Image forming apparatus

Abstract

This suppresses clogging of waste toner in the branch lines of the recovery pipeline due to the effects of heat from the fuser unit. [Solution] The image forming apparatus 100 includes an image forming unit P equipped with a plurality of discharge units 6, 4, and 7 for discharging waste toner, a fixing device 9, a plurality of branch pipes 83a, 83b, and 83c through which the waste toner discharged from the plurality of discharge units 6, 4, and 7 falls, a confluence pipe 84 that receives waste toner from the plurality of branch pipes 83a, 83b, and 83c, and a transport means 86 for transporting the waste toner inside the confluence pipe 84. The plurality of branch pipes 83a, 83b, and 83c and the confluence pipe 84 are located above the heating rotating body 91, and the plurality of branch pipes 83a, 83b, and 83c are arranged in a position that does not overlap with the heating rotating body 91 in the horizontal plane.

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus such as a copying machine using an electrophotographic method or an electrostatic recording method, a printer, a facsimile apparatus, or a multifunction peripheral having a plurality of these functions. [Background Art]

[0002] An image forming apparatus such as a printer using an electrophotographic method sometimes has a configuration including a recovery pipe passage that includes a plurality of branch pipes respectively connected to a plurality of discharge portions that discharge waste toner, and a merging pipe connected to the plurality of branch pipes. The plurality of discharge portions are, for example, a cleaning device that recovers waste toner from a photoreceptor or an intermediate transfer belt, or a developing device. The waste toner discharged from the plurality of discharge portions moves through the respective branch pipes to the merging pipe. The waste toner that has moved to the merging pipe is conveyed by a screw conveying mechanism provided in the merging pipe and recovered into a common waste toner container.

[0003] In an image forming apparatus having such a configuration, when the recovery pipe passage is arranged in a range affected by heat from a fixing device, softened waste toner may accumulate on the pipe wall of the recovery pipe passage and the like, which may interfere with the conveyance of waste toner.

[0004] In contrast, Patent Document 1 discloses a configuration including a merging pipe duct provided to form a double-pipe structure around the merging pipe, and a branch pipe duct provided to form a double-pipe structure around the branch pipe. The temperature-increased air in the merging pipe duct is exhausted to the outside of the housing of the image forming apparatus through the branch pipe duct by an air flow generated by an airflow forming fan or natural convection. [Prior Art Documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Laid-Open No. 2010-91750 [Summary of the Invention] [Problems that the invention aims to solve]

[0006] In recent years, the heat generated by the fixing unit has tended to increase with the speed of processing in image forming machines. On the other hand, with the demand for miniaturization of image forming machines, it has become difficult to secure an insulating barrier or sufficient distance between the recovery pipeline and the fixing unit.

[0007] In configurations where the recovery pipeline is located close to the fuser unit, the heat from the fuser unit has a greater impact on the waste toner in contact with the pipe wall of the recovery pipeline. In particular, in branch pipelines where waste toner falls due to gravity, the waste toner tends to soften and accumulate on the pipe wall. This makes the branch pipelines more prone to clogging with waste toner.

[0008] The configuration described in Patent Document 1 requires the installation of a duct surrounding the recovery pipeline within the housing of the image forming apparatus, which can lead to increased equipment costs and a larger overall size.

[0009] Therefore, the objective of the present invention is to suppress clogging of waste toner in the branch pipeline of the recovery pipeline due to the influence of heat from the fixing device. [Means for solving the problem]

[0010] The above objective is achieved by the image forming apparatus according to the present invention. In summary, the present invention provides an image forming apparatus comprising: an image forming unit for forming a toner image on a recording material, the image forming unit having a plurality of discharge units for discharging waste toner; a fixing device for fixing the toner image formed by the image forming unit to a recording material, the fixing device having a heating rotating body for applying heat to the recording material; a plurality of branch pipes connected to each of the plurality of discharge units, the waste toner discharged from the plurality of discharge units falling through the interior of each branch pipe; a confluence pipe connected to the plurality of branch pipes, the confluence pipe for receiving waste toner from each of the plurality of branch pipes; and a transport means for transporting the waste toner inside the confluence pipe, wherein the plurality of branch pipes and the confluence pipe are located above the heating rotating body, and the plurality of branch pipes are arranged in a position that does not overlap with the heating rotating body in the horizontal plane. [Effects of the Invention]

[0011] According to the present invention, it is possible to suppress clogging of waste toner in the branch pipeline of the recovery pipeline due to the influence of heat from the fixing device. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic cross-sectional view of an image forming apparatus. [Figure 2] This is a schematic cross-sectional view of the fixing device. [Figure 3] This is a schematic perspective view of a waste toner collection system. [Figure 4] This is a schematic cross-sectional view of the recovery pipeline. [Figure 5] This is a schematic cross-sectional side view showing the positional relationship between the recovery pipeline and the fixing device in the embodiment. [Figure 6] This is a schematic cross-sectional side view showing the positional relationship between the recovery pipeline and the fixing device in a modified example. [Figure 7] This is a schematic cross-sectional view showing the positional relationship between the recovery pipeline and the fixing device in the embodiment. [Figure 8]This is a schematic cross-sectional side view showing the positional relationship between the recovery pipeline and the fixing device in the comparative example. [Modes for carrying out the invention]

[0013] The image forming apparatus according to the present invention will be described in more detail below with reference to the drawings.

