JP5894971B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that forms an image on a sheet.

  2. Description of the Related Art Conventionally, an apparatus described in Patent Document 1 is known as an image forming apparatus that forms an image on a sheet. In the apparatus, a fan and a duct are provided to cool the conveyance motor and the guide member that are heated in the apparatus main body of the image forming apparatus. The air flow generated by the fan is blown to the guide member from the opening opened in the duct. Further, the air flow is guided by the guide surface of the duct and guided to the transport motor.

JP 2000-304395 A

  In the technique described in Patent Document 1, when an air flow is blown from a duct to a conveyance motor or a guide member that is a cooling target, surrounding air may be involved and an unnecessary air flow may occur. As a result, there is a problem that foreign matters such as toner and dust adhere to the cooling target.

  The present invention has been made in view of the above problems, and provides an image forming apparatus that suppresses foreign air from flowing into the detection sensor when the detection sensor is cooled by an air flow. Objective.

An image forming apparatus according to an aspect of the present invention includes a sheet conveyance path in which a sheet is conveyed in a predetermined conveyance direction, a sheet conveyance path disposed opposite to the sheet conveyance path, rotationally driven about an axis, and a toner on a circumferential surface A photosensitive drum that carries an image, and a conveyance belt that is arranged to face the photosensitive drum across the sheet conveyance path, is driven to rotate, and forms a nip portion with the photosensitive drum, A transfer unit that conveys the sheet so that the sheet passes through the nip portion and transfers the toner image onto the sheet, and a transfer unit that is disposed downstream of the nip portion in the conveyance direction, and the toner image is transferred. A fixing unit that performs a fixing process on the sheet and a fixing unit that is disposed on the opposite side of the photosensitive drum from the transfer unit with a predetermined gap with respect to the transfer unit. The transported unit transports the sheet to the sheet transport path on the upstream side in the transport direction from the nip portion, and the transfer unit in a cross-sectional view intersecting the axial direction of the photosensitive drum. A detection sensor that is disposed in the transport unit and that performs a predetermined detection operation; an airflow generator that allows a cooling airflow to flow between the transfer unit and the transport unit along the axial direction; A cooling air path formed between the transfer unit and the transport unit and guiding the cooling air flow toward the detection sensor; and on the upstream side of the detection sensor in the flow path of the cooling air flow The periphery of the transfer unit and the cooling air passage intersect the axial direction through the gap between the transfer unit and the transport unit. A communication air passage for communicating along the direction, the diverter mechanism for flowing a portion of the cooling air flow that has flowed into the cooling air passage from the air flow generating unit in the communication air passage, was closed, the shunt The mechanism is disposed in the cooling air passage, and is disposed downstream of the opening in the flow path of the cooling airflow, the opening for communicating the cooling air passage and the communication air passage, And a shielding surface that shields a part of the cooling airflow .

  According to this configuration, the sheet conveyed through the sheet conveyance path is subjected to a fixing process in the fixing unit after the toner image is transferred in the nip unit. The detection sensor is disposed in the transport unit so as to face the transfer unit. Then, the cooling air flow generated by the air flow generation unit flows between the transfer unit and the transport unit, and reaches the detection sensor while being guided to the cooling air passage. For this reason, it is suppressed that the temperature of a detection sensor rises, and it is prevented that the malfunction of a detection sensor arises. On the other hand, when the cooling airflow flows between the transfer unit and the transport unit from the airflow generator, the airflow around the transfer unit is cooled through the communication air passage from the gap between the transfer unit and the transport unit. It becomes easy to flow into the air path. In particular, since the toner easily moves around the transfer unit, when the toner flows into the cooling air passage, the detection sensor is contaminated with the toner, and the detection accuracy is lowered. Further, when the air flow flows from the communication air passage into the cooling air passage, the cooling air flow is prevented from flowing into the cooling air passage. Even in such a case, according to the above configuration, the diversion mechanism causes a part of the cooling airflow that has flowed into the cooling airflow path from the airflow generation unit to flow into the communication airflow path. For this reason, an air flow is formed in the communication air passage from the cooling air passage toward the periphery of the transfer unit. As a result, the flow of air from the periphery of the transfer unit to the cooling air passage is suppressed. For this reason, the detection sensor is stably cooled by the cooling air flow, and foreign substances such as toner are prevented from adhering to the detection sensor.

Moreover, according to this structure, a part of cooling airflow flows in into a communicating air path from an opening part. At this time, since a part of the cooling air flow is shielded by the shielding surface, the air flow is retained and easily flows into the opening.

  In the above configuration, the opening is formed in a rectangular shape, has an edge on the downstream side of the flow path of the cooling air flow, and the shielding surface is directed from the edge toward the inside of the cooling air passage. It is desirable that the angle of the shielding surface with respect to the opening can be adjusted by extending and rotating the shielding surface with the edge as a fulcrum.

  According to this configuration, the amount of air flowing into the communication air passage of the cooling airflow can be adjusted by adjusting the angle of the shielding surface with respect to the opening.

  Said structure WHEREIN: The said conveyance unit is equipped with the wall part which demarcates a part of said cooling air path along the said axial direction, The said wall part forms a part of said communicating air path, The said opening part And the flow dividing mechanism includes a fixed surface fixed to the wall portion so as to cover the concave portion, and the opening and the shielding formed by cutting a part of the fixed surface. A surface.

  According to this configuration, an opening and a shielding surface can be formed by cutting a part of the fixed surface of the flow dividing mechanism.

  Said structure WHEREIN: It is desirable to provide the elastic member which is arrange | positioned downstream from the said opening part in the path | route of the flow of the said cooling airflow, and contains the said shielding surface.

  According to this configuration, since a part of the cooling airflow is shielded by the shielding surface of the elastic member, the airflow can easily flow into the opening.

  Said structure WHEREIN: The said conveyance unit is equipped with the wall part which demarcates a part of said cooling air path along the said axial direction, The said wall part forms a part of said communicating air path, The said opening part The elastic member is provided with a sheet member including a fixed surface fixed to the wall portion so as to cover the concave portion, and the opening portion opened to the fixed surface. Is preferably attached to the fixed surface on the downstream side of the opening.

  According to this configuration, by attaching the elastic member to the fixed surface of the sheet member, a part of the cooling airflow can be caused to flow into the communication air passage.

