JP2023059000A - Sheet conveying device and image forming apparatus - Google Patents

Abstract

To provide a sheet conveying device using an endless belt, and even when floating of the endless belt occurs, prevent occurrence of scratches due to contact with a paper feed guide.SOLUTION: A sheet conveying device brings a long-sized support and a rotating body into pressure contact with each other and sandwiches an endless belt therebetween to form a nip part, and feeds a sheet to the nip part to convey the sheet, and the sheet conveying device comprises a belt-side paper feed guide 36 that is on a downstream side of the nip part in a sheet feeding direction and guides the sheet ejected from the nip part closer to the endless belt. The belt-side paper feed guide 36 is formed by providing, on the side of a sheet guide surface, a plurality of ribs 362 extending along a sheet conveyance direction in parallel in a direction orthogonal to the sheet conveyance direction. At tips on a nip side of the plurality of ribs 362, belt protection members 363 having at least a same height as the tips of the ribs and a wider width than the tips of the ribs are disposed along an edge 3611 on the nip side of the belt-side paper feed guide 36.SELECTED DRAWING: Figure 3

Description

The present disclosure relates to a sheet conveying device having an endless belt and an image forming apparatus having the sheet conveying device.

An electrophotographic image forming apparatus includes a fixing device that thermally fixes a sheet on which an unfixed toner image is formed by passing the sheet through a nip formed between a heating rotator and a pressurizing rotator.

In recent years, from the viewpoint of energy saving, a fixing belt (endless belt) is stretched between a heating roller, which is a heat source, and an elongated support such as a support pad or a support roller (fixing roller). A belt-type fixing device, in which a support is sandwiched between a pressure roller and a nip portion is formed, is widely used.

The fixing belt is mainly made of metal or resin material, and is relatively thin, which reduces heat capacity. This shortens the time it takes to raise the temperature from the start-up or standby state to the fixing temperature, which saves energy. because it contributes to

FIG. 11 is a cross-sectional view showing an example of the configuration of a conventional fixing device using a fixing belt. As shown in the figure, a fixing belt 531, a pressure roller 532, a fixing pad 533, a heating roller 534, and the like are arranged in a housing 538 of the fixing device.

The fixing belt 531 is stretched between a fixing pad 533 and a heating roller 534, and a portion of the fixing belt 531 corresponding to the fixing pad 533 is pressed by the pressure roller 532 to form a nip portion Np.

The pressure roller 532 is rotationally driven in the direction of arrow Q by a drive source (not shown), the fixing belt 531 runs in the direction of arrow P, and the heating roller 534 also rotates following the fixing belt 531 .

A heater 535 is built in the heating roller 534 to heat the fixing belt 531 . A recording sheet on which an unfixed toner image is formed is passed through the nip portion Np and thermally fixed.

On the downstream side of the nip portion Np in the sheet passing direction (the direction from the bottom to the top in FIG. 11), a pair of sheet passing guides guide the sheet that has passed through the nip portion Np toward the exit 539 of the housing 538 of the fixing device. Guides 536, 537 are provided.

FIG. 12(a) is an external perspective view of the sheet passing guide 536 as seen from the right direction in FIG. 11 and slightly forward.

As shown in the figure, the sheet passing guide 536 has a plurality of ribs 5362 on the surface of a plate-like guide body 5361 that is elongated in the width direction of the fixing belt 531 (the direction perpendicular to the running direction) and faces the sheet. , are erected in parallel with the sheet passing direction.

FIG. 12(b) is an enlarged view of a portion surrounded by a semicircular dashed line J5 in FIG.

Since the rib 5362 is provided to reduce the contact area with the sheet and guide the sheet toward the discharge port of the housing 538, the width W11 is as thin as about 1 mm and the height H11 is also about 2 mm. is designed to

The lower end of the rib 5362 scoops up the leading edge of the sheet that has passed through the nip portion Np in close contact with the fixing belt 531 at a position separated from the fixing belt 531 by the stiffness of the sheet and guides the sheet upward. It is arranged close to the surface of the belt 531 .

JP-A-2004-93582

However, when the fixing belt 531 is rotated, especially when the image forming apparatus is turned on and started at the beginning of the day, the pressure roller 532 is applied when the fixing belt 531 is not sufficiently heated yet. When the fixing belt 531 is rotated, the rigidity of the fixing belt 531 is still high, and the rotation torque becomes unstable due to the effects of static friction in the bearing of the heating roller 534, and the behavior of the fixing belt 531 also becomes unstable. , the fixing belt 531 on the downstream side of the fixing nip Np may float (portion of broken line 531a in FIG. 11; hereinafter referred to as "belt float").

If the belt lifts even a little, the fixing belt 531 comes into contact with the lower end portion (the end portion on the nip portion Np side) of the sheet passing guide 536 arranged close to the fixing belt 531 .

As described above, since the width W11 of the rib 5362 is not so large, when the fixing belt 531 contacts the lower end portion of the rib 5362, particularly the corner portion 5362a (FIG. 12B), as shown in FIG. In addition, a large number of fine scratches 531b are generated on the surface of the fixing belt 531, and as a result, glossy streaks and the like are generated in the fixed image, resulting in deterioration of the image quality.

In order to solve such a problem, for example, in Patent Document 1, a drive roller is brought into contact with a fixing roller through a fixing belt on the downstream side of the nip portion Np in the paper passing direction, and the peripheral speed of the drive roller is set to fix the fixing roller. A configuration has been proposed in which the fixing belt is rotated so as to be faster than the circumferential speed of the belt and tension is applied to the fixing belt in a direction in which the belt lift is eliminated, thereby suppressing the belt lift.