[0014] [Example 1] <Image forming apparatus> Figure 1 is a schematic cross-sectional view of the image forming apparatus 100 of this embodiment. The image forming apparatus 100 of this embodiment is a digital printer employing an intermediate transfer method that can form a black (K) image on a sheet-like recording material S using an electrophotographic method. The image forming apparatus 100 can form an image based on image information transmitted from an external device, such as a personal computer connected to the image forming apparatus 100.

[0015] The image forming apparatus 100 will be described as being installed and used on a horizontal plane. The arrangement and orientation of each component in the image forming apparatus 100 described below are those that would occur if the image forming apparatus 100 were installed on a horizontal plane. For the image forming apparatus 100 and its elements, the front side of Figure 1 is the "front" side, the back side of Figure 1 is the "rear" side, the right side in Figure 1 is the "right" side, and the left side in Figure 1 is the "left" side. The direction perpendicular to the plane of Figure 1 (front-back direction) connecting the front and rear sides of the image forming apparatus 100 is assumed to be approximately parallel to the rotation axis direction of the photosensitive drum 1 (described later) and the rotation axis direction of the tension roller of the intermediate transfer belt 30 (described later). Furthermore, the up and down direction refers to the up and down in the direction of gravity (vertical direction), but does not mean only directly above and directly below, but also includes the sides above and below the horizontal plane through which the position or element of interest passes.

[0016] An image forming apparatus 100 includes an image forming portion P that forms a black (K) image on a recording material S. In this embodiment, the image forming portion P includes a photosensitive drum 1, a charging roller 2, an exposure device 3, a developing device 4, a drum cleaning device 6, a developer supplying device 11, an intermediate transfer unit 35, an external secondary transfer roller 32, and the like.

[0017] The photosensitive drum 1, which is a rotatable drum-type (cylindrical) photoconductor (electrophotographic photoconductor) serving as a first image bearing member, rotates in the direction of arrow R1 (counterclockwise direction) in FIG. 1. The surface of the rotating photosensitive drum 1 is uniformly charged to a predetermined potential of a predetermined polarity (negative polarity in this embodiment) by the charging roller 2, which is a roller-type charging member serving as a charging means. During charging, a charging voltage (charging bias) including a DC component having the same polarity as the charging polarity of the photosensitive drum 1 is applied to the charging roller 2. The charged surface of the photosensitive drum 1 is scan-exposed according to image information (image signal) by the exposure device 3 serving as an exposure means, and an electrostatic latent image (electrostatic image) corresponding to the image information is formed on the photosensitive drum 1.

[0018] The electrostatic latent image formed on the photosensitive drum 1 is developed (visualized) by the development device 4, which is a developing means, when toner is supplied, and a toner image (toner image, developer image) is formed on the photosensitive drum 1. In this embodiment, the development device 4 uses a two-component developer containing toner (non-magnetic toner particles) and carrier (magnetic carrier particles) as the developer. The development device 4 has a developing container 4a that contains the developer, and a developing sleeve 4b as a developer carrier (developing member) that is rotatably supported in the developing container 4a. The developing sleeve 4b carries the developer and rotates to transport the developer toward the photosensitive drum 1. The development device 4 supplies toner from the developer carried in the developing sleeve 4b onto the photosensitive drum 1 according to the electrostatic latent image on the photosensitive drum 1. During development, a developing voltage (developing bias) containing a DC component of the same polarity (negative polarity in this embodiment) as the charge polarity of the photosensitive drum 1 is applied to the developing sleeve 4b. In this embodiment, toner charged with the same polarity as the charging polarity of the photosensitive drum 1 adheres to the exposed area on the photosensitive drum 1, where the absolute value of the potential has decreased after being uniformly charged and then exposed (reverse development method). In this embodiment, the normal charging polarity of the toner, which is the main charging polarity of the toner during development, is negative polarity.

[0019] An intermediate transfer belt 30, which is an endless belt-shaped intermediate transfer body serving as a second image bearing member, is disposed so as to face the photosensitive drum 1. The intermediate transfer belt 30 is stretched around a secondary transfer inner roller 31, a tension roller 33, and a driving roller 34 serving as a plurality of stretching rollers. The intermediate transfer belt 30 rotates (circulates) in the direction of arrow R2 (clockwise direction) in FIG. 1 when the driving roller 34 is rotationally driven. On the inner peripheral surface side of the intermediate transfer belt 30, at a position facing the photosensitive drum 1, a primary transfer roller 5, which is a roller-type primary transfer member serving as primary transfer means, is disposed. The primary transfer roller 5 is pressed toward the photosensitive drum 1, and forms a primary transfer portion (primary transfer nip) T1 which is a contact portion between the photosensitive drum 1 and the intermediate transfer belt 30. The stretching rollers other than the driving roller 34 and the primary transfer roller 5 are driven to rotate as the intermediate transfer belt 30 rotates. The toner image formed on the photosensitive drum 1 is applied with a predetermined pressing force and electrostatic load bias by the primary transfer roller 5 at the primary transfer portion T1, and is transferred (primary transfer) onto the rotating intermediate transfer belt 30. During primary transfer, a primary transfer voltage (primary transfer bias) having a polarity opposite to the normal charging polarity of toner (positive polarity in the present embodiment) is applied to the primary transfer roller 5. Toner remaining on the photosensitive drum 1 without being transferred onto the intermediate transfer belt 30 during primary transfer (residual toner, transfer residual toner) is removed from the photosensitive drum 1 and collected by a drum cleaning device 6 serving as photosensitive member cleaning means. Further, replenishment developer containing an amount of toner corresponding to the amount consumed from the developing device 4 is replenished from the developer replenishing device 11 to the developing device 4.

