Fixing device

Abstract

We provide a new type of fixing device that builds upon conventional technology. [Solution] A fixing device comprising a belt, a heater, a pressure roller, and a resin frame that rotatably supports the pressure roller, wherein the frame has a base surface facing the outer surface of the roller portion in the longitudinal direction and having a first rib and a second rib, the first rib and the second rib are aligned in the longitudinal direction, a first shape is formed on the first rib and a second shape is formed on the second rib, the first shape is a first through hole that penetrates the first rib in the longitudinal direction or a first groove formed in a part of the arc shape of the first rib, and the second shape is a second through hole that penetrates the second rib in the longitudinal direction or a second groove formed in a part of the arc shape of the second rib.

Description

Technical Field

[0001] The present invention relates to a fixing device attached to an electrophotographic image forming apparatus.

Background Art

[0002] The fixing device described in Patent Document 1 includes a heating unit having a heater that heats the inner surface of a belt, and a pressure roller that forms a nip portion together with the heater via the belt, and fixes the toner on the recording material.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to provide a new form of fixing device that develops on the basis of the conventional technology.

Means for Solving the Problems

[0005] One aspect of the present invention is a fixing device for fixing an image to a recording material, comprising: an endless belt; a heater for heating the inner surface of the belt; a pressure roller including a rubber roller portion that forms a nip portion for transporting the recording material in the transport direction together with the heater via the belt; and a resin frame that rotatably supports the pressure roller and faces the roller portion in the longitudinal direction of the pressure roller, wherein the frame has a base surface facing the outer circumferential surface of the roller portion in the longitudinal direction, and the base surface has a first rib and a second rib extending in an intersecting direction that intersects both the transport direction and the longitudinal direction. The fixing device is characterized in that, when viewed in the longitudinal direction, the shape of the tip of the first rib and the shape of the tip of the second rib are arc shapes that follow the outer surface of the roller portion, the first rib and the second rib are aligned in the longitudinal direction, a first shape is formed on the first rib and a second shape is formed on the second rib, the first shape is a first through hole that penetrates the first rib in the longitudinal direction or a first groove formed in a part of the arc shape of the first rib, and the second shape is a second through hole that penetrates the second rib in the longitudinal direction or a second groove formed in a part of the arc shape of the second rib.

[0006] Another aspect of the present invention is a fixing device for fixing an image to a recording material, comprising: an endless belt; a heater for heating the inner surface of the belt; a pressure roller including a roller portion that forms a nip portion for transporting the recording material in the transport direction together with the heater via the belt; and a resin frame that rotatably supports the pressure roller and faces the roller portion in the longitudinal direction of the pressure roller, wherein the frame has a base surface facing the outer circumferential surface of the roller portion in the longitudinal direction, and the base surface has a first rib and a second rib extending in an intersecting direction that intersects both the transport direction and the longitudinal direction, and the shape of the tip of the first rib and the shape of the tip of the second rib are arc shapes along the outer surface of the roller portion when viewed in the longitudinal direction. The fixing device is characterized in that, in the longitudinal direction, the first rib and the second rib are aligned, the base surface includes a first crossing rib having a first shape and a second crossing rib having a second shape, the first crossing rib and the second crossing rib are located between the first rib and the second rib in the longitudinal direction and extend in the longitudinal direction and the crossing direction, the first crossing rib and the second crossing rib are located in different positions in the conveying direction, the first shape is a first through hole penetrating the first crossing rib in the conveying direction or a groove formed at the tip of the first crossing rib in the crossing direction, and the second shape is a second through hole penetrating the second crossing rib in the conveying direction or a groove formed at the tip of the second crossing rib in the crossing direction.

[0007] Another aspect of the present invention is a fixing device for fixing an image to a recording material, comprising: an endless belt; a heater for heating the inner surface of the belt; a pressure roller including a roller portion that forms a nip portion for transporting the recording material in the transport direction together with the heater via the belt; and a resin frame that rotatably supports the pressure roller and faces the roller portion along the longitudinal direction of the pressure roller, wherein the frame has a base surface facing the roller portion in an intersecting direction that intersects the transport direction and the longitudinal direction, and includes a first rib and a second rib extending in the intersecting direction, the shape of the tip of the first rib and the shape of the tip of the second rib being arc-shaped along the outer surface of the roller portion when viewed in the longitudinal direction, the first rib and the second rib being aligned in the longitudinal direction, and the frame having a first through hole and a second through hole, the first through hole and the second through hole being formed in a position on the base surface that does not include the first rib and the second rib, and penetrating from the base surface to the outside of the frame.

[0008] Another aspect of the present invention is a fixing device for fixing an image to a recording material, comprising: an endless belt; a heater for heating the inner surface of the belt; a pressure roller including a roller portion that forms a nip portion for transporting the recording material in the transport direction together with the heater via the belt; and a resin frame that rotatably supports the pressure roller and faces the roller portion along the longitudinal direction of the pressure roller, wherein the frame has a base surface facing the roller portion in an intersecting direction that intersects the transport direction and the longitudinal direction, and includes a first rib and a second rib extending in the intersecting direction, the shape of the tip of the first rib and the shape of the tip of the second rib being arc-shaped along the outer surface of the roller portion when viewed in the longitudinal direction, the first rib and the second rib being aligned in the longitudinal direction, and the frame having a through hole that penetrates from the base surface to the outside of the frame and is located between the first rib and the second rib, and a temperature detection unit that penetrates the through hole and is arranged to face the pressure roller. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a new form of fixing device that is an advancement of the conventional technology. [Brief explanation of the drawing]

[0010] [Figure 1] A cross-sectional view in the short direction of the lower frame and pressure roller of the fixing device according to Example 1. [Figure 2] Cross-sectional view of the fixing device according to the embodiment. [Figure 3] Cross-sectional view of the fixing device according to the embodiment. [Figure 4] Cross-sectional view of the fixing device according to the embodiment. [Figure 5] An exploded perspective view of the fixing device according to the embodiment. [Figure 6] Front view (a) and cross-sectional views (b-d) of the fixing device according to the embodiment. [Figure 7] Cross-sectional views (a, b) of the fixing device according to the embodiment. [Figure 8] An exploded perspective view of the fixing device according to the embodiment. [Figure 9] A longitudinal cross-sectional view of the lower frame and pressure roller in Example 1. [Figure 10] Figures (a, b) showing the conveying direction ribs in Example 1 and figures (c-f) showing the conveying direction ribs in a modified example. [Figure 11] A longitudinal cross-sectional view of the lower frame and pressure roller in Example 2 (a), and a figure showing the through-holes of the longitudinal ribs in a modified example (b). [Figure 12] A perspective view (a) of the lower frame in Example 3 and an enlarged view of a part thereof (b). [Figure 13] A bottom view of the lower frame in Example 4. [Figure 14] Front view of the lower frame in Modification 1 of Example 4. [Figure 15] Rear view of the lower frame in modified example 2 of Example 4. [Figure 16] Front view of the lower frame in Modification 3 of Example 4. [Figure 17] Perspective view of the lower frame in Example 5. [Figure 18] Schematic diagram showing the short cross-section of the lower frame and the pressure roller in Example 5. [Figure 19] Schematic diagram showing the short cross-section of the lower frame and the pressure roller in a modified example of Example 5. [Figure 20] Diagrams (a, b) showing an example of the arrangement of the thermistors in Example 5.

Mode for Carrying Out the Invention

[0011] Hereinafter, embodiments according to the present disclosure will be described with reference to the drawings.

[0012] FIG. 2 is a cross-sectional view of an electrophotographic image forming apparatus 1 including a fixing device 6 as a fixing device according to an embodiment. In the following description, as shown in FIG. 2, when the image forming apparatus 1 is installed on a horizontal plane, the vertical direction is defined as the Z direction. The direction intersecting the Z direction is defined as the Y direction. The Y direction is the direction of the rotation axis of the pressure roller 62 described later. The direction intersecting both the Z direction and the Y direction is defined as the X direction. The X direction is parallel to the direction in which the heating unit 61 described later conveys the recording material located at the nip portion. The X direction and the Y direction are preferably horizontal directions. Further, the X direction, the Y direction, and the Z direction are preferably orthogonal to each other.

[0013] Furthermore, as needed, the directions of the arrows X, Y, and Z shown in each drawing will be referred to as the +X direction, +Y direction, and +Z direction, respectively, and the opposite directions will be referred to as the -X direction, -Y direction, and -Z direction, respectively. In the following explanation, the direction in which the recording material sheet S is conveyed in the nip section np1 described later will be called the sheet conveying direction D1. In the embodiment of Figure 2, the sheet conveying direction D1 is the direction along the +X direction. In addition, the direction of the rotation axis of the pressure roller 62 may be referred to as the axial direction, the longitudinal direction of the fuser 6, or simply the "longitudinal direction". In the axial direction, the direction from one end to the other end of the pressure roller 62 will be called the first axial direction (+Y direction). In the axial direction, the direction opposite to the first axial direction will be called the second axial direction (-Y direction). The Y direction is also the longitudinal direction of the fuser 6. Furthermore, the Y direction is the longitudinal direction or the busbar direction of the belt 614.

[0014] [Image forming apparatus] The configuration of the image forming apparatus 1 will be explained using Figure 2. The image forming apparatus 1 comprises an apparatus body 2, a process cartridge 10, and a fuser 6. The process cartridge 10 is detachably attached to the apparatus body 2. The fuser 6 is detachably attached to the apparatus body 2. It can also be said that the fuser 6 is mounted on the apparatus body 2. Note that the fuser 6 may be permanently attached.

[0015] The main unit 2 of the apparatus comprises a feed tray 3, a sheet feed section 4, a transport path P, a transfer roller 51, a sheet discharge section 7, a discharge tray 8, a laser scanner 9, and an opening / closing door 21. The process cartridge 10 comprises a photosensitive drum 11 and a developing roller 12 as a developer carrier. The process cartridge 10 also contains developer inside. The opening / closing door 21 is rotatably supported around a pivot axis 21a and is configured to move between a closed position that closes the opening 2a and an open position that opens the opening 2a. When the opening / closing door 21 is in the open position with the opening 2a open, the process cartridge 10 can be attached to and detached from the main unit 2 through the opening 2a.

