JP2023085729A - Fixing device and image forming apparatus including the same - Google Patents

Abstract

To provide a fixing device that can separate a sheet from a pressure roller or a fixing roller while preventing an increase in manufacturing cost, and an image forming apparatus including the same.SOLUTION: A fixing device comprises a rotating body to be heated, a pressure rotating body, a heating unit, and a separation pawl. The separation pawl has a pair of recesses that are arranged side by side across the center of gravity in the longitudinal direction. The fixing device includes an oscillation shaft that is inserted into one of the pair of recesses to oscillatably support the separation pawl. The separation pawl oscillates by the self weight from a separation position where it separates from the rotating body to be heated or the pressure rotating body toward a contact position where it is in contact with the rotating body to be heated or the pressure rotating body. The oscillation direction of the separation pawl when the oscillation shaft is inserted into one of the pair of recesses and the oscillation direction when the oscillation shaft is inserted into the other are opposite to each other.SELECTED DRAWING: Figure 7

Description

The present invention relates to a fixing device and an image forming apparatus having the fixing device.

In order to fix a toner image on paper in an image forming apparatus, a fixing device is widely used in which a fixing roller or fixing belt (rotating body to be heated) and a pressure roller (rotating pressure) are pressed against each other to form a fixing nip portion. used. In this fixing device, the paper is passed through the fixing nip portion, and heat and pressure are applied to the toner image to melt and fix the toner image on the paper.

In the fixing device as described above, the paper may adhere to the fixing roller or the pressure roller (hereinafter referred to as the fixing roller or the like) due to the melted toner, and the paper may be wound as it is. Therefore, there is a configuration in which a separating claw is interposed between the sheet that has passed through the fixing nip portion and the fixing roller or the pressure roller, and the sheet is conveyed while the tip of the separating claw is brought into sliding contact with the fixing roller or the pressure roller. Proposed.

As an example of such a fixing device, Japanese Patent Application Laid-Open No. 2002-200001 discloses a fixing device that includes a fixing roller, a pressure roller, a separation claw, and an urging member. A rotating shaft protruding in the thickness direction is provided on both end surfaces of the separation claw in the thickness direction. A housing of the fixing device is provided with a bearing portion that supports the rotating shaft. The separation claw is supported by a bearing portion so as to be able to swing around the rotation shaft. The biasing member biases the separation claw toward the fixing roller so that the tip of the separation claw contacts the outer peripheral surface of the fixing roller.

JP-A-06-149114

Here, when the separation claw according to the fixing device of Patent Document 1 has a large pressing force with respect to the fixing roller, the contact portion between the separation claw and the pressure roller is severely worn. On the other hand, if the pressure contact force is small, the separation of the paper is deteriorated. Therefore, it is necessary to make the magnitude and direction of the biasing force of the biasing member substantially constant. As a result, the structure for bringing the separation claw into contact with the fixing roller becomes complicated, which may increase the manufacturing cost of the fixing device. SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a fixing device capable of separating paper from a pressure roller or a fixing roller, and an image forming apparatus having the same, while suppressing an increase in manufacturing cost.

In order to achieve the above object, a first configuration of the present invention is a fixing device comprising a heated rotating body, a pressurizing rotating body, a heating section, and a separation claw. The pressurizing rotator is pressed against the heated rotator to form a fixing nip portion. The heating unit heats the rotating body to be heated. The separation claw is arranged at a position close to at least one of the heated rotating body and the pressing rotating body, and separates the recording medium that has passed through the fixing nip portion from the heated rotating body or the pressing rotating body. The fixing device heats and presses the recording medium passing through the fixing nip to fuse and fix the unfixed toner image on the recording medium. The separation claw has a pair of recesses arranged in the longitudinal direction with the center of gravity interposed therebetween. The fixing device includes a swing shaft that is inserted into one of the pair of recesses to swingably support the separation claw. The separation claw swings by its own weight from a separated position away from the rotating body to be heated or the rotating body to be pressurized toward a contact position in contact with the rotating body to be heated or the rotating body to be pressurized. When the swing shaft is inserted into one of the pair of recesses and when the swing shaft is inserted into the other, the swing direction of the separation claw is opposite.

According to the first configuration of the present invention, the separation claw can swing from the separated position toward the contact position by its own weight. The swinging direction of the separation claw can be changed by selecting which of the pair of recesses the swing shaft is inserted into. Therefore, with a simple structure, the separation claw can stably come into contact with the rotating body to be heated or the rotating body to be pressurized according to the arrangement thereof. Therefore, it is possible to provide a fixing device capable of reliably separating the paper from the heated rotating body or the pressing rotating body while suppressing an increase in manufacturing cost.

