JP6876473B2 - Fixing device - Google Patents

Description

Embodiments of the present invention relate to a fixing device.

The fixing device includes a heating roller and a pressing unit. The pressing unit has a pressure belt and a pressure roller. The pressing unit heat-fixes the toner to the sheet by pressing a recording medium such as a sheet against the heating roller. The fixing device may weaken the pressing by the pressing unit in order to prevent the recording medium from wrinkling.
In the fixing device, when the pressing force by the pressing unit is weakened, the pressurizing belt may not move according to the heating roller, and it may be difficult to convey the recording medium.

Japanese Unexamined Patent Publication No. 2014-119600

An object to be solved by the present invention is to provide a fixing device that does not easily hinder the transport of a recording medium even when the pressing force by the pressing unit is weakened.

The fixing device of the embodiment includes a first rotating body, a pressing unit, an urging member, and a moving mechanism . The first rotating body is heated by a heat source. The pressing unit includes a belt, a second rotating body, a belt supporting member, and a pressing member. The belt faces the outer peripheral surface of the first rotating body. In the second rotating body, the belt is hung around the outer peripheral surface. In the belt support member, the belt is hung around the outer peripheral surface. The pressing member has a pressing region that presses the belt toward the first rotating body. The pressing member is arranged between the second rotating body and the belt supporting member. The pressing unit can switch between a pressing position and a releasing position by rotating around a rotation fulcrum. The rotation fulcrum is located at a position away from the first rotating body. At the pressing position, the pressing unit presses the belt against the first rotating body by the second rotating body. At the release position, the pressing unit is released from being pressed by the second rotating body. The line connects the center of the first rotating body and the center of the rotating fulcrum when viewed from the axial direction of the first rotating body. The line passes through the pressing region of the pressing member at both the pressing position and the releasing position. The urging member urges the pressing unit in a first direction in which the second rotating body approaches the first rotating body. The moving mechanism has a first rotating body holding member and a separating arm. The first rotating body holding member is attached to the first rotating body. The separation arm is rotatably supported by the pressing unit and can come into contact with the outer peripheral surface of the first rotating body holding member at a contact portion. In the moving mechanism, the separation arm is rotated in the direction of pressing the first rotating body holding member, so that the pressing unit is set in the second direction opposite to the first direction with the contact point as a fulcrum. Move in the direction.

The external view which shows the image forming apparatus using the fixing apparatus of embodiment. The figure which shows the schematic structure of the image forming apparatus using the fixing apparatus of embodiment. The figure which shows the schematic structure of the fixing device of an embodiment. The figure which shows the schematic structure of the fixing device of an embodiment. The perspective view which shows the fixing device of an embodiment. The front view which shows the fixing device of an embodiment. The front view which shows the fixing device of an embodiment. The perspective view which shows a part of the fixing device of an embodiment. The perspective view which shows a part of the fixing device of an embodiment.

Hereinafter, the fixing device of the embodiment will be described with reference to the drawings.

FIG. 1 is an external view showing an overall configuration example of an image forming apparatus 200 using the fixing apparatus of the embodiment. For example, the image forming apparatus 200 is a multifunction device. The image forming apparatus 200 includes a display 210, a control panel 220, a printer unit 230, a sheet accommodating unit 240, and an image reading unit 300.

The image forming apparatus 200 forms an image on a recording medium such as a sheet by using a developing agent such as toner. For example, the sheet is paper or label paper. The sheet is not particularly limited as long as the image forming apparatus 200 can form an image on the surface thereof. The recording medium is not limited to a single sheet, and may have a structure in which a plurality of sheets are overlapped and at least a part thereof is adhered and fixed to each other, such as an envelope. A recording medium (envelope or the like) having a structure in which a plurality of sheets are laminated and at least a part thereof is adhered and fixed to each other is called a "laminated recording medium".

The display 210 is an image display device such as a liquid crystal display or an organic EL (Electro Luminescence) display. The display 210 displays various information about the image forming apparatus 200.
The control panel 220 has a plurality of buttons. The control panel 220 accepts user operations. The control panel 220 outputs a signal corresponding to the operation performed by the user to the control unit of the image forming apparatus 200. The display 210 and the control panel 220 may be configured as an integrated touch panel.

