Image forming apparatus

Abstract

To provide a configuration that supports a pre-fixing conveying unit 410 and a fixing unit 50 in a first housing 102a and a second housing 103a, respectively, and connects the first housing 102a and the second housing 103a with each other, and can prevent the occurrence of a failure in sheet conveyance.SOLUTION: The second housing 103a is connected to the first hosing 102a such that a part of the pre-fixing conveying unit 410 is inserted into the second housing, and thereby a sheet is conveyed from the pre-fixing conveying unit 410 to the fixing unit 50. The pre-fixing conveying unit 410 is oscillatably supported by an oscillating support part 415 with respect to the first housing 102a centered on an oscillation axis α along a sheet width direction intersecting a sheet conveyance direction FD. A positioning member 131a provided in the second housing 103a and a contact part 416 provided on a part of the pre-fixing conveying unit 410 are brought into contact with each other to determine the position of the pre-fixing conveying unit 410 in the oscillation direction centered on the oscillation axis α.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multifunction machine having a plurality of these functions.

Background Art

[0002] In an image forming apparatus, a configuration is conventionally known in which a toner image is transferred to a sheet at a transfer unit, and the toner image transferred to the sheet at the transfer unit is fixed to the sheet at a fixing unit. Further, a configuration including a transport unit that transports a sheet between the transfer unit and the fixing unit in the sheet transport direction is also conventionally known (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Here, with the increase in the speed of the image forming apparatus, the apparatus is becoming larger, and there is a configuration in which the transport unit and the fixing unit are supported by separate casings, and these casings are connected and used. In such a configuration where two casings are connected, many components are interposed between the transport unit and the fixing unit supported by separate casings, so that the tolerance regarding the position of the transport unit and the position of the fixing unit increases. Therefore, the relationship between the position of the transport unit and the position of the fixing unit deviates from an appropriate position, and there is a risk that sheet transport failure may occur when transporting the sheet from the transport unit to the fixing unit.

[0005] An object of the present invention is to provide a configuration capable of suppressing the occurrence of sheet transport failure in a configuration in which a transport unit and a fixing unit are supported by separate casings and these casings are connected.

Means for Solving the Problems

[0006] One aspect of the present invention comprises a transfer unit for transferring a toner image to a sheet, a fixing unit for fixing the toner image transferred to the sheet by the transfer unit to the sheet, a belt suction transport unit disposed between the transfer unit and the fixing unit in the sheet transport direction and having a belt unit and a suction unit for sucking the sheet to the belt unit by sucking air, wherein the belt suction transport unit transports the sheet sucked to the belt unit toward the fixing unit by rotating the belt unit, a first housing, and a second housing connected to the first housing and supporting the fixing unit. The belt suction conveying unit is supported by the first housing in a state that it can pivot about a pivot axis extending in the sheet width direction intersecting the sheet conveying direction, the second housing is provided with a rotating member for positioning the belt suction conveying unit in the vertical direction, the belt suction conveying unit has a positioning surface that contacts the rotating member to position the belt suction conveying unit in the vertical direction, and a guide surface provided downstream of the positioning surface in the sheet conveying direction, which guides the rotating member toward the positioning surface when the first housing and the second housing are connected. This is an image forming apparatus characterized by the following features. Another aspect of the present invention is a belt suction conveying unit having a transfer unit for transferring a toner image to a sheet, a fixing unit for fixing the toner image transferred to the sheet by the transfer unit to the sheet, a belt suction conveying unit disposed between the transfer unit and the fixing unit in the sheet conveying direction and comprising a belt unit and a suction unit for sucking the sheet to the belt unit by sucking air, wherein the belt suction conveying unit conveys the sheet sucked to the belt unit toward the fixing unit by rotating the belt unit, a first housing, a second housing connected to the first housing and supporting the fixing unit, and the belt suction conveying unit toward the first conveying unit In this case, the image forming apparatus comprises a second transport unit which is positioned between the first transport unit and the transfer unit in the sheet transport direction and transports the sheet on which the toner image has been transferred by the transfer unit toward the first transport unit, wherein the first housing has a first positioning unit which positions the belt suction transport unit in a predetermined direction along a plane perpendicular to the width direction of the sheet which is perpendicular to the sheet transport direction, the second housing has a second positioning unit which positions the belt suction transport unit in the predetermined direction, and the second transport unit is supported so as to be insertable and removable from the first housing. Another aspect of the present invention is a belt suction transport unit having a transfer unit for transferring a toner image to a sheet, a fixing unit for fixing the toner image transferred to the sheet by the transfer unit to the sheet, and a belt suction transport unit having a belt unit and a suction unit for sucking the sheet to the belt unit by sucking air, wherein the belt suction transport unit rotates the belt unit to transport the sheet sucked to the belt unit toward the fixing unit, a first housing, a second housing connected to the first housing and supporting the fixing unit, and when the belt suction transport unit is the first transport unit, a belt suction transport unit having a belt suction transport unit having a belt unit and a fixing unit for fixing the sheet transferred to the sheet by the transfer unit The image forming apparatus comprises: a second transport unit that transports a sheet toward the first transport unit; a third housing that supports the transfer unit; and a third transport unit that is positioned between the first transport unit and the second transport unit in the sheet transport direction and transports the sheet from the second transport unit toward the first transport unit, wherein the first housing has a first positioning unit that positions the belt suction transport unit in a predetermined direction along a plane perpendicular to the width direction of the sheet which is perpendicular to the sheet transport direction; the second housing has a second positioning unit that positions the belt suction transport unit in the predetermined direction; and the first housing is positioned between the third housing and the second housing in the sheet transport direction and is connected to the third housing and the second housing, respectively. Another aspect of the present invention is a belt suction transport unit comprising: a transfer unit for transferring a toner image to a sheet; a fixing unit for fixing the toner image transferred to the sheet by the transfer unit to the sheet; a belt suction transport unit disposed between the transfer unit and the fixing unit in the sheet transport direction, having a belt unit and a suction unit for sucking the sheet to the belt unit by sucking air, wherein the belt suction transport unit transports the sheet sucked to the belt unit toward the fixing unit by rotating the belt unit; a first housing; and a second housing connected to the first housing and supporting the fixing unit, wherein the first housing has a first positioning unit for positioning the belt suction transport unit in a predetermined direction along a plane perpendicular to the width direction of the sheet and perpendicular to the sheet transport direction, and the second housing is The image forming apparatus is characterized by having a second positioning unit for positioning the belt suction conveying unit in the predetermined direction, the belt suction conveying unit swingably supporting the belt suction conveying unit and having one of the following: a swing shaft extending in the sheet width direction intersecting the sheet conveying direction, a hole that engages with the swing shaft, a contact portion, and a swing restricting unit that can restrict the swing range around the swing shaft when the first housing is not connected to the second housing, the first positioning unit being the other of the swing shaft and the hole, the second positioning unit being the contacted portion that the contact portion contacts, and the swing range by the swing restricting unit being configured such that the contacted portion can contact the contact portion when the first housing is connected to the second housing. [Effects of the Invention]

[0007] According to the present invention, in a configuration in which the conveying unit and the fixing unit are supported in separate housings and these housings are connected, the occurrence of sheet conveying defects can be suppressed. [Brief explanation of the drawing]

[0008] [Figure 1] A schematic cross-sectional view of the image forming apparatus according to the first embodiment. [Figure 2] A schematic cross-sectional view of the main body of the image forming apparatus according to the first embodiment. [Figure 3] (a) A schematic cross-sectional view of a color image forming station according to the first embodiment, and (b) a schematic cross-sectional view of a black image forming station according to the first embodiment. [Figure 4] A schematic cross-sectional view of the fixing and transporting unit according to the first embodiment. [Figure 5] A schematic cross-sectional view showing the configuration from the secondary transfer section to the fixing section of the fixing transport section of the main body of the image forming apparatus according to the first embodiment. [Figure 6] A schematic plan view of the pre-fixing transport unit according to the first embodiment, viewed from below. [Figure 7]Schematic cross-sectional view of the positioning unit according to the first embodiment, as viewed from the conveyance direction. [Figure 8] Schematic cross-sectional view showing the configuration for positioning the pre-fixing conveyance unit according to the first embodiment. [Figure 9] Schematic cross-sectional view of the image forming apparatus according to the second embodiment. [Figure 10] Schematic cross-sectional view showing from the secondary transfer unit to the fixing unit of the fixing conveyance unit in the main body of the image forming apparatus according to the second embodiment. [Figure 11] Schematic cross-sectional view of the image forming apparatus according to the third embodiment. [Figure 12] Schematic cross-sectional view showing from the secondary transfer unit to the fixing unit of the fixing conveyance unit in the main body of the image forming apparatus according to the third embodiment. <{0000074}> [Embodiments for Carrying out the Invention]

[0009] <First Embodiment> The first embodiment will be described with reference to FIGS. 1 to 8. First, the schematic configuration of the image forming apparatus (image forming system) of the present embodiment will be described with reference to FIG. 1. <00..00082> [Image Forming Apparatus] FIG. 1 is a schematic cross-sectional view of an image forming apparatus 100 including an image forming apparatus main body 101 according to the present embodiment. The image forming apparatus main body 101 includes an image forming unit 102 that transfers a toner image onto a fed sheet S, and a fixing conveyance unit 103 that fixes the transferred toner image onto the sheet S. The image forming unit 102 and the fixing conveyance unit 103 are each composed of an independent housing. With this configuration, even for a large-sized apparatus, it is possible to perform packing and transportation in a separated state for each housing, and the workability during logistics until installation can be improved.

