JP7790190B2 - Fixing device - Google Patents

Description

The present invention relates to a fixing device equipped with an endless belt.

Conventionally, some fixing devices using a pressure pad have a sliding sheet between the endless belt and the pressure pad (see Patent Document 1). Lubricating oil is held between the sliding sheet and the endless belt. The sliding sheet has recesses for holding the lubricant.

Japanese Patent Application Laid-Open No. 2009-015227

When the endless belt moves, the lubricant also moves in the width direction of the sliding sheet. However, the configuration in Patent Document 1 was unable to move the lubricant in a specific direction.

The present invention aims to move the lubricating oil placed between the endless belt and the sliding sheet in a specific direction.

In order to solve the above problem, the fixing device of the present invention comprises a rotating body, an endless belt in contact with the outer peripheral surface of the rotating body, a heater that heats at least one of the rotating body and the endless belt, a pressure member that sandwiches the endless belt between the rotating body and the pressure member, a sliding sheet that is sandwiched between the inner peripheral surface of the endless belt and the pressure member, and a lubricant that is arranged between the endless belt and the sliding sheet.
The surface of the sliding sheet facing the inner circumferential surface of the endless belt has a rib-shaped convex portion that is convex toward the endless belt and a concave portion that is concave relative to the convex portion.
The protrusion includes a first rib extending in a first extension direction that is oblique to the moving direction of the endless belt;
and a second rib extending in a second extension direction intersecting the first extension direction and connected to the first rib.
The first rib has a side surface facing the second extension direction exposed at a portion where the second rib is connected to the first rib.

With this configuration, when the endless belt moves in the travel direction, the lubricant moves along the side of the first rib in the first extension direction, allowing the lubricant to move in a specific direction.

Furthermore, in the fixing device described above, the angle between the movement direction of the endless belt and the first extension direction may be configured to be equal to the angle between the movement direction of the endless belt and the second extension direction.

This reduces the frictional force of the first rib against the endless belt and the frictional force of the second rib, preventing the endless belt from becoming misaligned.

Furthermore, in the fixing device described above, the first rib and the second rib may be configured to extend linearly.

This allows the entire first rib to function to move the lubricant in a specific direction.

Furthermore, in the fixing device described above, the first rib and the second rib may be configured to intersect at right angles.

Furthermore, in the fixing device described above, the top of the first rib may be higher than the top of the second rib, and at the portion where the second rib connects to the first rib, the side surface may protrude further toward the endless belt than the top of the second rib.

This allows the lubricating oil to move easily along the first rib.

Furthermore, in the fixing device described above, the opposing surface of the sliding sheet may be configured to have a groove located between the first and second ribs at the portion where the second rib connects to the first rib, extending in the first extension direction and crossing the second rib.

This allows the lubricant to move along the grooves.

Furthermore, in the fixing device described above, the first rib may extend from one side of the endless belt widthwise to the other side as it moves downstream in the direction of movement of the endless belt, and may further include a temperature sensor that detects the temperature of the end of the rotating body on the other side in the widthwise direction of the endless belt.

This allows the lubricant temperature to be measured properly by moving the lubricant to the side where the temperature is detected.

Furthermore, in the fixing device described above, the first rib may be configured to extend continuously from one end to the other end in the width direction.

Furthermore, in the fixing device described above, the first rib may extend from one end to the center of the sliding sheet in the width direction of the endless belt, and the convex portion may further include a third rib extending in the second extension direction from the other end in the width direction to the center of the sliding sheet in the width direction, and a fourth rib extending in the first extension direction and connected to the third rib, and the third rib may be configured so that the side surface facing the first extension direction is exposed at the portion where the fourth rib connects to the third rib.

This keeps the lubricant concentrated in the center, preventing it from leaking out from the edges.

According to the present invention, the lubricating oil placed between the endless belt and the sliding sheet can be moved in a specific direction.