[0016] The sheet feeding unit 4 consists of a feeding roller 41, a separation roller 42, a separation pad 42a, and a transport roller pair 43. Based on the print start signal, the sheet S stored in the feeding tray 3 is sent to the transport path P by the sheet feeding unit 4 and transported towards the transfer roller 51 via the register roller pair 44.

[0017] When the sheet S is transported to a predetermined position, an image formation start signal is issued, and the image formation process begins. The photosensitive drum 11, which is rotated by a drive source (motor) (not shown), is uniformly charged to a predetermined potential by a charging means (not shown). The surface of the charged photosensitive drum 11 is exposed by a laser scanner 9 based on image information, and an electrostatic image is formed in which the charge of the exposed area is removed. The toner in the process cartridge 10 is carried on the developing roller 12 and supplied to the photosensitive drum 11 according to the electrostatic latent image, developing the latent image. As a result, the latent image is made visible on the photosensitive drum 11 as a toner image.

[0018] The transfer roller 51 is positioned opposite the photosensitive drum 11 of the process cartridge 10. When the sheet S, conveyed by the registration roller pair 44, passes through the nip between the photosensitive drum 11 and the transfer roller 51, a voltage is applied to the transfer roller 51 from the main body of the device 2, and the toner image on the photosensitive drum 11 is transferred to the sheet S as an unfixed image. Subsequently, the sheet S with the transferred toner image is conveyed to the fuser 6, which is equipped with a heating unit 61 and a pressure roller 62. The fuser 6 is a fixing device that fixes toner (developer) to the recording material. When the sheet S passes through the nip between the heating unit 61 and the pressure roller 62, the unfixed image transferred on the sheet S is heated and pressurized and fixed to the surface of the sheet S. The sheet S with the fixed toner image is discharged to the discharge tray 8 via the sheet discharge section 7.

[0019] [Fuser] Next, the configuration of the fuser 6 will be described. Figure 3 is a plan view of the fuser 6. As will be explained in detail below, the fuser 6 comprises an endless belt 614 and a heater 611 that heats the inner surface of the belt 614. The fuser 6 also comprises a pressure roller 62 including a rubber roller section 62b that forms a nip section np1 for transporting the recording material in the transport direction (sheet transport direction D1) together with the heater 611 via the belt 614. The fuser 6 also comprises a resin frame (lower frame 63) that rotatably supports the pressure roller 62 and faces the roller section 62b along the longitudinal direction of the pressure roller 62.

[0020] As shown in Figure 3, the heating unit 61 comprises a heater 611, a holder 612, a stay 613, and a belt 614. The heater 611 is provided on the inner surface side of the belt 614 and heats the belt 614. The heater 611 extends in the longitudinal direction (Y direction) of the belt 614, and the shape of the heater 611 is flat. The heater 611 has a first surface 611a and a second surface 611b opposite to the first surface 611a, and the first surface 611a is supported by the holder 612.

[0021] The holder 612 is made of a heat-resistant resin such as PPS or liquid crystal polymer, and has a guide surface 612a and a support wall 612b. The guide surface 612a contacts the inner circumferential surface 614a of the belt 614 to guide the belt 614, and the support wall 612b has a support surface 612b1 that supports the heater 611. The support surface 612b1 of the support wall 612b is in contact with the first surface 611a of the heater 611. The stay 613 is a member that supports the holder 612, and is formed by bending a plate material with greater rigidity than the holder 612, for example, a steel plate with a thickness of 1.6 mm, into a roughly U-shape.

[0022] The belt 614 is a heating element (heating rotating body) that heats the image on the recording material. The belt 614 in this embodiment is an endless belt that is heat-resistant and flexible, and is composed of, for example, a metal sleeve such as stainless steel coated with fluororesin, or a laminate of polyimide resin, silicone rubber, fluororesin, etc. The belt 614 can also be described as a rotatable cylindrical film. A heater 611, a holder 612, and a stay 613 are arranged inside the belt 614, and the belt 614 is configured to rotate around these. The inner circumferential surface 614a of the belt 614 is in contact with the second surface 611b of the heater 611.

[0023] The pressure roller 62 has a metal shaft 62a and a roller portion 62b (outer circumference) made of an elastic material covering the shaft 62a, and is pressed against the heater 611 via the belt 614. The pressure roller 62 sandwiches the belt 614 between itself and the heater 611, forming a nip portion np1 for nipping, heating, and pressurizing the sheet S. In other words, the pressure roller 62, together with the heater 611 via the belt 614, forms the nip portion np1. That is, the pressure roller 62 is a rotating body that heats and pressurizes the sheet S together with the heater 611 in the nip portion np1. The nip portion np1 is the contact portion where the belt 614 and the pressure roller 62 come into contact.

[0024] The pressure roller 62 is configured to rotate when a driving force is transmitted from a drive source provided by the image forming apparatus 1. As the pressure roller 62 rotates, the belt 614 rotates in accordance with the pressure roller 62. The sheet S on which the toner image has been transferred is transported between the pressure roller 62 and the heated belt 614, thereby thermally fixing the toner image.

[0025] Next, the frame configuration of the fuser 6 will be explained using Figure 4. Figure 4 is a plan view of the fuser 6. The fuser 6 has an upper frame 64 and a lower frame 63. The upper frame 64 and the lower frame 63 constitute the frame of the fuser 6. The lower frame 63 can also be called the first frame, and the upper frame 64 can be called the second frame.

[0026] Note that the shape of the lower frame 63 shown in Figures 4 to 8 is just one example, and the detailed shape of the lower frame 63 will be explained in the embodiment described later.

[0027] The lower frame 63 is a frame that supports the heating unit 61 and the pressure roller 62. The upper frame 64 is located above the lower frame 63 and covers the heating unit 61. The lower frame 63 and the upper frame 64 are resin components formed from non-conductive molded members (resin members).

[0028] The upper frame 64 has an upper guide surface 64a located downstream of the heating unit 61 in the sheet conveying direction D1. The upper guide surface 64a guides the upper surface of the sheet S being conveyed in the sheet conveying direction D1. The lower frame 63 has a lower guide surface 63a located downstream of the heating unit 61 in the sheet conveying direction D1. The lower guide surface 63a guides the lower surface of the sheet S being conveyed in the sheet conveying direction D1.

[0029] Next, the configuration of the lower frame 63 that supports the pressure roller 62 will be described using Figure 5. Figure 5 is an exploded perspective view of the fuser 6. The lower frame 63 has rails 63b at its ends in the first axial direction and the second axial direction, respectively. The rails 63b extend vertically and support the holder 612 so that it can move vertically. The two rails 63b face each other in the axial direction. The rails 63b engage with grooves 617a1 and 617b1 provided in the transmission members 617a and 617b, respectively.

[0030] The fixing unit 6 includes bearings 62c and 62d. The ends of the shaft 62a in the first axial direction and the ends in the second axial direction are supported by bearings 62c and 62d, respectively. Bearing 62c is positioned by fitting into a recess 63d1 provided in the lower frame 63. Similarly, bearing 62d is positioned by fitting into a recess 63d2 provided in the lower frame 63. Bearing 62c is electrically conductive. In this configuration, bearings 62c and 62d have protrusions and the lower frame 63 has recesses 63d1 and 63d2, but the relationship between the protrusions and recesses may be reversed. Also, the means for fixing bearings 62c and 62d to the lower frame 63 does not have to be of a protrusion-recess shape.

[0031] [Pressurization mechanism] Next, the pressurizing mechanism of the fuser 6 will be explained. Figure 6(a) is a front view of the fuser 6. Figures 6(b) to (d) are cross-sectional views of Figure 6(a) in the short direction. The short-side cross-section of the fuser 6 (short-side cross-section) refers to the cross-section of the fuser 6 by a virtual plane perpendicular to the longitudinal direction (Y direction) of the fuser 6. Furthermore, the longitudinal cross-section of the fuser 6 (long-side cross-section), which will be described later, refers to the cross-section of the fuser 6 by a virtual plane parallel to the longitudinal direction (Y direction) of the fuser 6 (in particular, the plane containing the rotation axis of the pressure roller 62).

[0032] As shown in Figures 6(a) to (d), the fuser 6 has a pressurizing mechanism 65 for pressurizing the nip portion np1. In this embodiment, the pressurizing mechanism 65 presses the heating unit 61 against the pressurizing roller 62. The pressurizing mechanism 65 is provided at both the end of the lower frame 63 in the first axial direction and the end in the second axial direction. In other words, it can be said that the pressurizing mechanism 65 is supported by the lower frame 63. The structure of the pressurizing mechanism 65 provided on the end of the lower frame 63 in the first axial direction and the pressurizing mechanism 65 provided on the end of the lower frame 63 in the second axial direction are substantially the same. Therefore, the explanation of the pressurizing mechanism 65 provided on the first axial direction side also applies to the pressurizing mechanism 65 provided on the second axial direction side, so the explanation is omitted.

[0033] The pressurizing mechanism 65 includes a transmission member 651, a pressurizing arm 652, and a pressurizing spring 653. The pressurizing arm 652 is supported by a lower frame 63. More specifically, the pressurizing arm 652 is supported by a support portion 64d of the lower frame 63 and is rotatably supported around the central axis X1 of the support portion 64d. The support portion 64d is a substantially cylindrical projection.

[0034] The pressure arm 652 presses the transmission member 651 from above, moving the transmission member 651 downward. This causes the transmission member 651 to press the stay 613 downward. The transmission member 651 presses the stay 613, moving the stay 613 downward. As the stay 613 moves downward, the heating unit 61, which includes the stay 613, is pressed toward the pressure roller 62. The pressure spring 653 is a conductive tension coil spring that biases the pressure arm 652 so that the heating unit 61 is pressed toward the pressure roller 62. The pressure spring 653 engages with the lower frame 63 and the pressure arm 652. The biasing of the pressure arm 652 by the pressure spring 653 causes the pressure arm 652 to move the transmission member 651 downward. That is, the pressure arm 652 presses the heating unit 61 toward the pressure roller 62.

