Image forming apparatus

Abstract

To provide a configuration that blows air to a recording material to peel off the recording material from a fixing belt 301, and that can suppress occurrence of uneven glossiness in a toner image.SOLUTION: A fixing belt 301 heats a toner image carried on a recording material to fix the toner image to the recording material. A halogen heater 306 heats the fixing belt 301. A pressure roller 305 forms, with the fixing belt 301, a nip part N for sandwiching and conveying the recording material. An air nozzle 401 blows air to peel off the recording material from the fixing belt 301. An air path 402 is a channel for sending air to the air nozzle 401. A piping member 402b as a part of the air path 402 is arranged above the fixing belt 301 in the vertical direction, and within a range overlapping the fixing belt 301 when the fixing belt 301 is seen from above.SELECTED DRAWING: Figure 4

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 fixes a toner image carried on a recording material to the recording material. In the fixing device, the toner image on the recording material is heated and conveyed in a nip portion formed by a fixing member and a nip portion forming member. At this time, there is a risk that the recording material will stick to the fixing member and not be peeled off from the fixing member. For this reason, a configuration has been proposed that includes a nozzle for blowing air onto the leading edge of the recording material in order to peel the recording material off from the fixing member (Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 60-247672 [Patent Document 2] JP 2007-94327 A Summary of the Invention [Problem to be solved by the invention]

[0004] Here, in the case of a configuration in which air is blown onto the recording material to separate it from the fixing member, the toner image on the recording material may be cooled by the air blown from the nozzles. Since the glossiness of the cooled toner image changes depending on the cooling temperature, there is a risk of uneven gloss occurring in the toner image.

[0005] SUMMARY OF THE DISCLOSURE An object of the present invention is to provide a configuration in which air is blown to separate a recording material from a fixing member, and in which the occurrence of uneven gloss on a toner image can be suppressed. [Means for solving the problem]

[0006] The image forming apparatus of the present invention comprises a fixing device having a fixing member that heats a toner image carried on a recording material to fix it to the recording material, a heating section that heats the fixing member, a nip portion forming member that forms a nip portion between the fixing member and the nip portion for sandwiching and transporting the recording material, and a nozzle that blows air to peel the recording material from the fixing member, and a flow path member for sending air to the nozzle, wherein a portion of the flow path member is arranged vertically above the fixing member and in a range that overlaps with the fixing member when viewed from above. Effect of the Invention

[0007] According to the present invention, in a configuration in which air is blown to separate the recording material from the fixing member, it is possible to suppress the occurrence of gloss unevenness in a toner image. [Brief description of the drawings]

[0008] [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] FIG. 2 is a cross-sectional view including a cover of the fixing device according to the first embodiment. [Figure 4] FIG. 2 is a perspective view of a fixing device, an air nozzle, and an air path according to the first embodiment. [Diagram 5] FIG. 2A is a perspective view of an air nozzle according to the first embodiment, and FIG. [Figure 6] FIG. 2 is a schematic diagram showing a path from an air compressor to an air nozzle according to the first embodiment, as viewed from above. [Figure 7] 6 is a graph showing temperature distribution on a recording material in an example and a comparative example. [Figure 8] FIG. 11 is a cross-sectional view showing a schematic configuration of a fixing device according to a second embodiment. [Figure 9] FIG. 11 is a perspective view of a fixing device, an air nozzle, and an air path according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] <First embodiment> The first embodiment will be described with reference to Figures 1 to 7. First, the schematic configuration of an image forming apparatus according to the present embodiment will be described with reference to Figure 1.

[0010] [Image forming device] The image forming apparatus 1 is an electrophotographic full-color printer having four image forming units Pa, Pb, Pc, and Pd provided corresponding to the four colors of yellow, magenta, cyan, and black. In this embodiment, the image forming units Pa, Pb, Pc, and Pd are of a tandem type arranged along the rotation direction of an intermediate transfer belt 204 described later. The image forming apparatus 1 forms a toner image (image) on a recording material in response to an image signal from an image reading unit (original reading device) 2 connected to the image forming apparatus main body 3 or a host device such as a personal computer connected to the image forming apparatus main body 3 so as to be able to communicate with the image forming apparatus main body 3. Examples of the recording material include sheet materials such as paper, plastic film, and cloth.

[0011] The image forming apparatus 1 comprises an image reading section 2 and an image forming apparatus main body 3. The image reading section 2 reads an original placed on an original platen glass 21, and light emitted from a light source 22 is reflected by the original and an image is formed on a CCD sensor 24 via an optical system member 23 such as a lens. Such an optical system unit converts the original into an electric signal data string for each line by scanning in the direction of the arrow. The image signal obtained by the CCD sensor 24 is sent to the image forming apparatus main body 3, and a control section 30 performs image processing in accordance with each image forming section described later. The control section 30 also receives external inputs as image signals from external host devices such as a print server.

[0012] The image forming apparatus main body 3 includes a plurality of image forming units Pa, Pb, Pc, and Pd, and each image forming unit forms an image based on the image signal. That is, the image signal is converted into a laser beam that is PWM (pulse width modulation) controlled by a control unit 30. A polygon scanner 31 as an exposure device scans with the laser beam according to the image signal. Then, the laser beam is irradiated onto photosensitive drums 200a to 200d as image carriers of the image forming units Pa to Pd.