1 is a cross-sectional view showing a laser printer according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view showing the fixing device. FIG. 3 is an enlarged view of a portion of the endless belt and the sliding sheet in FIG. 2 . 1A is an enlarged perspective view showing the opposing surface of the sliding sheet, and FIG. 1B is a cross-sectional view taken along the line AA. 3A is a cross-sectional view taken along the line XX in FIG. 2, and FIG. 3B is a plan view of the opposing surface of the sliding sheet. 10A and 10B are diagrams illustrating a method for attaching a thermostat to a heating unit. 7 is a cross-sectional view taken along the line YY in FIG. 6. 10A is a perspective view showing a sliding sheet of a second embodiment, and FIG. 10B is a cross-sectional view taken along the line BB. 10A is a perspective view showing a sliding sheet of a third embodiment, and FIG. 10B is a cross-sectional view taken along the line CC. 10A is a perspective view showing a sliding sheet of a fourth embodiment, and FIG. 10B is a cross-sectional view taken along the line DD. 10A is a perspective view showing a sliding sheet according to a fifth embodiment, and FIG. 10B is a perspective view showing a sliding sheet according to a sixth embodiment. FIG. 13 is a plan view showing a sliding sheet according to a seventh embodiment.

Hereinafter, a first embodiment of the invention will be described in detail with reference to the drawings as appropriate.
1, a fixing device 8 according to the embodiment is used in an image forming apparatus 1 such as a laser printer. The image forming apparatus 1 includes a main body 2, a sheet supply unit 3, an exposure device 4, a developer image forming unit 5, and the fixing device 8.

The sheet supply unit 3 is located at the bottom of the main body housing 2 and includes a sheet tray 31 that stores sheets S such as paper, and a sheet supply mechanism 32. The sheets S in the sheet tray 31 are supplied to the developer image forming unit 5 by the sheet supply mechanism 32.

The exposure device 4 is located at the top of the main body housing 2 and includes a light source device (not shown), a polygon mirror (shown without reference numerals), a lens, a reflecting mirror, etc. The exposure device 4 exposes the surface of the photosensitive drum 61 by scanning a light beam (see dashed line) based on image data emitted from the light source device over the surface of the photosensitive drum 61 at high speed.

The developer image forming unit 5 is located below the exposure device 4. The developer image forming unit 5 is configured as a process cartridge, and is detachable from the main body casing 2 through an opening created when the front cover 21 located at the front of the main body casing 2 is opened. The developer image forming unit 5 includes a photosensitive drum 61, a charger 62, a transfer roller 63, a developing roller 64, a supply roller 65, and a developer storage unit 66 that stores developer made of dry toner.

The developer image forming unit 5 uniformly charges the surface of the photosensitive drum 61 using the charger 62. The surface of the photosensitive drum 61 is then exposed to a light beam from the exposure device 4, forming an electrostatic latent image based on the image data on the surface. The developer image forming unit 5 also supplies the developer in the developer container 66 to the developing roller 64 via the supply roller 65.

The developer image forming unit 5 then supplies the developer on the developing roller 64 to the electrostatic latent image formed on the photosensitive drum 61. This makes the electrostatic latent image visible, and a developer image is formed on the photosensitive drum 61. The developer image forming unit 5 then transfers the developer image on the photosensitive drum 61 to the sheet S by transporting the sheet S supplied from the sheet supply unit 3 between the photosensitive drum 61 and the transfer roller 63.

The fixing device 8 is located behind the developer image forming unit 5. Details of the fixing device 8 will be described later. The fixing device 8 thermally fixes the developer image to the sheet S by passing the sheet S onto which the developer image has been transferred. The image forming apparatus 1 discharges the sheet S with the thermally fixed developer image onto the discharge tray 22 outside the main body casing 2 using the transport rollers 23 and discharge rollers 24.

As shown in FIG. 2, the fixing device 8 includes a heating unit 81 and a pressure unit 82. The pressure unit 82 is urged toward the heating unit 81 by a pressing mechanism (not shown). In the following description, the direction in which the pressure unit 82 is urged toward the heating unit 81 is referred to as the "predetermined direction." In this embodiment, the predetermined direction is a direction perpendicular to the width direction and movement direction (described later), and is the direction in which the heating unit 81 and pressure unit 82 face each other.

