JP2024037245A - Fixing device and image forming device equipped with it - Google Patents

Abstract

An object of the present invention is to provide a fixing device that can suppress damage to the outer circumferential surface of a pressurizing rotary body or a heated rotary body that comes into contact with a separation claw. A fixing device includes a rotating body to be heated, a pressing rotating body, a heating section, and a separating claw. The pressure rotating body is pressed against the heated rotating body to form a fixing nip. The separation claw swings between a separated position and a contact position. The fixing device includes a biasing member. The separation claw is always placed in the contact position due to its own weight or the biasing force of the biasing member. [Selection diagram] Figure 4

Description

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

2. Description of the Related Art In order to fix a toner image on a sheet of paper in an image forming apparatus, a fixing device that heats and presses the sheet to melt and fix the unfixed toner image on the sheet is widely used. In such a fixing device, a fixing roller or a fixing belt (heated rotating body) and a pressure roller (pressing rotating body) come into pressure contact to form a fixing nip. When the paper passes through this fixing nip, heat and pressure are applied to the unfixed toner image on the paper, and the toner image is melted and fixed onto the paper.

In the above-described fixing device, 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 wind around the fixing roller or the like. Therefore, a configuration has been proposed in which a separating claw is provided between the paper that has passed through the fixing nip and the fixing roller or the pressure roller. In this configuration, the paper passes through the fixing nip section with the tip of the separation claw in sliding contact with the fixing roller or pressure roller, is separated from the fixation roller or pressure roller by the separation claw, and is then conveyed to the downstream side. be done.

As an example of such a fixing device, Patent Document 1 discloses one including a fixing roller, a pressure roller, a separation claw, and a biasing member. The separation claw is supported so as to be swingable about a swing axis parallel to the rotation axis of the fixing roller. The biasing member is an elastic member (a spring member such as a coil spring). The urging member urges the separating claw toward the outer peripheral surface of the fixing roller or the pressure roller so that the tip end of the separating claw comes into contact with the outer peripheral surface of the fixing roller or the pressure roller.

By the way, in such a fixing device, the urging force of the urging member is too strong, and the separating claw may damage the outer circumferential surface of the fixing roller or the pressure roller, or the outer circumferential surface or the tip of the separating claw may become severely worn. There is a risk of Therefore, in Patent Document 2, the biasing member as described above is omitted, and a configuration is adopted in which the separation claw swings by its own weight and contacts the fixing roller or the pressure roller. Thereby, the contact pressure between the separating claw and the outer circumferential surface of the fixing roller becomes suitable, and damage to the outer circumferential surface as described above can be suppressed.

Some fixing devices as described above are configured to be removably attached to an image forming apparatus.

Japanese Unexamined Patent Publication No. 6-149114 Japanese Patent Application Publication No. 3-105374

A fixing device that is removably attached to an image forming apparatus is sometimes removed from the image forming apparatus and carried around during the assembly stage of the image forming apparatus, maintenance, or parts replacement. At this time, the orientation of the fixing device may be different from the orientation of the fixing device when it is attached to the image forming apparatus. In other words, the separation claw's own weight acts in a direction that separates the separation claw from the outer peripheral surface of the fixing roller or the pressure roller, and the separation claw may separate from the outer peripheral surface. Furthermore, when the orientation of the fixing device returns from this state to the same orientation as when it is attached to the image forming apparatus, the tip of the separation claw comes into contact with the outer circumferential surface again. When the fixing device is removed from the image forming apparatus and carried around, the orientation of the fixing device is not stable, and the tip of the separating claw repeatedly contacts the outer circumferential surface or strongly contacts the outer circumferential surface. This may lead to damage to the outer peripheral surface and wear of the tip of the separation claw.

SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device capable of suppressing damage to the outer circumferential surface of a pressure rotating body or heated rotating body that comes into contact with a separation claw, and an image forming apparatus equipped with the fixing device.