[0011] Above the image forming unit 102, a document reading device 104 that reads a document image, and a document feeding device 105 that feeds a plurality of stacked documents one by one to the document reading device 104 are selectively connected.

[0012] Upstream of the image forming unit 102 in the sheet S conveyance direction (hereinafter referred to as the sheet conveyance direction), it is possible to selectively connect any one of a high-capacity feeder 106 having a storage unit for a plurality of sheets S, a manual feeder (not shown), or a long sheet feeder (not shown) capable of accommodating a long sheet S. Further upstream of the high-capacity feeder 106, it is possible to selectively connect in series any one of a high-capacity feeder, a manual feeder, or a long sheet feeder (not shown).

[0013] Downstream of the fixing conveyance unit 103 in the sheet conveyance direction, a sensing device 107 for reading the fixed toner image formed on one or both sides of the sheet S, detecting deviations in image density and image position, and performing feedback correction on the image signal transmitted to the image forming unit 102 is selectively connected. Further downstream of the fixing conveyance unit 103 or the sensing device 107, one or a plurality of various sheet processing devices (not shown) such as an inserter, a puncher, a bookbinding machine, a high-capacity stacker, a folder, a finisher, a trimmer, etc. can be selectively connected in combination.

[0014] As described above, by selectively connecting various option devices to the image forming apparatus main body 101 of the present embodiment, it becomes possible to output inline a product obtained by performing various post-processing on various materials, and to provide an image forming apparatus (image forming system) 100 excellent in high productivity, high image quality, high stability, and high functionality.

[0015] [Image Forming Unit] Next, the schematic configuration of the image forming unit 102 will be described with reference to FIGS. 2, 3(a), and 3(b). FIG. 2 is a schematic cross-sectional view of the image forming unit 102 in the image forming apparatus main body 101. FIG. 3(a) is a schematic cross-sectional view showing the image forming stations 200Y, 200M, and 200C for the color images of yellow (Y), magenta (M), and cyan (C), and FIG. 3(b) is a schematic cross-sectional view showing the image forming station 200K for black (K). Note that FIG. 3(a) shows the image forming station 200Y for yellow as a representative.

[0016] As shown in Figure 2, the image forming unit 102 is equipped with multiple image forming stations 200Y, 200M, 200C, and 200K, which form different toner images for each color: yellow (Y), magenta (M), cyan (C), and black (K). Since the basic configuration of each color image forming station is the same, the yellow image forming station 200Y will be described below as a representative example of the color image forming stations. Furthermore, the basic configuration for image forming is the same for both the color image forming station and the black image forming station, with the only main difference being the size of the photosensitive drum.

[0017] The photosensitive drums 201Y and 201K, which serve as the image carrier and photoreceptor, are uniformly charged on their surfaces by primary chargers 202Y and 202K, after which an electrostatic latent image is formed by laser scanners 203Y and 203K, which are driven based on the transmitted image information signal. In this embodiment, the color primary charger 202Y is a charging roller positioned in contact with or close to the photosensitive drum 201Y, and the black primary charger 202K is a corona charger; however, the primary charger may be either a charging roller or a corona charger.

[0018] The latent images formed on the photosensitive drums 201Y and 201K are developed as toner images by the developing units 204Y and 204K. The toner consumed during development is replenished as needed from the toner bottles 205Y and 205K to the developing units 204Y and 204K via the toner replenishment paths 206Y and 206K. The toner images on the photosensitive drums 201Y and 201K are sequentially transferred onto the intermediate transfer belt 208 by the primary transfer rollers 207Y and 207K, which apply a predetermined pressure and electrostatic load bias. After transfer, any small amount of remaining toner on the photosensitive drums 201Y and 201K is removed by the photosensitive drum cleaners 209Y and 209K, in preparation for the next image formation. The removed remaining toner is collected in the toner recovery container 211 via the toner recovery path 210.

[0019] Meanwhile, the sheets S, fed one by one by the sheet storage section 212 inside the image forming section 102 or by one of the externally connected paper feeding devices mentioned above, are corrected for skew by forming a loop with their leading edge following the nip portion of the registration roller 213. Subsequently, the registration roller 213 transports the sheets S to the secondary transfer section in synchronization with the toner image on the intermediate transfer belt 208. The secondary transfer outer roller 215 presses against the intermediate transfer belt 208, which is supported from the inside of the intermediate transfer belt 125 by the secondary transfer inner roller 214, forming a secondary transfer nip portion N1 between itself and the intermediate transfer belt 208.

[0020] The toner image on the intermediate transfer belt 208 is transferred to the sheet S by applying a predetermined pressure and electrostatic load bias at the secondary transfer nip section N1. The secondary transfer section, which serves as the transfer section in this embodiment, is composed of the secondary transfer inner roller 214, the intermediate transfer belt 208, and the secondary transfer outer roller 215. After transfer, any small amount of residual toner remaining on the intermediate transfer belt 208 is removed by the intermediate transfer belt cleaner 216, in preparation for the next image formation. The removed residual toner is collected in the toner recovery container 211 via the toner recovery path 210. The sheet S on which the toner image has been transferred is transported to the downstream fixing transport section 103 by the pre-fixing transport section 410, which serves as the transport section.

[0021] [Fusing and transport section] Figure 4 is a schematic cross-sectional view of the fixing and transport section 103 in the main body 101 of the image forming apparatus according to this embodiment. The fixing section (fixing device) 50 shown in Figure 4 comprises a heating roller 51 as a first rotating body equipped with a heater 51a as a heat source inside, and an opposing roller 52 as a second rotating body arranged to contact the heating roller 51 and forming a fixing nip section N2 that grips and transports the sheet between itself and the heating roller 51. The fixing section 50 fixes the toner image on the sheet S, which is transported from the image forming section 102 to the fixing nip section N2, by heating and pressurizing it. The sheet S heated by the fixing section 50 is cooled by the heat absorption of a heat sink 303 disposed inside the cooler 302, and is discharged via the discharge transport path 304 to the sensing device 107 or a sheet processing device (not shown).

[0022] When discharging the sheet S with its front and back sides reversed, a switchback transport is performed at the double-sided reversal unit 306, and the leading and trailing ends of the sheet S are swapped, and the sheet S is discharged via the reversal transport path 305 and the discharge transport path 304 with its front and back sides reversed.

[0023] When image formation is performed on both sides of sheet S, the sheet S with the first image formed is transported via a switchback mechanism in the double-sided reversal unit 306, reversing the front and rear ends of the sheet S and transporting it to the double-sided transport path 307. Then, in conjunction with the timing of subsequent sheets S fed by either the sheet S storage unit 212 inside the image forming unit 102 or one of the externally connected paper feeding devices mentioned above, the sheets are rejoined by the registration roller 213, where image formation is performed on the second side using the same process as the first side, and the sheets are then discharged via the discharge transport path 304.

[0024] The image forming apparatus body 101 of this embodiment can perform full-color image forming using all of the aforementioned image forming stations 200Y, 200M, 200C, and 200K, as well as monochrome image forming using only the K image forming station 200K.

[0025] During black and white image formation, the primary transfer rollers 207Y, 207M, 207C, the primary transfer auxiliary roller 218, and the intermediate transfer belt 208 are displaced to the positions shown by the dashed lines in Figure 2 by a separation mechanism (not shown). This mechanism allows the Y, M, and C image forming stations 200Y, 200M, and 200C, which are separated from the intermediate transfer belt 208, to stop their rotational drive. In other words, unnecessary wear of parts due to unnecessary rotational drive can be prevented in the Y, M, and C image forming stations 200Y, 200M, and 200C, thereby extending their lifespan.