[0020] On the outer circumferential surface of the intermediate transfer belt 30, a roller-type secondary transfer member, the secondary transfer outer roller 32, is positioned opposite the secondary transfer inner roller 31 via the intermediate transfer belt 30. The secondary transfer outer roller 32 is pressed toward the secondary transfer inner roller 31, forming a secondary transfer section (secondary transfer nip) T2, which is the contact point between the intermediate transfer belt 30 and the secondary transfer outer roller 32. At the secondary transfer section T2, the toner image formed on the intermediate transfer belt 30 is subjected to a predetermined pressure and electrostatic load bias by the secondary transfer outer roller 32. As a result, the toner image on the intermediate transfer belt 30 is transferred (secondary transfer) onto the recording material S, which is being transported while being held between the intermediate transfer belt 30 and the secondary transfer outer roller 32. During secondary transfer, a secondary transfer voltage (secondary transfer bias) with the opposite polarity (positive polarity in this embodiment) to the normal charging polarity of the toner is applied to the secondary transfer outer roller 32. The secondary transfer inner roller 31 is electrically grounded (connected to ground potential). In this embodiment, a secondary transfer voltage with the same polarity as the normal charging polarity of the toner may be applied to the roller corresponding to the secondary transfer inner roller 31, and the roller corresponding to the secondary transfer outer roller 32 may be electrically grounded. Toner that remains on the intermediate transfer belt 30 without being transferred to the recording material S during secondary transfer (residual toner, transferred residual toner) is removed from the intermediate transfer belt 30 and recovered by the belt cleaning device 7, which serves as an intermediate transfer body cleaning means.

[0021] Recording material (transfer material, sheet) S, such as paper or plastic sheets, is stored in a cassette 50 which serves as a recording material storage unit. This recording material S is fed out of the cassette 50 in accordance with the image formation timing by a feeding roller 60, which is a feeding member that serves as a feeding means. This recording material S passes through a transport path 61 and is transported to a register roller 62, which is a transport member that serves as a transport means. After correcting the tilt of the transported recording material S, the register roller 62 transports the recording material S to the secondary transfer unit T2 at a predetermined timing in accordance with the toner image formed on the intermediate transfer belt 30.

[0022] The recording material S onto which the toner image has been transferred is transported to a fixing device 9, which serves as a fixing means. The fixing device 9 pressurizes and heats the recording material S carrying the unfixed toner image to fix (melt and solidify) the toner image onto the recording material S. The recording material S that has undergone the toner image fixing process by the fixing device 9 is discharged (output) onto a discharge tray 51, which serves as a discharge section located outside the housing 110 of the image forming apparatus 100, by discharge rollers 63, which serve as discharge members.

[0023] In this embodiment, the photosensitive drum 1, the charging roller 2, and the drum cleaning device 6 together constitute a drum cartridge 10 that is detachable from the main body 101 of the image forming apparatus 100. In this embodiment, the developing device 4 substantially independently constitutes a developing cartridge that is detachable from the main body 101 of the image forming apparatus 100. In this embodiment, the intermediate transfer belt 30, the tensioning roller for the intermediate transfer belt 30, the primary transfer roller 5, and the belt cleaning device 7 together constitute an intermediate transfer unit 35 that is detachable from the main body 101 of the image forming apparatus 100.

[0024] Furthermore, the toner removed from the photosensitive drum 1 by the drum cleaning device 6, and the toner removed from the intermediate transfer belt 30 by the belt cleaning device 7, are collected by the waste toner collection device 8.

[0025] <Cleaning device> Next, the cleaning apparatus (drum cleaning apparatus 6, belt cleaning apparatus 7) in this embodiment will be described further.

[0026] As shown in Figure 1, the drum cleaning device 6 is positioned downstream of the primary transfer section T1 (and upstream of the charging section by the charging roller 2) in the rotational direction (surface movement direction) of the photosensitive drum 1. The drum cleaning device 6 comprises a drum cleaning container 6a and a cleaning blade 6b as a cleaning member. The cleaning blade 6b is attached to the drum cleaning container 6a so as to contact the surface of the photosensitive drum 1. The drum cleaning device 6 rubs the surface of the rotating photosensitive drum 1 with the cleaning blade 6b. In this way, the drum cleaning device 6 removes residual toner, paper dust, external additives, etc. that have adhered to the surface of the photosensitive drum 1 after passing through the primary transfer section T1, and collects them in the drum cleaning container 6a.

[0027] Furthermore, as shown in Figure 1, the belt cleaning device 7 is positioned downstream of the secondary transfer section T2 (and upstream of the primary transfer section T1) in the rotational direction (surface movement direction) of the intermediate transfer belt 30. In this embodiment, the belt cleaning device 7 is positioned opposite the tension roller 33 via the intermediate transfer belt 30. The belt cleaning device 7 cleans the image forming surface of the intermediate transfer belt 30. The belt cleaning device 7 comprises a belt cleaning container 7a and a cleaning brush 7b as a cleaning member. The cleaning brush 7b is rotatably supported in the belt cleaning container 7a so as to rotate in contact with the surface of the intermediate transfer belt 30. The belt cleaning device 7 rubs the surface of the rotating intermediate transfer belt 30 with the cleaning brush 7b. As a result, the belt cleaning device 7 removes residual toner, paper dust, external additives, etc. that have adhered to the surface of the intermediate transfer belt 30 after passing through the secondary transfer section T2, and collects them in the belt cleaning container 7a. The belt cleaning device 7 may also have a configuration that includes a cleaning blade, which serves as a cleaning member, positioned to contact the surface of the intermediate transfer belt 30.