The printer unit 230 forms an image on the sheet based on the image information generated by the image reading unit 300 or the image information received via the communication path. For example, the printer unit 230 forms an image by the following processing. The image forming unit of the printer unit 230 forms an electrostatic latent image on the photoconductor drum based on the image information. The image forming unit of the printer unit 230 forms a visible image by adhering a developer to the electrostatic latent image. Toner is a specific example of a developer. The transfer unit of the printer unit 230 transfers the visible image onto the sheet. The fixing section of the printer section 230 fixes the visible image on the sheet by heating and pressurizing the sheet. The sheet on which the image is formed may be a sheet housed in the seat accommodating portion 240 or a hand-pointed sheet.
The sheet accommodating unit 240 accommodates a sheet used for image formation in the printer unit 230.

The image reading unit 300 reads the image information to be read as light and dark. The image reading unit 300 records the read image information. The recorded image information may be transmitted to another information processing device via a network. The recorded image information may be image-formed on the sheet by the printer unit 230.

FIG. 2 is a diagram showing an example of a schematic configuration of the image forming apparatus 200 of the embodiment. The image forming apparatus 200 shown in FIG. 2 is an electrophotographic image forming apparatus. The image forming apparatus 200 includes an intermediate transfer body 10, a blade 11 (toner removing unit), an image forming unit 12 to 15, a secondary transfer roller 16, a control unit 17, a paper feeding unit 18, and a fixing device 20.
The intermediate transfer body 10 is an endless belt and rotates in the direction of the arrow shown in FIG.
The blade 11 removes excess toner adhering to the intermediate transfer body 10.
The image forming units 12 to 15 form an image on the intermediate transfer body 10 using toners of each color (four colors in the example shown in FIG. 2).
The secondary transfer roller 16 transfers the image of the toner formed on the intermediate transfer body 10 onto the sheet.
The control unit 17 controls the image forming units 12 to 15 and the fixing device 20.
The paper feed unit 18 feeds the sheet.
The fixing device 20 heats and pressurizes the image of the toner transferred onto the sheet to fix it on the sheet.

The image forming apparatus 200 converts the formed image data into image data of each color by image processing. For example, the image forming apparatus 200 converts the image data into image data of each color of yellow (Y), magenta (M), cyan (C), and black (K).
The image forming apparatus 200 executes the first transfer step and the second transfer step. In the first transfer step, the image forming units 12 to 15 perform multiple transfer so as to superimpose the images of the toners of each color on the intermediate transfer body 10. In the second transfer step, the secondary transfer roller 16 collectively transfers the image of the toner on the intermediate transfer body 10 onto the sheet. The sheet is fed from the paper feed unit 18 and conveyed along the paper transport path. The sheet passes through the secondary transfer roller 16 and the fixing device 20, and is discharged to the output tray.

3 and 4 are diagrams showing a schematic configuration of the fixing device 20 shown in FIG.
As shown in FIG. 3, the fixing device 20 includes a heat roller 21 (first rotating body), a pressing unit 22, and an urging member 23.
The heat roller 21 is a cylinder made of a metal such as aluminum or iron. The outer peripheral surface of the heat roller 21 is covered with a release layer (coating layer). For example, the release layer is made of an elastic material such as fluororesin or silicone rubber. The heat roller 21 has a built-in lamp 24 (heat source). The heat roller 21 is heated by the lamp 24. For example, the lamp 24 is a halogen lamp, an IH heater, or the like.

The pressing unit 22 includes a pressure belt 25 (belt), a pressure roller 26 (second rotating body), a pressure pad 27 (pressing member), and a pressure belt heat roller 28 (belt support member). , Equipped with.
The pressure belt 25 is an endless belt. The pressure belt 25 is laid around the outer peripheral surface of the pressure roller 26 and the outer peripheral surface of the pressure belt heat roller 28. The pressure belt 25 rotates in accordance with the heat roller 21. The pressure belt 25 faces the outer peripheral surface 21a of the heat roller 21. The pressure belt 25 is brought into pressure contact with the heat roller 21 by the pressure roller 26 and the pressure pad 27. By this pressure contact, a fixing nip portion is formed between the pressure belt 25 and the heat roller 21.

The pressure roller 26 is a cylinder made of a metal such as stainless steel. For example, a coating layer is formed on the outer peripheral surface of the pressure roller 26. The coating layer is made of an elastic material such as fluororesin or silicone rubber. The pressure roller 26 presses the pressure belt 25 toward the heat roller 21. The central axis C2 of the pressure roller 26 is parallel to the central axis C1 of the heat roller 21. The pressure roller 26 brings the pressure belt 25 into pressure contact with the heat roller 21. The pressure roller 26 forms an outlet for the anchoring nip.

