Image forming device

Abstract

To appropriately cool non-paper feeding parts at the ends in a longitudinal direction of a heating member or a pressure member with a simple configuration.SOLUTION: In an image forming apparatus 100 comprising a fixing device 300 that brings a heating member (fixing roller 310) and a pressure member (pressure roller 320) having a longitudinal direction into pressure contact with each other to form a nip part (fixing nip SN), transfers heat to a sheet member (paper P) passing through the nip part from the heating member, and heats and fixes a toner image carried on the sheet member, ducts 510 blowing air to both ends in the longitudinal direction of the heating member or the pressure member are disposed movably in a direction crossing the longitudinal direction.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus equipped with a fixing device that forms a nip portion for fixing between a heating member and a pressure member, and in particular to an image forming apparatus that uses a simple configuration to appropriately cool both longitudinal ends of the heating member or pressure member to prevent excessive heating when a small-sized sheet member (paper) is passed through the nip portion. [Background technology]

[0002] In the fixing device of an electrophotographic image forming apparatus, the toner image is heated and fixed by passing a sheet of paper carrying the toner image through a nip between a heating member (fixing member) and a pressure member. When small-sized paper is continuously printed using such a fixing device, the temperature of the longitudinal ends (non-paper passing portions) of the heating member and pressure member may rise excessively (end overheating). When end overheating occurs, the durability of the heating member and pressure member may decrease, paper may wrap around the heating member, causing jams, and problems such as high-temperature offset may occur.

[0003] Therefore, in the past, in order to prevent the end portions from overheating, cooling air has been blown onto non-paper passing portions at the longitudinal ends of the heating member and pressure applying member. For example, in the fixing device of Patent Document 1, a swingable partition plate arranged in the air blowing duct is deployed according to the paper size to appropriately distribute the air volume of the upstream blowing fan along the longitudinal direction of the heating member and pressure applying member. In addition, in the fixing device of Patent Document 2, the blowing port (nozzle) of the air blowing duct is arranged so as to be movable along the longitudinal direction of the heating member and pressure applying member. Summary of the Invention [Problem to be solved by the invention]

[0004] However, there are nearly 10 different paper sizes, from small to large, and for this reason, even with the fixing devices of Patent Documents 1 and 2, it is not easy to adequately cool only the necessary ranges in the longitudinal direction of the heating member and pressure member for each paper size.

[0005] That is, in order to perform such appropriate cooling in Patent Document 1, it is necessary to increase the number of partition plates or to make the partition plates larger. Also, in order to perform the appropriate cooling in the device of Patent Document 2, it is necessary to further increase the number of air outlets (nozzles). However, doing so makes it unavoidable that the fixing device becomes larger and more complicated, resulting in increased costs.

[0006] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to appropriately cool non-sheet passing portions at longitudinal ends of a heating member and a pressure member using a simple structure. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the image forming apparatus of the present invention is an image forming apparatus equipped with a fixing device in which a heating member and a pressure member having a longitudinal direction are pressed together to form a nip portion, heat is transferred from the heating member to a sheet member passing through the nip portion, and a toner image carried on the sheet member is heated and fixed, and is characterized in that a duct for blowing air to both longitudinal ends of the heating member or the pressure member is arranged so as to be movable in a direction transverse to the longitudinal direction. Effect of the Invention

[0008] According to the present invention, non-sheet passing portions at the longitudinal ends of the heating member and the pressure member can be appropriately cooled with a simple configuration. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2A] FIG. 2 is a plan view of the fixing device according to the first embodiment of the present invention when approaching a duct. [Figure 2B] FIG. 2 is a plan view of the fixing device according to the first embodiment of the present invention when the duct is separated. [Figure 2C] 1 is a cross-sectional view of a fixing device in which a fixing belt is used instead of a fixing roller. [Figure 2D] FIG. 2 is a plan view of a heater that heats the fixing belt. [Figure 3A]11A and 11B are a side view and a front view showing a fixing device according to a second embodiment of the present invention when the fixing device approaches a duct. [Figure 3B] 11A and 11B are a side view and a front view showing a fixing device according to a second embodiment of the present invention when a duct is separated. [Figure 3Adef] 13A and 13B are a side view and a front view showing a fixing device according to a modified example of the second embodiment of the present invention when the fixing device approaches a duct. [Figure 3Bdef] 13A and 13B are a side view and a front view showing a fixing device according to a modified example of the second embodiment of the present invention when the duct is separated. [Figure 4A] 13A and 13B are a plan view and a front view showing a fixing device according to a third embodiment of the present invention when the fixing device approaches a duct. [Figure 4B] 13A and 13B are a plan view and a front view showing a fixing device according to a third embodiment of the present invention when the duct is separated. [Figure 5A] 13 is a front view of a fixing device according to a fourth embodiment of the present invention when the opening width of an air outlet member is enlarged. FIG. [Figure 5B] 13 is a front view of a fixing device according to a fourth embodiment of the present invention when the opening width of an air outlet member is reduced. FIG. [Figure 6] 6A and 6B are diagrams showing temperature changes of a fixing roller when the rotation speed of a cooling fan is increased or decreased in response to a printing operation of the fixing device. [Figure 7] 1A is a plan view of a fixing device when approaching a duct, (b) is a plan view showing the state where the area of ​​the air outlet is changed when the duct is separated, (c) is a plan view showing the state where the orientation is changed, and (d) is a plan view showing the state where the shape is changed. [Figure 8A] FIG. 13 is a side view of the fixing device according to the fifth embodiment of the present invention when approaching a duct. [Figure 8B] FIG. 13 is a side view of the fixing device according to the fifth embodiment of the present invention when the duct is separated. [Figure 8C] FIG. 13 is a diagram showing the swinging state of the duct when (a) the duct approaches and when (b) the duct moves away. [Figure 9A] FIG. 13 is a side view of the fixing device according to the sixth embodiment of the present invention when approaching a duct. [Figure 9B]FIG. 13 is a side view of the fixing device according to the sixth embodiment of the present invention when the duct is separated. [Figure 10A] FIG. 13 is a plan view of a fixing device according to a seventh embodiment of the present invention when approaching a duct. [Figure 10B] FIG. 13 is a plan view of a fixing device according to a seventh embodiment of the present invention when the duct is separated. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of an image forming apparatus (laser printer) according to the present invention will be described with reference to the drawings. A laser printer is one example of an image forming apparatus, and the image forming apparatus is of course not limited to a laser printer. In other words, the image forming apparatus can be configured as any one of a copier, a facsimile, a printer, a printing machine, and an inkjet recording apparatus, or as a multifunction machine that combines at least two or more of these.

[0011] In addition, the same or corresponding parts in each drawing are given the same reference numerals, and duplicated explanations are appropriately simplified or omitted. Furthermore, the dimensions, materials, shapes, relative positions, etc. in the explanations of each component are examples, and unless otherwise specified, the scope of this invention is not limited to them.

