Image forming apparatus

Abstract

To provide a configuration that can prevent the temperature balance from being lost between the ends in a width direction of a fixing film, even if the configuration is to move a fixing device in a reciprocating manner.SOLUTION: A fixing device forms a nip part with a fixing film and a pressure roller, and sandwiches and conveys a recording material at the nip part to fix a toner image to the recording material. An image forming apparatus comprises a fan that blows air toward a first area on a first end in a width direction of the fixing film, the other fan that blows air toward a second area on a second end in the width direction of the fixing film, and a reciprocation mechanism that moves the fixing device in the width direction. A control circuit unit changes at least one of the volumes of air from the two fans according to the position in the width direction of the fixing device.SELECTED DRAWING: Figure 12

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus such as a copier, a printer, a facsimile, or a multifunction machine having a plurality of these functions. [Background technology]

[0002] The image forming apparatus has a fixing device that heats a toner image carried on a recording material to fix the toner image to the recording material. Such a fixing device fixes the toner image to the recording material by conveying the recording material carrying the toner image in a pressurized and heated state in a nip portion formed between a first rotating body such as a fixing film and a second rotating body such as a pressure roller.

[0003] Furthermore, as such a fixing device, a configuration has been proposed in which the fixing device is moved back and forth in a width direction that intersects with the conveying direction of the recording material in order to prevent the first rotating body from being locally damaged (for example, Patent Document 1).

[0004] Furthermore, as a fixing device, a configuration has been proposed in which a fan is used to blow air onto the area on the end side of the first rotating body to cool it in order to prevent the non-passage area, where the recording material does not pass, from rising in temperature (non-passage area temperature rise) (for example, Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2000-194216 A [Patent Document 2] JP 2013-134421 A Summary of the Invention [Problem to be solved by the invention]

[0006] As described in Patent Document 1, in the case of a configuration in which the fixing device reciprocates (performs a reciprocating motion), the temperature balance at both ends in the width direction of the first rotating body is lost before and after the reciprocating motion of the fixing device. This is because the positional relationship in the width direction between the heater that heats the first rotating body and the recording material passing through the nip portion changes before and after the reciprocating motion. For example, when the fixing device moves to one side from the center position in the width direction due to the reciprocating motion, the recording material passes through the other side of the nip portion from the center position. For this reason, the non-passing portion temperature rise is likely to occur on one side of the first rotating body, and the non-passing portion temperature rise is unlikely to occur on the other side.

[0007] Here, it is conceivable to combine the configuration for cooling the end of the first rotor to suppress the temperature rise in the non-passage section as described in Patent Document 2 with the configuration for performing the reciprocating operation as described above. However, in the case of a conventional configuration for blowing air toward the end of the first rotor to suppress the temperature rise in the non-passage section, the amount of air blown to each end of the first rotor is the same. Therefore, even if such a configuration is combined, it is not possible to improve the imbalance in temperature at both ends of the width direction of the first rotor caused by the reciprocating operation.

[0008] An object of the present invention is to provide a configuration that can prevent the temperature balance at the ends in the width direction of a first rotating body from being lost even when the fixing device is configured to reciprocate. [Means for solving the problem]

[0009] The image forming apparatus of the present invention is characterized in that it comprises a fixing device having a first rotating body, a second rotating body that sandwiches and transports a recording material carrying a toner image between the first rotating body to form a nip portion in which the toner image is fixed to the recording material, and a heating section that heats the first rotating body; a first air blowing section that blows air toward a first region of the first rotating body that is closer to the first end than the center of the first rotating body in a width direction that intersects with the transport direction of the recording material; a second air blowing section that blows air toward a second region of the first rotating body that is closer to the second end than the center of the first rotating body in the width direction; a reciprocating movement section that moves the fixing device back and forth in the width direction; and a control section that changes the air volume of at least one of the first air blowing section and the second air blowing section depending on the position of the fixing device in the width direction.

[0010] The image forming apparatus of the present invention further includes a fixing device having a first rotating body, a second rotating body that sandwiches and conveys a recording material carrying a toner image between the first rotating body and a nip portion that fixes the toner image to the recording material, and a heating portion that heats the first rotating body, a blowing portion that blows air, a first duct that guides the air blown from the blowing portion toward a first region of the first rotating body that is closer to a first end portion than a center portion of the first rotating body in a width direction that intersects with a conveying direction of the recording material, a first shutter that is capable of changing an opening width of the first duct, and a fixing device that blows air from the blowing portion. the second duct configured to guide the air sent from the first rotating body toward a second region of the first rotating body which is located on the second end side opposite the first end from the central portion of the first rotating body; a second shutter configured to change the opening width of the second duct; a reciprocating movement unit configured to reciprocate the fixing device in the width direction; and a control unit configured to change at least one of the opening width of the first duct formed by the first shutter and the opening width of the second duct formed by the second shutter depending on the position of the fixing device in the width direction.

[0011] The image forming apparatus of the present invention further includes a fixing device including a first rotating body, a second rotating body that forms a nip portion between the first rotating body and the second rotating body to sandwich and transport a recording material carrying a toner image thereon, and fixes the toner image onto the recording material, a heating portion that heats the first rotating body, a first temperature detection portion that detects the temperature of the first rotating body on a first end side of the center of the first rotating body in a width direction that intersects with a transport direction of the recording material, and a second temperature detection portion that detects the temperature of the first rotating body on a second end side that is opposite to the first end side of the center in the width direction, and a fixing device including a first region of the first rotating body that is on the first end side of the center in the width direction. the fixing device includes a first air blowing unit that blows air toward the second end portion of the first rotating body, a second air blowing unit that blows air toward a second region of the first rotating body that is closer to the second end portion than the center portion in the width direction, a reciprocating movement unit that moves the fixing device back and forth in the width direction, and a control unit that controls the driving and stopping of the first air blowing unit based on the temperature detected by the first temperature detection unit and the driving and stopping of the second air blowing unit based on the temperature detected by the second temperature detection unit, wherein the control unit changes at least one of the temperature at which the first air blowing unit starts to drive and the temperature at which the second air blowing unit starts to drive depending on the position of the fixing device in the width direction. Effect of the Invention

[0012] According to the present invention, even if the fixing device is configured to reciprocate, it is possible to prevent the temperature balance at the ends in the width direction of the first rotating body from being lost. [Brief description of the drawings]

[0013] [Figure 1] 1 is a schematic cross-sectional view of an image forming apparatus according to a first embodiment. [Diagram 2] 1 is a cross-sectional view showing a schematic configuration of a fixing device according to a first embodiment. [Diagram 3] 1 is a vertical cross-sectional view showing a schematic configuration of a fixing device according to a first embodiment. [Figure 4] FIG. 2 is a schematic cross-sectional view of the fixing film according to the first embodiment. [Diagram 5]1A and 1B are schematic diagrams of a reciprocating mechanism according to a first embodiment, as viewed from the side and above, respectively. [Figure 6] 5 is a graph showing the relationship between the phase of the reciprocating cam and the amount of reciprocation according to the first embodiment. [Figure 7] FIG. 2 is a cross-sectional view showing a schematic configuration of a fixing device and a cooling mechanism according to the first embodiment. [Figure 8] FIG. 2 is a diagram showing a drive configuration of a shutter according to the first embodiment. [Figure 9] FIG. 2 is a schematic plan view of the shutter drive configuration according to the first embodiment, showing the shutter in a fully closed state. [Figure 10] FIG. 2 is a schematic plan view of the shutter drive configuration in the first embodiment, showing a state in which the shutter is open. [Figure 11] 2 is a control block diagram of a main part of the image forming apparatus according to the first embodiment. FIG. [Figure 12] 5 is a flowchart of control regarding reciprocating operation and fan air volume correction according to the first embodiment. [Figure 13] 6 is a graph showing a temperature transition of a fixing film according to a comparative example. [Figure 14] 6 is a graph showing a temperature transition of a fixing film according to an embodiment. [Figure 15] FIG. 11 is a control block diagram of a main part of an image forming apparatus according to a second embodiment. [Figure 16] 13 is a schematic diagram showing the relationship between the arrangement of a thermistor and an opening of a duct in a fixing device according to a second embodiment. FIG. [Figure 17] FIG. 11 is a plan view showing a drive configuration of the shutter according to the second embodiment. [Figure 18] 10 is a flowchart of control regarding reciprocating operation and aperture width correction by a shutter according to a second embodiment. [Figure 19] 13 is a flowchart of control regarding reciprocating operation and fan drive start temperature width correction according to the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] <First embodiment> The first embodiment will be described with reference to Figures 1 to 14. First, the schematic configuration of an image forming apparatus according to the present embodiment will be described with reference to Figure 1.

[0015] [Image forming equipment] The image forming apparatus 1 is, for example, a printer, and after a toner image formed on a photosensitive drum 11 is transferred to a recording material P in an image forming section 10, a fixing device 40 fixes the image to the recording material P. As shown in FIG. 1, the image forming apparatus 1 includes an image forming section (image forming station) 10 that forms toner images of the colors Y (yellow), M (magenta), C (cyan), and Bk (black). The image forming section 10 includes photosensitive drums 11 as four image carriers corresponding to the colors Y, M, C, and Bk in order from the left side of FIG. 1. The photosensitive drum 11, which is a cylindrical photosensitive body, is rotated in the direction of the arrow by a driving source (not shown) such as a motor.

