JP7115092B2 - Fixing device and image forming device - Google Patents

Description

The present invention relates to fixing devices and image forming apparatuses.

In image forming devices such as copiers, printers, and facsimiles, images are formed by image forming processes such as electrophotographic recording, electrostatic recording, and magnetic recording. It is formed on recording materials such as printing paper, photosensitive paper, and electrostatic recording paper. As a fixing device for fixing an unfixed toner image on a recording material, the toner image formed on the recording material is heated and pressed at a nip portion between an endless fixing belt and a pressure roller to perform fixing processing. The configuration is known (for example, Patent Document 1, etc.).

By configuring such a fixing device to heat the entire endless belt, it is possible to shorten the first print time from the time of waiting for heating, and to solve the problem of insufficient amount of heat during high-speed rotation. Therefore, even if it is installed in a high-production image forming apparatus, good fixability can be obtained.

By the way, in the fixing device, it is assumed that various types of recording materials are passed through. For example, the recording material is small in size (smaller than the heat generation width in the axial direction of the heating means for heating the endless belt), such as a letter. A recording material may be fed. In such a case, heat is not taken away from the non-paper-passing area of the endless belt due to the passage of paper, so the temperature of the non-paper-passing area rises due to excessive heat. As a result, there is a problem that deterioration of the fixing member including the endless belt progresses, shortening the life of the apparatus.

On the other hand, a configuration has been proposed in which a heat equalizing member made of a material having a high thermal conductivity is used as the nip forming member and brought into contact with the endless belt from the inner side to release the heat of the non-sheet-passing portion. However, in the fixing device with this configuration, the nip forming member and the fixing belt contact and slide, so that there are problems such as durability and temperature stability of the fixing belt.

To address this problem, for example, Patent Document 2 discloses a configuration in which a sliding sheet with low friction characteristics is provided on the surface of a nip forming member and a lubricant is applied to reduce the sliding load (torque). . As a result, with a simple configuration, it is possible to prevent the temperature from rising in the non-sheet-passing portion and ensure the durability and temperature stability of the fixing belt.

However, in the conventional structure in which the lubricant is applied to the sliding sheet, the lubricant is not applied to the edges of the sliding sheet due to variations in the weave direction of the sliding sheet and pressure deviation (unevenness of pressure in the longitudinal direction of the nip). may flow out of the If the lubricant flows out, the life of the driving system may be shortened due to an increase in the sliding load, or the linear speed fluctuation (slip) of the fixing belt may cause conveyance failure.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a fixing device that prevents lubricant from flowing out from the end of a sliding sheet.

The above-mentioned problems are solved by: a rotatable endless fixing belt; a heat source for heating the fixing belt; a pressure member that abuts on the outer peripheral surface of the fixing belt; A fixing device comprising a nip forming member forming a nip portion between itself and the pressure member, wherein the nip forming member includes a heat soaking member and a sliding sheet impregnated with a lubricant. The heat soaking member extends to the inside of the fixing belt on the contact portion that contacts the fixing belt via the sliding sheet, the inlet side and the outlet side of the nip portion in the conveying direction of the recording material. and a holding portion that hooks and holds the sliding sheet at the leading end of the bending portion located on the inlet side of the nip portion. The weave of the sliding sheet is held at the abutting portion of the heat equalizing member so as to move toward the center in the longitudinal direction as it progresses from the entrance to the exit of the nip portion . having a plurality of openings or recesses, wherein the heat equalizing member has a plurality of protrusions located toward the center in the longitudinal direction with respect to the respective positions of the plurality of openings or recesses, The fixing device is characterized in that the plurality of openings or recesses of the sliding sheet are fitted into the plurality of protrusions of the heat soaking member .

In the fixing device of the present invention, since the weave of the sliding sheet moves toward the center in the longitudinal direction as it progresses from the entrance to the exit of the nip portion at the contact portion of the heat equalizing member, the lubricant flows from the end portion of the heat equalizing member. You can prevent it from leaking.