[0012] In the following embodiments, the sheet member (recording medium) will be described as "paper", but the "recording medium" is not limited to paper. The "recording medium" includes not only paper but also overhead projector sheets, fabrics, metal sheets, plastic films, and prepreg sheets made of carbon fibers pre-impregnated with resin.

[0013] All media to which a developer or ink can be attached, recording paper, and recording sheets are included in the "recording medium." In addition to plain paper, "paper" also includes cardboard, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, etc. In the following explanation, "image formation" refers not only to applying images such as characters and figures to a medium, but also to applying patterns and other designs to a medium.

[0014] (● Laser printer configuration) 1 is a schematic diagram showing the configuration of a color laser printer as an embodiment of an image forming apparatus 100 equipped with a fixing device 300. The image forming apparatus 100 includes four process units 1K, 1Y, 1M, and 1C as image forming means. These process units form images using developers of the colors black (K), yellow (Y), magenta (M), and cyan (C) that correspond to the color separation components of a color image. The image forming means may be of an indirect transfer type that uses an intermediate transfer belt 16 described below, or of a direct transfer type that transfers toner images formed by the process units 1K, 1Y, 1M, and 1C directly to paper without using the intermediate transfer belt 16.

[0015] Each process unit 1K, 1Y, 1M, and 1C has the same configuration, except that it has toner bottles 6K, 6Y, 6M, and 6C that contain unused toner of different colors. Therefore, the configuration of one process unit 1K will be described below, and descriptions of the other process units 1Y, 1M, and 1C will be omitted.

[0016] The process unit 1K has an image carrier 2K (e.g., a photosensitive drum), a drum cleaning device 3K, and a charge removal device. The process unit 1K further has a charging device 4K as a charging means for uniformly charging the surface of the image carrier, and a developing device 5K as a developing means for performing visible image processing of the electrostatic latent image formed on the image carrier. The process unit 1K is detachably mounted on the main body of the image forming apparatus 100, and consumable parts can be replaced at the same time.

[0017] The exposure unit 7 is disposed above each of the process units 1K, 1Y, 1M, and 1C installed in the image forming apparatus 100. The exposure unit 7 is configured to perform writing scanning according to image information, that is, to reflect laser light L from a laser diode by a mirror 7a based on image data and irradiate the image carrier 2K.

[0018] In this embodiment, the transfer device 15 is disposed below each of the process units 1K, 1Y, 1M, and 1C. The primary transfer rollers 19K, 19Y, 19M, and 19C are disposed in contact with the intermediate transfer belt 16 and opposed to the image carriers 2K, 2Y, 2M, and 2C, respectively.

[0019] The intermediate transfer belt 16 circulates around the primary transfer rollers 19K, 19Y, 19M, and 19C, the drive roller 18, and the driven roller 17. The secondary transfer roller 20 is disposed opposite the drive roller 18 and in contact with the intermediate transfer belt 16. If the image carriers 2K, 2Y, 2M, and 2C are the first image carriers for the respective colors, then the intermediate transfer belt 16 is the second image carrier that combines these images.

[0020] The belt cleaning device 21 is disposed downstream of the secondary transfer roller 20 in the running direction of the intermediate transfer belt 16. In addition, a cleaning backup roller is disposed on the opposite side of the intermediate transfer belt 16 to the belt cleaning device 21.

[0021] A paper feeder 200 having a tray for stacking paper P is installed below the image forming apparatus 100. This paper feeder 200 constitutes a recording medium supply section, and is capable of storing a large number of sheets of paper P as recording media in a bundle. The paper feeder 200 is unitized with a paper feed roller 60 and a roller pair 210 as a means for transporting paper P.

[0022] The paper feed device 200 can be inserted into and removed from the main body of the image forming apparatus 100 for the purpose of replenishing paper, etc. The paper feed roller 60 and the roller pair 210 are disposed above the paper feed device 200, and are configured to transport the topmost paper P of the paper feed device 200 toward the paper feed path 32.

[0023] The pair of registration rollers 250 as a separation conveying means are disposed immediately upstream of the secondary transfer roller 20 in the conveying direction, and can temporarily stop the paper P fed from the paper feeding device 200. This temporary stop creates slack in the leading edge of the paper P, and corrects the skew of the paper P.

[0024] A registration sensor 31 is disposed immediately upstream of the registration roller pair 250 in the conveying direction, and the passage of the leading edge of the paper is detected by this registration sensor 31. When a predetermined time has elapsed after the registration sensor 31 detects the passage of the leading edge of the paper, the paper is abutted against the registration roller pair 250 and temporarily stops.

[0025] A transport roller 240 is disposed at the downstream end of the paper feed device 200 for transporting the paper upward, the paper having been transported to the right from the roller pair 210. As shown in FIG. 1, the transport roller 240 transports the paper upward toward the registration roller pair 250.

[0026] The roller pair 210 is composed of a pair of upper and lower rollers. The roller pair 210 may be of an FRR separation type or an FR separation type.

[0027] In the FRR separation method, a separation roller (return roller) to which a fixed amount of torque is applied in the counter-feed direction by the drive shaft via a torque limiter is pressed against the feed roller to separate the paper in the nip between the rollers.In the FR separation method, a separation roller (friction roller) supported on a fixed shaft is pressed against the feed roller via a torque limiter to separate the paper in the nip between the rollers.

[0028] In this embodiment, the roller pair 210 is configured using the FRR separation method. That is, the roller pair 210 is configured with an upper feed roller 220 that transports the paper into the machine, and a lower separation roller 230 that is given a driving force by a drive shaft via a torque limiter in the opposite direction to the feed roller 220.

[0029] The separation roller 230 is biased by a biasing means such as a spring toward the feed roller 220. The feed roller 60 rotates counterclockwise in FIG. 1 by transmitting the driving force of the feed roller 220 via a clutch means.

[0030] The paper P, which has been struck against the registration roller pair 250 and has a slack formed at its leading edge, is sent to the secondary transfer nip between the secondary transfer roller 20 and the drive roller 18 in time for the toner image formed on the intermediate transfer belt 16 to be suitably transferred. The toner image formed on the intermediate transfer belt 16 is then electrostatically transferred to the desired transfer position with high precision by a bias applied to the secondary transfer nip of the sent-out paper P.

[0031] The post-transfer transport path 33 is disposed above the secondary transfer nip between the secondary transfer roller 20 and the drive roller 18. The fixing device 300 is installed near the upper end of the post-transfer transport path 33. The fixing device 300 includes a fixing roller 310 as a heating member containing a heat generating member such as a halogen lamp, and a pressure roller 320 as a pressure member that rotates while contacting the fixing roller 310 with a predetermined pressure.

[0032] The fixing roller 310 and the pressure roller 320 have their longitudinal directions parallel to each other. A nip portion is formed at the pressure contact portion between the fixing roller 310 and the pressure roller 320, through which a sheet P carrying a toner image is passed to fix the toner image onto the sheet.