[0016] Around each photosensitive drum 11, there are disposed a charger 12, an exposure device 13, a developing device 14, a primary transfer blade 17, and a cleaner 15. The procedure for forming a Bk toner image will be described below, but the procedures for forming toner images of other colors are similar. The recording material P is, for example, a sheet such as paper or a plastic sheet.

[0017] First, a procedure for forming a toner image on a recording material P will be described. The surface of the photosensitive drum 11 is uniformly charged by the charger 12, and then exposed by the exposure device 13 in accordance with image information. As a result, an electrostatic latent image is formed on the photosensitive drum 11. Then, the developing device 14 develops toner onto the electrostatic latent image obtained by the exposure device 13, forming a toner image on the photosensitive drum 11. At this time, similar processes are performed for the other colors.

[0018] The toner images on the photosensitive drums 11 are sequentially superimposed and primarily transferred onto the intermediate transfer belt 31 serving as an intermediate transfer body by the primary transfer blade 17. As a result, a full-color toner image is formed on the intermediate transfer belt 31. Any toner remaining on the photosensitive drums 11 after the primary transfer is removed by the cleaner 15. In this way, the photosensitive drums 11 are ready for the next image formation.

[0019] Meanwhile, the recording material P contained in the feeding cassette 20 or the recording material P placed on the multi-feed tray 25 is fed one by one by a feeding mechanism (not shown) and sent to the registration roller pair 23. The registration roller pair 23 temporarily stops the recording material P, straightens the direction of the recording material P if it is skewed with respect to the conveying direction, and feeds the recording material P between the intermediate transfer belt 31 and the secondary transfer roller 35 in synchronization with the toner image on the intermediate transfer belt 31. The secondary transfer roller 35 secondarily transfers the toner image on the intermediate transfer belt 31 to the recording material P.

[0020] The recording material P onto which the toner image has been transferred is transported to the fixing device 40, where a permanently fixed toner image is formed on the recording material P by heat and pressure processing. The recording material P that has passed through the fixing device 40 is discharged to the discharge tray 26a or 26b by the discharge rollers 43a, 43b. In the case of the double-sided printing mode, the recording material P discharged by the discharge rollers 43a, 43b is switched back and transported to the double-sided transport path 27, and is transported again to the registration roller pair 23. Then, in the same manner as described above, a toner image is formed on the back side of the recording material P.

[0021] [Fixing device] Next, the fixing device 40 will be described with reference to Fig. 2 to Fig. 4. The fixing device 40 includes a film unit 60 that heats the toner image on the recording material P, and a pressure roller 70. The film unit 60 includes a fixing film 603 serving as a first rotating body and an endless fixing belt, and a heater 600 serving as a heating section. The heater 600 heats the fixing film 603. That is, the film unit 60 is configured to heat the flexible, thin fixing film 603 by the heater 600 that comes into contact with the inner surface.

[0022] The pressure roller 70 as the second rotating body sandwiches and conveys the recording material P carrying the toner image between itself and the fixing film 603 to form a nip portion N where the toner image is fixed to the recording material. That is, as shown in Fig. 2, the fixing film 603 forms the nip portion N by pressing the heater 600 against the pressure roller 70 via the fixing film 603, and sandwiches and conveys the recording material P fed to the nip portion N. At this time, heat generated by the heater 600 is applied to the recording material P via the fixing film 603, and the toner image T on the recording material P is melted and fixed to the recording material P.

[0023] The film unit 60 is a unit for applying heat and pressure to the toner image on the recording material P, and is disposed parallel to the pressure roller 70 . The film unit 60 comprises a heater 600 , a heater holder 601 , a support stay 602 , and a fixing film 603 .

[0024] The fixing film 603 is pressed against the pressure roller 70 so that the nip portion N has a predetermined width. The heater 600 includes a substrate 610 and a resistance heating element 620 on the substrate 610, and is fixed to a recess in the lower surface of the heater holder 601. In this embodiment, the heating element 620 is provided on the back side of the substrate 610 (the side that does not come into contact with the fixing film 603), but the present invention is not limited to this, and the heating element may be provided on the front side (the side that comes into contact with the fixing film 603).

[0025] A semi-solid lubricant (hereinafter, grease) made of a solid component (compound) and a base oil component (oil) is applied to the surface of the substrate 610 in order to reduce the friction load between the fixing film 603 and the heater 600, and ensures the sliding properties between the heater 600 and the fixing film 603, and between the heater holder 601 and the fixing film 603. Examples of the grease compound include solid lubricants such as graphite and molybdenum disulfide, metal oxides such as zinc oxide and silica, and fluororesins such as polytetrafluoroethylene (PTFE). Examples of the grease oil include heat-resistant polymeric resin oils such as silicone oil and fluorosilicone oil. In this embodiment, grease using PTFE powder fine particles (particle size 3 μm) as the compound and fluorosilicone oil as the oil is used.

[0026] The fixing film 603 is a cylindrical film for applying heat and pressure to the toner image on the recording material at the nip portion N. FIG. 4 shows the layer structure of the fixing film 603. In this embodiment, an elastic layer 603b and a release layer 603c are provided on a substrate 603a, and an inner surface sliding layer 603d is provided on the inner surface of the substrate 603a. Specifically, a cylindrical member made of a nickel alloy having an outer diameter of 30 mm, a length (the length in the rotation axis direction and longitudinal direction of the pressure roller 70) of 340 mm, and a thickness of 30 μm is used as the substrate 603a. Furthermore, a silicone rubber layer having a thickness of 400 μm is formed as the elastic layer 603b on the substrate 603a, and a fluorine resin tube having a thickness of about 20 μm is further coated on the elastic layer 603b as the release layer 603c. Furthermore, a polyimide layer (PI layer) having a thickness of about 10 μm is used as the inner surface sliding layer 603d.

[0027] The heater holder 601 (hereinafter, holder 601) is a member that holds the heater 600 pressed against the fixing film 603. The holder 601 has a semicircular cross-sectional shape and has a function of regulating the rotation orbit of the fixing film 603. The heater holder 601 is made of a highly heat-resistant resin or the like, and in this embodiment, Zenite 7755 (product name) manufactured by DuPont is used.

[0028] The support stay 602 is a member that supports the heater 600 via the heater holder 601. The support stay 602 is desirably made of a material that is not easily bent even when a large load is applied, and in this embodiment, stainless steel (SUS304) is used.

[0029] As shown in FIG. 3, the support stay 602 is supported by flanges 411 at both ends in the longitudinal direction. The flanges 411 regulate the longitudinal movement and circumferential shape of the fixing film 603. The flanges 411 are made of a heat-resistant resin, and polyphenylene sulfide (PPS) is used in this embodiment. A pressure spring 415 is provided in a compressed state between the flange 411 and the pressure arm 414. With the above configuration, the elastic force of the pressure spring 415 is transmitted to the heater 600 via the flange 411 and the support stay 602. Then, the fixing film 603 is pressed against the pressure roller 70 with a predetermined pressing force, and a nip portion N with a predetermined width is formed. In this embodiment, the pressure force is about 156.8 N at one end, and the total pressure force is about 313.6 N (32 kgf).

[0030] The connector 500 is a power supply member that is electrically connected to the heater 600 in order to apply a voltage to the heater 600, and is detachably attached to one end of the heater 600 in the longitudinal direction.

[0031] As shown in FIG. 2, the pressure roller 70 is a member that forms a nip portion N by being pressed by the film unit 60. The pressure roller 70 has a multi-layer structure in which an elastic layer 72 is provided on a metal core 71, and a release layer 73 is further provided on the elastic layer 72. The core 71 can be made of stainless steel (SUS), sulfur and sulfur composite free-cutting steel material (SUM), or aluminum. The elastic layer 72 can be made of silicone rubber, sponge rubber, or elastic foam rubber. The release layer 73 can be made of a fluororesin material such as tetrafluoroethylene-perfluoroalkylvinylether copolymer (PFA). The pressure roller 70 of this embodiment is made of a stainless steel core 71, a silicone rubber elastic layer 72, and a PFA tube release layer 73, and has an outer diameter of about 25 mm and a longitudinal length of the elastic layer of 330 mm.

[0032] As shown in Fig. 3, the core metal 71 of the pressure roller 70 is rotatably held by the side plate 41 constituting the frame of the fixing device 40 via bearings 42a and 42b, and a gear G is provided at one end of the core metal 71 to transmit the driving force of the fixing drive motor M1 to the core metal 71. As shown in Fig. 2, the pressure roller 70 driven by the fixing drive motor M1 is driven to rotate in the direction of the arrow, and transmits the driving force to the fixing film 603 at the nip portion N to rotate it. In this embodiment, the fixing drive motor M1 is controlled by a control circuit unit 90 (see Fig. 11 described later) so that the surface speed of the pressure roller 70 is 200 mm / sec.