The pressure pad 27 is upstream of the pressure roller 26 in the sheet transport direction and downstream of the pressure belt heat roller 28 in the sheet transport direction. Therefore, the pressure pad 27 is arranged between the pressure roller 26 and the pressure belt heat roller 28 in the sheet transport direction. The pressure pad 27 includes a pedestal 31, a pad body 32, and a pressure mechanism 29. The pad body 32 is made of a soft material such as silicone rubber. The pad body 32 is provided on one surface of the pedestal 31. The pressure pad 27 presses the pressure belt 25 by the pad body 32. A sliding sheet for reducing friction may be provided between the pressure pad 27 and the pressure belt 25. The pressurizing mechanism 29 urges the pressurizing pad 27 toward the heat roller 21. For example, the pressurizing mechanism 29 is a coil spring.

The pressure pad 27 has a pressing region 30. The pressing region 30 is a partial region of the pad body 32. For example, the pressing region 30 is a cylindrical surface along the outer peripheral surface 21a of the heat roller 21. The pressing region 30 faces the outer peripheral surface 21a of the heat roller 21 via the pressure belt 25. The pressing region 30 comes into contact with the outer peripheral surface 21a of the heat roller 21 via the pressure belt 25. The pressing region 30 presses the pressure belt 25 toward the outer peripheral surface 21a of the heat roller 21.

The pressure belt heat roller 28 is a tubular body made of a metal such as aluminum or iron. The outer peripheral surface of the pressure belt heat roller 28 is covered with a release layer (coating layer). The release layer is made of an elastic material such as fluororesin or silicone rubber. The pressure belt heat roller 28 has a built-in lamp 33 (heat source). The pressure belt heat roller 28 is heated by the lamp 33. For example, the lamp 33 is a halogen lamp, an IH heater, or the like. The pressure belt heat roller 28 heats the pressure belt 25. The central axis C3 of the pressure belt heat roller 28 is parallel to the central axis C1 of the heat roller 21. The pressure belt heat roller 28 is arranged upstream of the pressure pad 27 in the sheet transport direction.
The pressure belt heat roller 28 may be movable in the direction of approaching and separating from the pressure roller 26. Thereby, the tension of the pressure belt 25 can be easily adjusted.

The pressing unit 22 can rotate about the rotation fulcrum 35. The rotation fulcrum 35 is located away from the heat roller 21. The central axis C4 of the rotation fulcrum 35 is parallel to the central axis C1 of the heat roller 21.
The first direction D1 is one direction in the axial direction of the rotation fulcrum 35. The first direction D1 is a direction in which the pressure roller 26 approaches the heat roller 21. The second direction D2 is the direction opposite to the first direction D1 in the axial direction of the rotation fulcrum 35. The second direction D2 is a direction in which the pressure roller 26 is separated from the heat roller 21.

The pressing unit 22 can switch between the pressing position P1 shown in FIG. 3 and the releasing position P2 shown in FIG. 4 by rotating around the rotation fulcrum 35. The pressing position P1 is a position where the pressure belt 25 is pressed against the heat roller 21 by the pressure roller 26. The release position P2 is a position where the pressing by the pressure roller 26 is released. At the release position P2, the pressure roller 26 may be in contact with the heat roller 21 via the pressure belt 25, or may be separated from the heat roller 21.

The urging member 23 urges the pressing unit 22 in the first direction D1. For example, the urging member 23 is a coil spring. The urging member 23 urges the pressure roller 26 in the first direction D1.

The virtual line L1 is a line connecting the central axis C1 of the heat roller 21 and the central axis C4 of the rotation fulcrum 35 when viewed from a direction parallel to the central axis C1 of the heat roller 21.
The virtual line L1 passes through the pressing region 30 of the pressure pad 27 when the pressing unit 22 is at the pressing position P1 shown in FIG. 3 when viewed from a direction parallel to the central axis C1 of the heat roller 21. The virtual line L1 passes through the pressing region 30 of the pressure pad 27 even when the pressing unit 22 is at the release position P2 shown in FIG. 4 when viewed from a direction parallel to the central axis C1 of the heat roller 21.

