Image forming device

Abstract

The image forming device has a processing unit, which is removed from the device body after rotating upward, and the processing unit has a photosensitive drum (47), a developing device (51), a guide component (81) and a sealing component (91). The photosensitive drum (47) rotates in a specified rotation direction; the developing device (51) faces the surface of the photosensitive drum (47); the guiding component (81) contacts the upper surface of the sheet to guide the sheet; the sealing component (91) is supported between the developing device (51) and the guiding component (81) in a rotatable manner, and the sealing component (91) opens the gap between the developing device (51) and the guiding component (81) when the processing unit is installed on the device body, and when the processing unit rotates upward, it rotates by its own weight to close the gap between the developing device (51) and the guiding component (81).

Description

Technical Field

[0001] The present invention relates to an image forming apparatus including a guide member for guiding a sheet from a photosensitive drum to a transfer nip. Background Art

[0002] In an image forming apparatus of an electrophotographic method, a development nip is formed between a developing roller of a developing device and a photosensitive drum, and a transfer nip is formed between a transfer roller and a photosensitive drum. The electrostatic latent image formed on the photosensitive drum is developed into a toner image in the development nip, and the developed toner image is transferred from the photosensitive drum to a sheet in the transfer nip. The sheet is conveyed in a predetermined conveying direction and guided to the transfer nip by a guide member. In the conveying direction of the sheet, the developer (toner) scattered from the developing device is easily accumulated in the conveying path or near the conveying path on the upstream side of the transfer nip.

[0003] Therefore, in order to prevent the toner from intruding between the developing device and the guide member, the gap between the guide member and the developing device is sometimes blocked with a sealing member such as a sponge.

[0004] On the other hand, in an image forming apparatus, a processing unit formed of a developing device and a photosensitive drum unit is sometimes supported on the apparatus body in a detachable manner. The processing unit is rotated upward around a rotation axis in the horizontal direction and then pulled out in a direction perpendicular to the rotation axis, thereby removing the processing unit from the apparatus body. The sealing member also has a function of preventing toner accumulated on the upper surface of the guide member from falling when the processing unit is rotated.

[0005] In the case of a sealing member, when the tip of the sheet guided along the guide member contacts the photosensitive drum, a space is formed which is sealed by the developing device, the sealing member, the guide member, the sheet and the photosensitive drum. When the sheet moves with the rotation of the photosensitive drum, there is a problem that the volume of the space changes by the amount of sheet movement and airflow is generated in the space, thereby shifting the position of the toner image formed on the photosensitive drum and generating image defects such as horizontal stripes.

[0006] Therefore, the guide member described in Patent Document 1 has a rib at the tip portion, and a gap is formed between the sheet being conveyed and the tip portion via the rib. This can reduce the change in the space volume when the sheet moves with the rotation of the photosensitive drum.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Publication No. 2017-198818 Summary of the invention

[0010] However, in the guide member described in the above-mentioned Patent Document 1, since there is a gap between the guide member and the sheet, an airflow may sometimes be generated to flow toward the conveying path through the gap. Therefore, there is a problem that the scattered toner flows into the conveying path along with the airflow. Thus, in the case where the problem when the sealing member is provided is not sufficiently eliminated, it is preferable not to provide the sealing member so as not to form the closed space. However, when the sealing member is not provided, there is a problem that the toner accumulated on the upper surface of the guide member falls when the processing unit is rotated.

[0011] The present invention has been made in consideration of the above circumstances, and an object thereof is to provide an image forming apparatus capable of suppressing airflow generated when a sheet enters a transfer nip and preventing toner from falling when a process unit rotates.