[0035] [Pressure release mechanism] Next, the configuration of the pressure release mechanism of the fuser 6 will be explained using Figures 7(a) and 7(b), and Figure 8. Figures 7(a) and 7(b) are cross-sectional views of the fuser 6 in the short direction. Figure 7(a) shows the pressurized state in which the pressure release mechanism 67 allows pressurization of the nip portion np1. Figure 7(b) shows the pressure-released state in which the pressure release mechanism 67 releases the pressurization of the nip portion np1. Figure 8 is an exploded perspective view of the upper frame 64, lower frame 63, and camshaft 671, with some parts such as the heating unit 61 and pressure roller 62 omitted.

[0036] The pressure release mechanism 67 is a nip pressure release mechanism that changes the nip pressure in the nip portion np1 between the heating unit 61 and the pressure roller 62. The pressure release mechanism 67 comprises a camshaft 671 and a cam 672.

[0037] As shown in Figures 7(a) and 7(b), the camshaft 671 is rotatable about the central axis X2. The camshaft 671 extends axially and is made of a conductive metal. As shown in Figure 8, cams 672 are fixed (supported) to the first axial end and the second axial end of the camshaft 671, respectively. The cams 672 are supported so as to rotate together with the camshaft 671. The cams 672 are provided on the first axial end side and the second axial end side of the lower frame 63, respectively. The structure of the cam 672 provided on the first axial end side and the cam 672 provided on the second axial end side of the lower frame 63 are substantially identical.

[0038] The cam 672 presses against the pressurizing arm 652 against the biasing force of the pressurizing spring 653. In other words, the rotation of the cam 672 changes the pressing force applied by the pressurizing arm 652 to the pressurizing roller 62 of the heating unit 61. The cam 672 is rotatable between the pressurizing position shown in Figure 7(a) and the release position shown in Figure 7(b).

[0039] To release the pressurized state, the camshaft 671 is rotated, causing the cam 672 to rotate. When the cam 672 rotates, the pressurizing arm 652, which is in contact with the cam 672, moves away from the transmission member 651 in the opposite direction to the direction in which the stay 613 is pressed against the transmission member 651. As a result, the pressure that presses the heating unit 61 toward the pressurizing roller 62 decreases.

[0040] Next, the support configuration of the camshaft 671 will be described using Figure 8. The lower frame 63 has a support wall 631 that rotatably supports the camshaft 671. The support wall 631 extends in the vertical direction (Z direction). The support wall 631 has a hole 631h that rotatably supports the camshaft 671. The camshaft 671 passes through the hole 631h. In other words, the support wall 631 can also be called a shaft support portion that supports the camshaft 671. The support wall 631 is provided on the end side in the first axial direction of the lower frame 63 and on the end side in the second axial direction of the lower frame 63. In addition, substantially the same hole 631h is provided in each support wall 631.

[0041] The upper frame 64 has a support wall 641 that rotatably supports the camshaft 671. The support wall 641 extends vertically. The support wall 641 has a hole 641h that rotatably supports the camshaft 671. The camshaft 671 passes through the hole 641h. The support wall 641 is provided at the end of the upper frame 64 in the first axial direction and at the end of the lower frame 63 in the second axial direction. In addition, substantially the same hole 641h is provided in each support wall 641. [Examples]

[0042] The configuration of the fuser 6 according to Embodiment 1, which is an example of this embodiment, will now be described. This embodiment proposes a configuration for a fuser 6 that has multiple ribs extending in the sheet transport direction D1, which reduces the influence of water vapor generated from the recording material.

[0043] [Effects of water vapor generated from the sheet] First, let's explain the effect of water vapor generated from the sheet S as it passes through the nip section np1 of the fuser unit 6. In particular, in high temperature and high humidity environments, the paper used as the sheet S placed in the feed tray 3 contains a lot of moisture. When this moisture-absorbing paper passes through the nip section np1, the paper is heated along with the toner image, causing water vapor to be generated from the paper. If the generated water vapor condenses on the surface of the pressure roller 62, the frictional force with the sheet S decreases, and the sheet S may slip, causing the image to be distorted. In addition, the frictional force may change in different areas due to condensation, causing the transport force that the sheet S receives from the pressure roller 62 to differ depending on the position in the longitudinal direction, which may result in wrinkles in the sheet S.

[0044] [Reinforcement ribs on the lower frame] Next, the shape and arrangement of the reinforcing ribs 80 provided on the lower frame 63 (frame) in this embodiment will be described below.

[0045] Figure 9 is a cross-sectional view showing the longitudinal section of the lower frame 63 with the pressure roller 62 attached. As shown in Figures 4, 5, and 9, one or more reinforcing ribs 80 are arranged on the lower frame 63.

[0046] The lower frame 63 has a base surface 630d, a front surface 630a facing upstream in the sheet conveying direction D1, a bottom surface 630b facing downward, a rear surface 630c facing downstream in the sheet conveying direction D1, and reinforcing ribs 80.

[0047] The base surface 630d is the back surface (inner surface of the lower frame 63) of the front surface 630a, bottom surface 630b, and rear surface 630c, which are the surfaces facing outward from the lower frame 63. The base surface 630d is opposite the outer circumferential surface (outer surface) of the roller portion 62b of the pressure roller 62. As shown in Figure 4, when viewed in the longitudinal direction, at least a portion of the pressure roller 62 is housed in the space enclosed by the base surface 630d.

[0048] The reinforcing rib 80 is provided on the base surface 630d so as to extend in the intersecting direction D2. In other words, the reinforcing rib 80 is formed to project from the base surface 630d toward the outer circumferential surface of the pressure roller 62. The intersecting direction D2 is the direction that intersects both the longitudinal direction (Y direction) and the sheet conveying direction D1 of the pressure roller 62. The intersecting direction D2 may be the direction that is perpendicular to both the longitudinal direction (Y direction) and the sheet conveying direction D1 of the pressure roller 62.

[0049] The base surface 630d, front surface 630a, bottom surface 630b, and rear surface 630c constitute the main body 630 of the lower frame 63 which extends in the longitudinal direction. The reinforcing ribs 80 can be said to be supported by the main body 630. The reinforcing ribs 80 and the main body 630 are integrally formed from a resin material.

[0050] In this embodiment, the lower frame 63 has one or more conveying directional ribs 801 as reinforcing ribs 80. In the example shown in Figure 9, the lower frame 63 has multiple conveying directional ribs 801. In other words, the "frame" in this embodiment has a first rib and a second rib. An example of the first rib is one of the multiple conveying directional ribs 801 (for example, conveying directional rib 801-1 in Figure 9), and an example of the second rib is the other of the multiple conveying directional ribs 801 (for example, conveying directional rib 801-2 in Figure 9).

[0051] In this embodiment, the multiple conveying ribs 801 are arranged at approximately equal intervals in the longitudinal direction. The multiple conveying ribs 801 can be said to include a first rib (conveying rib 801-1) and a second rib (conveying rib 801-2) that are aligned in the longitudinal direction.

[0052] One end of the base surface 630d in the longitudinal direction is designated as the first end 630d1, and the other end as the second end 630d2 (Figure 9). In the longitudinal direction, the first rib (conveying direction rib 801-1) is closer to the first end 630d1 than to the second end 630d2, and the second rib (conveying direction rib 801-2) is closer to the second end 630d2 than to the first end 630d1. In other words, the first rib and the second rib may be positioned on opposite sides of the center of the base surface 630d in the longitudinal direction.

[0053] The lower frame 63 may have longitudinal ribs 803 (Figures 4 and 5) extending in the longitudinal direction (Y direction). In other words, the reinforcing rib 80 may include one or more conveying direction ribs 801 and one or more longitudinal ribs 803. In this embodiment, the reinforcing rib 80 may consist only of conveying direction ribs 801 and not include longitudinal ribs 803.

[0054] The longitudinal ribs 803 are formed, for example, over the entire length of at least the roller portion 62b of the pressure roller 62 in the longitudinal direction. The longitudinal ribs 803 may also be formed over the entire base surface 630d in the longitudinal direction. Furthermore, the longitudinal ribs 803 are formed to intersect with each of the multiple conveying direction ribs 801.

[0055] The reinforcing ribs 80 enhance the rigidity of the lower frame 63, which is formed from molded material. By increasing the rigidity with the reinforcing ribs 80, it is possible to prevent the lower frame 63 from bending due to the heat emitted from the heating unit 61 and pressure roller 62, and the load applied via the pressure mechanism 65, and further prevent creep deformation due to long-term use.

[0056] Figure 1 is a cross-sectional view of the lower frame 63 with the pressure roller 62 attached, showing a cross-section in a virtual plane passing through the conveying direction rib 801 (801-1) (DD cross-section in Figure 9). Figure 10(a) is a view of one conveying direction rib 801-1 in the longitudinal direction. Figure 10(b) is a view of the other conveying direction rib 801-2 in the longitudinal direction.

[0057] As shown in Figure 1, the tip 801a (ridge) of each conveying rib 801 in this embodiment is formed in an arc shape along the outer surface of the pressure roller 62.

[0058] [Groove portion of reinforcing rib] At least one conveying rib 801 is provided with a groove 801b. The groove 801b is formed in part of the arc shape of the tip 801a and is a groove (recess) that is recessed on the side away from the rotation axis of the pressure roller 62 compared to the arc shape of the tip 801a.

[0059] The groove 801b-1 (Figure 10(a)) provided on the conveying direction rib 801-1 (first rib) is an example of the first groove, and the groove 801b-2 (Figure 10(b)) provided on the conveying direction rib 801-2 (second rib) is an example of the second groove. Furthermore, the groove 801b-1 provided on the conveying direction rib 801-1 (first rib) is an example of the first shape, and the groove 801b-2 provided on the conveying direction rib 801-2 (second rib) is an example of the second shape.

[0060] The groove 801b connects the small spaces between the outer circumferential surface of the pressure roller 62 and the base surface 630d of the lower frame 63, which are separated by the conveying direction rib 801. In other words, the groove 801b forms a path in the longitudinal direction that allows air containing water vapor to move.

[0061] Furthermore, for example, a blower fan attached to the main body 2 may be used to actively generate a longitudinal airflow through the groove 801b.

[0062] [Function of the groove] If the small spaces partitioned by the transport direction ribs 801 are highly airtight (meaning there is little air movement between adjacent small spaces), then air may accumulate in these small spaces. If air accumulates in these small spaces, water vapor generated from the sheet S during image fixing can build up, causing condensation on the pressure roller 62, which could lead to the aforementioned problems.