  In the above configuration, the diversion mechanism is connected to the fixed surface so as to intersect the fixed surface, and is disposed to face the transfer unit, and part of the cooling air passage along the axial direction. It is desirable to have a partition wall that defines.

  According to this configuration, the cooling airflow that has flowed into the cooling air passage can be stably guided in the axial direction toward the detection sensor.

  In the above configuration, it is preferable that the diversion mechanism is slidable in the axial direction so that an opening area communicating with the concave portion of the opening changes.

  According to this configuration, the air volume of the cooling airflow that flows into the communication air passage from the opening can be adjusted by sliding the diversion mechanism.

  In the above configuration, the transfer unit includes a notch formed so as to expose a part of the transport unit to the sheet transport path side downstream of the transport belt in the transport direction, and the detection sensor Preferably, the sheet sensor is disposed in the conveyance unit so as to face the notch portion and detects the sheet conveyed from the nip portion via the notch portion.

  According to this configuration, the sheet sensor is disposed to face the sheet conveyance path on the downstream side in the conveyance direction with respect to the conveyance belt. When the sheet subjected to the fixing process passes through the nip portion again, the heat of the sheet is transmitted to the sheet sensor, and the temperature of the sheet sensor is likely to rise. Even in such a case, since the sheet sensor is cooled by the cooling airflow, the sheet sensor stably detects that the sheet has been carried out from the nip portion.

  In the above configuration, it is preferable that the detection sensor is a density sensor that is disposed in the conveyance unit so as to face the conveyance belt and detects a density of a detection toner image formed on the conveyance belt.

  According to this configuration, the density of the detection toner image can be detected using the back side of the conveyance belt with respect to the sheet conveyance path. Further, since the concentration sensor is cooled by the cooling air flow, the concentration is stably detected. Further, even when the toner of the detection toner image rises from the conveyance belt, the toner is prevented from adhering to the density sensor by the cooling air flow.

  According to the present invention, there is provided an image forming apparatus in which when the detection sensor is cooled by an air flow, ambient air flows in and foreign matter is prevented from adhering to the detection sensor.

1 is a perspective view of an image forming apparatus according to an embodiment of the present invention. 1 is an internal cross-sectional view of an image forming apparatus according to an embodiment of the present invention. 1 is an enlarged cross-sectional view of a part of an image forming apparatus according to an embodiment of the present invention. It is sectional drawing which expanded a part of FIG. 3 further. FIG. 3 is a perspective view of a transfer unit and a conveyance unit of the image forming apparatus according to the embodiment of the present invention. FIG. 6 is a perspective view of a state where a transfer unit is removed from the transport unit of FIG. 5. FIG. 6 is a perspective view of a state where a front standing wall is removed from the transport unit of FIG. 5. FIG. 6 is a perspective view of a state where a transfer unit and a front standing wall are removed from the transport unit according to the embodiment of the invention. It is the perspective view which expanded the periphery of the airflow generation part of the conveyance unit which concerns on embodiment of this invention. It is a perspective view which shows the flow of the air in the cooling air path which concerns on embodiment of this invention. It is a side view which shows the flow of the air in the cooling air path which concerns on embodiment of this invention. It is a perspective view which shows the state by which the flow dividing mechanism was mounted | worn with the conveyance unit which concerns on embodiment of this invention. It is the (A) perspective view, (B) side view, (C) expanded view of the flow dividing mechanism which concerns on embodiment of this invention. FIG. 6 is a perspective view of a flow dividing mechanism according to a modified embodiment of the present invention.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of an image forming apparatus 1 according to an embodiment of the present invention. FIG. 2 schematically shows an internal structure of image forming apparatus 1 shown in FIG. In FIG. 2, the upper housing 22 of FIG. 1 does not appear. The image forming apparatus 1 shown in FIGS. 1 and 2 is a so-called monochrome printer, but in other embodiments, the image forming apparatus is a color printer, a facsimile machine, a multifunction machine having these functions, or a toner image. Other devices for forming the sheet may be used. Note that the terms used in the following description, such as “up”, “down”, “front”, “rear”, “left” and “right”, are merely for the purpose of clarifying the description. There is no limitation on the principle of the image forming apparatus. In the following description, the term “sheet” means copy paper, coated paper, OHP sheet, cardboard, postcard, tracing paper, other sheet material subjected to image forming processing, or any processing other than image forming processing. Means the sheet material to receive.

  The image forming apparatus 1 includes a main housing 2 having a substantially rectangular parallelepiped shape. The main housing 2 connects a substantially rectangular parallelepiped lower housing 21, a substantially rectangular parallelepiped upper housing 22 disposed above the lower housing 21, and the lower housing 21 and the upper housing 22. And a connecting housing 23. The connection housing 23 extends along the right edge and the back edge of the main housing 2. The sheet subjected to the printing process is discharged into a discharge space 24 surrounded by the lower casing 21, the upper casing 22, and the connecting casing 23.

  The operation unit 221 protruding in the front direction of the upper housing 22 includes, for example, an LCD touch panel 222. The operation unit 221 is formed so as to be able to input information related to the image forming process. For example, the user can input the number of sheets to be printed, the print density, and the like through the LCD touch panel 222. Housed in the upper housing 22 are mainly an apparatus for reading an image of a document and an electronic circuit that controls the entire image forming apparatus 1.

  A pressing cover 223 disposed on the upper housing 22 is used for pressing the document. The presser cover 223 is attached to the upper housing 22 so as to be rotatable up and down. The user rotates the holding cover 223 upward to place the document on the upper housing 22. Thereafter, the user can operate the operation unit 221 to read an image of the document on a device provided in the upper housing 22.

  A manual feed tray 240 is disposed on the right side surface of the lower housing 21. The manual feed tray 240 can be rotated up and down on the upper end 240B side with the lower end 240A (FIG. 2) as a fulcrum. The user can place a sheet on the manual feed tray 240 when the manual feed tray 240 is rotated downward and the manual feed tray 240 is in a position protruding to the right of the lower housing 21. The sheet on the manual feed tray 240 is drawn into the lower housing 21 based on an instruction input by the user through the operation unit 221, is subjected to image forming processing, and is discharged into the discharge space 24.