[0026] On the other hand, the K series photosensitive drum 201K is configured with a larger diameter, which is more suitable for a longer lifespan than the Y, M, and C series photosensitive drums 201Y, 201M, and 201C. Furthermore, the K series primary charger 202K is configured with a non-contact method using a corona charger, which is more suitable for a longer lifespan than the roller charger contact method used in the Y, M, and C series primary chargers 202Y, 202M, and 202C. In addition, the K series toner bottle 205K is configured with a larger capacity, which is more suitable for a longer lifespan than the Y, M, and C series toner bottles 205Y, 205M, and 205C.

[0027] With the above configuration, even for users who frequently use monochrome image formation, it is possible to prevent the maintenance interval of the frequently used K image formation station 200K from becoming shorter than that of the less frequently used Y, M, and C image formation stations 200Y, 200M, and 200C. Furthermore, the large-diameter drum configuration using a corona charger has a wider charging width and is more suitable for high-speed operation than the small-diameter drum configuration using a roller charger, thus improving productivity during monochrome image formation.

[0028] In the image forming unit 102, where different conditions exist between image forming stations 200Y to 200K, differences in toner charge on the photosensitive drums 201Y to 201K may occur due to differences in shape and wear. If differences in toner charge occur, the transfer of the toner image to the sheet S may not be uniform in the secondary transfer process, resulting in image defects. Therefore, the photosensitive drum 201K of the K unit is equipped with a pre-transfer charger 220 consisting of a corona charger to match the toner charge of the photosensitive drums 201Y, 201M, and 201C of the Y, M, and C units.

[0029] As described above, according to the configuration of this embodiment, it is possible to provide an image forming apparatus body 101 that excels in high productivity, high image quality, high stability, and long lifespan not only in full-color image forming but also in monochrome image forming.

[0030] [Pre-fixing transport section] Next, refer to Figure 5. , as a belt suction conveying unit The detailed configuration of the pre-fixing transport unit 410 and its surroundings will be described. Figure 5 is a cross-sectional view showing the secondary transfer unit, the pre-fixing transport unit 410, and the fixing unit 50. In recent years, there has been a demand for equipment that achieves high image quality, high productivity, and high image position accuracy. To achieve high image quality, it is important to keep the orientation of the sheet constant after transfer and before fixing. It is also important to stably supply an appropriate amount of heat to the sheet in order to maintain uniform glossiness and other properties. Furthermore, to achieve high image position accuracy, it is important to transport the sheet without skew, rotation, or oblique feeding. However, in the case of a compact image forming apparatus, for example, where the distance from the transfer unit to the fixing unit is short, the sheet will be nipped and transported simultaneously in both the transfer unit and the fixing unit.

[0031] On the other hand, the transfer unit transfers the toner image to the sheet, making it difficult to fine-tune the sheet transport speed. Also, the fuser unit's roller outer diameter expands due to heat, making it difficult to maintain a constant sheet transport speed. Therefore, when the sheet is transported simultaneously by the transfer unit and the fuser unit, there are issues such as poor image quality due to pulling and pushing, and sheet rotation during transport, i.e., the image becoming skewed. For this reason, in this embodiment, a pre-fusing transport unit 410 is provided between the secondary transfer unit and the fuser unit 50, thereby increasing the distance from the secondary transfer unit to the fuser unit 50 and avoiding the aforementioned problems.

[0032] In the sheet transport direction FD, a transfer guide 219 is provided between the pre-fixing transport section 410 and the secondary transfer nip section N1 to guide the sheet being transported from the secondary transfer nip section N1 toward the pre-fixing transport section 410. Also, in the sheet transport direction FD, a transfer guide 219 is provided between the pre-fixing transport section 410 and the fixing nip section N2 to guide the sheet being transported by the pre-fixing transport section 410 toward the fixing nip section N2. As a guide before establishment A fixing entrance guide 53 is provided.

[0033] As shown in Figure 5, the pre-fixing transport section 410 is positioned lower than the secondary transfer nip section N1 and the fixing nip section N2. With this configuration, the leading edge of the sheet that has passed through the secondary transfer nip section N1 is transported towards the pre-fixing transport section 410 along the transfer guide 219. The pre-fixing transport section 410 transports the sheet towards the fixing section 50 along the sheet transport surface 410a. The fixing inlet guide 53 is a guide surface that guides the leading edge of the sheet transported along the sheet transport surface 410a toward the fixing nip section N2. (Guide surface) It has 53a. Guide surface of fixing entrance guide 53 53a In the sheet transport direction FD, it is downstream of the pre-fixing transport section 410 and upstream of the fixing nip section N2, on the sheet transport surface 410a It was extended toward the guide surface 53a.It intersects with the virtual line 410a'. With this configuration, the leading edge of the sheet being transported from the pre-fixing transport section 410 to the fixing section 50 comes into contact with the fixing entrance guide 53, and the sheet's orientation conforms to the fixing entrance guide 53, so that the sheet is properly introduced into the fixing nip section N2. In other words, it is possible to avoid image defects caused by unfixed toner on the sheet coming into contact with the heating roller 51, as well as transport defects such as wrinkles and corner folds.

[0034] The pre-fixing transport unit 410 is, as a belt The conveyor belt 411 and the drive roller 412 and driven rollers 412a, 412b, and 412c, which serve as tensioning members for rotatably tensioning the conveyor belt 411, are included. The pre-fixing conveyor unit 410 also includes a drive motor 413 as a driving means for rotating the drive roller 412 to rotate the conveyor belt 411. The conveyor belt 411 is an endless belt with numerous holes formed therein, and is a breathable material that allows air to pass between the inside and outside of the circumferential surface of the conveyor belt 411 through the holes. Furthermore, the inside of the circumferential surface of the conveyor belt 411 is used to attach a sheet to the circumferential surface of the conveyor belt 411. suck A suction fan 414 is positioned as a pulling mechanism. The suction fan 414 can draw air from the outside to the inside of the circumferential surface of the conveyor belt 411 through numerous holes formed in the conveyor belt 411, thereby applying a suction force to the circumferential surface of the conveyor belt 411 for conveying the sheet. As a result, the pre-fixing conveying section 410 uses the suction fan 414 to attract the sheet onto the conveyor belt 411 (on the belt), and the drive motor 413 rotates the conveyor belt 411 to convey the sheet.

[0035] Here, if a configuration in which a pre-fixing transport unit 410 is provided between the secondary transfer unit and the fixing unit 50 is arranged in a single housing, the device becomes larger, and the ease of transporting and installing the device decreases. For this reason, in this embodiment, the secondary transfer unit and the pre-fixing transport unit 410 are supported in the first housing 102a, which is the housing of the image forming unit 102, and the fixing unit 50 is supported in the second housing 103a, which is the housing of the fixing transport unit 103. Then, when installing the device, the image forming unit 102 is connected to the fixing transport unit 103 to form the main body of the image forming apparatus 101. In other words, the main body of the image forming apparatus 101 is divided into multiple modular devices to improve the ease of transporting and installing the device.

[0036] As explained in Figure 2, the first housing 102a contains the components for transferring the toner image to the sheet S and the components for fixing the toner image to the sheet, including each image forming station 200Y, 200M, 200C, 200K, an intermediate transfer belt 208, a sheet S storage section 212, and a pre-fixing transport section 410. As explained in Figure 4, the second housing 103a contains the components for fixing the toner image to the sheet and then discharging it, including a fixer section 50, a cooler 302, and an discharge transport path 304. By connecting the first housing 102a to the second housing 103a, the sheet can be transported from the pre-fixing transport section 410 supported by the first housing 102a to the fixer section 50 supported by the second housing 103a.

[0037] In this configuration, where the image forming apparatus body 101 is divided into multiple modular devices, there are many parts between the pre-fixing transport unit 410 supported by the first housing 102a and the fixing entrance guide 53 provided on the fixing unit 50 supported by the second housing 103a, resulting in large dimensional tolerances. Specifically, the tolerances of the support configuration of the pre-fixing transport unit 410 to the first housing 102a, the connection configuration between the first housing 102a and the second housing 103a, and the support configuration of the fixing unit 50 to the second housing 103a all exist between the pre-fixing transport unit 410 and the fixing entrance guide 53 of the fixing unit 50.

[0038] Furthermore, the accumulation of these numerous tolerances may lead to sheet transport defects and image defects such as those described below. For example, if the pre-fusing transport section 410 is excessively low in height relative to the fuser entrance guide 53, the leading edge of the sheet will not contact the fuser entrance guide 53 and will instead get stuck between the fuser entrance guide 53 and the pre-fusing transport section 410, causing the sheet to jam. Conversely, if the pre-fusing transport section 410 is excessively high in height relative to the fuser entrance guide 53, the leading edge of the sheet will not contact the fuser entrance guide 53 and will instead be introduced into the fuser nip section N2, resulting in image defects caused by unfusing toner on the sheet coming into contact with the heating roller 51, or transport defects such as wrinkles and corner folds.