However, if the drive roller is provided separately as in Patent Document 1, the size of the device increases, the number of parts increases, and the manufacturing cost increases.

The problem of preventing deterioration of the belt due to contact with the ribs of the paper-passing guide is not limited to the fixing device as described above. This problem commonly occurs in general sheet conveying apparatuses having a structure in which a sheet passing guide is arranged in the vicinity of the endless belt on the downstream side of the nip portion.

The present disclosure has been made in view of the circumstances described above, and is directed to a sheet conveying apparatus having an endless belt, which does not require an increase in the size of the apparatus, has a simple configuration that is less costly, and can be used even if the belt floats. SUMMARY OF THE INVENTION It is an object of the present invention to provide a sheet conveying device capable of preventing a belt from being damaged, and an image forming apparatus having the sheet conveying device.

In order to achieve the above object, a sheet conveying apparatus according to an aspect of the present disclosure forms a nip portion by pressing and holding an endless belt between a long support member and a rotating member, and passes a sheet through the nip portion. The sheet conveying device includes a guide member for guiding the sheet discharged from the nip portion toward the endless belt, the guide member being disposed on the sheet guide surface side of the guide main body in the sheet conveying direction. A plurality of ribs extending along the sheet are arranged in parallel in a direction orthogonal to the sheet conveying direction, and at least the tip end portions of the ribs are positioned at a position closer to the nip portion than the tip end portions of the plurality of ribs on the nip side. A belt protection member having the same height as the guide body and having a wider width than the tip is provided along the nip side edge of the guide body.

Further, in one aspect of the present disclosure, the belt protection member is formed to be continuous along the nip-side edge of the guide body.

In one aspect of the present disclosure, the belt protection member is divided along the nip-side edge of the guide body and provided in plurality.

In one aspect of the present disclosure, the tip of the rib and the belt protection member are integrally formed, and the tip of the rib on the nip side is connected to the belt protection member to form a T-shape and/or be adjacent to the belt protection member. The ends of the two ribs on the nip side are connected to each other through a belt protection member to form a U-shape.

Further, in one aspect of the present disclosure, in a state where the endless belt does not float, the distance between the surface of the belt protection member facing the endless belt and the surface of the endless belt is equal to the nip between the facing surfaces. The belt protection member is arranged such that a second position farthest from the nip portion is larger than a first position closest to the nip portion.

In one aspect of the present disclosure, the guide member is formed by injection molding, and the mold for injection molding has a mold split at a position corresponding to the second position.

Another aspect of the present disclosure is a sheet conveying device in which an endless belt is pressed and held between a long support member and a rotating member to form a nip portion, and a sheet is passed through the nip portion to be conveyed. and a guide member for guiding the sheet discharged toward the endless belt from the nip portion, the guide member having a plurality of ribs extending along the sheet conveying direction on the sheet guide surface side of the guide body, The plurality of ribs arranged side by side in a direction perpendicular to the sheet conveying direction have a width of 6 mm or more and 11 mm or less in the direction perpendicular to the sheet conveying direction at the nip side tip end portions of the plurality of ribs.

Further, according to one aspect of the present disclosure, the endless belt is a fixing belt, and heating means for heating the fixing belt is provided.

Further, according to one aspect of the present disclosure, the endless belt is an image carrying belt that carries a toner image, and the rotating body moves the toner image carried on the surface of the image carrying belt between the image carrying belt and the rotating body. It is a transfer roller that transfers the image to the sheet that is passed through the nip portion.

Another aspect of the present disclosure is an image forming apparatus including the sheet conveying device.

According to the configuration of the sheet conveying device according to the aspect of the above disclosure, even if belt floating occurs in the endless belt, belt protection with a larger contact area with the endless belt than the end surface of the lower end portion of the rib of the conventional paper-passing guide. Since the member is provided, the surface of the endless belt is less likely to be damaged. In addition, since there is no need to provide a drive roller for preventing the belt from lifting as in Patent Document 1, the device does not become large, and the structure is simple and the cost burden is small.

1 is a schematic diagram showing an overall configuration of a printer including a fixing device according to one aspect of the present disclosure; FIG. 3 is a cross-sectional view showing the structure of a fixing section of the printer; FIG. 1A is a perspective view of a first embodiment of a belt-side sheet passing guide in a fixing device according to one aspect of the present disclosure, and FIG. 1B is a partially enlarged view thereof; FIG. FIG. 10 is a diagram for explaining the effects of the belt-side paper-passing guide; (a) is a perspective view of a second embodiment of a belt-side paper-passing guide in a fixing device according to one aspect of the present disclosure, and (b) is a partially enlarged view thereof. (a) is a perspective view of a third embodiment of a belt-side paper-passing guide in a fixing device according to one aspect of the present disclosure, and (b) is a partially enlarged view thereof. (a) is an explanatory diagram of mold division when injection-molding a belt-side sheet passing guide according to the present disclosure, and (b) is an explanation of mold division when injection-molding a conventional belt-side sheet passing guide. It is a diagram. FIG. 4 is a diagram for explaining the size of a gap between a belt protection member of a belt-side paper-passing guide and a fixing belt according to the present disclosure; (a) is a perspective view of a modified example of a belt-side sheet passing guide in a fixing device according to an aspect of the present disclosure, and (b) is a partially enlarged view thereof. FIG. 10 is a diagram showing a modification in which the configuration of the sheet conveying device according to the aspect of the present disclosure is applied to the secondary transfer section; FIG. 10 is a diagram for explaining problems in a conventional belt-type fixing device; (a) is a perspective view of a belt-side paper-passage guide in the conventional fixing device, (b) is a partially enlarged view, and (c) shows an example of scratches generated on the surface of the fixing belt. It is a diagram.

