JP7310331B2 - image forming device - Google Patents

Description

The present invention relates to an image forming apparatus. More particularly, the present invention relates to an image forming apparatus that appropriately cools a pressurizing rotator.

Electrophotographic image forming apparatuses include multi-function peripherals (MFPs), facsimile machines, copiers, printers, etc., each of which has a scanner function, a facsimile function, a copying function, a printer function, a data communication function, and a server function. include.

Some electrophotographic image forming apparatuses use an optical writing device to scan exposure light onto a photoreceptor to form an electrostatic latent image. This image forming apparatus develops an electrostatic latent image using a developing device. A toner image is formed by development. This image forming apparatus transfers a toner image onto a recording medium. This image forming apparatus uses a fixing device to fix a toner image on a recording medium. Thus, an image is formed on the recording medium.

Some fuser devices include a fuser rotator, a heating member, and a pressure rotator. The fixing rotator heats the toner image to fix the toner image on the recording medium. The heating member heats the fixing rotator. The pressing rotator presses the fixing rotator to form a nip portion through which the recording medium passes together with the fixing rotator. This type of fixing device blows air to the surface of the pressure rotating body as necessary to cool the surface of the pressure rotating body. The reason for cooling the surface of the pressurizing rotor is to suppress hot offset, expansion of the pressurizing rotor, deterioration of the pressurizing rotor, and the like, which are caused by the temperature rise of the surface of the pressurizing rotor.

A conventional technique for cooling the surface of a pressurizing rotating body is disclosed, for example, in Patent Document 1 below. Japanese Unexamined Patent Application Publication No. 2002-200000 discloses an image forming apparatus that includes three cooling mechanisms and two air regulating plates. The three cooling mechanisms apply air to the outer peripheral surface of the pressure roller to cool it. The two air regulating plates restrict the direction or amount of air flowing before it hits the outer peripheral surface of the pressure roller. Also, the two air regulating plates restrict the direction or amount of flow of the air after being applied to the outer peripheral surface. The tip portions of the two air regulating plates face the outer peripheral surface of the pressure roller with a gap therebetween. These tip portions are formed so as to follow the shape of the outer peripheral surface of the pressure roller. The three cooling mechanisms have the same shape. Each of the three cooling mechanisms cools different locations in the width direction of the pressure roller.

JP 2017-111162 A

A CD (Cross Direction) direction is defined as a direction perpendicular to the conveying direction of a recording medium, which traverses the conveyed recording medium. The temperature distribution along the CD direction of the pressing rotator during fixing becomes non-uniform. This non-uniform temperature distribution is caused by the width of the recording medium to be fixed in the CD direction or the width of the heating member in the CD direction.

On the other hand, in the technique of Patent Document 1, the surface of the pressure roller is cooled by each of the three identical cooling mechanisms arranged in the CD direction. During this cooling, the surface of the pressure roller is cooled with a uniform cooling amount along the CD direction. For this reason, relatively high-temperature portions in the CD direction are not sufficiently cooled. On the other hand, the relatively cold parts in the CD are over-cooled. As described above, the technique of Patent Document 1 has a problem that the pressurizing rotating body cannot be cooled appropriately.

As a method of reliably cooling the high-temperature portion, a method of increasing the velocity of the wind applied to the relatively high-temperature portion in the CD direction is conceivable. However, with this method, the wind that cools the surface of the pressure roller is too strong and winds around the fixing rotating body. As a result, there arises a problem that unnecessary portions of the fixing device are cooled.

The present invention is intended to solve the above problems. SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus that appropriately cools a pressure rotating member.

An image forming apparatus according to one aspect of the present invention includes a fixing rotator for heating and fixing a toner image onto a recording medium, a heating member for heating the fixing rotator, and a recording medium by pressing the fixing rotator. A pressurizing rotator comprising a pressure rotator forming a passing nip portion together with the fixing rotator, a fan for blowing air, and a duct forming a flow path for the air flow by the fan between the pressure rotator and the surface of the pressure rotator. The velocity of the air flowing between the surface of the body and the duct varies along the CD direction, which is a direction perpendicular to the conveying direction of the recording medium and transverse to the conveyed recording medium. The duct is provided along the surface of the pressurizing rotor, and comprises a main body portion that forms a flow path of the air by the fan between the surface of the pressurizing rotor and the surface of the pressurizing rotor and the main body portion. and a partition that divides the outlet into a plurality of openings arranged in the CD direction.
An image forming apparatus according to another aspect of the present invention includes a fixing rotator that heats a toner image to fix it on a recording medium, a heating member that heats the fixing rotator, and a recording medium that presses the fixing rotator. A pressure rotating body comprising a pressure rotating body forming a passing nip portion together with the fixing rotating body, a fan for generating wind, and a duct forming a flow path for the air flow by the fan between the pressure rotating body and the surface of the pressure rotating body, and rotating under pressure. The velocity of the air flowing between the surface of the body and the duct varies along the CD direction, which is a direction perpendicular to the conveying direction of the recording medium and transverse to the conveyed recording medium. The duct is provided along the surface of the pressurizing rotor, and comprises a main body portion that forms a flow path of the air by the fan between the surface of the pressurizing rotor and the surface of the pressurizing rotor and the main body portion. and a partition for dividing the outlet into a plurality of openings arranged in the CD direction. Each of the plurality of circulating portions is a flow path for air that extends along the rotational direction on the surface of the main body on the side of the pressure rotating body and that flows between the surface of the pressure rotating body and the main body. is divided into a plurality of circulation portions corresponding to each of the plurality of openings, and the minimum distance between some of the plurality of circulation portions and the surface of the pressure rotating body, The minimum distance of the section from one end to the other end of the flow-through portion along the direction of rotation of the body is different from the minimum distance of other flow-through portions among the plurality of flow-through portions.
In the image forming apparatus described above, preferably, the speed of the wind flowing through each of the plurality of flow portions increases as the minimum distance decreases.
An image forming apparatus according to still another aspect of the present invention includes a fixing rotator that heats and fixes a toner image onto a recording medium, a heating member that heats the fixing rotator, and a recording medium by pressing the fixing rotator. a pressure rotator forming a nip portion together with the fixing rotator through which the pressure passes; a fan for generating wind; The speed of the air flowing between the surface of the rotating body and the duct varies along the CD direction, which is a direction perpendicular to the conveying direction of the recording medium and crosses the conveyed recording medium. The duct is provided along the surface of the pressurizing rotor, and comprises a main body portion that constitutes a flow path for air flow by the fan between the surface of the pressurizing rotor and the surface of the pressurizing rotor and the main body portion. and a partition that divides the discharge port into a plurality of openings arranged in the CD direction, each of the plurality of openings Each of the plurality of openings is divided into a plurality of sections by the wire, and the average area of each of the plurality of sections in some of the plurality of openings is , is different from the average area of each of the plurality of compartments at other openings of the plurality of openings.
Preferably, in the above image forming apparatus, the velocity of the wind flowing through each of the plurality of openings is higher as the average area of each of the plurality of sections is smaller.

In the image forming apparatus described above, preferably, the duct is a projecting portion projecting from the body portion toward the surface of the pressure rotating body, and is an outlet for discharging air flowing between the surface of the pressure rotating body and the body portion. It further includes protrusions that lead to.

The image forming apparatus preferably further includes a sensor that detects the temperature of the fixing rotator and is provided at a position corresponding in the CD direction to the opening through which the air flows at the slowest speed among the plurality of openings.

Preferably, in the above image forming apparatus, the sensor is provided at a position corresponding in the CD direction to a position on the surface of the pressurizing rotator where the recording medium does not pass.

In the above image forming apparatus, the heating member preferably stops heating the fixing rotator when the temperature detected by the sensor exceeds a predetermined temperature.

The image forming apparatus preferably further includes a windbreak member that is provided upstream of the sensor in the rotation direction of the fixing rotator and that reduces wind generated by the fan that hits the sensor.