[0039] Therefore, in this embodiment, the pre-fixing transport unit 410 is pivotably supported on the first housing 102a, and the pre-fixing transport unit 410 is positioned by bringing a part of the pre-fixing transport unit 410 into contact with a positioning member 131a provided on the second housing 103a. This configuration will be explained below with reference to Figures 5 to 8.

[0040] [Positioning configuration of the pre-fixing transport unit] Referring to Figures 5 to 7, a configuration will be described in which the oscillating pre-fixing transport unit 410 is appropriately positioned when the image forming unit 102 and the fixing transport unit 103 are connected. Figure 6 is a cross-sectional view of the first housing 102a of the image forming unit 102, the positioning unit 131 fixed to the fixing transport unit 103, and the pre-fixing transport unit 410, viewed from the bottom surface of the main body 101 of the image forming apparatus. Figure 7 is a view of the positioning unit 131 having a positioning member 131a, viewed from the transport direction. The second housing 103a supporting the fixing unit 50 is connected to the first housing 102a such that a part of the pre-fixing transport unit 410 enters the interior, so that a sheet is transported from the pre-fixing transport unit 410 to the fixing unit 50.

[0041] The pre-fixing transport unit 410 is, As the first positioning unitThe first housing 102a is pivotably supported by the pivot support portion 415, with the pivot axis α (the central axis of the first pivot support member 415a and the second pivot support member 415b) located along the sheet width direction (vertical direction in Figure 6) which intersects (orthogonal in this embodiment) with the sheet transport direction FD. As a result, the pre-fixing transport unit 410 is positioned vertically and horizontally by the rocking support unit 415 provided on the first housing 102a. The predetermined vertical direction is the direction along the plane perpendicular to the width direction of the sheet, which is perpendicular to the sheet transport direction FD. The swinging support section 415 is a first support member that swingably supports the pre-fixing conveying section 410 on both sides of the pre-fixing conveying section 410 in the sheet width direction. (First pivot axis) First swing support member 415a and second support member as (Second pivot axis) It has a second swing support member 415b. The first swing support member 415a and the second swing support member 415b have their central axes on the same straight line parallel to the sheet width direction. The pre-fixing transport section 410 has a contact portion 416 that, when the first housing 102a and the second housing 103a are connected, at least a part of it penetrates the second housing 103a.

[0042] On the other hand, the second enclosure 103a , covered Positioning member 131 as contact portion a A positioning member 131 is provided as a second positioning part. The positioning member 131a contacts a contact part 416 provided on a part of the pre-fixing transport part 410, thereby positioning the pre-fixing transport part 410 in the swing direction around the swing axis α. That is, the pre-fixing transport part 410 is positioned vertically by the positioning member 131 provided on the second housing 103a. In this embodiment, the positioning member 131a is provided below the pre-fixing transport part 410 and supports a part of the pre-fixing transport part 410 by contacting the contact part 416 from below. As a result, the pre-fixing transport part 410 is supported at a total of three points: two-point swing support by the first swing support member 415a and the second swing support member 415b, and one-point support by the contact between the contact part 416 and the positioning member 131a.

[0043] Alternatively, the pre-fixing transport section 410 may be biased by a spring or the like so that the downstream side of the sheet transport direction FD is directed upward around the pivot axis α, and the pre-fixing transport section 410 may be positioned by restricting this upward swing with a positioning member.

[0044] The positioning configuration of the pre-fixing transport unit 410 in this embodiment will be described in more detail. The pre-fixing transport unit 410 has a front and rear side in the sheet width direction perpendicular to the sheet transport direction FD, on the upstream side in the sheet transport direction FD. as a pivot axis It is equipped with one first swing support member 415a and one second swing support member 415b. The front and rear sides in the sheet width direction correspond to the front and rear sides of the image forming apparatus body 101, respectively. The front side of the image forming apparatus body 101 is the side operated by the user, and for example, an operation panel for operating the image forming apparatus 100 is located there. Similarly, the rear side is the back side of the image forming apparatus body 101.

[0045] The first swing support member 415a and the second swing support member 415b are swingably supported relative to the first housing 102a. In this embodiment, the first swing support member 415a and the second swing support member 415b are axial in shape, and the member provided in the first housing 102a is shaped like a hole to swing them. However, the swing support configuration of the pre-fixing transport section 410 is not limited to this, and a hole shape may be provided in the pre-fixing transport section 410, and the axial first swing support member 415a and the second swing support member 415b may be provided protruding from the first housing 102a.

[0046] Furthermore, the pre-fixing transport unit 410 is equipped with a contact portion (oscillation restricting member) 416 located downstream in the sheet transport direction FD and approximately in the center of the pre-fixing transport unit 410 in the sheet width direction. As described above, the contact portion 416 contacts the positioning member 131a to restrict the oscillation of the pre-fixing transport unit 410. Thus, the pre-fixing transport unit 410 is supported at three points: two oscillation support members 415a and 415b and one contact portion (oscillation restricting member) 416. This three-point support suppresses twisting within the pre-fixing transport unit 410 and has the effect of making it less likely for the transport belt 411 of the pre-fixing transport unit 410 to shift. From the viewpoint of preventing belt shifting, it is desirable to have only one contact portion 416, but the arrangement is not limited to this, and multiple contact portions 416 may be arranged in the sheet width direction.

[0047] As shown in Figure 5, the positioning member 131a is attached to the fixing and transport section support column 132, which is provided on the surface of the second housing 103a that meets the first housing 102a, in the same phase as the contact portion 416 in the sheet width direction. As shown in Figure 7, the positioning section 131 has a positioning member 131a, a shaft 131b that rotatably supports the positioning member 131a, and a support member 131c that supports the shaft 131b. The shaft 131b is a rotation axis arranged along the sheet width direction, and the positioning member 131a is rotatable around this rotation axis. Subordinate It is a roller. In addition to a rotatable roller, the positioning member 131a may be a cylindrical member or a semi-cylindrical member with a smooth surface that is easy to slide, as long as it is configured to reduce the sliding resistance with the contact portion 416 of the pre-fixing transport section 410 when connecting the first housing 102a and the second housing 103a, as will be described later.

[0048] Such a positioning member 131a is provided so as to be adjustable in the vertical direction (height direction) relative to the second housing 103a. Specifically, the support member 131c is provided with an adjustment range so that the positioning member 131a can be adjusted in the height direction. That is, the support member 131c is attached to the anchoring and transporting column 132 by a bolt 131e via an elongated hole 131d that is long in the vertical direction. Therefore, by changing the fixing position of the bolt 131e relative to the elongated hole 131d, the height direction position of the positioning member 131a, which is supported by the support member 131c via an axis 131b, can be adjusted.

[0049] As a result, the positioning member 131a can be assembled to the second housing 103a with its height adjusted so that it maintains a constant height relationship with the fixing entrance guide 53 to the pre-fixing transport section 410. This suppresses variations in dimensional tolerances in the height direction from the contact portion 416 to the fixing entrance guide 53. Here, even if there are variations in the angle of the sheet transport surface 410a or variations in the sheet posture due to curling of the sheet's leading edge, caused by variations in tolerances in the height direction from the contact portion 416 to the sheet transport surface 410a, the angle and width of the guide surface 53a are set so that the leading edge of the sheet contacts the guide surface 53a of the fixing entrance guide 53.

[0050] Next, the positioning behavior of the pre-fixing transport unit 410 when the first housing 102a and the second housing 103a are brought closer together and connected will be explained using Figure 8. Figure 8 shows a cross-sectional view of the pre-fixing transport unit 410 in a state where its oscillation is restricted by its own weight by the oscillation restricting unit 221. That is, the pre-fixing transport unit 410 has an oscillation restricting unit 221 that can restrict the oscillation range around the oscillation axis α when the first housing 102a is not connected to the second housing 103a. The oscillation range by the oscillation restricting unit 221 is set so that the positioning member 131a can come into contact with the contact part 416 when the first housing 102a is connected to the second housing 103a.

[0051] Specifically, the oscillation restricting unit 221 has a restricting plate portion 222 and a stepped screw 223 as a restricting shaft portion. The restricting plate portion 222 is fixed to the first housing 102a so as to be able to restrict the oscillation range of the pre-fixing transport unit 410 by receiving the weight of the pre-fixing transport unit 410. The restricting plate portion 222 has, Holes (first hole, second hole) that engage with the first swing support member 415a and the second swing support member 415b A through hole 222a is formed, and a first swing support member 415a and a second swing support member 415b are inserted into the through hole 222a. As a result, the pre-fixing transport section 410 is swingably supported relative to the regulating plate section 222.