In the following, a fixing device to which the structure of the sheet conveying device according to the aspect of the present disclosure is applied, and a tandem color printer (hereinafter simply referred to as “printer”) as an example of an image forming apparatus having the fixing device are shown in the drawings. I will explain based on.

(1) Overall Configuration of Printer FIG. 1 is a schematic cross-sectional view showing the overall configuration of a printer 1. As shown in FIG.

As shown in the figure, the printer 1 is of the electrophotographic type, and includes a feeding section 10, an image forming section 20, a fixing section 30, a discharge section 40 and a double-sided conveying section 50, and a recording sheet S for recording. A single-sided print job for printing an image on only one side (front side) and a double-sided print job for printing an image on both sides (front side and back side) of the recording sheet S can be executed.

The feeding unit 10 includes a paper feed tray 11 that accommodates the recording sheets S, a feeding roller 12P provided in the paper feeding tray 11 that feeds out the recording sheets S one by one toward the conveying path 19, and the fed recording sheets. A sheet feeding roller 12F for feeding and conveying the recording sheet S, and a timing roller 13 for determining the timing of sending out the recording sheet S to the secondary transfer position 29 are provided.

The image forming section 20 forms a toner image on the recording sheet S sent from the feeding section 10 . Specifically, in the four image forming units 21Y, 21M, 21C, and 21K, the surfaces of the charged photoreceptor drums 25Y, 25M, 25C, and 25K are irradiated with laser beams from the exposure section 26 that are modulated and driven based on image data. It is exposed to light to create an electrostatic latent image on its surface, and the electrostatic latent image is developed with yellow (Y), magenta (M), cyan (C) and black (K) toners.

Four-color toner images visualized by development are formed on photosensitive drums 25Y, 25M, 25C, and 25K and primary transfer rollers 22Y, 22M, 22C, and 22K opposed to them via intermediate transfer belt 23. The surface of each photosensitive drum is primarily transferred onto the surface of the intermediate transfer belt 23 by the electric field between them. In this primary transfer, the toner image forming timings of the image forming units 21Y to 21K are shifted so that the Y to K color toner images are transferred to the same position on the intermediate transfer belt 23. FIG. As a result, a color toner image is formed on the intermediate transfer belt 23 by multiple transfer of Y to K color toner images.

The intermediate transfer belt 23 is positioned above the photoreceptor drums 25Y to 25K, stretched over a plurality of rollers including a drive roller 23R and a driven roller 23L, and circulates in the arrow A direction. The color toner image on the intermediate transfer belt 23 moves to a secondary transfer position 29 where the intermediate transfer belt 23 and the secondary transfer roller 24 contact each other as the intermediate transfer belt 23 rotates. The secondary transfer roller 24 is urged toward the intermediate transfer belt 23 by an urging means (not shown), and a predetermined nip pressure is generated between them.

The color toner image on the intermediate transfer belt 23 is transferred from the recording sheet S conveyed from the feeding unit 10 to the intermediate transfer position 29 by the electric field between the intermediate transfer belt 23 and the secondary transfer roller 24 . When passing between the transfer belt 23 and the secondary transfer roller 24, the recording sheet S is secondarily transferred to the surface (first surface) thereof. Toner remaining on the intermediate transfer belt 23 after the secondary transfer is removed by the cleaning blade 23B.

The recording sheet S on which the color toner image (unfixed image) has been secondarily transferred is conveyed in the direction of arrow E by the secondary transfer roller 24 toward the fixing section 30 .

The fixing unit 30 includes a fixing belt (endless belt) 31 and a pressure roller (rotating body) 32, and a color toner image is formed by passing the recording sheet S through a nip portion Np formed between them. is thermally fixed on the recording sheet S.

The discharge unit 40 includes a discharge roller 41 and a paper discharge port 45 , and discharges the recording sheet S on which the color toner image is fixed from the paper discharge port 45 . The ejection roller 41 is arranged inside the paper ejection port 45, and rotates (normally rotates) in the direction of the arrow B to transport the recording sheet S conveyed from the fixing section 30 through the paper ejection port 45 and out of the apparatus. discharge to The ejected paper S is accommodated in the paper ejection tray 46 . Thus, single-sided printing for printing only on the first side of the recording sheet S is completed.

In the case of a double-sided print job, the recording sheet S that has passed the secondary transfer position 29 during printing on the front side (first side) is conveyed from the fixing section 30 to the discharge roller 41 . When the trailing edge of the recording sheet S conveyed by the discharge roller 41 passes the detection position of the discharge sensor ES, which is an optical sensor, the discharge roller 41 switches from forward rotation to reverse rotation (rotation in the direction of arrow C).

Due to the reverse rotation of the discharge roller 41, the recording sheet S is reversed and guided to the double-sided conveying portion 50, and conveyed along the double-sided conveying path in the direction of arrow D by the double-sided conveying rollers 51, 52, 53, 54, and 55. , and the color toner image is secondarily transferred to the back surface (second surface) of the recording sheet S and thermally fixed by the fixing unit 30 . The paper is discharged to the paper discharge tray 46 via.