[0013] Note that Pa is a yellow (Y) image forming section, Pb is a magenta (M) image forming section, Pc is a cyan (C) image forming section, and Pd is a black (Bk) image forming section, which form images of the corresponding colors. Since the image forming sections Pa to Pd are substantially the same, the Y image forming section Pa will be described in detail below, and the other image forming sections will not be described. In the image forming section Pa, a toner image is formed on the surface of the photosensitive drum 200a based on an image signal, as described below.

[0014] The charging roller 201a, which serves as a primary charger, charges the surface of the photosensitive drum 200a to a predetermined potential to prepare for the formation of an electrostatic latent image. An electrostatic latent image is formed on the surface of the photosensitive drum 200a, which has been charged to a predetermined potential, by a laser beam from the polygon scanner 31. The developing unit 202a develops the electrostatic latent image on the photosensitive drum 200a to form a toner image. The primary transfer roller 203a discharges electricity from the rear surface of the intermediate transfer belt 204, applies a primary transfer bias of opposite polarity to the toner, and transfers the toner image on the photosensitive drum 200a onto the intermediate transfer belt 204. After the transfer, the surface of the photosensitive drum 200a is cleaned by a cleaner 207a.

[0015] The toner image on intermediate transfer belt 204 is then conveyed to the next image forming section, where the toner images of each color formed in each image forming section are transferred in the order of Y, M, C, and Bk, forming a four-color image on the surface. The toner image that has passed through Bk image forming section Pd, which is located at the most downstream side in the rotation direction of intermediate transfer belt 204, is conveyed to a secondary transfer section composed of a pair of secondary transfer rollers 205 and 206. In the secondary transfer section, a secondary transfer electric field of opposite polarity to the toner image on intermediate transfer belt 204 is applied, so that the toner image is secondarily transferred to the recording material.

[0016] The recording material is stored in a cassette 9, and the recording material fed from the cassette 9 is transported to a registration unit 208 consisting of, for example, a pair of registration rollers, and waits at the registration unit 208. Thereafter, the registration unit 208 controls the timing to align the toner image on the intermediate transfer belt 204 with the position of the paper, and transports the recording material to a secondary transfer unit.

[0017] The recording material onto which the toner image has been transferred in the secondary transfer section is transported to a fixing device 8, where the toner image carried on the recording material is fixed to the recording material by heating and pressurizing it. The recording material that has passed through the fixing device 8 is discharged onto a discharge tray 7. When forming images on both sides of the recording material, once the transfer and fixing of the toner image onto the first side (front side) of the recording material is completed, the recording material is turned over via a reversing transport section 10, and the toner image is transferred and fixed onto the second side (rear side) of the recording material, and then stacked onto the discharge tray 7.

[0018] As described above, the control unit 30 controls the entire image forming apparatus 1. The control unit 30 can perform various settings based on input from the operation unit 4 of the image forming apparatus 1. Such a control unit 30 has a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The CPU controls each unit while reading a program corresponding to a control procedure stored in the ROM. The RAM stores working data and input data, and the CPU performs control by referring to the data stored in the RAM based on the above-mentioned programs.

[0019] [Fixing device] Next, the configuration of the fixing device 8 in this embodiment will be described with reference to FIG. 2 and FIG. 3. FIG. 2 is a cross-sectional view showing a schematic configuration of the fixing device 8, and FIG. 3 is a cross-sectional view of the fixing device 8 including the cover 500. In this embodiment, a fixing device of a belt heating type using an endless belt is adopted. In FIG. 2, the X direction indicates the conveying direction of the recording material P, the Y direction indicates the width direction intersecting with the conveying direction of the recording material P (perpendicular in this embodiment), and the Z direction indicates the pressure direction of the pressure roller 305 described later. These are perpendicular to each other. Also, one side of the width direction (Y direction) is the front side of the image forming apparatus 1, for example, the side where the operation unit 4 is arranged and operated by the user. On the other hand, the other side of the width direction is the rear side of the image forming apparatus 1.

[0020] The fixing device 8 includes a heating unit 300 having a fixing belt 301 as an endless rotatable belt, and a pressure roller 305 as a nip portion forming member and pressure rotating body that contacts the fixing belt 301 and forms a nip portion N together with the fixing belt 301.

[0021] The heating unit 300 includes the above-mentioned fixing belt 301, a fixing pad 303 as a pad member, a heating roller 307, and a steering roller 308. The pressure roller 305 rotates in contact with the outer circumferential surface of the fixing belt 301, and is also a driving rotor that applies a driving force to the fixing belt 301.

[0022] The fixing belt 301 as a fixing member and a rotating body has thermal conductivity, heat resistance, etc., and is a thin cylindrical shape. In this embodiment, it has a three-layer structure with a base layer, an elastic layer on the outer periphery of the base layer, and a release layer on the outer periphery of the elastic layer. The base layer is 80 μm thick and made of polyimide resin (PI), the elastic layer is 300 μm thick and made of silicone rubber, and the release layer is 30 μm thick and made of PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin) as a fluororesin. Such a fixing belt 301 is stretched by a fixing pad 303, a heating roller 307, and a steering roller 308.

