  According to the present invention, it is possible to provide a fixing device capable of reducing a temperature difference generated in a pressure roller having portions having different heat capacities.

1 is a cross-sectional view of an image forming apparatus according to an embodiment of the present invention. It is sectional drawing of the image formation part in embodiment of this invention. It is sectional drawing of the pressure roller of embodiment of this invention. It is a block diagram of the conventional edge part cooling part. It is a graph which shows transition of the surface temperature of a pressure roller when the conventional edge part cooling control is performed. It is a block diagram of the edge part cooling part in embodiment of this invention. FIG. 5 is an enlarged view of an end portion of the fixing device when A4R paper is passed in the embodiment of the present invention. It is a flowchart which shows operation | movement of embodiment of this invention. It is a graph which shows transition of the surface temperature of a pressure roller when the edge part cooling control of embodiment of this invention is performed. It is a table | surface which shows the effect in embodiment of this invention. It is a figure which shows the structure of the edge part cooling part in other embodiment of this invention. FIG. 10 is a diagram illustrating a configuration of a fixing device when A4R paper is passed in another embodiment of the present invention. It is a flowchart which shows operation | movement of other embodiment of this invention. It is a table | surface which shows the effect in other embodiment of this invention.

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

<First Embodiment>
(Overall configuration of image forming apparatus)
The overall configuration of the image forming apparatus according to the first embodiment of the present invention will be described in detail.

  FIG. 1 is a diagram illustrating an overall configuration of an image forming apparatus A according to the present embodiment.

  As shown in the figure, the image forming apparatus A includes a scanner unit B, an image forming unit C, and a sheet deck D.

  The scanner unit B reads image information such as a document, converts the read image information into an electric signal, and transmits the electric signal to the image forming unit C.

  The image forming unit C transfers the image information transmitted from the scanner unit B to a recording material such as a sheet conveyed from the sheet deck D as a developer image, and fixes the transferred developer image on the recording material and discharges it. To do. Details of the configuration of the image forming unit C will be described later.

  The sheet deck D includes a feeding unit U1 and a feeding unit U2 each including a pair of sheet cassettes 1a and a sheet cassette 1b. The sheet deck D separates the sheet-like recording materials accommodated in the respective sheet cassettes 1a and 1b one by one and conveys them to the image forming unit C.

  Here, the image forming apparatus A functions as a copying machine if the processing signal of the image processing unit of the scanner unit B is input to the image forming unit C, and the output signal of an external device such as a computer is input to the image forming unit C. Function as a printer. Further, the image forming apparatus A functions as a facsimile apparatus by receiving a signal from an external facsimile apparatus and transmitting a processing signal of the image processing section of the scanner section B to the external facsimile apparatus.

(Configuration of image forming unit)
Next, the configuration of the image forming unit C of the present embodiment will be described.

  FIG. 2 is a diagram illustrating a configuration of the image forming unit C of the present embodiment.

  As shown in FIGS. 1 and 2, the image forming unit C includes a registration roller pair 106, a laser scanner 111, a photosensitive drum 112, an image writing optical system 113, a developing device 114, a transfer roller 115, A conveyance unit 117, a fixing device 118, a discharge roller 119, and a tray 120 are included. The image forming unit C also includes a controller 100 that performs overall control of operations, drive motors M1 and M2 that drive the units, and drive control units 22 and 101 that control the drive motors M1 and M2, respectively. have. Further, the image forming unit C includes a sensor light receiving unit 23, a thermistor 24, a sensor light emitting unit 25, an environment measuring unit 102, an input unit 103, and a counter 104.

  The drive control unit 22 controls the drive of the drive motor M <b> 1 according to the control of the controller 100.

  The sensor light receiving unit 23 receives the light emitted from the sensor light emitting unit 25 and outputs a detection signal of the received light to the controller 100.

  The sensor light emitting unit 25 emits light toward the sensor light receiving unit 23. The sensor light emitting unit 25 and the sensor light receiving unit 23 constitute a paper detection sensor that detects whether or not the recording material has been conveyed.

  The controller 100 (control unit) includes a CPU 100a, an information recording unit 100b, and a temperature control unit 100d. The controller 100 controls the driving of the drive control unit 22 and the drive control unit 101, and conditions for the fixing process in the fixing device 118 based on the measurement result in the environment measurement unit 102 or the attribute information input from the input unit 103. To change.

  The temperature controller 100d controls the temperature of the heater 13 according to the control of the CPU 100a. The temperature control unit 100 d performs temperature control of the heater 13 according to the temperature measured by the thermistor 24.