In the feeding unit 10 and the image forming unit 20, the rotating members including the feeding and transporting rollers, the driving roller 23R, the photosensitive drums 25Y to 25K, etc. are driven by the driving force of the driving motor M1 arranged in the image forming unit 20. Rotate by The pressure roller 32 in the fixing unit 30 is driven to rotate by a drive motor (fixing motor) M2, and the discharge roller 41 rotates forward and backward by the driving force of a drive motor M3 arranged in the discharge unit 40, and double-sided conveying roller. 51 to 55 are rotated by the driving force of the driving motor M4 arranged in the double-sided conveying section 50. As shown in FIG.

The control unit 100 is connected to an external terminal device via a network, receives print job data sent from this terminal device, and generates image data to be printed from the received print job data. and print the generated image data.

(2) Configuration of Fixing Section FIG. 2 is a sectional view showing the configuration of the fixing section 30. As shown in FIG.

As shown in the figure, the fixing section 30 stretches a fixing belt 31 between a heating roller 34 (heating section) and a fixing pad (support) 33, and presses a pressure roller 32 toward the fixing pad 33. A nip portion is formed.

In FIG. 2, the axial direction (longitudinal direction) of the heating roller 34 is the X-axis, the vertical direction is the Z-axis, and the direction orthogonal to the XZ-axis is the Y-axis (the same applies to the following drawings).

In this embodiment, the fixing pad 33 is made of resin and elongated in a direction (X-axis direction) parallel to the axis of the heating roller 34, and contacts the rear surface of the fixing belt 31 to support it. To support. The fixing pad 33 is fixed to the housing 38 via the support member 331 .

The surface of the fixing pad 33 that contacts the fixing belt 31 is desirably coated with a surface treatment and/or a lubricant to reduce friction.

The fixing belt 31 includes, for example, a base layer made of polyimide, SUS (stainless steel), or the like, an elastic layer made of a highly heat-resistant material such as silicone rubber or fluororubber, and a layer of PFA (perfluoroalkoxy fluororesin) or the like. Release layers made of fluorine-based resin and provided with release properties are laminated in this order.

The pressure roller 32 has an elastic layer 322 formed of a highly heat-resistant elastic material such as silicone rubber laminated on the outer peripheral surface of a cylindrical core metal 321 made of aluminum, iron, or the like. A release layer (not shown) such as PFA may be further laminated on the outermost layer.

The pressing roller 32 is pressed against the outer peripheral surface of the fixing belt 31 with a predetermined load (pressing force) due to the biasing force of an elastic member (not shown) such as a spring. This pressure contact forms a nip portion Np between the outer peripheral surface of the pressure roller 32 and the outer peripheral surface of the fixing belt 31 .

The pressure roller 32 is rotationally driven at a predetermined rotational speed in the direction of arrow Q by the rotational driving force of the fixing motor M2 (FIG. 1), and functions as a driving roller. As the pressure roller 32 rotates, the heating roller 34 and the fixing belt 31 stretched between the heating roller 34 and the fixing pad 33 are driven to rotate (run) in the arrow P direction.

The heating roller 34 is formed, for example, by laminating a coat layer made of PTFE (polytetrafluoroethylene) on the outer peripheral surface of a cylindrical aluminum hollow core, and both ends in the axial direction are attached to the frame of the housing 38 of the fixing section 30 . It is rotatably supported.

A heater portion 341 is inserted in the inner peripheral side of the cylindrical heating roller 34, and a first heater 3411 that heats substantially the entire range in the axial direction (longitudinal direction: X-axis direction in FIG. 2) of the heating roller 34. , and a second heater 3412 that heats the central portion in the axial direction.

The heating roller 34 is held in an elongated hole (not shown) of the frame of the housing 38 via a bearing member 342 . The major diameter of the elongated hole is inclined to the right in the drawing, and the heating roller 34 is pushed away from the fixing pad 33 by biasing the bearing member 342 obliquely downward to the left with an elastic member 343 such as a compression spring. As a result, a predetermined amount of tension is applied to the fixing belt 31 .

When the heater portion 341 is energized while the fixing belt 31 is running around, the heat generated from the heater portion 341 is transmitted from the heating roller 34 to the fixing belt 31 and reaches the nip portion Np as the fixing belt 31 runs around.

As a result, the heat of the fixing belt 31 is supplied to the pressure roller 32 and the fixing pad 33, and the temperature of the nip portion Np, which is the contact area between the fixing belt 31 and the pressure roller 32, rises.

A temperature sensor (not shown) is disposed near the portion of the fixing belt 31 that contacts the outer peripheral surface of the heating roller 34 to detect the surface temperature of the fixing belt 31. Based on the detection result, the controller 100 controls the heater. The electric power supplied to the portion 341 is turned on and off, and the fixing belt 31 is controlled to reach the target temperature.

The recording sheet to which the toner image has been transferred passes through the nip portion Np with the surface to which the toner image is transferred facing the heated fixing belt 31 . The recording sheet passing through the nip portion Np is pressed and heated by being sandwiched between the fixing belt 31 and the pressure roller 32, and the toner image is fixed on the recording sheet.

A pair of sheet passing guide members 391 and 392 on the entrance side are arranged upstream of the nip portion Np in the sheet conveying direction, and guide the recording sheet S that has passed the secondary transfer position 29 toward the nip portion Np. .

Further, a pair of exit-side sheet passing guide members 36 and 37 are arranged downstream of the nip portion Np in the sheet conveying direction, and guide the recording sheet S that has passed through the nip portion Np to the exit 381 of the housing 38 of the fixing portion 30 . guide towards.