[0012] In order to solve the above technical problems, the image forming device of the present invention has a processing unit, which is configured to be removed from the device body after rotating upward around a rotating shaft, and is characterized in that the processing unit has a photosensitive drum, a developing device, a guide component and a sealing component, wherein the photosensitive drum rotates along a specified rotation direction; the developing device faces the surface of the photosensitive drum to form a developing clamping portion; the guiding component contacts the upper surface of the sheet to guide the sheet to a position downstream of the developing clamping portion in the rotation direction; the sealing component is rotatably supported between the developing device and the guiding component, and the sealing component opens a gap between the developing device and the guiding component when the processing unit is installed on the device body, and when the processing unit is removed from the device body and rotated upward, the sealing component rotates in a manner to close the gap between the developing device and the guiding component.

[0013] Effects of the Invention

[0014] According to the present invention, along with the rotation of the processing unit, the sealing component rotates between a posture of opening the gap between the guide component and the developing device and a posture of blocking the colorant accumulated on the guide component, thereby suppressing the airflow generated when the sheet is conveyed to the transfer clamping part and preventing the colorant accumulated on the guide component from falling. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a side view schematically showing the internal structure of the image forming apparatus according to one embodiment of the present invention.

[0016] Figure 2 It is a perspective view showing a sealing member of the image forming apparatus according to one embodiment of the present invention.

[0017] Figure 3 This is a side view showing a sealing member when a process unit is installed in the image forming apparatus according to the embodiment of the present invention.

[0018] Figure 4 It is a perspective view showing an end portion of a sealing member attached to a developing device in an image forming apparatus according to an embodiment of the present invention.

[0019] Figure 5A It is a side view schematically showing a state in which the top cover is opened in the image forming apparatus according to the embodiment of the present invention.

[0020] Figure 5B It is a side view schematically showing a state in which a front cover is opened and a process unit is rotated in the image forming apparatus according to an embodiment of the present invention.

[0021] Figure 5C It is a side view schematically showing a state in which a process unit is pulled out from the apparatus main body in the image forming apparatus according to one embodiment of the present invention.

[0022] Figure 6 This is a side view showing a sealing member when a process unit rotates in the image forming apparatus according to the embodiment of the present invention.

[0023] Figure 7 It is a side view explaining a state where a sheet abuts against a photosensitive drum as a comparative example. DETAILED DESCRIPTION

[0024] Next, refer to the attached Figure 1 The image forming apparatus of the present invention will be described.

[0025] First, use Figure 1 The overall structure of the image forming apparatus will be described. Figure 1 FIG. 1 is a side view schematically showing the internal structure of the image forming apparatus. Figure 1 The left side of the paper in the figure is the front side (front side) of the image forming apparatus. Fr, Rr, L, and R shown in each figure represent the front side, rear side, left side, and right side of the image forming apparatus.

[0026] The image forming apparatus 1 includes an apparatus body 3 having a substantially rectangular hollow portion. A vertical rear wall 5 and a discharge tray 7 are formed on the top plate of the apparatus body 3. The discharge tray 7 is inclined upward from the lower end of the rear wall 5 toward the front. In addition, an opening is formed on the top plate in front of the discharge tray 7. The opening is opened and closed by an upper cover 9. When the upper cover 9 is opened, the hollow portion of the apparatus body 3 is exposed through the opening. A discharge port 11 for sheets is formed on the upper portion of the rear wall 5.

[0027] A manual paper feed port 13 is formed at the lower part of the front plate of the device body 3. In addition, a manual tray 15 is supported on the front plate of the device body 3 so as to be rotatable around a fulcrum below the manual paper feed port 13. In addition, an opening is formed on the front plate at a position above the manual paper feed port 13. The opening is opened and closed by a front cover 17. When the front cover 17 is opened, the hollow part of the device body 3 is exposed through the opening.

[0028] The hollow portion of the apparatus body 3 accommodates a paper feed cassette 21, a paper feed unit 23, an image forming unit 25, and a fixing device 27. The apparatus body 3 also includes a main conveying path 29 for conveying sheets, a reversing path 31, and a manual paper feeding path 33.