[0033] The post-fixing transport path 35 is disposed above the fixing device 300, and at the upper end of the post-fixing transport path 35, it branches into a paper discharge path 36 and a reversing transport path 41. A switching member 42 is disposed at this branching point, and the switching member 42 is adapted to swing about its swing shaft 42a. A pair of paper discharge rollers 37 is disposed near the open end of the paper discharge path 36.

[0034] The reverse conveying path 41 merges with the paper feed path 32 at the other end opposite to the branching portion. A pair of reverse conveying rollers 43 is disposed midway along the reverse conveying path 41. The paper output tray 44 is disposed on the upper portion of the image forming apparatus 100, forming a concave shape facing inward of the image forming apparatus 100.

[0035] The powder container 10 (for example, a toner container) is disposed between the transfer device 15 and the paper feed device 200. The powder container 10 is detachably attached to the main body of the image forming apparatus 100.

[0036] In the image forming apparatus 100 of this embodiment, a certain distance is necessary between the paper feed roller 60 and the secondary transfer roller 20 due to the relationship with the transfer paper transport. The powder container 10 is installed in the dead space generated in this distance, thereby making the entire laser printer smaller.

[0037] The transfer cover 8 is installed on the top of the paper feed device 200, in front of the paper feed device 200 in the pull-out direction. By opening the transfer cover 8, it is possible to inspect the inside of the image forming apparatus 100. The transfer cover 8 is provided with a manual feed roller 45 for manual paper feed and a manual feed tray 46 for manual paper feed.

[0038] (● Laser printer operation) Next, the basic operation of the laser printer according to this embodiment will be described below with reference to Fig. 1. First, single-sided printing will be described.

[0039] 1, the paper feed roller 60 rotates in response to a paper feed signal from the control unit of the image forming apparatus 100. Then, the paper feed roller 60 separates only the topmost sheet of the stack of papers P loaded in the paper feed device 200, and sends it to the paper feed path 32.

[0040] When the leading edge of the paper P sent out by the paper feed roller 60 and the roller pair 210 reaches the nip of the registration roller pair 250, it forms a slack and waits in that state. Then, the toner image formed on the intermediate transfer belt 16 is transferred to the paper P at the optimal timing (synchronization), and the leading edge skew of the paper P is corrected.

[0041] In the case of manual paper feeding, a stack of papers stacked on manual feed tray 46 is conveyed one by one, starting from the topmost paper, through a part of reverse conveyance path 41 by manual paper feed roller 45 to the nip of registration roller pair 250. The subsequent operation is the same as that of paper feeding from paper feeder 200.

[0042] Here, the image forming operation will be described for one process unit 1K, and the description of the other process units 1Y, 1M, and 1C will be omitted. First, the charging device 4K uniformly charges the surface of the image carrier 2K to a high potential. Then, the exposure device 7 irradiates the surface of the image carrier 2K with laser light L based on image data.

[0043] The potential of the irradiated portion of the surface of the image carrier 2K is reduced, forming an electrostatic latent image. The developing device 5K has a developer carrier that carries a developer containing toner, and transfers unused black toner supplied from a toner bottle 6K, via the developer carrier, to the surface portion of the image carrier 2K on which the electrostatic latent image is formed.

[0044] The image carrier 2K to which the toner has been transferred forms (develops) a black toner image on its surface. Then, the toner image formed on the image carrier 2K is transferred to the intermediate transfer belt 16.

[0045] The drum cleaning device 3K removes the residual toner adhering to the surface of the image carrier 2K after the intermediate transfer process. The removed residual toner is sent by a waste toner transport means to a waste toner storage section in the process unit 1K and collected. In addition, the charge removing device removes the residual charge of the image carrier 2K from which the residual toner has been removed by the cleaning device 3K.

[0046] Similarly, in the process units 1Y, 1M, and 1C of the respective colors, toner images are formed on the image carriers 2Y, 2M, and 2C, and the toner images of the respective colors are transferred onto the intermediate transfer belt 16 so as to be superimposed on each other.

[0047] The intermediate transfer belt 16, onto which the toner images of each color have been transferred so as to be superimposed, travels to the secondary transfer nip between the secondary transfer roller 20 and the drive roller 18. Meanwhile, the pair of registration rollers 250 rotates while nipping the paper that has been abutted against them at a predetermined timing, and transports the paper to the secondary transfer nip of the secondary transfer roller 20 in accordance with the timing at which the toner images formed by superimposing and transferring onto the intermediate transfer belt 16 are suitably transferred. In this way, the toner image on the intermediate transfer belt 16 is transferred to the paper P sent out by the pair of registration rollers 250.

[0048] The paper P onto which the toner image has been transferred is transported to the fixing device 300 via a post-transfer transport path 33. The paper P transported to the fixing device 300 is then sandwiched between a fixing roller 310 and a pressure roller 320, and the unfixed toner image is fixed to the paper P by applying heat and pressure. The paper P onto which the toner image has been fixed is sent from the fixing device 300 to a post-fixing transport path 35.

[0049] 1, at the timing when the paper P is sent out from the fixing device 300, the switching member 42 is in a position that opens the vicinity of the upper end of the post-fixing transport path 35. Then, the paper P sent out from the fixing device 300 is sent out to the paper discharge path 36 via the post-fixing transport path 35. The paper discharge roller pair 37 pinches the paper P sent out to the paper discharge path 36 and rotates to discharge the paper P onto the paper discharge tray 44, thereby completing the single-sided printing.

[0050] Next, a case where double-sided printing is performed will be described. As in the case of single-sided printing, the fixing device 300 sends the paper P to the paper discharge path 36. When double-sided printing is performed, the pair of paper discharge rollers 37 are driven to rotate to transport a part of the paper P outside the image forming apparatus 100.

[0051] 1, the switching member 42 swings about the swing shaft 42a, and closes the upper end of the post-fixing transport path 35. Almost simultaneously with the closing of the upper end of the post-fixing transport path 35, the pair of paper discharge rollers 37 rotates in the direction opposite to the direction in which the paper P is transported out of the image forming apparatus 100, and sends the paper P to the reverse transport path 41.

[0052] The paper P sent to the reversing conveying path 41 passes through a pair of reversing conveying rollers 43 and reaches a pair of registration rollers 250. The pair of registration rollers 250 then determines the optimal timing (synchronization) for transferring the toner image formed on the intermediate transfer belt 16 to the non-transferred surface of the paper P, and sends the paper P to the secondary transfer nip.

[0053] Then, when the paper P passes through the secondary transfer nip, the secondary transfer roller 20 and the drive roller 18 transfer the toner image onto the non-transferred surface (rear surface) of the paper P. Then, the paper P onto which the toner image has been transferred is transported to the fixing device 300 via the post-transfer transport path 33.