The heating unit 81 includes a heater 110 and a rotating body 120. The pressure unit 82 includes an endless belt 130, a pressure pad P as an example of a pressure member, a holder 140, a sliding sheet 150, an upstream belt guide 160, a downstream belt guide 170, a stay 180, and grease GR as an example of a lubricant. In the following description, the width direction of the endless belt 130 will be simply referred to as the "width direction." The width direction is the direction in which the rotation axis X1 of the rotating body 120 extends. The width direction is perpendicular to the specified direction.

The heater 110 heats at least one of the rotating body 120 and the endless belt 130. In this embodiment, the heater 110 is disposed inside the rotating body 120 and heats the rotating body 120.

The rotating body 120 is a cylindrical roller and has a base tube 121 and an elastic layer 122. The base tube 121 is a metal pipe. The elastic layer 122 is rotatable around a rotation axis X1. The rotating body 120 is driven to rotate by a motor (not shown) provided in the image forming apparatus 1. The elastic layer 122 is provided on the outer periphery of the base tube 121. In other words, the rotating body 120 has the elastic layer 122 on its surface. The elastic layer 122 is elastic.

The endless belt 130 is an endless belt made of metal or the like. The endless belt 130 has a width greater than the width of the largest sheet S transported by the image forming apparatus 1. The endless belt 130 contacts the outer peripheral surface of the rotating body 120. The endless belt 130 transports the sheet S by sandwiching it between itself and the rotating body 120. When the rotating body 120 rotates, the endless belt 130 rotates clockwise in FIG. 2 due to friction with the rotating body 120 or the sheet S.

The pressure pad P is a member that sandwiches the endless belt 130, sliding sheet 150, and sheet S between itself and the rotating body 120 to form the nip portion NP. In the following description, the movement direction of the endless belt 130 at the nip portion NP will be simply referred to as the "movement direction." In this embodiment, the movement direction is along the outer surface of the rotating body 120, but since this direction is roughly perpendicular to the predetermined direction and the width direction, it will be illustrated as a direction perpendicular to the predetermined direction and the width direction. The movement direction is the same as the conveyance direction of the sheet S at the nip portion NP.

The pressure pad P has a first pressure pad P1 and a second pressure pad P2. The second pressure pad P2 is located downstream of the first pressure pad P1 in the direction of movement. The second pressure pad P2 has a higher durometer hardness than the first pressure pad P1.

The holder 140 is a member that holds the pressure pad N.

The sliding sheet 150 is sandwiched between the inner circumferential surface 131 of the endless belt 130 and the pressure pad P. The sliding sheet 150 contacts the inner circumferential surface 131 of the endless belt 130. When the rotating body 120 rotates, the sliding sheet 150 is always in contact with the endless belt 130. In contrast, when the rotating body 120 rotates, each part of the inner circumferential surface of the endless belt 130 alternates between being in contact with the sliding sheet 150 and not being in contact with it.

The sliding sheet 150 is a sheet-like member. The sliding sheet 150 is made of, for example, heat-resistant resin. As shown in FIG. 3, the sliding sheet 150 has an opposing surface 151 that faces the inner circumferential surface 131 of the endless belt 130. As shown in FIG. 4(a), the opposing surface 151 has a convex portion 152 and a concave portion 153.

The convex portion 152 is a rib-shaped portion that convexly extends toward the endless belt 130. In this embodiment, the proportion of the area of the convex portion 152 on the opposing surface 151 to the specified area is 50% or less. The convex portion 152 is composed of multiple ribs extending in different directions. Specifically, the convex portion 152 has a first rib 152A and a second rib 152B.

The first rib 152A extends in a first extension direction that is oblique to the movement direction of the endless belt 130. The first rib 152A extends linearly. In this embodiment, the angle between the movement direction of the endless belt 130 and the first extension direction is 45°.

5(b), the first rib 152A extends continuously from an end 150A on one side in the width direction of the sliding sheet 150 to an end 150B on the other side of the sliding sheet 150. In other words, the first rib 152A extends from the end 150A on one side in the width direction of the endless belt 130 toward the end 150B on the other side as it moves downstream in the moving direction of the endless belt 130.
In FIG. 5(b), the first ribs 152A and the second ribs 152B are shown enlarged to make the drawing easier to see, so the actual number of first ribs 152A and second ribs 152B is significantly greater than in FIG. 5(b).