[0063] As in this embodiment, by providing a groove 801b at the tip of the transport direction rib 801, air stagnation can be suppressed, and condensation on the pressure roller 62 can be suppressed even in environments where the sheet S contains a lot of moisture, such as high temperature and high humidity environments. In other words, the longitudinal airflow through the groove 801b allows water vapor generated from the sheet S during image fixing to escape from the vicinity of the outer surface of the pressure roller 62.

[0064] Figures 10(a) and 10(b) show the transport direction ribs 801-1 and 801-2, which are adjacent in the longitudinal direction. In the longitudinal direction, the transport direction rib 801-1 (first rib) and the transport direction rib 801-2 (second rib) face each other (Figure 9).

[0065] In the illustrated example, two grooves 801b-1 are formed in the first conveying rib 801-1 (Figure 10(a)), and two grooves 801b-2 are formed in the second conveying rib 801-2 (Figure 10(b)). The number of grooves 801b formed in the conveying ribs 801-1 and 801-2 may be different from each other.

[0066] In the example shown in Figures 10(a) and 10(b), when viewed in the longitudinal direction (Y direction), the groove 801b-1 formed on the first conveying direction rib 801-1 and the groove 801b-2 formed on the second conveying direction rib 801-2 do not overlap. The dashed line shown in Figure 10(a) is a perspective view of the position of the groove 801b-2 of the second conveying direction rib 801-2 on the first conveying direction rib 801-1 when viewed in the longitudinal direction (Y direction). By arranging the grooves 801b between adjacent conveying direction ribs 801-1 and 801-2 so that they do not overlap, water vapor in the small space between adjacent conveying direction ribs 801 can be evenly discharged.

[0067] On the other hand, unlike the examples in Figures 10(a) and 10(b), the grooves 801b may overlap between adjacent conveying ribs 801-1 and 801-2 when viewed in the longitudinal direction (Y direction). Figure 10(c) shows an example of an arrangement where the groove 801b-1 of the first conveying rib 801-1 and the groove 801b-2 of the second conveying rib 801-2 overlap when viewed in the longitudinal direction (Y direction). In this case, the airflow in the longitudinal direction becomes smoother, and the amount of air passing between the outer surface of the pressure roller 62 and the lower frame 63 can be increased. Whether the grooves 801b overlap or not when viewed in the longitudinal direction can be changed depending on the specific configuration of the fuser 6 (especially the design of the airflow path) and the position of the blower fan.

[0068] In the direction of the airflow generated by the blower fan, the area of ​​the groove 801b of the downstream conveying direction rib 801 may be larger than the area of ​​the groove 801b of the upstream conveying direction rib 801. In this case, for example, air can be discharged more smoothly than when the area of ​​the groove 801b of the downstream conveying direction rib 801 is smaller, and water vapor is less likely to accumulate.

[0069] (modified version) In this embodiment, the first and second grooves are described as rectangular grooves 801b that extend elongated in a direction perpendicular to the sheet conveying direction D1. However, the shape of the grooves 801b is not limited to this, and for example, a semicircular groove 801b may be formed when viewed in the longitudinal direction. Also, although Figure 1 shows an example in which two grooves 801b are formed on one conveying direction rib 801, one or more grooves 801b may be formed on one conveying direction rib 801. If there are multiple conveying direction ribs 801, the grooves 801b may be formed on only some of the conveying direction ribs 801.

[0070] In this embodiment, an example of suppressing water vapor accumulation was described by providing grooves 801b (first groove, second groove) as examples of the first and second shapes. However, as shown in Figures 10(d) and 10(e), a through hole 801c may be formed in the conveying direction rib 801 instead of the grooves 801b. In other words, a hole that penetrates in the longitudinal direction (Y direction) may be formed in the part of the conveying direction rib 801 closer to the root (towards the base surface 630d) than the tip 801a. By forming a through hole 801c in the conveying direction rib 801, the movement of air between the small spaces partitioned by the conveying direction rib 801 becomes easier, which helps to discharge water vapor.

[0071] Figure 10(d) shows an example of a first conveying rib 801-1 (first rib) in which a through-hole 801c-1 (first through-hole) is formed. Figure 10(e) shows an example of a second conveying rib 801-2 (second rib) in which a through-hole 801c-2 (second through-hole) is formed. As shown in Figure 10(d), when the through-hole 801c-1 (first through-hole, first shape) and the through-hole 801c-2 (second through-hole, second shape) overlap in the longitudinal direction, the airflow in the longitudinal direction becomes smoother.

[0072] On the other hand, as shown in Figure 10(f), the through-holes 801c-1 (first through-hole, first shape) and 801c-2 (second through-hole, second shape) may be arranged so that they do not overlap when viewed in the longitudinal direction. In this case, it becomes easier to discharge water vapor without leakage from the small space partitioned by the conveying direction ribs 801-1 and 801-2.

[0073] The shape of the through-hole may be, for example, circular, elliptical, or quadrilateral (including parallelograms and rounded quadrilaterals). There may be one or more through-holes. [Examples]

[0074] Embodiment 2 of this disclosure will now be described. This embodiment differs from Embodiment 1 in that grooves are provided in the longitudinal ribs 803 (Figures 4 and 5) which serve as intersecting ribs. Hereafter, elements with reference numerals common to Embodiment 1 will have basically the same configuration and function as those described in Embodiment 1 unless otherwise specified, and the differences from Embodiment 1 will be described mainly.

[0075] Figure 11(a) is a cross-sectional view showing the longitudinal section of the lower frame 63 to which the pressure roller 62 is mounted (a cross-section taken by a virtual plane passing through one of the longitudinal ribs 803). The longitudinal ribs 803 protrude in the direction of intersection D2 from the base surface 630d toward the outer circumferential surface of the pressure roller 62 (i.e., toward upward), and each extends in the longitudinal direction (Y direction). The tip 803a (ridge) of the longitudinal rib 803 is formed linearly, for example, along the outer circumferential surface of the pressure roller 62.

[0076] The lower frame 63 may have a conveying direction rib 801 (Figure 5). In other words, the reinforcing rib 80 may include one or more conveying direction ribs 801 and one or more longitudinal direction ribs 803. In this embodiment, the reinforcing rib 80 may consist only of longitudinal direction ribs 803 and not include a conveying direction rib 801.

[0077] The lower frame 63 of this embodiment is provided with two longitudinal ribs 803 (see also Figure 4). Each longitudinal rib 803 extends longitudinally, intersecting with a plurality of conveying direction ribs 801. The first longitudinal rib 803-1 is an example of a first intersecting rib that extends longitudinally to connect the conveying direction rib 801-1 (first rib) and the conveying direction rib 801-2 (second rib). The second longitudinal rib 803-2 is a second intersecting rib that extends longitudinally to connect the conveying direction rib 801-1 (first rib) and the conveying direction rib 801-2 (second rib), and is an example of a second intersecting rib that faces the first intersecting rib in the sheet conveying direction D1. Furthermore, the longitudinal ribs 803-1 and 803-2 are located between the transport direction rib 801-1 (first rib) and the transport direction rib 801-2 (second rib) in the longitudinal direction, and include the first and second intersecting ribs as portions extending in the longitudinal direction (Y direction) and the intersecting direction D2.

[0078] One end of the base surface 630d in the sheet conveying direction D1 is designated as the first end 630d3, and the other end as the second end 630d4 (Figure 4). In the sheet conveying direction, the first cross rib (longitudinal rib 803-1) is closer to the first end 630d3 than to the second end 630d4. The second cross rib (longitudinal rib 803-2) is closer to the second end 630d4 than to the first end 630d3. In other words, the first cross rib and the second cross rib may be positioned on opposite sides of the base surface 630d in the sheet conveying direction D1, with the center of the base surface 630d in between.

[0079] The number of longitudinal ribs 803 may be one or three or more.

[0080] [Groove portion of reinforcing rib] At least one longitudinal rib 803 is provided with a groove 803b. The groove 803b has a groove shape (recess, notch) in which a portion of the tip 803a is recessed.

[0081] The groove 803b provided on the longitudinal rib 803-1 (first intersecting rib) (Figure 11(a)) is an example of the first groove, and the groove 803b provided on the longitudinal rib 803-2 (second intersecting rib) is an example of the second groove. Furthermore, the groove 803b provided on the longitudinal rib 803-1 (first intersecting rib) is an example of the first shape, and the groove 803b provided on the longitudinal rib 803-2 (second intersecting rib) is an example of the second shape.

[0082] The groove 803b connects the small spaces between the outer circumferential surface of the pressure roller 62 and the base surface 630d of the lower frame 63, which are separated by the longitudinal ribs 803. In other words, the groove 803b forms a path that allows water vapor-containing air to move in the rotational direction of the pressure roller 62. The groove 803b also allows air to move from the upstream side to the downstream side (or in the opposite direction) in the sheet conveying direction D1.

[0083] Airflow through the groove 803b is generated, for example, by the rotation of the pressure roller 62. Airflow through the groove 803b is also generated by the sheet S passing through the nip portion np1. In addition, airflow through the groove 803b may be actively generated, for example, by a blower fan attached to the main body of the device 2.

[0084] [Function of the groove] As in this embodiment, by providing grooves 803b at the tips of the longitudinal ribs 803, it is possible to suppress the accumulation of water vapor-containing air between the lower frame 63 and the pressure roller 62. Furthermore, condensation on the pressure roller 62 can be suppressed even in environments where the sheet S contains a lot of moisture, such as high temperature and high humidity environments. In other words, the airflow through the grooves 803b allows water vapor generated from the sheet S during image fixing to escape from the vicinity of the outer surface of the pressure roller 62.

[0085] Similar to the groove 803b of the conveying rib 801 described in Example 1, when grooves 803b are provided on each of the adjacent longitudinal ribs 803 in the sheet conveying direction D1, the positions of the grooves 803b in the longitudinal direction may overlap. That is, as shown at the left end of Figure 11(a), when viewed in the sheet conveying direction D1, the groove 803b-1 (first shape) of the first longitudinal rib 803-1 (first intersecting rib) and the groove 803b-2 (second shape) of the second longitudinal rib 803-2 (second intersecting rib) may overlap. In this case, the airflow in the rotational direction of the pressure roller 62 becomes smoother, and the amount of air passing between the outer surface of the pressure roller 62 and the lower frame 63 can be increased.