In order to achieve the above object, a first configuration of the present invention is a fixing device including a heated rotating body, a pressurizing rotating body, a heating section, and a separating claw. The pressure rotating body is pressed against the heated rotating body to form a fixing nip. The heating section heats the rotating body to be heated. The separation claw is arranged at a position close to at least one of the rotating body to be heated and the rotating body to be pressurized. Alternatively, the recording medium that has passed through the fixing nip portion is oscillated between the contact position where it contacts the pressure rotating body and the recording medium that has passed through the fixing nip portion from the heated rotating body or the pressure rotating body at the contact position. The fixing device melts and fixes the unfixed toner image on the recording medium by heating and pressurizing the recording medium passing through the fixing nip. The fixing device is removable from the image forming apparatus main body, and when it is attached to the image forming apparatus main body, the separation claw is placed in a contact position by its own weight, and when it is removed from the image forming apparatus main body, the separation claw The separating claw is provided with a biasing member that urges the separating claw toward the contact position against the dead weight of the separating claw when the dead weight of the separating claw acts in the direction of swinging toward the separated position. The separation claw is always placed in the contact position due to its own weight or the biasing force of the biasing member.

According to the first configuration of the present invention, when the fixing device is attached to the image forming apparatus main body, the separating claw is placed in the contact position by its own weight. Therefore, the contact pressure between the separating claw and the outer circumferential surface of the pressure rotating body or the heated rotating body becomes suitable, and damage to the outer circumferential surface is suppressed when the fixing device is attached to the image forming apparatus main body. Can be done. Also, when the fixing device is removed from the image forming apparatus main body and the weight of the separation claw acts in the direction of swinging toward the separation position, the separation claw is arranged at the contact position. Therefore, the separation claw becomes difficult to swing in this state, and it is possible to prevent the separation claw from repeatedly or strongly colliding with the outer circumferential surface. Therefore, it is possible to provide a fixing device that can suppress damage to the outer circumferential surface of the pressurizing rotary body or the heated rotary body and the tip of the separating claw.

A schematic sectional view showing the internal structure of an image forming apparatus 100 in which a fixing device 13 according to an embodiment of the present invention is mounted. Side sectional view of the vicinity of the fixing device 13 in FIG. 1 An enlarged side view of the separation claw 21 and the biasing member 43 viewed from the axial direction of the fixing roller 131 in a state where the separation claw 21 is placed at the contact position P1 due to its own weight. An enlarged side view of the separation claw 21 and the biasing member 43 viewed from the axial direction of the fixing roller 131 in a state where the separation claw 21 is placed at the contact position P1 by the biasing member 43.

Embodiments 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 in which a fixing device 13 according to an embodiment of the present invention is mounted. In the main body of the image forming apparatus 100 (here, a color printer), four image forming sections Pa, Pb, Pc, and Pd are located on the upstream side in the belt conveyance direction (the upstream side in the conveyance direction of the intermediate transfer belt 8 described later, in FIG. 1). They are provided in order from the left side).

The image forming sections Pa to Pd are provided with photoreceptor drums (image carriers) 1a to 1d, charging devices 2a to 2d, an exposure device 5, developing devices 3a to 3d, and cleaning devices 7a to 7d. There is.

The photosensitive drums 1a to 1d are rotatably supported. The photosensitive drums 1a to 1d carry visible images (toner images) of each color. The charging devices 2a to 2c charge the photoreceptor drums 1a to 1d. The exposure device 5 exposes image information to each of the photoreceptor drums 1a to 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. The developing devices 3a to 3d form toner images of each color on the photoreceptor drums 1a to 1d. Toner containers 4a to 4d are arranged above the developing devices 3a to 3d. The toner containers 4a to 4d replenish toner to the developing devices 3a to 3d when the ratio of toner in the two-component developer filled in the developing devices 3a to 3d falls below a specified value.

The cleaning devices 7a to 7d remove developer (toner) and the like remaining on the photoreceptor drums 1a to 1d.

An intermediate transfer belt 8 is provided above and adjacent to the photoreceptor drums 1a to 1d. Intermediate transfer belt 8 rotates counterclockwise in FIG. 1 . As the intermediate transfer belt 8, a belt without seams (seamless belt) is mainly used. The intermediate transfer belt 8 is formed of a dielectric resin sheet.

The intermediate transfer belt 8 is stretched around a driven roller 10 and a drive roller 11. The driven roller 10 is located on the upstream side in the belt conveyance direction. Drive roller 11 is located on the downstream side. A belt drive motor (not shown) is connected to the drive roller 11 for applying rotational driving force to the drive roller 11 . When the drive roller 11 is rotated by the belt drive motor, the intermediate transfer belt 8 rotates following the rotation of the drive roller 11.