In the above image forming apparatus, preferably, the height along the direction of rotation of the pressure rotating body of some of the plurality of openings is equal to the height of the pressure rotating body of the other openings of the plurality of openings. Different from the height along the direction of rotation.

In the above image forming apparatus, preferably, the velocity of the wind flowing through each of the plurality of openings increases as the height decreases.

In the above-described image forming apparatus, preferably, the air inlet from the fan is composed of the pressurizing rotator and the downstream end of the main body along the rotational direction of the pressurizing rotator, and the outlet is preferably the inlet. is provided on the upstream side in the rotational direction of the pressure rotating body.

The image forming apparatus preferably further includes a shutter for adjusting the area of the surface of the pressure rotating member to which air is blown by the fan according to the width in the CD direction of the recording medium passing through the nip portion.

Preferably, in the above image forming apparatus, there are a plurality of ducts, each of the plurality of ducts is arranged along the CD direction, and includes a center position of the pressure rotating body in the CD direction. They are provided at symmetrical positions across a plane perpendicular to the axis.

Preferably, in the above image forming apparatus, the heating member heats the entire region of the fixing rotator in the CD direction and having a width greater than the width in the CD direction of the recording medium passing through the nip portion.

In the above image forming apparatus, preferably, the heating member changes the width in the CD direction of the region of the fixing rotator to be heated according to the width in the CD direction of the recording medium passing through the nip portion.

According to the present invention, it is possible to provide an image forming apparatus that appropriately cools the pressing rotator.

1 is a cross-sectional view schematically showing the configuration of an image forming apparatus 1 according to an embodiment of the invention; FIG. 2 is a cross-sectional view schematically showing the configuration of a fixing device 30 and the configuration of members in the vicinity of the fixing device 30 according to one embodiment of the present invention; FIG. 3 is a layout diagram showing the positional relationship between each member constituting fixing device 30 and members near fixing device 30 according to an embodiment of the present invention. FIG. 4 is a perspective view schematically showing the configuration of a duct 40A; FIG. It is a figure which shows the shape of one part of duct 40A in one embodiment of this invention. 4 is a diagram showing the relationship between the width in the CD direction of a sheet passing through the nip portion NP and the method of cooling the surface of the pressure roller 38. FIG. It is a figure explaining the 1st modification of one embodiment of this invention. It is a figure explaining the 2nd modification of one embodiment of this invention. FIG. 4 is a diagram showing changes in height H in the CD direction of each of Comparative Example A, Comparative Example B, and Invention Example C in one example of the present invention. 4 is a table showing measurement results of various numerical values of Comparative Example A, Comparative Example B, and Invention Example C in one example of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

In the drawings, the direction from the left side to the right side in FIG. 1 is the x-axis direction, the direction from the front side to the back side of the paper surface in FIG. 1 is the y-axis direction, and the upward direction in FIG. 1 is the z-axis direction. The x-axis direction, y-axis direction, and z-axis direction are orthogonal to each other.

In the following embodiments, a case where the image forming apparatus is an MFP will be described. The image forming apparatus may be an MFP, a printer, a facsimile machine, a monochrome copier, a color copier, or the like.

FIG. 1 is a cross-sectional view schematically showing the configuration of an image forming apparatus 1 according to one embodiment of the invention.

Referring to FIG. 1, image forming apparatus 1 in the present embodiment is an MFP. The image forming apparatus 1 mainly includes a sheet conveying section 10 , a toner image forming section 20 , a fixing device 30 and a control section 70 .

The paper transport section 10 transports the paper along a transport path (transport direction) TR. The paper transport section 10 includes a paper feed tray 11 , paper feed rollers 12 , registration rollers 13 , paper discharge rollers 14 , and a paper discharge tray 15 . The paper feed tray 11 accommodates paper (an example of a recording medium) SH for forming an image. A plurality of paper feed trays 11 may be provided. The paper feed roller 12 is provided between the paper feed tray 11 and the transport path TR. The registration rollers 13 are provided upstream of the secondary transfer rollers 28 in the transport path TR. The paper discharge roller 14 is provided at the most downstream position of the transport path TR. The paper discharge tray 15 is provided at the top of the main body 1 a of the image forming apparatus 1 .

The toner image forming unit 20 synthesizes four-color toner images of Y (yellow), M (magenta), C (cyan), and K (black) by a so-called tandem method. The toner image forming section 20 forms the combined toner image on the conveyed paper. The toner image forming section 20 includes four image forming units 20</b>A, an intermediate transfer belt 26 , four primary transfer rollers 27 , a secondary transfer roller 28 and a cleaning device 29 . Each of the four image forming units 20A is provided for each color of YMCK. Each of the four primary transfer rollers 27 is also provided for each color of YMCK.

The four image forming units 20A are arranged along the intermediate transfer belt 26 . Each of the four image forming units 20A includes a photosensitive drum 21, a charging device 22, an exposure device 23, a developing device 24, a cleaning device 25, and the like. The photosensitive drum 21 is rotationally driven in the direction indicated by the arrow α in FIG. A charging device 22 , a developing device 24 , and a cleaning device 25 are provided around the photosensitive drum 21 .

The intermediate transfer belt 26 is provided above the four image forming units 20A. The intermediate transfer belt 26 has an annular shape. The intermediate transfer belt 26 is stretched over a rotating roller 26a. The intermediate transfer belt 26 is rotationally driven in the direction indicated by the arrow β in FIG. Each of the four primary transfer rollers 27 faces the photosensitive drum 21 with the intermediate transfer belt 26 interposed therebetween. The secondary transfer roller 28 is in contact with the intermediate transfer belt 26 on the transport path TR. Cleaning device 29 is in contact with the surface of intermediate transfer belt 26 .

The fixing device 30 conveys the sheet on which the toner image is formed along the conveying path TR. During this transportation, the fixing device 30 grips the sheet on which the toner image is formed by the fixing nip. Thereby, the fixing device 30 fixes the toner image on the paper.

The control unit 70 controls the operation of the image forming apparatus 1 as a whole. The control unit 70 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like.

The image forming apparatus 1 uniformly charges the surface of the rotating photosensitive drum 21 to a predetermined potential. This charging is performed using the charging device 22 . The image forming apparatus 1 exposes the charged area on the surface of the photosensitive drum 21 based on the image data. An electrostatic latent image is formed on the surface of the photosensitive drum 21 . This exposure is performed using the exposure device 23 .

Next, the image forming apparatus 1 supplies toner to the surface of the photosensitive drum 21 from the developing device 24 . This develops the electrostatic latent image. A toner image is formed on the surface of the photosensitive drum 21 .

Next, the image forming apparatus 1 transfers the toner image formed on the surface of the photosensitive drum 21 to the surface of the intermediate transfer belt 26 (primary transfer). This primary transfer is performed using a primary transfer roller 27 . During this primary transfer, a bias is applied to the primary transfer roller 27 to attract the toner. In the case of a full-color image, toner images of YMCK colors are synthesized on the surface of the intermediate transfer belt 26 .

After the primary transfer, toner that has not been transferred to the intermediate transfer belt 26 remains on the surface of the photosensitive drum 21 . The image forming apparatus 1 removes toner remaining on the surface of the photosensitive drum 21 . Residual toner is removed using the cleaning device 25 .

Subsequently, the image forming apparatus 1 conveys the toner image formed on the surface of the intermediate transfer belt 26 to a position facing the secondary transfer roller 28 . The toner image is conveyed by rotating the intermediate transfer belt 26 following the rotation of the rotating roller 26a.

On the other hand, the image forming apparatus 1 feeds the plurality of sheets SH accommodated in the sheet feed tray 11 one by one to the transport path TR. This paper feed is performed using the paper feed roller 12 . The image forming apparatus 1 introduces the fed sheet SH between the intermediate transfer belt 26 and the secondary transfer roller 28 at a predetermined timing. This introduction is performed using registration rollers 13 . The image forming apparatus 1 transfers the toner image formed on the surface of the intermediate transfer belt 26 onto the introduced paper (secondary transfer). This secondary transfer is performed using a secondary transfer roller 28 . During this secondary transfer, a predetermined transfer voltage is applied to the secondary transfer roller 28 .