Schematic cross-sectional view showing the internal structure of an image forming apparatus 100 in which a fixing device 13 according to the first embodiment of the present invention is mounted. FIG. 2 is a cross-sectional side view of the periphery of the fixing device 13 in FIG. 1; Enlarged plan view showing an enlarged separation claw 21 A cross-sectional view of the separation claw 21 cut along the AA cross-sectional line shown in FIG. FIG. 3 is an enlarged view of a contact portion between the separation claw 21 and the fixing roller 131 shown in FIG. 2; FIG. 2 is a plan view showing a state in which the conveying guide 32 is viewed from the opposite side of the guide surface 34; Enlarged view enlarging the periphery of the separation claw 21 FIG. 5 is an enlarged view showing an enlarged separation claw 21 according to the image forming apparatus 100 of the second embodiment; FIG. 11 is an enlarged view showing an enlarged separation claw 21 according to the image forming apparatus 100 of the third embodiment; An enlarged view showing the periphery of the separation claw 21 and the fixing nip portion N in the image forming apparatus 100 of the third embodiment. A side view of a fixing device showing a modified example of the fixing device 13 according to the embodiment.

A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing the internal structure of an image forming apparatus 100 equipped with a fixing device 13 according to the first embodiment of the invention. Four image forming units Pa, Pb, Pc, and Pd are provided in order from the upstream side in the transport direction (the left side in FIG. 1) in the main body of the image forming apparatus 100 (here, a color printer). These image forming units Pa to Pd are provided corresponding to images of four different colors (cyan, magenta, yellow and black). and black images are sequentially formed.

Photoreceptor drums (image bearing members) 1a, 1b, 1c and 1d for carrying visible images (toner images) of respective colors are disposed in these image forming portions Pa to Pd. An intermediate transfer belt 8 that rotates clockwise is provided adjacent to each of the image forming stations Pa to Pd. The toner images formed on these photoreceptor drums 1a to 1d are sequentially primary-transferred and superimposed on an intermediate transfer belt 8 that moves in contact with each of the photoreceptor drums 1a to 1d. After that, the toner image primarily transferred onto the intermediate transfer belt 8 is secondarily transferred onto a sheet S as an example of a recording medium by a secondary transfer roller 9 . Further, the sheet S on which the toner image has been secondarily transferred is ejected from the main body of the image forming apparatus 100 after the toner image is fixed by the fixing device 13 . A main motor (not shown) rotates the photosensitive drums 1a to 1d in the clockwise direction in FIG. 1, and an image forming process is performed on each of the photosensitive drums 1a to 1d.

The paper S onto which the toner image is to be secondarily transferred is accommodated in a paper cassette 16 arranged at the bottom of the main body of the image forming apparatus 100, and is transferred to the secondary transfer roller 9 via a paper feed roller 12a and a pair of registration rollers 12b. and the driving roller 11 of the intermediate transfer belt 8 . A dielectric resin sheet is used for the intermediate transfer belt 8, and a seamless belt is mainly used. Further, a blade-shaped belt cleaner 19 for removing toner remaining on the surface of the intermediate transfer belt 8 is arranged on the downstream side of the secondary transfer roller 9 .

Next, the image forming units Pa to Pd will be described. Charging devices 2a, 2b, 2c and 2d, an exposure device 5, developing devices 3a, 3b, 3c and 3d, and a cleaning device 7a are provided around and below the rotatably arranged photosensitive drums 1a to 1d. , 7b, 7c and 7d are provided. The charging devices 2a-2c charge the photosensitive drums 1a-1d. The exposure device 5 exposes each of the photosensitive drums 1a to 1d with image information. The developing devices 3a-3d form toner images on the photosensitive drums 1a-1d. The cleaning devices 7a-7d remove developer (toner) and the like remaining on the photosensitive drums 1a-1d.

When image data is input from a host device such as a personal computer, first, the surfaces of the photosensitive drums 1a to 1d are uniformly charged by the charging devices 2a to 2d. Then, the exposure device 5 irradiates the photosensitive drums 1a to 1d with light according to image data to form electrostatic latent images according to the image data on the photosensitive drums 1a-1d. Each of the developing devices 3a to 3d is filled with a predetermined amount of two-component developer containing toner of each color of cyan, magenta, yellow and black. When the ratio of the toner in the two-component developer filled in each of the developing devices 3a to 3d falls below a specified value due to the formation of a toner image, which will be described later, each of the developing devices 3a to 3d is removed from the toner containers 4a to 4d. Toner is supplied to the The toner in the developer is supplied onto the photosensitive drums 1a to 1d by the developing devices 3a to 3d, and adheres electrostatically to an electrostatic latent image formed by exposure from the exposure device 5. A toner image is formed.

Then, an electric field is applied between the primary transfer rollers 6a to 6d and the photosensitive drums 1a to 1d by the primary transfer rollers 6a to 6d with a predetermined transfer voltage, and the cyan, magenta, yellow and yellow colors on the photosensitive drums 1a to 1d are transferred. A black toner image is primarily transferred onto the intermediate transfer belt 8 . These four-color images are formed with a predetermined positional relationship for predetermined full-color image formation. After that, in preparation for subsequent formation of new electrostatic latent images, cleaning devices 7a to 7d remove toner and the like remaining on the surfaces of the photosensitive drums 1a to 1d after the primary transfer.