[0029] The paper feed cassette 21 is housed in the lower part of the hollow portion and can be removed in the front-to-back direction through an opening formed in the front plate of the apparatus body 3. The paper feed cassette 21 has a loading plate 37 and a retard roller 39 for loading the sheet S. The loading plate 37 is supported on the bottom plate of the paper feed cassette 21 so as to be rotatable in the up-down direction around the rear end portion. The retard roller 39 is arranged in front of the loading plate 37.

[0030] The paper feeding section 23 includes a pickup roller 41 disposed above the front end of the paper feeding cassette 21 and a feed roller 43 disposed in front of the pickup roller 41. The pickup roller 41 rotates in contact with the sheet S placed on the placement plate 37 that has rotated upward, and feeds the sheet S forward. The feed roller 43 contacts the retard roller 39, and a separation nip is formed therebetween.

[0031] The image forming unit 25 is arranged above the paper feed cassette 21 and includes a photosensitive drum 47, a charger 49, a developing device 51, a transfer roller 53, a cleaning device 55, and an exposure device 57. Figure 1 The charger 49, the developing device 51, the transfer roller 53 and the cleaning device 55 are arranged in this order around the photosensitive drum 47 along the rotation direction of the photosensitive drum 47. In this example, the charger 49 is arranged above the photosensitive drum 47, the developing device 51 is arranged in front, the transfer roller 53 is arranged below, and the cleaning device 55 is arranged at the rear.

[0032] The developing device 51 includes a developing housing 61, two stirring members 63, and a developing roller 65. The two stirring members 63 are housed in the developing housing 61 and are used to stir the developer. The developing roller 65 is arranged to face the photosensitive drum 47 through the opening of the developing housing 61, and a developing nip is formed between the developing roller 65 and the photosensitive drum 47. In the developing nip, the toner moves from the developing roller 65 to the photosensitive drum 47. The toner container 67 is connected to the developing housing 61 in a detachable manner.

[0033] The transfer roller 53 faces the photosensitive drum 47 from below, and a transfer nip is formed between the photosensitive drum 47 and the transfer roller 53 .

[0034] The fixing device 27 is arranged behind the image forming section 25 and includes a fixing roller and a pressure roller.

[0035] The main conveying path 29 is formed so as to bend upward from the separation nip portion, extend substantially horizontally rearward in a manner passing through the transfer nip portion and the fixing device 27, and bend upward from the fixing device 27 to the discharge port 11. The direction along the main conveying path 29 is assumed to be the conveying direction of the sheet S, and the upstream side and the downstream side in the following description refer to the upstream side and the downstream side in the conveying direction of the sheet S. The reversing path 31 branches off from the main conveying path 29 on the downstream side of the fixing device 27, and merges with the main conveying path 29 on the downstream side of the separation nip portion. The manual paper feeding path 33 starts from the manual paper feeding port 13 and merges with the main conveying path 29 on the downstream side of the separation nip portion.

[0036] The main conveying path 29 has an intermediate roller pair 71, a resistance roller pair 73, a switchback part 75, and a discharge roller pair 77 in order from the upstream side. The intermediate roller pair 71 is arranged on the downstream side of the confluence of the reversing path 31 and the manual paper feeding path 33 with the main conveying path 29. The resistance roller pair 73 is arranged between the intermediate roller pair 71 and the transfer nip. The switchback part 75 is arranged on the downstream side of the fixing device 27. The discharge roller pair 77 is arranged on the inner side of the discharge port 11.

[0037] The main conveying path 29 from the resist roller pair 73 to the transfer nip is formed below the developing device 51 and generally horizontally from the front to the rear between the upper guide member 81 and the lower guide member 83. The upper guide member 81 is supported by the developing housing 61 of the developing device 51, and the lower guide member 83 is supported by the device body 3.

[0038] The upper guide member 81 has a width corresponding to the maximum sheet width and a predetermined length extending in the conveying direction. The lower surface of the upper guide member 81 is flat and is curved in an upward arc shape in the conveying direction.

