JP2023147165A - Fixing device and image forming apparatus - Google Patents

Abstract

To provide a fixing device that prevents excessive adhesion of lubricant to an inner peripheral surface of a fixing belt and prevents wave-like deformation of the fixing belt.SOLUTION: A fixing device 7 comprises: a fixing belt 20 that rotates around an axis to heat a toner image on a sheet P; a pressure roller 21 that applies pressure to toner on the sheet P passing through a pressure area N; and a heater holder 22 that is provided inside the fixing belt 20, and has a first slide surface 26 in contact with an inner peripheral surface 20A of the fixing belt 20 with lubricant therebetween. The heater holder 22 has a plurality of first slits 31 that are arranged side by side in the first slide surface 26 on the upstream side of the pressure area N in the passage direction of the sheet P and guide the movement of lubricant directed from the upstream to the downstream in the direction of rotation of the fixing belt 20, and damming parts 41 that restrict the outflow of the lubricant from the respective first slits 31 and regulate fall-down of the fixing belt 20 into the respective first slits 31.SELECTED DRAWING: Figure 3

Description

The present invention relates to a fixing device and an image forming apparatus that fix toner images on a medium.

A fixing device is known that includes a fixing belt and a pressure roller that comes into contact with the fixing belt to form a nip portion (Patent Document 1). A nip forming member is disposed inside the fixing belt, and a lubricant is attached between the inner peripheral surface of the fixing belt and the sliding surface of the nip forming member. A plurality of inclined grooves are formed on the sliding surface of the nip forming member to transfer the lubricant toward the central portion in the axial direction (width direction). The downstream end of the inclined groove in the rotational direction of the fixing belt is formed to be continuous with the sliding surface of the nip forming member without any step between the downstream end and the sliding surface of the nip forming member.

JP 2018-5047 Publication

However, in the above-mentioned fixing device, the downstream end of the inclined groove is formed so as to be continuous with the sliding surface, so the lubricant accumulated in the inclined groove easily flows out and excessively adheres to the inner circumferential surface of the fixing belt. I had something to do.

Further, in the above-described fixing device, the fixing belt may fall into the inclined groove and be deformed in a wavy manner in the axial direction. The lubricant does not adhere uniformly to the inner circumferential surface of the fixing belt that has been deformed in a undulating manner, and there is a possibility that sliding resistance (friction) between the fixing belt and the nip forming member may increase. Further, in a fixing belt that is deformed in a wavy manner, the pressure at the nip portion is not uniform in the axial direction, and image defects such as streaky unevenness in gloss may occur in the fixed image. Furthermore, when the fixing belt that has been deformed in a wavy manner rotates, a force that moves the fixing belt in the axial direction acts, and there is a possibility that the end portion of the fixing belt may be damaged.

In consideration of the above circumstances, the present invention provides a fixing device and an image forming apparatus that suppress excessive adhesion of lubricant to the inner circumferential surface of a fixing belt and suppress undulating deformation of the fixing belt.

The fixing device of the present invention is formed into a flexible cylindrical shape, and is provided between a fixing belt that heats a toner image on a medium while rotating around an axis, and a fixing belt that rotates around an axis and heats a toner image on a medium. a pressure member that forms a pressure region and presses the toner on the medium passing through the pressure region; and a pressure member that is provided inside the fixing belt and contacts the inner circumferential surface of the fixing belt via a lubricant. a holder having a sliding surface and holding a heater that heats the fixing belt; A plurality of slits that are arranged in a row and guide the movement of the lubricant from upstream to downstream in the rotational direction of the fixing belt, and restrict the outflow of the lubricant from each of the slits, and and a blocking portion that restricts the fixing belt from falling.

In this case, each of the slits has a bottom surface and a peripheral wall surface, and is recessed so as to form an annular opening edge on the sliding surface, and the blocking portion is provided for each of the slits. It is preferable to include a wall surface located on the downstream side in the rotational direction of the fixing belt among the surrounding wall surfaces.

In this case, the blocking portion may include a rib protruding from the sliding surface of the holder on the downstream side of the plurality of slits in the rotational direction of the fixing belt.

In this case, each of the slits may be inclined toward the center in the axial direction from upstream to downstream in the rotational direction of the fixing belt.

In other cases, the plurality of slits extend axially from upstream to downstream in the rotational direction of the fixing belt, except for at least one slit that extends parallel to the rotational direction of the fixing belt near the center in the axial direction. The inclination angle of the plurality of slits may gradually increase from the center in the axial direction toward both outer sides.

In this case, the slit has an inflow portion that allows the lubricant to flow in from an upstream side in the rotational direction of the fixing belt, and an outflow portion that allows the lubricant to flow out downstream in the rotational direction of the fixing belt. The sliding surface includes a facing area facing the medium with the fixing belt in between, and a pair of opposing areas facing the medium on both sides of the facing area in the axial direction and not facing the medium with the fixing belt in between. a non-opposing area, the blocking portion is formed only in the opposing area, a plurality of the slits are formed in the opposing area, and each non-opposing area has at least one slit. is formed, and at least the slit formed in the non-opposing area and the slit formed at the outermost end in the axial direction of the opposing area each have a The outflow portion may be inclined so as to overlap the inflow portion of the other slit adjacent to the inside in the axial direction.

The image forming apparatus of the present invention includes any one of the fixing devices described above.

According to the present invention, excessive adhesion of lubricant to the inner circumferential surface of the fixing belt can be suppressed, and undulating deformation of the fixing belt can be suppressed.