[0052] The regulating plate portion 222 has an engagement hole 222b formed along an arc centered on the pivot axis α. The frame supporting the tension roller of the pre-fixing transport portion 410 is also provided with screw holes. With the first pivot support member 415a and the second pivot support member 415b inserted into the through hole 222a of the regulating plate portion 222, the stepped screw 223 is passed through the engagement hole 222b and fastened together with the regulating plate portion 222 to the screw hole of the pre-fixing transport portion 410. As a result, the stepped screw 223 can pivot within the engagement hole 222b along an arc centered on the pivot axis α, and the pre-fixing transport portion 410 can pivot within the engagement range of the stepped screw 223 and the engagement hole 222b. When the image forming unit 102 is viewed on its own, the pre-fixing transport unit 410 can swing within the restricted range of the swing restricting unit 221 (i.e., the engagement range of the stepped screw 223 and the engagement hole 222b), and its swinging is restricted by its own weight by the swing restricting unit 221.

[0053] In this embodiment, the oscillation range is restricted by a stepped screw, but the oscillation restriction configuration is not limited to this, and any member capable of restricting the oscillation range of the pre-fixing transport unit 410 or the first housing 102a may be provided.

[0054] On the other hand, the contact portion 416 has a positioning surface 416a and a guide surface 416b. The positioning surface 416a contacts the positioning member 131a to position the pre-fixing transport portion 410. The guide surface 416b is provided downstream of the positioning surface 416a in the sheet transport direction FD and guides the positioning member 131a to the positioning surface 416a when connecting the first housing 102a to the second housing 103a. This contact portion 416 is substantially trapezoidal when viewed from the sheet width direction and is made of a material with good sliding properties. Furthermore, the guide surface 416b is formed to incline upward as it moves downstream in the sheet transport direction FD.

[0055] The upper oscillation restriction position of the oscillation restriction section 221 is such that when the first housing 102a and the second housing 103a are connected, the outer circumferential surface of the positioning member 131a and the guide surface 416b of the contact section 416 come into contact. In other words, when the first housing 102a and the second housing 103a are connected with the pre-fixing transport section 410 in a state where oscillation due to its own weight is restricted, or in other words, with the stepped screw 223 engaged with the upper edge of the engagement hole 222b, the oscillation range of the pre-fixing transport section 410 is restricted so that the guide surface 416b comes into contact with the positioning member 131a.

[0056] In this embodiment, with this configuration, when connecting the first housing 102a and the second housing 103a, the contact portion 416 of the pre-fixing transport unit 410 that has entered the second housing 103a first 、 The guide surface 416b contacts the positioning member 131a. Furthermore, the pre-fixing transport section 410 is in contact with the second housing 103a of Inside Department As it enters the area, the guide surface 416b slides against the positioning member 131a, and the pre-fixing transport section 410 is pushed upward. With the first housing 102a and the second housing 103a connected, the positioning member 131a is positioned on the positioning surface 416a, and the pre-fixing transport section 410 is positioned in the oscillating direction. At this time, the guide surface 416b and the positioning surface 416a come into smooth contact with the positioning member 131a.

[0057] Furthermore, when connecting the first housing 102a and the second housing 103a, they may be misaligned in the front-rear direction. The contact portion 416 is given a certain width in the front-rear direction so that the outer surface of the positioning member 131a and the guide surface 416b of the contact portion 416 come into contact within the range of this expected misalignment.

[0058] With the above configuration, when the first housing 102a and the second housing 103a are connected, the pre-fixing transport unit 410 swings smoothly, and the height of the fixing unit 50 relative to the fixing entrance guide 53 is appropriately determined. That is, when the first housing 102a and the second housing 103a are connected, the contact portion 416 rides up on the positioning member 131a, restricting the swinging of the pre-fixing transport unit 410. Then, the guide surface 53a of the fixing entrance guide 53 and the imaginary line 410a' of the sheet transport surface 410a of the pre-fixing transport unit 410 intersect at an appropriate point.

[0059] In this embodiment, the positioning of the pre-fixing transport unit 410 relative to the fixing unit 50 is performed by contact between a positioning member 131a provided on the second housing 103a and a contact portion 416 provided on the pre-fixing transport unit 410. Therefore, the number of members present between the pre-fixing transport unit 410 and the fixing unit for positioning can be reduced, and the tolerance for positioning can be reduced. As a result, in a configuration in which the pre-fixing transport unit 410 and the fixing unit 50 are supported by separate housings and these housings are connected, the occurrence of sheet transport defects and image defects can be suppressed.

[0060] Therefore, in this embodiment, even large devices can be packaged and transported in a state where the device is separated into multiple modules, improving workability during logistics until installation, while suppressing image defects such as wrinkles and corner folds caused by unfixed toner on the sheet coming into contact with the heating roller 51, thereby improving image quality.

[0061] <Second Embodiment> A second embodiment will be described using Figures 9 and 10. In the first embodiment described above, the case where there is one pre-fixing transport unit 410 was described. In contrast, in this embodiment, multiple pre-fixing transport units are arranged between the secondary transfer unit and the fixing unit 50. The other configurations and operations are the same as in the first embodiment described above, so the same components are denoted by the same reference numerals, and their description and illustration are omitted or simplified. The following description will focus on the differences from the first embodiment.

[0062] First, if a jam occurs around the pre-fixing transport section where the sheet gets stuck, it is desirable to perform jam removal with the pre-fixing transport section and its surrounding units pulled out in order to improve jam removal efficiency. However, if a configuration is adopted in which a part of the pre-fixing transport section 410 in the first housing 102a is positioned by contacting the positioning member 131a in the second housing 103a, as in the first embodiment, the pre-fixing transport section 410 is positioned straddling the first housing 102a and the second housing 103a. In this case, the pre-fixing transport section 410 is hidden by the support column of the frame of the first housing 102a, and the pre-fixing transport section 410 cannot be pulled out.

[0063] Furthermore, as described in the first embodiment, the orientation of the sheet as it enters the fixing unit 50 is also important for improving image quality, so the fixing unit 50 and the upstream pre-fixing transport unit 410 are required to have a highly accurate relative position. In other words, if the unit needs to be pulled out to improve jam handling performance, and if the relative position of the fixing unit 50 and the upstream pre-fixing transport unit 410 is required to be highly accurate, it is desirable that the pre-fixing transport unit be configured to be divided into two or more transport units.

[0064] Therefore, in this embodiment, in addition to the first pre-fixing transport unit 430, which is a first transport unit corresponding to the pre-fixing transport unit 410 of the first embodiment, a second pre-fixing transport unit 420 is provided as a second transport unit. Figure 9 is a schematic cross-sectional view of the image forming apparatus (image forming system) 100A having the image forming apparatus body 101A of this embodiment. Figure 10 is a cross-sectional view showing the secondary transfer unit, the first pre-fixing transport unit 430, the second pre-fixing transport unit 420, and the fixing unit 50.

[0065] In the sheet transport direction FD, a second pre-fixing transport unit 420 is positioned upstream of the sheet transport direction FD, and a first pre-fixing transport unit 430 is positioned downstream of the sheet transport direction FD. Specifically, the second pre-fixing transport unit 420 is positioned between the first pre-fixing transport unit 430 and the secondary transfer unit in the sheet transport direction FD, and transports the sheet onto which the toner image has been transferred in the secondary transfer unit toward the first pre-fixing transport unit 430. The second pre-fixing transport unit 420 is supported so as to be insertable and removable from the first housing 102a. Specifically, the second pre-fixing transport unit 420 is supported by the first housing 102a so as to be able to be pulled out from the first housing 102a for jamming. The second pre-fixing transport unit 420 can be pulled out from the front of the first housing 102a by opening the front door of the image forming unit 102, for example, and pushed inward when storing it in the first housing 102a.

[0066] The first pre-fixing transport unit 430 is pivotably supported on the first housing 102a, similar to the pre-fixing transport unit 410 described in the first embodiment, and is positioned in the pivoting direction by a positioning member 131a. That is, the support configuration and positioning configuration of the first pre-fixing transport unit 430 are the same as those of the pre-fixing transport unit 410 in the first embodiment. Specifically, the first pre-fixing transport unit 430 is pivotably supported on the first housing 102a by a pivoting support unit 435, with a pivot axis α along the sheet width direction that intersects (orthogonal in this embodiment) with the sheet transport direction FD. The configuration of the pivoting support unit 435 is the same as that of the pivoting support unit 415 in the first embodiment. In addition, the first pre-fixing transport unit 430 has a contact portion 436 that, when the first housing 103a and the second housing 103a are connected, at least a part of it penetrates the second housing 103a. The configuration of the contact portion 436 is the same as that of the contact portion 416 in the first embodiment.