The virtual line L1 may pass through a part of the pressing area 30 at the pressing position P1 and the releasing position P2, and the position passing through the pressing area 30 is not particularly limited. For example, the position where the virtual line L1 passes through the pressing region 30 may be the center in the sheet transport direction or the end portion in the sheet transport direction.
The virtual line L1 intersects the pressing region 30 when viewed from a direction parallel to the central axis C1 of the heat roller 21. It can be said that the pressing region 30 is located at a position straddling the virtual line L1. Seen from a direction parallel to the central axis C1 of the heat roller 21, the central axis C4 is within the projection range from the central axis C1 toward the pressing region 30.

As shown in FIG. 3, the fixing device 20 passes a sheet on which an image (unfixed developer image) of unfixed toner is transferred in the direction of the arrow in the drawing. The sheet and the toner image on the sheet are heated and pressurized through the nip between the heat roller 21 and the pressure belt 25. The sheet passing through the nip is heated from the heat roller 21 and the pressure belt 25. The toner image is fixed on the sheet.

In the fixing device 20, a virtual line connecting the center of the heat roller 21 and the center of the rotation fulcrum 35 regardless of whether the pressing unit 22 is at the pressing position P1 (see FIG. 3) or the releasing position P2 (see FIG. 4). L1 passes through the pressing region 30 of the pressing pad 27. Therefore, the displacement of the pressure pad 27 (change in the distance between the heat roller 21 and the pressure pad 27) between the pressing position P1 and the release position P2 becomes small. Therefore, even when the pressing unit 22 is in the release position P2, the pressing force of the pressurizing pad 27 against the heat roller 21 is not significantly reduced as compared with the case where the pressing unit 22 is in the pressing position P1.

Unlike plain paper (single sheet), when targeting a laminated recording medium (envelope, etc.), if the pressing unit 22 is at the pressing position P1 (see FIG. 3), the laminated recording is performed by bending. Wrinkles are likely to occur on the medium. Therefore, the pressing unit 22 is set to the release position P2 (see FIG. 4). As a result, the pressing force of the pressurizing roller 26 is reduced and the bending of the laminated recording medium is reduced, so that the occurrence of wrinkles is suppressed. In this case, the recording medium is mainly pressed by the pressure pad 27 regardless of the pressure roller 26. Therefore, the transport speed of the laminated recording medium is reduced. As a result, the toner is fixed on the laminated recording medium.

According to the fixing device 20, the pressing pressure of the pressurizing pad 27 does not decrease even when the pressing unit 22 is in the release position P2, so that the pressurizing belt 25 rotates in accordance with the heat roller 21. Therefore, there is no problem in transporting a recording medium (laminated recording medium) such as a sheet.

Next, the fixing device 120, which is a specific example of the fixing device 20, will be described with reference to FIGS. 5 to 9.
FIG. 5 is a perspective view showing the fixing device of the embodiment. FIG. 6 is a front view showing the fixing device of the embodiment. FIG. 7 is a front view showing the fixing device of the embodiment. FIG. 8 is a perspective view showing a part of the fixing device of the embodiment. FIG. 9 is a perspective view showing a part of the fixing device of the embodiment.
As shown in FIG. 6, the line connecting the central axis C1 of the heat roller 121 and the central axis C4 of the rotation fulcrum 135 is defined as L1. The direction from the first rotation fulcrum 135 toward the heat roller 121 along the virtual line L1 is called the front F, and the opposite direction is called the rear B.

As shown in FIG. 5, the fixing device 120 includes a heat roller 121 (first rotating body), a pressing unit 122, an urging member 123, a moving mechanism 141 (see FIG. 6), and a detection mechanism 142 (FIG. 6). 8) and a stop mechanism 143 (see FIG. 8).

The heat roller 121 has the same configuration as the heat roller 21 shown in FIG.
The pressing unit 122 includes a pressure belt 125, a pressure roller 126 (second rotating body), a pressure pad 127 (pressing member) (see FIG. 6), and a pressure belt heat roller 128 (belt support member). ), A pair of support frames 151, and a connector 156 (see FIG. 6).
The pressure belt 125 has the same configuration as the pressure belt 25 shown in FIG. The pressure belt 125 faces the outer peripheral surface 121a of the heat roller 121.
The pressure roller 126 has the same configuration as the pressure roller 26 shown in FIG.
The pressure pad 127 has the same configuration as the pressure pad 27 shown in FIG. Reference numeral 130 denotes a pressing region of the pressure pad 127. The pressing region 130 faces the heat roller 121 via the pressurizing belt 125. The pressing region 130 presses the pressure belt 125 toward the heat roller 121.
The pressure belt heat roller 128 has the same configuration as the pressure belt heat roller 28 shown in FIG.