1 is a schematic diagram showing a cross section of a color printer that is an embodiment of an image forming apparatus; FIG. 1 is a cross-sectional configuration diagram (part 1) showing a fixing device according to an embodiment of the present invention; FIG. 2 is a cross-sectional configuration diagram (part 2) showing a fixing device according to an embodiment of the present invention; FIG. 3 is a cross-sectional configuration diagram (part 3) showing a fixing device according to an embodiment of the present invention; FIG. FIG. 4 is an exploded view of a light shielding member according to one embodiment of the present invention; An arrangement example of a light shielding member is shown, the upper stage is a perspective view, and the lower stage is a cross-sectional configuration diagram. 1 is an exploded perspective view of a nip forming member according to one embodiment of the present invention; FIG. FIG. 4 is an enlarged perspective view of a nip forming member according to one embodiment of the present invention; FIG. 4 is a schematic diagram illustrating assembly of the sliding sheet to the heat equalizing member according to one embodiment of the present invention. It is a two-sided schematic diagram explaining the flow of the lubricant applied to the sliding sheet.

(embodiment)
FIG. 1 is a schematic diagram showing a cross section of a color printer which is an embodiment of an image forming apparatus. The present color printer employs a tandem system in which image forming units for forming a plurality of color images are arranged side by side along the stretching direction of the belt, but the present invention is not limited to this system. Moreover, it is possible to target not only printers but also copiers, facsimile machines, and the like.

As shown in FIG. 1, photoreceptors 20Y, 20C, 20M, and 20Bk, which are image carriers, are arranged side by side at the center of the image forming apparatus 1 . The photoreceptors 20Y, 20C, 20M, and 20Bk are capable of forming images corresponding to yellow (Y), cyan (C), magenta (M), and black (Bk), respectively. Since these image forming means have the same structure except for the difference in developer (toner) color, the suffixes Y, C, M and Bk in the reference numerals will be omitted as appropriate in the following description.

A charging member 30 , a developing device 40 and a cleaning means 50 are provided around each photoreceptor 20 . The photoreceptor 20 is driven to rotate clockwise, and the charging member 30 is pressed against the surface of the photoreceptor 20 . A predetermined bias voltage is applied to the charging member 30 by a high-voltage power supply, so that the surface of the rotating photoreceptor 20 can be uniformly charged. The photoreceptor 20 , charging member 30 , developing device 40 and cleaning means 50 are arranged detachably from the image forming apparatus 1 .

An exposure device 8 is provided obliquely below the four photoreceptors 20 and parallel to them. This exposure device 8 has constituent members such as a light source, a polygon mirror, an f-θ lens, and a reflecting mirror. The exposure device 8 exposes each photoreceptor 20 charged by the charging member 30 to form an electrostatic latent image on each photoreceptor 20 based on image information formed according to image data of each color toner. produce. The electrostatic latent image formed on the photoreceptor 20 by using the exposure device 8 is developed by applying toner of each color when passing through the developing device 40 as the photoreceptor 20 rotates, and is visualized. .

Toner bottles 9Y, 9C, 9M, and 9Bk filled with yellow, cyan, magenta, and black toners are arranged in the upper part of the image forming apparatus 1 . A predetermined supply amount of toner is supplied from these toner bottles 9Y, 9C, 9M and 9Bk to the developing devices 40Y, 40C, 40M and 40Bk of each color through a transport path (not shown).

Further, an endless belt-like intermediate transfer belt 11 configured as an intermediate transfer member is disposed facing the photoreceptors 20 of each image forming means, and each photoreceptor 20 is in contact with the surface of the intermediate transfer belt 11 . ing. The intermediate transfer belt 11 is wound around a plurality of support rollers (for example, support rollers 72 and 73). In the illustrated example, the support roller 73 is connected to a drive motor (not shown) as a drive source. Driven by this drive motor, the intermediate transfer belt 11 rotates counterclockwise in the figure, and is driven accordingly. A rotatable support roller 73 also rotates. A primary transfer roller 12 is arranged inside the intermediate transfer belt 11 so as to face the photosensitive member 20 with the belt interposed therebetween. A primary transfer bias is applied to the primary transfer roller 12 from a high-voltage power supply, and the toner image visualized by the developing device 40 is primarily transferred to the intermediate transfer belt 11 .