The recording sheet S that has passed through the nip portion Np adheres to the surface of the fixing belt 31 due to the fused toner, and tends to be discharged while being close to the fixing belt 31 side. Since the curvature of the surface of the fixing belt 31 supported by the fixing pad 33 on the downstream side of the nip portion Np is large, the leading edge of the recording sheet S is lifted from the surface of the fixing belt 31 due to the stiffness of the recording sheet S itself. is scooped up by a leading end portion 3631 (see FIG. 4) on the nip portion Np side of the sheet passing guide 36 on the fixing belt 31 side (hereinafter referred to as the "belt side sheet passing guide 36") and guided upward (in this way). In addition, scooping up the leading edge of the recording sheet from the fixing belt by the belt-side paper-passing guide is hereinafter referred to as a "scooping-up function").

In order to effectively exhibit the scooping function, the distance between the front end portion 3631 of the belt-side paper-passing guide 36 and the surface of the fixing belt 31 in the stopped state (the state in which the belt is not lifted) should be as small as possible. is desirable. Otherwise, since the thin sheet is particularly weak, the leading edge of the sheet is not lifted by a small amount, and the sheet is caught in the fixing belt 31 as it is, causing trouble. In the present embodiment, the thickness is about 1 to 2 mm, but is not limited to this. material, etc.), it is arranged close to the range where the scooping function can be exhibited.

However, if the fixing belt 31 is in an unstable state such as when the apparatus is started, the fixing belt 31 may float as described above, and the lower end portion of the rib of the belt-side paper-passing guide may occur. come into contact with

As described above, in the conventional art, the width of the rib is small, and the lower corner of the rib is relatively sharp and faces the fixing belt 31. As a result, the surface of the fixing belt 31 is scratched, and the image quality such as glossy streaks is deteriorated. Therefore, in the present embodiment, a belt protection member is provided along the lower edge of the belt-side paper-passing guide 36 to increase the contact area with the fixing belt 31. It is configured so that the surface of the fixing belt 31 is not damaged.

In the case of executing a double-sided print job, when the recording sheet S having a toner image formed on its first side (front side) passes through the nip portion Np for fixing the toner image on its second side (back side), Since the toner image formed on the first surface may cause the recording sheet S to adhere to the pressure roller 32 side, in the present embodiment, the separation claw 371 is arranged on the paper passing guide 37 side. .

(3) Belt Protection Member Hereinafter, three examples of the belt protection member in the belt-side paper-passing guide according to the present embodiment will be described.

(3-1) First Embodiment of Belt Protection Member FIG. 3(a) is a perspective view of the belt-side paper-passing guide 36 according to the present embodiment when viewed obliquely from the front right in FIG. 3(b) is an enlarged view of the portion surrounded by the dashed line J1 in FIG. 3(a).

As shown in FIG. 3A, the belt-side paper-passing guide 36 is provided on the sheet guide surface side (surface on which the recording sheet S is guided) of a plate-shaped guide body 361 elongated in the X direction. A plurality of ribs 362 extending along the S transport direction E (see FIG. 1) are arranged in parallel in the longitudinal direction (X direction).

The positions of the ribs 362 in the X direction are provided in a plurality of positions necessary to guide at least the center peripheral portion and both end portions in the width direction for each of the plurality of sizes of the recording sheets S that can be used in the printer 1. there is

In this embodiment, the belt protection member 363 is positioned along the lower edge 3611 of the belt-side sheet passing guide 36 at a position closer to the nip Np than the lower end of the rib 362 (tip on the nip Np side). 362, and has a T shape when viewed upside down from the Y-axis direction.

In this embodiment, the height of the belt protection member 363 (height from the guide side surface of the guide body 361) is equal to the height of the lower end of the rib 362 (tip on the nip side). The upper limit of the height in this case is determined by the design specifications such as the installation space of the belt-side paper-passing guide 36 in the housing 38, and the leading edge of the recording sheet S of the belt-side paper-passing guide 36. A person skilled in the art can determine this by design or experiment, considering the need to perform the function of scooping up.

Also, the width of the belt protection member 363 (the width in the X-axis direction) is larger than the width of the lower end of the rib 362, preferably 5 mm or more.

If the width is at least wider than the width of the rib 362, the contact area with the fixing belt 31 when the belt is lifted can be increased, and the occurrence of scratches on the fixing belt 31 can be suppressed compared to the conventional art.

A surface 3632 of each belt protection member 363 facing the fixing belt 31 is preferably flat and coplanar including the lower edge 3611 .

FIG. 4 is a diagram for explaining the effect of providing the belt protection member 363 to the belt-side paper-passage guide 36 in the fixing section 30. As shown in FIG. For the sake of simplification, illustration of the sheet passing guide 37 and the like is omitted.

As shown in FIG. 4, when the printer 1 is started up, even if the belt float 31a occurs on the fixing belt 31, the flat opposing surface of the belt protection member 363 having a larger area than the edge area of the conventional rib 362 is formed. 3632, the surface of the fixing belt 31 is prevented from being scratched, and deterioration of the fixed image can be prevented.

The positions of the plurality of ribs 362 and the length of each belt protection member 363 in the X-axis direction are symmetrical with respect to the sheet passing center (the center in the X-axis direction) M (FIG. 3A) in the sheet conveying path. is desirable. This is because the contact resistance with respect to the recording sheet S is made symmetrical with respect to the sheet passing center M in the sheet width direction, and the recording sheet S is smoothly conveyed without skewing.

(3-2) Second Embodiment of Belt Protection Member In the first embodiment, the belt protection member 363 is integrally provided at the tip of the rib 362 to form a T-shape. In the example, a plurality of belt protection members are arranged in series in the X direction.