[0028] Here, the remaining toner, paper dust, and external additives recovered by the drum cleaning device 6 and the belt cleaning device 7 are also referred to as "waste particles" or "waste toner."

[0029] <Fusing device> Next, the fixing device 9 in this embodiment will be described further. Figure 2 is a schematic cross-sectional view of the fixing device 9 in this embodiment (showing a cross-section approximately perpendicular to the rotation axis direction of the photosensitive drum 1).

[0030] In this embodiment, the image forming apparatus 100 employs a belt heating system using an endless belt member as the fixing device 9. The fixing device 9 includes a heating unit 90 that heats the recording material S, a pressure roller 96 as a pressure rotating body, and a fixing device housing 97. The heating unit 90 and the pressure roller 96 are housed inside the fixing device housing 97. The heating unit 90 includes a fixing belt 91 as a heating rotating body, a heating roller 92, an auxiliary roller 94, and a pressure pad 95, all composed of a rotatable endless belt member. The fixing belt 91 is stretched over the heating roller 92, the auxiliary roller 94, and the pressure pad 95. The heating unit 90 also has a heater 93 as a heat source inside (hollow part) of the heating roller 92. The heating roller 92 contacts the inner circumferential surface of the fixing belt 91 and heats the fixing belt 91 by being heated by the heater 93. The fixing belt 91 is made of a thin-walled cylindrical belt member that has thermal conductivity and heat resistance. The pressure roller 96 contacts the pressure pad 95 via the fixing belt 91 and together with the fixing belt 91 forms a nip section N. The pressure roller 92 is also rotationally driven, and the fixing belt 91 rotates (circularly) in accordance with the rotation of the pressure roller 92. At the nip section N, the recording material S, which is held and transported between the fixing belt 91 heated by the heating roller 92 and the pressure roller 96 that is in contact with the fixing belt 91, is heated and pressurized. As a result, a toner image is fixed (melted and solidified) on the recording material S.

[0031] In this embodiment, the fixing device 9 is configured to have a heat source only in the heating unit 90, but it is also possible to configure it to have a heat source in the pressure roller 96 as well. Alternatively, the fixing device 9 may be configured to heat and pressurize the recording material S by sandwiching and conveying the recording material S between a heating roller, which is a heating rotating body equipped with a heat source such as a heater, and a pressure roller, which is a pressing rotating body that presses against the heating roller (roller heating method).

[0032] <Waste Toner Collection System> Next, the waste toner collection device 8 in this embodiment will be described. Figure 3 is a schematic perspective view of the waste toner collection device 8 as seen from diagonally behind the image forming apparatus 100.

[0033] The waste toner collection device 8 comprises a collection pipeline (waste toner collection pipeline) 81 and a waste toner container (collection container) 82. The collection pipeline 81 comprises a plurality of branch pipelines 83 (first, second, and third branch pipelines 83a, 83b, and 83c), a confluence pipeline 84, and a connecting pipeline 85. Waste toner flows through the plurality of branch pipelines 83 to the confluence pipeline 84, and from the confluence pipeline 84 it is collected through the collection pipeline 85 to the waste toner container 82. The waste toner container 82 is detachable from the main body 101 of the image forming apparatus 100 and can be replaced with an empty one, for example, when it becomes full.

[0034] As described above, any remaining toner on the photosensitive drum 1 is removed from the photosensitive drum 1 by the drum cleaning device 6 and stored in the drum cleaning container 6a of the drum cleaning device 6. The remaining toner stored in the drum cleaning container 6a is then transported backward as waste toner by a transport member (not shown), such as a transport screw, provided inside the drum cleaning container 6a. This waste toner is then discharged into the first branch pipeline 83a through the first discharge port 6c provided at the rear end of the drum cleaning container 6a.

[0035] In this embodiment, the developing device 4 uses a two-component developer as the developer agent, and the developer in the developing container 4a of the developing device 4 contains not only toner but also a carrier for charging the toner. Friction is generated when the toner and carrier are agitated, and the toner becomes electrically charged. The toner is consumed during image formation. Then, a replenishment developer containing an amount of toner equivalent to the amount consumed is newly supplied to the developing device 4 from the developer replenishment device 11. On the other hand, the carrier is not consumed during image formation, so it may deteriorate with long-term use in the developing device 4. Therefore, in this embodiment, the developer containing the deteriorated carrier is discharged from the developing device 4, and a replenishment developer containing an amount of carrier equivalent to the amount discharged is newly supplied to the developing device 4 from the developer replenishment device 11. The developer containing the deteriorated carrier is transported backward as waste toner by a transport member (not shown), such as a transport screw, provided inside the developing container 4a. This waste toner is then discharged to the second branch pipeline 83b through a second discharge port 4c provided at the rear end of the developing container 4a.