Returning to FIG. 4(a), the second rib 152B extends in a second extension direction that intersects with the first extension direction. The second rib 152B extends linearly. In this embodiment, the angle between the movement direction of the endless belt 130 and the second extension direction is 45°. That is, in this embodiment, the angle between the movement direction of the endless belt 130 and the first extension direction is equal to the angle between the movement direction of the endless belt 130 and the second extension direction. In other words, the second rib 152B extends in a direction perpendicular to the first rib 152A.

Here, the first rib 152A and the second rib 152B are each capable of contacting each other via grease GR (see Figure 3). If the portions of the first rib 152A and the second rib 152B that can contact the endless belt 130 are defined as their respective peaks, the peak of the first rib 152A is higher than the peak of the second rib 152B. In other words, the peak of the second rib 152B is located closer to the recess 153 than the peak of the first rib 152A. Therefore, the first rib 152A has a side surface 152C at the portion where the second rib 152B connects to the first rib 152A. The side surface 152C faces in the second extension direction and connects the peak of the first rib 152A to the peak of the second rib 152B. The side surface 152C protrudes toward the endless belt 130 beyond the peak of the second rib 152B.

The recess 153 is a portion recessed in a direction away from the endless belt 130. In other words, the recess 153 is a portion recessed relative to the protrusion 152. The recess 153 is surrounded by the first rib 152A and the second rib 152B. In this embodiment, the recess 153 is a quadrangular pyramid-shaped depression with the base as the apex.

In this embodiment, the difference in height between the top of the first rib 152A and the top of the second rib 152B is 0.1 to 0.01 times the depth of the recess 153.

Returning to Figure 2, the upstream belt guide 160 is a member that guides the movement of the endless belt 130 upstream of the nip portion NP in the conveying direction of the sheet S. The upstream belt guide 160 has a curved surface that allows the endless belt 130 to rotate smoothly.

The downstream belt guide 170 is a member that guides the movement of the endless belt 130 downstream of the nip portion NP in the conveying direction of the sheet S. The upstream belt guide 160 has a curved surface that allows the endless belt 130 to rotate smoothly.

The stay 180 is a member that supports the holder 140, the upstream belt guide 160, and the downstream belt guide 170. The stay 180 is made by pressing a metal plate.

As shown in Figure 3, grease GR is placed between the endless belt 130 and the sliding sheet 150. The grease GR is intended to reduce friction between the endless belt 130 and the sliding sheet 150. The grease GR is located on the inner surface 131 of the endless belt 130 and on the convex portions 152 and concave portions 153 of the sliding sheet 150.

Returning to Figure 2, the fixing device 8 further includes a first temperature sensor TS1, a second temperature sensor TS2, and a thermostat 190.

As shown in Figure 5(a), the first temperature sensor TS1 is a sensor that detects the temperature of the central portion of the heating unit 81 in the width direction. The first temperature sensor TS1 is located in the central portion in the width direction. More specifically, the first temperature sensor TS1 is slightly offset to one side in the width direction from the center of the heating unit 81 in the width direction, i.e., the conveying center FC. The first temperature sensor TS1 is a sensor that does not come into contact with the heating unit 81.

The second temperature sensor TS2 is an example of a temperature sensor that detects the temperature at the other end of the heating unit 81 in the width direction. The second temperature sensor TS2 is located at the other end in the width direction. The second temperature sensor TS2 is a contact-type sensor that comes into contact with the heating unit 81. The second temperature sensor TS2 is positioned outside the width of the largest sheet S transported by the image forming apparatus 1.

As shown in FIG. 6, thermostat 190 is a well-known disk-type thermostat, and has a cylindrical main body 190A and a flat terminal 190B. As shown in FIG. 7, thermostat 190 is attached to fixing frame 80 with a spacer SP made of a resin film sandwiched between them. Frame 80 is disposed opposite heating unit 81 and has a thermostat support portion 80A that supports thermostat 190 and a first temperature sensor support portion 80B that supports first temperature sensor TS2.

Main body 190A has a temperature detection surface 190M capable of detecting the temperature of endless belt 130. Temperature detection surface 190M is positioned opposite the outer circumferential surface of endless belt 130 with a predetermined gap (a gap large enough to detect temperature). In this case, the predetermined gap can be accurately determined by appropriately selecting the thickness and number of spacers. For example, when assembling fixing device 8, spacers SP1, SP2, and SP3 of different thicknesses can be prepared, and the type and number of spacers SP can be determined after measuring the gap between rotating body 120 and temperature detection surface 190M.