A secondary transfer roller 9 is arranged to face the drive roller 11 with the intermediate transfer belt 8 in between. A secondary transfer nip is formed between the intermediate transfer belt 8 and the secondary transfer roller 9. The secondary transfer roller 9 secondary transfers the toner image formed on the intermediate transfer belt 8 to the paper S (recording medium including printing paper, envelopes, and OHP sheets) passing through the secondary transfer nip. .

A belt cleaner 19 is arranged downstream of the drive roller 11 in the belt conveyance direction. The belt cleaner 19 has a blade shape. The belt cleaner 19 removes toner and the like remaining on the surface of the intermediate transfer belt 8.

A fixing device 13 is arranged downstream of the secondary transfer nip with respect to the conveyance direction of the paper S (hereinafter referred to as the "paper conveyance direction"). The fixing device 13 fuses and fixes the toner image secondarily transferred to the sheet S, which has been transported. The detailed configuration of the fixing device 13 will be described later.

The paper S is housed in a paper cassette 16 located at the bottom of the main body of the image forming apparatus 100 . The paper S is conveyed to the secondary transfer nip via the paper feed roller 12a and the registration roller pair 12b.

When image data is input from a host device such as a personal computer, first, the charging devices 2a to 2d uniformly charge the surfaces of the photoreceptor drums 1a to 1d. Next, the exposure device 5 irradiates light according to the image data to form electrostatic latent images on each of the photosensitive drums 1a to 1d according to the image data.

The developing devices 3a to 3d supply toner onto the photoreceptor drums 1a to 1d. Then, the toner electrostatically adheres to the photoreceptor drums 1a to 1d, forming a toner image corresponding to the electrostatic latent image.

Then, an electric field is applied by the primary transfer rollers 6a to 6d between the primary transfer rollers 6a to 6d and the photosensitive drums 1a to 1d at a predetermined transfer voltage. With the toner images formed on the photoreceptor drums 1a to 1d, the intermediate transfer belt 8 moves while contacting each of the photoreceptor drums 1a to 1d, so that the toner images of each color are sequentially formed on the intermediate transfer belt 8. A full color image is formed by primary transfer and superimposition.

Thereafter, the paper S is conveyed from the registration roller pair 12b to the secondary transfer nip portion at a predetermined timing. Then, the full-color image on the intermediate transfer belt 8 is secondarily transferred onto the paper S. The paper S on which the toner image has been secondarily transferred is conveyed to the fixing device 13.

When the sheet S is conveyed to the fixing device 13, the sheet S is heated and pressurized by the fixing device 13, and the toner image on the sheet S is fixed to the sheet S. Thereafter, the paper S is sorted in its conveying direction by a bifurcation section 14 that branches into two directions, and is sent to the duplex conveyance path 18 and images are formed on both sides of the sheet S as it is (or after being sent to the double-sided conveyance path 18 and images are formed on both sides). It is discharged on 17th.

Next, the fixing device 13 will be explained in detail. FIG. 2 is a side sectional view of the vicinity of the fixing device 13 in FIG. 1. The fixing device 13 employs a fixing method using an electromagnetic induction heating type heat source. The fixing device 13 uses a vertical conveyance method (the direction in which the fixing roller 131 and the pressure roller 132 face each other is the horizontal direction, and the paper S passing through the fixing nip N is conveyed in the vertical direction (upward as shown in FIG. 2). 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 shaft body 40, a separating claw 21, and a biasing member 43. We are prepared.

The fixing roller 131 is rotatably held in the housing of the fixing device 13. The fixing roller 131 includes a base material 131a, a heat insulating layer 131b, an induction heating layer 131c, an elastic layer 131d, and a release layer 131e.

The base material 131a is made of stainless steel and has a cylindrical shape. A heat insulating layer 131b and an induction heating layer 131c are laminated on the base material 131a. The elastic layer 131d is laminated on the induction heating layer 131c. The elastic layer 131d is made of silicone rubber sponge for imparting elasticity to the fixing nip portion N that is in pressure contact with the pressure roller 132. The release layer 131e is a layer made of fluororesin and formed into a tube shape so as to cover the surface of the elastic layer 131d.