[0036] Furthermore, as described above, any remaining toner on the intermediate transfer belt 30 is removed from the intermediate transfer belt 30 by the belt cleaning device 7 and stored in the belt cleaning container 7a of the belt cleaning device 7. The remaining toner stored in the belt cleaning container 7a is then transported as waste toner towards the rear by a transport member (not shown), such as a transport screw, provided inside the belt cleaning container 7a. This waste toner is then discharged to the third branch pipe 83c through a third discharge port 7c provided at the rear end of the belt cleaning container 7a.

[0037] Figure 4 is a schematic cross-sectional view of the recovery pipeline 81 in this embodiment (showing a view from the front of a cross-section cut approximately parallel to the direction of gravity).

[0038] A merging circuit 84 is connected to the first, second, and third branch pipes 83a, 83b, and 83c. In this embodiment, the first, second, and third branch pipes 83a, 83b, and 83c extend approximately parallel to the direction of gravity. In this embodiment, the merging pipe 84 extends in the left-right direction approximately parallel to the horizontal direction. The merging pipe 84 communicates with the first branch pipe 83a at the first inlet 84a. The merging pipe 84 also communicates with the second branch pipe 83b at the second inlet 84b. Furthermore, the merging pipe 84 communicates with the third branch pipe 83c at the third inlet 84c. The first, second, and third inlets 84a, 84b, and 84c open upwards. The first, second, and third branch pipelines 83a, 83b, and 83c are not equipped with any transporting members (or breaking down members) such as transporting screws for transporting (or breaking down) waste toner between the time it is discharged from the first, second, and third outlets 6c, 4c, and 7c and the time it joins the merging pipeline 84.

[0039] In this embodiment, the connecting conduit 85 is connected to the merging conduit 84. In this embodiment, the connecting conduit 85 extends approximately parallel to the direction of gravity. The merging conduit 84 communicates with the connecting conduit 85 at the outlet 84d. The outlet 84d opens downwards. The waste toner container 82 is connected to the connection port 85a at the end of the connecting conduit 85 opposite to the outlet 84d.

[0040] In this embodiment, the first, second, and third discharge ports 6c, 4c, and 7c are located behind the intermediate transfer belt 30 in the front-rear direction. Also in this embodiment, the first, second, and third receiving ports 84a, 84b, and 84c are located behind the intermediate transfer belt 30 in the front-rear direction. Furthermore, in this embodiment, the drop port 84d and connection port 85a are located behind the intermediate transfer belt 30 in the front-rear direction. And in this embodiment, the first, second, and third branch pipes 83a, 83b, and 83c, the merging pipe 84, and the connecting pipe 85 are each located behind the intermediate transfer belt 30 in the front-rear direction.

[0041] A transport member 86 is provided inside the confluence pipeline 84. In this embodiment, the confluence pipeline 84 is composed of a circular pipe with a substantially circular cross-section that is substantially perpendicular to its axial direction. In this embodiment, the transport member 86 is composed of a transport screw (such as a shaftless screw). The first inlet 84a is provided near the upstream end in the transport direction G of the waste toner inside the confluence pipeline 84 by the transport member 86. The second inlet 84b is provided downstream of the first inlet 84a in the transport direction G of the waste toner inside the confluence pipeline 84. The third inlet 84c is provided downstream of the second inlet 84b in the transport direction G of the waste toner inside the confluence pipeline 84. Furthermore, the drop-off port 84d is located downstream of the third receiving port 84c in the transport direction G of the waste toner inside the confluence pipeline 84, and is provided near the downstream end in the transport direction G of the waste toner inside the confluence pipeline 84. The drop-off port 84d may, for example, be provided between the second receiving port 84b and the third receiving port 84c in the transport direction G of the waste toner inside the confluence pipeline 84. In this case, the transport direction of the waste toner by the transport member 86 can be reversed for the portion transported from the first and second receiving ports 84a and 84b to the drop-off port 84d side and for the portion transported from the third receiving port 84c side to the drop-off port 84d side. For example, the transport direction of the waste toner can be reversed by reversing the winding direction of the blades of a transport screw, which rotates in a predetermined direction, as the transport member 86.

[0042] Waste toner from the drum cleaning device 6, developing device 4, and belt cleaning device 7, which serve as multiple discharge points, is discharged into the first, second, and third branch pipes 83a, 83b, and 83c, respectively, through the first, second, and third discharge ports 6c, 4c, and 7c. The waste toner discharged into the first, second, and third branch pipes 83a, 83b, and 83c falls through them by gravity. The waste toner that has fallen through the first, second, and third branch pipes 83a, 83b, and 83c moves into the merging pipe 84 through the first, second, and third receiving ports 84a, 84b, and 84c, respectively. The waste toner that has moved into the merging pipe 84 is transported by a transport member 86 and moves into the connecting pipe 85 through a drop port 84d. The waste toner that has moved into the connecting conduit 85 falls through gravity into the connecting conduit 85 and moves into the waste toner container 82 through the connection port 85a, where it is collected (stored and accumulated).