The primary transfer residual toner left on the photoreceptor 20 without being primarily transferred is removed by the cleaning means 50 in preparation for the next image forming operation by the photoreceptor 20, and the toner on the photoreceptor 20 is completely removed. removed.

Further, a secondary transfer roller 5 as a secondary transfer device is provided on the downstream side of the intermediate transfer belt 11 in the driving direction. The secondary transfer roller 5 faces the support roller 72 with the intermediate transfer belt 11 interposed therebetween, and the secondary transfer roller 5 and the support roller 72 form a secondary transfer nip with the intermediate transfer belt 11 interposed therebetween. ing. The image forming apparatus 1 also includes a sheet feeding device 61 as a stacking unit for sheets S as recording materials, a feeding roller 3, and a pair of registration rollers 4 and the like. Further, a fixing device 100 and a pair of discharge rollers 7 are provided downstream of the secondary transfer roller 5 in the direction in which the sheet S is conveyed.

Next, the image forming operation will be described. First, the photoreceptor 20 is rotationally driven clockwise by the drive source, and at this time, the surface of the photoreceptor 20 is irradiated with light from a static elimination device (not shown) to initialize the surface potential. Next, the surface of the photoreceptor 20 is uniformly charged to a predetermined polarity by the charging member 30 . Next, the surface of the photoreceptor 20 is irradiated with laser light from the exposure device 8 to form an electrostatic latent image on the surface of the photoreceptor 20 . The image information exposed to each photosensitive member 20 at this time is monochrome image information obtained by decomposing a desired full-color image into yellow, cyan, magenta, and black toner color information. The electrostatic latent image formed on the photoreceptor 20 is applied with toner (developer) of each color from the developing device 40 when passing through the developing device 40, and is visualized as a visualized toner image.

The intermediate transfer belt 11 is driven to run counterclockwise in the drawing, while a primary transfer voltage having a polarity opposite to the toner charging polarity of the toner image formed on the photosensitive member 20 is applied to the primary transfer roller 12 . be done. As a result, a transfer electric field is formed between the photoreceptor 20 and the intermediate transfer belt 11, and the toner image on the photoreceptor 20 is electrostatically transferred onto the intermediate transfer belt 11, which is rotationally driven in synchronization with the photoreceptor 20. primary transfer. In this way, the primary-transferred toner images of the respective colors are successively superimposed on the intermediate transfer belt 11 from the upstream side in the conveying direction of the intermediate transfer belt 11, and a desired full-color image is formed.

On the other hand, the sheets S on which an image is to be formed are separated sheet by sheet from the sheet stack stacked in the sheet feeding device 61 and fed to the registration roller pair 4 by a transporting member such as the feeding roller 3 . At this time, the leading edge of the conveyed sheet S abuts against the nip portion of the registration roller pair 4 which has not yet started to rotate, forms a loop, and the registration of the sheet S is performed. Thereafter, the rotation of the registration roller pair 4 is started in synchronization with the full-color toner image carried on the intermediate transfer belt 11, and the secondary transfer nip portion formed by the support roller 72 and the secondary transfer roller 5 is started. The sheet S is sent out toward .