[0023] The fixing pad 303 is disposed inside the fixing belt 301 so as to face the pressure roller 305 with the fixing belt 301 sandwiched therebetween. The fixing pad 303 forms a nip portion N between the fixing belt 301 and the pressure roller 305 for sandwiching and conveying the recording material. In this embodiment, the fixing pad 303 is a substantially plate-shaped member that is long along the width direction of the fixing belt 301 (the longitudinal direction intersecting the rotation direction of the fixing belt 301, the direction of the rotation axis of the heating roller 307). The fixing pad 303 is pressed against the pressure roller 305 with the fixing belt 301 sandwiched therebetween, thereby forming the nip portion N. The fixing pad 303 is made of LCP (liquid crystal polymer) resin.

[0024] The fixing pad 303 is supported by a stay 302 serving as a support member disposed inside the fixing belt 301. That is, the stay 302 is disposed on the opposite side of the fixing pad 303 from the pressure roller 305, and supports the fixing pad 303. Such a stay 302 is a reinforcing member having long rigidity along the longitudinal direction of the fixing belt 301, and contacts the fixing pad 303 to back up the fixing pad 303. That is, the stay 302 provides strength to the fixing pad 303 to ensure the pressure force at the nip portion N when the fixing pad 303 is pressed by the pressure roller 305.

[0025] A lubricating sheet (not shown) is interposed between fixing pad 303 and fixing belt 301. A lubricant is applied to the inner peripheral surface of fixing belt 301 so that fixing belt 301 slides smoothly against fixing pad 303 covered with the lubricating sheet. Silicone oil is used as the lubricant.

[0026] Heating roller 307 as a first roller is disposed inside fixing belt 301, and stretches fixing belt 301 together with fixing pad 303 and steering roller 308. Heating roller 307 is formed in a cylindrical shape from metal such as aluminum or stainless steel, and has a halogen heater 306 disposed therein as a heating unit for heating fixing belt 301. Heating roller 307 is heated by halogen heater 306 to a predetermined temperature.

[0027] In this embodiment, the heating roller 307 is formed of, for example, a stainless steel pipe having a thickness of 1 mm. The halogen heater 306 may be one or more. The heating unit is not limited to a halogen heater, and may be another heater capable of heating the heating roller 307, such as a carbon heater. The fixing belt 301 is heated by the heating roller 307 heated by the halogen heater 306, and is controlled to a predetermined target temperature according to the type of recording material based on temperature detection by a thermistor (not shown).

[0028] The steering roller 308 is disposed inside the fixing belt 301, stretches the fixing belt 301 together with the fixing pad 303 and the heating roller 307, and rotates in a driven manner with the fixing belt 301. The steering roller 308 tilts with respect to the rotation axis direction (width direction, length direction) of the heating roller 307 to control the position (shift position) of the fixing belt 301 with respect to the rotation axis direction. That is, the steering roller 308 has a rotation center at the center or one end of the rotation axis direction (length direction) of the steering roller 308, and tilts with respect to the length direction of the heating roller 307 by swinging about this rotation center. This generates a tension difference between one side and the other side of the length direction of the fixing belt 301, and moves the fixing belt 301 in the length direction.

[0029] Fixing belt 301 tends to shift to one end during rotation depending on the outer diameter accuracy of the rollers that tension it and the alignment accuracy between the rollers. For this reason, such shifting is controlled by steering roller 308. Note that steering roller 308 may be swung by a driving source such as a motor, or may be configured to swung by automatic centering.

[0030] In this embodiment, the steering roller 308 is biased by a spring supported by the frame of the heating unit 300, and also serves as a tension roller that applies a predetermined tension to the fixing belt 301. The steering roller 308 is formed into a cylindrical shape from a metal such as aluminum or stainless steel. In this embodiment, the steering roller 308 is formed from a stainless steel pipe having an outer diameter of 20 mm. The steering roller 308 may be provided with a rubber material or the like on its surface in order to increase its gripping force on the fixing belt 301.

[0031] The pressure roller 305 rotates in contact with the outer circumferential surface of the fixing belt 301, and applies a driving force to the fixing belt 301. In this embodiment, the pressure roller 305 is a roller having an elastic layer formed on the outer periphery of the shaft, and a release layer formed on the outer periphery of the elastic layer. The shaft is made of stainless steel with a diameter of 72 mm, the elastic layer is made of conductive silicone rubber with a thickness of 8 mm, and the release layer is made of PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin) as a fluororesin with a thickness of 100 μm. The pressure roller 305 is rotatably supported by a fixing frame (not shown) of the fixing device 8, and a gear is fixed to one end thereof, and the pressure roller 305 is connected to a motor M as a pressure roller drive source via the gear, and is driven to rotate.

[0032] In the fixing device 8 configured as above, the toner image is heated while the recording material P carrying the toner image is sandwiched and conveyed in the nip portion N formed between the fixing belt 301 and the pressure roller 305. Then, the toner image is fixed to the recording material P. Therefore, the fixing device 8 needs to have both a function of applying heat and pressure and a function of conveying the recording material P. The pressure roller 305 is pressed against the fixing pad 303 via the fixing belt 301 by a driving source (not shown). In this embodiment, the pressure force (NF) in the nip portion N during image formation is set to 1600 N, and the length of the nip portion N in the X direction (conveyance direction) is set to 24.5 mm, and the length in the Y direction (width direction) is set to 326 mm.