[0086] In contrast, when grooves 803b are provided on each of adjacent longitudinal ribs 803 in the sheet conveying direction D1, the positions of the grooves 803b in the longitudinal direction may be arranged so as not to overlap. That is, as shown at the right end of Figure 11(a), when viewed in the sheet conveying direction D1, the groove 803b-1 of the first longitudinal rib 803-1 and the groove 803b-2 of the second longitudinal rib 803-2 may not overlap. By arranging the grooves 803b of adjacent longitudinal ribs 803 so as not to overlap, water vapor in the small space between adjacent longitudinal ribs 803 can be evenly discharged.

[0087] Although Figure 11(a) shows a roughly semicircular groove 803b, the shape of the groove 803b is not limited to this, and may be rectangular or triangular, for example. Also, although Figure 11(a) shows an example in which multiple grooves 803b are arranged at roughly equal intervals in the longitudinal direction (Y direction) on a single longitudinal rib 803, for example, only one groove 803b may be provided in the center of the longitudinal rib 803. If there are multiple longitudinal ribs 803, the grooves 803b may be formed on only some of the longitudinal ribs 803.

[0088] (modified version) In this embodiment, an example was described in which water vapor accumulation is suppressed by providing a groove 803b in the longitudinal rib 803. However, as shown in Figure 11(b), a through hole 803c may be formed in the longitudinal rib 803 instead of the groove 803b. In other words, a hole that penetrates in the direction of rotation of the pressure roller 62 may be formed in the portion of the longitudinal rib 803 closer to the root (towards the base surface 630d) than the tip 803a. By forming a through hole 803c in the longitudinal rib 803, the movement of air between the small spaces partitioned by the longitudinal rib 803 becomes easier, which helps to discharge water vapor.

[0089] Figure 11(b) shows an example of a first longitudinal rib 803-1 (first intersecting rib) in which a through-hole 803c (first through-hole) is formed. A similar through-hole 803c (second through-hole) may be formed in the second longitudinal rib 803-2 (second intersecting rib). As shown at the left end of Figure 11(b), the through-hole 803c-1 (first through-hole) of the first longitudinal rib 803-1 and the through-hole 803c-2 (second through-hole) of the second longitudinal rib 803-2 (second intersecting rib) may overlap when viewed in the sheet conveying direction D1. In this case, the airflow in the sheet conveying direction D1 becomes smoother. In contrast, as shown at the right end of Figure 11(b), the through-hole 803c-1 of the first longitudinal rib 803-1 and the through-hole 803c-2 of the second longitudinal rib 803-2 may be in a positional relationship where they do not overlap when viewed in the sheet conveying direction D1. In this case, it becomes easier to discharge water vapor without leakage from the small space between the longitudinal ribs 803-1 and 803-2.

[0090] Furthermore, in this embodiment, an example was described in which multiple grooves 803b of equal size and shape are arranged at approximately equal intervals. However, this is not limited to this example, and the size and shape of the multiple grooves or through holes may differ from one another, and the arrangement of multiple grooves or through holes in the longitudinal direction (Y direction) does not have to be at equal intervals. For example, if condensation on the pressure roller 62 is more likely to occur in the central region in the longitudinal direction than in the region including the ends of the roller portion 62b of the pressure roller 62 on the outside, the spacing between adjacent grooves in the central region may be narrower than the spacing between adjacent grooves in the regions at both ends. Also, in a similar case, the size of the grooves in the central region may be smaller than the size of the grooves in the regions at both ends.

[0091] Furthermore, the groove 803b only needs to be provided on at least one of the multiple longitudinal ribs 803, but each of the multiple longitudinal ribs 803 may also have a groove 803b. In this case, for example, if the arrangement of the grooves 803b in the longitudinal direction is aligned among the multiple longitudinal ribs 803, the airflow in the rotational direction of the pressure roller 62 can be made smoother. On the other hand, if the arrangement of the grooves 803b in the longitudinal direction is different among the multiple longitudinal ribs 803, it becomes easier to evenly discharge water vapor from the small spaces partitioned by the longitudinal ribs 803. [Examples]

[0092] Embodiment 3 of this disclosure is described below. This embodiment differs from Embodiment 1 in that a recess is provided at the intersection 802 of the conveying rib 801 and the longitudinal rib 803. In the following description, elements with the same reference numerals as in Embodiment 1 have basically the same configuration and function as those described in Embodiment 1 unless otherwise specified, and the differences from Embodiment 1 will be described mainly.

[0093] Figure 12(a) is a perspective view of the lower frame 63. Figure 12(b) is an enlarged view of the intersection 802 between the conveying direction rib 801 (first conveying direction rib 801-1) and the longitudinal direction rib 803 (first longitudinal direction rib 803-1).

[0094] As shown in Figures 12(a) and 12(b), the lower frame 63 of this embodiment is provided with a recess 802b at at least one of the intersections 802 where the conveying rib 801 and the longitudinal rib 803 intersect. The recess 802b is recessed on the side further away from the rotation axis of the pressure roller 62 compared to the tip 801a of the conveying rib 801, and also recessed on the side further away from the rotation axis of the pressure roller 62 compared to the tip 803a of the longitudinal rib 803. In other words, the tip (802b) of the intersection 802 in the intersecting direction D2 is recessed more than the tip 803a of the longitudinal rib 803-1 (first intersecting rib) in the intersecting direction D2.

[0095] The recess 802b can be described as a groove formed by a recess in part of the tip 801a of the conveying rib 801. Furthermore, the recess 802b can be described as a groove formed by a recess in part of the tip 803a of the longitudinal rib 803. Therefore, the recess 802b is an example of the first and second grooves of the first and second ribs described in Example 1, and also an example of the first and second grooves of the first and second intersecting ribs described in Example 2.

[0096] In this embodiment, one longitudinal rib 803 intersects with multiple conveying ribs 801. The recesses 802b are provided at each of the multiple intersections 802 where the one longitudinal rib 803 and the multiple conveying ribs 801 intersect.

[0097] [Function of the recess] The recess 802b in this embodiment provides the same function as the groove 801b of the conveying direction rib 801 and the groove 803b of the longitudinal direction rib 803 described in Embodiment 1. That is, by providing the recess 802b, the small spaces separated by the conveying direction rib 801 and the longitudinal direction rib 803 are connected, and water vapor is more easily discharged by the airflow through the recess 802b.

[0098] Furthermore, since the intersection 802 where the longitudinal rib 803 and the transport direction rib 801 intersect has relatively high rigidity to begin with, the reduction in rigidity of the lower frame 63 due to the provision of the recess 802b can be suppressed. As a result, deflection of the lower frame 63 due to pressure on the nip portion np1 and the occurrence of creep deformation due to long-term use can be suppressed. In addition, since it is easier to ensure the rigidity of the lower frame 63 without increasing the wall thickness of the lower frame 63, which is a molded member, there is an advantage in that the fuser 6 (and the entire image forming apparatus 1) can be made lighter and the amount of resin raw material used can be reduced.

[0099] (modified version) In Example 3, an example was described in which recesses 802b are provided at all of the multiple intersections 802 where a single longitudinal rib 803 intersects with multiple conveying ribs 801. However, recesses 802b may be formed at only some of the multiple intersections 802. Furthermore, the shape of the recesses 802b is not limited to that shown in Figure 12(b). [Examples]

[0100] Embodiment 4 of this disclosure is described below. This embodiment differs from Embodiment 1 in that through holes 630h are provided in the lower frame 63 in a portion other than the reinforcing rib 80. In the following description, elements denoted by the same reference numerals as in Embodiment 1 have basically the same configuration and function as those described in Embodiment 1 unless otherwise specified, and the parts that differ from Embodiment 1 will be described mainly.

[0101] Figure 13 is a bottom view showing the lower frame 63 of this embodiment as seen from below. More specifically, Figure 13 shows the lower frame 63 of this embodiment as seen from the viewpoint of looking from below to above in Figure 4, in a direction perpendicular to both the longitudinal direction (Y direction) and the sheet transport direction D1.

[0102] In this embodiment, the lower frame 63 has a plurality of through holes 630h formed therein. Each through hole 630h is formed in a position that does not include the reinforcing ribs 80 (transport direction ribs 801 and longitudinal direction ribs 803) of the base surface 630d. Any one of the plurality of through holes 630h can be called the first hole or first through hole, and the other one of the plurality of through holes 630h can be called the second hole or second through hole. In this case, the first hole and the second hole (first through hole and second through hole) are aligned in the longitudinal direction.

[0103] In this embodiment, the lower frame 63 has a lower through-hole 630h-1 formed therein, which penetrates from the base surface 630d to the bottom surface 630b, as an example of a through-hole 630h. The lower through-hole 630h-1 penetrates the bottom surface 630b from top to bottom. In the illustrated example, six lower through-holes 630h-1 are arranged at intervals from each other in the longitudinal direction.

[0104] The lower through-hole 630h-1 connects the inner space of the lower frame 63 (the space between the bottom surface 630b and the outer surface of the pressure roller 62) with the outer space of the lower frame 63. In other words, the lower through-hole 630h-1 forms a path that allows water vapor to escape from the inner space to the outer space of the lower frame 63.

[0105] [Function of through holes] As in this embodiment, by providing through holes (ventilation holes) in the lower frame 63, it is possible to suppress the accumulation of water vapor-containing air between the lower frame 63 and the pressure roller 62. Furthermore, condensation on the pressure roller 62 can be suppressed even in environments where the sheet S contains a lot of moisture, such as high temperature and high humidity environments.

[0106] Furthermore, in this embodiment, it is not necessary to provide through holes or grooves in the reinforcing rib 80. Therefore, it is possible to suppress condensation on the pressure roller 62 while minimizing the impact on the rigidity of the lower frame 63.

[0107] (modified version) In Example 4, an example was shown in which a lower through-hole 630h-1 is made in the bottom surface 630b of the lower frame 63, but through-holes may also be provided in other parts of the lower frame 63. Figure 14 is a view of the lower frame 63 according to one modified example (Modification Example 1) from the upstream side in the sheet conveying direction D1. In Modification Example 1, a plurality of front through-holes 630h-2 are formed as through-holes 630h, penetrating from the base surface 630d to the front surface 630a of the lower frame. The front through-holes 630h-2 penetrate from the base surface 630d to the outside of the lower frame 63 in the opposite direction to the sheet conveying direction D1.