  With reference to FIG. 2, the image forming apparatus 1 includes a cassette 110, a paper feeding unit 11, a second paper feeding roller 114, an intermediate roller 115, a registration roller pair 116, and an image forming unit 120. The paper feed unit 11 includes a pickup roller 112 and a first paper feed roller 113. The sheet feeding unit 11 sends the sheet P to the sheet conveyance path PP. The sheet conveyance path PP is disposed so as to pass from the sheet feeding unit 11 through a transfer nip TP (nip unit) disposed in the image forming unit 120 via the intermediate roller pair 115 and the registration roller pair 116. It is a transport path. The sheet P is conveyed in the conveyance direction from the lower side to the upper side along the sheet conveyance path PP.

  The cassette 110 accommodates the sheet P inside. The cassette 110 can be pulled out from the lower housing 21 in the front direction (the front side in FIG. 2). The sheet P accommodated in the cassette 110 is sent upward in the lower housing 21. Thereafter, the sheet P is subjected to an image forming process in the lower housing 21 based on an instruction input by the user through the operation unit 221, and is discharged to the discharge space 24. The cassette 110 includes a lift plate 111 that supports the sheet P. The lift plate 111 is inclined so as to push up the leading edge of the sheet P upward.

  The pickup roller 112 is disposed on the leading edge of the sheet P pushed upward by the lift plate 111. When the pickup roller 112 rotates, the sheet P is pulled out from the cassette 110.

  The first paper feed roller 113 is disposed downstream of the pickup roller 112 in the sheet conveyance direction. The first paper feed roller 113 sends the sheet P further downstream. The second paper feed roller 114 is disposed inside the manual feed tray 240. The second paper feed roller 114 pulls the sheet P on the manual feed tray 240 into the lower housing 21. The user can selectively use the sheet P stored in the cassette 110 or the sheet P placed on the manual feed tray 240.

  The intermediate roller pair 115 is disposed downstream of the first paper feed roller 113 and the second paper feed roller 114 in the sheet conveyance direction. The intermediate roller pair 115 conveys the sheet P sent out by the first paper feed roller 113 and the second paper feed roller 114 further downstream.

  The registration roller pair 116 defines the position of the sheet in a direction orthogonal to the sheet conveyance direction. Thereby, the position of the image formed on the sheet P is adjusted. The registration roller pair 116 conveys the sheet P to the image forming unit 120 in accordance with the timing at which the toner image is transferred to the sheet P in the image forming unit 120. The registration roller pair 116 has a function of correcting skew (skew) of the sheet P. The registration roller pair 116 includes a driven roller 116A and a registration roller 116B (FIG. 3).

  Referring to FIG. 2, the image forming unit 120 includes a photosensitive drum 121, a charger 122, an exposure device 123, a developing device 124, a toner container 125, a transfer roller 126, a conveyance belt 180, and a cleaning. Device 127.

  The photosensitive drum 121 is disposed to face the sheet conveyance path PP and is driven to rotate about an axis. The photosensitive drum 121 has a cylindrical shape. The photosensitive drum 121 has an electrostatic latent image formed on its peripheral surface and carries a toner image corresponding to the electrostatic latent image.

  The charger 122 is applied with a predetermined voltage and charges the peripheral surface of the photosensitive drum 121 substantially uniformly. The exposure device 123 irradiates the peripheral surface of the photosensitive drum 121 charged by the charger 122 with laser light. The laser light is emitted in accordance with image data output from an external device (not shown) such as a personal computer that is communicably connected to the image forming apparatus 1. As a result, an electrostatic latent image corresponding to the image data is formed on the peripheral surface of the photosensitive drum 121.

  The developing device 124 supplies toner to the peripheral surface of the photosensitive drum 121 on which the electrostatic latent image is formed. The toner container 125 supplies toner to the developing device 124. The toner container 125 supplies toner to the developing device 124 sequentially or as necessary. When the developing device 124 supplies toner to the photosensitive drum 121, the electrostatic latent image formed on the peripheral surface of the photosensitive drum 121 is developed (visualized). As a result, a toner image is formed on the peripheral surface of the photosensitive drum 121. The developing device includes a developing roller 124A (FIG. 3) that carries toner on its peripheral surface. The developing roller 124A is disposed to face the photosensitive drum 121 at the developing position. The developing roller 124 </ b> A is rotated and supplies toner to the photosensitive drum 121.

  The transfer roller 126 is disposed to face the peripheral surface of the photoconductive drum 121. The transfer roller 126 contacts the inner peripheral surface of the conveyance belt 180 and presses the conveyance belt 180 against the photosensitive drum 121. A transfer bias is applied to the transfer roller 126 from a bias application unit (not shown).

  The conveyance belt 180 is disposed to face the photosensitive drum 121 with the sheet conveyance path PP interposed therebetween. The conveyor belt 180 is an endless belt. The conveyor belt 180 is driven to form a transfer nip TP with the photosensitive drum 121. The conveyance belt 180 carries the sheet P on its surface and conveys the sheet P so that the sheet P passes through the transfer nip TP. The conveyor belt 180 transmits a rotational driving force to the transfer roller 126 via the inner peripheral surface. The conveyance belt 180 is stretched by a stretching roller 182 and a driving roller 181 on the upstream side and the downstream side in the sheet conveyance direction from the transfer roller 126. The driving roller 181 receives a rotational driving force from a driving unit (not shown) and rotates the conveyor belt 180. The transfer roller 126 and the stretching roller 182 rotate along with the conveyance belt 180 and rotate at the same speed as the conveyance belt 180. When the sheet P passes through the transfer nip TP, the toner image formed on the peripheral surface of the photosensitive drum 121 is transferred to the sheet P.

  The cleaning device 127 removes the toner remaining on the peripheral surface of the photosensitive drum 121 after the toner image is transferred to the sheet P. The peripheral surface of the photosensitive drum 121 cleaned by the cleaning device 127 passes again below the charger 122 and is uniformly charged. Thereafter, the above-described toner image is newly formed.