[0033] Further, downstream of the nip portion N in the conveying direction of the recording material P, a discharge unit 350 is disposed for discharging the recording material P that has passed through the nip portion N to the outside of the fixing device 8. The discharge unit 350 is provided with an air nozzle 401, a pair of discharge rollers 400a, and a lower separation guide 400. The air nozzle 401 as a nozzle blows out air (compressed air) for peeling the recording material P from the fixing belt 301. Specifically, the air nozzle 401 is disposed downstream of the nip portion N in the conveying direction of the recording material (hereinafter, sometimes simply referred to as the "conveying direction") and vertically above the nip portion N, and blows out air upstream of the conveying direction and vertically downward. Then, the recording material P is peeled off from the fixing belt 301 by blowing air near the leading end of the recording material P after passing through the nip portion N.

[0034] The lower separation guide 400b is disposed downstream of the nip portion N in the recording material conveying direction and vertically below the nip portion N, with its tip facing closely to the vicinity of the nip portion N of the pressure roller 305. When the recording material P sticks to the pressure roller 305, the lower separation guide 400b separates the recording material P from the pressure roller 305. The lower separation guide 400b also supports the lower surface of the recording material P discharged from the nip portion N and guides the recording material P to the discharge roller 40a. The discharge roller pair 400a discharges the recording material P discharged from the nip portion N to the outside of the fixing device 8. In this embodiment, the discharge roller pair 400a is disposed about 40 mm downstream of the nip portion N in the conveying direction.

[0035] Further, upstream of the nip portion N of the fixing device 8 in the conveying direction, there are disposed a guide portion 94 for guiding the recording material P to the nip portion N, and a detection sensor 95 for detecting the recording material P immediately before the nip portion N. The control portion 30 detects the timing at which the recording material P enters the nip portion N by the detection sensor 95.

[0036] 3, the fixing device 8 has a cover 500 that covers at least the upper part of the fixing belt 301 in the vertical direction. In this embodiment, the cover 500 is arranged so as to cover a part of the periphery including the upper part of the fixing belt 301 and a part of an air path 402 described later. Such a cover 500 constitutes a part of a housing 501 of the fixing device 8 that houses the heating unit 300, the pressure roller 305, the discharge unit 350, etc.

[0037] [Air nozzle and air path] Next, the air nozzle 401 and the air path 402 will be described in detail with reference to FIG. 3 and FIG. 4 to FIG. 6. The air nozzle 401 is an aluminum alloy member arranged facing the fixing belt 301 so that the longitudinal direction is along the width direction of the fixing belt 301, as shown in FIG. 4. The air nozzle 401 has about 30 to 50 nozzle holes 401a with a diameter of about 0.5 to 1.0 mm on the surface facing the fixing belt 301, as shown in FIGS. 5(a) and 5(b). Compressed air generated by the air compressor 96a passes through the air path 402 and is guided to the space inside the air nozzle 401 from an air nozzle inlet 401b provided in the air nozzle 401, and is discharged from the nozzle hole 401a. The air nozzle inlet 401b opens at one end of the air nozzle 401 in the longitudinal direction.

[0038] 4 and 6, the air path 402 as a flow path member is disposed inside a housing 501 of the fixing device 8. As shown in FIG. 4, the air path 402 includes a fixing side coupler 402a, a piping member (air heating unit) 402b, an air tube 402c, a tube joint 402d, an air pipe 402e, and the like.

[0039] The fixing side coupler 402a is provided at the inlet of the air path 402, and is a piping coupling member that can be detached from the main body side coupler 96f (described later) in order to supply compressed air supplied from the air compressor 96a (described later) into the air path 402. The fixing side coupler 402a is attached to one end of the piping member 402b as a part of the flow path member. A plurality of tube joints 402d and air tubes 402c are connected to the other end of the piping member 402b to form the air path 402, which is a continuous air flow path. An air pipe 402e is attached to the most downstream of the air path 402 and is connected to an air nozzle inlet 401b provided in the air nozzle 401. The air path 402 configured in this manner guides the compressed air flowing in from the fixing side coupler 402a to the space inside the air nozzle 401 via the piping member 402b, the air tube 402c, etc.

[0040] The piping member 402b and the air tube 402c are rubber tubes made of a heat-resistant material such as silicone rubber, with an inner diameter of about φ9 mm and a thickness of about 1 mm. The tube joint 402d is made of an aluminum alloy or a heat-resistant resin, for example. The tube joint 402d is a component that bends the flow path, and by arranging the tube joint 402d between the piping member 402b and the air tube 402c or between two air tubes 402c, the piping member 402b and the air tube 402c can be routed in various directions without bending or buckling.

[0041] 6 is a schematic diagram showing the path from the air compressor 96a to the air nozzle 401 viewed from above inside the image forming apparatus 1. Inside the image forming apparatus main body 3 of the image forming apparatus 1, there are provided the air compressor 96a, a piping tube 96g, a pressure release solenoid valve 96b, a pressure adjustment valve 96c, an air filter 96d, a spray solenoid valve 96e, a main body side coupler 96f, and the like.