[0043] In this embodiment, the first, second, and third branch pipelines 83a, 83b, and 83c extend approximately parallel to the direction of gravity, but are not limited to this. At least one of the first, second, and third branch pipelines 83a, 83b, and 83c may extend inclined with respect to gravity in the vertical direction (along the direction of gravity) to the extent that waste toner can be moved by gravity. The angle of this inclination is not limited to this, but a range of 45 degrees or less with respect to gravity is appropriate, and is typically a range of 30 degrees or less. In addition, in this embodiment, the merging pipeline 84 extends approximately parallel to the horizontal direction, but may extend inclined with respect to the horizontal direction in a direction intersecting the direction of gravity to the extent that transport by the transport member 86 can be carried out appropriately. The angle of this inclination is not limited to this, but a range of 45 degrees or less with respect to the horizontal direction is appropriate, and is typically a range of 30 degrees or less. Furthermore, in this embodiment, the connecting pipeline 85 extends substantially parallel to the direction of gravity, but is not limited to this. It may also extend inclined with respect to the direction of gravity and in the vertical direction (along the direction of gravity) to the extent that the waste toner can move due to gravity. The angle of this inclination is not limited to this, but a range of 45 degrees or less with respect to the direction of gravity is appropriate, and is typically a range of 30 degrees or less. Also, in this embodiment, the recovery pipeline 81 is configured to have a connecting pipeline 85, but is not limited to this. For example, the recovery pipeline 81 may not have a connecting pipeline 85, and the waste toner container 82 may be directly connected to the merging pipeline 84. Also, in this embodiment, the first, second, and third branch pipelines 83a, 83b, and 83c and the merging pipeline 84 are configured as separate components, but at least one of the first, second, and third branch pipelines 83a, 83b, and 83c may be configured integrally with the merging pipeline 84. Furthermore, in this embodiment, the waste toner collection device 8 has a transport member 86 as a transport means for transporting waste toner in the confluence pipeline 84, but it is not limited to this. For example, the waste toner collection device 8 may be configured to transport waste toner in the confluence pipeline 84 by airflow. In this case, the waste toner collection device 8 is provided with a blowing means such as an air pump or a fan as a transport means.

[0044] <Positional relationship between the recovery pipeline and the fixing device> As mentioned above, with the increasing speed and miniaturization of image forming apparatuses, the recovery pipeline 81 tends to become more susceptible to the effects of heat from the fuser unit 9. In particular, since there are no transport members such as transport screws, the waste toner that passes through the branch pipeline 83 by gravity tends to accumulate on the inner wall of the branch pipeline 83, which is melted by the heat from the fuser unit 9. This makes the branch pipeline 83 prone to clogging with waste toner. In other words, because the branch pipeline 83 is not equipped with a transport member (or a breaking member), it cannot break up the solidified waste toner caused by the heat from the fuser unit 9, making it prone to waste toner clogging.

[0045] Therefore, in the image forming apparatus 100 of this embodiment, the positional relationship between the branch pipes 83 (83a, 83b, 83c) of the recovery pipe 81 and the fuser 9 makes it less susceptible to the heat from the fuser 9 affecting the waste toner in the branch pipes 83 (83a, 83b, 83c).

[0046] Figure 5 is a schematic cross-sectional side view of the recovery pipeline 81 and the fixing device 9 as seen from the front in this embodiment. As shown in Figure 5, the branch pipelines 83 (83a, 83b, 83c) and the confluence pipeline 84 of the recovery pipeline 81 are located above the fixing device 9 in the direction of gravity. More specifically, the branch pipelines 83 (83a, 83b, 83c) and the confluence pipeline 84 of the recovery pipeline 81 are located above the fixing belt 91, which acts as a heating rotating body, in the direction of gravity. Furthermore, the branch pipelines 83 (83a, 83b, 83c) are positioned so as not to overlap with the heating unit 90 of the fixing device 9 in the horizontal plane (front-back, left-right direction). In other words, the confluence pipeline 84 extends across the heating unit 90 in the horizontal plane (front-back, left-right direction), but the branch pipelines 83 (83a, 83b, 83c) are positioned so as not to overlap with the heating unit 90 in the horizontal plane. More specifically, the branch pipelines 83 (83a, 83b, 83c) of the recovery pipeline 81 are positioned so as not to overlap with the anchoring belt 91, which acts as a heating rotating body, in the horizontal plane. In other words, the merging pipeline 84 extends across the anchoring belt 91 in the horizontal plane, but the branch pipelines 83 (83a, 83b, 83c) are positioned so as not to overlap with the anchoring belt 91 in the horizontal plane. To put it another way, the statement that the first element and the second element do not overlap in the horizontal plane means that when the first element and the second element are projected perpendicularly onto a horizontal plane, the area projected by the first element and the area projected by the second element do not overlap.

[0047] In this embodiment, the heating unit 90 is located between the second branch pipe 83b and the third branch pipe 83c in the direction in which the confluence pipe 84 extends (the direction G in which waste toner is transported inside the confluence pipe 84). In other words, in the direction in which the confluence pipe 84 extends (the direction G in which waste toner is transported inside the confluence pipe 84), at least one branch pipe 83 is provided on each side of the heating unit 90.

[0048] The heat generated from the heating unit 90 of the fixing device 9 rises if airflow is not formed by an airflow-forming fan or duct. By positioning the recovery pipeline 81 and the fixing device 9 as in this embodiment, the effect of heat on the branch pipeline 83 can be suppressed even without an airflow-forming fan or duct. Furthermore, even if an airflow-forming fan or duct is provided to discharge air from inside the housing 110 of the image forming apparatus 100 to the outside of the housing 110, the heat generated from the heating unit 90 of the fixing device 9 rises after the airflow-forming fan stops because no airflow is formed. By positioning the recovery pipeline 81 and the fixing device 9 as in this embodiment, the effect of heat on the branch pipeline 83 can be suppressed even if the airflow-forming fan stops due to a power outage or jam (paper jam) processing. Furthermore, by positioning the recovery pipeline 81 and the fixing device 9 as in this embodiment, the effect of heat on the branch pipeline 83 can be suppressed, so the time from when image forming is completed until the airflow-forming fan is stopped can be shortened.