  The image forming apparatus 1 further includes a fixing device 130 (FIG. 2) (fixing unit) disposed downstream of the image forming unit 120 (transfer nip TP) in the transport direction. The fixing device 130 performs a fixing process on the sheet P on which the toner image is transferred. The fixing device 130 includes a heating roller 131 that melts the toner on the sheet P, and a pressure roller 132 that causes the sheet P to adhere to the heating roller 131. When the sheet P passes between the heating roller 131 and the pressure roller 132, the toner image is fixed on the sheet P.

  The image forming apparatus 1 further includes an upper conveyance roller pair 133 disposed downstream of the fixing device 130 and a discharge roller pair 134 disposed downstream of the upper conveyance roller pair 133. The sheet P is discharged from the lower housing 21 by the upper conveyance roller pair 133 and the discharge roller pair 134. The sheets P discharged from the lower housing 21 are stacked on the upper wall 210.

  Next, the transfer unit 180M and the transport unit 1M according to the present embodiment will be described with reference to FIGS. 3 to 9 in addition to FIG. FIG. 3 is an enlarged cross-sectional view of a part of the image forming apparatus 1 of FIG. FIG. 3 is an enlarged cross-sectional view of the periphery of the photosensitive drum 121 and the conveyance belt 180. FIG. 4 is a cross-sectional view in which a part of FIG. 3 is further enlarged. In FIG. 4, the photosensitive drum 121 does not appear. FIG. 5 is a perspective view of the transport unit 1M and the transfer unit 180M of the image forming apparatus 1 according to the present embodiment. FIG. 6 is a perspective view of a state where the transfer unit 180M is removed from the transport unit 1M of FIG. FIG. 7 is a perspective view of the transport unit 1M of FIG. 5 with the front standing wall 1MF removed. FIG. 8 is a perspective view of the transfer unit 1M with the transfer unit 180M and the front standing wall 1MF removed. Further, FIG. 9 is an enlarged perspective view of the periphery of the sirocco fan 50 of the transport unit 1M.

  Referring to FIGS. 4 and 5, image forming apparatus 1 includes transfer unit 180M. The transfer unit 180M is a unit in which the transport belt 180, the driving roller 181, the stretching roller 182, and the transfer roller 126 are integrally supported. The transfer unit 180M has a function of transporting the sheet P so that the sheet P passes through the transfer nip TP and transferring the toner image to the sheet P. The transfer unit 180M is mounted on a transport unit 1M described later.

  Referring to FIGS. 4, 7, and 9, transfer unit 180 </ b> M includes guide portion 183. The guide unit 183 extends along the front-rear direction (the axial direction of the photosensitive drum 121) above the drive roller 181 in the transfer unit 180M. The guide unit 183 has a function of guiding the sheet P detached from the transport belt 180 in the transport direction. The guide part 183 includes a guide rib 183G and a notch part 184 (FIG. 7).

  The guide ribs 183G are a plurality of ribs arranged at intervals in the front-rear direction in the guide portion 183. The sheet P is guided toward the fixing device 130 along the guide rib 183G. The notch 184 is a recess formed at the center in the front-rear direction of the guide 183. The notch 184 is formed on the downstream side in the transport direction from the transport belt 180 so as to expose a part of the transport unit 1M described later to the sheet transport path PP side.

  Further, the image forming apparatus 1 includes a transport unit 1M. The transport unit 1M is disposed on the right wall 2R (FIGS. 1 and 2) side of the main housing 2. The transport unit 1M is arranged with a predetermined gap with respect to the transfer unit 180M on the opposite side of the photosensitive drum 121 (right side of the transfer unit 180M) as viewed from the transfer unit 180M. The transport unit 1M is arranged along the front-rear and up-down directions at the right end of the main housing 2. The right wall 2R of the main housing 2 is provided in the transport unit 1M. The transport unit 1M transports the sheet P on which the fixing process has been performed to the sheet transport path PP on the upstream side in the transport direction from the transfer nip TP. The transport unit 1M includes a reverse transport path RP, a first transport roller pair 141, a second transport roller pair 142, a reverse guide unit 145, and a front standing wall 1MF.

  The reverse conveyance path RP is a conveyance path through which the sheet P is conveyed again toward the transfer nip TP. The first transport roller pair 141 and the second transport roller pair 142 are disposed at appropriate positions on the reverse transport path RP and transport the sheet P. As shown in FIGS. 2, 4, and 5, the reverse guide portion 145 is a guide wall that defines the right side portion of the reverse conveyance path RP above the transfer unit 180 </ b> M. Further, as shown in FIG. 5, the front standing wall 1MF is a wall portion erected so as to face leftward in the front portion of the transport unit 1M.

  Referring to FIG. 2, the sheet P that has been subjected to the fixing process in the fixing device 130 is conveyed upward by the upper conveying roller pair 133. At this time, during double-sided printing in which an image is also formed on the back side of the sheet P, the switching guide 135 is rotated to switch the conveyance direction of the sheet P to the right side. As a result, the sheet P is carried into the reverse conveyance path RP by the reverse carry-in roller 136. Referring to FIG. 4, the sheet P conveyed further downward (arrow D <b> 41 in FIG. 4) on the reverse conveyance path RP is moved by the first conveyance roller pair 141 and the second conveyance roller pair 142 to the arrow in FIG. 4. It is further conveyed as shown in D42. Then, in the sheet conveyance path PP, the sheet P is conveyed again into the sheet conveyance path PP in the conveyance junction MP on the upstream side of the transfer nip TP. When the sheet P is conveyed again to the transfer nip TP by the registration roller pair 116 and the conveyance belt 180, the toner image is transferred to the back surface of the sheet P.

  As shown in FIG. 4, the transfer unit 180 </ b> M is supported by the transport unit 1 </ b> M by a tension spring (not shown) in such a posture that the upper end portion is inclined to the right side. Specifically, a pair of tension springs (not shown) disposed at both ends in the front-rear direction of the transfer unit 180M, which are upper ends of the transfer unit 180M, are formed at both ends in the front-rear direction of the transport unit 1M. Is attached to the support portion 146 (FIG. 8). The lower part of the transfer unit 180M is supported by a bracket 1MB (FIG. 8) extending in the front-rear direction in the transport unit 1M. At this time, a gap is formed between the transfer unit 180M and the transport unit 1M, and a later-described cooling air passage AP (FIG. 4) is formed.