  The input unit 103 receives an external input of attribute information indicating the weight per unit area of the recording material, and outputs it to the CPU 100a.

  The drive control unit 101 controls the driving of the driving motor M <b> 2 according to the control of the controller 100 to control the recording material conveyance speed in the fixing device 118.

  The registration roller pair 106 includes a first roller 106a and a second roller 106b. The second roller 106b rotates following the rotation of the first roller 106a. The registration roller pair 106 forms a recording material between the photosensitive drum 112 and the transfer roller 115 when the first roller 106a rotates in synchronization with the rotation of the photosensitive drum 112 by driving the driving motor M1. Then, it is conveyed to the transferred transfer part R. When the driving of the first roller 106a of the driving motor M1 is stopped, the recording material conveyance operation to the transfer roller 115 is stopped. When the driving motor M1 resumes driving, the first roller 106a rotates again, so that the recording material conveyance operation to the transfer portion R is resumed.

  The environment measurement unit 102 measures the environmental temperature and humidity of the image forming apparatus A, and outputs the measurement result to the CPU 100 a of the controller 100.

  The input unit 103 can input attribute information from the outside, and outputs the input attribute information to the controller 100.

  The laser scanner 111 emits image information read by the scanner unit B based on the electrical signal transmitted from the scanner unit B.

  The photosensitive drum 112 as an image carrier is uniformly charged by a charging roller (not shown). An electrostatic latent image is formed on the photosensitive drum 112 by being scanned by the image writing optical system 113.

  The image writing optical system 113 scans the photosensitive drum 112 with laser light corresponding to the image information emitted from the laser scanner 111 to form an electrostatic latent image on the surface of the photosensitive drum 112.

  The developing device 114 develops the electrostatic latent image formed on the photosensitive drum 112 to form a developer image on the photosensitive drum 112.

  The transfer roller 115 transfers the developer image formed on the photosensitive drum 112 to the recording material supplied from the feeding unit U1 or the feeding unit U2 in synchronization with the rotation of the photosensitive drum 112.

  The conveyance unit 117 conveys the recording material onto which the developer image has been transferred from the transfer roller 115 to the fixing device 118.

  The fixing device 118 heats and presses the recording material conveyed from the conveyance unit 117 and conveys the recording material toward the discharge roller 119, thereby fixing the developer image transferred to the recording material to the recording material. Do. The fixing device 118 is formed with a nip portion N for fixing the developer image transferred to the recording material to the recording material. Details of the configuration of the fixing device 118 will be described later.

  The discharge roller 119 discharges the recording material on which the developer image is fixed by the fixing device 118 to the tray 120.

  The tray 120 is disposed outside the image forming apparatus A, and sequentially stacks the recording materials discharged by the discharge roller 119.

  The counter 104 (counting unit) counts the number of sheets that the image forming apparatus A has passed.

  The drive motor M <b> 1 is driven according to the control of the drive control unit 22 to rotate the registration roller pair 106. The drive motor M2 is driven according to the control of the drive control unit 101 to rotate the pressure roller 18 (pressure body).

(Configuration of fixing device)
Next, the configuration of the fixing device 118 will be described.

  The fixing device 118 film heating method shown in FIGS. 1 and 2 is adopted, and has a stay 11, a fixing film 12 (heating body), a heater 13, a pressure roller 18, and a thermistor 24.

  The stay 11 is formed of a heat resistant resin, and is disposed inside the fixing film 12 to serve as a rotation guide member for the fixing film 12.

  The heater 13 is fixed to the stay 11. The heater 13 supplies heat to the recording material via the fixing film 12 by being in pressure contact with the pressure roller 18 via the fixing film 12. The heater 13 is held by the stay 11 and is provided at a position that slides with the fixing film 12. As the heater 13, a plate having a low heat capacity is used. In this embodiment, the surface of an insulating ceramic substrate such as alumina or aluminum nitride is screen-printed with a conductive heating resistance layer such as Ag / Pd (silver palladium), RuO2, Ta2N along the longitudinal direction of the substrate. Is used. In addition, a configuration in which a protective layer such as a glass layer that protects the energization heating resistance layer may be provided on the sliding surface with the inner peripheral surface of the fixing film 12 within a range that does not impair the thermal efficiency.

  The stay 11 holds the heater 13 and is formed of a heat resistant resin such as a liquid crystal polymer, a phenol resin, PPS, or PEEK. The stay 11 also has a function of guiding the rotation of the fixing film 12 in addition to holding the heater 13.