The intermediate transfer belt 8 is stretched over a driven roller 10 on the upstream side and a driving roller 11 on the downstream side. A belt driving motor (not shown) is connected to the driving roller 11 to apply rotational driving force to the driving roller 11 . When the drive roller 11 is rotated by the belt drive motor, the intermediate transfer belt 8 starts rotating counterclockwise along with the rotation of the drive roller 11 . After that, the sheet S is conveyed from the registration roller pair 12b to the nip portion (secondary transfer nip portion) between the drive roller 11 and the secondary transfer roller 9 provided adjacent thereto at a predetermined timing. Then, the full-color image on the intermediate transfer belt 8 is secondarily transferred onto the paper S. FIG. The sheet S on which the toner image has been secondarily transferred is conveyed to the fixing device 13 .

The sheet S conveyed to the fixing device 13 is heated and pressed by a fixing roller 131 (rotating member to be heated) and a pressure roller 132 (rotating member to be pressed, see FIG. 2) to form a toner image on the surface of the sheet S. The toner is fixed to form a predetermined full-color image. The sheet S on which the full-color image is formed is divided in the conveying direction by the branching unit 14 branching in a plurality of directions, and is sent to the double-sided conveying path 18 as it is (or after the images are formed on both sides thereof), and is sent to the pair of discharge rollers. 15 to the ejection tray 17 .

FIG. 2 is a side cross-sectional view around the fixing device 13 in FIG. The fixing device 13 employs a fixing method using a heat source of an electromagnetic induction heating method. As shown in FIG. 2, the fixing device 13 includes a fixing roller 131, a pressure roller 132, an induction heating section 133 (heating section), a separation claw 21, a rotating shaft 30, a regulating member 31, and a conveying guide. 32 (see FIG. 5).

The fixing roller 131 is rotatably held in the housing of the fixing device 13 . The fixing roller 131 includes a base material 131a, an elastic layer 131d, a release layer 131e, a heat insulating layer 131b, and an induction heating layer 131c. The fixing roller 131 is composed of an elastic layer 131d, an induction heating layer 131c, a heat insulating layer 131b, and a base material 131a in this order from a release layer 132c, which forms the outer peripheral surface of the fixing roller 131, toward the inner side in the radial direction of the fixing roller 131. It is constructed by stacking. The base material 131a is made of stainless steel and has a cylindrical shape. The elastic layer 131d is made of silicone rubber sponge for imparting elasticity to the fixing nip portion N that is pressed against the pressure roller 132. As shown in FIG. The release layer 131e is a tube-shaped layer that covers the surface of the elastic layer 131d with fluororesin.

The pressure roller 132 is provided at a position facing the fixing roller 131 . The pressure roller 132 includes a base material 132a, an elastic layer 132b, and a release layer 132c. With respect to the radial direction of the pressure roller 132, the release layer 132c, the elastic layer 132b, and the base material 132a are laminated in this order from the outside. The base material 132a is a metal core made of aluminum. The base material 132 a is rotatably supported by the housing of the fixing device 13 . The elastic layer 132b is a layer made of silicon rubber and formed on the base material 132a. The elastic layer 132b provides the fixing nip portion N with elasticity. The release layer 132c is a tube-shaped layer that covers the surface of the elastic layer 132b with fluororesin. The release layer 131e and the release layer 132c facilitate separation of the sheet S from the fixing roller 131 and the pressure roller 132 when the unfixed toner image is melted and fixed at the fixing nip portion N. FIG.

The pressure roller 132 is rotationally driven by a drive source (not shown) such as a motor, and is further pressed toward the radial center of the fixing roller 131 . As a result, the pressure roller 132 is in pressure contact with the fixing roller 131 . When the pressure roller 132 rotates, the fixing roller 131 rotates through the fixing nip portion N in the same direction.

The induction heating unit 133 includes an exciting coil 133a, a hobbin 133b, and a core 133c, and heats the fixing roller 131 by electromagnetic induction. The induction heating units 133 are arranged to face each other so as to surround part of the outer periphery of the fixing roller 131 and extend in the axial direction of the fixing roller 131 .

The excitation coil 133a is made of copper wire and wound around a hobbin 133b. The excitation coil 133a is connected to a high voltage power supply (not shown) and generates magnetic flux by a high frequency current supplied from the high voltage power supply. This magnetic flux generates an eddy current in the induction heating layer 131c. Then, Joule heat is generated by electrical resistance in the induction heating layer 131c, and the induction heating layer 131c generates heat. The induction heating layer 131 c is connected to a temperature sensor 134 capable of measuring the temperature of the outer peripheral surface of the fixing roller 131 . The induction heating layer 131 c controls the power of the high-voltage power supply based on the temperature detected by the temperature sensor 134 to adjust the temperature of the outer circumferential surface of the fixing roller 131 .

When the sheet S is passed through the fixing nip portion N with the fixing roller 131 heated to a predetermined temperature, the sheet S sandwiched by the fixing nip portion N is heated and pressed by the pressure roller 132 . be done. As a result, the powdery toner on the paper S is fused and fixed.

The sheet S on which the toner has been fixed is discharged from the discharge roller pair 15 to the discharge tray 17 (see FIG. 1 for both) through the fixing transport roller pair 20 .