[0039] The photosensitive drum 47, the charger 49, the developing device 51, the cleaning device 55, the toner container 67 and the upper guide member 81 are unitized into a processing unit P. As described above, the charger 49 is arranged above the photosensitive drum 47, the developing device 51 and the upper guide member 81 are arranged in front, and the cleaning device 55 is arranged in the rear. The end of the cleaning device 55 side of the processing unit P is supported in a manner that can rotate around the rotating shaft 87 extending in the horizontal direction, and accordingly, the processing unit P is positioned at a predetermined position relative to the device body 3. That is, when the processing unit P is installed in a predetermined position, the photosensitive drum 47 and the transfer roller 53 face each other to form a transfer nip, and the upper guide member 81 and the lower guide member 83 face each other to form a main conveying path. The removal and assembly of the processing unit P will be described later.

[0040] A sealing member 91 is provided in a gap G between the developing device 51 and the upper guide member 81. Figure 2 to Figure 4 The sealing member 91 will be described. Figure 2 is a perspective view showing a sealing component, Figure 3 is a side view showing a sealing member installed in a developing device, Figure 4 It is a perspective view showing an end portion of a sealing member attached to a developing device.

[0041] like Figure 2 As shown, the sealing member 91 includes: a shaft member 93; a plate 95 which is supported by the shaft member 93 in a cantilever manner; hammers 99 which are respectively provided at both left and right ends of the shaft member 93; and bosses 97 which protrude from the outer sides of each hammer 99.

[0042] The shaft member 93 is an elongated member having a rectangular cross section and having a length longer than the maximum width of the sheet S. On the rear surface of the shaft member 93, a plurality of fixing pieces 93a having the same thickness as the shaft member 93 protrude at predetermined intervals in the left-right direction. The plate 95 has a rectangular shape that is long in the left-right direction and is formed of a flexible material. The front end of the plate 95 is fixed to the shaft member 93 and the lower surface of the fixing piece 93a by bonding or the like.

[0043] The two weights 99 each have a rectangular parallelepiped shape that is long in the vertical direction and are formed of a material such as resin. The left and right end surfaces of the shaft member 93 are fixed to the upper portion of the inner surface of the weight 99, and the weight 99 extends downward from the shaft member 93. The boss 97 is protrudingly provided on the upper portion of the outer surface of each weight 99.

[0044] like Figure 3 As shown, the sealing member 91 is arranged at a position as close to the photosensitive drum 47 as possible, with the plate 95 extending forward on the opposite side of the photosensitive drum 47. Figure 2) is rotatably supported by a shaft support portion 61a formed on the lower surface of the developing housing 61 (see Figure 4 ). In addition, the left and right weights 99 are housed in the notches 81a formed in the upper guide member 81 (see Figure 4 )Inside.

[0045] The plate 95 of the sealing member 91 is supported by the weight portion 99 in a substantially horizontal posture. Figure 3 The counterclockwise rotation force and the hammer 99 cause the shaft member 93 to Figure 3 The weight of the weight portion 99 is set so that the plate 95 becomes substantially horizontal at the position where the force of the clockwise rotation is balanced. The posture of the sealing member 91 is referred to as the balanced posture.

[0046] When the sealing member 91 is supported in a balanced posture, the tip of the plate 95 moves upward away from the upper guide member 81. That is, when the process unit P is mounted on the apparatus body 3, a gap G is provided between the developing housing 61 of the developing device 51 and the upper guide member 81.

[0047] Next, the image forming operation is described. First, the charger 49 charges the photosensitive drum 47, and the exposure device 57 exposes the photosensitive drum 47 according to the image data. Accordingly, an electrostatic latent image is formed on the photosensitive drum 47. The developing device 51 develops the electrostatic latent image on the toner image. On the other hand, the sheet S placed on the placing plate 37 of the paper feed cassette 21 is supplied by the pickup roller 41, and the sheet S is separated in the separation nip and then conveyed to the main conveying path 29. Thereafter, the sheet S is conveyed by the intermediate roller pair 71, and after the conveying time is adjusted by the resistance roller pair 73, it is conveyed to the transfer nip.