[0033] The thermistor (TH) 630, which is a temperature detection means shown in FIG. 2, is provided on the rear side of the heater 600 and is a temperature sensor that detects the temperature of the heater 600. The thermistor 630 is connected to the control circuit unit 90 via an A / D converter and transmits an output corresponding to the detected temperature to the control circuit unit 90. The control circuit unit 90 is a circuit equipped with a CPU that performs calculations associated with various controls and a non-volatile medium such as a ROM. This ROM stores programs, and the CPU reads and executes the programs to execute various controls. The control circuit unit 90 is electrically connected to a power source so as to control the power supply. In addition, the control circuit unit 90 reflects the temperature information acquired from the thermistor 630 in the power supply power supply control, thereby controlling the power supplied to the heater 600. In this embodiment, a method is used in which the amount of heat generated by the heater 600 is adjusted by performing wave number control or phase control on the power supply output, and the heater 600 is maintained at a predetermined temperature when fixing the toner on the recording material.

[0034] [Reciprocating mechanism] Next, the reciprocating mechanism 700 of this embodiment will be described. The surface layer of the fixing film 603 is made of soft resin with relatively good releasability, such as PFA or PTFE, in order to prevent toner from adhering to the recording material. Therefore, when a recording material such as paper passes through the nip portion N, the surface of the fixing film 603 is easily scratched in the rotation direction (circumferential direction) by the paper edge that occurs at the cut edge of the paper when the paper is cut. This scratch (called paper edge scratch) tends to become deeper and larger as the recording material repeatedly passes the same part of the fixing film 603. That is, the surface of the fixing film 603 is scratched locally.

[0035] If deep and large scratches occur on the edge of the paper on the surface of the fixing film 603, when a recording material of the maximum size width passes through the nip portion N in the width direction intersecting the transport direction of the recording material, the position of the scratches may overlap with the image area of ​​the recording material, which may result in streak-like image defects on the recording material after fixing.

[0036] Therefore, in this embodiment, in order to disperse the paper edge scratches in the width direction and prevent localized deep and large scratches from occurring on the surface of the fixing film 603, a reciprocating mechanism 700 is provided as a reciprocating movement unit that reciprocates (reciprocating operation) the fixing device 40 in the width direction. The reciprocating mechanism 700 will be described with reference to Figures 5(a) and (b). Figure 5(a) shows a side view of the reciprocating mechanism 700, and Figure 5(b) shows a top view of the reciprocating mechanism 700.

[0037] In this embodiment, the fixing device 40 is supported by rollers 706, and moves on a slider 704 provided on the main body of the image forming apparatus 1 as the rollers 706 rotate, so that the fixing device 40 can reciprocate in the width direction.

[0038] The reciprocating mechanism 700 includes a reciprocating cam 703 and a reciprocating motor M2. A protrusion 40a that fits into a groove 703a of the reciprocating cam 703 is provided on a side plate of the fixing device 40. The reciprocating cam 703 is fixed to the main body of the image forming apparatus 1 so as to be rotatable by the reciprocating motor M2. The reciprocating motor M2 is a stepping motor, and controls the rotation of the reciprocating cam 703. The reciprocating cam 703 is formed in a cylindrical shape having a groove 703a on its outer circumferential surface. The groove 703a is formed in a shape that displaces the protrusion 40a that fits into the reciprocating cam 703 in the axial direction (width direction) as it advances in the circumferential direction, specifically in a substantially V-shape as shown in the figure.

[0039] When the reciprocating cam 703 rotates, the protrusion 40a fitted in the groove 703a moves along the groove 703a in the axial direction of the reciprocating cam 703. That is, as the reciprocating cam 703 fixed to the image forming apparatus 1 rotates, the protrusion 40a fixed to the fixing device 40 moves in the rotation axis direction of the reciprocating cam 703. This allows the recording material P conveyed by the image forming apparatus 1 and the fixing device 40 to move relatively in the width direction.

[0040] As a result, the end of the recording material P is prevented from repeatedly passing over one spot on the surface of the fixing film 603 (or the pressure roller 70), and the progress of wear caused by contact between the fixing film 603 (or the pressure roller 70) and the end of the recording material can be delayed. In this embodiment, as shown in FIG. 6, the groove 703a of the reciprocating cam 703 is formed so that the fixing device 40 reciprocates in a range of 3 mm in the width direction in half a rotation of the reciprocating cam 703. FIG. 6 shows the relationship between the rotation angle (phase: deg) of the reciprocating cam 703 and the width-direction movement amount (reciprocation amount: mm) of the fixing device 40. The position of the reciprocation amount of 0 mm is set as the home position, and specifically, the home position is determined by a rotation phase detection sensor (not shown) of the reciprocating cam 703.

[0041] 6, it is possible to periodically shift the relative position of the fixing device 40 with respect to the discharge rollers 43a and 43b in the width direction by rotating the reciprocating cam 703. Note that in the case of the recording material P having the maximum size width on which an image can be formed, a recording material having an even larger size width does not pass through the nip portion N, so the effect of scratches on the paper edge does not become apparent.

[0042] In this embodiment, when forming an image on a recording material P of maximum width, the reciprocating operation is stopped at the position indicated by symbol b in Fig. 6, thereby reducing the widthwise space, including the reciprocating amount of the fixing device 40, that needs to be secured within the main body of the image forming apparatus 1. The position indicated by symbol b in Fig. 6 is the position where the center in the widthwise direction of the nip portion N coincides with the center in the widthwise direction of the discharge rollers 43a, 43b (referred to as the reciprocating center).

[0043] [Cooling mechanism] Next, the cooling mechanism 800 of this embodiment will be described with reference to Fig. 7. It is known that in a fixing device, when recording materials (small-sized recording materials) having a smaller width than a recording material (maximum-sized recording material) having a maximum width passing through the nip portion N in a width direction perpendicular to the conveying direction of the recording material are successively passed through the nip portion N, a problem of temperature rise in non-passing portions occurs.

[0044] A more specific explanation will be given. When a maximum-sized recording material is passed through the nip portion N to fix a toner image onto the recording material, the surfaces of the fixing film and the pressure roller have a substantially uniform temperature distribution across the entire fixing area in the width direction. However, when small-sized recording materials are continuously fixed, the surface temperatures of the non-passage areas of the fixing film and the pressure roller, where the recording material does not pass, rise excessively. This is because, when small-sized recording materials are continuously passed through the nip portion N, the non-passage areas where the recording material does not pass do not absorb heat, and heat is partially stored in those areas.

[0045] If the temperature of the non-passing area rises due to successive small-sized recording materials passing through the nip N, when larger-sized recording materials, including the largest-sized recording materials, are passed through the nip N in the next job, these recording materials will pass through the non-passing area for small-sized recording materials. At this time, if the non-passing area exceeds the optimum fixing temperature, the toner will melt excessively, and some of it will remain on the fixing film and be fixed onto the recording material one revolution later. This causes an image defect known as high-temperature offset.

[0046] Furthermore, if there is temperature unevenness in the longitudinal direction of the non-passage area, uneven gloss will occur in the image. Furthermore, if the temperature rise reaches a high temperature, control may be performed to suppress the temperature rise in the non-passage area by increasing the interval between recording materials that continuously pass through the nip portion N, in which case productivity will decrease. The temperature rise in the non-passage area increases under conditions in which the amount of heat absorbed by the recording material increases, and this applies, for example, when the number of sheets processed per unit time (productivity) is large, or when the weight per unit area of ​​the recording material is large (so-called thick paper).

[0047] In this embodiment, a cooling mechanism 800 is provided to suppress the temperature rise of the non-passing portion of the fixing film 603, which occurs when small-sized recording materials are continuously fixed, by cooling (air blowing). As shown in FIG. 7, the cooling mechanism 800 has a fan 44a as a first air blowing section, a fan 44b as a second air blowing section, a duct 45a that guides the air of the fan 44a, and a duct 45b that guides the air of the fan 44b. The ducts 45a and 45b have openings 46a and 46b, respectively, and the openings 46a and 46b are provided at positions facing the first and second regions on both ends of the fixing film 603, which become non-passing regions when small-sized recording materials are fixed. The air of the fans 44a and 44b is guided to the first and second regions of the fixing film 603 through the openings 46a and 46b.

[0048] That is, the fan 44a blows air through the duct 45a toward a first region of the fixing film 603 that is closer to the first end than the center of the fixing film 603 in the width direction intersecting with the conveying direction of the recording material. The fan 44b blows air through the duct 45b toward a second region of the fixing film 603 that is closer to the second end opposite the first end than the center of the fixing film 603 in the width direction. Here, the first and second regions correspond to regions on both sides in the width direction of the region through which the minimum-sized recording material passes when the minimum-sized recording material passes through the fixing nip N, in other words, regions through which the minimum-sized recording material does not pass.

[0049] The cooling mechanism 800 also has shutters 47a, 47b as adjustment members that adjust the opening width of the openings 46a, 46b according to the width of the recording material being used, and a shutter drive unit 48 (FIG. 8) that drives the shutters 47a, 47b. The shutter 47a as the first shutter can change the opening width of the opening 46a of the duct 45a as the first duct. The shutter 47b as the second shutter can change the opening width of the opening 46b of the duct 45b as the second duct.