Next, the separation claw 21 of the first embodiment will be described in detail. FIG. 3 is an enlarged plan view showing the separation claw 21 in an enlarged manner. FIG. 4 is a cross-sectional view of the separation claw 21 cut along the AA cross-sectional line shown in FIG. FIG. 5 is an enlarged view of the contact portion between the separation claw 21 and the fixing roller 131 shown in FIG. Note that the longitudinal direction of the separation claw 21 (horizontal direction shown in FIG. 3) is hereinafter simply referred to as the "longitudinal direction". Also, the direction perpendicular to the longitudinal direction (vertical direction shown in FIG. 3) is hereinafter simply referred to as the "width direction". Further, the direction along the rotating shaft 30 (details will be described later) perpendicular to the longitudinal direction and the width direction (the direction of the paper surface shown in FIG. 3) is hereinafter simply referred to as the "axial direction".

As shown in FIGS. 2 and 5, the separation claw 21 is arranged on the downstream side of the fixing nip portion N with respect to the sheet conveying direction. Further, the separation claw 21 is positioned closer to the fixing roller 131 than the pressure roller 132 with respect to the facing direction of the fixing roller 131 and the pressure roller 132 . Separation claw 21 is made of a heat-resistant resin (for example, polyimide or the like).

As shown in FIG. 3, the separation claw 21 is elongated in one direction (longitudinal direction). The separation claw 21 includes a front end portion 22, a rear end portion 25, and a pair of concave portions 23a and 23b.

The tip 22 is formed at one longitudinal end of the separation claw 21 (here, the right end in FIG. 3). The distal end portion 22 has a tapered shape in which the dimension in the width direction becomes smaller toward the extreme end portion in the longitudinal direction. A rear end portion 25 is formed at the end portion on the side opposite to the front end portion 22 in the longitudinal direction. The rear end portion 25 has a constant width dimension toward the extreme end portion in the longitudinal direction.

The pair of recessed portions 23a and 23b are arranged in the longitudinal direction with the center of gravity CG of the separation claw 21 interposed therebetween. In the present embodiment, for convenience of explanation, one of the pair of concave portions 23a and 23b into which the rotating shaft 30 described later is inserted (in this embodiment, the side closer to the rear end portion 25 than the center of gravity CG in the longitudinal direction) ) is defined as a first recess 23a, and the other is defined as a second recess 23b.

The first recessed portion 23a is recessed inward (upper side in FIG. 3) from one side portion (lower side in FIG. 3) in the width direction. The bottom portion (the innermost portion in the width direction) of the first concave portion 23a is formed in an arc shape in plan view in the axial direction. The second recessed portion 23b is recessed inward (lower side in FIG. 3) from the other side portion (upper surface in FIG. 3) in the width direction. The widthwise bottom of the second recessed portion 23b (the inner portion with respect to the widthwise direction) is formed in an arc shape in plan view in the axial direction. The inner peripheral surface of the second recess 23b is formed with an inclined surface 26 that linearly inclines outward in the width direction (upper side in FIG. 3) from the bottom toward the tip 22 in the longitudinal direction.

As shown in FIGS. 3 and 4, the inner peripheral surface of the first recess 23a is recessed in the central portion along the axial direction, and sliding protrusions 29 are formed on both sides of the recessed portion. there is The sliding projection 29 is formed in an arc shape in plan view in the axial direction (plan view shown in FIG. 3). Two similar sliding protrusions 29 are also provided in the second recess 23b so as to be aligned in the axial direction.

As shown in FIG. 3 , the separation claw 21 has a first protrusion 27 and a second protrusion 28 . The first protruding portion 27 protrudes outward in the width direction from one side portion of the separation claw 21 in the width direction. The first protrusion 27 is adjacent to the first recess 23a in the longitudinal direction. The second protrusion 28 protrudes outward in the width direction from the other side of the separation claw 21 in the width direction (the side opposite to the side on which the first protrusion 27 is provided). . The second protrusion 28 is adjacent to the second recess 23b in the longitudinal direction.

The rotating shaft 30 is a cylindrical shaft extending along the axial direction of the fixing roller 131 . As shown in FIG. 5, the rotating shaft 30 is positioned downstream of the fixing nip portion N and closer to the fixing roller 131 than the pressure roller 132 with respect to the direction in which the fixing roller 131 and the pressure roller 132 face each other. and fixed to a housing (not shown) of the fixing device 13 .

As shown in FIG. 5 , the rotation shaft 30 rotates the first concave portion 23 a (of the pair of concave portions 23 a and 23 b ) in a state where the tip end portion 22 of the separation claw 21 is directed toward the pressure roller 132 . farther from the nip portion N). The outer peripheral surface of the rotating shaft 30 is in contact with the inner peripheral surface of the first recess 23a. More specifically, the outer peripheral surface of the rotary shaft 30 abuts on the tips of a pair of sliding protrusions 29 formed on the inner peripheral surface of the first recess 23a. The separation claw 21 is supported by the rotating shaft 30 so as to be swingable along the circumferential direction centering on the rotating shaft 30 .