[0042] The air compressor 96a generates compressed air. The piping tube 96g connects the air compressor 96a to an air path 402 provided inside the housing 501 of the fixing device 8. The pressure release solenoid valve 96b is used to release the pressure in the piping tube 96g. The pressure adjustment valve 96c adjusts and maintains the pressure in the piping tube 96g at a predetermined pressure. The air filter 96d separates and removes drainage, dust, and dirt in the piping tube 96g. The blowing solenoid valve 96e is a valve for sending compressed air to the air nozzle 401 and blowing the compressed air against the tip of the recording material P. The main body side coupler 96f is a coupling member connected to the fixing side coupler 402a. With this configuration, the air generated by the air compressor 96a and passing through the piping tube 96g is supplied to the above-mentioned air path 402.

[0043] The air blowing operation is performed as follows. First, the air compressor 96a is started, and then the pressure release solenoid valve 96b is closed, whereby compressed air with a pressure adjusted by the pressure adjustment valve 96c is accumulated inside the piping tube 96g up to the spray solenoid valve 96e. In this embodiment, the pressure adjustment valve 96c is adjusted so that the pressure inside the piping tube 96g is 0.2 to 0.3 MPa.

[0044] When the recording material P is fed into the fixing device 8, the detection sensor 95 detects the leading edge of the recording material P. Using that timing as a reference, the blowing solenoid valve 96e is opened after a predetermined time has elapsed, whereby compressed air accumulated in the piping tube 96g is blown onto the leading edge of the recording material P, causing the recording material P to be peeled off from the fixing belt 301.

[0045] Such blowing of compressed air is performed within a range of about 90 mm from the leading edge of the recording material P. That is, air is blown from the air nozzle 401 for the period until the recording material P, whose leading edge has passed through the nip portion N, is separated from the fixing belt 301 by about 90 mm, in other words, until the leading edge of the recording material P is conveyed about 90 mm from the exit of the nip portion N. This is because if the blowing period is long, the air pressure inside the piping tube 96g may not be sufficiently increased before the next recording material is separated, and if the blowing period is short, there is a risk that the recording material may not be sufficiently separated.

[0046] For example, if the length of the recording material P to be separated from the fixing belt 301 is set to 150 mm or more, the air nozzle 401 will continue to blow air for a longer period of time than if the length was set to 90 mm, and there is a possibility that the time to compress the air to separate the next recording material from the fixing belt 301 will be insufficient. This 150 mm is the length in the conveying direction of the recording material of the smallest size on which an image can be formed by the image forming apparatus 1. On the other hand, for example, if the length of the recording material P to be separated from the fixing belt 301 is set to 40 mm, the separation ability will be insufficient. This 40 mm is the length in the conveying direction from the exit of the nip portion N to the pair of discharge rollers 400a. In this embodiment, by blowing air from the air nozzle 401 until the recording material P is nipped by the pair of discharge rollers 400a, it is possible to prevent the intermediate portion of the recording material P in the conveying direction from being wrapped around the fixing belt 301 halfway. From the above, in this embodiment, the length of the recording material P to be separated from the fixing belt 301 is set to 90 mm, which is the middle of these two values.

[0047] [Position of piping components] Next, the position of the piping member 402b, which is a part of the air path 402, will be described with reference to Figs. 2 to 4. As described above, in this embodiment, the recording material is peeled off from the fixing belt 301 by blowing air from the air nozzle 401. Here, if the temperature of the blown air is low, the toner image on the recording material may be cooled. The glossiness of the cooled toner image changes depending on the cooling temperature, so there is a risk of uneven gloss occurring in the toner image.

[0048] Particularly in this embodiment, the air nozzle 401 is arranged such that its longitudinal direction runs along the width direction of the fixing belt 301, and a plurality of nozzle holes 401a are formed on the surface facing the fixing belt 301. By providing a plurality of small-diameter nozzle holes 401a in this manner, compressed air with high air pressure and volume is blown onto the recording material.

[0049] On the other hand, the toner image on the recording material onto which compressed air is blown is rapidly cooled when low-temperature air is blown onto it. The wind pressure and volume of the blown compressed air are higher the closer to the nozzle hole 401a in the width direction. That is, a temperature distribution occurs in the toner image on the recording material in the width direction due to the cooling of the compressed air according to the position of the nozzle hole 401a. The glossiness of the cooled toner image changes slightly depending on the cooling temperature, and a gloss distribution occurs in the width direction.

[0050] In recent years, with the increase in the speed of devices and the diversification of media such as ultra-thin paper, measures have been taken to further improve peeling performance, such as moving the air nozzle 401 even closer to the fixing belt 301 and increasing the wind pressure of the compressed air. When such measures are taken, the temperature distribution in the width direction of the toner image on the recording material becomes larger. As a result, a gloss distribution according to the temperature distribution may occur at a visible level (called nozzle pitch unevenness). Therefore, in this embodiment, the piping member 402b, which is a part of the air path 402, is arranged as follows to heat the air blown from the air nozzle 401 and suppress the above-mentioned gloss unevenness of the toner image.