1 is a schematic diagram (side view) showing the internal structure of an image forming apparatus according to an embodiment of the present invention. FIG. 1 is a perspective view showing a fixing device according to a first embodiment of the present invention. 3 is a sectional view taken along line III-III in FIG. 2. FIG. FIG. 1 is a front view showing a fixing device according to a first embodiment of the present invention. FIG. 2 is a rear view showing the fixing device according to the first embodiment of the present invention. FIG. 3 is a sectional view showing a fixing device according to a second embodiment of the invention. FIG. 7 is a front view showing a fixing device according to a second embodiment of the present invention. FIG. 7 is a rear view showing a fixing device according to a second embodiment of the present invention. FIG. 7 is a front view showing a fixing device according to a modification of the first embodiment of the present invention. FIG. 7 is a rear view showing a fixing device according to a modification of the first embodiment of the present invention. FIG. 7 is a front view showing a fixing device according to another modification of the first embodiment of the present invention. FIG. 7 is a rear view showing a fixing device according to another modification of the first embodiment of the present invention. FIG. 7 is an enlarged front view showing a part of the first sliding surface of the fixing device according to another modification of the first embodiment of the present invention. FIG. 7 is an enlarged rear view of a part of the second sliding surface of the fixing device according to another modification of the first embodiment of the present invention. FIG. 6 is an explanatory diagram illustrating the effect of a slit in a fixing device according to another modification of the first embodiment of the present invention. FIG. 7 is an explanatory diagram illustrating another function of the slit of the fixing device according to another modification of the first embodiment of the present invention.

Embodiments of the present invention will be described below with reference to the accompanying drawings. Note that Fr, Rr, L, R, U, and D shown in the drawings indicate front, rear, left, right, top, and bottom. Further, the front-rear direction (passing direction), the left-right direction (axial direction), and the up-down direction are orthogonal to each other. Although terms indicating directions and positions are used in this specification, these terms are used for convenience of explanation and do not limit the technical scope of the present invention. Further, "upstream" and "downstream" and similar terms refer to "upstream" and "downstream" in the passing direction (transportation direction) of the paper P, and similar concepts. Note that in each figure, dimensions, angles, etc. of members are not exact, but are shown schematically for the purpose of explanation.

An image forming apparatus 1 according to an embodiment will be described with reference to FIG. FIG. 1 is a schematic diagram (side view) showing an image forming apparatus 1. As shown in FIG.

The image forming apparatus 1 is an electrophotographic printer. The image forming apparatus 1 includes an apparatus main body 2 having a substantially rectangular parallelepiped appearance. At the bottom of the apparatus main body 2, for example, a paper feed cassette 3 that accommodates paper P (medium) is removably provided. A paper discharge tray 4 is provided on the upper surface of the apparatus main body 2. Note that the paper P as an example of the medium is not limited to paper, and may be a resin sheet or the like.

The image forming apparatus 1 includes a paper feeding device 5, an image forming device 6, and a fixing device 7. The paper feed device 5 is provided at the upstream end of the conveyance path 9A extending from the paper feed cassette 3 to the paper discharge tray 4, and feeds the sheets P stored in the paper feed cassette 3 one by one to the conveyance path 9A. The image forming device 6 is provided at an intermediate portion of the conveyance path 9A, and forms a toner image on the sheet P being conveyed. The fixing device 7 is provided on the downstream side of the conveyance path 9A, and thermally fixes the toner image on the paper P.

The transport path 9A is provided with a pair of registration rollers 10A that temporarily blocks the paper P being transported and corrects the inclination of the paper P (skew correction). A reversing conveyance path 9B is provided below the conveyance path 9A, which branches off on the downstream side of the conveyance path 9A and merges with the upstream side of the conveyance path 9A. The reversing conveyance path 9B is provided with a plurality of conveyance roller pairs 10B that convey the paper P.

The image forming device 6 includes a toner container 11, a drum unit 12, and an optical scanning device 13. The toner container 11 is arranged at the front upper part of the apparatus main body 2 and contains, for example, black toner (developer). The drum unit 12 includes a photosensitive drum 14 , a charging device 15 , a developing device 16 , and a transfer roller 17 . The photosensitive drum 14 is formed into a substantially cylindrical shape and is driven to rotate around an axis by a motor (not shown). The charging device 15, the developing device 16, and the transfer roller 17 are arranged around the photosensitive drum 14 in the order of the image forming process. The transfer roller 17 contacts the photosensitive drum 14 from below to form a transfer nip. The optical scanning device 13 is provided above the photoreceptor drum 14 and emits scanning light toward the surface of the photoreceptor drum 14 .

[Image formation processing]
The operation of the image forming apparatus 1 will be explained. A control device (not shown) that centrally controls the image forming apparatus 1 executes image forming processing as described below based on image data input from an external terminal.

The charging device 15 charges the surface of the photoreceptor drum 14, and the optical scanning device 13 emits scanning light based on image data to form an electrostatic latent image on the photoreceptor drum 14. The developing device 16 develops a toner image on the photoreceptor drum 14 using the toner supplied from the toner container 11 . The paper feed device 5 feeds the sheets of paper P one by one from the paper feed cassette 3 to the conveyance path 9A. The paper P is conveyed along the conveyance path 9A, skew-corrected by the registration roller pair 10A, and enters the transfer nip. Transfer roller 17 transfers the toner image on photoreceptor drum 14 onto the surface of paper P passing through the transfer nip. The fixing device 7 heat-fixes the toner image onto the paper P. In the case of single-sided printing, the paper P that has passed through the fixing device 7 is discharged to the paper discharge tray 4.

In the case of double-sided printing, the paper P that has passed through the fixing device 7 is switched back at the downstream end of the conveyance path 9A and sent to the reversal conveyance path 9B. The paper P is transported by the transport roller pair 10B, returned to the transport path 9A from the reverse transport path 9B, and is sent to the transfer nip after being skew-corrected by the registration roller pair 10A. Thereafter, the toner image is transferred to the paper P, thermally fixed, and the paper P with double-sided printing is discharged to the paper discharge tray 4.

[First embodiment: Fixing device]
The fixing device 7 according to the first embodiment will be described with reference to FIGS. 2 and 3. FIG. 2 is a perspective view showing the fixing device 7. As shown in FIG. FIG. 3 is a cross-sectional view taken along line III--III in FIG.