  As illustrated in FIG. 4, a driven roller 116 </ b> A that is a roller on the right side of the registration roller pair 116 is rotatably supported by the transport unit 1 </ b> M. When the transfer unit 180M is attached to the transport unit 1M, the stretching roller 182 is disposed above the driven roller 116A.

  The conveyance unit 1M includes a sheet detection sensor 51 (detection sensor), a density detection sensor 52 (detection sensor), and a sirocco fan 50 (air flow generation unit). The sheet detection sensor 51 and the density detection sensor 52 are arranged in the transport unit 1M so as to face the transfer unit 180M in a cross-sectional view intersecting the axial direction of the photosensitive drum 121, and execute a predetermined detection operation.

  The sheet detection sensor 51 is disposed in the transport unit 1M so as to face the notch 184 of the transfer unit 180M. As shown in FIG. 8, the sheet detection sensor 51 is disposed below and to the left of the reversing guide portion 145 and in the central portion in the front-rear direction of the transport unit 1M. The sheet detection sensor 51 detects the leading end portion or the trailing end portion of the sheet P conveyed in the conveying direction from the transfer nip TP through the notch 184. The detection information of the sheet P by the sheet detection sensor 51 is used for adjusting the feeding timing of the subsequent sheet P by the registration roller pair 116.

  3, 4, and 8, the density detection sensor 52 is disposed in the transport unit 1 </ b> M so as to face the transport belt 180 of the transfer unit 180 </ b> M. In FIG. 5, the transfer unit 180 </ b> M is attached to the transport unit 1 </ b> M, and the density detection sensor 52 is disposed on the back side of the transport belt 180, so the density detection sensor 52 does not appear. Further, as shown in FIG. 8, the density detection sensor 52 is disposed below and behind the sheet detection sensor 51. The density detection sensor 52 detects the density of the toner image for density detection that is transferred from the photosensitive drum 121 to the transport belt 180 and formed on the transport belt 180. Therefore, the density of the density detection toner image can be detected using the back side of the conveyance belt 180 with respect to the sheet conveyance path PP. The density information detected by the density sensor 52 is used for adjusting the amount of toner to be replenished to the developing device 124, adjusting the developing bias applied to the developing roller 124A, and the like.

  The sirocco fan 50 is arranged inside the front standing wall 1MF (FIG. 5). That is, with reference to FIG. 7 and FIG. 9, the sirocco fan 50 is disposed at the front end of the transport unit 1M. The sirocco fan 50 causes a cooling air flow to flow between the transfer unit 180M and the transport unit 1M along the axial direction of the photosensitive drum 121 toward the rear. The sirocco fan 50 includes an outlet 50A (FIG. 9). The outlet 50A is opened rearward. The cooling airflow is blown out from the blowout port 50A.

  As described above, a predetermined gap is formed between the transfer unit 180M and the transport unit 1M. The gap functions as a cooling air path AP shown in FIG. In other words, the cooling air passage AP is formed between the transfer unit 180M and the transport unit 1M, and guides the cooling air flow toward the sheet detection sensor 51 and the density detection sensor 52.

  When double-sided printing is performed on the sheet P, the sheet P that has been heated by passing through the fixing device 30 is conveyed through the reverse conveyance path RP, and then again passes through the transfer nip TP. When the sheet P carried out from the transfer nip TP is conveyed along the guide portion 183 of the transfer unit 180M, the heat of the sheet P is transmitted to the sheet detection sensor 51 via the notch portion 184. Alternatively, the heat of the sheet P is transmitted to the back side of the transfer unit 180M via the transport belt 180, and the density detection sensor 52 is warmed. When the temperature of the sheet detection sensor 51 and the density detection sensor 52 rises, the detection accuracy may be lowered, or malfunction of each sensor may be caused. Even in such a case, in the present embodiment, since the sheet detection sensor 51 is cooled by the cooling airflow, the temperature increase of the sheet detection sensor 51 is suppressed. As a result, the sheet detection sensor 51 stably detects that the sheet P has been unloaded from the transfer nip TP. Further, since the concentration detection sensor 52 is cooled by the cooling air flow, the concentration is detected stably. Further, even when the toner of the density detection toner image rises from the conveyance belt 180, the toner is prevented from adhering to the density detection sensor 52 by the cooling air flow.

  On the other hand, when a strong cooling airflow flows from the sirocco fan 50 into the cooling air passage AP, a new airflow is caused around the transfer unit 180M by the cooling airflow. Specifically, as indicated by an arrow AF1 in FIG. 3, an air flow flows into the gap AT (FIG. 4) between the upper end of the transfer unit 180M and the transport unit 1M while passing from the transfer nip TP to above the transfer unit 180M. Becomes easier to flow in. In the transfer nip TP, toner may be scattered when the toner image on the photosensitive drum 121 is transferred onto the sheet P by discharge. As shown in FIG. 3, in the present embodiment, a cleaning device 127 that collects toner from the photosensitive drum 121 is disposed above the transfer nip TP. Accordingly, when the air flow indicated by the arrow AF1 in FIG. 4 includes scattered toner, the toner flowing in from the gap AT adheres to the sheet detection sensor 51 and the density detection sensor 52. As a result, malfunctions of the sheet detection sensor 51 and the density detection sensor 52 may occur.

  In the present embodiment, a shielding sponge 60 (shielding member) is disposed in order to solve the above problems. The shielding sponge 60 is interposed in the gap between the transfer unit 180M and the transport unit 1M along the axial direction (sheet width direction) of the photosensitive drum 121, and intersects the axial direction from the periphery of the transfer unit 180M. The airflow flowing toward the cooling air passage AP along the direction is shielded. In the present embodiment, the shielding sponge 60 is a sponge material (elastic member) that is compressed between the transfer unit 180M and the transport unit 1M.

  Referring to FIG. 6, a pair of shielding sponges 60 are arranged on transport unit 1 </ b> M so as to sandwich sheet detection sensor 51. The shielding sponge 60 is a prismatic sponge material extending in the front-rear direction. When the transfer unit 180M is mounted on the transport unit 1M, as shown in FIG. 4, the shielding sponge 60 is interposed between the guide portion 183 of the transfer unit 180M and the transport unit 1M in a compressed state.