[0108] Figure 15 is a view of the lower frame 63 according to another modified example (modification 2) as seen from the downstream side in the sheet conveying direction D1. In modification 2, a plurality of rear through holes 630h-3 are formed as through holes 630h, penetrating from the base surface 630d to the rear surface 630c of the lower frame. The rear through holes 630h-3 penetrate from the base surface 630d to the outside of the lower frame 63 in the sheet conveying direction D1.

[0109] One of the rear through-holes 630h-3 can be called the first hole or first through-hole, and one of the front through-holes 630h-2 can be called the second hole or second through-hole. For example, as shown by the dashed line in Figure 14, when viewed in the sheet transport direction D1, the rear through-hole 630h-3 (first hole, first through-hole) and the front through-hole 630h-2 (second hole, second through-hole) may overlap. In other words, the longitudinal position of the through-hole 630h opening on the front surface 630a of the lower frame 63 may be aligned with the longitudinal position of the through-hole 630h opening on the rear surface 630c of the lower frame 63. This allows air to flow more smoothly along the outer surface of the pressure roller 62.

[0110] On the other hand, when viewed in the sheet transport direction D1, the rear through-hole 630h-3 (first hole, first through-hole) and the front through-hole 630h-2 (second hole, second through-hole) may not overlap. In other words, the longitudinal position of the through-hole 630h opening on the front surface 630a of the lower frame 63 and the longitudinal position of the through-hole 630h opening on the rear surface 630c of the lower frame 63 may be different from each other. This makes it easier to evenly expel water vapor from the space between the lower frame 63 and the outer surface of the pressure roller 62.

[0111] Figure 16 shows a lower frame 63 relating to another modification (modification 3), viewed from the upstream side in the sheet conveying direction D1. In modification 3, instead of forming through holes 630h in the lower frame 63, grooves 630i are formed on the edge of the lower frame 63 that penetrate from the base surface 630d to the outside. In the example shown in Figure 16, one or more grooves 630i are formed that penetrate from the base surface 630d to the front surface 630a of the lower frame 63. The grooves 630i have a concave shape, with a part of the upper edge of the front surface 630a recessed downwards. The grooves 630i penetrate from the base surface 630d to the outside of the lower frame 63 in the opposite direction to the sheet conveying direction D1. In the illustrated example, six grooves 630i are arranged in the longitudinal direction, but the number of grooves 630i can be changed. One of the six grooves 630i can be called the first groove, and the other one of the six grooves 630i can be called the second groove.

[0112] The groove 630i may be formed on the rear surface 630c of the lower frame 63, as shown by the dashed line in Figure 15. This groove 630i has a concave shape in which a part of the upper edge of the rear surface 630c is recessed downwards, and is formed to penetrate from the base surface 630d of the lower frame 63 to the rear surface 630c. In other words, this groove 630i penetrates from the base surface 630d to the outside of the lower frame 63 in the sheet conveying direction D1.

[0113] When the groove 630i-1 on the rear surface 630c is called the first groove, the groove 630i-2 on the front surface 630a can be called the second groove. As shown in the single groove 630i-2 on the left side of Figure 15, the groove 630i-1 on the rear surface 630c and the groove 630i-2 on the front surface 630a may overlap when viewed in the sheet transport direction D1. Alternatively, as shown in the single groove 630i-2 on the right side of Figure 15, the groove 630i-1 on the rear surface 630c and the groove 630i-2 on the front surface 630a may not overlap when viewed in the sheet transport direction D1.

[0114] In each of the above modifications, providing through holes or grooves in the lower frame 63 prevents water vapor-containing air from accumulating between the lower frame 63 and the pressure roller 62. This also prevents condensation on the pressure roller 62 even in environments where the sheet S contains a lot of moisture, such as high temperature and high humidity environments. Furthermore, providing through holes or grooves in the front surface 630a or rear surface 630c has the advantage of making it easier for water vapor to escape due to the airflow generated by the sheet S as it passes through the fuser 6.

[0115] The number, arrangement, and shape of the through holes or grooves formed in the lower frame 63 are not limited to those shown in Figures 13 to 16; for example, rectangular through holes or grooves may be used. Furthermore, the through holes or grooves described in Example 4 and Modifications 1 to 3 may be combined. For example, through holes may be formed in both the front surface 630a and the rear surface 630c of the lower frame 63. [Examples]

[0116] Embodiment 5 of this disclosure is described below. Embodiments 1 to 4 described through holes and grooves that serve to release water vapor generated from the sheet S, but this embodiment differs from Embodiments 1 to 4 in that through holes and grooves for arranging sensors (temperature detection units) related to the fuser 6 are provided in the lower frame 63. In the following, elements with reference numerals common to Embodiment 1 are assumed to have basically the same configuration and function as those described in Embodiment 1 unless otherwise specified, and the parts that differ from Embodiment 1 will be described mainly.

[0117] In this embodiment, a thermistor 618 facing the pressure roller 62 is used as an example of a temperature detection unit. Figure 17 is a schematic perspective view showing the lower frame 63 according to this embodiment. Figure 18 is a cross-sectional view of the lower frame 63, pressure roller 62 and thermistor 618 in a virtual plane perpendicular to the longitudinal direction (Y direction).

[0118] As shown in Figures 17 and 18, the fuser 6 of this embodiment includes a contact-type thermistor 618. The thermistor 618 is positioned inside the lower frame 63 so as to be in contact with the outer surface of the pressure roller 62 (Figure 18), and outputs a signal (e.g., voltage) corresponding to the temperature of the pressure roller 62. The thermistor 618 may be, for example, a thin-film thermistor.

[0119] The control unit of the image forming apparatus 1 acquires temperature information of the pressure roller 62 based on the signal from the thermistor 618 and controls the temperature of the pressure roller 62 by controlling the heat generation of the heater 611 (Figure 3) of the fuser 6. By appropriately controlling the temperature of the pressure roller 62, it is possible to improve the productivity of the image forming apparatus 1, improve fixing performance, and improve image quality.

[0120] Note that the thermistor 618 is just one example of a temperature detection unit; a temperature detection unit including other heat-sensitive elements such as thermocouples or platinum resistance thermometers may also be used. Furthermore, a non-contact type temperature detection unit (non-contact sensor) may be used, as shown in the modified example described later.

[0121] As shown in Figures 17 and 18, the lower frame 63 of this embodiment has a through hole 805 (sensor mounting hole) and a groove 806 for arranging the thermistor 618. The through hole 805 penetrates from the base surface 630d of the lower frame 63 to the outside of the lower frame 63. In the illustrated example, the through hole 805 opens to the rear surface 630c, but the through hole 805 may also open to the front surface 630a or the bottom surface 630b.

[0122] The groove 806 is a groove shape (recess, notch) formed in the reinforcing rib 80 of the lower frame 63. In this embodiment, the groove 806 is formed in the longitudinal rib 803. The groove 806 is a concave shape in which a part of the tip 803a of the longitudinal rib 803 (intersecting rib) that extends longitudinally to connect adjacent transport direction ribs 801 (first rib, second rib) in the longitudinal direction is recessed. When viewed in the direction in which the longitudinal rib 803 extends toward the lower frame 63 (intersecting direction D2), the thermistor 618 (temperature detection part) has a portion that overlaps with the groove 806.

[0123] The thermistor 618 is positioned to penetrate the through-hole 630h and face the outer circumferential surface of the pressure roller 62. The thermistor 618 has a head portion 618a that contacts the outer circumferential surface of the pressure roller 62, a base portion 618c supported by the lower frame 63, and a connecting portion 618b that connects the head portion 618a and the base portion 618c. The head portion 618a includes a heat-sensitive element whose resistance changes according to temperature, such as an NTC type semiconductor element. The base portion 618c includes a connector that is connected to wiring for electrical connection to the control unit of the image forming apparatus 1, for example. The connecting portion 618b has a conductor that electrically connects the base portion 618c and the heat-sensitive element of the head portion 618a, and supports the head portion 618a.

[0124] By forming a through-hole 805 in the lower frame 63, the thermistor 618 can be positioned facing the outer surface of the pressure roller 62. Furthermore, the through-hole 805 allows the thermistor 618 to be connected to wiring that passes outside the lower frame 63.

[0125] Furthermore, by forming grooves 806 in the reinforcing ribs 80 (longitudinal ribs 803) of the lower frame 63, it becomes easier to achieve an arrangement in which the head portion 618a contacts the outer circumferential surface of the pressure roller 62. If grooves 806 are not provided, there may be insufficient space to position the thermistor 618, making it difficult to install the thermistor 618 and potentially reducing work efficiency during assembly, or causing problems such as strong contact between the head portion 618a and the pressure roller 62.

[0126] Figure 18 illustrates a contact-type thermistor 618, but as shown in Figure 19, a non-contact type thermistor 618' may be used as a non-contact temperature detection unit. The non-contact type thermistor 618' is positioned so that its head portion 618a' does not come into contact with the outer surface of the pressure roller 62. The non-contact type thermistor 618' outputs a signal corresponding to the temperature of the pressure roller 62 by detecting thermal radiation (infrared radiation) from the pressure roller 62. Even in this case, the non-contact type thermistor 618' can be positioned by forming a through hole 805 in the lower frame 63 and a groove portion 806 in the reinforcing rib 80.

[0127] Note that the non-contact thermistor 618' is just one example of a non-contact temperature detection unit, and other non-contact temperature detection units using different detection methods may also be used.

[0128] Figure 20(a) is a schematic cross-sectional view showing the positional relationship between the longitudinal rib 803 and the thermistor 618 in a plane perpendicular to the sheet conveying direction D1 and including the longitudinal rib 803. In the cross-section shown in Figure 20(a), at least a portion of the thermistor 618 (temperature sensing portion) is located inside the groove 806. That is, when viewed in the sheet conveying direction D1, at least a portion of the thermistor 618 penetrates inside the groove 806 compared to the tip 803a (ridge portion) of the longitudinal rib 803. Specifically, when viewed in the intersecting direction D2, the portion of the thermistor 618 that overlaps with the groove 806 is located inside the groove 806. This configuration makes it easier to position the thermistor 618.