In this embodiment, the secondary transfer roller 5 is applied with a transfer voltage having a polarity opposite to that of the toner image formed on the surface of the intermediate transfer belt 11, thereby transferring the full-color toner image formed on the surface of the intermediate transfer belt 11 to the sheet S. It is transcribed all at once on top. Next, the sheet S having the toner image transferred thereon is conveyed to the fixing device 100, and is subjected to heat and pressure while passing through the fixing device 100, so that the toner image is fixed onto the sheet S as a permanent image. Then, the paper S is discharged to a paper discharge section such as a paper discharge tray 17 via the paper discharge roller pair 7, and the image forming operation is completed. Residual toner remaining on the intermediate transfer belt 11 without being transferred at the secondary transfer nip portion is removed and collected by the intermediate transfer belt cleaning means 13 .

The above description is for the image forming operation when forming a full-color image on the sheet S. However, any one of the photoreceptors 20 may be used to form a monochrome image, or to form a two- or three-color image. can also be formed. When the printer of the present embodiment is used for monochrome printing, an electrostatic latent image is formed only on the photosensitive member 20Bk, developed by the same means, transferred to the sheet S, and fixed by the fixing device 100. Just do it.

FIG. 2 is a cross-sectional configuration diagram (No. 1) showing a fixing device according to an embodiment of the present invention. The fixing device 100 includes a rotatable endless fixing belt 81 , a heat source 82 (halogen heater) that heats the fixing belt 81 , and a pressure roller 83 that is a pressure member that contacts the outer peripheral surface of the fixing belt 81 . Prepare. A nip forming member 86 that indirectly slides on the inner surface of the fixing belt 81 via a sliding sheet is provided in the fixing belt 81 . The nip forming member 86 forms a nip portion N together with the pressure roller 83 facing the fixing belt 81 .

Although the nip portion N has a flat shape in FIG. 2, it may have a concave shape or other shapes. When the nip portion N has a concave shape, the discharge direction of the leading edge of the recording material is closer to the pressure roller 83, and the separability is improved, thereby suppressing the occurrence of a jam.

The fixing belt 81 can be a metal belt such as nickel or SUS, an endless belt using a resin material such as polyimide, or a film. The surface layer of the fixing belt 81 has a release layer such as a PFA or PTFE layer, and has release properties so that toner does not adhere.

It is desirable that an elastic layer formed of a silicone rubber layer or the like is provided between the base material of the fixing belt 81 and the PFA or PTFE layer. Without the silicone rubber layer, the heat capacity is reduced and the fixability is improved. However, when the unfixed image is crushed and fixed, minute unevenness on the belt surface may be transferred to the image, leaving uneven luster (citron skin image) in the solid portion of the image. In order to improve this, a silicone rubber layer having a thickness of 100 μm or more may be provided. Deformation of the silicone rubber layer absorbs fine irregularities, thereby improving the orange peel image.

A support member 87 (stay) for supporting the nip portion N is provided inside the fixing belt 81 . This prevents the nip forming member 86 from bending due to the pressure of the pressure roller 83, and obtains a uniform nip width in the axial direction. Both ends of the support member 87 are held and fixed by holding members 88 (flanges) and positioned. Furthermore, a reflecting member 89 is provided between the heat source 82 and the support member 87 to suppress wasteful energy consumption due to heating of the support member 87 by radiant heat from the heat source 82 . Here, instead of providing the reflecting member 89, the surface of the supporting member 87 may be heat-insulated or mirror-finished to obtain the same effect.

The heat source 82 may be the illustrated halogen heater, but may also be an IH, a resistance heating element, a carbon heater, or the like.

The pressure roller 83 has a metal core 84 and an elastic rubber layer 85, and is provided with a release layer (PFA or PTFE layer) on the surface to obtain release properties. The pressure roller 83 rotates when a driving force is transmitted through a gear from a driving source such as a motor provided in the image forming apparatus 1 . The pressure roller 83 is pressed against the fixing belt 81 by a spring or the like, and the elastic rubber layer 85 is crushed and deformed to have a predetermined nip width. The pressure roller 83 may be a hollow roller, and may have a heating source such as a halogen heater inside the pressure roller 83 .

The elastic rubber layer 85 may be solid rubber, but if there is no heat source inside the pressure roller 83, sponge rubber may be used. Sponge rubber is more desirable because it has a higher heat insulating property and makes it more difficult for the fixing belt 81 to lose heat.