[0049] Figure 8 is a schematic cross-sectional side view of the recovery pipeline 81 and the fuser unit 9 as seen from the front in the comparative example. As shown in Figure 8, in this comparative example, the branch pipeline 83 (third branch pipeline 83c) of the recovery pipeline 81 is positioned to overlap with the heating unit 90 of the fuser unit 9 in the horizontal plane. In this case, the heat generated from the heating unit 90 of the fuser unit 9 rises and heats the third branch pipeline 83c. As a result, since there is no conveying member such as a conveying screw, the waste toner that has melted due to the heat from the fuser unit 9 tends to accumulate on the inner wall of the third branch pipeline 83c, through which the waste toner passes by gravity. This makes it easier for waste toner to clog the third branch pipeline 83c.

[0050] Figure 6 is a schematic cross-sectional side view of the recovery pipeline 81 and the fixing device 9 as seen from the front in a modified example of this embodiment. As mentioned above, the branch pipelines 83 (83a, 83b, 83c) may extend vertically at an inclination with respect to the direction of gravity. In this case as well, as shown in Figure 6, the branch pipelines 83 (for example, the second branch pipeline 83b and the third branch pipeline 83c) are positioned so as not to overlap with the heating unit 90 (fixing belt 91) in the horizontal plane over their entire length from the lower end to the upper end. In this case, as shown in Figure 6, it is preferable that the branch pipelines 83 (for example, the second branch pipeline 83b and the third branch pipeline 83c) extend at an inclination such that the upper end is further from the heating unit 90 (fixing belt 91) than the lower end. This further reduces the influence of heat from the fixing device 9 on the branch pipelines 83.

[0051] Figure 7 is a schematic cross-sectional view of the recovery pipeline 81 and the fixing device 9 in this embodiment, viewed from the right side (in the direction of arrow A in Figure 5) (i.e., along the direction in which the merging pipeline 84 extends). As shown in Figure 7, in this embodiment, the recovery pipeline 81 and the fixing device 90 (fixing device housing 97) overlap in the front-to-back direction (i.e., the horizontal plane). However, the recovery pipeline 81 and the heating unit 90 (fixing belt 91) do not overlap in the front-to-back direction (i.e., the horizontal plane). Note that the recovery pipeline 81 may be positioned so as not to overlap with the fixing device 9 (fixing device housing 97) in the front-to-back direction.

[0052] Thus, in this embodiment, the image forming apparatus 100 comprises an image forming unit P that forms a toner image on a recording material S, the image forming unit P equipped with a plurality of discharge units (drum cleaning device 6, developing device 4, belt cleaning device 7) for discharging waste toner; a fixing device 9 that fixes the toner image formed by the image forming unit P to the recording material S, the fixing device 9 equipped with a heating rotating body (fixing belt) 91 that applies heat to the recording material S; and a plurality of branch pipes 83a, 83b, 83c connected to each of the plurality of discharge units 6, 4, 7, respectively, for waste toner discharged from the plurality of discharge units 6, 4, 7 The system includes a plurality of branch pipes 83a, 83b, and 83c through which waste toner falls, a confluence pipe 84 connected to the plurality of branch pipes 83a, 83b, and 83c, the confluence pipe 84 receiving waste toner from each of the plurality of branch pipes 83a, 83b, and 83c, and a transport means (transport member) 86 for transporting the waste toner inside the confluence pipe 84. The plurality of branch pipes 83a, 83b, and 83c and the confluence pipe 84 are located above the heating rotating body 91, and the plurality of branch pipes 83a, 83b, and 83c are positioned so as not to overlap with the heating rotating body 91 in the horizontal plane. In this embodiment, the confluence pipe 84 extends so as to straddle the heating rotating body 91 in the horizontal plane, and at least one branch pipe 83a, 83b, and 83c is provided on each side of the heating rotating body 91 in the direction in which the confluence pipe 84 extends. In this embodiment, the fixing device 9 has a housing (fixing device housing) 97 that houses the heating rotating body 91, and at least one branch pipeline (all of the multiple branch pipelines 83a, 83b, and 83c in this embodiment) and a merging pipeline 84 are arranged in a position that overlaps with the housing 97 in the horizontal plane.

[0053] Furthermore, in this embodiment, at least one branch pipeline (all of the multiple branch pipelines 83a, 83b, and 83c in this embodiment) extends substantially parallel to the direction of gravity. However, at least one branch pipeline 83a, 83b, and 83c may extend vertically at an inclination with respect to the direction of gravity. In this case, it is preferable that at least one branch pipeline 83a, 83b, and 83c extending vertically at an inclination with respect to the direction of gravity is inclined such that its upper end is located further from the heating rotating body 91 than its lower end. Also in this embodiment, the image forming unit P includes a photoreceptor 1 on which a toner image is formed, an intermediate transfer belt 30 on which the toner image is transferred from the photoreceptor 1, a first cleaning device (drum cleaning device) 6 for recovering waste toner from the photoreceptor 1, and a second cleaning device (belt cleaning device) 7 for recovering waste toner from the intermediate transfer belt 30, and the multiple discharge units include the first cleaning device 6 and the second cleaning device 7. Furthermore, in this embodiment, the image forming unit P includes a developing device 4 that supplies toner to the photoreceptor 1 and forms a toner image on the photoreceptor 1, and the plurality of discharge units include the developing device 4.