Terminal 190B is connected to a circuit that supplies power to heater 110. When main body 190A detects a temperature higher than a predetermined temperature, thermostat 190 cuts off the flow of electricity between main body 190A and terminal 190B, thereby cutting off the flow of electricity to heater 110. This prevents the temperature of fixing device 100 from rising excessively.

As described above, the following effects can be obtained in this embodiment.
The sliding sheet 150 in the fixing device 8 has a facing surface 151 that faces the inner circumferential surface 131 of the endless belt 130 and has a convex portion 152 and a concave portion 153. The convex portion 152 has a first rib 152A and a second rib 152B. The first rib 152A extends in a first extension direction that is oblique to the movement direction of the endless belt 130. The first rib 152A has an exposed side surface 152C facing the second extension direction at the portion where the second rib 152B connects to the first rib 152A. Therefore, when the endless belt 130 moves in the movement direction, the grease GR moves in the first extension direction along the side surface 152C of the first rib 152A, allowing the grease GR to move in a specific direction.

In addition, the angle between the movement direction of the endless belt 130 and the first extension direction is equal to the angle between the movement direction of the endless belt 130 and the second extension direction. This prevents the endless belt from becoming misaligned due to the frictional force of the first rib 152A and the frictional force of the second rib 152B against the endless belt 130.

Furthermore, the first rib 152A and the second rib 152B extend linearly. Therefore, the entire first rib 152A can function to move the grease GR in a specific direction, in this embodiment, from one side to the other in the width direction.

In addition, the top of the first rib 152A is higher than the top of the second rib 152B, and at the portion where the second rib 152B connects to the first rib 152A, the side surface 152C protrudes further toward the endless belt 130 than the top of the second rib 152B. This allows the grease GR to easily move along the first rib 152A.

The first rib 152A extends from one side of the endless belt 130 to the other side in the width direction as it moves downstream in the movement direction of the endless belt 130, and is equipped with a second temperature sensor TS2 that detects the temperature of the end of the rotating body 120 on the other side in the width direction. This allows the grease GR to move to the side where the temperature is detected (the other side in the width direction), allowing the temperature of the grease GR to be measured appropriately.

Next, a second embodiment will be described with reference to FIG.
In the first embodiment, the top of the first rib 152A is higher than the top of the second rib 152B (see Figures 4(a) and (b)), whereas in the sliding sheet 250 of the second embodiment, the top of the first rib 252A and the top of the second rib 252B are configured to be the same height.

As shown in FIG. 8 , similar to the first embodiment, the sliding sheet 250 of the second embodiment has an opposing surface 251 that has a convex portion 252 and a concave portion 253, and the convex portion 252 has a first rib 252A and a second rib 252B. In the second embodiment, the top of the first rib 252A and the top of the second rib 252B are at the same height. The opposing surface 251 of the sliding sheet 250 has a groove 252D located between the first rib 252A and the second rib 252B at the portion where the second rib 252B connects to the first rib 252A, extending in the first extension direction and crossing the second rib 252B. The side surface 252C of the first rib 252A that faces the second extension direction is exposed where the groove 252D is formed.

In the sliding sheet 250 of the second embodiment, the grease GR also moves in the first extension direction through the groove 252D, allowing the grease GR to move in a specific direction.

Next, a third embodiment will be described with reference to FIG.
The sliding sheet 350 of the third embodiment differs from the second embodiment in that it has a wall portion between the rib and the groove.

As shown in FIG. 9 , the opposing surface 351 of the sliding sheet 350 has a convex portion 352 and a concave portion 353, and the convex portion 352 has a first rib 352A, a second rib 352B, a groove 352D, and a wall portion 352E. The wall portion 352E extends continuously from the groove 352D toward the endless belt 130 and is a wall that protrudes further toward the endless belt 130 than the top of the first rib 352A. The side surface 352C of the first rib 352A facing the second extension direction is exposed in the portion where the groove 352D and the wall portion 352E are formed.