When the pressure roller 83 is rotated by the driving source, the driving force is transmitted to the fixing belt 81 at the nip portion N, so that the fixing belt 81 rotates together. The fixing belt 81 rotates while being nipped by the nip portion N, and runs while being guided by the holding members 88 (flanges) at both end portions other than the nip portion N. As shown in FIG.

With the configuration as described above, it is possible to realize a fixing device that is inexpensive and warms up quickly.

FIG. 3 is a cross-sectional configuration diagram (No. 2) showing a fixing device according to an embodiment of the present invention. In FIG. 3, the same reference numerals are assigned to the same components as in FIG. 2, and detailed description thereof will be omitted.

In the embodiment shown in FIG. 2, the heat source 82 is composed of one halogen heater, whereas in this embodiment, the heat source 82a is composed of three halogen heaters in order to accommodate the paper width. Since each of the three halogen heaters has a different light emitting position, it is possible to select the heater to be turned on according to the size of the recording material, and heat the fixing belt 81 in the corresponding range. As a result, productivity can be improved and energy saving can be achieved.

FIG. 4 is a cross-sectional configuration diagram (No. 3) showing a fixing device according to an embodiment of the present invention. In FIG. 4, the same components as in FIGS. 2 and 3 are denoted by the same reference numerals, and detailed description thereof will be omitted.

A fixing device 100b shown in FIG. 4 has a configuration in which a light blocking member 90 is added to the configuration of FIG. The light shielding member 90 has a stepped shape as shown in FIG. 5, and has a light shielding area corresponding to the size (paper width) of the recording material.

FIG. 6 shows an arrangement example of the light shielding member, the upper stage is a perspective view, and the lower stage is a cross-sectional view. (a) is an example in which an A3 size recording material is passed, and (b) is an example in which a postcard size recording material is passed. The light shielding member 90 rotates along the inside of the fixing belt 81 in a non-contact manner to a position corresponding to each paper width, and shields an area unnecessary for heating from light.

By shielding the light with the light shielding member 90, the temperature of the non-paper-passing area does not rise excessively even when the recording material having a narrow paper width is continuously passed. In addition, it is not necessary to reduce productivity in order to suppress excessive temperature rise. Here, the "non-paper-passing area" means an area through which the recording material having the maximum width (recording material having the maximum paper width) does not pass among the recording materials used in the fixing device. Also, by providing the light shielding member 90, the number of halogen heaters constituting the heat source 82b can be reduced (the heat source 82b in this embodiment is two halogen heaters).

FIG. 7 is an exploded perspective view of a nip forming member according to one embodiment of the present invention. This configuration aims to reduce the excessive temperature rise in the non-sheet-passing area, and has a function of reducing the number of heat sources (reducing the number of halogen heaters to two) and a function of substituting the light shielding member 90 . Therefore, the light shielding member 90 and the drive unit for driving it are not required, and the cost can be greatly reduced.

The nip forming member 86 includes, as shown in FIG. 7, a heat soaking member 66 as a first heat transfer means and a sliding sheet 67 provided on the heat soaking member 66 . When the fixing belt 81 rotates, the fixing belt 81 slides on the sliding sheet 67 , thereby reducing the driving torque generated in the fixing belt 81 and reducing the load of the fixing belt 81 due to the frictional force. be.

The heat soaking member 66 is made of a material with high thermal conductivity, such as copper, and is formed along the longitudinal direction of the fixing belt 81 . Then, it is possible to absorb the heat excessively accumulated in the non-sheet passing portion of the fixing belt 81 and move the heat in the longitudinal direction.

FIG. 8 is an enlarged perspective view of a nip forming member according to one embodiment of the invention. As shown in FIG. 8, the heat equalizing member 66 has a contact portion 66a that contacts the fixing belt 81 via the sliding sheet 67, and a bent portion 66b that is located on the inlet side of the nip portion N in the sheet S transport direction. , and a bend 66c on the exit side of the nip N. The bent portions 66b and 66c are formed to extend inside the fixing belt 81, respectively.