FIG. 5(a) is a perspective view of the belt-side sheet passing guide 36 according to the second embodiment when viewed from the same direction as FIG. 3(a), and FIG. 5(b) is a perspective view of FIG. 5(a). 2 is an enlarged view of a portion surrounded by a dashed line J2 in FIG.

As shown in FIG. 5A, a belt protection member 364 in this embodiment has a shape in which a plurality of belt protection members 363 in the first embodiment are connected in the X direction.

Also in this embodiment, the height of the belt protection member 364 should be at least the height of the lower ends of the ribs 362 .

According to the second embodiment, the area of the facing surface 3642 of the belt protection member 364 facing the fixing belt 31 is increased, and the contact between the fixing belt 31 and the belt floating portion 31a is greater than in the case of the first embodiment. Since the area can be greatly increased, the effect of preventing scratches on the fixing belt 31 is further enhanced.

On the other hand, if the belt protection member 364 is formed in the shape of a single rib along the lower edge of the belt-side paper-passing guide 36, the thickness of the edge increases substantially throughout the X direction. When manufacturing using injection molding, there is a possibility that "warping" occurs in the X-axis direction due to variations in the cooling rate in the longitudinal direction.

A function of scooping up the leading edge of the recording sheet S and guiding it backward when the gap in the X direction between the lower edge of the belt-side paper-passing guide 36 and the fixing belt 31 varies due to the influence of "warp" in the X direction. Since there is a risk that the belt protection member 364 It is desirable to determine each dimension (height and width in the sheet conveying direction).

It should be noted that the belt protection member 364 does not necessarily have to be continuous across all the ribs 362, and may be divided at appropriate locations excluding locations where the ends of the ribs 362 exist.

(3-3) Third Embodiment of Belt Protection Member FIG. 6(a) is a perspective view of the belt-side sheet passing guide 36 according to the second embodiment when viewed from the same direction as FIG. 3(a). 6(b) is an enlarged view of the portion surrounded by the dashed line J3 in FIG. 6(a).

In this third embodiment, in addition to forming the belt protection member 363 in a T shape with respect to the rib 362 as shown in FIGS. 2, a belt protection member 365 that has a U-shape when viewed in the Y-axis direction may be formed by connecting the tips of two adjacent ribs 362 .

When the T-shaped belt protection member 363 (FIG. 3B) and the U-shaped belt protection member 365 are combined, the arrangement of both is symmetrical with respect to the sheet passing center M. It is desirable to distribute to This is because the magnitude of the contact friction of the belt protection member with respect to the recording sheet S is also bilaterally symmetrical, so it is considered that the recording sheet S can be smoothly guided along the conveying direction rather than being randomly arranged.

(4) Manufacturing Method of Belt-Side Paper Passing Guide In the present embodiment, the belt-side paper passing guide 36 is manufactured by injection molding from the viewpoint of manufacturing cost.

In injection molding, a resin material such as a synthetic resin (plastic) is melted by heating and injected into a mold, then cooled and molded. Injection molding is advantageous in terms of manufacturing costs because parts with complicated shapes can be continuously manufactured in large quantities.

7(a) and 7(b) show a mold split for forming the belt-side paper-passing guide 36 according to the present embodiment by injection molding, and a conventional belt-side paper-passing guide 536 (FIG. 11). It is a figure for each demonstrating the mold division in the case of forming by injection molding.

7(a) and 7(b) show that the mold and the paper-passing guide, which are the molded parts, before mold release (before the mold is removed and the molded part is taken out) are aligned in the X-axis direction (Fig. 2). , FIG. 11), but for the sake of simplification, the cross section of the mold is not hatched.

FIG. 7(b) is a cross-sectional view for explaining a mold used for injection molding of a conventional belt-side paper-passing guide.

As shown in the figure, the conventional mold consists of three split molds 421-423. It is designed to open in the direction of K13.

From the standpoint of releasability, a mold splitting line 425 (joint portion of the split molds 421 and 423) is arranged at an angle 5362a at the tip of the rib 5362 of the sheet passing guide 536. Therefore, minute steps and burrs are generated at this portion. may occur.

The present inventors consider that when the fixing belt floats and comes into contact with the tip 5362a of the rib 5362, the minute steps and burrs make the surface of the fixing belt 31 more susceptible to damage. clarified by

In this embodiment, the belt protection member is provided in order to prevent the fixing belt 31 from being damaged as described above. If the burr remains, the fixing belt may still be damaged, although the burr is smaller than the conventional one.

Although it is possible to remove steps and burrs by polishing, it requires a lot of man-hours and is not desirable in terms of cost. Therefore, in the present embodiment, the configuration of the mold is devised.

FIG. 7A is a cross-sectional view for explaining a mold used for injection molding of the belt-side paper-passing guide according to this embodiment.

As shown in the figure, the mold in the present embodiment consists of three split molds 411 to 413, and when releasing the mold, each split mold is separated from each other by the mold split lines 414 to 416. It is designed to open in the directions of arrows K1 to K3.

A characteristic point is that the mold splitting line 415 between the split molds 411 and 413 is changed to the left end position of the facing surface 3632 of the belt protection member 363 of the belt-side sheet passing guide 36 .