The support frame 151 includes a main body portion 152 and a pressure arm 153.
The main body 152 includes an upper frame 157 and a lower frame 158. The upper frame 157 and the lower frame 158 are connected to each other. For example, the upper frame 157 supports a pressure roller 126 and a pressure pad 127. For example, the lower frame 158 supports the pressure belt heat roller 128. As a result, the pair of support frames 151 support both ends of the pressure roller 126 and both ends of the pressure belt heat roller 128.

The portion of the main body 152 that supports the pressure roller 126 and the pressure belt heat roller 128 is referred to as the main portion 152A.
The pressurizing arm 153 extends substantially toward the front F from the main portion 152A. One end portion 123a of the urging member 123 is connected to the tip end portion 154 of the pressure arm 153.
The connector 156 is bridged between the pair of support frames 151. The connector 156 connects the pair of support frames 151 to each other.

As shown in FIG. 6, the pressing unit 122 can rotate about the first rotation fulcrum 135 provided in the main body portion 152 of the support frame 151. The first rotation fulcrum 135 is located at a position away from the heat roller 121.
The first direction D1 is the direction in which the pressurizing roller 126 approaches the heat roller 121 in the axial direction of the first rotation fulcrum 135. The second direction D2 is the axial direction of the first rotation fulcrum 135, and the second direction D2 is the direction in which the pressurizing roller 126 is separated from the heat roller 121.

The pressing unit 122 can switch between the pressing position P1 shown in FIG. 6 and the release position P2 shown in FIG. 7 by rotating around the first rotation fulcrum 135.
The pressing position P1 shown in FIG. 6 is a position where the pressure belt 125 is pressed against the heat roller 121 by the pressure roller 126.
The release position P2 shown in FIG. 7 is a position where the pressing by the pressure roller 126 is released.

L1 shown in FIGS. 6 and 7 is a virtual line connecting the central axis C1 of the heat roller 121 and the central axis C4 of the first rotation fulcrum 135 when viewed from a direction parallel to the central axis C1 of the heat roller 121. is there.
The virtual line L1 passes through the pressing region 130 of the pressure pad 27 when the pressing unit 122 is at the pressing position P1 shown in FIG. 6 when viewed from a direction parallel to the central axis C1 of the heat roller 121. The virtual line L1 passes through the pressing region 130 of the pressurizing pad 127 even when the pressing unit 122 is at the release position P2 shown in FIG. 7 when viewed from a direction parallel to the central axis C1 of the heat roller 21.

The urging member 123 urges the pressing unit 122 in the first direction D1. For example, the urging member 123 is a coil spring. One end 123a of the urging member 123 is connected to the tip 154 of the pressure arm 153, and the other end 123b is fixed to a fixed point (not shown).
The moving mechanism 141 includes a roller holding member 145 (first rotating body holding member) and a separation arm 146.

The roller holding member 145 is an annular ball bearing. The annular ball bearing has an inner ring (not shown) and an outer ring 148. The roller holding member 145 is provided on the outer periphery of the end portion of the heat roller 121. The roller holding member 145 is rotatable together with the heat roller 121.
The outer peripheral surface 148a of the outer ring 148 is a circumferential surface whose central axis coincides with the central axis C1 of the heat roller 121. The outer peripheral surface 148a of the outer ring 148 is smoothly formed by being polished. The outer peripheral surface 148a has been heat-treated and has high hardness, so that it is not easily worn.

The separation arm 146 is formed in a long plate shape. The thickness direction of the separation arm 146 is parallel to the central axis C1 of the heat roller 121.
A contact convex portion 149 (contact portion) (see FIG. 6) projecting laterally (in the width direction of the separation arm 146) is formed on a part of the side edge of the separation arm 146. The contact convex portion 149 can come into contact with the outer peripheral surface 148a of the roller holding member 145.
The separation arm 146 is supported by a second rotation fulcrum 155 provided on the support frame 151. The second rotation fulcrum 155 is located near one end portion 146a of the separation arm 146. The central axis C5 of the second rotation fulcrum 155 is parallel to the central axis C1 of the heat roller 121. The separation arm 146 is rotatable around the central axis C5 of the second rotation fulcrum 155 with respect to the support frame 151. The distance of the separation arm 146 from the second rotation fulcrum 155 to the other end portion 146b is sufficiently longer than the distance from the second rotation fulcrum 155 to the contact convex portion 149.