The separation claw 21 can swing between a contact position P1 and a separation position P2 (see FIG. 7 for both). When the separation claw 21 swings, the outer peripheral surface of the rotating shaft 30 and the tip of the sliding projection 29 slide. The contact position P<b>1 is the position where the separation claw 21 swings clockwise due to its own weight and the tip portion 22 contacts the outer peripheral surface of the fixing roller 131 , as described above. The separated position P<b>2 is a position where the separation claw 21 swings in the direction opposite to the rotation due to its own weight, and the leading end portion 22 separates from the outer peripheral surface of the fixing roller 131 . The details of swinging of the separation claw 21 will be described later.

As shown in FIG. 5, the regulating member 31 is fixed to the housing of the fixing device 13 at a position closer to the pressure roller 132 than the rotating shaft 30 with respect to the direction in which the fixing roller 131 and the pressure roller 132 face each other. . The restricting member 31 is elongated along the axial direction of the rotating shaft 30 . The regulating member 31 is inserted into the second recess 23b. The restricting member 31 is preferably formed in the same shape as the rotating shaft 30 , that is, formed in a cylindrical shape having the same diameter as the rotating shaft 30 .

FIG. 6 is a plan view showing a state in which the conveying guide 32, which will be described later, is viewed from the side opposite to the guide surface 34. As shown in FIG. The direction along the vertical direction in FIG. 6 is the paper transport direction. As shown in FIGS. 5 and 6, it is preferable to employ a configuration in which the restricting member 31 is provided with a pair of axial movement restricting ribs 37 arranged in the axial direction with the separation claw 21 interposed therebetween. The axial movement restricting rib 37 contacts the separation claw 21 when the separation claw 21 moves in the axial direction, and restricts the movement of the separation claw 21 in the axial direction.

As shown in FIGS. 5 and 6, the transport guide 32 is fixed to the housing (not shown) of the fixing device 13 at a position overlapping the separation claw 21 in the paper transport direction. The transport guide 32 has a pair of guide plates 33 . The pair of guide plates 33 are arranged axially with the separation claw 21 interposed therebetween. The guide plate 33 is a plate-like body elongated with respect to the sheet conveying direction. The guide plate 33 is curved so as to swell toward a bow shape on one side in the horizontal direction (the right side in FIG. 5, the pressure roller 132 side). The guide plate 33 has a guide surface 34 that faces the sheet S that has passed through the fixing nip portion N. As shown in FIG. After passing through the fixing nip portion N, the sheet S slides on the guide surface 34 and is guided downstream in the sheet conveying direction.

Both ends of the guide plate 33 are positioned inside the leading end portion 22 and the trailing end portion 25 of the separation claw 21 with respect to the sheet conveying direction. That is, the tip portion 22 of the separation claw 21 protrudes further upstream than the upstream end portion of the guide plate 33 in the sheet conveying direction. Further, the rear end portion 25 of the separation claw 21 protrudes further downstream than the downstream end portion of the guide plate 33 in the sheet conveying direction.

The rotating shaft 30 and the regulating member 31 described above can adopt a configuration formed integrally with the transport guide 32 . Specifically, the rotation shaft 30 is a tip portion of a first support member 35 that extends from the back surface of the guide plate 33 (the surface opposite to the guide surface 34) toward the other side in the horizontal direction (the left side in FIG. 5). connected to. Similarly, the regulation member 31 is connected to the tip portion of a second support member 36 extending from the rear surface of the guide plate 33 toward the other side in the horizontal direction.

When assembling the fixing device 13, the separation claw 21 is inserted downward from above between the rotation shaft 30 and the regulation member 31 with the tip portion 22 positioned downward. Then, the rotary shaft 30 is inserted into the first recess 23a, and the restricting member 31 is inserted into the second recess 23b.

Next, swinging of the separation claw 21 will be described in detail. As shown in FIG. 5, in the separation claw 21 of the fixing device 13 according to this embodiment, the center of gravity CG is shifted to one side in the horizontal direction with respect to the rotation shaft 30 (here, the right side, the pressure roller 132 side). there is Therefore, the separation claw 21 rotates clockwise (broken line arrow in FIG. 5) about the rotation shaft 30 by its own weight so that the rotation shaft 30 and the center of gravity CG are aligned with each other in the vertical direction. (rocking) trying to Then, the tip portion 22 of the separation claw 21 comes into contact with the outer peripheral surface of the fixing roller 131 .

Conversely, as shown in FIG. 7, when the sheet S guided by the transport guide 32 contacts the rear end portion 25 of the separation claw 21, the transport force of the sheet S causes the separation claw 21 to swing by its own weight. direction. Then, the separation claw 21 tries to rotate (swing) counterclockwise around the rotation shaft 30 (in the direction of the dashed arrow in FIG. 7). Here, the restricting member 31 is located upstream of the second recess 23b with respect to the swinging direction of the separation claw 21 due to its own weight. Therefore, when the separation claw 21 swings from the contact position P1 (the position indicated by the broken line in FIG. 7) to the separation position P2 (the position indicated by the solid line in FIG. It abuts on the outer peripheral surface, and the rocking movement is restricted.