[0050] The fans 44a, 44b, the ducts 45a, 45b, the openings 46a, 46b, and the shutters 47a, 47b are arranged symmetrically in the longitudinal direction (width direction) of the fixing film 603. In this embodiment, axial fans are used as the fans 44a, 44b, but centrifugal fans such as sirocco fans may also be used.

[0051] The operation of the fans 44a and 44b is performed when the temperature of the thermistor (temperature detector) 631 in FIG. 9 exceeds a predetermined temperature. The thermistor 631 as a temperature detector for detecting the temperature of the first rotating body is disposed inside the fixing film 603, and for example, abuts on or is close to the inner circumferential surface of the fixing film 603 closer to the end than the center in the width direction, and detects the temperature of the fixing film 603. The thermistor 631 abuts on or is close to the inner circumferential surface of the fixing film 603 corresponding to the first region or the second region. In FIG. 9, the thermistor 631 is disposed near the end of the second region on the far side of the fixing film 603, and detects the temperature of the fixing film 603 in this region. The control circuit unit 90 controls the driving and stopping of the fans 44a and 44b based on the temperature detected by the thermistor 631. The thermistor 631 may be provided in both the first region and the second region. A fan for cooling the area may then be operated in response to the temperature detected by each thermistor.

[0052] [Shutter drive configuration] Next, the drive configuration of the shutters 47a, 47b will be described with reference to Figs. 8 to 10. The shutter drive unit 48 has a support plate 49, rack teeth 50a, 50b, a pinion gear 51, and a shutter motor M3. The two left and right shutters 47a, 47b are supported so as to be slidable in the width direction along the plate surface of the support plate 49 that forms the openings 46a, 46b and extends in the width direction (left and right direction in Figs. 9 and 10). The shutters 47a, 47b are provided with rack teeth 50a, 50b, respectively, and the rack teeth 50a, 50b are arranged to sandwich the pinion gear 51, and each of them meshes with the pinion gear 51.

[0053] When the pinion gear 51 is rotated forward and backward by the forward and reverse drive of the shutter motor M3, the shutters 47a, 47b on both sides are linked to open and close the corresponding openings 46a, 46b in a symmetrical relationship in the width direction. As shown in Fig. 10, the openings 46a, 46b on both sides in the width direction are provided from a position α slightly toward the center of the non-passage portion that occurs when a recording material of a minimum width passes through the nip portion N to a position β of the maximum passing width W1. The shutters 47a, 47b on both sides in the width direction are arranged so that they move from the center of the support plate 49 in the longitudinal direction toward the ends to close the openings 46a, 46b by a predetermined amount according to the size of the recording material.

[0054] When the width information of the recording material P is the maximum size recording material, the control circuit section 90 controls the shutter driving section 48 to move to a fully closed position where the openings 46a, 46b are closed by the shutters 47a, 47b as shown in FIG. 9. When the width information of the recording material P is a small size recording material such as an A4 portrait feed size, the control circuit section 90 moves the shutters 47a, 47b to a fully open position where the openings 46a, 46b are opened to a portion corresponding to the non-passage portion as shown in FIG. 10. The position information of the shutters 47a, 47b is detected by a sensor (not shown) arranged on the support plate 49, which detects flags (not shown) arranged at predetermined positions of the shutters 47a, 47b. Specifically, the home position is determined at the shutter position where the openings 46a, 46b are fully closed as shown in FIG. 9, and the opening amount is detected from the amount of rotation of the shutter motor M3. In this embodiment, the shutter motor M3 is a pulse motor.

[0055] [Control Unit] The image forming apparatus 1 includes a control circuit section 90 as a control section. The control circuit section 90 will be described with reference to Fig. 11. However, in addition to those shown in the figure, various devices for operating the image forming apparatus 1 are connected to the control circuit section 90, but illustration and description of those devices will be omitted. Fig. 11 is a block diagram showing the configuration of a control system for the main parts of the image forming apparatus 1 according to this embodiment.

[0056] The control circuit section 90 performs various controls of the image forming apparatus 1, such as image forming operations, and includes, for example, a CPU (Central Processing Unit) and a memory. The memory is composed of a ROM (Read Only Memory) and a RAM (Random Access Memory). The memory stores various programs for controlling the image forming apparatus 1, and various data such as the maximum size width of the recording material P on which an image can be formed and the above-mentioned reciprocating center. The CPU can execute various programs stored in the memory, and executes the various programs to operate the image forming apparatus 1. In this embodiment, the CPU can execute the "image formation job processing (program)", "reciprocating control processing (program)", and "cooling control processing (program)" stored in the memory. The memory can also temporarily store the results of calculations associated with the execution of various programs.

[0057] An image forming job is a series of operations from the start of image formation to the completion of image forming operations based on a print signal for forming an image on a recording material P. That is, it is a series of operations from the start of a preparatory operation (so-called pre-rotation) required for performing image formation, through the image forming process, to the completion of a preparatory operation (so-called post-rotation) required for completing image formation. Specifically, it refers to the period from the pre-rotation after receiving a print signal (preparatory operation before image formation) to the post-rotation (operation after image formation), and includes the image formation period and the period between the trailing end and leading end of successive recording materials (so-called paper interval).

[0058] The control circuit unit 90 is further connected to the fixing drive motor M1, the reciprocating motor M2, the shutter motor M3, the heater energization circuit 92, the front fan 44a, the back fan 44b, and thermistors 630 and 631 via an input / output interface. In this embodiment, the front side is the side where the user operates the image forming apparatus 1, for example, the side where an operation panel or the like is installed, and the back side is the opposite side to the front side. The direction from the front side to the back side and the opposite direction are the width direction described above.

[0059] When an instruction to start an image formation job is given from an external host device such as a personal computer or an operation panel, the control circuit unit 90 executes an "image formation job process" stored in the memory. The control circuit unit 90 controls the image forming apparatus 1 based on the execution of the "image formation job process." In response to this, the control circuit unit 90 drives the fixing drive motor M1 to rotate the pressure roller 70, thereby rotating the fixing film 603. Then, the control circuit unit 90 controls the temperature by the heater current supply circuit 92 so that the surface temperature of the fixing film 603 becomes a desired target temperature.

[0060] The control circuit section 90 controls the reciprocating motor M2 to rotate the reciprocating cam 703, thereby executing the reciprocating operation of the fixing device 40 every time a predetermined number of recording materials P are discharged from the fixing nip section N. That is, the control circuit section 90 controls the reciprocating mechanism 700 so as to move the fixing device 40 every time a predetermined number of recording materials pass through the nip section N. In addition, at the same time as the reciprocating operation is executed, the control circuit section 90 controls the cooling mechanism 800 to change the cooling control of the fixing film 603 independently for the first end side (one end side) and the second end side (opposite end side).

[0061] [Fan airflow correction] Next, the correction of the air volume of the fans 44a and 44b in this embodiment will be described. As described above, when the fixing device is operated in a reciprocating manner, the temperature balance of the widthwise end of the fixing film is lost. Therefore, in this embodiment, at least one of the air volume of the fan 44a and the air volume of the fan 44b is changed according to the widthwise position of the fixing device 40.

[0062] A more detailed description will be given. When the fixing device 40 is at the center position in the width direction, the control circuit unit 90 sets the air volume of the fan 44a to a first air volume and the air volume of the fan 44b to a second air volume. This center position is the reciprocating center described above. Next, the fixing device 40 is moved by the reciprocating mechanism 700, and when the fixing device 40 is located on the first end side (front side) of the center position in the width direction, the air volume of the fan 44a is set to a third air volume smaller than the first air volume, and the air volume of the fan 44b is set to a fourth air volume larger than the second air volume. Similarly, when the fixing device 40 is located on the second end side (rear side) of the center position in the width direction, the air volume of the fan 44a is set to a larger air volume than the first air volume, and the air volume of the fan 44b is set to a smaller air volume than the second air volume. That is, the air volume of the fan on the side where the fixing device 40 is moved is reduced, and the air volume of the fan on the opposite side is increased.

[0063] The air volume may be changed stepwise depending on the position of the fixing device 40 in the width direction. For example, when the fixing device 40 is located at a first position closer to the first end than the central position in the width direction, the air volume of the fan 44a is set to a third air volume, and the air volume of the fan 44b is set to a fourth air volume. When the fixing device 40 is located at a second position closer to the first end than the first position in the width direction, the air volume of the fan 44a is set to a fifth air volume smaller than the third air volume, and the air volume of the fan 44b is set to a sixth air volume larger than the fourth air volume. The same applies when the fixing device 40 is moved to the second end side.

[0064] The air volume of the fans may be changed only for one of the fans. For example, when the air volume of the fan 44a at the central position is the first air volume and the air volume of the fan 44b is the second air volume as described above, when the fixing device 40 is located closer to the first end than the central position in the width direction, the air volume of the fan 44a may be set to a third air volume smaller than the first air volume, and the air volume of the fan 44b may be kept at the second air volume. Alternatively, when the fixing device 40 is located closer to the first end than the central position in the width direction, the air volume of the fan 44a may be kept at the first air volume, and the air volume of the fan 44b may be set to a fourth air volume larger than the second air volume. The same applies when the fixing device 40 is moved to the second end.