The fixing device 7 includes a fixing belt 20, a pressure roller 21, a heater holder 22, and a heater 23. The fixing belt 20 and the pressure roller 21 are supported by a frame (not shown), and the frame is fixed to the main body 2 of the apparatus. The heater holder 22 is provided inside the fixing belt 20, and the heater 23 is held by the heater holder 22 (see FIG. 3).

<Fuser belt>
The fixing belt 20 is an endless belt formed into a substantially cylindrical shape that is long in the left-right direction (axial direction). The fixing belt 20 is made of, for example, a synthetic resin having heat resistance and flexibility (elasticity). A pair of holding members 24 (see FIG. 2) are inserted into both left and right ends of the fixing belt 20 to hold the fixing belt 20 in a substantially cylindrical shape. The pair of holding members 24 rotatably guide both ends of the fixing belt 20 in the axial direction. Note that the fixing belt 20 is supported by a frame via a pair of holding members 24 (not shown).

<Pressure roller>
The pressure roller 21, which is an example of a pressure member, is formed into a substantially cylindrical shape that is long in the left-right direction. The pressure roller 21 has a metal core 21A and an elastic layer 21B made of silicon sponge or the like laminated on the outer peripheral surface of the core (see FIG. 3). A drive motor M is connected to the left end of the core metal 21A via a gear train (not shown) (see FIG. 2). The pressure roller 21 contacts the fixing belt 20 from below, and forms a pressure area N between the pressure roller 21 and the fixing belt 20 . Note that the pressurized area N refers to an area from an upstream position where the pressure is 0 Pa to a downstream position where the pressure becomes 0 Pa again via a position where the pressure acts.

<Heater holder>
As shown in FIG. 3, the heater holder 22 (holder) is supported by a support member 25 inside the fixing belt 20. The support member 25 is made of a metal material such as stainless steel, and has a substantially rectangular tube shape that is long in the left-right direction (axial direction). The support member 25 is installed between the pair of holding members 24 . The heater holder 22 is fixed to the lower part of the support member 25. The heater holder 22 is made of, for example, a heat-resistant and abrasion-resistant synthetic resin and is formed into a substantially semi-cylindrical shape that is elongated in the left-right direction. The heater holder 22 is in contact with the inner circumferential surface 20A of the lower side (pressure area N side) of the fixing belt 20.

<Heater>
The heater 23 is formed into a substantially rectangular plate shape that is elongated in the left-right direction, and is fixed to the lower surface of the heater holder 22. The heater 23 includes a heating resistor (not shown) that is laminated on the substrate and generates heat when energized. The heater 23 has a heating resistor in contact with the inner circumferential surface 20A of the fixing belt 20 at a position corresponding to the pressurized area N.

Note that the frame that supports the fixing belt 20 and the like is provided with a temperature sensor (not shown) for detecting the surface temperature of the fixing belt 20. The drive motor M, the heater 23, the temperature sensor, and the like are electrically connected to the control device of the image forming apparatus 1 via various drive circuits (not shown) and are appropriately controlled.

[Fixing device action]
Here, the function (fixing process) of the fixing device 7 will be explained. The pressure roller 21 rotates in response to the driving force of the drive motor M, and the fixing belt 20 rotates following the pressure roller 21 (see the arrow in FIG. 3). The heater 23 heats the fixing belt 20. The control device receives a detection signal from the temperature sensor and starts executing the image forming process described above while controlling the heater 23 to maintain a preset temperature.

The paper P onto which the toner image has been transferred enters the pressure area N. The fixing belt 20 heats the toner (toner image) on the paper P passing through the pressure area N while rotating around an axis. The pressure roller 21 presses the toner on the paper P passing through the pressure area N while rotating around an axis. Then, the toner image is fixed on the paper P. Then, the paper P on which the toner image is fixed is discharged to the paper discharge tray 4.

[Heater holder details]
As shown in FIG. 3, the heater holder 22 contacts the inner circumferential surface 20A of the fixing belt 20 on the upstream and downstream sides of the portion holding the heater 23 (position corresponding to the pressurized area N). It has sliding surfaces 26 and 27. In this specification, for convenience of explanation, the sliding surface 26 located upstream of the pressurizing area N is referred to as the "first sliding surface 26", and the sliding surface 26 downstream of the pressurizing area N is referred to as the "first sliding surface 26". 27 will be referred to as the "second sliding surface 27", and the first sliding surface 26 and the second sliding surface 27 will be simply referred to as "sliding surfaces 26, 27" in the common explanation.

A lubricant (not shown) is applied to the inner peripheral surface 20A of the fixing belt 20, and the sliding surfaces 26 and 27 of the heater holder 22 come into contact with the inner peripheral surface 20A of the fixing belt 20 via the lubricant. ing. The lubricant is grease or the like that has viscosity and fluidity, and reduces the frictional resistance between the fixing belt 20 and the heater holder 22. The lubricant moves as the fixing belt 20 rotates, but in the portion where the inner circumferential surface 20A of the fixing belt 20 is not in contact with the sliding surfaces 26 and 27, the lubricant moves toward both outer sides in the axial direction. It has been known. As the fixing process is repeated, lubricant leaks from both ends of the fixing belt 20 in the axial direction, and when the amount of lubricant decreases, the frictional resistance between the fixing belt 20 and the heater holder 22 increases, causing the fixing belt 20 to There was a risk that smooth rotation would be hindered.

Therefore, the fixing device 7 according to the present embodiment has a structure that suppresses leakage of the lubricant applied to the inner circumferential surface 20A of the fixing belt 20. Hereinafter, a structure for suppressing lubricant leakage will be described with reference to FIGS. 3 to 5. FIG. 4 is a front view showing the fixing device 7. FIG. FIG. 5 is a rear view showing the fixing device 7. As shown in FIG. Note that in FIGS. 4 and 5, illustration of the fixing belt 20 is omitted.