After the secondary transfer, toner that has not been transferred to the paper remains on the surface of the intermediate transfer belt 26 . The image forming apparatus 1 removes toner remaining on the surface of the intermediate transfer belt 26 . Residual toner is removed using the cleaning device 29 .

The image forming apparatus 1 guides the sheet onto which the toner image has been transferred to the fixing device 30 . The image forming apparatus 1 applies heat and pressure to the toner image using the fixing device 30 to fix the toner image on the paper. After that, the image forming apparatus 1 discharges the sheet on which the toner image is fixed to the discharge tray 15 . This discharge is performed using the discharge roller 14 .

FIG. 2 is a cross-sectional view schematically showing the configuration of fixing device 30 and the configuration of members around fixing device 30 according to an embodiment of the present invention.

Referring to FIG. 2, fixing device 30 includes a fixing belt 31 (an example of a fixing rotating body), a pad 32, a heating roller 33, a halogen heater 34 (an example of a heating member), a supporting member 35, and a sliding member. It includes a moving sheet 36 , a curvature imparting member 37 , a pressure roller 38 (an example of a pressure rotating body), and a supply member 39 .

The fixing belt 31 is an endless belt. The fixing belt 31 heats the toner image to fix the toner image on the paper. The fixing belt 31 is supported by guide members (side plates) (not shown) at both ends in the axial direction of the fixing belt 31 . The fixing belt 31 is in pressure contact with the pressure roller 38 and forms a nip portion NP with the pressure roller 38 . The fixing belt 31 is stretched around the pad 32 , the heating roller 33 and the supply member 39 . The fixing belt 31 has an outer diameter of approximately 10 mm to 100 mm. The fixing belt 31 includes a base layer, an elastic layer, and a release layer. The base layer is made of PI (polyimide), SUS (stainless steel), Ni (nickel), or the like. The base layer has a thickness of the order of 5 μm to 100 μm. The elastic layer is formed on the surface of the base layer. The elastic layer is made of a highly heat-resistant material such as silicone rubber or fluororubber. The elastic layer has a thickness of about 10 μm to 300 μm. . The release layer is formed on the surface of the elastic layer. The release layer is imparted with release properties. The release layer is made of a fluorine tube, a fluorine-based coating, or the like. The release layer has a thickness of about 5 μm to 100 μm.

The pad 32 is arranged inside the fixing belt 31 . The pad 32 extends parallel to the extending direction of the central axis R of the pressure roller 38 . The pad 32 presses the fixing belt 31 from the inner side of the fixing belt 31 . The pad 32 stretches the fixing belt 31 inside the fixing belt 31 . The pad 32 is made of liquid crystal polymer resin or the like.

The heating roller 33 has a cylindrical shape and is provided inside the fixing belt 31 . The heating roller 33 stretches the fixing belt 31 inside the fixing belt 31 . The heating roller 33 transfers the heat of the halogen heater 34 to the fixing belt 31 . The heating roller 33 follows the rotation of the fixing belt 31 . The heating roller 33 has a rotating shaft parallel to the extending direction of the central axis R of the pressure roller 38 . The heating roller 33 is made of Al (aluminum), SUS, or the like. The heating roller 33 has an outer diameter of approximately 10 to 100 mm. The heating roller 33 has a thickness of approximately 0.1 mm to 5 mm. The inner peripheral surface of the heating roller 33 is painted black. The purpose of this coating is to increase the absorption of light emitted from the halogen heater 34 . A coating layer made of PTFE (polytetrafluoroethylene) or the like is provided on the outer peripheral surface of the heating roller 33 . The purpose of this coating layer is to prevent damage from foreign objects.

A halogen heater 34 is provided inside the heating roller 33 . The halogen heater 34 extends parallel to the extending direction of the central axis R of the pressure roller 38 . Halogen heater 34 heats fixing belt 31 to a predetermined target temperature via heating roller 33 .

Note that the fixing belt 31 and the heating roller 33 may be heated by the IH method instead of being heated by the halogen heater. Fixing belt 31 and heating roller 33 may be heated by applying an electric current to fixing belt 31 or heating roller 33 made of a resistance heating element.

The support member 35 is provided inside the fixing belt 31 . The support member 35 extends parallel to the extending direction of the central axis R of the pressure roller 38 . A support member 35 supports the pad 32 and the curvature imparting member 37 . The support member 35 is made of, for example, a U-shaped sheet metal. The support member 35 has a thickness of approximately 2 mm.

The sliding sheet 36 is sandwiched between the inner peripheral surface of the fixing belt 31 and the outer peripheral surface of the pad 32 . The sliding sheet 36 is wound around the outer peripheral surface of the pad 32 by one turn or more. The sliding sheet 36 reduces frictional resistance between the fixing belt 31 and the pad 32 . As a result, the fixing belt 31 can rotate stably. The sliding sheet 36 includes a base material made of glass cloth. The sliding surface of the sliding sheet 36 is coated with a fluororesin. The sliding sheet 36 may be made of fluorofiber fabric, fluororesin sheet, glass coat, or the like.

The curvature imparting member 37 is fixed to the upper portion of the support member 35 . The curvature imparting member 37 is provided inside the fixing belt 31 . The curvature imparting member 37 stretches the fixing belt 31 through the supply member 39 . Each of the pad 32 and the curvature imparting member 37 is made of resin such as polyphenylene sulfide, polyimide, or liquid crystal polymer, metal such as aluminum or iron, ceramic, or the like. Each of the pad 32 and the curvature imparting member 37 may include a fixing member made of silicone rubber, fluororubber, or the like. Each of the pad 32 and the curvature imparting member 37 has an arbitrary shape.

The pressure roller 38 is provided outside the fixing belt 31 . The pressure roller 38 faces the pad 32 with the fixing belt 31 interposed therebetween. The pressure roller 38 presses the portion of the fixing belt 31 pressed against the pad 32 . Thereby, the pressure roller 38 and the fixing belt 31 form a nip portion NP. The pressure roller 38 rotates about the central axis R in the direction indicated by the arrow AR11. The pressure roller 38 is rotationally driven at a predetermined rotational speed by a fixing conveying motor (not shown). The fixing belt 31 follows the rotation of the pressure roller 38 . The fixing belt 31 rotates in a direction indicated by an arrow AR12. The pressure roller 38 has an outer diameter of 20-100 mm. The pressure roller 38 includes a metal core, an elastic layer, and a release layer. The core bar is made of metal such as aluminum or iron. The core bar has a thickness of about 0.1 to 10 mm. The cored bar has a pipe shape. The core bar may have a solid shape or a three-arrow cross-sectional shape. The elastic layer is formed on the surface of the cored bar. The elastic layer is made of a highly heat-resistant material such as silicone rubber or fluororubber. The elastic layer has a thickness of about 1 mm to 20 mm. The release layer is formed on the surface of the elastic layer. The release layer is imparted with release properties. The release layer is made of a fluorine tube, a fluorine-based coating, or the like. The release layer has a thickness of 5 μm to 100 μm.

The supply member 39 is fixed to the upper portion of the curvature imparting member 37 . The supply member 39 is in contact with the inner circumferential surface of the fixing belt 31 at a position different from the sliding portion in the circumferential direction of the fixing belt 31 . This sliding portion is a sliding portion between the fixing belt 31 and the sliding sheet 36 . The supply member 39 extends parallel to the central axis R of the pressure roller 38 . Supply member 39 contains a lubricant. The supply member 39 applies lubricant to the inner peripheral surface of the fixing belt 31 . The applied lubricant is supplied to the sliding portion between the fixing belt 31 and the sliding sheet 36 through the inner peripheral surface of the fixing belt 31 . As a result, the lubricant is supplied (replenished) to the sliding portion between the fixing belt 31 and the sliding sheet 36 . The supply member 39 is made of a material such as felt that can be impregnated with a lubricant.