[0129] Furthermore, Figure 20(a) can be described as a view of the outer surface of the pressure roller 62 in the tangential direction at a position opposite the head portion 618a of the thermistor 618. Therefore, in this embodiment, when viewed tangentially to the outer surface of the pressure roller 62, at least a portion of the thermistor 618 is located on the side (lower side in the figure) further from the pressure roller 62 than the tip 803a of the longitudinal rib 803.

[0130] Figure 20(b) is a schematic cross-sectional view showing other positional relationships between the longitudinal rib 803 and the thermistor 618. In the cross-section shown in Figure 20(b), the entire thermistor 618 is located outside the groove 806. In other words, when viewed in the sheet conveying direction D1, the entire thermistor 618 is located closer to the pressure roller 62 (upper side in the figure) than the tip 803a (ridge) of the longitudinal rib 803.

[0131] In the example shown in Figure 20(b), by providing the groove 806 in the longitudinal rib 803, interference between the thermistor 618 and the longitudinal rib 803 due to tolerances in the dimensions of the thermistor 618 or the lower frame 63, or assembly tolerances, can be avoided. Therefore, even in the example shown in Figure 20(b), the thermistor 618 for detecting the temperature of the pressure roller 62 can be positioned more easily.

[0132] (modified version) In Example 5, an example was described in which the thermistor 618 for detecting the temperature of the pressure roller 62 is placed in only one location, but the thermistor 618 may be placed in multiple locations. For example, an additional thermistor may be placed to detect the temperature of the end of the pressure roller 62 in the longitudinal direction. In this case, the control unit of the image forming apparatus 1 can monitor the temperature of the end of the pressure roller 62.

[0133] Here, when image formation is performed on recording material whose longitudinal width is shorter than the heating range of heater 611, the phenomenon in which the temperature of the pressure roller 62 (and belt 614) rises in the region where the recording material does not pass in the longitudinal direction is called non-paper-passing area heating. Non-paper-passing area heating can cause damage or deterioration of components due to high temperatures, and may also cause image defects when image formation is performed on wider recording material later. If an additional thermistor is not used, when image formation is performed on a narrow recording material, it may be necessary to reduce the throughput to avoid the negative effects of non-paper-passing area heating. On the other hand, by monitoring the temperature of the end of the pressure roller 62 using an additional thermistor, it becomes possible to perform image formation at a high throughput while avoiding the negative effects of non-paper-passing area heating. Therefore, by placing an additional thermistor 618 at the end of the pressure roller 62, the productivity of the image forming apparatus 1 can be improved.

[0134] When arranging multiple temperature sensing elements in this manner, through holes 805 and grooves 806 corresponding to each of the multiple temperature sensing elements may be formed in the lower frame 63. This makes it easier to arrange contact-type temperature sensing elements that contact the outer surface of the pressure roller 62, or non-contact-type temperature sensing elements that are placed near the pressure roller 62.

[0135] Summary of this disclosure This disclosure includes at least the following configurations or methods: Summary of this disclosure This disclosure includes at least the following: (Composition 1) A fixing device for fixing an image onto a recording material, An endless belt, A heater for heating the inner surface of the belt, A pressure roller including a rubber roller portion that forms a nip portion for transporting the recording material in the transport direction together with the heater via the belt, A resin frame that rotatably supports the pressure roller and faces the roller portion in the longitudinal direction of the pressure roller, Equipped with, The frame comprises a base surface facing the outer circumferential surface of the roller portion in the longitudinal direction, and having a first rib and a second rib extending in an intersecting direction that intersects both the conveying direction and the longitudinal direction. Viewed in the longitudinal direction, the shape of the tip of the first rib and the shape of the tip of the second rib are arc-shaped, following the outer surface of the roller portion. In the longitudinal direction, the first rib and the second rib are aligned, The first rib is formed with the first shape, A second shape is formed on the second rib. The first shape is a first through-hole that penetrates the first rib in the longitudinal direction or a first groove formed in a part of the arc shape of the first rib. The fixing device is characterized in that the second shape is a second through hole that penetrates the second rib in the longitudinal direction or a second groove formed in a part of the arc shape of the second rib. (Configuration 2) The end of the base surface in the longitudinal direction on one side is defined as the first end, and the end on the other side is defined as the second end. In the longitudinal direction, the first rib is closer to the first end than the second end. In the longitudinal direction, the second rib is closer to the second end than the first end. The fixing device according to configuration 1, characterized by the above. (Composition 3) In the longitudinal direction, the first rib and the second rib face each other. The fixing device according to configuration 1 or 2, characterized in that, when viewed in the longitudinal direction, the first shape overlaps the second shape. (Composition 4) In the longitudinal direction, the first rib and the second rib face each other. The fixing device according to configuration 1 or 2, characterized in that, when viewed in the longitudinal direction, the first shape does not overlap with the second shape. (Composition 5) A first intersecting rib extending in the longitudinal direction connects the first rib and the second rib, A fixing device according to any one of configurations 1 to 4, characterized in that it comprises a second crossing rib extending in the longitudinal direction so as to connect the first rib and the second rib, and the second crossing rib facing the first crossing rib in the conveying direction. (Composition 6) The portion where the first rib and the first intersecting rib intersect is called the intersection, The fixing device according to configuration 5, characterized in that the tip of the intersection in the aforementioned intersection direction is recessed from the tip of the first intersection rib in the aforementioned intersection direction. (Composition 7) The fixing device according to any one of configurations 1 to 6, characterized in that the frame has a first hole and a second hole that penetrate from the base surface to the outside of the frame. (Composition 8) The first hole penetrates from the base surface to the outside of the frame in the direction of transport, The fixing device according to configuration 7, characterized in that the second hole penetrates from the base surface to the outside of the frame in the direction opposite to the conveying direction. (Composition 9) The fixing device according to configuration 8, characterized in that the first hole and the second hole overlap when viewed in the transport direction. (Composition 10) The fixing device according to configuration 7, characterized in that the first hole and the second hole are aligned in the longitudinal direction. (Composition 11) A fixing device according to any one of configurations 1 to 10, characterized in that it comprises a first groove and a second groove that penetrate from the base surface to the outside of the frame when viewed in the transport direction. (Composition 12) The first groove penetrates from the base surface to the outside of the frame in the direction of transport, The fixing device according to configuration 11, characterized in that the second groove penetrates from the base surface to the outside of the frame in the direction opposite to the conveying direction. (Composition 13) The fixing device according to configuration 12, characterized in that the first groove and the second groove overlap when viewed in the conveying direction. (Composition 14) The fixing device according to configuration 11, characterized in that the first groove and the second groove are aligned in the longitudinal direction. (Composition 15) A fixing device for fixing an image onto a recording material, An endless belt, A heater for heating the inner surface of the belt, A pressure roller including a roller portion that forms a nip portion for conveying the recording material in the conveying direction together with the heater via the belt, A resin frame that rotatably supports the pressure roller and faces the roller portion in the longitudinal direction of the pressure roller, Equipped with, The frame comprises a base surface facing the outer circumferential surface of the roller portion in the longitudinal direction, and having a first rib and a second rib extending in an intersecting direction that intersects both the conveying direction and the longitudinal direction. Viewed in the longitudinal direction, the shape of the tip of the first rib and the shape of the tip of the second rib are arc-shaped, following the outer surface of the roller portion. In the longitudinal direction, the first rib and the second rib are aligned, The base surface includes a first crossing rib having a first shape and a second crossing rib having a second shape. The first intersecting rib and the second intersecting rib are located between the first rib and the second rib in the longitudinal direction and extend in the longitudinal direction and the intersecting direction. The first crossing rib and the second crossing rib are located in different positions in the conveying direction. The first shape is a first through hole that penetrates the first intersecting rib in the conveying direction, or a groove formed at the tip of the first intersecting rib in the direction of intersection. The fixing device is characterized in that the second shape is a second through-hole that penetrates the second intersecting rib in the conveying direction or a groove formed at the tip of the second intersecting rib in the intersecting direction. (Composition 16) The base surface is defined as having one end in the conveying direction as the first end and the other end as the second end. In the aforementioned conveying direction, the first intersecting rib is closer to the first end than the second end. In the aforementioned conveying direction, the second crossing rib is closer to the second end than the first end. The fixing device according to configuration 15, characterized by the features described above. (Composition 17) In the aforementioned conveying direction, the first crossing rib and the second crossing rib face each other. The fixing device according to configuration 15 or 16, characterized in that, when viewed in the conveying direction, the first shape overlaps the second shape. (Composition 18) In the aforementioned conveying direction, the first crossing rib and the second crossing rib face each other. The fixing device according to configuration 15 or 16, characterized in that, when viewed in the conveying direction, the first shape does not overlap with the second shape. (Composition 19) A fixing device for fixing an image onto a recording material, An endless belt, A heater for heating the inner surface of the belt, A pressure roller including a roller portion that forms a nip portion for conveying the recording material in the conveying direction together with the heater via the belt, A resin frame that rotatably supports the pressure roller and faces the roller portion in the longitudinal direction of the pressure roller, Equipped with, The frame comprises a base surface facing the roller portion in an intersecting direction that intersects the transport direction and the longitudinal direction, and the base surface includes a first rib and a second rib extending in the intersecting direction. Viewed in the longitudinal direction, the shape of the tip of the first rib and the shape of the tip of the second rib are arc-shaped, following the outer surface of the roller portion. In the longitudinal direction, the first rib and the second rib are aligned, The frame is provided with a first through hole and a second through hole, The fixing device is characterized in that the first through hole and the second through hole are formed in the base surface in a position that does not include the first rib and the second rib, and penetrate from the base surface to the outside of the frame. (Composition 20) The fixing device according to configuration 19, characterized in that the first through-hole and the second through-hole overlap when viewed in the aforementioned transport direction. (Composition 21) The fixing device according to configuration 19, characterized in that the first through-hole and the second through-hole do not overlap when viewed in the aforementioned transport direction. (Composition 22) The fixing device according to configuration 19, characterized in that the first through hole and the second through hole are aligned in the longitudinal direction. (Composition 23) A fixing device for fixing an image onto a recording material, An endless belt, A heater for heating the inner surface of the belt, A pressure roller including a roller portion that forms a nip portion for conveying the recording material in the conveying direction together with the heater via the belt, A resin frame that rotatably supports the pressure roller and faces the roller portion in the longitudinal direction of the pressure roller, Equipped with, The frame comprises a base surface facing the roller portion in an intersecting direction that intersects the transport direction and the longitudinal direction, and the base surface includes a first rib and a second rib extending in the intersecting direction. Viewed in the longitudinal direction, the shape of the tip of the first rib and the shape of the tip of the second rib are arc-shaped, following the outer surface of the roller portion. In the longitudinal direction, the first rib and the second rib are aligned, The frame has a through hole that extends from the base surface to the outside of the frame, and is located between the first rib and the second rib. A fixing device characterized by comprising a temperature detection unit that penetrates the through hole and is positioned opposite the pressure roller. (Composition 24) The fixing device according to configuration 23, characterized in that the temperature detection unit is arranged to be in contact with the pressure roller. (Composition 25) The fixing device according to configuration 23, characterized in that the temperature detection unit is a non-contact sensor positioned so as not to come into contact with the pressure roller. (Composition 26) The frame comprises intersecting ribs extending in the longitudinal direction so as to connect the first rib and the second rib, the intersecting ribs having grooves formed at their tips. The fixing device according to any one of configurations 23 to 25, characterized in that when the intersecting ribs are viewed in the direction extending toward the frame, the temperature detection unit has a portion that overlaps with the groove. (Composition 27) The fixing device according to configuration 26, characterized in that the portion is located inside the groove. [Explanation of Symbols]