As shown in FIGS. 8 and 9, the detection mechanism 142 detects that the pressing unit 122 is in the release position P2.
The detection mechanism 142 includes a detection sensor 160, a light-shielding plate 163, and a control unit 164. The detection sensor 160 is an optical sensor including a light source 161 and a light receiving unit 162. For example, the light source 161 is a laser light source. For example, the light receiving unit 162 is a photodiode. The light source 161 and the light receiving unit 162 are attached to a fixed frame (not shown). The light source 161 and the light receiving unit 162 are provided side by side in the direction along the central axis C1 of the heat roller 121 and at intervals from each other.

The light receiving unit 162 outputs a detection signal when the light from the light source 161 is not received. The light receiving unit 162 may output a detection signal when receiving light from the light source 161.
The light-shielding plate 163 is attached to the main body portion 152 (upper frame 157) or the pressure arm 153 via the connecting plate 165.
The light-shielding plate 163 is in a position that does not block the light from the light source 161 toward the light receiving portion 162 when the pressing unit 122 is at the pressing position P1 shown in FIG. The light-shielding plate 163 is in a position of blocking light from the light source 161 toward the light-receiving unit 162 when the pressing unit 122 is at the release position P2 shown in FIG.

When the pressing unit 122 shifts from the pressing position P1 to the releasing position P2, the light from the light source 161 toward the light receiving unit 162 is blocked by the light shielding plate 163, so that the light receiving unit 162 outputs a detection signal.

In the detection mechanism 142, the control unit 164 outputs a control signal based on the detection signal from the light receiving unit 162, and the display 210 (see FIG. 1) may indicate that the pressing unit 122 is in the release position P2. it can. As a result, the user can recognize that the pressing unit 122 is in the release position P2.

The stop mechanism 143 includes a control unit 166 to which a detection signal from the light receiving unit 162 is input. The control unit 166 can output a control signal based on the detection signal and stop a part of the operation of the image forming apparatus 200. For example, the control signal from the control unit 166 is a signal for stopping the feeding of plain paper (single sheet). By the control signal, the paper feeding unit 18 shown in FIG. 2 can stop the feeding of plain paper (single sheet). On the other hand, the paper feed unit for supplying the laminated recording medium (envelope or the like) is operable.
According to this configuration, when the pressing unit 122 is in the release position P2, the laminated recording medium (envelope or the like) is supplied, but the plain paper (single sheet) is not supplied. Therefore, it is possible to avoid insufficient toner fixing on the pressing unit 122 at the release position P2 due to the supply of plain paper (single sheet).

The stop mechanism 143 may output a control signal for stopping the supply of the laminated recording medium (envelope or the like) when the pressing unit 122 is at the pressing position P1. In this case, the plain paper (single sheet) can be supplied by the paper feed unit 18 shown in FIG. 2, but the paper feed unit for supplying the laminated recording medium (envelope or the like) is stopped. As a result, when the pressing unit 122 is at the pressing position P1, plain paper (single sheet) is supplied, but a laminated recording medium (envelope or the like) is not supplied.
A phototube may be used as the light source of the detection sensor of the release detection mechanism. Further, a mechanical switch may be used instead of the optical sensor.

Next, the operation of the fixing device 120 will be described.
In the state shown in FIG. 6, the pressing unit 122 is at the pressing position P1, and the contact convex portion 149 (contact portion) of the separation arm 146 is in contact with the outer peripheral surface 148a of the roller holding member 145.
As shown in FIG. 7, the other end portion 146b (operating portion) of the separation arm 146 is rotated in the direction of pressing the roller holding member 145 (clockwise in FIG. 7). The separation arm 146 applies a force in the direction away from the roller holding member 145 to the second rotation fulcrum 155 with the contact convex portion 149 as a fulcrum. Therefore, the pressing unit 122 rotates in the second direction D2 against the urging force of the urging member 123, and shifts to the release position P2.

The distance arm 146 has a longer distance from the second rotation fulcrum 155 to the other end 146b than the distance from the second rotation fulcrum 155 to the contact convex portion 149. A large force can be applied to the pressing unit 122 with a moderate pressing force. Therefore, the pressing unit 122 can be operated with a simple operation.