[0051] The piping member 402b is disposed above the fixing belt 301 in the vertical direction and in a range overlapping with the fixing belt 301 when the fixing belt 301 is viewed from above. In other words, the piping member 402b is disposed within a silhouette S obtained by projecting the upper surface of the fixing belt 301 upward as shown in FIG. 2. The piping member 402b is also disposed between the fixing belt 301 and the cover 500 as shown in FIG. 3. It is preferable that the piping member 402b and the fixing belt 301 face each other without any obstacles. However, the piping member 402b may be covered with a nonwoven fabric or the like, or a member that blocks a part of the space between the piping member 402b and the fixing belt 301, such as a frame of the fixing device 8, may be disposed between the piping member 402b and the fixing belt 301. When such a blocking member is present, it is preferable that the blocking area is small. In short, in this embodiment, it is only necessary that the piping member 402b is disposed above the fixing belt 301 so that the piping member 402b is heated by the heat generated from the fixing belt 301.

[0052] 4, the piping member 402b is arranged along the width direction intersecting the recording material conveying direction. In this embodiment, the piping member 402b is arranged approximately parallel to the longitudinal direction of the fixing belt 301. Specifically, the piping member 402b is arranged along the width direction (Y direction) from the rear side to the front side of the image forming apparatus 1 inside the cover 500 of the fixing device 8. This allows the length of the piping member 502b facing the fixing belt 301 to be longer than when the piping member 502b is arranged parallel to the recording material conveying direction, for example, and the air passing through the piping member 402b can be efficiently heated by the heat of the fixing belt 301.

[0053] The length of the piping member 402b is preferably shorter than the length of the fixing belt 301 in the longitudinal direction, and the piping member 402b is preferably disposed so that the entirety of the piping member 402b falls within the range overlapping with the fixing belt 301 when the fixing belt 301 is viewed from above. This is because, if a part of the piping member 402b is out of the range overlapping with the fixing belt 301, there is a risk that the air will be cooled in that part.

[0054] 2, the piping member 402b is located downstream in the rotation direction of the fixing belt 301 from the highest position in the vertical direction of the fixing belt 301. As a result, the air that is heated around the fixing belt 301 and flows along the rotation direction of the fixing belt 301 hits the piping member 402b, so that the piping member 402b is efficiently heated.

[0055] Particularly, in this embodiment, the fixing belt 301 is stretched by the fixing pad 303, the heating roller 307, and the steering roller 308 as described above. Among these stretching members, the heating roller 307 as a first roller is located at the highest position. The steering roller 308 as a second roller is disposed downstream of the heating roller 307 in the rotation direction of the fixing belt 301 and upstream of the nip portion N (i.e., upstream of the fixing pad 303). The piping member 402b is disposed between the heating roller 307 and the steering roller 308 in the rotation direction of the fixing belt 301. Therefore, the air heated by the heating roller 307 can be efficiently sent to the piping member 402b side by the rotation of the fixing belt 301.

[0056] In addition, in this embodiment, the steering roller 308 is located below the highest position (apex) of the heating roller 307, and the piping member 402b is located between the heating roller 307 and the steering roller 308 in the rotation direction of the fixing belt 301. Therefore, the piping member 402b can be disposed at a height similar to or below the apex of the heating roller 307. As a result, even if the piping member 402b is disposed above the fixing belt 301, it is possible to prevent the piping member 402b from protruding above the highest position of the fixing belt 301, and it is possible to prevent the device from becoming large.

[0057] In the present embodiment configured as described above, in a configuration in which air is blown to peel off the recording material from the fixing belt 301, it is possible to suppress the occurrence of gloss unevenness in the toner image. That is, in the present embodiment, the piping member 402b, which is a part of the air path 402, is disposed above the fixing belt 301. Therefore, air heated by the radiant heat of the fixing belt 301 rises, and the piping member 402b is heated by this air. In the present embodiment, while the image forming apparatus 1 is in operation, the piping member 402b is heated to about 80 to 100°C by the heat from the fixing belt 301. Then, the air flowing through the piping member 402b is also heated, and the warm air can be blown from the air nozzle 401 toward the recording material. As a result, it is possible to reduce the temperature distribution caused by the air blown from the air nozzle 401, and it is possible to suppress the occurrence of gloss unevenness.

[0058] [Example] An experiment was conducted to confirm the effect of the configuration of the present embodiment as described above. In the experiment, the temperature distribution on the recording material was measured when air was blown onto the recording material from the air nozzle 401 in an example in which the piping member 402b was arranged above the fixing belt 301 as in the present embodiment as described above, and in a comparative example in which the piping member 402b was not arranged above the fixing belt 301.

[0059] In the embodiment, the compressed air ejected from air nozzle 401 is heated to about 60 to 70° C. by passing through piping member 402b heated to about 80 to 100° C. The compressed air is then cooled slightly by passing through air tube 402c and tube joint 402d downstream thereof, the temperature of which drops to about 42° C., and the air is guided through air nozzle inlet 401b into the space inside air nozzle 401. On the other hand, when no portion heated by fixing belt 301 is provided in air path 402 as in the comparative example, compressed air at about 30° C. is guided into air nozzle 401.