[0065] In this embodiment, the air volume of at least one of the fans 44a and 44b is changed at the timing when the fixing device 40 is moved by the reciprocating mechanism 700. However, the timing of changing the air volume is not limited to this, and after the fixing device 40 is moved, for example, the temperature of at least one of the first end side and the second end side of the fixing film 603 may be measured, and the air volume may be changed according to the temperature. For example, when the temperature of the moved side is measured, the air volume may be changed when the measured temperature falls below a certain temperature, and when the temperature of the opposite side to the moved side is measured, the air volume may be changed when the measured temperature rises above a certain temperature. Alternatively, the air volume may be changed when a certain number of recording materials pass through the nip portion N after the fixing device 40 is moved.

[0066] In the case of this embodiment, by changing at least one of the airflow rates of the fans 44a and 44b according to the widthwise position of the fixing device 40, the cooling efficiency of the fans 44a and 44b is changed according to the widthwise position of the fixing device 40. Therefore, even if the fixing device 40 is configured to reciprocate, it is possible to prevent the temperature balance at the widthwise end of the fixing film 603 from being lost.

[0067] For example, when the fixing device 40 moves to the first end side, the air volume of the fan 44a is reduced and the air volume of the fan 44b is increased. This makes it possible to efficiently cool the side where air is blown by the fan 44b, where the non-passing area is widened, while preventing the side where air is blown by the fan 44a, where the non-passing area is narrowed, from being excessively cooled as the fixing device 40 moves.

[0068] An example of the control of this embodiment will be described below with reference to the flow chart of FIG. 12. When the control circuit unit 90 receives a print signal, it starts energizing the heater 600, rotates the pressure roller 70 via the fixing drive motor M1, and heats the fixing film 603 (S001). Based on the detection result of the thermistor 630, the control circuit unit 90 determines whether the temperature of the fixing film 603 has reached the desired target temperature (S002). If the temperature of the fixing film 603 has reached the desired target temperature (Yes in S002), the control circuit unit 90 determines whether the recording material P has a width of the maximum size width on which an image can be formed, based on the size of the recording material P (S003). If the recording material has a width of the maximum size width (Yes in S003), the control circuit unit 90 controls the reciprocating motor M2 to move the fixing device 40 to the center of reciprocation before the recording material P reaches the nip portion N (S004). Next, printing (image formation) is performed (S005), and the job continues until printing is completed (S006).

[0069] On the other hand, if the recording material does not have the maximum width (No in S003), printing is performed as is (S007), and the job is continued until printing is completed (S008). If the predetermined number of sheets is reached during the job (Yes in S009), reciprocating operation is performed, and the fan air volume correction described above is also performed (S010).

[0070] In this embodiment, the air volume of the fan is corrected by a method of determining the correction amount according to the reciprocating amount. That is, the air volume is changed stepwise according to the position in the width direction of the fixing device 40. Table 1 shows an example of the air volume correction amount. In Table 1, the position of the fixing device 40 is expressed as a plus when the fixing device 40 moves forward from the center of the reciprocating motion, and as a minus when the fixing device 40 moves backward. The air volume correction amount is expressed as the percentage increase or decrease from the reference air volume, based on the air volume of the fan when the fixing device 40 is at the center of the reciprocating motion. [Table 1]

[0071] As shown in Table 1, for example, when the reciprocation amount is moved to a position 0.3 mm toward the rear, the air volume of the front fan 44a is set to +5%, and the air volume of the rear fan 44b is set to -5%, based on the fan air volume at the center of reciprocation. As another example, when the reciprocation amount is moved to a position 0.6 mm toward the front, the air volume of the front fan 44a is set to -10%, and the air volume of the rear fan 44b is set to +10%. In this embodiment, the reciprocation amount per time is about 0.3 mm, and the fan air volume is set in correspondence with every 0.3 mm.

[0072] [Example 1] Next, the results of experiments performed in an example in which the control of this embodiment was performed and in a comparative example in which the control of this embodiment was not performed will be described. In the example, image formation was performed according to the flow of Fig. 12, and the air volume correction of the front fan 44a and the rear fan 44b was performed each time the reciprocating operation was performed. In the comparative example, the air volumes of the fans 44a and 44b were not changed even when the fixing device 40 moved.

[0073] In the example and the comparative example, image forming apparatuses having the same configuration were used, and similar controls were performed except for the control of changing the air volume of the fan. The experimental conditions for the example and the comparative example were also the same, and the experiment was performed with a recording material conveying speed of 260 mm / s, a print speed of 60 sheets / min, paper type: CS068 (A4 size), and number of prints: 1000 sheets. Reciprocating operation was performed once for every 250 sheets. Then, the temperature transitions were examined at the center position in the width direction of the fixing film 603, the front end position, and the back end position. Specifically, as shown in FIG. 16 described later, thermistor TH4 was placed at the center position in the width direction of the inner peripheral surface of the fixing film 603, thermistor TH5 at the front end position, and thermistor TH6 at the back end position, and the temperatures were measured at each position.

[0074] The above-mentioned experimental results are shown in Figs. 13 and 14. Fig. 13 shows the temperature transition of the comparative example, and Fig. 14 shows the temperature transition of the example. In the comparative example, as shown in Fig. 13, there was variation in the temperature transition at each position, and it was found that the temperature balance in the width direction of the fixing film 603 was lost. In contrast, in the example, as shown in Fig. 14, the temperature balance of the front and rear ends of the fixing film 603 could be optimally maintained, and the end temperature drop could be suppressed, so that the effect of suppressing poor fixing could be obtained. That is, it was found that according to the configuration of this embodiment, even if the fixing device 40 is configured to move back and forth, it is possible to suppress the temperature balance of the width direction ends of the fixing film 603 from being lost.

[0075] <Second embodiment> The second embodiment will be described with reference to Figs. 15 to 18. In the above-mentioned first embodiment, a configuration was described in which the air volume correction of the front and rear fans is performed in conjunction with the reciprocating operation. In contrast, in this embodiment, the opening width of the front and rear shutters is corrected in conjunction with the reciprocating operation. Since the other configurations and operations are the same as those of the above-mentioned first embodiment, illustrations and descriptions of the similar configurations will be omitted or simplified, and the following description will focus on the points that are different from the first embodiment.

[0076] In this embodiment, as in the first embodiment, the cooling mechanism 800 has a front fan 44a and a rear fan 44b as a blowing section, a duct 45a as a first duct, and a duct 45b as a second duct. The duct 45a guides the air sent from the fan 44a toward the first area, and the duct 45b guides the air sent from the fan 44b toward the second area. Note that in this embodiment, for example, the blowing section may be a single fan, and the air from this fan may be branched and sent to the duct 45a and the duct 45b.

[0077] Also, like the first embodiment, the present embodiment has shutters 47a and 47b for changing the opening widths of the openings 46a and 46b of the ducts 45a and 45b. However, unlike the first embodiment, the present embodiment is capable of driving the shutters 47a and 47b separately. For this reason, as shown in FIG. 15, the present embodiment is provided with a shutter motor M3 for driving the shutter 47a and a shutter motor M4 for driving the shutter 47b. FIG. 15 is a block diagram showing the configuration of a control system of the main parts in the image forming apparatus 1 of the present embodiment, and the shutter motor M4 is added to the block diagram of FIG. 11 of the first embodiment. Also, in FIG. 15, thermistors TH1 to TH6 are added to FIG. 11.

[0078] The position of the thermistor as a temperature detector for detecting the temperature of the heater 600 or the fixing film 603 in this embodiment will be described with reference to FIG. 16. In this embodiment, the thermistor TH1 is provided so as to detect the temperature of the area of ​​the heater 600 through which all recording materials used in the image forming apparatus 1 pass. For this purpose, the thermistor TH1 is provided in the center of the heater 600 in the longitudinal direction. The thermistors TH2 and TH3 are provided between the center and the ends of the heater 600 in the longitudinal direction, respectively. Thermistor TH4 is disposed in the center of the inner surface of the fixing film 603, and thermistors TH5 and TH6 are disposed on the end sides of the inner surface of the fixing film 603, respectively. The thermistors TH4, TH5, and TH6 are used to detect the temperatures of the center of the fixing film 603 and the area through which the recording material P does not pass.

[0079] That is, the thermistor TH4 is disposed inside the fixing film 603, for example, in contact with or close to the inner circumferential surface of the central portion of the fixing film 603 in the width direction, and detects the temperature of the fixing film 603. Thermistors TH5 and TH6 are disposed inside the fixing film 603, for example, in contact with or close to the inner circumferential surfaces of the first end side and the second end side of the fixing film 603 from the central portion in the width direction, and detect the temperature of the fixing film 603. In FIG. 16, the thermistor TH5 is disposed near the end of the first region on the front side of the fixing film 603, and detects the temperature of the fixing film 603 in this region. Thermistor TH6 is disposed near the end of the second region on the back side of the fixing film 603, and detects the temperature of the fixing film 603 in this region.

[0080] The detection information (signal values ​​related to temperature) of the thermistors TH1, TH2, TH3, TH4, TH5, and TH6 is input to the control circuit unit 90 via an A / D converter. The control circuit unit 90 controls the power supplied to the heater 600 according to the temperature detected by thermistor TH4. The control circuit unit 90 also controls the driving and stopping of the fans 44a and 44b based on the temperatures detected by thermistors TH5 and TH6. That is, the operation of the fans 44a and 44b is performed when the temperatures of thermistors TH5 and TH6 exceed a predetermined temperature. For example, the driving of the fan 44a is started when the temperature of thermistor TH5 exceeds a predetermined temperature, and the driving of the fan 44b is started when the temperature of thermistor TH6 exceeds a predetermined temperature.