  As the fixing film 12 in the present embodiment, a heat resistant film having a layer thickness of 200 μm or less is used in order to enable quick start. In order to ensure durability, the layer thickness is desirably 20 μm or more. That is, in this embodiment, a fixing film having a layer thickness of 20 μm or more and 200 μm or less is used.

  Further, the fixing film 12 in the present embodiment has a multilayer structure formed of a base layer, an adhesive layer, and a surface layer. As the base layer, a heat-resistant resin such as polyimide, polyamideimide, or PEEK, or a pure metal such as SUS, Al, Ni, Cu, or Zn having heat resistance and high thermal conductivity, an alloy, or the like is used.

  As the surface layer, resins such as PTFE (polytetrafluoroethylene), PFA (tetrafluoroethylene perfluoroalkyl vinyl ether copolymer), and FEP (tetrafluoroethylene hexafluoropropylene copolymer) are used. Further, as the surface layer, a resin such as ETFE (ethylene tetrafluoroethylene copolymer), CTFE (polychlorotrifluoroethylene), PVDF (polyvinylidene fluoride), or the like may be used. By configuring the surface layer of the fixing film 12 in this way, the releasability of the fixing film 12 is improved.

  The fixing film 12 that is a fixing rotating body is endless (endless) and cylindrical, has an inner peripheral length that is, for example, 3 mm longer than the outer peripheral length of the stay 11, and is loosely fitted to the stay 11. The fixing film 12 can be rotated clockwise in FIG. 2 while its inner surface is in close contact with the surface of the heater 13 by the rotation of the pressure roller 18. The fixing film 12 heats the recording material with heat from the heater 13.

  A pressure roller 18 that is a pressure rotator is a roller and rotates the fixing film 12 and presses the recording material against the fixing film 12. The pressure roller 18 can be rotated counterclockwise in FIG. 2 by being driven by the driving motor M2.

  The thermistor 24 measures the temperature on the non-heating surface side of the heater 13.

  Next, the pressure roller 18 will be described.

  FIG. 3 is a cross-sectional view showing the configuration of the pressure roller 18.

  As shown in the figure, the pressure roller 18 includes a pipe-shaped metal core 18b made of metal such as SUS, SUM, and Al, a shaft portion 18c, a bearing portion 18d, and an elastic layer 18a formed outside the metal core 18b. Consists of.

A hollow portion 18e (hollow portion) is formed at the center portion surrounded by the bearing portion 18d and the cored bar 18b. That is,
As the elastic layer 18a, an elastic solid rubber layer formed of heat-resistant rubber such as silicone rubber or fluorine rubber, or an elastic sponge rubber layer formed by foaming silicone rubber to provide a more heat insulating effect is used. Further, as the elastic layer 18a, an elastic cellular rubber layer in which a hollow filler (such as a microballoon) is dispersed in the silicone rubber layer and a gas portion is provided in the cured product to enhance the heat insulating effect may be used. Good.

  Further, a release layer such as perfluoroalkoxy resin (PFA) or polytetrafluoroethylene resin (PTFE) is formed on the surface of the elastic layer 18a. The longitudinal width of the elastic layer 18a and the cored bar 18b is 306 mm, and the longitudinal width of the bearing portion 18d is 20 mm.

  When A4R size paper having a paper width of 210 mm in the longitudinal direction is passed, the non-paper passing area and the core metal hollow area are 28 mm.

(Configuration of end cooling unit)
Further, since the maximum sheet passing width of the image forming apparatus A is 297 mm (A4 width), when a recording material having a small width such as a sheet width of 210 mm (A4 length) (hereinafter referred to as a small size sheet) is continuously passed, The temperature rises in the paper passing area (non-paper passing part temperature rise). For this reason, the edge part cooling part which prevents a non-sheet passing part temperature rising is provided.

  FIG. 4 is a diagram showing a configuration of the pressure roller 18 and a conventional end cooling unit 21 that cools the end of the pressure roller 18.

  As shown in the figure, the end cooling unit 21 includes two cooling fans 21 a that cool the end of the pressure roller 18 and a shutter 21 c. The cooling fan 21a is a DC axial flow fan having a size of 60 mm in length and 60 mm in width, an operating current of 0.1 A, a rated voltage of 24 V, and a rated rotation speed of 4400 rpm.