<Slit>
The heater holder 22 has a plurality of first slits 31 (see FIG. 4) arranged in the left-right direction (axial direction) on the first sliding surface 26 on the upstream side of the pressurizing area N, and It has a plurality of second slits 32 (see FIG. 5) arranged in the axial direction on the second sliding surface 27 on the downstream side. The plurality of first slits 31 and the plurality of first slits 31 each guide the movement of the lubricant from upstream to downstream in the rotational direction of the fixing belt 20. In this specification, in order to simplify the explanation, one first slit 31 and one second slit 32 will be mainly explained, and common explanations for the first slit 31 and the second slit 32 will be simply referred to as " slits 31 and 32. Furthermore, as mentioned at the beginning, in this specification, simply "upstream/downstream" refers to the passing direction (conveying direction) of the paper P, and "upstream/downstream" in the rotational direction of the fixing belt 20. It is differentiated.

As shown in FIGS. 4 and 5, the slits 31 and 32 are grooves that extend linearly along the rotational direction of the fixing belt 20. As shown in FIGS. To be precise, the slits 31 and 32 are inclined toward the center in the axial direction from upstream to downstream in the rotational direction of the fixing belt 20. The inclination angles (absolute values) of the plurality of slits 31 and 32 are all the same size, and the plurality of slits 31 and 32 are arranged symmetrically with respect to the center in the left-right direction. Note that the intervals between the plurality of slits 31 and 32 that are inclined in the same direction (centroid distance) are approximately equal intervals, but are not limited to this, and may be irregular intervals (not shown). Moreover, although the widths of the plurality of slits 31 and 32 are the same in the axial direction, they may be formed to have different widths (not shown).

(1st slit)
As shown in FIGS. 3 and 4, the first slit 31 has a bottom surface 31A and a peripheral wall surface 31B, and is depressed so as to form an annular opening edge 31C on the first sliding surface 26. As shown in FIGS. The bottom surface 31A and the opening edge 31C have a substantially parallelogram outer shape, and the peripheral wall surface 31B is formed into a substantially rectangular cylindrical shape so as to connect the peripheral edge of the bottom surface 31A and the opening edge 31C. That is, the peripheral wall surface 31B forms a step between the bottom surface 31A and the first sliding surface 26. This step may be, for example, about 0.5 to 2.0 mm. A wall surface of the peripheral wall surface 31B of the first slit 31 located on the downstream side in the rotational direction of the fixing belt 20 serves as a blocking portion 41 that restricts the outflow of the lubricant from the first slit 31. Although details will be described later, the blocking portion 41 also has a function of restricting the fixing belt 20 from falling into the first slit 31. The blocking part 41 is located upstream of the most upstream end of the pressurizing area N (the holding part of the heater 23), and there is also a gap between the blocking part 41 and the most upstream end of the pressurizing area N. 1 sliding surface 26 is formed.

(Second slit)
As shown in FIGS. 3 and 5, the second slit 32 is shaped like the first slit 31 upside down. The second slit 32 has a bottom surface 32A and a peripheral wall surface 32B, and is depressed so as to form an annular opening edge 32C on the second sliding surface 27. A wall surface located on the downstream side in the rotational direction of the peripheral wall surface 32B serves as a blocking portion 42.

[Effect of slit]
The lubricant attached to the inner peripheral surface 20A of the fixing belt 20 moves downstream in the rotation direction as the fixing belt 20 rotates, and the lubricant adheres to the inner peripheral surface 20A of the fixing belt 20 (inner peripheral surface) that slides on the first sliding surface 26. Lubricate surface 20A). The lubricant enters the first slit 31 and moves along the first slit 31 toward the center in the axial direction.

As the rotation of the fixing belt 20 progresses, the lubricant lubricates the fixing belt 20 sliding against the heater 23, and when the fixing belt 20 passes through the pressure area N, it slides against the second sliding surface 27. The moving fixing belt 20 is lubricated. The lubricant enters the second slit 32 and moves along the second slit 32 toward the center in the axial direction.

As described above, since the slits 31 and 32 are inclined toward the center in the axial direction from upstream to downstream in the rotational direction of the fixing belt 20, the lubricant is moved to the center in the axial direction of the heater holder 22. can be done. Thereby, leakage of lubricant from both outer ends of the fixing belt 20 in the axial direction can be suppressed.

By the way, if the slits 31, 32 do not have blocking parts 41, 42 (steps) and the downstream sides of the slits 31, 32 in the rotational direction smoothly continue to the sliding surfaces 26, 27, the slits 31, 32 Substantially all of the lubricant that has flowed in may flow out, resulting in an excessive amount of lubricant adhering to the inner circumferential surface 20A of the fixing belt 20. Further, in the case of the above assumption, the fixing belt 20 may drop to the downstream side of the slits 31 and 32 in the rotational direction and be deformed in a undulating manner in the axial direction. The lubricant does not adhere uniformly to the inner circumferential surface 20A of the fixing belt 20 that has been deformed in a undulating manner, and there is a possibility that the sliding resistance (friction) between the fixing belt 20 and the sliding surfaces 26 and 27 will increase. In addition, in the fixing belt 20 that has been deformed in a wavy manner, the pressure in the pressure area N is not uniform in the axial direction, and image defects such as streaky uneven gloss may occur in the fixed image. . Furthermore, when the fixing belt 20 that has been deformed in a wavy manner rotates, a force that moves the fixing belt 20 in the axial direction acts, and there is a risk that the end of the fixing belt 20 may come into contact with the holding member 24 and be damaged.

To address the above-described problem, in the fixing device 7 according to the first embodiment, blocking portions 41 and 42 are formed on the downstream side of the slits 31 and 32 in the rotational direction to restrict movement of the lubricant. Some of the lubricant moving along the slits 31 and 32 overcomes the blocking parts 41 and 42 and flows out, but the remaining lubricant is blocked by the blocking parts 41 and 42 and leaves the slits 31 and 32. remain in the Thereby, the amount of lubricant flowing out from the slits 31 and 32 can be restricted, and excessive adhesion of the lubricant to the inner circumferential surface 20A of the fixing belt 20 can be suppressed.