[0067] On the other hand, the second housing 103a is provided with a positioning member 131a. The positioning member 131a contacts a contact portion 436 provided on a part of the first pre-fixing transport section 430, thereby positioning the first pre-fixing transport section 430 in the direction of oscillation around the oscillation axis α. The positioning member 131a has the same configuration as in the first embodiment and is attached to the fixing transport section support column 132 provided on the surface of the second housing 103a that joins with the first housing 102a, in the same phase as the contact portion 436 in the sheet width direction.

[0068] In the sheet transport direction FD, a transfer guide 219 is provided between the second pre-fixing transport section 420 and the secondary transfer nip section N1 to guide the sheet being transported from the secondary transfer nip section N1 toward the second pre-fixing transport section 420. Also in the sheet transport direction FD, a fixing inlet guide 53 is provided between the first pre-fixing transport section 430 and the fixing nip section N2 to guide the sheet being transported by the first pre-fixing transport section 430 toward the fixing nip section N2. As shown in Figure 10, the upstream end of the second pre-fixing transport section 420 is positioned lower than the secondary transfer nip section N1 when viewed in the width direction of the sheet perpendicular to the sheet transport direction FD. With this configuration, the leading edge of the sheet that has passed through the secondary transfer nip section N1 is transported toward the second pre-fixing transport section 420 along the transfer guide 219.

[0069] The upstream end of the first pre-fixing conveying section 430 is positioned lower than the downstream end of the second pre-fixing conveying section 420 in order to receive the sheet from the second pre-fixing conveying section 420. With this configuration, the leading edge of the sheet that has passed through the second pre-fixing conveying section 420 is conveyed toward the first pre-fixing conveying section 430.

[0070] The first pre-fixing transport unit 430 transports the sheet towards the fixer unit 50 along the sheet transport surface 430a. The fixer entrance guide 53 has a guide surface 53a that guides the leading edge of the sheet transported along the sheet transport surface 430a toward the fixer nip section N2. The guide surface of the fixer entrance guide 53 is downstream of the first pre-fixing transport unit 430 and upstream of the fixer nip section N2 in the sheet transport direction FD, and intersects with the imaginary line 430a' of the sheet transport surface 430a. With this configuration, the leading edge of the sheet transported from the first pre-fixing transport unit 430 to the fixer unit 50 comes into contact with the fixer entrance guide 53, and the orientation of the sheet conforms to the fixer entrance guide 53, so that the sheet is correctly introduced into the fixer nip section N2. In other words, it is possible to suppress image defects caused by unfixed toner on the sheet coming into contact with the heating roller 51, as well as transport defects such as wrinkles and corner folds.

[0071] The second pre-fixing conveying unit 420 includes a conveying belt 421 and a drive roller 422 and driven rollers 422a, 422b, and 422c as tensioning members that rotatably tension the conveying belt 421. The second pre-fixing conveying unit 420 also includes a drive motor 423 that rotates the drive roller 422 to rotate the conveying belt 421. The conveying belt 421 is an endless belt with numerous holes formed therein, and is a breathable material that allows air to pass between the inside and outside of the circumferential surface of the conveying belt 421 through the holes. A suction fan 424 is also positioned on the inside of the circumferential surface of the conveying belt 421 as an air suction unit that attracts the sheet to the circumferential surface of the conveying belt 421. The suction fan 424 can draw air from the outside to the inside of the circumferential surface of the conveying belt 421 through the numerous holes formed in the conveying belt 421, thereby applying suction force to convey the sheet to the circumferential surface of the conveying belt 421. As a result, the second pre-fixing transport unit 420 uses a suction fan 424 to attract the sheet onto the transport belt 421, and the drive motor 423 rotates the transport belt 421 to transport the sheet.

[0072] The components of the first pre-fixing conveying unit 430 are the same as those of the pre-fixing conveying unit 410 described in the first embodiment. Specifically, the first pre-fixing conveying unit 430 includes a conveying belt 431 and a drive roller 432 and driven rollers 432a, 432b, and 432c as tensioning members that rotatably tension the conveying belt 431. The first pre-fixing conveying unit 430 also includes a drive motor 433 that rotates the drive roller 432 to rotate the conveying belt 431. Furthermore, a suction fan 434 is arranged on the inside of the circumferential surface of the conveying belt 431 as an air suction unit that attracts the sheet to the circumferential surface of the conveying belt 431. The components of the fixing conveying unit 103 and the fixing unit 50 are also the same as those described in the first embodiment.

[0073] With the above configuration, in this embodiment, in addition to the effects described in the first embodiment, jam handling performance can be improved. In this embodiment, a configuration with two pre-fixing transport units has been described, but a configuration with three or more pre-fixing transport units may also be used. In that case, the pre-fixing transport unit located furthest downstream between the secondary transfer unit and the fixing unit 50 in the sheet transport direction FD shall have a support configuration and positioning configuration similar to the pre-fixing transport unit 410 in the first embodiment.

[0074] <Third Embodiment> A third embodiment will be described using Figures 11 and 12. In the first and second embodiments described above, a configuration was described in which the image forming unit 102 is directly connected to the fixing and transport unit 103. In contrast, in this embodiment, the image forming unit 102 and the fixing and transport unit 103 are connected via an intermediate transport unit 108. The other configurations and operations are the same as in the second embodiment described above, so the same reference numerals are used for similar components, and their description and illustration are omitted or simplified. The following description will focus on the differences from the second embodiment.

[0075] For high image quality and high productivity, it is desirable for the distance between the secondary transfer nip section N1 and the fixing nip section N2 to be approximately 19.2 inches (= 487.7 mm), which is generally referred to as a standard size. Therefore, in the second embodiment described above, the distance L1 between the secondary transfer nip section N12 and the fixing nip section N2 is set to approximately 500 mm, which is 19 inches (483 mm) or more. Therefore, even with the configuration of the second embodiment, if the length of the sheet in the transport direction FD is 19 inches or less, the sheet is transported without being pinched by both the secondary transfer nip section N1 and the fixing nip section N2. In other words, in the case of a sheet length of 19 inches, the secondary transfer nip section N1 and the fixing nip section N2 do not nip the sheet simultaneously, thus avoiding image defects and providing high-quality, high-precision deliverables.

[0076] However, in recent years, there has been a growing demand for electrophotographic image forming apparatuses that can form images not only on standard-sized sheets, but also on so-called long sheets, where the length of the sheet in the transport direction is longer than that of a standard-sized sheet. On the other hand, in the case of sheets with a length exceeding 19 inches, which are generally called long sheets, in the configuration of the second embodiment, the secondary transfer nip section N1 and the fixing nip section N2 nip the sheet simultaneously. Furthermore, if the sheet speed at the fixing nip section N2 (fixing transport speed VF) is faster than the sheet transport speed at the secondary transfer nip section N1 (transfer transport speed VT), the fixing section 50 will pull the sheet.

[0077] The clamping force of the fuser unit 50 on the sheet is designed to be greater than the clamping force of the secondary transfer unit on the sheet in order to fix the toner to the sheet. Therefore, the sheet passing through the secondary transfer unit may be pulled by the fuser unit 50, which may cause a transfer failure of the toner image carried on the intermediate transfer belt 208.

[0078] Furthermore, if the sheet comes into contact with the heating roller 51 against unfixed toner on the sheet upstream of the fixing nip section N2 in the transport direction, the image quality may deteriorate.

[0079] On the other hand, if the transfer transport speed VT is faster than the fuser transport speed VF, the sheet may be pushed back by the leading edge of the sheet hitting the fuser nip N2, potentially causing a transfer failure of the toner image carried on the intermediate transfer belt 208.

[0080] In contrast, if the distance L1 between the secondary transfer nip section N1 and the fixing nip section N2 is set to approximately 800 mm, which is common for long sheets of 30 inches (762 mm) or more, the image defects and other problems described above can be avoided. However, if the distance L1 is increased in this way, the image forming section 102 or the fixing and transport section 103 that make up the main body 101 of the image forming apparatus becomes a large device, and the work of transporting and installing the device takes time.

[0081] Therefore, in this embodiment, an intermediate transport unit 108, which is a separate module from the image forming unit 102 and the fixing transport unit 103, is placed between them to increase the distance L1 between the secondary transfer nip unit N1 and the fixing nip unit N2. That is, in this embodiment, the image forming apparatus body 101B is composed of three divided modules: the image forming unit 102, the intermediate transport unit 108, and the fixing transport unit 103. Also, in this embodiment, the housing 108a of the intermediate transport unit 108 corresponds to the first housing, the housing 103b of the fixing transport unit 103 corresponds to the second housing, and the housing 102b of the image forming unit 102 corresponds to the third housing.