Pressure roller 132 is provided at a position facing fixing roller 131 . The pressure roller 132 includes a base material 132a, an elastic layer 132b, and a release layer 132c. A release layer 132c, an elastic layer 132b, and a base material 132a are laminated in this order from the outside in the radial direction of the pressure roller 132.

The base material 132a is a metal core made of aluminum. The base material 132a is rotatably supported by the housing of the fixing device 13. The elastic layer 132b is a layer made of silicone rubber formed on the base material 132a. The elastic layer 132b provides elasticity to the fixing nip portion N. The release layer 132c is a tube-shaped layer made of fluororesin and covers the surface of the elastic layer 132b. The release layer 131e and the release layer 132c make it easy to separate the paper S from the fixing roller 131 and the pressure roller 132 when the unfixed toner image is melted and fixed in the fixing nip N.

The pressure roller 132 is rotationally driven by a drive source (not shown) such as a motor, and further pressurized toward the center of the fixing roller 131 in the radial direction. 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 is driven to rotate in the same direction via the fixing nip N.

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 unit 133 is arranged to face and surround a part of the outer periphery of the fixing roller 131 and extends in the axial direction of the fixing roller 131 .

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

When the paper S is inserted into the fixing nip N with the fixing roller 131 heated to a predetermined temperature, the paper S held in the fixing nip N is heated and is pressed by the pressure roller 132. be done. As a result, the powdered toner on the paper S is melted and fixed.

After the toner has been fixed, the sheet S is discharged from the discharge roller pair 15 to the discharge tray 17 (see FIG. 1) via the fixing conveyance roller pair 20.

Next, the separation claw 21 will be explained in detail. FIG. 3 is an enlarged side view of the separation claw 21 and the biasing member 43 viewed from the axial direction of the fixing roller 131 in a state where the separation claw 21 is placed at the contact position P1 due to its own weight. FIG. 4 is an enlarged side view of the separation claw 21 and the biasing member 43 viewed from the axial direction of the fixing roller 131 in a state where the separation claw 21 is placed at the contact position P1 by the biasing member 43.

In FIG. 3, similarly to FIG. 2, the lower side of the fixing nip N in the figure is the upstream side in the paper transport direction, and the upper part of the fixing nip N is the downstream side in the paper transport direction. In FIG. 4, the left side of the fixing nip N is the upstream side in the paper transport direction, and the right side of the fixing nip N is the downstream side in the paper transport direction.

As shown in FIGS. 2 and 3, the shaft body 40 is disposed on the downstream side of the fixing nip portion N with respect to the paper conveyance direction. The shaft body 40 is a rod-shaped body extending parallel to the rotation axis of the fixing roller 131. The shaft body 40 is rotatably supported around a swing axis L1 passing through the center of the shaft body 40 in the radial direction. Hereinafter, the direction parallel to the swing axis L1 will be referred to as the "axial direction."

The separation claw 21 is arranged on the downstream side of the fixing nip portion N with respect to the paper conveyance direction. Furthermore, the separation claw 21 is located 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. The separation claws 21 are made of heat-resistant resin (eg, polyimide, etc.). The surface of the separation claw 21 is coated with fluororesin.

A plurality of separation claws 21 are arranged along the extending direction of the shaft body 40 (direction perpendicular to the paper surface of FIG. 3) (not shown). Each separation claw 21 is fixed to the shaft body 40 at the same position (same phase) in the circumferential direction of the shaft body 40. The separation claw 21 is formed integrally with the shaft body 40.

The separation claw 21 swings between a contact position P1 and a separation position P2 using the shaft body 40 as a swing support shaft. The contact position P1 is a position where the tip of the separation claw 21 (the tip 51 of the contact portion 50 described later) contacts the outer circumferential surface of the fixing roller 131 (the position of the separation claw 21 indicated by a solid line in FIG. 3). The separated position P2 is a position where the tip (tip portion 51) of the separation claw 21 is separated from the outer circumferential surface of the fixing roller 131 (the position of the separation claw 21 indicated by a broken line in FIG. 3).

With the separating claw 21 disposed at the contact position P1, even if the paper S that has passed through the fixing nip N sticks to the outer peripheral surface of the fixing roller 131 due to melted toner, the tip of the separating claw 21 ( By contacting the leading end portion 51), the sheet S is peeled off from the outer peripheral surface of the fixing roller 131 and separated.