In the sliding sheet 350 of the third embodiment, the grease GR also moves in the first extension direction through the groove 352D and along the wall portion 352E, allowing the grease GR to move in a specific direction.

Next, a fourth embodiment will be described with reference to FIG.
10 , in addition to the configuration of the sliding sheet 150 of the first embodiment, the sliding sheet 450 of the fourth embodiment has a groove 452F in the first rib 152A. The groove 452F is provided at the top of the first rib 152A and extends in the first extension direction. The depth of the groove 452F is 0.1 to 0.01 times the depth of the recess 153.

In the sliding sheet 450 of the fourth embodiment, the grease GR can also be moved in a specific direction by entering the groove 452F.

Next, fifth and sixth embodiments will be described with reference to FIGS.
In the first embodiment, the opposing surface 151 of the sliding sheet 150 has a convex portion 152 consisting of multiple ribs and a square concave portion 153, but the concave portion is not limited to a square and may be a rectangle, a parallelogram, or a polygon other than a rectangle.

For example, as shown in FIG. 11(a), the opposing surface 551 of the sliding sheet 550 has a convex portion 552 consisting of multiple ribs and a hexagonal concave portion 553. The convex portion 552 has a first rib 552A and a second rib 552B. The first rib 552A has a zigzag shape and extends in the first extension direction while bending. The second rib 552B extends linearly in the second extension direction. The top of the first rib 552A is higher than the top of the second rib 552B. The first rib 552A has a side surface 552C at the portion where the second rib 552B connects to the first rib 552A. The side surface 552C faces the second extension direction and connects the top of the first rib 552A to the top of the second rib 552B. The side surface 552C protrudes from the top of the second rib 552B toward the endless belt 130.

For example, as shown in Figure 11(a), the opposing surface 651 of the sliding sheet 650 has a convex portion 652 made up of multiple ribs and a triangular concave portion 653. The convex portion 652 has a first rib 652A, a second rib 652B, and a third rib 652C.

The first rib 652A extends linearly in a first extension direction. The second rib 652B extends linearly in a second extension direction tilted 60 degrees from the first extension direction. The third rib 652C extends linearly in a third extension direction tilted 60 degrees from both the first extension direction and the second extension direction. The top of the first rib 652A is higher than the tops of the second rib 652B and the third rib 652C.

The first rib 652A has a side surface 652D where the second rib 652B connects to the first rib 652A. The side surface 652D faces in the second extension direction and connects the top of the first rib 652A to the top of the second rib 652B. The side surface 652D protrudes from the top of the second rib 652B toward the endless belt 130.

The first rib 652A has a side surface 652E where the third rib 652C connects to the first rib 652A. The side surface 652E faces the third extension direction and connects the top of the first rib 652A to the top of the third rib 652C. The side surface 652E protrudes from the top of the third rib 652C toward the endless belt 130.

The sliding sheets 550 and 650 in the fifth and sixth embodiments also allow the grease GR to move in a specific direction.

Next, we will explain the seventh embodiment with reference to Figure 12.

In the first embodiment, the first rib 152A extended continuously from the end 150A on one side of the sliding sheet 150 in the width direction to the end 150B on the other side (see FIG. 5(a)). However, in the sliding sheet 750 of the seventh embodiment, the first rib 752A extends from the end 750A on one side to the conveying center FC, which is an example of a central portion, which is different from the first embodiment.

As shown in FIG. 12, the opposing surface 751 of the sliding sheet 750 of the seventh embodiment has a convex portion 752 and a concave portion 753, and the convex portion 752 has a first rib 752A, a second rib 752B, a third rib 752C, and a fourth rib 752D.

The first rib 752A extends linearly in the first extension direction from one end 750A to the conveying center FC of the sliding sheet 750 in the width direction of the endless belt 130.

The second rib 752B extends linearly in the second extension direction from one end 750A to the conveyance center FC. The second rib 752B is connected to the first rib 752A.
The first rib 752A has an exposed side surface 752E facing the first extension direction at the portion where the second rib 752B connects to the first rib 752A.

The third rib 752C extends linearly in the second extension direction from the other end 750B to the conveying center FC.