[0054] The fixing device 300 sandwiches the conveyed paper P between the fixing roller 310 and the pressure roller 320, and applies heat and pressure to fix the unfixed toner image to the back surface of the paper P. In this way, the paper P with the toner images fixed on both sides is sent from the fixing device 300 to the post-fixing conveyance path 35.

[0055] 1, at the timing when the paper P is sent out from the fixing device 300, the switching member 42 is in a position that opens the vicinity of the upper end of the post-fixing transport path 35. Then, the paper P sent out from the fixing device 300 is sent out to the paper discharge path 36 via the fixing transport path. The paper discharge roller pair 37 pinches the paper P sent out to the paper discharge path 36, and is driven to rotate to discharge the paper onto the paper discharge tray 44, thereby completing the double-sided printing.

[0056] After the toner image on the intermediate transfer belt 16 is transferred to the paper P, residual toner remains on the intermediate transfer belt 16. The belt cleaning device 21 removes this residual toner from the intermediate transfer belt 16. The toner removed from the intermediate transfer belt 16 is transported by the waste toner transport means to the powder container 10 and collected in the powder container 10.

[0057] (First embodiment) Next, a fixing device 300 used in the image forming apparatus 100 according to the first embodiment of the present invention will be described with reference to Figures 2A and 2B. The fixing device 300 is composed of a fixing roller 310 as a heating member incorporating a halogen lamp HL, and a pressure roller 320 as a pressure member in pressure contact with the fixing roller 310. A fixing nip SN is formed between the fixing roller 310 and the pressure roller 320, through which a sheet carrying a toner image passes.

[0058] The fixing device 300 may be of a roller fixing type or a belt fixing type. In either fixing type, when a toner image formed on small size paper P is heated and fixed, the heat of the heater is absorbed by the paper P in the area where the paper P passes, but in the area where the paper P does not pass, the heat of the heater is not absorbed by the paper P, which can cause an overheating. This embodiment appropriately suppresses such an overheating with a simple configuration.

[0059] Thermistors TH1 to TH3 serving as temperature detection members for detecting the surface temperature are disposed adjacent to the surface of the fixing roller 310. The surface temperature of the fixing roller 310 can be detected by these thermistors TH1, TH2, and TH3.

[0060] The central thermistor TH1 is disposed at the longitudinal center of the fixing roller 310. The end thermistors TH2 and TH3 are disposed in non-paper passing portions on the outer sides in the width direction of large size paper. Based on temperature information from thermistors TH1 to TH3, the power supplied to the halogen lamp HL is controlled to suppress a temperature rise in the non-paper passing portions of the fixing roller 310.

[0061] The thermistors TH1 to TH3 can be replaced with a thermistor disposed opposite to the outer circumferential surface of the pressure roller 320. Various types of fixing device 300 are possible, and the fixing device 300 shown in Figures 2A and 2B described above is merely one example.

[0062] (Belt type fixing device) In the first embodiment, the fixing roller 310 is used as the heating member, but it is also possible to use a fixing belt 311 as shown in Fig. 2C instead of the fixing roller 310. The fixing device 300 of the belt fixing method in Fig. 2C is composed of a thin fixing belt 311 with low heat capacity and a pressure roller 320. The fixing belt 311 has a cylindrical body made of polyimide (PI) with an outer diameter of 25 mm and a thickness of 40 to 120 µm, for example.

[0063] In either the roller fixing method of Figures 2A and 2B or the belt fixing method of Figure 2C, when a toner image formed on small-sized paper P is heated and fixed, the heat of the heater is absorbed by the small-sized paper P in areas where the small-sized paper P passes, but in areas where the small-sized paper P does not pass, the heat of the heater is not absorbed by the small-sized paper P, which can result in overheating.

[0064] Pressure roller 320 has an outer diameter of, for example, 25 mm, and is composed of a solid iron core 321, an elastic layer 322 formed on the surface of this core 321, and a release layer 323 formed on the outside of elastic layer 322. Elastic layer 322 is made of silicone rubber, and has a thickness of, for example, 3.5 mm.

[0065] In order to improve releasability, it is desirable to form a release layer 323 made of a fluororesin layer having a thickness of, for example, about 40 μm on the surface of the elastic layer 322. A pressure roller 320 is pressed against the fixing belt 311 by a biasing means.

[0066] A stay 350 and a heater holder 340 are disposed in the axial direction inside the fixing belt 311. The stay 350 is made of a metal channel material, and both ends thereof are supported by both side plates of the fixing device 300. The stay 350 reliably receives the pressing force of the pressure roller 320 to stably form the fixing nip SN.

[0067] The heater holder 340 is for holding a base material 341 of the heater 330 of the fixing device 300, and is supported by a stay 350. The heater holder 340 can be preferably formed of a heat-resistant resin with low thermal conductivity, such as LCP, which reduces heat transfer to the heater holder 340 and enables the fixing belt 311 to be heated efficiently.

[0068] The heater holder 340 is shaped to support only two points near both ends of the substrate 341 in the short side direction in order to avoid contact with the high temperature portion of the substrate 341. This further reduces the amount of heat flowing to the heater holder 340, making it possible to efficiently heat the fixing belt 311.

[0069] A thermistor TH1 serving as a central temperature detection member for detecting the temperatures of heating elements 372-376 of heater 330 (described later) is disposed on the rear surface of base material 341. Thermistor TH1 is pressed against the rear surface of base material 341 by spring 387, thereby enabling accurate detection of the temperatures of heating elements 372-376.

[0070] The temperature of the inner surface of the fixing belt 311 downstream of the fixing nip SN is detected by a thermistor TH2 as a central temperature detection member and a thermistor TH3 as an end temperature detection member. The thermistor TH2 is disposed in the center of the heater 330 in the longitudinal direction, similar to the thermistor TH1. The thermistor TH3 is disposed in an end of the heater 330 in the longitudinal direction (non-paper passing portion).

[0071] Thermistors TH1 and TH2 are located at the center in the width direction of small size paper. Thermistor TH3 is located on the outer side in the width direction of large size paper in a non-paper passing portion. Based on temperature information from thermistors TH1 to TH3, the power supplied to heater 330 is controlled to suppress a temperature rise in the non-paper passing portions of fixing belt 311.

[0072] The thermistors TH1 to TH3 can be replaced with a thermistor disposed facing the outer circumferential surface of pressure roller 320. By disposing the thermistor on the pressure roller 320 side on the outside of fixing belt 311, maintenance of the thermistor becomes easier. Various types of fixing device 300 are possible, and the fixing device in Figures 2A to 2C described above is merely one example.