The tip of the bent portion 66b on the entrance side of the nip portion N has a holding portion 66d for holding the sliding sheet 67 thereon. The holding portion 66d has a plurality of sharp protrusions, and even if the sliding sheet 67 is pulled in the sliding direction when the fixing belt 81 rotates, the holding portion 66d holds the sliding sheet 67. .

The holding portion 66d has a plurality of sharp protrusions, and the protrusions do not have to penetrate the sliding sheet 67 as long as the nip portion N can be properly formed. If it is through, the holding force against rotational pull is stronger. Further, in the case of a specification in which the fixing belt 81 rotates in the reverse direction, it is effective to provide a similar holding portion at the tip of the bent portion 66c.

Returning to FIG. 7, the description is continued. As shown in FIG. 7, the nip forming member 86 has a first heat insulating member 77a, a second heat insulating member 77b, a first heat absorbing member 76, and a second heat absorbing member 75. As shown in FIG. The first heat insulating member 77 a is made of, for example, a resin having a lower thermal conductivity than the heat soaking member 66 , extends partially in the longitudinal direction of the fixing belt 81 , and extends between the heat soaking member 66 and the second heat absorbing member 75 . , are arranged at positions where the first heat absorbing member 76 does not exist. Excessive absorption of heat from the fixing belt 81 is avoided by having the first heat insulating member 77a. As a result, it is possible to prevent the temperature drop in the paper passing portion. Also, the warm-up time can be shortened and the power consumption can be reduced.

The second heat insulating member 77 b is made of, for example, resin having a lower thermal conductivity than the heat equalizing member 66 and is provided between the heat equalizing member 66 and the first heat absorbing member 76 . By providing the second heat insulating member 77b, the amount of heat transfer from the heat equalizing member 66 to the second heat absorbing member 75 via the first heat absorbing member 76 can be reduced.

If the thickness of the second heat insulating member 77b is too large, the heat accumulated in the fixing belt 81 will not move to the second heat absorbing member 75, so that the temperature of the non-sheet-passing portion is likely to rise. Therefore, the thickness and length of the second heat insulating member 77b must be optimized according to the magnitude of the temperature rise in the non-sheet-passing portion that occurs, but the thickness is smaller than the thickness of the first heat insulating member 77a.

The second heat absorbing member 75 is made of a material having higher thermal conductivity than the first heat insulating member 77a and the second heat insulating member 77b, extends in the longitudinal direction of the fixing belt 81, and extends between the first heat insulating member 77a and the first heat insulating member 77b. 76 is disposed in contact therewith.

The first heat absorbing member 76 is also made of a material having a higher thermal conductivity than the first heat insulating member 77a and the second heat insulating member 77b. It is arranged between the two heat absorbing members 75 . In particular, the first heat-absorbing member 76 is provided at a position corresponding to an area other than the central region of the fixing belt 81 , that is, at a position where the temperature of the non-sheet-passing portion of the fixing belt 81 is increased.

In the present embodiment, the first heat absorbing member 76 is provided corresponding to the paper non-passage area, but is not limited to this aspect. It may be provided by extending to the position.

The heat equalizing member 66 has a function of facilitating heat transfer in the longitudinal direction, equalizing the heat of the fixing belt 81, and suppressing an increase in the temperature of the non-sheet-passing portion. On the other hand, the first heat absorbing member 76 and the second heat absorbing member 75 have a role of promoting heat transfer in the thickness direction and absorbing heat. That is, the first heat absorbing member 76 and the second heat absorbing member 75 compensate for the insufficient heat capacity of the heat equalizing member 66. In particular, the second heat absorbing member 75 has a large heat capacity or a large surface area to increase heat dissipation. It is desirable to have

The heat-absorbing member, the heat-insulating member, and the bent portions 66b and 66c sandwich the end regions of the sliding sheet 67 in the sliding direction, so that the sliding sheet 67 can be fixed more firmly. Also, it is possible to prevent the temperature drop in the paper passing portion. Furthermore, the warm-up time can be shortened and the power consumption can be reduced.