The paper onto which the toner image has been transferred passes through the nip portion NP. When passing through the nip portion NP, the surface of the paper onto which the toner image has been transferred faces the heated fixing belt 31 . The toner image on the paper is heated by the fixing belt 31 when passing through the nip portion NP. As a result, the toner image is fixed on the paper.

FIG. 3 is a layout diagram showing the positional relationship between members constituting fixing device 30 and members near fixing device 30 according to an embodiment of the present invention. In the drawings, the arrow CD indicates the CD direction. In this embodiment, the CD direction is parallel to the extending direction of each of the y-axis and central axis R.

2 and 3, image forming apparatus 1 includes duct 40 (an example of a duct), fan 51 (an example of a fan), guides 52 and 53, shutter 54 (an example of a shutter), sensor It further comprises 55 and 56 (an example of a sensor) and a windbreak member 57 (an example of a windbreak member).

A duct 40 is provided along the outer circumference of the pressure roller 38 . A space between the duct 40 and the surface of the pressure roller 38 serves as a flow path for air flow by the fan 51 . This flow path is indicated by arrow AR1. Duct 40 includes two ducts 40A and 40B. Each of the two ducts 40A and 40B is arranged along the CD direction. The center position of the pressure roller 38 in the CD direction is referred to as center position CP. A plane that includes the center position CP and is perpendicular to the center axis R is referred to as a center plane. The two ducts 40A and 40B are provided at symmetrical positions with respect to this center plane. Each of the two ducts 40A and 40B has a shape that is symmetrical with respect to this center plane. The number and position of ducts 40 are arbitrary.

In each of the ducts 40A and 40B, the speed of the wind flowing between the surface of the pressure roller 38 and the duct varies along the CD direction.

The fan 51 creates wind. Fan 51 sends air to duct 40 . Fan 51 includes two fans 51A and 51B. The fan 51A sends air to the duct 40A. The fan 51B sends air to the duct 40B.

Guides 52 and 53 guide the wind from fan 51 to duct 40 . The guide 53 is provided downstream of the guide 52 in the wind direction (arrow AR1). Guide 52 includes two guides 52A and 52B. Guide 53 includes two guides 53A and 53B. Guides 52A and 53A guide the wind generated by fan 51A to duct 40A. Guides 52B and 53B guide the wind generated by fan 51B to duct 40B.

A plurality of partitions 403 are provided in each of the ducts 40A and 40B. Guide 52A includes each of a plurality of partitions 521 . Each of the multiple partitions 521 of the guide 52A corresponds to each of the multiple partitions 403 of the duct 40A. Guide 53A includes a plurality of partitions 531 each. Each of the multiple partitions 531 of the guide 53A corresponds to each of the multiple partitions 403 of the duct 40A. Guide 52B includes each of a plurality of partitions 521 . Each of the multiple partitions 521 of the guide 52B corresponds to each of the multiple partitions 403 of the duct 40B. Guide 53B includes a plurality of partitions 531 each. Each of the multiple partitions 531 of the guide 53B corresponds to each of the multiple partitions 403 of the duct 40B.

The shutter 54 is an area to which air is blown by the fan 51 and adjusts the area of the surface of the pressure roller 38 . This adjustment is performed according to the width of the sheet passing through the nip portion NP in the CD direction. Shutter 54 includes shielding plates 541 and 542 and pinion 543 . Each of shield plates 541 and 542 includes a rack. Pinion 543 is rotationally driven by a motor or the like.

It is assumed that each of shield plates 541 and 542 opens air inlet 522 in each of guides 52A and 52B. This state corresponds to a state in which the shutter 54 is open. In this state, when the pinion 543 rotates in the direction indicated by the arrow AR21, the shield plate 541 moves in the direction indicated by the arrow AR23. The shield plate 542 moves in the direction indicated by arrow AR24. As the amount of rotation of the pinion 543 increases, the introduction ports 522 of the guides 52A and 52B are sequentially blocked from the side closer to the center position CP. As the amount of rotation of pinion 543 increases, wind stops flowing through each of ducts 40A and 40B in order from the side closer to center position CP. As the amount of rotation of the pinion 543 increases, the area of the surface of the pressure roller 38 that is not hit by the wind gradually increases from the side closer to the center position CP.

On the other hand, it is assumed that each of the shielding plates 541 and 542 shields the air introduction port 522 of each of the guides 52A and 52B. This state corresponds to a state in which the shutter 54 is closed. When the pinion 543 rotates in the direction indicated by the arrow AR22 in this state, the shield plate 541 moves in the direction indicated by the arrow AR24. The shield plate 542 moves in the direction indicated by arrow AR23. As the amount of rotation of the pinion 543 increases, the introduction ports 522 of the guides 52A and 52B are released in order from the side farthest from the center position CP. As the amount of rotation of pinion 543 increases, air flows through each of ducts 40A and 40B in order from the side farthest from center position CP. As the amount of rotation of the pinion 543 increases, the area of the surface of the pressure roller 38 hit by the wind gradually increases from the side farther from the center position CP.

The sensor 55 consists of a thermostat. A sensor 55 detects the temperature of the fixing belt 31 . The sensor 55 cuts off the power supply to the halogen heater 34 when the detected temperature exceeds a predetermined temperature. A sensor 55 stops heating by the halogen heater 34 .

The sensor 56 consists of a thermistor. A sensor 55 detects the temperature of the fixing belt 31 . The controller 70 controls heating by the halogen heater 34 . Heating by the halogen heater 34 is controlled so that the temperature detected by the sensor 55 during fixing becomes a predetermined target temperature.

The windbreak member 57 is provided upstream of the sensors 55 and 56 in the rotation direction of the fixing belt 31 (the direction indicated by the arrow AR12). The windbreak member 57 is made of Mylar, a guide, or the like.

Referring to FIG. 3, fixing belt 31 can fix a toner image on each of a plurality of types of paper SH having a plurality of widths in the CD direction. Specifically, the fixing belt 31 can fix the toner images on each of the A3 size paper sheet SH1 in portrait orientation, the A4 size paper sheet SH2 in landscape orientation, and the A6 size paper SH3 in portrait orientation. is. The sheet SH1 has a width WD1 (300 mm) in the CD direction. The sheet SH2 has a width WD2 (220 mm) in the CD direction. The sheet SH3 has a width WD3 (160 mm) in the CD direction.

The halogen heater 34 heats the entire CD-direction region RG1 of the fixing belt 31 . The width of the region RG1 in the CD direction is larger than the maximum width in the CD direction of the sheet passing through the nip portion NP (that is, the width WD1).

Further, the halogen heater 34 may change the area of the fixing belt 31 to be heated according to the width in the CD direction of the sheet passing through the nip portion NP. Specifically, the halogen heater 34 may include two halogen heaters 341 and 342 having different widths. If the sheet passing through nip portion NP is sheet SH1 or SH2, the entire region RG1 may be heated by halogen heater 341 . The width of region RG1 in the CD direction is larger than widths WD1 and WD2. If the sheet passing through the nip portion NP is the sheet SH3, the entire region RG2 may be heated by the halogen heater 342. FIG. The width of region RG2 in the CD direction is larger than width WD3 and smaller than widths WD1 and WD2.

FIG. 4 is a perspective view schematically showing the configuration of the duct 40A. FIG. 4(a) shows the configuration of the duct 40A on the pressure roller 38 side. FIG. 4(b) shows the configuration of the duct 40A on the side opposite to the pressure roller 38. As shown in FIG. Since the duct 40B is mirror-symmetrical to the duct 40A, the description thereof will not be repeated.