  As a specific operation of the end cooling unit 21, when passing a small size paper having a width of A4 vertical or B4, the shutter 21c is opened to the vicinity of the paper edge, and the cooling fan 21a is rotated. Only the non-sheet passing area of the pressure roller 18 is cooled by the wind generated by the rotation of the cooling fan 21a.

  On the other hand, when passing a large size such as A3 portrait or A4 landscape, the temperature of the non-sheet passing portion does not rise, and there is no need to cool, so the shutter 21c is closed or the cooling fan 21a is not operated.

  Thus, the non-sheet passing portion temperature rise is prevented by controlling the end cooling portion 21.

  However, when the A4 portrait is continuously passed by the fixing device having the pressure roller 18 of FIG. 4, the heat capacity is in the solid part (areas C and G) and the hollow part (areas D and F) even in the non-sheet passing area. Therefore, temperature unevenness occurs on the surface of the pressure roller 18.

  FIG. 5 is a graph showing the transition of the surface temperature of the pressure roller 18 when 500 sheets of A4R paper are continuously passed by the hollow pressure roller 18 shown in FIG. The horizontal axis represents the regions C, D, E, F, and G from the left in the longitudinal direction of the pressure roller 18, and the vertical axis represents the surface temperature of the pressure roller 18.

  As shown in the figure, the surface temperature of the pressure roller 18 is 186 ° C. in the regions C and G, while the regions D and F rise to 212 ° C. because the heat capacity of the pressure roller 18 is small. The difference was 28 ° C.

  If a high-printed image such as solid black is passed through a large size paper such as A3 in a state where temperature unevenness occurs on the surface of the pressure roller 18, uneven glossiness occurs.

  Therefore, in the present embodiment, when passing small-size paper with the hollow pressure roller 18, the cooling strength of the non-paper passing and the hollow region is increased, and the cooling strength of the non-paper passing and the solid region is decreased. Thus, the occurrence of temperature unevenness on the surface of the pressure roller 18 is prevented.

  FIG. 6 is a diagram illustrating a configuration of the end cooling unit 210 (cooling unit) of the present embodiment.

  As shown in the figure, the slit plate 31 (wind power reducing means) is installed in the region C and region G between the solid region of the pressure roller 18 and the cooling fan 21a (air blower fan). The cooling intensity for the solid area is weakened. The regions C and G located at both axial ends of the pressure roller 18 constitute a first portion of the pressure roller 18 and are located between both axial portions of the pressure roller 18. D, E, and F constitute a second portion of the pressure roller 18. A region D is a hollow portion of the pressure roller 18 and a region through which the recording material does not pass, and a region E is a region (passing region) through which the recording material of the pressure roller 18 passes.

  The slit plate 31 has a longitudinal width of 20 mm, the width of the slit through which the cooling fan 21a passes is 1 mm, and 10 slits are provided at intervals of 1 mm. Further, the shutter 211 is provided with a guide 211a (air blowing guide) that prevents the cooling fan 21a from flowing into the sheet passing area. The shutter 211 moves according to the width of the paper to be passed. Therefore, the guide 211a moves in accordance with the paper width when passing a plurality of paper widths, and suppresses the wind from the cooling fan 21a from flowing to the pressure roller 18 in the paper passing area.

  FIG. 7 is an enlarged view of an end portion of the fixing device of the present embodiment when A4R paper is passed. In the figure, the size of arrows P and Q represents the strength of the wind from the cooling fan 21a. As indicated by these arrows P and Q, the area C (non-sheet passing area and solid part) has a slit plate 31 between the cooling fan 21a and the pressure roller 18, so that the wind force is reduced and the area D (non-passage area) The wind of the cooling fan 21a is weaker than the paper passing area and the hollow portion, and the cooling power is weakened.

(Operation)
Next, the operation of the image forming apparatus of this embodiment will be described.

  FIG. 8 is a flowchart showing the operation of the image forming apparatus of this embodiment.

  As shown in the figure, when the user inputs JOB and starts the printing operation, the image forming apparatus A detects an image formation request (step S101). The image forming apparatus A determines whether the width of the recording material to be passed is 297 mm or more from the JOB information input by the user (step S102). When the width of the recording material is 297 mm or more, it is determined that the non-sheet-passing portion temperature rise does not occur, the printing operation is executed without executing the edge cooling operation (step S103), and the recording material is placed in the tray 120. The printing operation ends (step S104).

  If the width of the recording material to be passed is less than 297 mm in step S102, it is determined whether or not the number of passed sheets is 20 or more (step S105). When the number of sheets to be passed is less than 20, the non-sheet passing portion temperature does not rise so that an abnormal image is generated, and it is not necessary to perform the edge cooling control, so the edge cooling operation is not executed. Then, the printing operation is executed (step S103), the recording material is discharged to the tray 120, and the printing operation is finished (step S104).