[0081] FIG. 17 shows the drive configuration of the shutter in this embodiment. As described above, in this embodiment, the shutters 47a and 47b can be driven separately, and therefore, unlike the first embodiment, there are two shutter motors M3 and M4, and pinion gears 51a and 51b driven by the respective motors. The rack teeth 50a and 50b of the shutters 47a and 47b are meshed with the pinion gears 51a and 51b. As a result, the two shutters 47a and 47b can be opened and closed independently with respect to the corresponding openings 46a and 46b by forward and reverse rotation of the pinion gears 51a and 51b. The two openings 46a and 45b on both sides in the width direction are provided so as to open a range of 116 mm to 165 mm from the longitudinal center.

[0082] [Shutter aperture width correction] Next, the correction of the opening width of the shutters 47a and 47b in this embodiment will be described. In this embodiment, at least one of the opening width of the duct 45a formed by the shutter 47a and the opening width of the duct 45b formed by the shutter 47b is changed according to the widthwise position of the fixing device 40. Hereinafter, the opening width of the duct 45a formed by the shutter 47a is referred to as the opening width of the shutter 47a, and the opening width of the duct 45b formed by the shutter 47b is referred to as the opening width of the shutter 47b.

[0083] A more detailed description will be given. When the fixing device 40 is at the center position in the width direction, the control circuit unit 90 sets the opening width of the shutter 47a to the first opening width and the opening width of the shutter 47b to the second opening width. This center position is the above-mentioned reciprocating center. Next, the fixing device 40 is moved by the reciprocating mechanism 700, and when the fixing device 40 is located on the first end side (front side) of the center position in the width direction, the opening width of the shutter 47a is set to the third opening width narrower than the first opening width, and the opening width of the shutter 47b is set to the fourth opening width wider than the second opening width. Similarly, when the fixing device 40 is located on the second end side (rear side) of the center position in the width direction, the opening width of the shutter 47a is set to the opening width wider than the first opening width, and the opening width of the shutter 47b is set to the opening width narrower than the second opening width. That is, the opening width of the shutter on the side where the fixing device 40 is moved is narrowed, and the opening width of the shutter on the opposite side is widened.

[0084] The opening width of the shutters may be changed stepwise depending on the position of the fixing device 40 in the width direction. For example, when the fixing device 40 is located at a first position closer to the first end than the central position in the width direction, the opening width of the shutter 47a is set to a third opening width, and the opening width of the shutter 47b is set to a fourth opening width. When the fixing device 40 is located at a second position closer to the first end than the first position in the width direction, the opening width of the shutter 47a is set to a fifth opening width narrower than the third opening width, and the opening width of the shutter 47b is set to a sixth opening width wider than the fourth opening width. The same applies when the fixing device 40 is moved to the second end side.

[0085] The aperture width of the shutter may be changed only for one of the shutters. For example, when the aperture width of the shutter 47a at the central position is the first aperture width and the aperture width of the shutter 47b is the second aperture width as described above, when the fixing device 40 is located on the first end side from the central position in the width direction, the aperture width of the shutter 47a may be set to a third aperture width narrower than the first aperture width, and the aperture width of the shutter 47b may be left as the second aperture width. Alternatively, when the fixing device 40 is located on the first end side from the central position in the width direction, the aperture width of the shutter 47a may be left as the first aperture width, and the aperture width of the shutter 47b may be set to a fourth aperture width wider than the second aperture width. The same applies when the fixing device 40 is moved to the second end side.

[0086] In this embodiment, the opening width of at least one of the shutters 47a and 47b is changed at the timing when the fixing device 40 is moved by the reciprocating mechanism 700. However, the timing of changing the opening width is not limited to this, and after the fixing device 40 is moved, for example, the temperature of at least one of the first end side and the second end side of the fixing film 603 may be measured, and the opening width may be changed according to the temperature. For example, when the temperature of the moved side is measured, the opening width may be changed when the measured temperature falls below a certain temperature, and when the temperature of the opposite side to the moved side is measured, the opening width may be changed when the measured temperature rises above a certain temperature. Alternatively, the opening width may be changed when a certain number of recording materials pass through the nip portion N after the fixing device 40 is moved.

[0087] In the case of this embodiment, at least one of the opening widths of the shutters 47a and 47b is changed depending on the widthwise position of the fixing device 40, so that the cooling efficiency of the fans 44a and 44b is changed depending on the widthwise position of the fixing device 40. Therefore, even if the fixing device 40 is configured to reciprocate, it is possible to prevent the temperature balance at the widthwise ends of the fixing film 603 from being lost.

[0088] For example, when fixing device 40 moves to the first end side, the opening width of shutter 47a is narrowed and the opening width of shutter 47b is widened. This makes it possible to efficiently cool the side where air is blown by fan 44b, where the non-passing area is widened, while suppressing excessive cooling of the side where air is blown by fan 44a, where the non-passing area is narrowed as fixing device 40 moves.

[0089] An example of the control of this embodiment will be described below with reference to the flowchart in Fig. 18. Note that the flowchart in Fig. 18 is the same as the flowchart in Fig. 12 except that "S010" has been changed to "S011". Therefore, descriptions of the other steps will be omitted. In S009, if the predetermined number of sheets is reached during the job (Yes in S009), a reciprocating operation is performed, and the shutter opening width correction described above is also performed (S011).

[0090] In this embodiment, the shutter opening width correction is performed by a means for determining the correction amount according to the reciprocating amount. That is, the air volume is changed stepwise according to the position of the fixing device 40 in the width direction. Table 2 shows an example of the shutter opening width correction amount (hereinafter, also referred to as the correction width). In Table 2, the position of the fixing device 40 is expressed as a plus when the fixing device 40 moves forward from the center of the reciprocating motion, and as a minus when the fixing device 40 moves backward. The correction width is expressed as an increase or decrease from the reference opening width, based on the shutter opening width when the fixing device 40 is at the center of the reciprocating motion. [Table 2]

[0091] As shown in Table 2, for example, when the reciprocation amount moves to a position 0.3 mm toward the rear side based on the shutter position at the center of reciprocation, the opening width of the front shutter 47a is set to +1 mm, and the opening width of the rear shutter 47b is set to -1 mm. As another example, when the reciprocation amount moves to a position 0.6 mm toward the front side, the opening width of the front shutter 47a is set to -2 mm, and the opening width of the rear shutter 47b is set to +2 mm. In this embodiment, the reciprocation amount per time is set to about 0.3 mm, and the opening width of the shutter is set in increments of 0.3 mm.

[0092] [Example 2] Next, the results of an experiment performed on an example in which the control of this embodiment was performed will be described. In the example, image formation was performed according to the flow of Fig. 18, and the aperture width correction of the front shutter 47a and the aperture width correction of the back shutter 47b were performed each time a reciprocating operation was performed. The experiment was performed with a recording material conveying speed of 260 mm / s, a print speed of 60 sheets / min, paper type: CS068 (A4 size), and print count: 1000 sheets. Reciprocating operation was performed once for every 250 sheets. Then, the temperature transitions at the center position in the width direction of the fixing film 603, the front end position, and the rear end position were examined. As a result, the temperature balance between the front and rear ends could be optimally maintained, and a drop in the end temperature could be suppressed, so that the effect of suppressing poor fixing could be obtained. That is, according to the configuration of this embodiment, it was found that even if the fixing device 40 is configured to move back and forth, it is possible to suppress the temperature balance at the ends in the width direction of the fixing film 603 from being disrupted.

[0093] <Third embodiment> The third embodiment will be described using FIG. 19 with reference to FIG. 15 and FIG. 16. In the first embodiment described above, the configuration in which the air volume correction of the front and rear fans is performed in conjunction with the reciprocating operation, and in the second embodiment, the configuration in which the opening width of the front and rear shutters is corrected in conjunction with the reciprocating operation, have been described. In contrast, in this embodiment, the operating temperature conditions of the front and rear fans are corrected in conjunction with the reciprocating operation. Since the other configurations and operations are the same as those of the first or second embodiment described above, illustrations and descriptions of the similar configurations will be omitted or simplified, and the following description will focus on the differences from the first and second embodiments.

[0094] The positions of the thermistors as temperature detectors for detecting the temperature of the heater 600 or the fixing film 603 in this embodiment are the same as those in the second embodiment shown in Fig. 16. That is, thermistor TH1 is provided in the center of the heater 600 in the longitudinal direction. Thermistors TH2 and TH3 are provided between the center and ends of the heater 600 in the longitudinal direction, thermistor TH4 is disposed in the center of the inner surface of the fixing film 603, and thermistors TH5 and TH6 are disposed on the end sides of the inner surface of the fixing film 603.