Referring to FIG. 4, the space between the duct 40A and the surface of the pressure roller 38 serves as a flow path for air flow by the fan 51A. Air from fan 51A is introduced into duct 40A through inlet 405 after passing through guides 52A and 53A. The introduction port 405 is configured between the surface of the pressure roller 38 and the end portion 402c. The end portion 402 c is the downstream end portion of the body portion 402 along the rotation direction of the pressure roller 38 . As indicated by arrow AR1, the wind introduced into duct 40A collides with the surface of pressure roller 38 and flows between the surface of pressure roller 38 and surface 4021 of main body 402. As shown in FIG. This wind is discharged in a direction away from the surface of the pressure roller 38 through the discharge port 401 . The outlet 401 is provided upstream of the inlet 405 in the direction of rotation of the pressure roller 38 .

The duct 40A includes a discharge port 401 (an example of a discharge port), a main body portion 402 (an example of a main body portion), a plurality of partitions 403 (an example of a partition), a projecting portion 404 (an example of a projecting portion), and two and a mounting portion 406 . The body portion 402 extends in the CD direction. The body portion 402 is provided along the surface of the pressure roller 38 . The body portion 402 includes a surface 4021 that is the surface on the pressure roller 38 side. The pressure roller 38 has a cylindrical shape. Therefore, when cut along a plane perpendicular to the central axis R, the surface 4021 of the main body 402 has an arcuate cross-sectional shape. A surface 4021 of the main body portion 402 faces the flow path of the air generated by the fan 51A.

Each of the plurality (here, five) of partitions 403 divides the discharge port 401 into each of a plurality (here, four) of openings 401a, 401b, 401c, and 401d. Each of the plurality of openings 401a, 401b, 401c, and 401d are arranged in the CD direction. Of the plurality of openings 401a, 401b, 401c, and 401d, the opening 401a is provided at the furthest position from the central position CP of the pressure roller . Of the plurality of openings 401a, 401b, 401c, and 401d, the opening 401d is provided closest to the center position CP of the pressure roller . Also, each of the plurality of partitions 403 extends to the surface 4021 of the body portion 402 . Each of the multiple partitions 403 is provided along the rotation direction of the pressure roller 38 . Each of the plurality of partitions 403 divides the flow path of the wind by the fan 51A into a plurality of flow portions 4021a, 4021b, 4021c, and 4021d. Each of the plurality of circulation portions 4021a, 4021b, 4021c, and 4021d are arranged in the CD direction. Each of the multiple circulation portions 4021a, 4021b, 4021c, and 4021d corresponds to each of the multiple openings 401a, 401b, 401c, and 401d. That is, the wind that has passed through the circulation portion 4021a is discharged from the opening portion 401a, the wind that has passed through the circulation portion 4021b is discharged from the opening portion 401b, the wind that has passed through the circulation portion 4021c is discharged from the opening portion 401c, and the wind that has passed through the circulation portion 4021d is discharged from the opening portion 401c. The air that has flowed through is discharged from the opening 401d.

The projecting portion 404 is provided on the upstream end portion 402 d side of the body portion 402 along the rotation direction of the pressure roller 38 . The protruding portion 404 protrudes from the body portion 402 toward the surface of the pressure roller 38 . The projecting portion 404 and the end portion 402 d of the main body portion 402 constitute the discharge port 401 . Protruding portion 404 prevents the air flowing between the surface of pressure roller 38 and each of fans 51A and 51B from advancing toward the outer circumference of fixing belt 31 . Protruding portion 404 guides a larger portion of the wind introduced from inlet 405 of each of fans 51A and 51B to outlet 401 .

Each of the two attachment portions 406 is attached to both ends of the body portion 402 in the CD direction. The duct 40A is attached to the image forming apparatus main body 1a through the attachment portion 406 using screws (not shown) or the like.

FIG. 5 is a diagram showing the shape of a portion of duct 40A in one embodiment of the present invention. FIG. 5 shows the shape of the duct 40A on the surface 4021 side.

Referring to FIG. 5, the shape of each outlet 401 of ducts 40A and 40B varies along the CD direction. As a result, the speed of the wind flowing between the surface of pressure roller 38 and each of ducts 40A and 40B changes along the CD direction.

That is, each of the plurality of openings 401a, 401b, 401c, and 401d forming the discharge port 401 has a height (length along the rotation direction of the pressure roller 38) Ha, Hb, Hc, and Hd, respectively. have. Each of heights Ha, Hb, Hc, and Hd corresponds to the length along the rotation direction of pressure roller 38 . Some of the heights Ha, Hb, Hc, and Hd are different from other heights. Here, height Ha is greater than each of heights Hb, Hc, and Hd. Each of the heights Hb, Hc and Hd are equal to each other. The width of each of the openings 401a, 401b, 401c, and 401d in the CD direction is arbitrary.

The smaller the opening height, the less air escapes out of the duct through the opening. As a result, the smaller the height of the opening, the greater the pressure and velocity of the wind passing through that opening. In the present embodiment, the pressure and velocity of wind passing through each of opening 401b and flow-through portion 4021b, opening 401c and flow-through portion 4021c, and opening 401d and flow-through portion 4021d are controlled by opening 401a and flow-through portion 4021a. Greater than the pressure and velocity of the passing wind.

The distribution of heights Ha, Hb, Hc, and Hd can adjust the cooling capacity of the fan 51 along the CD direction of the surface of the pressure roller 38 .

If the pressure of the wind flowing through each of the openings 401b, 401c, and 401d is higher than the pressure of the wind passing through the opening 401a, the wind from the fan 51A may be biased toward the opening 401a. Therefore, the partition 403 can prevent such deviation of the wind. As a result, the pressure of the wind flowing through each of the openings 401b, 401c, and 401d can be increased.

Also, height Ha is greater than each of heights Hb, Hc, and Hd. Therefore, the length along the surface of the pressure roller 38 of each of the circulation portions 4021b, 4021c, and 4021d is longer than the length along the surface of the pressure roller 38 of the circulation portion 4021a. As a result, the cooling capacity of duct 40 at positions corresponding to openings 401b, 401c, and 401d in the CD direction is higher than the cooling capacity of duct 40 at positions corresponding to opening 401a in the CD direction.

3 to 5, pressure roller 38 and fixing belt 31 are both rotating bodies. Therefore, when the air from the fan 51 hits the pressure roller 38 , the air from the fan 51 cannot be completely sealed in the duct 40 . Part of the air introduced from inlet 405 passes through between the surface of pressure roller 38 and protrusion 404 as indicated by arrow AR2. Part of the air introduced from the introduction port 405 wraps around the outer periphery of the fixing belt 31 along the surface of the pressure roller 38 .

When the wind that reaches the outer periphery of the fixing belt 31 hits the sensors 55 and 56, the sensors 55 and 56 are cooled. As a result, the temperatures detected by the sensors 55 and 56 are low even though the fixing belt 31 is at an abnormally high temperature. This delays the detection of abnormally high temperatures (activation of protection).

The two outer sensors 55B and 56B are provided at positions corresponding to the position of the opening 401a in the CD direction in order to reduce the influence of the wind that has flowed to the outer periphery of the fixing belt 31. FIG. The two outer sensors 55B and 56B are provided at positions corresponding to the non-sheet-passing portions on the surface of the pressure roller 38 in the CD direction. Among the plurality of openings 401a, 401b, 401c, and 401d, opening 401a has the slowest wind speed. Therefore, the temperature of the hottest portion of the fixing belt 31 can be detected by the two outer sensors 55B and 56B. It is possible to avoid a situation in which the detection of abnormally high temperatures is delayed.

In addition, the wind from the fan 51 is weaker at positions where the ducts 40A and 40B do not exist in the CD direction than at positions where the ducts 40A and 40B exist in the CD direction. Therefore, the two inner sensors 55A and 56A are provided at different positions in the CD direction than the ducts 40A and 40B.

Furthermore, by providing the windbreak member 57, the influence of the wind that reaches the outer periphery of the fixing belt 31 is reduced.