  As a result, the gap located above the density detection sensor 52 and in front of and behind the sheet detection sensor 51 is sealed, and the flow of air from the periphery of the transfer unit 180M to the cooling air path AP is suppressed. Further, since the upper part of the cooling air passage AP is defined by the shielding sponge 60, the cooling air flow blown out from the blowout port 50A is linearly guided toward the rear. As a result, the sheet detection sensor 51 and the density detection sensor 52 are stably cooled by the cooling air flow, and foreign substances such as toner are prevented from adhering to the sheet detection sensor 51 and the density detection sensor 52. The shielding sponge 60 is disposed between the transfer unit 180M and the transport unit 1M in a compressed manner, thereby further preventing the air flow from flowing into the cooling air path AP from the periphery of the transfer unit 180M. Further, according to the above configuration, the notch portion 184 can be formed by using the guide portion 183 that guides the sheet P detached from the conveyance belt 180, and the guide portion 183, the conveyance unit 1M, A shielding sponge 60 can be interposed between the two.

  10 and 11 are a perspective view and a side view showing the flow of the cooling air flow in the cooling air passage AP between the transfer unit 180M and the transport unit 1M. FIG. 12 is a perspective view showing a state where the first diverter 70 is attached to the transport unit 1M according to the present embodiment. 13A is a perspective view, FIG. 13B is a side view, and FIG. 13C is a developed view of the first flow dividing portion 70 according to the present embodiment.

  In the present embodiment, a reversing guide portion 145 is disposed along the vertical direction on the right side of the shielding sponge 60. Therefore, by arranging the shielding sponge 60 between the transfer unit 180M and the transport unit 1M, it is possible to prevent the air flow (arrow AF2 in FIG. 10) generated in the sheet transport path PP from flowing into the cooling air path AP. Is done.

  In the present embodiment, the transport unit 1M further includes a partition wall member 61, a left wall 62, an air path lower wall 63, and an upstream recess 64 (FIG. 10). The left wall portion 62 is a wall portion facing leftward below the shielding sponge 60 in the transport unit 1M. The air path lower wall 63 is a wall portion protruding from the lower portion of the left wall portion 62 toward the left. The air path lower wall 63 defines a lower part of the cooling air path AP along the axial direction of the photosensitive drum 121. Referring to FIG. 12, the air path lower wall 63 includes an upper surface portion 63A. The upper surface portion 63A is an upper surface portion of the air passage lower wall 63, and is composed of an inclined surface that is inclined downward as it proceeds from right to left. The upstream concave portion 64 is a concave portion formed by partially denting the front end of the air passage lower wall 63 to the right. The upstream recessed portion 64 is formed on the upstream side of the flow of the cooling airflow flowing into the cooling air passage AP in the air passage lower wall 63. Further, the upstream recessed portion 64 forms a part of a communication air passage AP3 described later and communicates with a first opening 703 described later.

  The partition member 61 is a plate-like member protruding from the left wall 62 of the transport unit 1M along the axial direction of the photosensitive drum 121. The partition member 61 is extended in the front-rear direction with a predetermined height in the left-right direction. The partition member 61 defines a part of the cooling air passage AP. For this reason, the partition member 61 promotes the flow of the cooling airflow in the axial direction.

  As described above, the sheet detection sensor 51 and the density detection sensor 52 are arranged at different positions in the sheet conveyance direction (vertical direction). The partition wall member 61 is disposed between the sheet detection sensor 51 and the density detection sensor 52 in the vertical direction. For this reason, as shown in FIGS. 10 and 11, the cooling air flow that has flowed into the cooling air passage AP from the outlet 50A of the sirocco fan 50 is separated from the first cooling air flow AP1 on the upper side by the partition wall member 61. It is divided into the second cooling air flow AP2 on the lower side. The first cooling air flow AP <b> 1 is guided to the sheet detection sensor 51. Further, the second cooling air flow AP <b> 2 is guided to the concentration detection sensor 52. As a result, the cooling airflow can be guided toward the plurality of detection sensors. Therefore, the sheet detection sensor 51 and the density detection sensor 52 are stably cooled.

  Furthermore, in the present embodiment, the partition wall member 61 has a function of positioning the electrical wiring extended from the sheet detection sensor 51 and the density detection sensor 52. In other words, electrical wires extending from the sheet detection sensor 51 and the density detection sensor 52 and routed to an electrical board (not shown) of the transport unit 1M are arranged along the partition wall member 61. Therefore, the electrical wiring of the sheet detection sensor 51 and the density detection sensor 52 can be positioned using the partition wall member 61 that guides the cooling air flow.

  On the other hand, referring to FIG. 3 and FIG. 10, when a strong cooling air flow flows from the sirocco fan 50 to the cooling air passage AP as described above, the air around the transfer unit 180M is transferred to the transfer unit 180M and the transport unit. It is drawn between 1M. Referring to FIGS. 3 and 10, on the upstream side of the sheet detection sensor 51 and the density detection sensor 52 in the flow path of the cooling air flow, a gap between the transfer unit 180M and the transport unit 1M is interposed. A space that connects the periphery of the transfer unit 180M and the cooling air passage AP is defined as a communication air passage AF3. The communication air path A3 connects the periphery of the transfer unit 180M and the cooling air path AP along a direction intersecting the axial direction of the photosensitive drum 121. When toner is scattered around the transfer unit 180M, the toner adheres to the sheet detection sensor 51 and the density detection sensor 52. As a result, malfunctions of the sheet detection sensor 51 and the density detection sensor 52 may occur.

  Further, when the cooling airflow is introduced into the cooling air passage AP from the outlet 50A (FIG. 9) of the sirocco fan 50, the airflow is generated from the periphery of the transfer unit 180M via the upstream concave portion 64 in FIG. It may flow into the cooling air passage AP. In this case, the air flow prevents the cooling air flow from flowing into the cooling air passage AP. As a result, the cooling effect of the sheet detection sensor 51 and the density detection sensor 52 is reduced.

  In order to solve such a problem on the upstream side of the cooling air passage AP, in this embodiment, the transport unit 1M includes the first flow dividing section 70 (FIGS. 12 and 13) (a flow dividing mechanism). The first diversion unit 70 has a function of causing a part of the cooling air flow that has flowed from the sirocco fan 50 into the cooling air passage AP to flow into the communication air passage AP3.