[0095] The thermistors TH5 and TH6 are disposed inside the fixing film 603, for example, in contact with or close to the inner circumferential surface on the first end side and the second end side rather than the center in the width direction of the fixing film 603, and detect the temperature of the fixing film 603. In Fig. 16, the thermistor TH5 as the first temperature detection unit is disposed near the end of the first region on the front side of the fixing film 603, and detects the temperature of the fixing film 603 in this region. Thermistor TH6 as the second temperature detection member is disposed near the end of the second region on the rear side of the fixing film 603, and detects the temperature of the fixing film 603 in this region.

[0096] The control circuit section 90 controls the driving and stopping of the fan 44a based on the temperature detected by the thermistor TH5, and the driving and stopping of the fan 44b based on the temperature detected by the thermistor TH6. For example, when the temperature of the thermistor TH5 exceeds a predetermined temperature, the driving of the fan 44a is started, and when the temperature of the thermistor TH6 exceeds a predetermined temperature, the driving of the fan 44b is started. In this embodiment, this predetermined temperature is corrected by the reciprocating amount of the fixing device 40. That is, the control circuit section 90 changes at least one of the temperatures at which the fan 44a starts to drive and the fan 44b starts to drive, depending on the position in the width direction of the fixing device 40. Note that, in this embodiment, the air volume of the fans 44a and 44b is not changed.

[0097] A more detailed description will be given. When the fixing device 40 is at the center position in the width direction, the control circuit unit 90 sets the temperature at which the fan 44a starts to drive as the first temperature, and the temperature at which the fan 44b starts to drive as the second temperature. This center position is the above-mentioned reciprocating center. Next, the fixing device 40 is moved by the reciprocating mechanism 700, and when the fixing device 40 is located on the first end side (front side) of the center position in the width direction, the temperature at which the fan 44a starts to drive is set as the third temperature higher than the first temperature, and the temperature at which the fan 44b starts to drive is set as the fourth temperature lower than the second temperature. Similarly, when the fixing device 40 is located on the second end side (rear side) of the center position in the width direction, the temperature at which the fan 44a starts to drive is set as the temperature lower than the first temperature, and the temperature at which the fan 44b starts to drive is set as the temperature higher than the second temperature. That is, the drive start temperature of the fan on the side where the fixing device 40 is moved is made higher, and the drive start temperature of the fan on the opposite side is made lower. Also, the fan drive start temperature may be changed stepwise depending on the position in the width direction of the fixing device 40 .

[0098] The fan drive start temperature may be changed at only one of the temperatures. For example, when the drive start temperature of the fan 44a at the central position is set to the first temperature and the drive start temperature of the fan 44b at the second temperature as described above, when the fixing device 40 is located closer to the first end than the central position in the width direction, the drive start temperature of the fan 44a may be set to a third temperature higher than the first temperature, and the drive start temperature of the fan 44b may be kept at the second temperature. Alternatively, when the fixing device 40 is located closer to the first end than the central position in the width direction, the drive start temperature of the fan 44a may be kept at the first temperature, and the drive start temperature of the fan 44b may be set to a fourth temperature lower than the second temperature. The same applies when the fixing device 40 is moved to the second end.

[0099] In this embodiment, at least one of the drive start temperatures of the fans 44a and 44b is changed at the timing when the fixing device 40 is moved by the reciprocating mechanism 700. However, the timing of changing the temperature is not limited to this, and after the fixing device 40 is moved, for example, the temperature of at least one of the first end side and the second end side of the fixing film 603 may be measured, and the drive start temperature may be changed according to the measured temperature. For example, when the temperature of the moved side is measured, the drive start temperature may be changed when the measured temperature falls below a certain temperature, and when the temperature of the opposite side to the moved side is measured, the drive start temperature may be changed when the measured temperature rises above a certain temperature. Alternatively, the drive start temperature may be changed when a certain number of recording materials pass through the nip portion N after the fixing device 40 is moved.

[0100] In the case of this embodiment, at least one of the temperatures at which the fan 44a starts to drive and the temperature at which the fan 44b starts to drive is changed according to the widthwise position of the fixing device 40, so that the drive timing and drive time of the fans 44a and 44b are changed according to the widthwise position of the fixing device 40. Therefore, even if the fixing device 40 is configured to reciprocate, it is possible to prevent the temperature balance at the widthwise ends of the fixing film 603 from being lost.

[0101] For example, when the fixing device 40 moves to the first end side, the drive start temperature of the fan 44a is increased and the drive start temperature of the fan 44b is decreased, so that the drive timing of the fan 44a can be delayed from the drive timing of the fan 44b, or the drive time of the fan 44a can be made shorter than the drive time of the fan 44b. Therefore, the side where the air is blown by the fan 44b, where the non-passing area is widened as the fixing device 40 moves, can be efficiently cooled while preventing the side where the air is blown by the fan 44a, where the non-passing area is narrowed, from being excessively cooled.

[0102] An example of control in this embodiment will be described below with reference to the flowchart in Fig. 19. The flowchart in Fig. 19 is the same as the flowchart in Fig. 12 except that "S010" has been changed to "S012". Therefore, a description of the other steps will be omitted. In S009, if the predetermined number of sheets is reached during the job (Yes in S009), reciprocal operation is performed, and the fan drive start temperature correction described above is also performed (S012).

[0103] <Other embodiments> In the above-mentioned embodiments, the fixing belt is a fixing film, which is a film-like member, but the fixing belt may be, for example, a belt having an elastic layer or a surface layer on a resin base layer. The fixing unit may be configured to stretch the fixing belt by a plurality of tension members. Furthermore, the nip portion forming member may be a belt other than a roller, and is preferably a rotating body.

[0104] Furthermore, the reciprocating mechanism 700 may reciprocate the fixing device 40 and the cooling mechanism 800, and the fixing device 40 and the cooling mechanism 800 may be integrated together. With this configuration, unlike the above-described embodiment, it is not necessary to consider the amount of movement of the fixing device 40 by the reciprocating mechanism 700, and cooling can be performed in accordance with the non-passage area.