Further, in the fixing device 7 according to the first embodiment, the slits 31 and 32 are depressions having annular opening edges 31C and 32C on the sliding surfaces 26 and 27, and the fixing belt 20 has annular opening edges 31C and 32C. It was designed to be supported by 32C. According to this configuration, it is possible to suppress the fixing belt 20 from falling into the slits 31 and 32 and deforming in a wavy manner in the axial direction. Thereby, the lubricant can be applied substantially uniformly to the smooth inner circumferential surface 20A of the fixing belt 20. As a result, an increase in sliding resistance (friction) between the fixing belt 20 and the heater holder 22 can be suppressed, and smooth rotation of the fixing belt 20 can be ensured. Furthermore, since undulating deformation of the fixing belt 20 is suppressed on the upstream side of the pressure area N, the pressure in the pressure area N can be made substantially uniform across the axial direction. Thereby, image defects such as uneven gloss can be suppressed. Furthermore, since the force that moves the fixing belt 20 in the axial direction becomes difficult to exert due to the rotation of the fixing belt 20, the end portion of the fixing belt 20 is prevented from coming into contact with the holding member 24, and damage to the end portion of the fixing belt 20 is suppressed. You can also do it.

[Second embodiment: fixing device]
Next, a fixing device 8 according to a second embodiment will be described with reference to FIGS. 6 to 8.
FIG. 6 is a sectional view showing the fixing device 8. As shown in FIG. FIG. 7 is a front view showing the fixing device 8. As shown in FIG. FIG. 8 is a rear view showing the fixing device 8. As shown in FIG. Note that in FIGS. 7 and 8, illustration of the fixing belt 20 is omitted. Further, in the following description, the same components as those of the fixing device 7 according to the first embodiment are given the same reference numerals, and the description of the similar components will be omitted.

The fixing device 8 according to the second embodiment is different from the fixing device 7 according to the first embodiment in slits 33 and 34 formed in the sliding surfaces 26 and 27 and blocking portions 43 and 44.

The heater holder 22 has a plurality of first slits 33 (see FIG. 7) arranged in the left-right direction (axial direction) on the first sliding surface 26 on the upstream side of the pressurizing area N; It has a plurality of second slits 34 (see FIG. 8) arranged in the axial direction on the second sliding surface 27 on the downstream side. In this specification, in order to simplify the explanation, one first slit 33 and one second slit 34 will be mainly explained, and common explanations for the first slit 33 and the second slit 34 will be simply referred to as " slits 33 and 34.

As shown in FIGS. 6 and 7, the first slit 33 has a bottom surface 33A and a peripheral wall surface 33B, and is recessed to form a U-shaped opening edge 33C on the first sliding surface 26. . The peripheral wall surface 33B has no wall surface on the downstream side in the rotational direction of the fixing belt 20, and the downstream end of the bottom surface 33A is formed so as to be continuous with the first sliding surface 26 without forming a step. Note that the second slit 34 (bottom surface 34A, peripheral wall surface 34B, opening edge 34C) has a shape similar to that of the first slit 33 upside down (see FIGS. 6 and 8), so a detailed description thereof will be given below. Omitted.

As shown in FIGS. 6 to 8, the blocking parts 43 and 44 are ribs protruding from the sliding surfaces 26 and 27 of the heater holder 22 on the downstream side of the slits 33 and 34 in the rotational direction of the fixing belt 20. It is. The blocking portions 43 and 44 extend linearly in the axial direction at positions close to the slits 33 and 34. The upper ends of the blocking parts 43 and 44 are preferably rounded, and the height of the blocking parts 43 and 44 is preferably about 0.5 to 2.0 mm, for example.

[Effect of slit]
The lubricant attached to the inner peripheral surface 20A of the fixing belt 20 moves downstream in the rotational direction as the fixing belt 20 rotates, and moves toward the center in the axial direction along the slits 33 and 34. Most of the lubricant that has flowed into the slits 33 and 34 flows out. A part of the lubricant flowing out from the slits 33 and 34 overcomes the blocking parts 43 and 44 and moves downstream in the rotational direction, but the remaining lubricant is blocked by the blocking parts 43 and 44.

According to the fixing device 8 according to the second embodiment described above, the amount of lubricant flowing out from the slits 33 and 34 can be restricted, and excessive adhesion of the lubricant to the inner circumferential surface 20A of the fixing belt 20 can be prevented. Can be suppressed. Further, since the fixing belt 20 is supported by the blocking parts 43 and 44, it is possible to suppress the fixing belt 20 from falling into the slits 33 and 34 and deforming in a wavy manner in the axial direction. As a result, it is possible to obtain the same effects as the fixing device 7 according to the first embodiment, such as smooth rotation of the fixing belt 20, suppression of image defects, and suppression of damage to the ends of the fixing belt 20.

Note that in the fixing device 8 according to the second embodiment, the downstream ends of the slits 33 and 34 are formed to be continuous with the sliding surfaces 26 and 27, but the present invention is not limited to this. In the fixing device 8 according to the second embodiment, the slits 31 and 32 of the fixing device 7 according to the first embodiment may be applied instead of the slits 33 and 34 (not shown). That is, the blocking parts 41, 42 provided in the slits 31, 32 and the rib-shaped blocking parts 43, 44 may be provided on the sliding surfaces 26, 27 (not shown). By providing the two types of blocking portions 41 to 44 in this manner, excessive adhesion of lubricant to the inner circumferential surface 20A of the fixing belt 20 and waving of the fixing belt 20 can be more effectively suppressed. be able to.

[Modified example]
Note that in the fixing devices 7 and 8 according to the first and second embodiments, the plurality of slits 31 to 34 are inclined at the same angle, so depending on the inclination angle, the lubricant may be applied to the center in the axial direction. It is also possible that there are too many people gathered in the club. Therefore, in a fixing device 7 according to a modified example of the first embodiment, as shown in FIGS. The other slits 31 and 32 other than these three slits 31 and 32 may be inclined toward the center in the axial direction from upstream to downstream in the rotational direction of the fixing belt 20. Further, the inclination angle of the plurality of slits 31 and 32 may gradually increase from the center in the axial direction toward both outer sides. According to this configuration, the movement direction of the lubricant can be directed toward the center as the slits 31 and 32 are located on the outer side in the axial direction. This makes it possible to prevent the lubricant from gathering too much in the center in the axial direction, and to prevent the lubricant from leaking from both ends of the fixing belt 20 in the axial direction. As a result, the lubricant can be applied substantially uniformly to the inner peripheral surface 20A of the fixing belt 20.