[0073] (●Heater) 2D shows an example of the aforementioned heater 330, which has three electrodes 370h, 370i, and 370j disposed on both ends of a substrate 341, and seven heating elements 371-377 disposed between the electrodes in the longitudinal direction of the substrate 341. The following three heating patterns can be selected by the method of connecting an AC power source to the electrodes 370h, 370i, and 370j. Heating pattern 1: Only the central heating elements 372 to 376 generate heat (for example, when heating small A4 size paper). Heating pattern 2: All heating elements 371 to 377 generate heat (for example, when heating large size A3 paper) Heating pattern 3: Only the end heating elements 371 and 377 generate heat (for example, when preventing the end temperature from dropping when heating A3 paper)

[0074] Here, the central heating elements 372 to 376 are referred to as central heater H1, and the heating elements 371 and 377 at both ends are referred to as end heaters H2. The central heater H1 and end heater H2 are arranged so as not to overlap with each other when viewed from the short side direction perpendicular to the long side direction of the heater 330.

[0075] The five heating elements 372-376 in the center of the heater 330 in the longitudinal direction are connected in parallel to a first electrode 370h and a second electrode 370i via conductors 370e and 370f having a lower resistance than the heating elements. The two resistance heating elements 371 and 377 at both ends in the longitudinal direction are connected in parallel to a second electrode 370i and a third electrode 370j via conductors 370f and 370g having a lower resistance than the heating elements 371 and 377.

[0076] The second electrode 370i on the right side is always connected to an AC power source, and the first electrode 370h and the third electrode 370j on the left side are selectively connected to the AC power source by switching the switch, thereby allowing the three heating patterns 1 to 3 described above to be selected.

[0077] In heater 330 thus allowing the selection of three heat generation patterns, the longitudinal length of five consecutive heat generation elements 372-376 in the longitudinal center of heater 330 is set to the width of A4 paper, and the longitudinal length of all seven heat generation elements 371-377 including both ends is set to the same as A3 size. Then, by appropriately controlling the heating state of heat generation elements 371-377, A4 size and A3 size paper can be heated uniformly.

[0078] A control method is generally used for controlling the heating of the heating elements 371 to 377, in which the lighting time (lighting duty) of the heating elements within a predetermined control time is made variable to obtain an appropriate amount of heat. The lighting duty is adjusted by controlling the phase of the AC power supply with a triac as a control means. The current becomes zero at a duty ratio of 0%, and the current becomes maximum at a duty ratio of 100%.

[0079] The heating elements 371 to 377 may be made of, for example, PTC elements. The PTC elements are made of a material having a positive temperature coefficient of resistance, and have the characteristic that the resistance value increases as the temperature T increases (the current I decreases, and the heater output decreases). The temperature coefficient of resistance (TCR) may be, for example, 1500 PPM (parts per million).

[0080] Heating elements 371-377 are formed on substrate 341, which is a long and narrow metal thin plate member covered with an insulating material. Low-cost aluminum or stainless steel is preferable as the material for substrate 341. Substrate 341 is not limited to being made of metal, and can be made of ceramics such as alumina or aluminum nitride, or non-metallic materials with excellent heat resistance and insulation properties, such as glass or mica.

[0081] (● Duct configuration) 2A and 2B, a duct 510 is disposed on the opposite side of the pressure roller 320 from the fixing roller 310. Cooling air is blown out through this duct 510 to both ends of the pressure roller 320 in the longitudinal direction.

[0082] The duct 510 has a symmetrical structure, and has one intake port 510a located in the center of the pressure roller 320 in the longitudinal direction, and a pair of left and right air outlets 510b located at both ends of the pressure roller 320 in the longitudinal direction. The downstream side of the intake port 510a branches into two branches leading to the pair of left and right air outlets 510b. A blower fan 530 is disposed in the intake port 510a, and this blower fan 530 introduces outside air into the duct 510, and the air is blown out from the pair of left and right air outlets 510b toward both ends of the pressure roller 320 in the longitudinal direction.

[0083] The pair of left and right air outlets 510b can be provided with air outlet members 550a, 550b as necessary. The air outlet members 550a, 550b adjust the opening area of ​​the air outlet 510b to increase or decrease, and the type of increase or decrease adjustment can be of multiple types as shown in Figures 3A, 3B, 3A', 3B', 4A, 4B, 5A, and 5B described later.

[0084] Duct 510 is disposed so as to be movable in a direction (up and down in Figs. 2A and 2B, left and right in Fig. 2C) transverse to the longitudinal direction of pressure roller 320. The amount of movement of duct 510 can be changed in accordance with paper size information.

[0085] In this embodiment, the duct 510 is disposed so as to be movable in a direction perpendicular to the longitudinal direction of the pressure roller 320, but the movement direction of the duct 510 is not limited to the direction perpendicular to the longitudinal direction. The duct 510 may be moved in an inclined direction that forms a predetermined angle (for example, a predetermined angle between 0° and 10°) with the direction perpendicular to the longitudinal direction of the pressure roller 320.

[0086] Fig. 2A shows a state in which duct 510 is closest to pressure roller 320, and Fig. 2B shows a state in which duct 510 is farthest from pressure roller 320. In Fig. 2A where duct 510 is closest to pressure roller 320, the diffusion range L1 of airflows Wa, Wb emitted from air outlet 510b is narrow in the longitudinal direction. Therefore, the air volume of blower fan 530 is supplied intensively to diffusion range L1 which is narrow in the longitudinal direction.

[0087] When large-sized paper is passed through the fixing nip, the longitudinal range of the non-paper passing portion is narrowed, and the longitudinal range of the end overheating is also narrowed. Therefore, under such printing conditions, as shown in Figure 2A, duct 510 is brought closest to pressure roller 320 and air is blown out in a narrow diffusion range L1 in a concentrated manner. In Figure 2A, the air volume per unit area is increased, so that limited areas at both longitudinal ends of pressure roller 320 can be cooled in a concentrated manner.

[0088] 2B, where the duct 510 is farthest from the pressure roller 320, the diffusion range L2 of the airflows Wa, Wb emitted from the air outlet 510b becomes wider in the longitudinal direction. Therefore, the air volume of the blower fan 530 is dispersed and supplied over the wide diffusion range L2 in the longitudinal direction.

[0089] When small-sized paper is passed through the fixing nip, the longitudinal range of the non-paper passing portion becomes wider, and the longitudinal range of the end overheating also becomes wider. Therefore, under such printing conditions, as shown in FIG. 2B, the duct 510 is set farthest from the pressure roller 320, and air is blown out to a wide diffusion range L2. In this way, as shown in FIG. 2B, it is possible to cool a wider area at both longitudinal ends of the pressure roller 320.

[0090] 2A and 2B, the duct 510 is arranged to be movable in a direction transverse to the longitudinal direction of the pressure roller 320, thereby making it possible to switch the cooling area of ​​the pressure roller 320. Therefore, in response to an excessive temperature rise at the end of the pressure roller 320, the area that needs to be cooled according to the paper size can be effectively cooled with a simple configuration.