[0060] FIG. 7 shows the temperature distribution on the recording material P immediately after the compressed air is blown onto the recording material P in the embodiment and the comparative example. As shown in FIG. 7, the temperature of the recording material P decreased more toward the position corresponding to the nozzle hole 401a of the air nozzle 401. As in the comparative example, when the compressed air temperature guided to the air nozzle 401 is 30° C., the difference ΔT between the adjacent maximum temperature portion and the minimum temperature portion was a maximum of 19.0° C. On the other hand, in the embodiment, the compressed air temperature guided to the air nozzle 401 is 42° C., and ΔT was a maximum of 9.3° C. As is clear from FIG. 7, in this embodiment, the distribution of glossiness occurring in the toner image on the recording material P is suppressed, and it is possible to improve the nozzle pitch unevenness to a level where it is not visible.

[0061] <Second embodiment> The second embodiment will be described with reference to Figures 8 and 9. In the above-described first embodiment, the fixing member is a fixing belt 301. In contrast, in this embodiment, the fixing member is a fixing roller 310. Since other configurations and functions are similar to those of the above-described first embodiment, the same configurations are denoted by the same reference numerals, and explanations and illustrations thereof will be omitted or simplified, and the following description will focus on the points that are different from the first embodiment.

[0062] The fixing device 8A in this embodiment has a fixing roller 310 as a fixing member and a heating rotator, and the fixing roller 310 is in pressure contact with the pressure roller 305 to form a nip portion N. The fixing roller 310 has a cylindrical metal (in this embodiment, made of aluminum) core having an outer diameter of 77 mm, a thickness of 6 mm, and a length of 350 mm. The core is coated with silicone rubber (in this embodiment, JIS-A hardness 20 degrees) to a thickness of 1.5 mm as a heat-resistant elastic layer. The elastic layer is coated with fluorine-based resin (in this embodiment, PFA tube) to a thickness of 50 μm as a heat-resistant release layer to improve releasability from the toner.

[0063] The fixing roller 310 is rotatably supported by a frame of the fixing device 8A (not shown) and is rotated at a predetermined peripheral speed by a driving source (not shown). The fixing roller 310 is provided with a halogen heater 306 as a heating unit therein, and is capable of generating heat up to a predetermined temperature.

[0064] The air nozzle 401 and the air path 402 of this embodiment are the same as those of the first embodiment. Also in this embodiment, the piping member 402b as part of the air path 402 is disposed vertically above the fixing roller 310 and in a range overlapping with the fixing roller 310 when the fixing roller 310 is viewed from above. In other words, the piping member 402b is disposed within a silhouette S obtained by projecting the upper surface of the fixing roller 310 upward as shown in Fig. 8. Also, the piping member 402b is disposed between the fixing roller 310 and the cover 500 (see Fig. 3) of the fixing device 8A as in the first embodiment.

[0065] 9, the piping member 402b is disposed along the width direction intersecting the conveying direction of the recording material. Furthermore, as shown in FIG. 8, the piping member 402b is located downstream in the rotation direction of the fixing roller 310 from the highest position (vertex) of the fixing roller 310 in the vertical direction.

[0066] In the present embodiment configured as described above, it is also possible to suppress the occurrence of gloss unevenness in a toner image in a configuration in which air is blown to peel off the recording material from the fixing roller 310. That is, in the present embodiment as well, the piping member 402b, which is a part of the air path 402, is disposed above the fixing roller 310. Therefore, the air heated by the fixing roller 310 rises, and the piping member 402b is heated by this air. Then, the air flowing through the piping member 402b is also heated, and the warm air can be blown from the air nozzle 401 toward the recording material. As a result, it is possible to reduce the temperature distribution caused by the air blown from the air nozzle 401, and it is possible to suppress the occurrence of gloss unevenness.

[0067] <Other embodiments> In the above-mentioned first embodiment, a configuration in which a halogen heater is provided on the heating roller as a heating unit for heating the fixing belt has been described. However, the heating unit may not be provided on the heating roller, but may be provided on another tension member such as a steering roller. Also, it may be provided on a pad member. For example, a plate-shaped heat generating member such as a ceramic heater may be provided on the fixing belt side of the pad member. Also, the fixing belt may be heated by electromagnetic induction (IH). Also, in the above-mentioned first and second embodiments, instead of the heating unit arranged inside the roller, an external heating method may be adopted in which a separate heating member is brought into contact with the belt or roller from the outside to heat it.

[0068] In the above-described first embodiment, a fixing device in which the fixing belt is stretched by a fixing pad, a heating roller, and a steering roller has been described. However, the fixing device to which the present invention is applicable is not limited to this, and may be configured such that the fixing belt is stretched by only one tension roller and a fixing pad. In short, it is sufficient to have at least one tension roller that stretches the fixing belt together with the fixing pad.

[0069] In the first embodiment, a pressure roller is used as the driving rotor. However, the driving rotor may be an endless belt that is stretched by a plurality of tension rollers and driven by any of the tension rollers. In each of the above embodiments, the pressure roller as the driving rotor presses the belt to form the nip portion, but the belt may be pressed against the driving rotor.