In addition, in the slits 31, 32 according to the above-described modification, the three slits 31, 32 near the center in the axial direction were formed parallel to the rotation direction, but the present invention is not limited to this, and at least one slit 31, 32 should just be formed parallel to the rotation direction. Moreover, although the slits 31 and 32 according to the above-described modification were formed in both the upstream and downstream sliding surfaces 26 and 27, the present invention is not limited to this. A slit 31, 32 according to a modified example may be formed on either one of the upstream and downstream sliding surfaces 26, 27, and a slit 31, 32 inclined at the same angle may be formed on the other one. (not shown). Furthermore, the features of the slits 31 and 32 according to the above-described modification may be applied to the slits 33 and 34 of the fixing device 8 according to the second embodiment (not shown).

[Other variations]
Note that in order to heat and press the toner on the paper P, the pressure area N and the sliding surfaces 26 and 27 are formed longer in the left-right direction (axial direction) than the width of the paper P (horizontal dimension). ing. Therefore, the fixing belt 20 has a paper passing area (not shown) that contacts the paper P, and a pair of paper non-passing areas (not shown) that do not contact the paper P on both sides of the paper passing area in the axial direction. ). Furthermore, sliding surfaces 26 and 27 that contact the inner circumferential surface 20A of the fixing belt 20 correspond to the sheet passing area, and have opposing areas 26A and 27A that face the paper P with the fixing belt 20 in between, and a pair of non-passing areas. It has a pair of non-opposed areas 26B, 27B that correspond to the paper area and are located on both sides of the opposing areas 26A, 27A in the axial direction and do not face the paper P with the fixing belt 20 in between. In the non-sheet passing areas (non-opposed areas 26B, 27B), the lubricant tends to move toward both axially outer sides, so it is preferable to direct the flow of the lubricant toward the center in the axial direction. Therefore, for example, the fixing device 7 according to another modification of the first embodiment has, in addition to the features of the fixing device 7 according to the modification described above, a configuration that suppresses leakage of lubricant to both outer sides in the axial direction. We are prepared.

A fixing device 7 according to another modification will be described with reference to FIGS. 11 to 14. FIG. 11 is a front view showing the fixing device 7. FIG. FIG. 12 is a rear view showing the fixing device 7. FIG. FIG. 13 is an enlarged front view of a part of the first sliding surface 26 of the fixing device 7. As shown in FIG. FIG. 14 is an enlarged rear view of a part of the second sliding surface 27 of the fixing device 7. As shown in FIG.

As shown in FIGS. 11 and 12, in the fixing device 7 according to another modification, the blocking portions 41 and 42 are formed only in the facing areas 26A and 27A, and in the non-facing areas 26B and 27B. Not formed. To be more specific, a plurality of slits 31 and 32 having blocking portions 41 and 42 are formed side by side in opposing areas 26A and 27A of sliding surfaces 26 and 27, respectively. On the other hand, two slits 33, 34 without blocking portions 41, 42 are formed side by side in the non-opposing regions 26B, 27B of each of the sliding surfaces 26, 27. In addition, in FIGS. 11 and 12, two slits 33, 34 are formed in each non-opposed region 26B, 27B, but the present invention is not limited to this, and at least one slit 33, 34 may be formed. . Moreover, two or more slits 31 and 32 may be formed in the opposing regions 26A and 27A.

As shown in FIGS. 13 and 14, two slits 33, 34 formed in the non-opposing regions 26B, 27B and several (for example, 5 to 6 slits) formed on the axial outside of the opposing regions 26A, 27A. (See FIGS. 11 and 12)) When viewed from the rotational direction of the fixing belt 20, the slits 31 and 32 of FIG. It is inclined so as to overlap part F1 (see also the broken lines shown in FIGS. 13 and 14). Here, in the slits 31 to 34, the "inflow part F1" is a part (upstream end) into which the lubricant flows from the upstream side in the rotational direction of the fixing belt 20, and the "outflow part F2" is a part (upstream end) of the fixing belt 20. This is a portion (downstream end) from which the lubricant flows out downstream in the rotational direction of 20.

Specifically, in the non-opposing regions 26B, 27B, the outflow portion F2 of the slit 33, 34 located at the outermost end in the axial direction is the innermost slit 33, 34 adjacent to the slit 33, 34 in the axial direction, when viewed from the rotation direction. It overlaps with the inflow portion F1. Furthermore, the outflow portions F2 of the slits 33 and 34 located on the inner side in the axial direction in the non-opposing regions 26B and 27B are the most axially innermost in the opposing regions 26A and 27A, which are adjacent to each other in the axial direction, when viewed from the rotation direction. It overlaps with the inlet portion F1 of the slits 31 and 32 located at the outer ends. Further, in the opposing regions 26A, 27A, the outflow portions F2 of the slits 31, 32 located at the outermost ends in the axial direction overlap with the inflow portions F1 of the slits 31, 32 adjacent to each other in the axial direction. Hereinafter, some slits 31 and 32 formed on the axially outer sides of the opposing regions 26A and 27A, and a pair of adjacent slits 32, are arranged such that the outer outflow portion F2 overlaps the inner inflow portion F1. (See FIGS. 11 and 12).