The fourth rib 752D extends linearly in the first extension direction from the other end 750B to the conveyance center FC. The fourth rib 752D is connected to the third rib 752C.
The third rib 752C has a side surface 752F facing the first extension direction exposed at the portion where the fourth rib 752D connects to the third rib 752C.

According to the seventh embodiment, the grease GR is concentrated in the center, preventing the lubricant from leaking from the ends.

The present invention is not limited to the above-described embodiment and can be used in various forms, as exemplified below.

In the above embodiment, a cylindrical roller incorporating a heater 110 was used as the rotating body, but the present invention is not limited to this. For example, the rotating body may be an endless belt whose inner circumferential surface is heated by a heater. Alternatively, an external heating method in which a heater is disposed outside the rotating body and heats the outer circumferential surface of the rotating body, or an induction heating method may be used. Alternatively, a heater may be disposed inside the endless belt and the rotating body in contact with the outer circumferential surface of the endless belt may be indirectly heated. Alternatively, the rotating body and the endless belt may each incorporate a heater.

In the above embodiment, the sliding sheet 150 was configured such that the area ratio of the convex portions 152 on the opposing surface 151 to the specified area was 50% or less, but the area ratio of the convex portions 152 may be greater than 50%.

In the above embodiment, the angle between the movement direction of the endless belt 130 and the first extension direction was 45°, and the angle between the movement direction of the endless belt 130 and the second extension direction was 45°, but this is not limited to 45° and may be, for example, any angle between 10° and 80°.

The elements described in the above embodiments and variations may be implemented in any combination.

REFERENCE SIGNS LIST 1 image forming apparatus 2 main body housing 8 fixing device 100 fixing device 110 heater 120 rotating body 130 endless belt 131 inner peripheral surface 150 sliding sheet 150A end 150B end 151 opposing surface 152 convex portion 152A first rib 152B second rib 152C side surface 153 concave portion GR grease

Claims (9)

A rotating body;
an endless belt that contacts the outer circumferential surface of the rotating body;
a heater for heating at least one of the rotating body and the endless belt;
a pressure member that sandwiches the endless belt between itself and the rotating body;
a sliding sheet sandwiched between the inner circumferential surface of the endless belt and the pressure member;
a lubricant disposed between the endless belt and the sliding sheet,
a surface of the sliding sheet facing the inner circumferential surface of the endless belt has a rib-shaped convex portion that is convex toward the endless belt and a concave portion that is concave relative to the convex portion,
The convex portion is
a first rib extending in a first extension direction that is oblique to a moving direction of the endless belt;
a second rib extending in a second extension direction intersecting the first extension direction and connected to the first rib;
The fixing device, wherein the first rib has a side surface facing the second extension direction exposed at a portion where the second rib is connected to the first rib. The fixing device described in claim 1, characterized in that the angle between the movement direction and the first extension direction is equal to the angle between the movement direction and the second extension direction. The fixing device described in claim 1 or claim 2, characterized in that the first rib and the second rib extend linearly. A fixing device according to any one of claims 1 to 3, characterized in that the first rib and the second rib are perpendicular to each other. The top of the first rib is higher than the top of the second rib,
5. The fixing device according to claim 1, wherein the side surface of the second rib protrudes toward the endless belt from the top of the second rib at a portion where the second rib connects to the first rib. A fixing device according to any one of claims 1 to 5, characterized in that the opposing surface has a groove located between the first rib and the second rib at the portion where the second rib connects to the first rib, and extending in the first extension direction. the first rib extends from one side to the other side in a width direction of the endless belt as it moves downstream in the moving direction,
7. The fixing device according to claim 1, further comprising a temperature sensor that detects the temperature of the end portion of the rotating body on the other side in the width direction. The fixing device according to claim 7, wherein the first rib extends continuously from the end on one side in the width direction to the end on the other side. the first rib extends from the end portion on the one side to a center portion of the sliding sheet in the width direction,
The convex portion is
a third rib extending in the second extension direction from the end portion on the other side in the width direction to a center portion of the sliding sheet in the width direction;
a fourth rib extending in the first extension direction and connected to the third rib,
The fixing device according to claim 7 , wherein the third rib has a side surface facing the first extension direction exposed at a portion where the fourth rib is connected to the third rib.