[0091] That is, the area that needs to be cooled according to the paper size can be effectively cooled by a simple configuration against excessive temperature rise at the edge. Also, by moving the duct 510 based on the paper size information, it is possible to eliminate the need for multiple temperature detection means such as thermistors and a complex configuration for moving the duct in the longitudinal direction, and cooling according to the paper size can be performed by a simple configuration against excessive temperature rise at the edge.

[0092] (Second embodiment) Next, the cooling structure of the fixing device 300 according to the second embodiment of the present invention will be described with reference to Figs. 3A and 3B. This cooling structure adjusts the vertical width of the air outlet 510b by adjusting the air outlet member 550 (550a, 550b) without changing the longitudinal width of the air outlet 510b. The rest of the structure is the same as that of the first embodiment described above with reference to Figs. 2A and 2B.

[0093] Air outlet members 550 are formed of elongated members with an L-shaped cross section, and are disposed in pairs above and below air outlet 510b. The upper and lower air outlet members 550 are each rotatable about a fulcrum pin 551 whose position is fixed. By rotating air outlet members 550 by a driving means such as a motor, the vertical width of air outlet 510b can be increased or decreased.

[0094] Fig. 3A shows the state where duct 510 is closest to pressure roller 320. At this time, the airflow from air outlet 510b is blown out into a narrow diffusion range L1 in the longitudinal direction like airflows Wa and Wb shown in Fig. 2A. However, the vertical width W1 of air outlet 510b is at its maximum (maximum opening area).

[0095] For this reason, the airflows Wa and Wb cool a wide angle range of the peripheral surface of the pressure roller 320. When a large size sheet is passed through the fixing nip, the longitudinal range in which excessive temperature rise occurs at the end is narrow, so that the duct 510 is placed closest to the pressure roller 320 for cooling, as shown in FIG.

[0096] 3B shows a state in which duct 510 is farthest from pressure roller 320. At this time, the airflow from air outlet 510b is blown out into a wide diffusion range L2 in the longitudinal direction like airflows Wa and Wb shown in FIG. 2B. However, the vertical width W2 of air outlet 510b is at a minimum (minimum opening area).

[0097] Therefore, the air currents Wa and Wb concentrate on cooling a narrow angle range of the circumferential surface of pressure roller 320. When small size paper is passed through the fixing nip, the longitudinal range in which excessive temperature rise occurs at the end is wide, so duct 510 is placed at the furthest distance from pressure roller 320 for cooling, as shown in Fig. 3B. Even when duct 510 is placed at the furthest distance from pressure roller 320, vertical width W2 of air outlet 510b is at its smallest, so the wind speed of air outlet 510b can be increased, thereby increasing the cooling effect.

[0098] The vertical width W2 can be changed according to the paper size, thereby more effectively suppressing the end excessive temperature rise. The vertical width W2 can be changed by controlling the drive amount of the motor that drives the shutter member 550.

[0099] The vertical width of the air outlet 510b gradually narrows as the duct 510 moves away from the pressure roller 320. Therefore, depending on the paper size, air can be blown out from the air outlet 510b with the duct 510 stopped at a predetermined intermediate position between Figures 3A and 3B.

[0100] (Modification of the second embodiment) Next, a modified example of the second embodiment of the present invention will be described with reference to Figures 3A' and 3B'. In this modified example, the air outlet member 550 of Figures 3A and 3B is rotatably disposed at the tip of the duct 510.

[0101] That is, a corner of air outlet member 550 having an L-shaped cross section is rotatably supported by a support shaft 556 provided at the tip of duct 510. A torsion spring wound around support shaft 556 biases air outlet member 550 in the opening direction.

[0102] On the other hand, one end of the air outlet member 550 is connected by a tension spring SP4 to a fixed pin 557 that is fixed in position. The air outlet member 550 is biased in a closing direction by the tension spring SP4.

[0103] 3A', when the duct 510 is closest to the pressure roller 320, the tension spring SP4 remains compressed, so the air outlet member 550 is wide open (maximum opening area) by the biasing force of the torsion spring wound around the support shaft 556. In contrast, when the duct 510 is farthest from the pressure roller 320 as shown in FIG 3B', the tension spring SP4 is stretched, and the biasing force in the closing direction by this tension spring SP4 becomes dominant, so that the vertical width W2 of the air outlet member 550 becomes minimum (minimum opening area).

[0104] For this reason, even if duct 510 is separated from pressure roller 320 as shown in Fig. 3B', airflows Wa, Wb are narrowed by vertical width W2, so it is possible to concentrate cooling on a narrow angular range of the circumferential surface of pressure roller 320. When small size paper is passed through the fixing nip, the longitudinal range in which excessive temperature rise at the ends occurs is wide, so duct 510 is placed as far away from pressure roller 320 as possible for cooling as shown in Fig. 3B'.

[0105] Since the vertical width W2 of the air outlet 510b is at its smallest even when the duct 510 is at the farthest position from the pressure roller 320, the air speed of the air outlet 510b can be increased, thereby enhancing the cooling effect. The vertical width W2 can be changed according to the paper size, thereby more effectively suppressing excessive temperature rise at the end portions.

[0106] The vertical width of the air outlet 510b gradually narrows as the duct 510 moves away from the pressure roller 320 because the tension spring SP4 is stretched. Therefore, air can be blown out from the air outlet 510b with the duct 510 stopped at a predetermined intermediate position between Figures 3A and 3B depending on the paper size.

[0107] (Third embodiment) Next, the cooling structure of the fixing device 300 according to the third embodiment of the present invention will be described with reference to Figs. 4A and 4B. This cooling structure adjusts the longitudinal width of the air outlet 510b without changing the vertical width. The rest of the structure is the same as that of the first embodiment described above with reference to Figs. 2A and 2B.

[0108] The slider members 570a, 570b are formed of U-shaped or bifurcated comb-like members, and are disposed inside the air outlet 510b with the bases (connecting parts) of the slider members 570a, 570b at the center in the longitudinal direction. The longitudinal width of the air outlet 510b can be increased or decreased by sliding the slider members 570a, 570b in the longitudinal direction by a driving means such as a motor in accordance with the paper size.

[0109] 4A shows a state in which duct 510 is closest to pressure roller 320, and slider members 570a and 570b have moved to both ends in the longitudinal direction. At this time, the longitudinal width of air outlet 510b is at its minimum (opening area S1, longitudinal opening width L1).

[0110] 4B shows a state in which duct 510 is farthest from pressure roller 320, and slider members 570a and 570b have moved toward the center in the longitudinal direction as indicated by arrows B and C. At this time, the longitudinal width of air outlet 510b is at its maximum (opening area S2, longitudinal opening width L2).

[0111] The opening areas S1 and S2 and the longitudinal opening widths L1 and L2 can be changed according to the paper size, thereby more effectively preventing excessive temperature rise at the edge. That is, by setting the opening area S1 and the longitudinal opening width L1 for small size paper and the opening area S2 and the longitudinal opening width L2 for large size paper, it is possible to more effectively prevent excessive temperature rise at the edge.