The separation claw 21 has an arm portion 41 and a contact portion 50. The arm portion 41 and the contact portion 50 are arranged on both sides with the swing axis L1 therebetween. The contact portion 50 protrudes from the outer peripheral surface of the shaft body 40 toward the fixing roller 131 . The arm portion 41 protrudes from the outer peripheral surface of the shaft in a direction opposite to the contact portion 50.

The arm portion 41 has an engaging protrusion 42 . The engagement protrusion 42 is a protrusion that protrudes in the axial direction from the end of the arm portion 41 on the opposite side to the swing axis L1.

The center of gravity of the separation claw 21 is biased toward the contact portion 50 side with respect to the swing axis L1. Therefore, when the fixing device 13 is attached to the image forming apparatus 100 (the state shown in FIG. 3), the moment due to its own weight acting on the separation claw 21 (hereinafter referred to as "self-weight moment") is It acts in the clockwise direction shown in FIG. 3 along the circumferential direction of L1.

The biasing member 43 has a weight portion 44 and a regulating portion 45. The weight portion 44 has a through hole 46 (guide hole) formed therein. The through hole 46 passes through the weight portion 44 in the axial direction. The through hole 46 has a rectangular cross-sectional shape in a plan view along the axial direction. The through hole 46 has a long side parallel to a direction perpendicular to the radial direction of the swing axis L1 (the tangential direction of a virtual circle centered on the swing axis L1, hereinafter simply referred to as the "tangential direction"). It is a long hole.

The engaging protrusion 42 is inserted into the through hole 46 . A first opposing surface 47 and a second opposing surface 48 are formed on a portion of the inner peripheral surface of the through hole 46 . The first opposing surface 47 and the second opposing surface 48 are planes perpendicular to the tangential direction. The first opposing surface 47 and the second opposing surface 48 face each other in the tangential direction with the engagement protrusion 42 interposed therebetween. When the fixing device 13 is attached to the image forming apparatus 100, the first opposing surface 47 is located below the second opposing surface 48.

A housing (not shown) of the fixing device 13 is provided with a pair of guide ribs 49 . The guide ribs 49 are elongated and protrude in the axial direction and are parallel to the tangential direction. The weight portion 44 faces a pair of guide ribs 49 in a direction perpendicular to the tangential direction. The weight portion 44 can reciprocate in the tangential direction while being slid and guided by the guide ribs 49.

The regulating portion 45 is formed on one end side (the fixing roller 131 side) of the pair of guide ribs 49, and faces the weight portion 44 in the tangential direction. As shown in Figure 3. When the fixing device 13 is attached to the image forming apparatus 100, the regulating section 45 is located below the weight section 44. The regulating portion 45 comes into contact with the weight portion 44 at a predetermined position to regulate movement of the weight portion 44 . With the movement of the weight portion 44 being restricted by the restriction portion 45 and the separation claw 21 being disposed at the contact position P1, the second opposing surface 48 and the engagement protrusion 42 are separated.

As shown in FIG. 3, when the fixing device 13 is attached to the image forming apparatus 100, the weight section 44 moves downward due to its own weight, and its movement is regulated by the regulating section 45. In this state, the weight of the separation claw 21 acts in a direction in which the separation claw 21 swings toward the contact position P1. When the separation claw 21 swings toward the contact position P1 due to its own weight, the engagement protrusion 42 moves upward within the through hole 46. When the separation claw 21 reaches the contact position P1, the swinging of the separation claw 21 is restricted, and the movement of the engagement protrusion 42 is also restricted.

In this state, the engaging protrusion 42 is spaced apart from the first opposing surface 47 and the second opposing surface 48, and no biasing force of the weight portion 44 is exerted on the separating claw 21. That is, in this state, the moment of the biasing force of the weight portion 44 acting on the separation claw 21 around the swing axis L1 (biasing moment due to the biasing force F described later) is 0, and the self weight acting on the separation claw 21 is 0. smaller than the moment. Therefore, the separation claw 21 is positioned at the contact position P1 by its own weight.

When the fixing device 13 is removed from the image forming apparatus 100, the separation claw 21 may be located below the fixing roller 131, as shown in FIG. 4, depending on the orientation of the fixing device 13. In this state, the weight of the separation claw 21 acts in a direction in which the separation claw 21 swings toward the separated position P2.