In the state where the separation claw 21 is at the contact position P1, if the sheet S that has passed through the fixing nip portion N sticks to the fixing roller 131, the leading edge of the sheet S (the edge on the downstream side in the sheet conveying direction) is It contacts the tip 22 of the separation claw 21 and separates from the fixing roller 131 .

The separation claw 21 according to the image forming apparatus 100 of this embodiment can swing by its own weight from the separation position P2 toward the contact position P1. Therefore, it is possible to bring the separation claw 21 into contact with the fixing roller 131 with a simple configuration. Therefore, it is possible to provide the fixing device 13 capable of releasing the sheet S from the fixing roller 131 and the image forming apparatus 100 including the fixing device 13 while suppressing an increase in manufacturing cost.

Here, the separation claw 21 of the conventional fixing device 13 is provided with rotating shafts protruding on both sides in the width direction, and the rotating shafts are supported by bearings provided in the housing of the fixing device 13 . On the other hand, the separation claw 21 according to the fixing device 13 of the present invention is pivotably supported by a rotating shaft 30 integrally formed with a conveying guide 32 inserted into the first concave portion 23a. Therefore, the weight of the separation claw 21 can be reduced by the weight of the rotating shaft as compared with the conventional separation claw 21 described above. Then, the contact pressure of the separation claw 21 against the fixing roller 131 can be reduced. As a result, wear of the fixing roller 131 can be reduced, and the durability of the fixing device 13 can be improved.

Moreover, the separation claw 21 is made of heat-resistant resin, which is more expensive than general resin materials. Therefore, by reducing the weight of the separation claw 21 by the weight of the rotating shaft as described above, it is possible to reduce the amount of heat-resistant resin required for the separation claw 21, and the material cost can be reduced. .

Further, as described above, the separation claw 21 swings toward the contact position P1 due to its own weight. Therefore, the magnitude of the contact pressure of the separation claw 21 on the fixing roller 131 is based on the weight of the separation claw 21 and is substantially constant. Therefore, by adjusting the weight of the separation claw 21 , it is possible to prevent the contact pressure from becoming excessively large, and it is possible to prevent wear of the outer peripheral surfaces of the tip portion 22 and the fixing roller 131 .

Further, as described above, the center of gravity CG is positioned between the first recess 23a and the second recess 23b in the longitudinal direction. Therefore, with a simple structure, the separation claw 21 swings from the separation position P2 to the contact position P1 by its own weight, and the manufacturing cost of the fixing device 13 can be suppressed more effectively.

Further, as described above, a pair of sliding protrusions 29 are provided in the first recess 23a and the second recess 23b. Therefore, the outer peripheral surface of the rotating shaft 30 contacts only the tips of the pair of sliding projections 29 . As a result, the contact area between the rotating shaft 30 and the first concave portion 23a can be reduced, and the frictional force when the rotating shaft 30 swings can be reduced. As a result, wear of the separation claw 21 and the rotating shaft 30 can be suppressed, and the durability of the fixing device 13 can be improved.

Further, as described above, the sheet S guided by the transport guide 32 contacts the rear end portion 25 of the separation claw 21, and the separation claw 21 swings from the contact position P1 toward the separation position P2. Therefore, it is possible to prevent the contact pressure between the separation claw 21 and the fixing roller 131 from becoming too high due to the weight of the separation claw 21, and to reduce the contact time between the separation claw 21 and the fixing roller 131. Become. Thereby, abrasion of the outer peripheral surface of the fixing roller 131 can be suppressed. Note that when the leading edge of the sheet S is separated from the fixing roller 131 and guided by the transport guide 32, the leading edge 22 of the separation claw 21 and the sheet S basically do not contact each other. Therefore, even if the separation claw 21 is positioned at the separation position P2 in this state, the separation of the sheets S is less likely to be affected.

Further, as described above, the restricting member 31 is inserted into the second recess 23b. When the separation claw 21 swings from the contact position P1 to the separation position P2, the regulation member 31 comes into contact with the bottom surface (sliding projection 29) of the second recess 23b and regulates the swinging of the separation claw 21. As shown in FIG. Therefore, it is possible to suppress the swinging of the separation claw 21 from increasing, and to suppress the rotation shaft 30 from coming out of the first concave portion 23a and the separation claw 21 from falling off.

Further, when the fixing device 13 is assembled, the regulating member 31 restricts the swinging motion of the separation claw 21, so that the separation claw 21 is less likely to come off. Therefore, the ease of assembly of the fixing device 13 is improved. Also, when the fixing device 13 or the image forming apparatus 100 including the fixing device 13 is transported, even if the separation claw 21 is shaken due to vibration during transportation, the restriction member 31 prevents the separation claw 21 from falling off. .

Further, as described above, the inclined surface 26 is provided in the second recess 23b. Therefore, when the restricting member 31 is inserted into the second recess 23b or removed from the second recess 23b, the restricting member 31 can be slid on the inclined surface 26 to be inserted or removed. Therefore, the attachment of the separation claw 21 is facilitated, and the assembly efficiency of the fixing device 13 is improved.