  When the width of the recording material to be passed is less than 297 mm and the number of passed sheets is 20 or more (steps S102 and S105), the temperature of the non-sheet passing portion is raised to a temperature at which an abnormal image occurs. There is a fear. For this reason, the shutter 211 is opened to the width of the paper to be passed (step S106), and the cooling fan 21a is rotated to 4400 rpm to lower the pressure roller surface temperature (step S107).

  When the number of sheets input by the user is reached, the printing operation is terminated (step S108), and 30 seconds after the printing operation is terminated, the rotation of the cooling fan 21a is stopped (step S109), and the shutter 211 is closed (step S110). .

  FIG. 9 is a graph showing the transition of the surface temperature of the pressure roller 18 when 500 sheets of A4R paper are continuously passed by the pressure roller 18 when the image forming apparatus of this embodiment is used. In the figure, the horizontal axis represents regions C, D, E, F, and G from the left in the longitudinal direction of the pressure roller 18, and the vertical axis represents the surface temperature of the pressure roller 18.

  As shown in the figure, in this embodiment, the surface temperature of the pressure roller 18 in the regions D and F is 194 ° C., and the temperature difference from the surface temperature of the pressure roller 18 in the regions C and G is reduced to 8 ° C. Was made.

  FIG. 10 is a table showing the difference in surface temperature of the pressure roller 18 and the presence or absence of occurrence of gloss unevenness in the present embodiment and the conventional image forming apparatus. In the conventional image forming apparatus, the temperature difference on the surface of the pressure roller 18 is 28 ° C. and uneven gloss occurs, but in this embodiment, the temperature difference on the surface of the pressure roller 18 is 8 ° C. and uneven gloss. There was no outbreak.

Second Embodiment
In the present embodiment, the overall configuration of the image forming apparatus and the basic configuration of the fixing device are the same as those in the first embodiment, and a description thereof will be omitted.

  FIG. 11 is a diagram illustrating a configuration of the fixing device 118 of the present embodiment.

  As shown in the figure, in the present embodiment, cooling fans 21a (first blowing fans) and 21b (second blowing fans) are provided in the hollow area and the solid area of the hollow pressure roller 18, respectively. The occurrence of uneven surface temperature of the pressure roller 18 is prevented by changing the air volume when passing a narrow recording material such as A4R paper. Further, by providing a guide plate 32 (air blowing guide), mixing of wind from the cooling fans 21a and 21b is prevented, and cooling suitable for each is performed. On the other hand, when passing a large size such as A3 portrait or A4 landscape, the non-sheet passing portion does not increase in temperature and does not need to be cooled. Therefore, the shutter 21c is closed or the cooling fans 21a and 21b are not operated. To do.

  FIG. 12 is a diagram showing a fixing device when A4R paper is passed in the present embodiment. The size of arrows R and S shown in the figure represents the strength of the wind from the cooling fans 21a and 21b.

  Regions D and F (non-sheet passing regions and hollow portions) have a small heat capacity and are likely to rise in temperature. Is also high.

  In FIG. 12, the shutter 211 of the first embodiment shown in FIGS. 6 and 7 is used.

(Operation)
Next, the operation of the image forming apparatus A in the present embodiment will be described.

  FIG. 13 is a flowchart showing the operation of the image forming apparatus A in the present embodiment.

  As shown in the figure, when the user inputs JOB and starts the printing operation, the image forming apparatus A detects an image formation request (step S201). The image forming apparatus A determines whether the width of the recording material to be passed is 297 mm or more from the JOB information input by the user (step S202). When the width of the recording material is 297 mm or more, it is determined that the non-sheet-passing portion temperature rise does not occur, the printing operation is executed without executing the edge cooling operation (step S203), and the recording material is placed in the tray 120. And the printing is finished (step S204).

  In step S202, if the width of the recording material to be passed is less than 297 mm, it is determined whether or not the number of passed sheets is 20 or more (step S205). When the number of sheets to be passed is less than 20, the non-sheet passing portion temperature does not rise so that an abnormal image is generated, and it is not necessary to perform the edge cooling control, so the edge cooling operation is not executed. Then, a printing operation is executed (step S203), and the recording material is discharged to the tray 120, and the process is ended (step S204).