FIG. 6 is a diagram showing the relationship between the width in the CD direction of the paper passing through the nip portion NP and the method of cooling the surface of the pressure roller 38. As shown in FIG.

5 and 6, the center position CP of pressure roller 38 is set as a reference (0 mm). The opening 401a and the flow portion 4021a of the duct 40A are provided in the range of -180 mm to -145 mm. The opening 401b and the flow portion 4021b of the duct 40A are provided in the range of -145 mm to -110 mm. The opening 401c and the flow portion 4021c of the duct 40A are provided within the range of -110 mm to -80 mm. The opening 401d and the flow portion 4021d of the duct 40A are provided in the range of -80 mm to -50 mm. Similarly, the opening 401a and the flow portion 4021a of the duct 40B are provided within the range of 180 mm to 145 mm. The opening 401b and the flow portion 4021b of the duct 40B are provided within a range of 145 mm to 110 mm. The opening 401c and the flow portion 4021c of the duct 40B are provided within a range of 110 mm to 80 mm. The opening 401d and the flow portion 4021d of the duct 40B are provided within the range of 80 mm to 50 mm.

The control unit 70 opens and closes the shutter 54 according to the width in the CD direction of the sheet passing through the nip portion NP. As a result, the area exposed to air through the duct 40 is adjusted. Further, the control unit 70 turns the fan 51 on and off according to the width of the sheet passing through the nip portion NP in the CD direction. Thereby, the speed of the wind by the fan 51 is adjusted. Also, the cooling ability of the fan 51 along the CD direction of the surface of the pressure roller 38 is controlled.

Specifically, it is assumed that the sheet passing through the nip portion NP is the sheet SH1. The sheet SH1 has a width WD1 (300 mm) in the CD direction. In this case, as shown in FIG. 6A, portions in the range of −150 mm to −160 mm and 150 mm to 160 mm on the surface of the pressure roller 38 are non-paper-passing portions (portions through which paper does not pass). Temperatures in these ranges are locally high. However, since the area of the non-sheet-passing portion is smaller than the area of the sheet-passing portion, the temperature rise is small when the sheet SH1 passes through.

When the sheet SH1 passes through, the openings 401b, 401c, and 401d and the flow portions 4021b, 4021c, and 4021d in the introduction ports 522 of the guides 52A and 52B are blocked by the shutter 54. In addition, the air volume of the fan 51 is reduced. As a result, air does not flow through the openings 401b, 401c, and 401d and the flow portions 4021b, 4021c, and 4021d. Only portions in the range of −180 mm to −145 mm and 145 mm to 180 mm on the surface of the pressure roller 38 are cooled with a small amount of air. Portions within these ranges correspond to portions of the surface of pressure roller 38 corresponding to opening 401a and circulation portion 4021a.

Assume that the sheet passing through the nip portion NP is the sheet SH2. The sheet SH2 has a width WD2 (220 mm) in the CD direction. In this case, as shown in FIG. 6(b), portions in the range of −110 mm to −160 mm and 110 mm to 160 mm on the surface of the pressure roller 38 are non-passing portions. Temperatures in these ranges are locally high. However, since the area of the non-sheet-passing portion is larger than the area of the sheet-passing portion, the temperature rise is large when the sheet SH2 passes through.

When the sheet SH2 passes through, the openings 401c and 401d in the introduction ports 522 of the guides 52A and 52B and the portions corresponding to the circulation portions 4021c and 4021d are blocked by the shutter . Also, the air volume by the fan 51 is increased. As a result, air does not flow through the openings 401c and 401d and the flow portions 4021c and 4021d. Only the -180 mm to -110 mm range and 110 mm to 180 mm range portions of the surface of the pressure roller 38 are cooled with a large amount of air. These ranges correspond to the surface portions of the pressure roller 38 corresponding to the opening 401a and the flow portion 4021a, and the opening 401b and the flow portion 4021b.

Assume that the sheet passing through the nip portion NP is the sheet SH3. The sheet SH3 has a width WD3 (120 mm) in the CD direction. In this case, as shown in FIG. 6(c), portions in the range of -60 mm to -140 mm and in the range of 60 mm to 140 mm on the surface of the pressure roller 38 are non-sheet-passing portions. The temperature in this range is locally high. However, since the area of the non-sheet-passing portion is much larger than the area of the sheet-passing portion, the temperature rise is very large when the sheet SH3 passes through.

When the sheet SH3 passes through, the shutter 54 is fully opened. Also, the air volume by the fan 51 is increased. As a result, a portion in the range of -180 mm to 180 mm on the surface of the pressure roller 38 is cooled with a large amount of air. Portions within these ranges are portions of the surface of pressure roller 38 corresponding to opening 401a and flow-through portion 4021a, opening 401b and flow-through portion 4021b, opening 401c and flow-through portion 4021c, and opening 401d and flow-through portion 4021d. corresponds to

Here, when the paper passing through the nip portion NP is the paper SH3, the temperature of the portions in the range of -140 mm to -160 mm and in the range of 140 mm to 160 mm of the non-paper passing portion on the surface of the pressure roller 38 is away from the edge. Therefore, the temperature in these ranges is not very high. In the present embodiment, the velocity of wind passing through opening 401a and flow-through portion 4021a is less than the wind speed. Therefore, it is possible to efficiently cool the high-temperature portion of the non-sheet-passing portion without excessively cooling the low-temperature portion. As a result, the occurrence of low temperature offset can be suppressed.

The partition 403 may be provided at a position where the surface of the pressure roller 38 has the highest temperature in the CD direction when the fixing device 30 fixes each of the sheets SH1, SH2, and SH3.

In the present embodiment, the speed of air flowing between the surface of pressure roller 38 and duct 40 changes along the CD direction. For this reason, it is possible to guide the wind at a speed corresponding to the temperature distribution along the CD direction of the pressure roller 38 during fixing to the surface of the pressure roller 38 . In addition, it is possible to prevent the wind that cools the surface of the pressure roller 38 from reaching the fixing belt 31 . Thereby, the pressure roller 38 can be cooled appropriately.

Also, the outlet 401 of each of the ducts 40A and 40B is provided upstream of the inlet 405 in the rotational direction of the pressure roller 38 . Therefore, it is possible to send air in a direction opposite to the rotation direction of the pressure roller 38 . The ability of the fan 51 to cool the surface of the pressure roller 38 can be improved.

[Modification]

FIG. 7 is a diagram illustrating a first modification of one embodiment of the present invention. FIG. 7A is a cross-sectional view showing an enlarged configuration of part of the fixing device 30 in the first modified example of the embodiment of the invention. FIG. 7(b) is a diagram showing distribution of the minimum distance d in the CD direction in the first modification of the embodiment of the present invention.

Referring to FIG. 7, the minimum distance between each of a plurality of circulation portions 4021a, 4021b, 4021c, and 40221d and the surface of pressure roller 38 is defined as minimum distance d. The minimum distance d corresponds to the minimum distance of a section from one end (end 402c of body portion 402) to the other end (end 402d of body portion 402) of the circulation portion along the rotation direction of pressure roller 38. FIG.

In each of the ducts 40A and 40B of the first modified example, the minimum distance d of some of the plurality of circulation portions 4021a, 4021b, 4021c, and 4021d is the plurality of circulation portions 4021a, 4021b, 4021c, and 40221d is different from the minimum distance d of the flow portion of other portions. Here, the minimum distance d between the flow portion 4021 a and the surface of the pressure roller 38 is greater than the minimum distance d between each of the flow portions 4021 b, 4021 c, and 4021 d and the surface of the pressure roller 38 . The minimum distances d between each of the flow portions 4021b, 4021c, and 4021d and the surface of the pressure roller 38 are equal to each other.

The smaller the minimum distance d, the smaller the amount of air circulating through the circulating portion. As a result, the smaller the minimum distance d, the greater the pressure and velocity of the wind circulating through that section. In the present embodiment, the pressure and velocity of wind passing through each of opening 401b and flow-through portion 4021b, opening 401c and flow-through portion 4021c, and opening 401d and flow-through portion 4021d are controlled by opening 401a and flow-through portion 4021a. Greater than the pressure and velocity of the passing wind.