The contact convex portion 149 of the separation arm 146 slides with respect to the outer peripheral surface 148a of the roller holding member 145. As described above, the outer peripheral surface 148a is smooth, has high hardness, and is not easily worn, so that the friction between the contact convex portion 149 and the outer peripheral surface 148a is small. Therefore, the resistance when the separation arm 146 slides on the outer peripheral surface 148a can be reduced. Therefore, the force required to rotate the separation arm 146 can be reduced. Further, since the outer peripheral surface 148a is a cylindrical surface whose central axis coincides with the central axis C1 of the heat roller 121, the friction between the contact convex portion 149 and the outer peripheral surface 148a is reduced. Therefore, the pressing unit 122 can be moved from the pressing position P1 to the releasing position P2 with a simple operation.

When the separation arm 146 is rotated in the direction away from the roller holding member 145, the pressing unit 122 returns to the pressing position P1 shown in FIG. 6 by the urging force of the urging member 123.
In the fixing device 120, the center of the heat roller 121 and the center of the first rotation fulcrum 135 are connected regardless of whether the pressing unit 122 is in the pressing position P1 (see FIG. 6) or the releasing position P2 (see FIG. 7). The virtual line L1 passes through the pressing region 130 of the pressing pad 127. Therefore, the displacement of the pressure pad 127 (change in the distance between the heat roller 21 and the pressure pad 27) between the pressing position P1 and the release position P2 can be reduced. Therefore, even when the pressing unit 122 is in the release position P2, the pressing force of the pressurizing pad 127 against the heat roller 121 does not decrease significantly.

When the laminated recording medium (envelope or the like) is targeted, if the pressing unit 122 is at the pressing position P1 (see FIG. 6), the recording medium is likely to be wrinkled due to bending. Therefore, the pressing unit 122 is set to the release position P2 (see FIG. 7). In that case, the pressing force of the pressurizing roller 126 becomes low and the bending of the recording medium becomes small, so that the occurrence of wrinkles is suppressed.

According to the fixing device 120, the pressing pressure of the pressurizing pad 127 does not decrease even when the pressing unit 122 is in the release position P2, so that the pressurizing belt 125 rotates in accordance with the heat roller 121. Therefore, there is no problem in transporting a recording medium (laminated recording medium) such as a sheet.

Since the fixing device 120 has the moving mechanism 141, the pressing unit 122 can be easily moved from the pressing position P1 to the releasing position P2 as described above.
Since the roller holding member 145 is a ball bearing, the resistance when the separation arm 146 slides on the outer peripheral surface 148a of the roller holding member 145 can be reduced.
Since the outer peripheral surface 148a of the roller holding member 145 is a cylindrical surface whose central axis coincides with the central axis C1 of the heat roller 121, the resistance when the separation arm 146 slides can be reduced.

Since the fixing device 120 includes the detection mechanism 142, the user can recognize that the pressing unit 122 is in the release position P2. Therefore, it is possible to prevent the plain paper (single sheet) from being accidentally supplied to the pressing unit 122 at the release position P2. Therefore, problems such as dirt adhesion in the device due to the sheet with insufficient toner fixing are unlikely to occur.

Since the fixing device 120 includes the stop mechanism 143, a part of the operation of the image forming device 200 can be stopped when the pressing unit 122 is in the release position P2. For example, the paper feed unit 18 (see FIG. 2) can stop the paper feed of plain paper (single sheet). Therefore, it is possible to prevent the above-mentioned problem of insufficient toner fixing.
Since the detection sensor 160 is an optical type, malfunctions are less likely to occur as compared with sensors of other types. Therefore, it is possible to accurately detect that the pressing unit 122 has reached the release position P2.

If the urging member 123 is a coil spring, its elasticity can exert a sufficient force on the pressure arm 153. Therefore, the operating performance of the pressing unit 122 can be improved.

As shown in FIGS. 6 and 7, the lower frame 158 of the support frame 151 may be rotatable with respect to the upper frame 157 at the third rotation fulcrum 170. The central axis C6 of the third rotation fulcrum 170 is parallel to the central axis C1 of the heat roller 121.

In this configuration, the pressure belt heat roller 128 can move in the direction of approaching and separating from the pressure roller 126 by the rotation of the lower frame 158 about the third rotation fulcrum 170. Thereby, the tension of the pressure belt 125 can be easily adjusted.

In the fixing device 20 of the embodiment, the separation arm 146 may be configured as follows. In FIG. 7, an imaginary line connecting the central axis C5 of the second rotation fulcrum 155 and the central axis C1 of the heat roller 121 is assumed. The separation arm 146 may be formed so that the contact convex portion 149 is located in front of the imaginary line when it is largely rotated clockwise in FIG. 7. As a result, the urging force of the urging member 123 acts to maintain the rotational posture of the separation arm 146, so that even if the user releases the pressure on the separation arm 146, the separation arm 146 retains that posture. Will be maintained. Therefore, even if the user releases his / her hand from the separation arm 146, the release position P2 of the pressing unit 122 can be maintained.
The fixing device of the embodiment may be provided with a tension roller in addition to the pressure roller, the pressure pad, and the pressure belt heat roller.