Note that when viewed from the rotational direction of the fixing belt 20, "overlapping" the outflow portions F2 and the inflow portions F1 of the adjacent slits 31 to 34 means that the outflow portions F2 and the inflow portions F1 are completely aligned with each other. However, the meaning is not limited to this, and includes, for example, partially overlapping the widths of the slits 31 to 34. Furthermore, since the inclination angles of the plurality of slits 31 to 34 gradually decrease from both outer sides in the axial direction toward the center, the overlapping width between the outflow portion F2 and the inflow portion F1 of the adjacent slits 31 to 34 is also It gradually decreases from both outer sides in the axial direction toward the center (see FIGS. 11 and 12). In the intermediate portions of the opposing regions 26A and 27A, excluding the vicinity of both outer sides in the axial direction, the outflow portions F2 and inflow portions F1 of the adjacent slits 31 and 32 do not overlap when viewed from the rotation direction (Figs. 11 and 12 reference).

[Effect of slit]
The functions of the slits 31 to 34 of the fixing device 7 according to another modification will be described with reference to FIG. 15. FIG. 15 is an explanatory diagram illustrating the function of the slits 31 to 34.

The lubricant attached to the inner circumferential surface 20A of the fixing belt 20 enters the slits 31 to 34 as the fixing belt 20 rotates, and moves along the slits 31 to 34 on the downstream side in the rotational direction and on the central side in the axial direction. Move to. Here, if we pay attention to the second slit 34 located at the outermost end in the axial direction in the non-opposing area 27B of the second sliding surface 27 (see the upper right diagram of FIG. 15), the lubricant is 34, and flows toward the center in the axial direction (see the broken line shown in the upper right diagram of FIG. 15). Since there is no blocking portion 42 corresponding to this second slit 34, the lubricant smoothly flows out from the outflow portion F2 of this second slit 34 (see the broken line shown in the upper right diagram of FIG. 15).

Thereafter, as the fixing belt 20 rotates, the lubricant is carried to the non-opposed area 26B of the first sliding surface 26, and is located on the axially inner side (second from the outermost end) of the non-opposed area 26B. It flows from the inflow part F1 of the first slit 33 and flows toward the center in the axial direction (see the broken line shown in the upper left diagram of FIG. 15). Since there is no blocking portion 41 corresponding to this first slit 33, the lubricant smoothly flows out from the outflow portion F2 of this first slit 33 (see the broken line shown in the upper left diagram of FIG. 15).

Thereafter, as the fixing belt 20 rotates, the lubricant is carried to the opposing area 27A of the second sliding surface 27, and flows into the inflow portion F1 of the second slit 32 located at the outermost end of the opposing area 27A. , flows toward the center in the axial direction (see the broken line shown in the lower right diagram of FIG. 15). Since a blocking part 42 is formed in this second slit 32, a part of the lubricant passes over the blocking part 42 and flows out from the outflow part F2, but the remaining lubricant is not blocked. 42 (see the broken line shown in the lower right figure of FIG. 15).

Thereafter, as the fixing belt 20 rotates, the lubricant is guided to move toward the center in the axial direction by the slits 31 to 34 (see the lower left diagram in FIG. 15). Note that the lubricant tends to move toward both outer sides in the axial direction in areas where the inner circumferential surface 20A of the fixing belt 20 is not in contact with the sliding surfaces 26 and 27, so all the lubricant is transferred to the axial direction. Rather than moving inward in the direction, some of the lubricant moves inward in the axial direction. In other words, the lubricant will not run out on both outer sides in the axial direction.

In the fixing device 7 according to the other modified example of the first embodiment described above, the blocking parts 41 and 42 are formed only in the opposing areas 26A and 27A, and on both outer sides in the axial direction including the opposing areas 26A and 27A. The outflow portion F2 and the inflow portion F1 of adjacent slits 31 to 34 are configured to overlap. According to this configuration, as the fixing belt 20 rotates, the lubricant can be efficiently brought to the center in the axial direction, and leakage of the lubricant from the outer end in the axial direction can be effectively suppressed. can.

In addition, in FIGS. 11 and 12, some of the slits 31 and 32 in the opposing regions 26A and 27A are inclined so that the outflow section F2 and the inflow section F1 overlap, but the present invention is not limited to this. Not done. At least, the slits 33 and 34 formed in the non-opposing areas 26B and 27B and the slits 31 and 32 formed at the outermost ends in the axial direction of the opposing areas 26A and 27A, respectively, when viewed from the rotation direction of the fixing belt 20. In this case, the outflow portion F2 may be inclined so as to overlap the inflow portions F1 of the other slits 31 to 34 adjacent to each other on the inner side in the axial direction. Furthermore, the features of the fixing device 7 according to other modified examples may be applied to the fixing device 7 according to the first embodiment (see FIGS. 4 and 5) excluding the modified example, and in this case, all the slits 31 to 34 may be inclined so that the outflow section F2 and the inflow section F1 overlap (not shown).

Furthermore, the features of the fixing device 7 according to other modifications may be applied to the fixing device 8 (see FIGS. 6 to 8) according to the second embodiment (not shown). That is, a plurality of first slits 33 are formed in the first sliding surface 26, a plurality of second slits 34 are formed in the second sliding surface 27, and opposing areas 26A, 27A of the sliding surfaces 26, 27 are formed. The blocking portions 43 and 44 protrude from only the non-opposing regions 26B and 27B, and the blocking portions 43 and 44 do not protrude (are not provided) from the respective non-opposing regions 26B and 27B. That is, the blocking portions 43 and 44 are preferably provided in protruding positions so as not to prevent the lubricant from flowing out from the slits 33 and 34 formed in the non-opposing regions 26B and 27B.

Furthermore, in the fixing devices 7 and 8 according to other modified examples, the second slits 32 and 34 (blocking portions 42 and 44) may be omitted (not shown). When the second slits 32 and 34 are not formed on the second sliding surface 27, focusing on the first slit 33 located at the outermost end in the axial direction of the non-opposing region 26B of the first sliding surface 26, the lubricant is , flows toward the center in the axial direction along the first slit 33 and flows out from the outflow portion F2 (see the upper diagram in FIG. 16). When the fixing belt 20 makes one revolution, the lubricant is again carried to the non-opposed area 26B of the first sliding surface 26, and is then transferred from the inlet F1 of the first slit 33 located inside the non-opposed area 26B in the axial direction. It flows in and flows out from the outflow portion F2 (see the middle diagram in FIG. 16). Furthermore, when the fixing belt 20 makes one revolution, the lubricant is carried to the opposing area 26A of the first sliding surface 26, and flows in from the inflow portion F1 of the first slit 31 located at the outermost end of the opposing area 26A. A part of the lubricant passes over the blocking part 41 and flows out from the outflow part F2 (see the lower diagram in FIG. 16). Thereafter, as the fixing belt 20 rotates, the lubricant is guided by the first slit 31 and moves toward the center in the axial direction.