[0070] Furthermore, in each of the above-described embodiments, the piping member 402b as part of the air path 402 is arranged above the fixing belt 301 and fixing roller 310 as fixing members, but it may be arranged above a member that does not directly touch the recording material, such as an external heating method. For example, in a configuration in which an external heating belt is brought into contact with the fixing belt 301 or fixing roller 310 and a heating unit is arranged inside a roller around which the external heating belt is stretched, the piping member 402b is arranged vertically above the external heating belt and in a range that overlaps with the external heating belt when viewed from above. The same applies when an external heating roller having a heating unit inside is brought into contact with the fixing belt 301 or fixing roller 310.

[0071] The disclosure of this embodiment also includes the following configuration.

[0072] (Configuration 1) a fixing device including a fixing member for heating a toner image carried on a recording material to fix the toner image on the recording material, a heating section for heating the fixing member, a nip portion forming member for forming a nip portion between the fixing member and the fixing member for nipping and conveying the recording material, and a nozzle for blowing air to peel the recording material off from the fixing member; a flow path member for sending air to the nozzle, A portion of the flow path member is disposed vertically above the fixing member and in a range overlapping with the fixing member when the fixing member is viewed from above. 1. An image forming apparatus comprising: (Configuration 2) the fixing device has a cover that covers at least a vertically upper portion of the fixing member, A portion of the flow path member is disposed between the fixing member and the cover. 2. The image forming apparatus according to claim 1, (Configuration 3) A portion of the flow path member is disposed along a width direction intersecting a conveying direction of the recording material conveyed through the nip portion. 3. The image forming apparatus according to claim 1, wherein the first and second components are arranged in a same plane. (Configuration 4) the fixing member is a rotating body, A portion of the flow path member is located downstream in a rotation direction of the fixing member from a highest position in a vertical direction of the fixing member. 4. The image forming apparatus according to any one of configurations 1 to 3, (Configuration 5) The fixing member is an endless belt. 5. The image forming apparatus according to any one of configurations 1 to 4. (Configuration 6) the fixing device includes a first roller that stretches the belt, and a second roller that stretches the belt downstream of the first roller in a rotation direction of the belt and upstream of the nip portion, A portion of the flow path member is disposed between the first roller and the second roller in the rotation direction of the belt. 6. The image forming apparatus according to configuration 5. (Configuration 7) the first roller is a heating roller having the heating unit therein, and the first roller is heated by the heating unit to heat the belt; The second roller is a steering roller that controls the position of the belt in a width direction that intersects with the rotation direction of the belt. 7. The image forming apparatus according to configuration 6, (Configuration 8) The fixing member is a roller. 5. The image forming apparatus according to any one of configurations 1 to 4. (Configuration 9) The roller has the heating portion therein. 9. The image forming apparatus according to configuration 8, (Configuration 10) The nozzle has a plurality of holes formed therein for blowing air in a width direction intersecting with a conveying direction of the recording material conveyed in the nip portion. 10. The image forming apparatus according to any one of configurations 1 to 9, [Explanation of symbols]

[0073] 8, 8A... Fixing device 301 Fixing belt (fixing member, rotating body) 305 Pressure roller (nip forming member) 306 Halogen heater (heating part) 307 Heating roller (first roller) 308···Steering roller (second roller) 310: Fixing roller (fixing member, rotating body) 401 Air nozzle (nozzle) 401a Nozzle hole 402 Air path (flow path member) 402b Piping member (part of flow path member) 500···Cover

Claims

1. A first rotating body that heats a toner image carried on a recording material; a second rotating body that contacts the first rotating body to form a nip portion; a nozzle configured to blow air toward the recording material and the first rotating body, the nozzle being disposed downstream of the nip portion with respect to a conveying direction of the recording material conveyed through the nip portion; a fixing device having a flow path member configured to guide air to the nozzle; Equipped with The flow path member extends along a width direction of the first rotating body that intersects with a conveying direction of the recording material, and includes an area that overlaps with the first rotating body when the first rotating body is viewed from above. An image forming apparatus characterized by:

2. the fixing device has a cover that covers at least a vertically upper portion of the first rotating body, The area of ​​the flow path member that overlaps with the first rotating body is disposed between the first rotating body and the cover.

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

3. A part of the flow path member is located downstream in the rotation direction of the first rotor than the highest position in the vertical direction of the first rotor.

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

4. The image forming apparatus further includes a compressor configured to discharge the generated compressed air from the nozzle.

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

5. The compressor is located downstream of the first rotor in the direction of rotation of the first rotor.

5. The image forming apparatus according to claim 4.

6. The connection position between the nozzle and the flow path member is located upstream of the second rotating body in the rotation direction of the first rotating body.

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

7. The first rotating body is an endless belt.

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

8. the fixing device includes a first roller that stretches the belt, and a second roller that stretches the belt downstream of the first roller in a rotation direction of the belt and upstream of the nip portion, A portion of the flow path member is disposed between the first roller and the second roller in the rotation direction of the belt.

8. The image forming apparatus according to claim 7,

9. the first roller is a heating roller having a heating section therein, and the first roller is heated by the heating section, thereby heating the belt; The second roller is a steering roller that controls the position of the belt in the width direction that intersects with the rotation direction of the belt.

9. The image forming apparatus according to claim 8,

10. The nozzle has a plurality of holes formed therein for blowing air in a width direction intersecting with a conveying direction of the recording material conveyed in the nip portion.

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

Images