  When the width of the recording material to be passed is less than 297 mm and the number of passed sheets is 20 or more (steps S202 and S205), the non-sheet passing portion is heated to a temperature at which an abnormal image occurs. Therefore, the shutter is opened to the width of the paper to be passed (step S206).

  Next, it is determined whether or not the opening width of the shutter is less than 20 mm (step S207). If the opening width of the shutter is less than 20 mm, the cooling fan 21a is rotated at 2200 rpm because there is no paper passing and there is no hollow area and the cooling fan 21b does not need to be rotated (step S208). When the number entered by the user is reached, the printing operation is terminated (step S209), and 30 seconds after the printing operation is terminated, the rotation of the cooling fan 21a is stopped (step S210), and the shutter is closed (step S211). ), And it ends.

  On the other hand, if the shutter opening width is 20 mm or more in step S207, the cooling fan 21a is rotated at 2200 rpm and the cooling fan 21b is rotated at 4400 rpm (step S212). When the number of sheets input by the user is reached, the printing operation is terminated (step S213), the shutter is closed (step S214), and the process is terminated.

  FIG. 14 is a table showing the difference in the surface temperature of the pressure roller 18 and the presence / absence of gloss unevenness in this embodiment and the conventional image forming apparatus. In the conventional image forming apparatus, the temperature difference on the surface of the pressure roller 18 is 28 ° C. and uneven gloss is generated. In the present embodiment, the temperature difference on the surface of the pressure roller 18 is 5 ° C. and uneven gloss. There was no outbreak.

  In the above-described embodiment, the DC axial flow fan is used as the cooling fan. However, for example, contact-type cooling means such as a heat pipe or a heat radiation roller can be used.

  In this manner, in the fixing device 118 using the pressure roller 18 having different heat capacity distribution in each part, the cooling means of the fixing device is controlled in accordance with the heat capacity distribution of the pressure roller, so that the surface of the pressure roller 18 is controlled. The temperature difference can be reduced and gloss unevenness can be prevented.

  The present invention is not limited to the present embodiment with respect to the type, arrangement, number, and the like of the members, and is appropriately replaced within the scope not departing from the gist of the invention, such as appropriately replacing the constituent elements with those having the same effects. It can be changed.

DESCRIPTION OF SYMBOLS 13 ... Fixing film 18 ... Pressure roller 18e ... Hollow part 21 ... End part cooling part 21a ... Cooling fan 21b ... Cooling fan 31 ... Slit board 32 ... Guide board 104 ... Counter 118 ... Fixing device 210 ... End part cooling part 211a ... Guide A ... Image forming apparatus

Claims (10)

A heating body for applying heat to the toner image formed on the recording material;
A pressure body that sandwiches the recording material with the heating body and applies pressure to the recording material;
Cooling means for cooling the pressurizing body with different cooling powers corresponding to heat capacities corresponding to the portions of the pressurizing body that sandwich the recording material;
A fixing device.   The fixing device according to claim 1, wherein the cooling unit cools the pressure member with a larger cooling power as the heat capacity is smaller. The pressure body is in the form of a roller, and is located between the first region located at both ends in the axial direction of the pressure body and the both ends of the pressure body, and from the first portion And a second region having a small heat capacity,
The fixing device according to claim 2, wherein the cooling unit cools a portion of the second area where the recording material is not sandwiched with a cooling power larger than that of the first area.   The fixing device according to claim 3, wherein the second region has a hollow structure. The cooling means has a blower fan that cools the first region and the second region,
5. The fixing device according to claim 3, wherein the fixing device includes a wind force reducing unit that reduces wind force generated by the blower fan between the blower fan and the first region.   The fixing device according to claim 5, wherein the wind force reducing unit includes a blowing guide that suppresses the flow of the wind from the blowing fan to a portion of the pressurizing member that sandwiches the recording material. The cooling means includes a first blower fan that cools the first region, and a second blower fan that cools a portion of the second region that does not sandwich the recording material,
5. The fixing device according to claim 3, wherein a blowing force of the second blowing fan is larger than a blowing force of the first blowing fan.   The said cooling means has a ventilation guide which guides ventilation so that the wind by a said 1st ventilation fan and the wind by a said 2nd ventilation fan may be mixed. Fixing device. Counting means for counting the number of recording materials subjected to fixing processing by the fixing device;
Control means for controlling the cooling means according to the number counted by the counting means;
The fixing device according to claim 1, further comprising: Image forming means for forming the toner image on the recording material;
A fixing device according to any one of claims 1 to 9,
An image forming apparatus comprising:

Images