Note that in the fixing devices 7 and 8 according to the first and second embodiments (including each modification; the same applies hereinafter), the axial intervals and widths of the slits 31 to 34 are approximately the same; It is not limited to this. For example, the spacing between the slits 31 to 34 may be narrower or wider near the ends than near the center in the axial direction. (not shown)

Note that in the fixing devices 7 and 8 according to the first and second embodiments, the blocking portions 41 to 44 were provided on both the upstream and downstream sliding surfaces 26 and 27, but the present invention is not limited to this. . In order to prevent the fixing belt 20 from waving, it is sufficient that the blocking portions 41 and 43 are provided at least on the first sliding surface 26 on the upstream side. For example, in the fixing device 7 according to the first embodiment, the second slit 34 of the fixing device 8 according to the second embodiment may be formed on the second sliding surface 27 instead of the second slit 32 (see FIG. (not shown).

Further, for example, the slits 31 and 32 and the blocking parts 41 and 42 of the fixing device 7 according to the first embodiment are provided on the first sliding surface 26 (or the second sliding surface 27), and The slits 33 and 34 and the blocking portions 43 and 44 of the fixing device 8 may be provided on the second sliding surface 27 (or the first sliding surface 26) (not shown).

Further, in the fixing devices 7 and 8 according to the first and second embodiments, the slits 31 to 34 are formed in a straight line, but the slits are not limited to this and may be curved (not shown). Further, although the slits 31 to 34 are inclined, they are not limited to this, and may be formed parallel to the rotational direction of the fixing belt 20 (or the passing direction of the paper P) (not shown).

In addition, in the description of the above embodiment, the case where the present invention is applied to the monochrome image forming apparatus 1 is shown as an example, but the present invention is not limited to this, and can be applied to, for example, a color printer, a copying machine, a facsimile machine, a multifunction machine, etc. The invention may be applied.

Note that the description of the above embodiments shows one aspect of the fixing device and image forming apparatus according to the present invention, and the technical scope of the present invention is not limited to the above embodiments. The present invention may be variously changed, replaced, and modified without departing from the spirit of the technical idea, and the scope of the claims includes all embodiments that can be included within the scope of the technical idea.

1 Image forming device 7, 8 Fixing device 20 Fixing belt 20A Inner peripheral surface 21 Pressure roller (pressure member)
22 Heater holder (holder)
23 Heater 26 First sliding surface (sliding surface)
27 Second sliding surface (sliding surface)
26A, 27A Opposing area 26B, 27B Non-opposing area 31, 33 First slit (slit)
31A, 32A, 33A, 34A Bottom surface 32, 34 2nd slit (slit)
31B, 32B, 33B, 34B Surrounding wall surface 31C, 32C, 33C, 34C Opening edge 41, 42, 43, 44 Blocking part F1 Inflow part F2 Outflow part N Pressure area P Paper (medium)

Claims (7)

a fixing belt formed in a flexible cylindrical shape and heating a toner image on a medium while rotating around an axis;
a pressure member that forms a pressure area between the fixing belt and the fixing belt while rotating around an axis, and presses the toner on the medium passing through the pressure area;
a holder that is provided inside the fixing belt, has a sliding surface that contacts the inner circumferential surface of the fixing belt via a lubricant, and holds a heater that heats the fixing belt;
The holder is
a plurality of slits that are arranged in the axial direction on the sliding surface upstream of the pressurizing area in the direction of passage of the medium and guide movement of the lubricant from upstream to downstream in the rotational direction of the fixing belt; ,
A fixing device comprising: a blocking portion that limits outflow of the lubricant from each of the slits and prevents the fixing belt from falling into each of the slits. Each of the slits has a bottom surface and a peripheral wall surface, and is recessed to form an annular opening edge on the sliding surface,
The fixing device according to claim 1, wherein the blocking portion includes a wall surface located on the downstream side in the rotational direction of the fixing belt among the peripheral wall surfaces of each of the slits. The fixing device according to claim 1, wherein the blocking portion includes a rib protruding from the sliding surface of the holder on a downstream side of the plurality of slits in the rotational direction of the fixing belt. . The fixing device according to claim 1, wherein each of the slits is inclined toward the center in the axial direction from upstream to downstream in the rotational direction of the fixing belt. The plurality of slits extend toward the center in the axial direction from upstream to downstream in the rotation direction of the fixing belt, except for at least one slit that extends parallel to the rotation direction of the fixing belt near the center in the axial direction. tilted,
The fixing device according to claim 1, wherein the inclination angle of the plurality of slits gradually increases from the center in the axial direction toward both outer sides. The slit has an inflow portion that allows the lubricant to flow in from an upstream side in the rotational direction of the fixing belt, and an outflow portion that allows the lubricant to flow out downstream in the rotational direction of the fixing belt,
The sliding surface includes a facing area that faces the medium with the fixing belt in between, and a pair of non-facing areas that are on both sides of the facing area in the axial direction and that do not face the medium with the fixing belt in between. having a region,
The blocking portion is formed only in the opposing area,
A plurality of the slits are formed in the facing area, and at least one slit is formed in each non-facing area,
At least, the slit formed in the non-opposing area and the slit formed at the outermost end in the axial direction of the opposing area respectively define the outflow portion when viewed from the rotational direction of the fixing belt. The fixing device according to claim 4 or 5, wherein the fixing device is inclined so as to overlap the inflow portion of the other slit adjacent to the inner side in the axial direction. An image forming apparatus comprising the fixing device according to claim 1.

Images