[0054] As described above, according to this embodiment, even if the branch pipeline 83 is not equipped with a transport member (or a disrupting member) such as a transport screw, the branch pipeline 83 is less affected by the heat released from the fuser 9, and therefore, clogging of waste toner in the branch pipeline 83 can be suppressed.

[0055] Furthermore, according to this embodiment, clogging of waste toner in the branch pipe 83 can be suppressed without the need for a wall separating the recovery pipe 81 from the fixing device 9, or a mechanism to cover the recovery pipe 81 with a duct and force-cool it with an airflow forming fan. As a result, the image forming apparatus 100 can be made lower cost and smaller (suppressing cost increases and size increases).

[0056] [others] Although the present invention has been described above with reference to specific embodiments, the present invention is not limited to the embodiments described above.

[0057] In the above-described embodiment, the image forming apparatus was a monochrome image forming apparatus having only one photoreceptor, but the present invention can also be applied to a color image forming apparatus. In this case, a tandem configuration can be used in which a plurality of image forming units are arranged along the image forming surface of the intermediate transfer belt in the above-described embodiment. Each image forming unit is configured to have, for example, a photoreceptor and process means that act on the photoreceptor (charging means, exposure means, developing means, photoreceptor cleaning means), similar to the above-described embodiment. Here, the image forming apparatus in the above-described embodiment may be a monochrome image forming apparatus configured by retaining only the parts and units necessary for black monochrome image formation from the parts and units of such a tandem-type color image forming apparatus. In other words, the image forming apparatus in the above-described embodiment may be configured in which the elements necessary for yellow, magenta, and cyan image formation in a tandem-type color image forming apparatus are removed, and the elements necessary for black image formation are retained. In such a color image forming apparatus and a monochrome image forming apparatus, the relative positions of the primary black transfer section, the secondary transfer section, and the waste toner container within the housing of the image forming apparatus are substantially the same. The present invention can be said to be easily applicable to such monochrome image forming apparatuses.

[0058] Furthermore, although the cleaning device was described in the above embodiment as one that recovers residual toner from the image carrier, the cleaning device can also recover control toner images (toner patches). [Explanation of symbols]

[0059] 1 Photosensitive drum 4. Developing device 6. Drum cleaning device 7. Belt cleaning device 8. Waste toner collection device 9. Fixing device 81 Recovery pipeline 82 Waste toner container 83 Branch pipeline 84 Confluence pipeline 90 heating units 91 Fixing belt 96 Pressure Roller 100 Image forming apparatus

Claims

1. An image forming unit that forms a toner image on a recording material, comprising an image forming unit equipped with a plurality of discharge units for discharging waste toner, A fixing device for fixing a toner image formed by the image forming unit onto a recording material, the fixing device comprising a heating rotating body that applies heat to the recording material, A plurality of branch pipes connected to each of the plurality of discharge units, wherein the waste toner discharged from the plurality of discharge units falls through the interior of each branch pipe, A merging pipeline connected to the plurality of branch pipelines, comprising a merging pipeline that receives waste toner from each of the plurality of branch pipelines, A transport means for transporting waste toner inside the aforementioned merging pipeline, It has, The aforementioned multiple branch pipelines and the aforementioned merging pipeline are located above the heating rotating body. The image forming apparatus is characterized in that the plurality of branch lines are arranged in a position that does not overlap with the heating rotating body in the horizontal plane.

2. The image forming apparatus according to claim 1, characterized in that the merging pipeline extends so as to straddle the heating rotating body in the horizontal plane, and at least one branch pipeline is provided on each side of the heating rotating body in the direction in which the merging pipeline extends.

3. The image forming apparatus according to claim 1, wherein the fixing device has a housing for housing the heating rotating body, and at least one of the branch pipelines and the merging pipeline are arranged in a position that overlaps with the housing in the horizontal plane.

4. The image forming apparatus according to claim 1, characterized in that at least one of the branch pipes extends substantially parallel to the direction of gravity.

5. The image forming apparatus according to claim 1, characterized in that at least one of the branch pipes extends vertically at an inclination with respect to the direction of gravity.

6. The image forming apparatus according to claim 5, characterized in that at least one of the branch pipes extending vertically and inclined with respect to the direction of gravity is inclined such that its upper end is located further away from the heating rotating body than its lower end.

7. The image forming apparatus according to claim 1, wherein the image forming unit comprises a photoreceptor on which a toner image is formed, an intermediate transfer belt on which the toner image is transferred from the photoreceptor, a first cleaning device for recovering waste toner from the photoreceptor, and a second cleaning device for recovering waste toner from the intermediate transfer belt, and the plurality of discharge units include the first cleaning device and the second cleaning device.

8. The image forming apparatus according to claim 7, wherein the image forming unit has a developing device that supplies toner to the photoreceptor and forms a toner image on the photoreceptor, and the plurality of discharge units include the developing device.

Images