Next, the image forming apparatus 100 of the second embodiment will be described. In addition, below, the difference with 1st Embodiment is described, the same code|symbol is attached|subjected to the structure similar to 1st Embodiment, and description is abbreviate|omitted. FIG. 8 is an enlarged view showing the separation claw 21 according to the image forming apparatus 100 of the second embodiment.

As shown in FIG. 8, the separation claw 21 according to the image forming apparatus 100 of the second embodiment is formed in a rotationally symmetrical shape about the center in the longitudinal and width directions. That is, the front end portion 22 and the rear end portion 25 of the separation claw 21 have a shape reversed in the longitudinal direction and the width direction in plan view along the axial direction. Also, the first recess 23a and the second recess 23b have the same shape. The first recessed portion 23a has an inclined surface 26 similarly to the second recessed portion 23b.

By doing so, it is not necessary to match the direction when attaching the separation claw 21 to the housing (not shown) of the fixing device 13 . That is, the first concave portion 23a is on the side closer to the fixing roller 131 and the second concave portion 23b is on the side farther from the fixing roller 131, and the first concave portion 23a is on the passing side from the fixing roller 131 and the second concave portion 23b is attached. is installed on the side closer to the fixing roller 131, there is substantially no difference. Therefore, attachment of the separation claw 21 is facilitated, and assembling efficiency of the fixing device 13 is improved.

Next, the image forming apparatus 100 of the third embodiment will be described. In addition, below, the difference with 1st Embodiment is described, the same code|symbol is attached|subjected to the structure similar to 1st Embodiment, and description is abbreviate|omitted. FIG. 9 is an enlarged view showing the separation claw 21 according to the image forming apparatus 100 of the third embodiment. FIG. 10 is an enlarged view showing the periphery of the separation claw 21 and the fixing nip portion N of the image forming apparatus 100 of the third embodiment.

As shown in FIG. 9, the separation claw 21 according to the image forming apparatus 100 of the third embodiment is formed in a rotationally symmetrical shape about the center in the longitudinal and width directions, as in the second embodiment. The separation claw 21 of this embodiment has a pair of curved surface portions 38 .

As shown in FIGS. 9 and 10, the curved surface portions 38 are formed at the front end portion 22 and the rear end portion 25, and project outward in the width direction compared to other portions of the separation claw 21. ing. The curved surface portion 38 formed on the front end portion 22 and the curved surface portion 38 formed on the rear end portion 25 protrude in opposite directions. The curved surface portion 38 is formed in an arc-shaped R shape in plan view along the axial direction (side view of the separation claw 21). It is formed at one edge portion in the width direction of the front end portion 22 and the rear end portion 25 . The curved surface portion 38 is in contact with the outer peripheral surface of the fixing roller 131 while the separation claw 21 is at the contact position P<b>1 .

An end surface 39 substantially parallel to the width direction is formed on the longitudinally outer side (fixing roller 131 side) of the curved surface portion 38 formed on the tip portion 22 . A gap L is formed between the end surface 39 (the end of the curved surface portion 38 on the side closer to the fixing nip portion N) and the outer peripheral surface of the fixing roller 131 when the separation claw 21 is at the contact position P1. . The dimension of the gap L along the transport direction is preferably 0.1 mm or less.

As described above, the separation claw 21 of the present embodiment has the curved surface portion 38 in contact with the outer peripheral surface of the fixing roller 131 when the separation claw 21 is at the contact position P1. Therefore, when the fixing roller 131 rotates, the tip portion 22 easily slides on the outer peripheral surface of the fixing roller 131 . Therefore, the wear of the outer peripheral surface of the fixing roller 131 and the tip portion 22 can be suppressed, and the durability of the fixing device 13 can be improved.

Further, the separation claws 21 of this embodiment and others are formed in a rotationally symmetrical shape centering on the central portion in the longitudinal direction and the width direction, as in the second embodiment. Therefore, as in the second embodiment, the ease of assembly of the fixing device 13 is improved.

In addition, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the present invention. For example, in each of the above-described embodiments, the roller heating type fixing device 13 having the fixing roller 131 as the heated rotating member was exemplified. A fixing device having a heated rotating body other than the roller 131 can be similarly applied. Moreover, the heating method is not limited to the induction heating method using the induction heating unit 133 including the exciting coil and the core, and for example, a halogen heater can be used as the heating unit.

2, the fixing device 13 according to each of the above-described embodiments is of a vertical conveyance method (the facing direction of the fixing roller 131 and the pressure roller 132 is the horizontal direction, and the sheet S passing through the fixing nip portion N is However, as shown in FIG. 11, a horizontal transport method (where the fixing roller 131 and the pressure roller 132 face each other is in the vertical direction). , and a method in which the sheet S passing through the fixing nip portion N is conveyed in the lateral direction (horizontal direction) can be adopted.

As shown in FIG. 11, when the horizontal transport method is adopted and the separation claw 21 is arranged at a position close to the fixing roller 131 arranged above, the fixing roller The side closer to 131 is defined as first recess 23a, and the side farther from 131 is defined as second recess 23b. That is, the positional relationship between the first concave portion 23a and the second concave portion 23b is opposite to that of each of the above-described embodiments. In this case, the center of gravity CG of the separation claw 21 is located on the upper left of the rotating shaft 30 . Therefore, the separating claw 21 swings counterclockwise in the figure about the rotating shaft 30 by its own weight so that the center of gravity CG is aligned with the center of the rotating shaft 30 in the vertical direction. Therefore, the separating claw 21 is oscillated in the opposite direction to the above embodiments.