  Referring to FIGS. 13A to 13C, the first flow dividing portion 70 includes a first fixed surface 701 (fixed surface), a first shielding surface 702 (shielding surface), and a first opening 703 (opening). Part) and a first partition wall surface 704 (partition wall surface). FIG. 13B is a side view of FIG. 13A viewed from the direction of arrow D131 (left side of FIG. 12). In the present embodiment, as shown in FIG. 13C, the first flow dividing portion 70 is formed of a single sheet member having a rectangular shape. The first fixing surface 701 and the first partition wall surface 704 are formed by bending the sheet member at a substantially central portion in the short side direction. In addition, the first shielding surface 702 and the first opening 703 are formed by cutting a part of the first fixing surface 701 at the center of the first fixing surface 701 in the long side direction.

  The first fixing surface 701 is fixed to the upper surface portion 63A of the air passage lower wall 63 so as to cover the upper side of the upstream concave portion 64 (FIG. 12).

  The first opening 703 is opened in a first fixed surface 701 that defines a part of the cooling air passage AP, and connects the cooling air passage AP and the communication air passage AF3. The first shielding surface 702 is disposed on the downstream side of the first opening 703 in the flow path of the cooling air flow, and shields a part of the cooling air flow.

  In other words, the first fixed surface 701, the first shielding surface 702, and the first opening 703 are formed in a rectangular shape on the first fixed surface 701, and the flow path of the cooling airflow An edge is provided on the downstream side. The first shielding surface 702 extends from the edge toward the inside of the cooling air passage AP. Then, the angle of the first shielding surface 702 with respect to the first opening 703 can be adjusted by rotating the first shielding surface 702 with the edge as a fulcrum (arrow D134 in FIG. 13B). Yes.

  The first partition wall surface 704 is connected to the first fixed surface 701 so as to intersect the first fixed surface 701. When the first fixing surface 701 is fixed to the upper surface portion 63A, the first partition wall surface 704 is disposed to face the transfer unit 180M, and a part of the cooling air passage AP is formed along the axial direction of the photosensitive drum 121. Define. The first partition wall 704 can stably guide the cooling airflow that has flowed into the cooling air passage AP toward the sheet detection sensor 51 and the concentration detection sensor 52 in the axial direction.

  As indicated by an arrow D132 in FIG. 13B, a part of the cooling air flow flowing in from the outlet 50A of the sirocco fan 50 is shielded and retained by the first shielding surface 702, and then passes through the first opening 703. It flows into the communication air passage AF3 (arrow D133 in FIG. 13B). As described above, in the present embodiment, the first diverter 70 causes a part of the cooling air flow that has flowed from the sirocco fan 50 to the cooling air passage AP to flow into the communication air passage AF3. For this reason, an air flow is formed in the communication air passage AF3 from the cooling air passage AP toward the periphery of the transfer unit 180M (arrow AP3 in FIG. 12). As a result, the flow of air from the periphery of the transfer unit 180M to the cooling air path AP is suppressed. That is, a part of the cooling air flow is used, and the first opening 703 is sealed. For this reason, the sheet detection sensor 51 and the density detection sensor 52 are stably cooled by the cooling air flow, and foreign substances such as toner are prevented from adhering to the sensors. As described above, by adjusting the angle of the first shielding surface 702 with respect to the first opening 703, it is possible to adjust the amount of air flowing into the communication air passage AF3 in the cooling air flow. Accordingly, the air volume for cooling the sheet detection sensor 51 and the density detection sensor 52 and the air volume for closing the communication air path AF3 can be appropriately set according to the air path shape of the communication air path AF3.

  The image forming apparatus according to the embodiment of the present invention has been described above. However, the present invention is not limited to this, and for example, the following modified embodiment can be taken.

  (1) In the above embodiment, the sponge member is used as the shielding member interposed between the transfer unit 180M and the transport unit 1M. However, the present invention is not limited to this. The shielding member may be a film member that extends from one of the transfer unit 180M and the conveyance unit 1M toward the other and is disposed along the sheet width direction.

  (2) Further, in the above-described embodiment, the conveyance unit 1M has been described as including the sheet detection sensor 51 and the density detection sensor 52, but the present invention is not limited to this. The transport unit 1M may include other detection sensors. Further, another detection sensor may be arranged on the transfer unit 180M side so as to face the transport unit 1M.

  (3) Furthermore, in the above embodiment, the first diverter 70 is used as the diversion mechanism, but the present invention is not limited to this. FIG. 14 is a perspective view of the second flow dividing portion 71 (a flow dividing mechanism) according to the present modified embodiment. The second diversion part 71 includes a sheet part 710 (sheet member) and a shielding block 712 (elastic member). The sheet portion 710 includes a second fixed surface 711 (fixed surface), a second opening 713 (opening), and a second partition wall 714 (partition wall). The second fixed surface 711 and the second partition surface 714 correspond to the first fixed surface 701 and the first partition surface 704 of the previous embodiment. The second opening 713 is a rectangular opening that is opened in the second fixed surface 711. The shielding block 712 is attached to the second fixing surface 711 on the downstream side of the second opening 713. The shielding block 712 is a sponge member having a rectangular parallelepiped shape. The shielding block 712 includes a second shielding surface 712A. The second shielding surface 712A has the same function as the first shielding surface 702 of the previous embodiment.

  Even in such a configuration, a part of the cooling airflow flowing in from the sirocco fan 50 is shielded by the second shielding surface 712A of the shielding block 712, so that the airflow easily flows into the second opening 713. . Therefore, by attaching the shielding block 712 to the second fixed surface 711 of the seat portion 710, a part of the cooling airflow can be caused to flow into the communication air path AF3.

  (4) In the embodiment described above, the first diverting portion 70 is fixed to the upper surface portion 63A of the air passage lower wall 63, but the present invention is not limited to this. The first diverter 70 or the second diverter 71 slides in the axial direction of the photosensitive drum 121 so that the opening area communicating with the upstream recess 64 of the first opening 703 or the second opening 713 changes. It may be possible. In this case, the air volume of the cooling airflow flowing into the communication air path AF3 from the first opening 703 or the second opening 713 is adjusted by sliding the first diversion part 70 or the second diversion part 71. be able to. Accordingly, the air volume for cooling the sheet detection sensor 51 and the density detection sensor 52 and the air volume for closing the communication air path AF3 can be appropriately set according to the air path shape of the communication air path AF3.