In this state, the guide rib 49 is inclined downward to the right. Then, the weight portion 44 is subjected to its own downward weight. Then, the weight part 44 slides on the guide rib 49 due to its own weight and moves in the direction away from the regulating part 45 with respect to the tangential direction. Then, the first opposing surface 47 and the engagement protrusion 42 come into contact.

As a result, a component force (hereinafter referred to as "biasing force F") of the weight of the weight portion 44 along the tangential direction acts on the separation claw 21 via the engagement protrusion 42 . Due to the biasing force F, the weight portion 44 biases the separation claw 21 toward the contact position P1 against the weight of the separation claw 21 (indicated by an arrow in the figure). In this state, the biasing force F of the weight portion 44 is greater than the weight of the separation claw 21 itself. That is, the biasing moment in this state is larger than the self-weight moment. Therefore, the separation claw 21 is positioned at the contact position P1 by the urging force F of the urging member 43.

As described above, the separation claw 21 of this embodiment is placed at the contact position P1 by its own weight when the fixing device 13 is attached to the image forming apparatus 100. Therefore, the contact pressure between the separating claw 21 and the outer circumferential surface of the fixing roller 131 becomes suitable, and damage to the outer circumferential surface of the fixing roller 131 can be suppressed when the fixing device 13 is attached to the image forming apparatus 100. can. Also, when the fixing device 13 is removed from the image forming apparatus 100 and the weight of the separation claw 21 acts in a direction to swing toward the separation position P2, the separation claw 21 is arranged at the contact position P1. Therefore, in this state, the separation claw 21 is positioned at the contact position P1, and it is possible to prevent the separation claw 21 from repeatedly colliding with the outer peripheral surface of the fixing roller 131 or strongly colliding with the outer peripheral surface. Therefore, it is possible to provide a fixing device that can suppress damage to the outer peripheral surface of the fixing roller 131 and the separation claw 21.

Further, as described above, the weight portion 44 is movable in the tangential direction due to its own weight. Therefore, without adopting a complicated configuration, when the fixing device 13 is removed from the image forming apparatus 100 and the weight of the separation claw 21 acts in the direction of swinging toward the separation position P2, the separation claw 21 is positioned at the contact position P1 by the weight portion 44. Therefore, it is possible to suppress damage to the outer peripheral surface of the fixing roller 131 and the separation claw 21 while suppressing manufacturing costs.

Furthermore, as described above, by adopting the configuration in which the guide rib 49 slides with the weight part 44, even if the direction of the weight acting on the weight part 44 is not along the tangential direction, the weight part 44 is moved along the tangential direction by the guide rib 49. Move by being guided in a direction. Therefore, it becomes possible to match the direction of the biasing force F in the tangential direction, and it is possible to apply a biasing moment to the separation claw 21 more suitably.

In addition, the present invention is not limited to the above-described embodiments, and various changes can be made without departing from the spirit of the present invention. For example, in the above embodiment, the fixing device 13 of a roller heating type is provided with the fixing roller 131 as a rotating body to be heated. The present invention can be similarly applied to fixing devices equipped with rotating bodies to be heated other than 131. Further, the heating method is not limited to the induction heating method using the induction heating section 133 including an excitation coil and a core, and for example, a halogen heater can also be used as the heating section.

Furthermore, although the fixing device 13 according to the above embodiment adopts a vertical conveyance method, it uses a horizontal conveyance method (the direction in which the fixing roller 131 and the pressure roller 132 face each other is the vertical direction, and the fixing device 13 passes through the fixing nip portion N). A method in which the paper S is transported in the lateral direction (horizontal direction) can be adopted.

Further, although the separation claw 21 according to the fixing device 13 of the above embodiment is arranged at the contact position P1, the tip portion 51 contacts the outer circumferential surface of the fixing roller 131, but the present invention is not limited to this. . For example, the separation claw 21 may have its tip portion 51 contacting the outer circumferential surface of the pressure roller 132 while being disposed at the contact position P1. For example, when double-sided printing is performed, a heated toner image is formed on the surface of the paper S on the pressure roller 132 side immediately after fixing. Therefore, by arranging the separation claw 21 in a position close to the pressure roller 132, it is possible to separate the paper S from the pressure roller 132 while suppressing damage to the outer peripheral surface of the pressure roller 132. become.