As a result, even if a minute step or burr remains at the position of the mold splitting line 415 after mold release, the facing surface 3632 of the belt protection member 363 is located on the most upstream side in the running direction of the fixing belt 31 (that is, at the nip portion) as shown in FIG. The distance G2 between the fixing belt 31 and the most downstream side of the fixing belt 31 running direction of the facing surface 3632 (that is, the side closest to the nip portion Np) and the fixing belt 31 is larger than the distance G1 between the fixing belt 31 and the fixing belt 31. If the inclination of the belt protection member 363 is set as described above, even if the belt floats, the fixing belt 31 is less likely to come into contact with the steps and burrs of the belt protection member 363 on the most downstream side in the running direction of the fixing belt 31 . , the fixing belt 31 can be more effectively prevented from being damaged.

As described above, according to the present embodiment, even if the behavior of the belt becomes unstable due to fluctuations in rotational torque or the like and the belt floats, the nip portion Np side of the rib rather than the nip portion Np side tip portion of the rib By providing the belt protection member at the position of , it is possible to suppress the occurrence of scratches on the fixing belt while suppressing the burden of manufacturing costs with a simple structure, and the fixing device is equipped with a fixing device that always satisfies good fixing quality over a long period of time. It is possible to provide an image forming apparatus with

In the case of manufacturing the belt-side paper-passing guide by injection molding, in addition to the above-mentioned belt protection member, by devising the mold division when molding the belt-side paper-passing guide, the manufacturing cost can be suppressed and the efficiency can be further improved. It is possible to prevent the occurrence of scratches on the fixing belt.

<Modification>
Although the above has been described based on the embodiments according to the present disclosure, the present disclosure is of course not limited to the above-described embodiments, and the following modifications are conceivable.

(1) In the fixing unit 30 according to the above embodiment, the fixing belt 31 is sandwiched between the fixing pad 33 and the pressure roller 32 to form a nip portion (hereinafter, the nip portion is formed by sandwiching the fixing belt 31 in this way). The forming member is referred to as a "nip forming member").

However, in such a nip portion forming member, instead of the fixing pad 33, a fixing roller may be used as a support. This is because, even in this case, the surface of the fixing belt 31 may be damaged due to the same belt floating phenomenon as in the case where the fixing pad 33 is used.

For the fixing roller in this case, it is desirable to use a resin material having as high adiabaticity and a small heat capacity as possible and to have a hollow shape in order to save energy.

(2) In the above-described embodiment, as shown in FIGS. By providing a wide belt protection member and increasing the contact area of the fixing belt 31 with the belt floating portion, the fixing belt 31 is protected from being damaged. Also by increasing the area of the lower end surface of the rib 362 itself, it is possible to increase the contact area of the fixing belt 31 with the belt floating portion, thereby suppressing the occurrence of scratches on the fixing belt 31 .

FIG. 9(a) is a perspective view of the belt-side sheet passing guide 36 in such a case, and FIG. 9(b) is an enlarged view of the portion surrounded by the broken line J4 in FIG. 9(a).

In this modified example, two types of wide ribs 366 and 367, W1 and W2 (W1>W2), which are larger in width in the X direction than in the conventional one, are formed. The arrangement of the ribs 366 and 367 in the X direction is symmetrical with respect to the sheet passing center M so that the recording sheet S can be smoothly conveyed.

In order not to damage the fixing belt 31, it is desirable that W2≧6 mm. Further, if the width of the rib 366 is too large, the contact friction with the recording sheet S increases, and the toner immediately after fixing tends to adhere to the upper surface of the rib.

In addition, although the height of each rib is set to 2 mm, for example, in this modified example, it is not limited to this, and may be appropriately determined in order to obtain the necessary contact area.

Also, the width of the rib 366 does not necessarily have to be greater than the width of the rib 367 (W1>W2), and even if both have the same width (W1=W2), the upper and lower limits are within the above range (6 mm 11 mm or less).

Furthermore, each rib does not necessarily have to have the same width over the entire length in the conveying direction of the recording sheet S. For example, the ribs may have a shape that gradually tapers from the leading end portion on the nip side toward the downstream side in the sheet conveying direction. . In this case, at least the width at the nip-side tip portion should be within the above range.

(3) In the above embodiment, eg, FIG. 3, the belt protection member 363 is integrally formed with the tip of the rib 362, but this is not necessarily required. The belt protection member 363 is a separate member from the rib 362, and is closer to the nip portion Np side than the tip portion of the rib 362 on the nip portion Np side, and is positioned close to the tip portion (for example, a position separated by about 1 mm to 2 mm). ), if the leading edge of the recording sheet S scooped up by the belt protection member 363 does not come into contact with the edge surface of the leading edge of the rib 362, the recording sheet S is not hindered in guiding.

(4) In the fixing unit 30 in the above embodiment, the heating roller 34 containing a halogen heater is used as a heat source. The fixing device may have a configuration in which the fixing belt 31 is directly energized to generate resistance heat.

(5) In the above embodiment, as one aspect of disclosure of the sheet conveying device, the embodiment of the fixing section has been described, but it is also applicable to the secondary transfer section in the image forming section 20 (FIG. 1).

FIG. 10 is a diagram showing a configuration example of a secondary transfer section (transfer device) according to this modified example, and the same reference numerals as in FIG. 1 denote the same members as in FIG. 1, so description thereof will be omitted.

As shown in the figure, a secondary transfer roller 24 is arranged at a position facing a driving roller 23R with an endless belt-shaped intermediate transfer belt (image carrying belt) 23 interposed therebetween. A transfer nip TN is formed with the transfer roller 24 .

After passing through the transfer nip TN, the recording sheet S is guided by a pair of sheet guides 290 and 294 and conveyed further upward.

Due to the influence of the toner, the recording sheet S adheres to the intermediate transfer belt 23 even after passing through the transfer nip TN and is conveyed. It is designed to guide you.