[0082] Furthermore, in this embodiment, in addition to the first pre-fixing transport unit 460 which corresponds to the first transport unit 410 of the first embodiment, there is a third pre-fixing transport unit 450 which corresponds to the third transport unit, and a second pre-fixing transport unit 440 which corresponds to the second pre-fixing transport unit 420 of the second embodiment. That is, the second pre-fixing transport unit 440, the third pre-fixing transport unit 450, and the first pre-fixing transport unit 460 are arranged from the upstream side in the sheet transport direction.

[0083] The configuration of this embodiment will be explained with reference to Figures 11 and 12. Figure 11 is a schematic cross-sectional view of an image forming apparatus (image forming system) 100B having the main body 101B of this embodiment. Figure 12 is a cross-sectional view showing the secondary transfer section, the second pre-fixing transport section 440, the third pre-fixing transport section 450, the first pre-fixing transport section 460, and the fixing section 50.

[0084] In the sheet transport direction FD, between the secondary transfer section and the fixing section 50, there is a second pre-fixing transport section 440 located on the upstream side of the sheet transport direction FD, a first pre-fixing transport section 460 located on the downstream side, and a third pre-fixing transport section 450 located between the second pre-fixing transport section 440 and the first pre-fixing transport section 460. The second pre-fixing transport section 440 is supported by a housing 102b, which is a third housing, so that it can be pulled out and jammed, similar to the second pre-fixing transport section 420 described in the second embodiment.

[0085] The third pre-fixing transport section 450 is fixedly supported to the housing 102b. That is, the housing 102b supports the secondary transfer section, the second pre-fixing transport section 440, and the third pre-fixing transport section 450. Furthermore, the housing 102b is positioned upstream of the housing 108a in the sheet transport direction FD, and is connected to the housing 108a such that a part of the third pre-fixing transport section 450 enters the interior of the housing 108a, thereby allowing the sheet to be transported from the third pre-fixing transport section 450 to the first pre-fixing transport section 460. In addition, the third pre-fixing transport section 450 may be pivotably supported to the housing 102b, similar to the pre-fixing transport section 410 described in the first embodiment, and its positioning in the pivoting direction may be performed by a positioning member provided on the housing 108a of the intermediate transport section 108.

[0086] When viewed in the width direction of the sheet, perpendicular to the sheet transport direction FD, the upstream end of the first pre-fixing transport section 460 is positioned lower than the downstream end of the third pre-fixing transport section 450 in order to receive the sheet from the third pre-fixing transport section 450. With this configuration, the leading edge of the sheet that has passed through the third pre-fixing transport section 450 is transported toward the first pre-fixing transport section 460.

[0087] The first pre-fixing transport unit 460 transports the sheet towards the fixer unit 50 along the sheet transport surface 460a. The fixer entrance guide 53 has a guide surface 53a that guides the leading edge of the sheet transported along the sheet transport surface 460a toward the fixer nip section N2. The guide surface 53a of the fixer entrance guide 53 is downstream of the first pre-fixing transport unit 460 in the sheet transport direction FD, and intersects with the imaginary line 460a' of the sheet transport surface 460a upstream of the fixer nip section N2. With this configuration, the leading edge of the sheet transported from the first pre-fixing transport unit 460 to the fixer unit 50 comes into contact with the fixer entrance guide 53, and the orientation of the sheet conforms to the fixer entrance guide 53, so that the sheet is correctly introduced into the fixer nip section N2. In other words, it is possible to avoid image defects caused by unfixed toner on the sheet coming into contact with the heating roller 51, as well as transport defects such as wrinkles and corner folds.

[0088] The configurations provided in the second pre-fixing transport unit 440 and the third pre-fixing transport unit 450 are the same as those of the second pre-fixing transport unit 420 described in the second embodiment. Furthermore, the configurations provided in the first pre-fixing transport unit 460 are the same as those of the pre-fixing transport unit 410 described in the first embodiment.

[0089] Specifically, the second pre-fixing conveying section 440, the third pre-fixing conveying section 450, and the first pre-fixing conveying section 460 each include conveying belts 441, 451, and 461, and drive rollers 442, 452, and 462, and driven rollers 442a, 452a, 462a, 442b, 452b, 462b, 442c, 452c, and 462c, which serve as tensioning members for rotatably tensioning the conveying belts 441, 451, and 461. Furthermore, the second pre-fixing conveying section 440, the third pre-fixing conveying section 450, and the first pre-fixing conveying section 460 each include drive motors 443, 453, and 463, which rotate the drive rollers 442, 452, and 462 to rotate the conveying belts 441, 451, and 461. Furthermore, suction fans 444, 454, and 464 are positioned on the inner side of the circumferential surfaces of the conveyor belts 441, 451, and 461, serving as air suction units to attract the sheets to the circumferential surfaces of the conveyor belts 441, 451, and 461.

[0090] The first pre-fixing transport unit 460 is pivotably supported on the housing 108a of the intermediate transport unit 108. The components of the first pre-fixing transport unit 460 are the same as those of the pre-fixing transport unit 410 described in the first embodiment. However, in this embodiment, unlike the first embodiment, the first pre-fixing transport unit 460 is supported on the housing 108a of the intermediate transport unit 108.

[0091] Specifically, the first pre-fixing transport unit 460 is pivotably supported by a swinging support unit 465 around a swing axis α along the sheet width direction which intersects (orthogonal in this embodiment) with the sheet transport direction FD, relative to the housing 108a. The configuration of the swinging support unit 465 is the same as that of the swinging support unit 415 in the first embodiment. Furthermore, the first pre-fixing transport unit 460 has a contact portion 466 that, at least a part of it, penetrates the housing 103b when the housing 108a and housing 103b are connected. The configuration of the contact portion 466 is the same as that of the contact portion 416 in the first embodiment.

[0092] On the other hand, the housing 103b is provided with a positioning member 131a. The positioning member 131a contacts a contact portion 466 provided on a part of the first pre-fixing transport section 460, thereby positioning the first pre-fixing transport section 460 in the direction of oscillation around the oscillation axis α. The positioning member 131a has the same configuration as in the first embodiment and is attached to the fixing transport section support column 132 provided on the surface of the housing 103b that meets the housing 108a, in the same phase as the contact portion 466 in the sheet width direction.

[0093] Furthermore, the configurations provided in the fixing transport section 103 and the fixing section 50 are the same as those described in the first embodiment. Here, the fixing entrance guide 53 is configured such that even if there are variations in the angle of the sheet transport surface 430a due to variations in the height tolerance from the contact section 466 to the sheet transport surface 460a of the first pre-fixing transport section 460, or variations in the sheet posture due to upward or downward curling of the sheet tip, the tip of the sheet will contact the guide surface of the fixing entrance guide 53. The angle and width of the guide surface 53a of the fixing entrance guide 53 are set accordingly.

[0094] When the housings 108a and 103b are brought close together and connected, the positioning behavior of the first pre-fixing transport unit 460 is the same as that of the first embodiment. However, it differs from the first embodiment in that the swing restricting member is fixedly supported to the housing 108a. With this configuration, when the housings 108a and 103b are connected, the first pre-fixing transport unit 460 swings smoothly, its height is determined, and the guide surface 53a of the fixing entrance guide 53 and the imaginary line 460a' of the sheet transport surface 460a of the first pre-fixing transport unit 460 intersect at an appropriate point.

[0095] As described above, in this embodiment, in addition to the effects described in the second embodiment, image quality can be improved even with 30-inch (762 mm) sheets, which are often used as long sheets. Specifically, an intermediate transport section 108 is added between the secondary transfer nip section N1 and the fixing nip section N2, and the sheet is transported via the third pre-fixing transport section 450. As a result, sufficient distance can be secured between the secondary transfer nip section N1 and the fixing nip section N2, and even when transporting long sheets, image defects caused by the secondary transfer nip section N1 and the fixing nip section N2 nipping the sheet simultaneously can be suppressed.

[0096] In this embodiment, the distance between the secondary transfer nip section N1 and the fixing nip section N2 is set to approximately 800 mm. However, if a longer sheet is to be used, another intermediate transport section may be added between the secondary transfer nip section N1 and the fixing nip section N2 to increase the number of pre-fixing transport sections between the secondary transfer nip section N1 and the fixing nip section N2. In that case, the pre-fixing transport section located furthest downstream between the secondary transfer section and the fixing section 50 in the sheet transport direction FD shall have a support configuration and positioning configuration similar to the pre-fixing transport section 410 in the first embodiment.