Similarly, it is also possible to adopt a configuration in which the separation claw 21 that contacts the fixing roller 131 and the separation claw 21 that contacts the pressure roller 132 are provided separately.

The present invention relates to a fixing device that melts and fixes a toner image onto a recording medium by inserting a recording medium into a fixing nip formed by a heated rotating body and a pressure rotating body and applying heat and pressure to the toner image. Available. By utilizing the present invention, it is possible to provide a fixing device that can suppress damage to the outer circumferential surface of a pressure rotating body or heated rotating body that comes into contact with a separation claw, and an image forming apparatus equipped with the fixing device.

13 Fixing device 21 Separation claw 41 Arm portion 43 Biasing member 44 Weight portion 45 Regulating portion 51 Tip portion 100 Image forming device 131 Fixing roller (rotating body to be heated)
132 Pressure roller (pressure rotating body)
L Swing axis N Fixing nip section P1 Contact position P2 Separation position Pa to Pd Image forming section S Paper (recording medium)

Claims (7)

A rotating body to be heated;
a pressure rotating body that is pressed against the heated rotating body to form a fixing nip;
a heating unit that heats the rotating body to be heated;
a spaced-apart position in which the distal end is located close to at least one of the heated rotating body and the pressurized rotating body, and the distal end is separated from the heated rotating body and the pressurized rotating body; The recording medium is oscillated between a rotating body or a contact position in contact with the pressure rotating body, and passes through the fixing nip portion from the heated rotating body or the pressure rotating body while in the contact position. A separation claw that separates the
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 fixing device is removable from the image forming apparatus main body,
When the fixing device is attached to the image forming apparatus main body, the separating claw is placed in the contact position by its own weight,
When the fixing device is removed from the image forming apparatus main body and the weight of the separation claw acts in the direction of swinging toward the separated position, the separation claw is moved against the weight of the separation claw. It includes a biasing member that biases toward the contact position,
The fixing device is characterized in that the separating claw is always placed at the contact position by its own weight or by the urging force of the urging member. The biasing moment of the biasing force acting on the separation claw around the swing axis of the separation claw is:
smaller than a self-weight moment of the separation claw's own weight acting on the separation claw around the swing axis when the separation claw swings toward the contact position due to its own weight;
The fixing device according to claim 1, wherein when the separation claw swings toward the separated position due to its own weight, the moment is larger than the self-weight moment. The separating claw has an arm portion that protrudes to the opposite side of the tip portion across the swing shaft,
The biasing member is
a weight part disposed on the arm part side of the separating claw and supported so as to be reciprocally movable in a direction intersecting the swing axis;
a regulating part provided to face the weight part in the orthogonal direction;
has
The weight part is
When the separation claw swings toward the separated position due to its own weight, it moves due to its own weight so as to be separated from the regulating portion along the intersecting direction, contacts the arm portion, and moves the separation claw to the above-mentioned position. bias toward the contact position,
When the separating claw swings toward the contact position due to its own weight, it moves due to its own weight so as to approach the regulating portion along the orthogonal direction, comes into contact with the regulating portion, and is prevented from contacting the arm portion. The fixing device according to claim 1, wherein the fixing device is regulated. The weight portion has a guide hole that slidably engages with the arm portion,
When the weight part moves due to its own weight so as to be separated from the regulating part, the weight part of the weight part acts on the arm part due to the arm part coming into contact with an end of the guide hole,
The fixing device according to claim 3, wherein when the weight portion contacts the regulating portion, the arm portion is separated from an end of the guide hole so that the weight of the weight portion does not act on the arm portion. Device. The separation claw is
the swing axis extending parallel to the rotation axis of the pressurizing rotor;
a plurality of the tip portions arranged along the axial direction of the swing shaft, protruding from the outer circumferential surface of the swing shaft toward the heated rotating body or the pressurizing rotating body;
The fixing device according to any one of claims 1 to 4, characterized in that the fixing device has: comprising a guide rib extending along a tangential direction of a virtual circle centered on the swing axis,
5. The fixing device according to claim 1, wherein the weight portion moves back and forth along the guide rib. The fixing device according to claim 1, which fixes the toner image on the recording medium to the recording medium;
an image forming unit that is disposed upstream of the fixing nip with respect to the conveyance direction of the recording medium and forms the toner image on the recording medium;
An image forming apparatus comprising:

Images