When the intermediate transfer belt 23 starts to rotate, such as when the apparatus is started, the friction between the cleaning blade 23B and the intermediate transfer belt 23 (static friction is greater than dynamic friction), and at this point, the surface of the intermediate transfer belt 23 is Friction is large because there is not much remaining toner as a lubricant), the rotational torque becomes unstable, and the intermediate transfer belt 23 tends to float.

Therefore, like the belt-side paper-passing guide 36 in the fixing section 30, the edge of the rib 292 provided on the sheet guide surface side of the guide main body 291 of the sheet guide 290 on the side of the nip portion Np also has the belt in the above-described embodiment. A belt protection member 293 having the same shape as the protection member 363 and the like is provided so that the surface of the intermediate transfer belt 23 is not damaged even if it comes into contact with the intermediate transfer belt 23 .

As a result, deterioration of the intermediate transfer belt 23 can be suppressed, and the image quality of the transferred toner image can be prevented from deteriorating.

In an image forming apparatus that uses a photoreceptor belt instead of an intermediate transfer belt to directly form a toner image on the photoreceptor belt and transfer the toner image onto the recording sheet S, the photoreceptor belt carries the image. becomes a belt.

(6) The sheet conveying device according to the present disclosure includes not only the fixing device and the transfer device as described above, but also an endless belt and a rotating body that form a nip portion, and not only a recording sheet but also any kind of sheet can be placed in the nip portion. General sheet conveying devices that pass and convey sheets and are provided with a guide member that guides a sheet discharged along an endless belt from a nip portion, and image forming apparatuses equipped with such sheet conveying devices. It is possible to apply

<Supplement>
As described above, the fixing device, the transfer device, and the image forming apparatus provided with the sheet conveying device as one form of the sheet conveying device according to the present disclosure have been described based on the embodiments and modifications. It is not limited to the embodiments and modifications of . Forms obtained by applying various modifications that a person skilled in the art can think of to the above embodiments and modifications, and arbitrarily combining the constituent elements and functions in the embodiments and modifications without departing from the spirit of the present invention Any implementations are also included in the invention.

The present disclosure relates to an image having a belt-type fixing device that thermally fixes an unfixed toner image formed on a sheet using a fixing belt, a transfer device that transfers the toner image on the intermediate transfer belt onto the sheet, and the like. It can be widely applied to forming equipment.

1 Printer 20 Imaging Section 23 Intermediate Transfer Belt 23L Driven Roller 23R Driving Roller 23B Cleaning Blade 24 Secondary Transfer Roller 30 Fixing Section 31 Fixing Belt 31a Belt Float 32 Pressurizing Roller 33 Fixing Pad 34 Heating Roller 36 Belt Side Paper Passing Guide 361 Guide bodies 362, 367, 368 Ribs 363-365 Belt protection member

Claims (10)

A sheet conveying device in which an endless belt is pressed and held between a long support member and a rotating member to form a nip portion, and a sheet is passed through the nip portion and conveyed,
a guide member that guides the sheet discharged from the nip toward the endless belt;
The guide member is formed by arranging a plurality of ribs extending along the sheet conveying direction on the sheet guide surface side of the guide body in a direction orthogonal to the sheet conveying direction,
At a position closer to the nip portion than the nip side tip portions of the plurality of ribs, a belt protection member having at least the same height as the tip portions of the ribs and having a width wider than the tip portions is provided on the guide main body. provided along the nip side edge of the sheet conveying device. 2. The sheet conveying apparatus according to claim 1, wherein the belt protection member is formed to be continuous along the edge of the guide body on the nip side. 2. The sheet conveying apparatus according to claim 1, wherein the belt protection member is divided along the edge of the guide body on the nip side and provided in plurality. The tip of the rib and the belt protection member are integrally formed, and the tip of the rib on the nip side is connected to the belt protection member to form a T-shape and/or the nip side of two adjacent ribs. 4. The sheet conveying device according to claim 3, wherein the leading ends are connected to each other via a belt protection member to form a U-shape. In a state where the endless belt does not float, the distance between the surface of the belt protection member facing the endless belt and the surface of the endless belt is greater than the first position closest to the nip portion of the facing surface. 5. The sheet conveying method according to any one of claims 1 to 4, wherein the belt protection member is arranged so that a second position farthest from the nip portion is larger. Device. 6. The sheet conveying apparatus according to claim 5, wherein the guide member is formed by injection molding, and the mold for injection molding has a mold split at a position corresponding to the second position. A sheet conveying device in which an endless belt is pressed and held between a long support member and a rotating member to form a nip portion, and a sheet is passed through the nip portion and conveyed,
a guide member that guides the sheet discharged from the nip toward the endless belt;
The guide member is formed by arranging a plurality of ribs extending along the sheet conveying direction on the sheet guide surface side of the guide body in a direction orthogonal to the sheet conveying direction,
The sheet conveying device, wherein the width of the tip portions of the plurality of ribs on the nip side in a direction perpendicular to the conveying direction of the sheet is 6 mm or more and 11 mm or less. 8. The sheet conveying apparatus according to any one of items 1 to 7, wherein the endless belt is a fixing belt, and is provided with heating means for heating the fixing belt. The endless belt is an image carrying belt carrying a toner image, and the rotating body passes the toner image carried on the surface of the image carrying belt through a nip portion between the image carrying belt and the rotating body. 8. The sheet conveying device according to any one of items 1 to 7, wherein the sheet conveying device is a transfer roller for transferring onto a sheet. An image forming apparatus comprising the sheet conveying device according to any one of claims 1 to 9.

Images