[0136] 62…Pressure roller, 63…Frame (lower frame), 611…Heater, 614…Belt, 618…Temperature detection unit (thermistor), 630h…First through hole, Second through hole, 801-1…First rib (conveying direction rib), 801-2…Second rib (conveying direction rib), 801b…First shape, Second shape (groove), 801c…First shape, Second shape (through hole), 802…Intersection, 803-1…Intersecting rib, First intersecting rib (longitudinal direction rib), 803-2…Intersecting rib, Second intersecting rib (longitudinal direction rib), 803b…First shape, Second shape (groove), 803c…First shape, Second shape (through hole)

Claims

1. A fixing device for fixing an image onto a recording material, An endless belt, A heater for heating the inner surface of the belt, A pressure roller including a rubber roller portion that forms a nip portion for transporting the recording material in the transport direction together with the heater via the belt, A resin frame that rotatably supports the pressure roller and faces the roller portion in the longitudinal direction of the pressure roller, Equipped with, The frame comprises a base surface facing the outer circumferential surface of the roller portion in the longitudinal direction, and having a first rib and a second rib extending in an intersecting direction that intersects both the conveying direction and the longitudinal direction. Viewed in the longitudinal direction, the shape of the tip of the first rib and the shape of the tip of the second rib are arc-shaped, following the outer surface of the roller portion. In the longitudinal direction, the first rib and the second rib are aligned, The first rib is formed with the first shape, A second shape is formed on the second rib. The first shape is a first through-hole that penetrates the first rib in the longitudinal direction or a first groove formed in a part of the arc shape of the first rib. The fixing device is characterized in that the second shape is a second through hole that penetrates the second rib in the longitudinal direction or a second groove formed in a part of the arc shape of the second rib.

2. The end of the base surface in the longitudinal direction on one side is defined as the first end, and the end on the other side is defined as the second end. In the longitudinal direction, the first rib is closer to the first end than the second end. In the longitudinal direction, the second rib is closer to the second end than the first end. The fixing device according to feature 1.

3. In the longitudinal direction, the first rib and the second rib face each other. The fixing device according to claim 1, characterized in that, when viewed in the longitudinal direction, the first shape overlaps the second shape.

4. In the longitudinal direction, the first rib and the second rib face each other. The fixing device according to claim 1, characterized in that, when viewed in the longitudinal direction, the first shape does not overlap with the second shape.

5. A first intersecting rib extending in the longitudinal direction connects the first rib and the second rib, The fixing device according to claim 1, further comprising a second crossing rib extending in the longitudinal direction so as to connect the first rib and the second rib, the second crossing rib facing the first crossing rib in the conveying direction.

6. The portion where the first rib and the first intersecting rib intersect is called the intersection, The fixing device according to claim 5, characterized in that the tip of the intersection in the aforementioned intersection direction is recessed from the tip of the first intersection rib in the aforementioned intersection direction.

7. The fixing device according to claim 1, characterized in that the frame has a first hole and a second hole that penetrate from the base surface to the outside of the frame.

8. The first hole penetrates from the base surface to the outside of the frame in the direction of transport, The fixing device according to claim 7, characterized in that the second hole penetrates from the base surface to the outside of the frame in the direction opposite to the conveying direction.

9. The fixing device according to claim 8, characterized in that the first hole and the second hole overlap when viewed in the aforementioned transport direction.

10. The fixing device according to claim 7, characterized in that the first hole and the second hole are aligned in the longitudinal direction.

11. The fixing device according to claim 1, characterized in that it comprises a first groove and a second groove that penetrate from the base surface to the outside of the frame when viewed in the transport direction.

12. The first groove penetrates from the base surface to the outside of the frame in the direction of transport, The fixing device according to claim 11, characterized in that the second groove penetrates from the base surface to the outside of the frame in the direction opposite to the conveying direction.

13. The fixing device according to claim 12, characterized in that the first groove and the second groove overlap when viewed in the conveying direction.

14. The fixing device according to claim 11, characterized in that the first groove and the second groove are aligned in the longitudinal direction.

15. A fixing device for fixing an image onto a recording material, An endless belt, A heater for heating the inner surface of the belt, A pressure roller including a roller portion that forms a nip portion for conveying the recording material in the conveying direction together with the heater via the belt, A resin frame that rotatably supports the pressure roller and faces the roller portion in the longitudinal direction of the pressure roller, Equipped with, The frame comprises a base surface facing the outer circumferential surface of the roller portion in the longitudinal direction, and having a first rib and a second rib extending in an intersecting direction that intersects both the conveying direction and the longitudinal direction. Viewed in the longitudinal direction, the shape of the tip of the first rib and the shape of the tip of the second rib are arc-shaped, following the outer surface of the roller portion. In the longitudinal direction, the first rib and the second rib are aligned, The base surface includes a first crossing rib having a first shape and a second crossing rib having a second shape. The first intersecting rib and the second intersecting rib are located between the first rib and the second rib in the longitudinal direction and extend in the longitudinal direction and the intersecting direction. The first crossing rib and the second crossing rib are located in different positions in the conveying direction. The first shape is a first through hole that penetrates the first intersecting rib in the conveying direction, or a groove formed at the tip of the first intersecting rib in the direction of intersection. The fixing device is characterized in that the second shape is a second through-hole that penetrates the second intersecting rib in the conveying direction or a groove formed at the tip of the second intersecting rib in the intersecting direction.

16. The base surface is defined as having one end in the conveying direction as the first end and the other end as the second end. In the aforementioned conveying direction, the first intersecting rib is closer to the first end than the second end. In the aforementioned conveying direction, the second crossing rib is closer to the second end than the first end. The fixing device according to claim 15.

17. In the aforementioned conveying direction, the first crossing rib and the second crossing rib face each other. The fixing device according to claim 15, characterized in that, when viewed in the transport direction, the first shape overlaps the second shape.

18. In the aforementioned conveying direction, the first crossing rib and the second crossing rib face each other. The fixing device according to claim 15, characterized in that, when viewed in the transport direction, the first shape does not overlap with the second shape.

19. A fixing device for fixing an image onto a recording material, An endless belt, A heater for heating the inner surface of the belt, A pressure roller including a roller portion that forms a nip portion for conveying the recording material in the conveying direction together with the heater via the belt, A resin frame that rotatably supports the pressure roller and faces the roller portion in the longitudinal direction of the pressure roller, Equipped with, The frame comprises a base surface facing the roller portion in an intersecting direction that intersects the transport direction and the longitudinal direction, and the base surface includes a first rib and a second rib extending in the intersecting direction. Viewed in the longitudinal direction, the shape of the tip of the first rib and the shape of the tip of the second rib are arc-shaped, following the outer surface of the roller portion. In the longitudinal direction, the first rib and the second rib are aligned, The frame is provided with a first through hole and a second through hole, The fixing device is characterized in that the first through hole and the second through hole are formed in the base surface in a position that does not include the first rib and the second rib, and penetrate from the base surface to the outside of the frame.

20. The fixing device according to claim 19, characterized in that the first through-hole and the second through-hole overlap when viewed in the transport direction.

21. The fixing device according to claim 19, characterized in that the first through-hole and the second through-hole do not overlap when viewed in the transport direction.

22. The fixing device according to claim 19, characterized in that the first through hole and the second through hole are aligned in the longitudinal direction.

23. A fixing device for fixing an image onto a recording material, An endless belt, A heater for heating the inner surface of the belt, A pressure roller including a roller portion that forms a nip portion for conveying the recording material in the conveying direction together with the heater via the belt, A resin frame that rotatably supports the pressure roller and faces the roller portion in the longitudinal direction of the pressure roller, Equipped with, The frame comprises a base surface facing the roller portion in an intersecting direction that intersects the transport direction and the longitudinal direction, and the base surface includes a first rib and a second rib extending in the intersecting direction. Viewed in the longitudinal direction, the shape of the tip of the first rib and the shape of the tip of the second rib are arc-shaped, following the outer surface of the roller portion. In the longitudinal direction, the first rib and the second rib are aligned, The frame has a through hole that extends from the base surface to the outside of the frame, and is located between the first rib and the second rib. A fixing device characterized by comprising a temperature detection unit that penetrates the through hole and is positioned opposite the pressure roller.

24. The fixing device according to claim 23, characterized in that the temperature detection unit is arranged to be in contact with the pressure roller.

25. The fixing device according to claim 23, characterized in that the temperature detection unit is a non-contact sensor positioned so as not to come into contact with the pressure roller.

26. The frame comprises intersecting ribs extending in the longitudinal direction so as to connect the first rib and the second rib, the intersecting ribs having grooves formed at their tips. The fixing device according to claim 23, characterized in that when the intersecting ribs are viewed in the direction extending toward the frame, the temperature detection unit has a portion that overlaps with the groove.

27. The fixing device according to claim 26, characterized in that the portion is located inside the groove.

Images