[0097] Furthermore, the configuration of this embodiment may be applied to the configuration of the first embodiment. That is, the above-described intermediate transport unit 108 may be added between the image forming unit 102 and the fixing transport unit 103. In other words, in the configuration shown in Figures 11 and 12 above, the second pre-fixing transport unit 440 may be omitted, and the sheet may be directly transported from the transfer guide 219 to the third pre-fixing transport unit 450. [Explanation of Symbols]

[0098] 50... Fixing section 51...Heating roller (first rotating body) 52... Opposing roller (second rotating body) 53...Fixed entrance guide 102a...First enclosure 102b... Cabinet (3rd cabinet) 103a...Second enclosure 103b... Cabinet (Second Cabinet) 108a... Cabinet (First Cabinet) 131a... Positioning member 221...Oscillation regulating section 410...Pre-fixing transport section (transport section) 411, 431, 461... Conveyor belts (belts) 412, 432, 462... Drive rollers (tensioning members) 412a, 412b, 412c, 432a, 432b, 432c, 462a, 462b, 462c... Driven rollers (tensioning members) 413, 433, 463... Drive motors (driving means) 414, 434, 464... Suction fan (air intake section) 415, 435, 465... Oscillating support parts 415a...First oscillating support member (first support member) 415b...Second oscillating support member (second support member) 416, 436, 466...Contact part 416a... Positioning surface 416b... Guide surface 420, 440...Second pre-fixing transport section (Second transport section) 430, 460...First pre-fixing transport section (first transport section) 450...Third pre-fixing transport section (Third transport section)

Claims

1. A transfer unit that transfers the toner image onto the sheet, A fixing unit that fixes the toner image transferred to the sheet by the transfer unit onto the sheet, A belt suction conveying unit is positioned between the transfer unit and the fixing unit in the sheet conveying direction and has a belt unit and a suction unit that sucks the sheet to the belt unit by sucking air, wherein the belt suction conveying unit conveys the sheet sucked to the belt unit toward the fixing unit by rotating the belt unit, The first enclosure and The system comprises a second housing connected to the first housing and supporting the fixing portion, The belt suction conveying unit is supported by the first housing in a state in which it can swing freely about a pivot axis that extends in the sheet width direction intersecting the sheet conveying direction. The second housing is provided with a rotating member for positioning the belt suction conveying unit in the vertical direction. The belt suction conveying unit has a positioning surface that contacts the rotating member to position the belt suction conveying unit in the vertical direction, and a guide surface provided downstream of the positioning surface in the sheet conveying direction, which guides the rotating member toward the positioning surface when the first housing and the second housing are connected. An image forming apparatus characterized by the following:

2. The belt suction conveying unit includes the swing shaft, The first housing has a hole formed therein that engages with the pivot shaft. The image forming apparatus according to feature 1.

3. The first housing is provided with the pivot shaft, The belt suction conveying unit is provided with a hole that engages with the oscillating shaft. The image forming apparatus according to feature 1.

4. The aforementioned rotating member is a driven roller, The image forming apparatus according to any one of claims 1 to 3, characterized in that when the second housing is connected to the first housing, the driven rollers rotate in contact with the guide surface, thereby guiding the belt suction conveying section into the interior of the second housing, and the driven rollers pivot around the pivot axis, and the vertical positioning is performed by the driven rollers contacting the positioning surface.

5. The image forming apparatus according to any one of claims 1 to 4, characterized in that the rotating member is provided so as to be able to adjust its vertical position relative to the second housing.

6. The system further includes a pre-fixing guide having a guide surface that guides the sheet conveyed by the belt suction conveying unit toward the fixing unit, The image forming apparatus according to any one of claims 1 to 5, characterized in that the guide surface intersects with a virtual line extended toward the guide surface from the conveying surface that adsorbs and conveys the sheet of the belt portion.

7. The image forming apparatus according to any one of claims 1 to 6, characterized in that the transfer unit is supported by the first housing.

8. The image forming apparatus according to any one of claims 1 to 7, characterized in that, when the belt suction transport unit is designated as the first transport unit, it further comprises a second transport unit which is arranged between the first transport unit and the transfer unit in the sheet transport direction and transports the sheet on which the toner image has been transferred by the transfer unit toward the first transport unit.

9. The image forming apparatus according to claim 8, characterized in that the second transport unit is supported so as to be insertable and removable from the first housing.

10. A third housing supporting the transfer section, The sheet further comprises a third conveying unit, which is positioned between the first conveying unit and the second conveying unit in the sheet conveying direction and conveys the sheet from the second conveying unit toward the first conveying unit, The image forming apparatus according to claim 8 or 9, characterized in that the first housing is positioned between the third housing and the second housing in the sheet transport direction and is connected to the third housing and the second housing, respectively.

11. The pivot shaft has a first pivot shaft and a second pivot shaft that pivotably support the belt suction conveying section on both sides in the sheet width direction. The aforementioned hole portion has a first hole portion that engages with the first pivot shaft and a second hole portion that engages with the second pivot shaft. The image forming apparatus according to feature 2 or 3.

12. The belt suction conveying unit has a swing restricting unit that can restrict the swing range around the swing axis when the first housing and the second housing are not connected, The oscillation range controlled by the oscillation restricting unit is configured such that the rotating member can contact the guide surface when the first housing and the second housing are connected. The image forming apparatus according to any one of claims 1 to 11.

13. A transfer unit for transferring a toner image to a sheet, A fixing unit that fixes the toner image transferred to the sheet by the transfer unit onto the sheet, A belt suction conveying unit is positioned between the transfer unit and the fixing unit in the sheet conveying direction and has a belt unit and a suction unit that sucks the sheet to the belt unit by sucking air, wherein the belt suction conveying unit conveys the sheet sucked to the belt unit toward the fixing unit by rotating the belt unit, The first enclosure and A second housing connected to the first housing and supporting the fixing part, When the belt suction transport unit is designated as the first transport unit, the system includes a second transport unit positioned between the first transport unit and the transfer unit in the sheet transport direction, which transports the sheet on which the toner image has been transferred by the transfer unit toward the first transport unit. The first housing has a first positioning unit that positions the belt suction conveying unit in a predetermined direction along a plane perpendicular to the width direction of the sheet, which is perpendicular to the sheet conveying direction, The second housing has a second positioning unit that positions the belt suction conveying unit in the predetermined direction, The second transport unit is supported in a manner that allows it to be inserted into and removed from the first housing. An image forming apparatus characterized by the following:

14. A transfer unit for transferring a toner image to a sheet, A fixing unit that fixes the toner image transferred to the sheet by the transfer unit onto the sheet, A belt suction conveying unit is positioned between the transfer unit and the fixing unit in the sheet conveying direction and has a belt unit and a suction unit that sucks the sheet to the belt unit by sucking air, wherein the belt suction conveying unit conveys the sheet sucked to the belt unit toward the fixing unit by rotating the belt unit, The first enclosure and A second housing connected to the first housing and supporting the fixing part, When the belt suction transport unit is designated as the first transport unit, a second transport unit is provided, which is positioned between the first transport unit and the transfer unit in the sheet transport direction, and which transports the sheet on which the toner image has been transferred by the transfer unit toward the first transport unit. A third housing supporting the transfer section, The system includes a third conveying unit positioned between the first conveying unit and the second conveying unit in the sheet conveying direction, which conveys the sheet from the second conveying unit toward the first conveying unit. The first housing has a first positioning unit that positions the belt suction conveying unit in a predetermined direction along a plane perpendicular to the width direction of the sheet, which is perpendicular to the sheet conveying direction, The second housing has a second positioning unit that positions the belt suction conveying unit in the predetermined direction, The first housing is positioned between the third housing and the second housing in the sheet transport direction and is connected to the third housing and the second housing, respectively. An image forming apparatus characterized by the following:

15. A transfer unit for transferring a toner image to a sheet, A fixing unit that fixes the toner image transferred to the sheet by the transfer unit onto the sheet, A belt suction conveying unit is positioned between the transfer unit and the fixing unit in the sheet conveying direction and has a belt unit and a suction unit that sucks the sheet to the belt unit by sucking air, wherein the belt suction conveying unit conveys the sheet sucked to the belt unit toward the fixing unit by rotating the belt unit, The first enclosure and The system comprises a second housing connected to the first housing and supporting the fixing portion, The first housing has a first positioning unit that positions the belt suction conveying unit in a predetermined direction along a plane perpendicular to the width direction of the sheet, which is perpendicular to the sheet conveying direction, The second housing has a second positioning unit that positions the belt suction conveying unit in the predetermined direction, The aforementioned belt suction conveying unit is The belt suction conveying section is pivotably supported by a pivot shaft extending in the sheet width direction intersecting the sheet conveying direction, and a hole that engages with the pivot shaft, Contact part and, The first housing has a swing restricting unit that can restrict the swing range around the swing axis when the first housing is not connected to the second housing, The first positioning portion is the other of the pivot shaft and the hole portion, The second positioning portion is the contacted portion against which the contact portion makes contact. The oscillation range of the oscillation restricting unit is configured such that the contacted portion can come into contact with the contacted portion when the first housing is connected to the second housing. An image forming apparatus characterized by the following:

Images