  (5) Moreover, in said embodiment, although the length by which the 1st shielding surface 702 is extended from the 1st fixing surface 701 was demonstrated, this invention is limited to this. is not. The length of the first shielding surface 702 is adjusted according to the air path shape of the communication air path AF3, so that the air volume for cooling the sheet detection sensor 51 and the density detection sensor 52 and the communication air path AF3 are blocked. The air volume may be set appropriately.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 1M Conveyance unit 1MB Bracket 1MF Front standing wall 2 Main housing 2R Right wall 50 Sirocco fan (air flow generation part)
50A Air outlet 51 Sheet detection sensor (detection sensor)
52 Concentration detection sensor (detection sensor)
60 Shielding sponge 61 Bulkhead member 62 Left wall 63 Lower wall of air passage (wall)
63A Top surface 64 Upstream recess (recess)
70 1st diversion part (diversion mechanism)
71 2nd diversion part (diversion mechanism)
116 Registration roller pair 121 Photoconductor drum 122 Charger 124 Developing device 127 Cleaning device 130 Fixing device (fixing unit)
141 First Conveying Roller Pair 142 Second Conveying Roller Pair 145 Reversing Guide Unit 146 Supporting Unit 180 Conveying Belt 180M Transfer Unit 181 Driving Roller 182 Stretching Roller 183 Guide Unit 183G Guide Rib 184 Notch 701 First Fixed Surface (Fixed Surface)
702 First shielding surface (shielding surface)
703 1st opening part (opening part)
704 First partition wall (partition wall)
710 Sheet part (sheet member)
711 Second fixed surface (fixed surface)
712 Shielding block (elastic member)
712A Second shielding surface (shielding surface)
713 Second opening (opening)
714 Second partition wall (partition wall)
AP Cooling air path P Sheet PP Sheet transport path RP Reverse transport path MP Transport junction

Claims (9)

A sheet conveyance path through which the sheet is conveyed in a predetermined conveyance direction;
A photoconductive drum disposed opposite to the sheet conveying path, driven to rotate about an axis, and carrying a toner image on a peripheral surface;
A conveyance belt is disposed opposite to the photosensitive drum across the sheet conveyance path, is driven to rotate, and forms a nip portion with the photosensitive drum, so that the sheet passes through the nip portion. A transfer unit for transporting the sheet to transfer the toner image onto the sheet;
A fixing unit that is disposed downstream of the nip portion in the transport direction and performs a fixing process on the sheet on which the toner image has been transferred;
On the opposite side of the photosensitive drum as viewed from the transfer unit, the sheet, which is disposed with a predetermined gap with respect to the transfer unit and has undergone the fixing process, is disposed upstream of the nip portion in the transport direction. A conveyance unit for carrying in the sheet conveyance path on the side;
A detection sensor that is disposed in the transport unit so as to face the transfer unit in a cross-sectional view that intersects the axial direction of the photosensitive drum, and performs a predetermined detection operation;
An air flow generating section for introducing a cooling air flow between the transfer unit and the transport unit along the axial direction;
A cooling air passage formed between the transfer unit and the transport unit and guiding the cooling air flow toward the detection sensor;
On the upstream side of the detection sensor in the flow path of the cooling air flow, the periphery of the transfer unit and the cooling air path are connected to the shaft through the gap between the transfer unit and the transport unit. A communication air passage that communicates along a direction intersecting the direction;
A flow dividing mechanism for causing a part of the cooling airflow flowing into the cooling air passage from the air flow generating portion to flow into the communication air passage;
I have a,
The diversion mechanism is
An opening that is open to the cooling air passage and connects the cooling air passage and the communication air passage;
A shielding surface that is disposed downstream of the opening in the flow path of the cooling air flow and shields a part of the cooling air flow;
An image forming apparatus comprising: a. The opening is formed in a rectangular shape, and has an edge on the downstream side of the flow path of the cooling air flow,
The shielding surface extends from the edge toward the inside of the cooling air passage, and the angle of the shielding surface with respect to the opening can be adjusted by rotating the shielding surface with the edge as a fulcrum. The image forming apparatus according to claim 1 , wherein the image forming apparatus is an image forming apparatus. The transport unit includes a wall portion that defines a part of the cooling air passage along the axial direction,
The wall portion includes a recess that forms part of the communication air passage and communicates with the opening.
The diversion mechanism is
A fixing surface fixed to the wall so as to cover the recess,
The opening and the shielding surface formed by cutting a part of the fixed surface;
The image forming apparatus according to claim 2 , further comprising: The image forming apparatus according to claim 1 , further comprising an elastic member that is disposed downstream of the opening in the flow path of the cooling air flow and includes the shielding surface. The transport unit includes a wall portion that defines a part of the cooling air passage along the axial direction,
The wall portion includes a recess that forms part of the communication air passage and communicates with the opening.
The diversion mechanism includes a sheet member including a fixed surface fixed to the wall portion so as to cover the concave portion, and the opening portion opened to the fixed surface,
The image forming apparatus according to claim 4 , wherein the elastic member is attached to the fixed surface on the downstream side of the opening. The diversion mechanism includes a partition wall surface that is continuous with the fixed surface so as to intersect the fixed surface, is disposed to face the transfer unit, and defines a part of the cooling air passage along the axial direction. the image forming apparatus according to claim 3 or 5, characterized in that it comprises. The diverter mechanism, as opening area is changed in communication with the recess of the opening, an image forming apparatus according to claim 3 or 5, characterized in that it is slidable in the axial direction. The transfer unit includes a notch formed so as to expose a part of the transport unit to the sheet transport path side downstream of the transport belt in the transport direction.
The detection sensor is a sheet sensor that is disposed in the conveyance unit so as to face the notch portion, and detects the sheet conveyed from the nip portion via the notch portion. Item 2. The image forming apparatus according to Item 1 . 2. The density sensor according to claim 1 , wherein the detection sensor is a density sensor that is disposed in the conveyance unit so as to face the conveyance belt and detects a density of a detection toner image formed on the conveyance belt. Image forming apparatus.