Next, a characteristic configuration of the present invention will be described.

Generally, in order to improve the durability of the fixing belt 81, the sliding sheet 67 is made of a material with low friction properties and is often coated with a lubricant. A low-viscosity material is used as the lubricant, but since it has high fluidity, it tends to flow out from the fixing belt 81, and there is a problem that the sliding load (torque) increases.

Also, the lubricant applied to the sliding sheet 67 tends to flow in one direction due to the nip deviation in the longitudinal direction, the texture direction of the sliding sheet 67, and the like. Here, the nip deviation is a pressure deviation caused by a static load deviation during pressurization or a dynamic load deviation during driving by a one-sided drive system.

If the lubricant is partially depleted in the longitudinal direction of the sliding sheet 67, linear velocity fluctuations of the fixing belt 81 in the longitudinal direction (frictional fluctuations between the fixing belt 81 and the sliding sheet 67) occur, resulting in conveyance failure such as wrinkling of the recording material. occurs. Furthermore, since the deviation speed of the fixing belt 81 also increases, the load on the end surface of the fixing belt 81 increases, and there is also the problem that the life of the fixing belt 81 is shortened.

In consideration of this flow direction, Patent Document 3 discloses a configuration in which the initial amount of impregnated lubricant is varied in the longitudinal direction. However, since the total amount of lubricant increases, the amount of lubricant that flows out also increases, making it easier for the lubricant to transfer (stain) to other parts. In addition, due to variations in the weave of the sliding sheet 67, the outflow of the lubricant also varies.

FIG. 9 is a schematic diagram illustrating the assembly of the sliding sheet to the heat equalizing member according to one embodiment of the present invention, and FIG. It is a schematic diagram.

As shown in FIG. 9, a plurality of openings 67a (or recesses) are provided in the longitudinal direction of the sliding sheet 67, and a plurality of projections 68 are provided at the tip of the bent portion 66c of the heat soaking member 66. As shown in FIG. Here, the plurality of projections 68 are located closer to the center in the longitudinal direction than the respective positions of the plurality of openings 67a (or recesses). A plurality of openings 67a (or recesses) of the sliding sheet 67 are fitted to a plurality of projections 68, respectively.

As a result, the sliding sheet 67 is assembled toward the center in the longitudinal direction from the entrance of the nip portion N toward the exit, as shown in FIG. That is, the sliding sheet 67 is held by the contact portion 66a of the heat soaking member 66 such that the weave t moves toward the central portion in the longitudinal direction as it proceeds from the entrance to the exit of the nip portion N. As shown in FIG.

The texture t directed toward the longitudinal center of the heat equalizing member 66 forms a flow path for moving the lubricant impregnated in the sliding sheet 67 to the longitudinal center of the heat equalizing member 66 at the contact portion 66 a of the heat equalizing member 66 . It is possible to prevent the lubricant from flowing out from the end of the Therefore, it is possible to reduce the sliding load (torque), prolong the life of the drive system, and prevent defective conveyance due to linear velocity fluctuations (fixing sleeve slip). Furthermore, transfer (dirt) of the lubricant to other parts can be prevented.

Since a force acts on the sliding sheet 67 in the conveying direction, if the holding force at the entrance of the nip portion N is weak, the sliding sheet 67 will come off, causing an increase in the sliding load (torque) and damage to the unit. As described above, the sliding sheet 67 is fixed by penetrating the tip of the bent portion 66b of the heat soaking member 66 having a sharp tip. Therefore, if the opening 67a and the convex portion 68 are provided at the nip entrance, the penetrating portion between the sliding sheet 67 and the heat soaking member 66 (bent portion 66b) is reduced, and the holding force of the sliding sheet 67 is reduced. In addition, there is a possibility that the slide sheet 67 is torn starting from the opening 67a.