[0112] (Fourth embodiment) Next, the cooling structure of the fixing device 300 according to the third embodiment of the present invention will be described with reference to Figures 5A and 5B. This cooling structure is a type that adjusts both the vertical width and the longitudinal width of the air outlet 510b. The air outlet members 550a and 550b are the same as those described in Figures 3A and 3B. Moreover, the slider members 570a and 570b are the same as those described in Figures 4A and 4B.

[0113] 5A shows the state in which duct 510 is closest to pressure roller 320, and because air outlet members 550a, 550b are fully open, vertical width W1 of air outlet 510b is at its maximum. Also, because slider members 570a, 570b have moved to both ends in the longitudinal direction, the longitudinal width of air outlet 510b is at its minimum (opening area S1).

[0114] 5B shows the state in which duct 510 is farthest from pressure roller 320, and because air outlet members 550a, 550b are narrowed, vertical width W2 of air outlet 510b is at its minimum. Also, slider members 570a, 570b have moved toward the center in the longitudinal direction as shown by arrows B and C, so that the longitudinal width of air outlet 510b is at its maximum (opening area S2).

[0115] The opening areas S1 and S2, longitudinal opening widths L1 and L2, and vertical widths W1 and W2 of the air outlet 510b can be changed according to the paper size, thereby more effectively preventing excessive temperature rise at the end portions. That is, by setting the opening area S1, longitudinal opening width L1, and vertical width W1 for small-sized paper, and the opening area S2, longitudinal opening width L2, and vertical width W2 for large-sized paper, excessive temperature rise at the end portions can be more effectively prevented.

[0116] (● Control of fan speed) The rotation speed of blower fan 530 may be increased or decreased in conjunction with the adjustment of the movement position of duct 510 corresponding to the paper size, and the adjustment of air outlet members 550 (550a, 550b) and slider members 570a, 570b. By combining the configuration of duct 510 and the rotation speed of blower fan 530, it is possible to provide an effective fixing device that suppresses excessive temperature rise at the end portions.

[0117] 6 is a diagram showing the temperature change of the fixing roller 310 when the rotation speed of the blower fan 530 is increased or decreased in response to the printing operation (printing or standby) of the fixing device 300. The temperature of the fixing roller 310 is represented by the detected temperatures of thermistors TH1 and TH2. In order to prevent the end portions of the fixing roller 310 from overheating, the temperature difference ΔT between thermistors TH1 and TH2 is made as small as possible.

[0118] When printing starts, the center temperature TH1 of the fixing roller is printed at the specified temperature. When small size paper is fed, the edge temperature TH2 becomes higher than the center temperature TH1. When the temperature difference between the center temperature TH1 and the edge temperature TH2 becomes ΔT1, the rotation speed of the cooling fan switches from Low to Middle, and when the temperature difference becomes ΔT10, the rotation speed of the cooling fan switches from Middle to High until the edge temperature TH2 drops to the temperature difference ΔT2.

[0119] When the temperature difference becomes ΔT2, the rotation speed of the cooling fan switches from High to Middle. When the printing operation is finished and the temperature difference becomes ΔT1, the rotation speed of the cooling fan switches from Middle to Low and goes into standby mode.

[0120] (● Change type of air outlet) In the first to fourth embodiments described above, the duct 510 is moved toward or away from the pressure roller 320, and the opening area of ​​the air outlet 510b is increased or decreased. However, the present invention can be implemented in other ways. That is, as shown in Fig. 7(a) and (b), the opening area of ​​the air outlet 510b may be changed (opening area CA1, CA2 -> opening area CA3, CA4), the direction of the air outlet of the duct 510 may be changed as shown in Fig. 7(c), or the shape of the air outlet of the duct 510 may be changed as shown in Fig. 7(d).

[0121] In this way, any one of the position, shape, orientation, and opening area of ​​the air outlet can be changed in response to the paper size, or any two or more of the position, shape, orientation, and opening area of ​​the air outlet can be changed in response to the paper size. By making any two or more of the position, shape, orientation, and opening area of ​​the air outlet changeable in response to the paper size as in the latter case, excessive temperature rise at the end of the fixing roller 310 or the pressure roller 320 can be suppressed more effectively than when only one of them is changeable. The position, shape, orientation, and opening area of ​​the air outlet can be changed by using a known slider mechanism, cam mechanism, link mechanism, etc., alone or in combination.

[0122] (Fifth embodiment) Next, a cooling structure of fixing device 300 according to a fifth embodiment of the present invention will be described with reference to Figs. 8A to 8C. In this embodiment, the orientation of air outlet member 550 is changed in the vertical direction in conjunction with the approaching and receding movement of duct 510 relative to pressure roller 320. The vertical width of air outlet 510b is almost the same (W1 ≒ W2) between the orientations of air outlet member 550 in Figs. 8A and 8B.

[0123] 8C, the air outlet members 550 disposed above and below the air outlet 510b are capable of swinging up and down about a fixed fulcrum pin 552. The tips of the air outlet members 550 are connected to each other by a connecting member 554. The lower air outlet member 550 is biased upward by a compression spring SP1.

[0124] 8A, when duct 510 is approaching pressure roller 320, the tip of duct 510 is inserted between air outlet member 550, and air outlet member 550 faces horizontally. Although the biasing force of compression spring SP1 acts on air outlet member 550, the tip of duct 510 interferes with air outlet member 550, so air outlet member 550 cannot tilt upward.

[0125] 8B, when duct 510 moves away from pressure roller 320 in the direction of arrow A, the tip of duct 510 is pulled out from between air outlet member 550. As a result, air outlet member 550 becomes free to swing, and is tilted upward around fulcrum pin 552 by the biasing force of compression spring SP1.

[0126] Therefore, the air blown out from the tip of duct 510 is guided obliquely upward by air outlet member 550, and is blown in a substantially tangential direction against the outer circumferential surface of pressure roller 320. As a result, air is blown over a wide angular range in the circumferential direction of the outer circumferential surface of pressure roller 320, enhancing the cooling effect of non-sheet-passing portions at both ends of pressure roller 320.

[0127] (Sixth embodiment) Next, a cooling structure of a fixing device 300 according to a sixth embodiment of the present invention will be described with reference to Figs. 9A and 9B. In this embodiment, the orientation of the blowout member 550 is changed in the vertical direction in conjunction with the approaching and receding movement of the duct 510 relative to the pressure roller 320. That is, when the duct 510 is approaching the pressure roller 320 as shown in Fig. 9A, the blowout member 550 faces horizontally (vertical width W1), but when the duct 510 moves away from the pressure roller 320 in the direction of arrow A as shown in Fig. 9B, the blowout member 550 opens in the vertical direction by the biasing force of the tension spring SP2 (vertical width W2).