Thus, the cooling capacity of the fan 51 along the CD direction of the surface of the pressure roller 38 can be adjusted by the distribution of the minimum distance d of each of the circulation portions 4021a, 4021b, 4021c, and 4021d.

If the pressure of the air flowing through each of circulation portions 4021b, 4021c, and 4021d is higher than the pressure of the wind passing through circulation portion 4021a, the wind from fan 51A may be biased toward circulation portion 4021a. Therefore, by providing the partition 403, such deviation of the wind can be prevented. As a result, it is possible to circulate high-pressure wind through each of the circulating portions 4021b, 4021c, and 4021d.

FIG. 8 is a diagram illustrating a second modification of one embodiment of the present invention. FIG. 8(a) is a cross-sectional view showing an enlarged configuration of part of a duct 40A in a second modification of one embodiment of the present invention. FIG. 8(b) is a diagram showing the CD-direction distribution of the average area TAV of each of the flow portions 4021a, 4021b, 4021c, and 4021d in the second modification of the embodiment of the present invention.

Referring to FIG. 8, in each of ducts 40A and 40B of the second modification, lattice-like (mesh-like) wire rods 407 (wire rod example) is provided. Focusing on one opening, the opening is divided into a plurality of sections 407a by the wire 407. FIG. An area T is defined as the area of one partition 407a. An average area (in other words, an average value of areas T) of each of the plurality of sections 407a forming one opening is defined as an average area TAV. The average area TAV of some of the plurality of openings 401a, 401b, 401c, and 401d differs from the average area TAV of other openings of the plurality of openings 401a, 401b, 401c, and 401d. ing. Here, the average area TAV of opening 401a is greater than the average area TAV of each of openings 401b, 401c, and 401d. The average areas TAV of each of openings 401b, 401c, and 401d are equal to each other.

The wire 407 serves as a barrier against wind passing through the opening. Therefore, the smaller the average area TAV, the smaller the amount of air flowing through the opening. As a result, the pressure and velocity of the wind passing through that opening is high. In the present embodiment, the pressure and velocity of the wind passing through each of the opening 401b and the circulation portion 4021b, the opening 401c and the circulation portion 4021c, and the opening 401d and the circulation portion 4021d are the same as those of the opening with the largest average area TAV. Greater than the pressure and velocity of the wind passing through 401a and through portion 4021a.

Thus, the cooling capacity of the fan 51 along the CD direction of the surface of the pressure roller 38 can be adjusted by the distribution of the average area TAV of each of the openings 401a, 401b, 401c, and 401d.

Further, when the pressure of the wind flowing through each of the openings 401b, 401c, and 401d is higher than the pressure of the wind passing through the opening 401a, there is a possibility that the wind from the fan 51A may flow unevenly through the opening 401a. be. Therefore, by providing the partition 403, it is possible to prevent such unevenness of air flow, and to allow high-pressure air to flow through each of the flow portions 4021b, 4021c, and 4021d.

[Example]

FIG. 9 is a diagram showing changes in height H in the CD direction of each of Comparative Example A, Comparative Example B, and Invention Example C in one example of the present invention. FIG. 10 is a table showing measurement results of various numerical values of Comparative Example A, Comparative Example B, and Invention Example C in one example of the present invention. Note that among the columns in which the measured values are described in the table of FIG. 10, the columns of the measured values that are worse than the reference values are hatched.

Referring to FIG. 9, fixing device 30 is provided with duct 40A and duct 40B as ducts for cooling the surface of pressure roller 38 . Ducts 40A and 40B were mirror images of each other. In each of the ducts 40A and 40B, a partition 403 divides the outlet 401 into five openings 401a, 401b, 401c, 401d, and 401e arranged in the CD direction.

In Comparative Example A, the height (the length along the rotation direction of the pressure roller 38) H of each of the plurality of openings 401a, 401b, 401c, 401d, and 401e was set to the same height H1.

In Comparative Example B, the height H of each of the plurality of openings 401a, 401b, 401c, 401d, and 401e was set to the same height H2 (<H1).

In Example C of the present invention, the height H of the opening 401a located farthest from the central position CP among the plurality of openings 401a, 401b, 401c, 401d, and 401e was set to the height H3. The height H of each of the openings 401b, 401c, 401d, and 401e is set to the same height H4 (<H3).

9 and 10, a toner image was fixed on a sheet using fixing device 30 having each of Comparative Example A, Comparative Example B, and Inventive Example C mounted therein. The speed (m/s) of the wind that flowed around the fixed position of the fixing belt 31 during fixing and the maximum temperature (° C.) during fixing of the non-paper passing portion on the surface of the pressure roller 38 were measured. The wind speed was measured at positions corresponding to each of the plurality of openings 401a, 401b, 401c, 401d, 401e in the CD direction. The maximum temperature of the non-sheet-passing portion during fixing was measured on each of the front side (duct 40A side) and the back side (duct 40B side) in the central axis R direction of the pressure roller 38 . The reference value of the speed of the wind that has flowed around the predetermined position of the fixing belt 31 during fixing was set to 0.3 m/s. The reference value for the maximum temperature of the non-paper passing portion during fixing was set to 230°C.

In Comparative Example A, the maximum temperature during fixing of the non-sheet-passing portion was higher than the reference value on both the front side and the back side. Therefore, in Comparative Example A, the surface of the pressure roller 38 was not sufficiently cooled.

In Comparative Example B, the speed of the wind that flowed into the position corresponding to the opening 401a during fixing was greater than the reference value. Therefore, in Comparative Example B, unnecessary portions of the fixing device were cooled.

In Example C of the present invention, the speed of the wind that flowed around during fixing was lower than the reference value at all positions. Therefore, in Example C of the present invention, there was no problem of cooling unnecessary portions of the fixing device. In addition, in Example C of the present invention, the maximum temperature during fixing of the non-sheet-passing portion was lower than the reference value on both the front side and the back side. Therefore, in Example C of the present invention, the surface of the pressure roller 38 was sufficiently cooled.

[others]

The embodiments and modifications described above can be combined as appropriate. For example, the above embodiment, the first modification, and the second modification may be combined. In this case, each of ducts 40A and 40B has all three configurations.

(1) Some of the heights Ha, Hb, Hc, and Hd of the plurality of openings 401a, 401b, 401c, and 401d are different from the other heights.

(2) The minimum distance d of some of the plurality of circulation portions 4021a, 4021b, 4021c, and 40221d is the minimum distance d of the other portions of the plurality of circulation portions 4021a, 4021b, 4021c, and 40221d. different from the distance d.

(3) Each of the plurality of openings 401a, 401b, 401c, and 401d is divided into a plurality of sections 407a by grid-like wire rods 407; The average area TAV of each of the plurality of partitions 407a in each of the plurality of openings 401a, 401b, 401c, and 401d is different from each other.

The above-described embodiments and modifications should be considered illustrative in all respects and not restrictive. The scope of the present invention is indicated by the scope of the claims rather than the above description, and is intended to include all modifications within the scope and meaning of equivalents of the scope of the claims.