Therefore, it is preferable that the opening 67a and the projection 68 are provided only at the nip outlet (the bent portion 66c). Moreover, it is preferable that the amount of assembling of the sliding sheets 67 is not uniform at each position, but is changed according to the configuration such as one-side driving.

The present invention has been described in detail above using the embodiments. This embodiment is an example, and can be used with various modifications within the scope of the invention. Moreover, as the fixing device and the image forming apparatus, any configuration can be adopted as long as the present invention can be applied. The image forming apparatus is not limited to a copier or printer, and may be a facsimile machine or a multifunction machine having multiple functions.

1 Image forming device 3 Feeding roller 4 Registration roller pair 5 Secondary transfer roller 7 Discharge roller pair 8 Exposure device 9Y, 9M, 9C, 9Bk Toner bottle 11 Intermediate transfer belt 12Y, 12M, 12C, 12Bk Primary transfer roller 13 Intermediate Transfer Belt Cleaning Means 17 Discharge Tray 20Y, 20M, 20C, 20Bk Photoreceptor 30Y, 30M, 30C, 30Bk Charging Member 40Y, 40M, 40C, 40Bk Developing Device 50Y, 50M, 50C, 50Bk Cleaning Means 61 Sheet Feeding Device 66 Heat equalizing member 66a Abutting portion 66b, 66c Bent portion 66d Holding portion 67 Sliding sheet 67a Opening 68 Convex portion 72, 73 Support roller 75 Second heat absorbing member 76 First heat absorbing member 77a First heat insulating member 77b Second heat insulating member 81 fixing belt 82, 82a, 82b heat source 83 pressure roller 84 core metal 85 elastic rubber layer 86 nip forming member 87 supporting member 88 holding member 89 reflecting member 90 light shielding member 100, 100a, 100b fixing device N nip portion S paper (recording material)
t texture

Japanese Patent Application Laid-Open No. 2007-334205 JP 2016-033636 A JP 2016-177078 A

Claims (5)

A rotatable endless fixing belt, a heat source for heating the fixing belt, a pressure member in contact with the outer peripheral surface of the fixing belt, and the fixing belt and the pressure member disposed inside the fixing belt. A fixing device comprising a nip forming member that forms a nip portion between
The nip forming member comprises a heat equalizing member and a sliding sheet impregnated with a lubricant,
The heat equalizing member extends inside the fixing belt at a contact portion that contacts the fixing belt via the sliding sheet, and at an entrance side and an exit side of the nip portion in the conveying direction of the recording material. a bent portion;
In a fixing device having a holding portion that hooks and holds the sliding sheet at the tip of the bent portion on the entrance side of the nip portion,
The sliding sheet is held so that the texture of the sliding sheet is directed toward the center in the longitudinal direction as it progresses from the entrance to the exit of the nip portion at the contact portion of the heat equalizing member. The moving sheet has a plurality of openings or recesses in the longitudinal direction,
the heat equalizing member has a plurality of protrusions in the bent portion positioned closer to the center in the longitudinal direction than the respective positions of the plurality of openings or recesses;
A fixing device , wherein the plurality of openings or recesses of the sliding sheet are fitted into the plurality of protrusions of the heat soaking member .

2. The fixing device according to claim 1 , wherein the weave of the sliding sheet forms a flow path for moving the lubricant impregnated in the sliding sheet to the central portion in the longitudinal direction. 3. The fixing device according to claim 1, wherein the heat equalizing member has the plurality of convex portions at the bent portion on the exit side of the nip portion in the conveying direction of the recording material. 4. The holding portion according to any one of claims 1 to 3 , wherein the holding portion has a plurality of sharp projections, and at least a part of the projections penetrates the sliding sheet. Fixing device. An image forming apparatus comprising the fixing device according to claim 1 .

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