[0105] The disclosure of this embodiment also includes the following configuration. (Configuration 1) a fixing device including a first rotating body, a second rotating body that forms a nip portion between the first rotating body and a recording material carrying a toner image thereon by sandwiching and conveying the recording material between the first rotating body and the second rotating body to fix the toner image onto the recording material, and a heating portion that heats the first rotating body; a first blowing section that blows air toward a first region of the first rotating body that is closer to a first end portion than a center portion of the first rotating body in a width direction that intersects with a conveying direction of the recording material; a second blowing section that blows air toward a second region of the first rotating body that is a second end side of the first rotating body that is opposite to the first end side from the central portion of the first rotating body in the width direction; a reciprocating unit that reciprocates the fixing device in the width direction; a control unit that changes at least one of an air volume of the first blower unit and an air volume of the second blower unit in accordance with a position of the fixing device in the width direction. 1. An image forming apparatus comprising: (Configuration 2) When the fixing device is at a central position in the width direction, the control unit sets the air volume of the first blower unit to a first air volume and the air volume of the second blower unit to a second air volume, and when the fixing device is located closer to the first end than the central position in the width direction, sets the air volume of the first blower unit to a third air volume smaller than the first air volume and sets the air volume of the second blower unit to a fourth air volume larger than the second air volume. 2. The image forming apparatus according to claim 1, (Configuration 3) When the fixing device is located at a first position closer to the first end than the central position in the width direction, the control unit sets the air volume of the first blower unit to the third air volume and the air volume of the second blower unit to the fourth air volume, and when the fixing device is located at a second position closer to the first end than the first position in the width direction, sets the air volume of the first blower unit to a fifth air volume smaller than the third air volume and sets the air volume of the second blower unit to a sixth air volume larger than the fourth air volume. 3. The image forming apparatus according to claim 2, (Configuration 4) The control unit changes an air volume of at least one of the first air blowing unit and the second air blowing unit at a timing when the reciprocating unit moves the fixing device. 4. The image forming apparatus according to any one of configurations 1 to 3, (Configuration 5) The control unit controls the reciprocating unit to move the fixing device every time a predetermined number of recording materials pass through the nip portion. 5. The image forming apparatus according to any one of configurations 1 to 4. (Configuration 6) the fixing device has a temperature detection unit configured to detect a temperature of the first rotating body located closer to an end portion than a central portion in the width direction, The control unit controls driving and stopping of the first blower unit and the second blower unit based on the temperature detected by the temperature detection unit. 6. The image forming apparatus according to any one of configurations 1 to 5, (Configuration 7) a fixing device including a first rotating body, a second rotating body that forms a nip portion between the first rotating body and a recording material carrying a toner image thereon by sandwiching and conveying the recording material between the first rotating body and the second rotating body to fix the toner image onto the recording material, and a heating portion that heats the first rotating body; A blower that blows air; a first duct that guides the air sent from the blower unit toward a first region of the first rotating body that is closer to a first end portion than a center portion of the first rotating body in a width direction that intersects with a conveying direction of the recording material; a first shutter capable of changing an opening width of the first duct; a second duct that guides the air sent from the blower toward a second region of the first rotating body that is on a second end side opposite to the first end from the central portion of the first rotating body; a second shutter capable of changing an opening width of the second duct; a reciprocating unit that reciprocates the fixing device in the width direction; a control unit that changes at least one of an opening width of the first duct formed by the first shutter and an opening width of the second duct formed by the second shutter in accordance with a position of the fixing device in the width direction. 1. An image forming apparatus comprising: (Configuration 8) an opening width of the first duct formed by the first shutter is defined as an opening width of the first shutter, and an opening width of the second duct formed by the second shutter is defined as an opening width of the second shutter, When the fixing device is at a central position in the width direction, the control unit sets the opening width of the first shutter to a first opening width and the opening width of the second shutter to a second opening width, and when the fixing device is located closer to the first end than the central position in the width direction, the control unit sets the opening width of the first shutter to a third opening width narrower than the first opening width and the opening width of the second shutter to a fourth opening width wider than the second opening width. 8. The image forming apparatus according to claim 7, (Configuration 9) When the fixing device is located at a first position closer to the first end than the central position in the width direction, the control unit sets the opening width of the first shutter to the third opening width and the opening width of the second shutter to the fourth opening width, and when the fixing device is located at a second position closer to the first end than the first position in the width direction, the control unit sets the opening width of the first shutter to a fifth opening width narrower than the third opening width and the opening width of the second shutter to a sixth opening width wider than the fourth opening width. 9. The image forming apparatus according to configuration 8, (Configuration 10) The control unit changes at least one of an opening width of the first shutter and an opening width of the second shutter at a timing when the reciprocating unit moves the fixing device. 10. The image forming apparatus according to any one of configurations 7 to 9, (Configuration 11) The control unit controls the reciprocating unit to move the fixing device every time a predetermined number of recording materials pass through the nip portion. 11. The image forming apparatus according to any one of configurations 7 to 10, (Configuration 12) the fixing device has a temperature detection unit configured to detect a temperature of the first rotating body located closer to an end portion than a central portion in the width direction, The control unit controls driving and stopping of the air blowing unit based on the temperature detected by the temperature detection unit. 12. The image forming apparatus according to any one of configurations 7 to 11, (Configuration 13) a fixing device including a first rotating body, a second rotating body that forms a nip portion between the first rotating body and the second rotating body to sandwich and transport a recording material carrying a toner image thereon, and fixes the toner image onto the recording material, a heating portion that heats the first rotating body, a first temperature detection portion that detects the temperature of the first rotating body on a first end side of the first rotating body relative to a center portion of the first rotating body in a width direction that intersects with a transport direction of the recording material, and a second temperature detection portion that detects the temperature of the first rotating body on a second end side that is opposite the first end side of the center portion in the width direction; a first blowing section that blows air toward a first region of the first rotating body that is closer to the first end portion than the central portion in the width direction; a second blowing section that blows air toward a second region of the first rotating body that is closer to the second end than the central portion in the width direction; a reciprocating unit that reciprocates the fixing device in the width direction; a control unit that controls the operation and stop of the first blower unit based on the temperature detected by the first temperature detection unit, and the operation and stop of the second blower unit based on the temperature detected by the second temperature detection unit, The control unit changes at least one of a temperature at which the first blower unit starts to operate and a temperature at which the second blower unit starts to operate, depending on a position of the fixing device in the width direction. 1. An image forming apparatus comprising: (Configuration 14) When the fixing device is located at a central position in the width direction, the control unit sets a temperature at which the first blower unit starts to operate to a first temperature and a temperature at which the second blower unit starts to operate to a second temperature, and when the fixing device is located closer to the first end than the central position in the width direction, sets a temperature at which the first blower unit starts to operate to a third temperature higher than the first temperature and a temperature at which the second blower unit starts to operate to a fourth temperature lower than the second temperature. 14. The image forming apparatus according to claim 13, (Configuration 15) The control unit changes at least one of a temperature at which the first blower unit starts to operate and a temperature at which the second blower unit starts to operate at a timing when the reciprocating unit moves the fixing device. 15. The image forming apparatus according to claim 13 or 14. (Configuration 16) The control unit controls the reciprocating unit to move the fixing device every time a predetermined number of recording materials pass through the nip portion. 16. The image forming apparatus according to any one of configurations 13 to 15, [Explanation of symbols]

[0106] 1. Image forming device 40... Fixing device 44a Fan (first blower, blower) 44b Fan (second blower, blower) 45a···Duct (1st duct) 45b···Duct (Second duct) 47a···Shutter (1st shutter) 47b···Shutter (2nd shutter) 70 Pressure roller (second rotating body) 90 Control circuit section (control section) 600···Heater (heating part) 603 Fixing film (first rotating body) 631...Thermistor (temperature detection part) 700···Reciprocating mechanism (reciprocating movement part) 800...Cooling mechanism TH5...Thermistor (Temperature detection section, 1st temperature detection section) TH6...Thermistor (Temperature detection part, Second temperature detection part)

Claims

1. a fixing device including a first rotating body, a second rotating body that sandwiches and conveys a recording material carrying a toner image between the first rotating body and a second rotating body to form a nip portion where the toner image is fixed to the recording material, and a heating portion that heats the first rotating body; A blower that blows air; a first duct that guides the air sent from the air blowing unit toward a first region of the first rotating body that is closer to a first end than a center portion of the first rotating body in a width direction that intersects with a conveyance direction of the recording material; a first shutter capable of changing the opening width of the first duct; a second duct that guides the air sent from the blower toward a second region of the first rotating body that is located on a second end side of the first rotating body that is opposite to the first end side relative to the central portion of the first rotating body; a second shutter capable of changing the opening width of the second duct; a reciprocating unit that reciprocates the fixing device in the width direction; a control unit that changes at least one of an opening width of the first duct formed by the first shutter and an opening width of the second duct formed by the second shutter in accordance with a position of the fixing device in the width direction. An image forming apparatus characterized by:

2. an opening width of the first duct formed by the first shutter is defined as an opening width of the first shutter, and an opening width of the second duct formed by the second shutter is defined as an opening width of the second shutter, When the fixing device is at a central position in the width direction, the control unit sets the opening width of the first shutter to a first opening width and the opening width of the second shutter to a second opening width, and when the fixing device is located closer to the first end than the central position in the width direction, sets the opening width of the first shutter to a third opening width narrower than the first opening width and the opening width of the second shutter to a fourth opening width wider than the second opening width.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

3. When the fixing device is located at a first position closer to the first end than the central position in the width direction, the control unit sets the opening width of the first shutter to the third opening width and the opening width of the second shutter to the fourth opening width, and when the fixing device is located at a second position closer to the first end than the first position in the width direction, the control unit sets the opening width of the first shutter to a fifth opening width narrower than the third opening width and the opening width of the second shutter to a sixth opening width wider than the fourth opening width.

3. The image forming apparatus according to claim 2, wherein the image forming apparatus is a recording medium.

4. The control unit changes at least one of the opening width of the first shutter and the opening width of the second shutter at a timing when the reciprocating unit moves the fixing device.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

5. The control unit controls the reciprocating unit to move the fixing device every time a predetermined number of recording materials pass through the nip portion.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

6. the fixing device has a temperature detection unit that detects the temperature of the first rotating body that is closer to an end portion than the central portion in the width direction, The control unit controls driving and stopping of the air blower unit based on the temperature detected by the temperature detection unit.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

7. The reciprocating movement unit reciprocates the fixing device, the first shutter, and the second shutter.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

8. a fixing device including: a first rotating body; a second rotating body that sandwiches and conveys a recording material carrying a toner image between the first rotating body and a nip portion that fixes the toner image to the recording material; a heating portion that heats the first rotating body; a first temperature detecting portion that detects the temperature of the first rotating body at a first end side relative to a center portion of the first rotating body in a width direction that intersects with the conveyance direction of the recording material; and a second temperature detecting portion that detects the temperature of the first rotating body at a second end side that is opposite the first end side relative to the center portion in the width direction; a first blowing unit configured to blow air toward a first region of the first rotating body that is closer to the first end portion than the central portion in the width direction; a second blowing unit configured to blow air toward a second region of the first rotating body that is closer to the second end portion than the central portion in the width direction; a reciprocating unit that reciprocates the fixing device in the width direction; a control unit that controls the driving and stopping of the first blower unit based on the temperature detected by the first temperature detection unit, and the driving and stopping of the second blower unit based on the temperature detected by the second temperature detection unit, The control unit changes at least one of the temperature at which the first blower unit starts to operate and the temperature at which the second blower unit starts to operate, depending on a position of the fixing device in the width direction. An image forming apparatus characterized by:

9. When the fixing device is located at a central position in the width direction, the control unit sets the temperature at which the first air blowing unit starts to operate to a first temperature and the temperature at which the second air blowing unit starts to operate to a second temperature, and when the fixing device is located closer to the first end than the central position in the width direction, sets the temperature at which the first air blowing unit starts to operate to a third temperature higher than the first temperature and the temperature at which the second air blowing unit starts to operate to a fourth temperature lower than the second temperature.

9. The image forming apparatus according to claim 8,

10. The control unit changes at least one of the temperature at which the first blower unit starts to operate and the temperature at which the second blower unit starts to operate at a timing when the reciprocating unit moves the fixing device.

9. The image forming apparatus according to claim 8,

11. The control unit controls the reciprocating unit to move the fixing device every time a predetermined number of recording materials pass through the nip portion.

9. The image forming apparatus according to claim 8,

Images