1 Image Forming Apparatus 1a Image Forming Apparatus Main Body 10 Paper Conveying Section 11 Paper Feed Tray 12 Paper Feed Roller 13 Registration Roller 14 Paper Discharge Roller 15 Paper Discharge Tray 20 Toner Image Forming Section 20A Image Forming Unit 21 Photosensitive Drum 22 Charging Device 23 Exposure Apparatus 24 Developing device 25 Cleaning device 26 Intermediate transfer belt 26a Rotating roller 27 Primary transfer roller 28 Secondary transfer roller 29 Cleaning device 30 Fixing device 31 Fixing belt (an example of fixing rotating body)
32 pad 33 heating roller 34, 341, 342 halogen heater (an example of a heating member)
35 Supporting member 36 Sliding sheet 37 Curvature imparting member 38 Pressure roller (an example of a pressure rotating body)
39 supply member 40, 40A, 40B duct (an example of a duct)
51, 51A, 51B Fan (an example of a fan)
52, 52A, 52B, 53, 53A, 53B Guide 54 Shutter (an example of a shutter)
55, 55A, 55B, 56, 56A, 56B sensor (example of sensor)
57 windbreak member (an example of windbreak member)
70 control unit 401 discharge port (an example of discharge port)
401a, 401b, 401c, 401d opening 402 main body (an example of main body)
402c, 402d end of main body 403, 521, 531 partition (an example of partition)
404 protruding part (an example of a protruding part)
405 Inlet 406 Mounting portion 407 Wire (an example of wire)
407a Section 522 Guide introduction port 541, 542 Shutter shielding plate 543 Shutter pinion 4021 Main body surface 4021a, 4021b, 4021c, 4021d Distribution part CD Arrow indicating the direction (CD direction) that traverses the recording medium CP Center position d The minimum distance between the circulation part and the surface of the pressure roller, from one end to the other end of the circulation part along the rotation direction of the pressure roller NP Nip portion R Central axis RG1, RG2 Areas heated by halogen heaters SH, SH1, SH2, SH3 Paper T Area of one of multiple sections divided by wire TAV One opening TR transport path WD1, WD2, WD3 width of paper in CD direction

Claims (17)

a fixing rotary member that heats and fixes the toner image onto the recording medium;
a heating member that heats the fixing rotating body;
a pressing rotator that presses the fixing rotator to form, together with the fixing rotator, a nip portion through which the recording medium passes;
a fan that creates wind,
a duct that constitutes a flow passage for air flow from the fan between the surface of the pressurizing rotating body,
The speed of the air flowing between the surface of the pressure rotating body and the duct is a direction perpendicular to the conveying direction of the recording medium and a direction transverse to the conveyed recording medium. varies along the direction of
The duct is
a main body provided along the surface of the pressurizing rotor and forming a flow path for the air generated by the fan between the pressurizing rotor and the surface of the pressurizing rotor;
a discharge port for discharging the air flowing between the surface of the pressure rotating body and the main body in a direction away from the surface of the pressure rotating body;
An image forming apparatus comprising a plurality of openings arranged in the CD direction and partitions for partitioning the outlet . a fixing rotary member that heats and fixes the toner image onto the recording medium;
a heating member that heats the fixing rotating body;
a pressing rotator that presses the fixing rotator to form, together with the fixing rotator, a nip portion through which the recording medium passes;
a fan that creates wind,
a duct that constitutes a flow passage for air flow from the fan between the surface of the pressurizing rotating body,
The speed of the air flowing between the surface of the pressure rotating body and the duct is a direction perpendicular to the conveying direction of the recording medium and a direction transverse to the conveyed recording medium. varies along the direction of
The duct is
a main body provided along the surface of the pressurizing rotor and forming a flow path for the air generated by the fan between the pressurizing rotor and the surface of the pressurizing rotor;
a discharge port for discharging the air flowing between the surface of the pressure rotating body and the main body in a direction away from the surface of the pressure rotating body;
a partition that divides the discharge port into the plurality of openings arranged in the CD direction,
The partition extends along the direction of rotation of the fixing rotator to the surface of the main body on the pressure rotator side, and circulates between the surface of the pressure rotator and the main body. dividing the air flow passage into a plurality of flow sections, each of which corresponds to each of the plurality of openings;
A minimum distance between some of the plurality of circulation portions and the surface of the pressurizing rotor, which is the section from one end to the other end of the circulation portion along the rotational direction of the pressurization rotor. The image forming apparatus, wherein the minimum distance is different from the minimum distance of other circulation portions among the plurality of circulation portions. 3. The image forming apparatus according to claim 2 , wherein the smaller the minimum distance, the higher the speed of the air flowing through each of the plurality of flow portions. a fixing rotary member that heats and fixes the toner image onto the recording medium;
a heating member that heats the fixing rotating body;
a pressing rotator that presses the fixing rotator to form, together with the fixing rotator, a nip portion through which the recording medium passes;
a fan that creates wind,
a duct that constitutes a flow passage for air flow from the fan between the surface of the pressurizing rotating body,
The speed of the air flowing between the surface of the pressure rotating body and the duct is a direction perpendicular to the conveying direction of the recording medium and a direction transverse to the conveyed recording medium. varies along the direction of
The duct is
a main body provided along the surface of the pressurizing rotor and forming a flow path for the air generated by the fan between the pressurizing rotor and the surface of the pressurizing rotor;
a discharge port for discharging the air flowing between the surface of the pressure rotating body and the main body in a direction away from the surface of the pressure rotating body;
a partition that divides the discharge port into the plurality of openings arranged in the CD direction,
further comprising a grid-shaped wire provided in each of the plurality of openings,
Each of the plurality of openings is divided into a plurality of sections by the wire,
wherein the average area of each of the plurality of sections in some of the plurality of openings is different from the average area of each of the plurality of sections in other openings of the plurality of openings , image forming device. 5. The image forming apparatus according to claim 4 , wherein the velocity of air flowing through each of said plurality of openings increases as the average area of each of said plurality of sections decreases. The duct is a protruding portion that protrudes from the body portion toward the surface of the pressure rotating body, and guides the air flowing between the surface of the pressure rotating body and the body portion to the discharge port. The image forming apparatus according to any one of claims 1 to 5 , further comprising a protrusion. 1. Further comprising a sensor provided at a position corresponding in the CD direction to the position of the opening through which the air flows at the slowest speed among the plurality of openings and detecting the temperature of the fixing rotator. 7. The image forming apparatus according to any one of 6 . 8. The image forming apparatus according to claim 7 , wherein said sensor is provided at a position corresponding in said CD direction to a position where said recording medium does not pass on the surface of said pressure rotating body. 9. The image forming apparatus according to claim 7 , wherein said heating member stops heating said fixing rotator when the temperature detected by said sensor exceeds a predetermined temperature. 10. The image forming apparatus according to any one of claims 7 to 9 , further comprising a windbreak member provided on the upstream side of the sensor in the rotation direction of the fixing rotator and reducing wind generated by the fan hitting the sensor. The height of some of the plurality of openings along the rotation direction of the pressing rotor is equal to the height of other openings of the plurality of openings along the rotation direction of the pressing rotor. 11. The image forming apparatus according to any one of claims 1 to 10 , wherein the height is different from the height of the image forming apparatus. 12. The image forming apparatus according to claim 11 , wherein the speed of air flowing through each of said plurality of openings increases as said height decreases. The air inlet port of the fan is composed of the pressurizing rotor and the downstream end of the main body along the rotating direction of the pressurizing rotor,
The image forming apparatus according to any one of claims 2 to 12 , wherein the discharge port is provided upstream of the introduction port in the rotational direction of the pressure rotating member. 14. The recording medium according to any one of claims 1 to 13 , further comprising a shutter for adjusting an area on the surface of the pressure rotating body to which air is blown by the fan according to the width of the recording medium passing through the nip portion in the CD direction. The image forming apparatus according to any one of . said duct is plural,
Each of the plurality of ducts is arranged along the CD direction and sandwiches a plane that includes the center position of the pressing rotor in the CD direction and is perpendicular to the rotation axis of the pressing rotor. 15. The image forming apparatus according to any one of claims 1 to 14 , which is provided at a symmetrical position at . 2. The heating member heats the entire region in the CD direction of the fixing rotator and having a width larger than the width in the CD direction of the recording medium passing through the nip portion. 16. The image forming apparatus according to any one of 15 . 17. The heating member according to any one of claims 1 to 16 , wherein the heating member changes the width in the CD direction of the region of the fixing rotator to be heated according to the width in the CD direction of the recording medium passing through the nip portion. image forming device.

Images