In the fixing device 120, the separation arm 146 is manually operated, but the fixing device of the embodiment may include a mechanism for rotating the separation arm. In that case, the control panel 220 can be configured to be able to input whether the recording medium to be handled is plain paper (single sheet) or a laminated recording medium. In the fixing device having this configuration, the separation arm is operated by the mechanism based on the input content, and the pressing unit is set to either the pressing position or the releasing position.
In the embodiment, the pressure belt heat roller is adopted as the belt support member, but the belt support member is not limited to the roller and may be a non-rotating body.

According to at least one embodiment described above, the center of the heat roller 21 and the rotation fulcrum 35 regardless of whether the pressing unit 22 is in the pressing position P1 (see FIG. 3) or the releasing position P2 (see FIG. 4). The virtual line L1 connecting the center of the pressure pad 27 passes through the pressing region 30 of the pressure pad 27. Therefore, the displacement of the pressure pad 27 between the pressing position P1 and the releasing position P2 becomes small. Therefore, even when the pressing unit 22 is in the release position P2, the pressing force of the pressurizing pad 27 against the heat roller 21 does not decrease significantly. Therefore, the pressure belt 25 is driven by the heat roller 21 to rotate. Therefore, there is no problem in transporting a recording medium (laminated recording medium) such as a sheet.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, as well as in the scope of the invention described in the claims and the equivalent scope thereof.

12 to 15 ... image forming unit, 20, 120 ... fixing device, 21, 121 ... heat roller (first rotating body), 21a, 121a ... outer peripheral surface of heat roller, 22, 122 ... pressing unit, 23, 123 ... Biasing member, 24 ... Lamp (heat source), 25, 125 ... Pressurized belt (belt), 26, 126 ... Pressurized roller (second rotating body), 27, 127 ... Pressurized pad (pressing member), 28,128 ... Pressurized belt heat roller (belt support member), 30,130 ... Pressing area, 35,135 ... Rotating fulcrum, 141 ... Moving mechanism, 142 ... Detection mechanism, 143 ... Stop mechanism, 145 ... Roller holding member (First rotating body holding member) 146 ... Separation arm, 149 ... Contact convex portion (contact point), 200 ... Image forming apparatus, D1 ... First direction, D2 ... Second direction, C1 ... Central axis, P1 ... Pressing position, P2 ... Release position.

Claims (4)

The first rotating body heated by the heat source,
The belt facing the outer peripheral surface of the first rotating body, the second rotating body on which the belt is laid on the outer peripheral surface, the belt support member on which the belt is hung on the outer peripheral surface, and the belt. A pressing member having a pressing region for pressing toward the first rotating body and arranged between the second rotating body and the belt supporting member is provided.
A pressing position in which the belt is pressed against the first rotating body by the second rotating body by rotating around a rotation fulcrum located at a position away from the first rotating body, and the second rotating body. It is possible to switch between the release position where the pressing by the rotating body is released,
The line connecting the center of the first rotating body and the center of the rotating fulcrum when viewed from the axial direction of the first rotating body is the pressing member at both the pressing position and the releasing position. A pressing unit that passes through the pressing area and
The pressing unit is provided with an urging member that urges the second rotating body in a first direction in which the second rotating body approaches the first rotating body.
A first rotating body holding member attached to the first rotating body, and a separation arm rotatably supported by the pressing unit and capable of contacting the outer peripheral surface of the first rotating body holding member at a contact point. By rotating the separation arm in the direction of pressing the first rotating body holding member, the pressing unit is moved in a second direction opposite to the first direction with the contact point as a fulcrum. With a moving mechanism to move to
Fixing device equipped with. The fixing device according to claim 1.
A fixing device in which the outer peripheral surface of the first rotating body holding member is a cylindrical surface whose central axis coincides with the central axis of the first rotating body. The fixing device according to claim 1.
A fixing device further comprising a detection mechanism for detecting that the pressing unit is in the release position. The fixing device according to claim 3.
A fixing device further comprising a stop mechanism for outputting a signal for stopping paper feeding of plain paper when the pressing unit is in the release position.

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