Further, although the separation claw 21 according to the image forming apparatus 100 of each of the above embodiments is arranged at a position closer to the fixing roller 131 than the fixing roller 131 or the pressure roller 132 , It can be placed in the position where the For example, when performing double-sided printing, a heated toner image immediately after fixing is formed on the surface of the sheet S on the pressure roller 132 side. The sheet S can be separated from the pressure roller 132 by the separation claw 21 . As a result, it is possible to prevent the paper S from being wound around the pressure roller 132 with a simple configuration.

The present invention relates to a fixing device in which a recording medium is passed through a fixing nip formed by a heated rotating body and a pressure rotating body, and heat and pressure are applied to the toner image to melt and fix the toner image on the recording medium. Available. By using the present invention, it is possible to provide a fixing device capable of separating a recording medium from a rotating body with a simple configuration and suppressing an increase in manufacturing cost, and an image forming apparatus having the fixing device.

13 Fixing Device 21 Separation Claw 22 Tip 23a First Concave 23b Second Concave 29 Sliding Protrusion 30 Rotating Shaft 31 Regulating Member 32 Conveying Guide 37 Shaft Movement Regulating Rib 38 Curved Surface Part 100 Image Forming Apparatus 131 Fixing Roller (rotating member to be heated) )
132 pressure roller (pressure rotating body)
CG Center of gravity L Gap P1 Contact position P2 Separation position

Claims (10)

a rotating body to be heated;
a pressurizing rotator that is pressed against the heated rotator to form a fixing nip;
a heating unit that heats the rotating body to be heated;
a separation claw disposed at a position close to at least one of the heated rotating body and the pressing rotating body and separating the recording medium that has passed through the fixing nip portion from the heated rotating body or the pressing rotating body;
A fixing device that melts and fixes an unfixed toner image on the recording medium by heating and pressurizing the recording medium passing through the fixing nip,
The separation claw has a pair of concave portions arranged with the center of gravity in between in the longitudinal direction,
a swing shaft that is inserted into one of the pair of recesses and that swingably supports the separation claw;
the separation claw swings by its own weight from a separated position away from the heated rotating body or the pressurizing rotating body toward a contact position in contact with the heated rotating body or the pressurizing rotating body;
A fixing device, wherein the swinging direction of the separating claw is opposite when the swinging shaft is inserted into one of the pair of recesses and when the swinging shaft is inserted into the other of the pair of recesses. The recess has a pair of sliding projections formed in an arc shape in a side view along the inner peripheral surface of the recess and arranged along the axial direction of the swing shaft, and the swing shaft is inserted into the recess. 2. The fixing device according to claim 1, wherein the outer peripheral surface of said rotary shaft contacts and slides on said sliding projection in the state of being held. The pair of concave portions are formed point-symmetrically with respect to central points located at the center in the longitudinal direction and the center in the width direction orthogonal to the longitudinal direction when the separation claw is viewed from the axial direction of the swing shaft. 3. The fixing device according to claim 1, wherein the fixing device comprises: 4. The fixing device according to claim 3, wherein the separation claw is formed point-symmetrically with respect to the center point. Of the pair of recesses, the recess into which the swing shaft is inserted is referred to as a first recess, and the recess into which the swing shaft is not inserted is referred to as a second recess. a rotation restricting member positioned upstream of the second recess with respect to the swinging direction of the separation claw due to its own weight;
The separation pawl is regulated from swinging by contact between the second concave portion and the rotation restricting member in a state of swinging from the contact position toward the separation position by a predetermined angle. Item 5. The fixing device according to any one of Items 1 to 4. Of both ends of the separation claw in the insertion direction, an end portion on a side closer to the fixing nip portion is formed with a curved surface portion having an R shape in a side view,
6. The fixing device according to claim 1, wherein when the separation claw is at the contact position, the curved surface portion is in contact with the rotating body to be heated or the pressing rotating body. When the separation claw is in the contact position, the distance between the end portion of the curved portion on the side closer to the fixing nip portion and the outer peripheral surface of the heating rotating member or the pressing rotating member is 0.1 mm or less. 7. The fixing device according to claim 6, wherein a gap of is provided. a conveying guide that overlaps the separation claw in the insertion direction of the recording medium and guides the recording medium that has passed through the fixing nip portion to the downstream side in the insertion direction;
the separation claw has a downstream projecting portion that projects further downstream than the conveying guide in the insertion direction;
3. A biasing force in a direction from the contact position toward the separation position is applied to the separation claw when the recording medium guided by the transport guide comes into contact with the downstream projecting portion. 8. The fixing device according to any one of 1 to 7. 9. The fixing device according to claim 1, wherein the separation claw is provided close to the heating rotator of the heating rotator and the pressure rotator. An image forming apparatus comprising the fixing device according to claim 1 .

Images