[0128] Air outlet members 550 disposed above and below air outlet 510b are capable of swinging up and down about fulcrum pins 553 that are fixed in position. A tension spring SP2 is connected to the tip of air outlet member 550. In the state of FIG. 9A, even if air outlet member 550 tries to open due to the biasing force of tension spring SP2, air outlet member 550 does not open because the tip of duct 510 interferes with air outlet member 550.

[0129] 9B, when duct 510 moves away from pressure roller 320 as indicated by arrow A, air outlet member 550 becomes free to swing and opens outward due to the biasing force of tension spring SP2. Therefore, air blown out from the tip of duct 510 is blown from vertical width W2 over a wide angular range on the outer circumferential surface of pressure roller 320, enhancing the cooling effect on non-paper passing portions at both ends of pressure roller 320.

[0130] (Seventh embodiment) Next, the cooling structure of the fixing device 300 according to the seventh embodiment of the present invention will be described with reference to Figs. 10A and 10B. In this embodiment, the approach and separation of the duct 510 to the pressure roller 320 is performed according to the paper size. That is, for example, when a large size paper is passed, the end excessive temperature rise occurs in a relatively narrow range at both ends in the longitudinal direction of the pressure roller 320, so the duct 510 is brought close to the pressure roller 320 as shown in Fig. 10A to blow out air. On the other hand, when a small size paper is passed, the end excessive temperature rise range expands to a wide range at both ends in the longitudinal direction of the pressure roller 320, so the duct 510 is moved away from the pressure roller 320 as shown in Fig. 10B to blow out air.

[0131] A pair of left and right air outlet members 550 are disposed rotatably about support shafts 555 near left and right air outlets 510b through which air is blown out from duct 510. The air outlet members 550 are biased by tension springs SP3 in a direction in which they open outward.

[0132] 10A, when the duct 510 is approaching the pressure roller 320, the outer surfaces of the pair of left and right air outlet members 550 are pressed in a closing direction by the inner surface of the duct 510, so the left and right air outlet members 550 face each other in a substantially parallel state. Therefore, air can be blown out within an appropriate range to counter the end overheating that occurs in a relatively narrow range at both longitudinal ends of the pressure roller 320 when large size paper is passed through.

[0133] 10B, when the duct 510 moves away from the pressure roller 320, the pair of left and right air outlet members 550 are biased outward by the tension spring SP3 and open flared. Therefore, air can be blown out within an appropriate range to cope with the end overheating that occurs over a wide range at both longitudinal ends of the pressure roller 320 when small size paper is passed through.

[0134] (Modification of the seventh embodiment) 10A and 10B, the air outlet member 550 in Figures 3A and 3B may be disposed. That is, the air outlet members 550 may be disposed above, below, left and right of the air outlet.

[0135] 10B, the opening of the air outlet member 550 can be narrowed in the vertical direction and widened in the longitudinal direction as the duct 510 moves away from the pressure roller 320. Here, the "vertical direction" refers to a direction perpendicular to both the longitudinal direction of the pressure roller 320 and the moving direction of the duct 510.

[0136] In this way, with the duct 510 separated from the pressure roller 320, the strong airflows Wa, Wb can be applied to both ends of the pressure roller 320 in the longitudinal direction over a wide range of the pressure roller 320. Therefore, excessive temperature rise at the ends of the fixing roller 310 or the pressure roller 320 can be suppressed more effectively than in the case of FIG. 10B.

[0137] Although the present invention has been specifically described based on the embodiment, it goes without saying that the present invention is not limited to the above embodiment and can be modified in various ways within the scope of the technical ideas described in the claims. For example, instead of cooling the pressure roller 320 with air from the duct 510, the fixing roller 310 may be cooled directly. Also, the halogen lamp HL for heating the fixing roller 310 can be replaced with other heating elements such as a heater using a PTC element or a ceramic heater. [Explanation of symbols]

[0138] 100: Image forming apparatus 300: Fixing device 310: Fixing roller (heating member) 311: Fixing belt (heating member) 320: Pressure roller (pressure member) 330: Heater 340: Heater holder 350: Stay 510: Duct 510a: Intake port 510b: Air outlet 530: Blower fan 550, 550a, 550b: Air outlet members 551 to 553: Pivot pins 554: Connecting material 555, 556: Support shaft 557: Fixing pin 570a, 570b: Slider member SN: Fixing nip (nip part) SP1: Compression spring SP2~SP4: Tension springs TH1~TH3: Thermistors [Prior art documents] [Patent documents]

[0139] [Patent Document 1] JP 2006-119259 A [Patent Document 2] JP 2003-66762 A

Claims

1. An image forming apparatus including a fixing device in which a heating member having a longitudinal direction and a pressure member are in pressure contact with each other to form a nip portion, heat is transferred from the heating member to a sheet member passing through the nip portion, and a toner image carried on the sheet member is heated and fixed, an image forming apparatus comprising: a duct for blowing air to both ends in a longitudinal direction of said heating member or said pressure member, said duct being disposed so as to be movable in a direction transverse to said longitudinal direction;

2. 2. The image forming apparatus according to claim 1, wherein at least one of a position, a shape, a direction and an opening area of ​​an air outlet for blowing out air from said duct is changeable.

3. 2. The image forming apparatus according to claim 1, wherein at least two of the position, shape, direction and opening area of ​​the air outlet for blowing out the air from the duct are changeable.

4. 4. The image forming apparatus according to claim 2, wherein the moving position of said duct and the position, shape, direction and opening area of ​​said air outlet are changeable in accordance with the size of said sheet member.

5. 5. The image forming apparatus according to claim 2, wherein the position, shape, direction and opening area of ​​the air outlet are changeable in conjunction with the movement of the duct.

6. An image forming apparatus including a fixing device in which a heating member having a longitudinal direction and a pressure member are in pressure contact with each other to form a nip portion, heat is transferred from the heating member to a sheet member passing through the nip portion, and a toner image carried on the sheet member is heated and fixed, an image forming apparatus comprising: a duct for blowing air toward both longitudinal ends of the heating member or the pressure applying member, the duct being arranged so as to be movable in a direction transverse to the longitudinal direction; and an opening of an outlet for blowing air from the duct gradually narrowing as the duct moves away from the heating member or the pressure applying member in the direction transverse to the longitudinal direction.

7. An image forming apparatus including a fixing device in which a heating member having a longitudinal direction and a pressure member are in pressure contact with each other to form a nip portion, heat is transferred from the heating member to a sheet member passing through the nip portion, and a toner image carried on the sheet member is heated and fixed, an image forming apparatus comprising: a duct which blows air toward both longitudinal ends of the heating member or the pressure applying member, the duct being arranged so as to be movable in a direction transverse to the longitudinal direction; and an opening of an outlet which blows air from the duct gradually narrows in the longitudinal direction and in a direction perpendicular to the direction of movement of the duct, and widens in the longitudinal direction as the duct moves away from the heating member or the pressure applying member in the direction transverse to the longitudinal direction.

Images