[0048] The sheet S passing through the resist roller pair 73 is conveyed with its upper surface along the lower surface of the upper guide member 81, and is guided from the upper guide member 81 toward the photosensitive drum 47 along the curved direction of the lower surface of the upper guide member 81. At this time, the leading end of the sheet S contacts the surface of the photosensitive drum 47 from the upstream side in the rotation direction of the photosensitive drum 47, and enters the transfer nip portion as the photosensitive drum 47 rotates.

[0049] In the transfer nip, the toner image formed on the photosensitive drum 47 is transferred to the sheet S. After that, the sheet S is conveyed to the fixing device 27. The fixing device 27 fixes the toner image on the sheet. The sheet with the toner image fixed is conveyed along the main conveying path 29 to the discharge port 11, and is discharged from the discharge port 11 by the discharge roller pair 77 and placed on the discharge tray 7. After the toner image is transferred to the sheet, the toner remaining on the photosensitive drum 47 is removed by the cleaning device 55.

[0050] Next, refer to Figure 5A to Figure 5C and Figure 6 An example of a method of disassembling the processing unit P will be described. Figure 5A to Figure 5C It is a side view schematically showing the image forming apparatus in a state where the process unit is rotated. Figure 6 It is a side view showing the sealing member when the process unit is rotating.

[0051] When the processing unit P is removed from the device body 3, as shown in FIG. Figure 5A As shown in FIG. 1 , the upper cover 9 is opened to open the hollow portion of the device body 3. Then, the toner container 67 (see FIG. 1 ) is placed in the Figure 1 ) is removed from the developing device 51 and pulled out through the opening of the top plate of the device body 3. Figure 6 As shown in FIG. 2B , the front cover 17 is opened, and the processing unit P is rotated upward around the rotation axis 87. The rotation angle is, for example, 11 degrees.

[0052] With the rotation of the processing unit P, Figure 6 As shown, the sealing member 91 is oriented relative to the developing device 51 by its own weight. Figure 6 The top end of the plate 95 is slightly deformed along the upper surface of the upper guide member 81, and the sealing member 91 is moved from the equilibrium posture to the counterclockwise direction. Figure 6 When the processing unit P rotates, the hammer 99 does not contact the upper guide member 81.

[0053] After this, if Figure 5C As shown, the processing unit P is pulled out obliquely from the front and upward through the openings of the top plate and the front plate of the device body 3. Accordingly, the processing unit P is removed from the device body 3.

[0054] Reference Figure 7 , a case where a sealing member 101 is provided to block the gap G between the developing device 51 and the upper guide member 81 as a comparative example will be described. In this case, when the tip of the sheet S contacts the surface of the photosensitive drum 47, a closed space X surrounded by the developing device 51 (developing housing 61 and developing roller 65), the sealing member 101, the upper guide member 81, the sheet S, and the photosensitive drum 47 is formed. When the tip of the sheet S moves toward the transfer nip portion as the photosensitive drum 47 rotates, the volume of the space X changes (increases) by the amount Y of movement. When the volume of the space X changes in this way, a downward airflow is generated in the space X, and the position of the toner image formed on the surface of the photosensitive drum 47 is shifted downward, resulting in image defects such as horizontal streaks.

[0055] In contrast, in the present embodiment, as described above, a gap G is provided between the developing device 51 and the upper guide member 81, and a closed space as in the comparative example is not formed. Therefore, it is possible to suppress the airflow generated when the leading end of the sheet S moves toward the transfer nip portion as the photosensitive drum 47 rotates, thereby preventing image defects from occurring.

[0056] However, when the gap G is left, the toner scattered through the gap G may accumulate on the upper guide member 81. Therefore, when the process unit P is rotated upward when the process unit P is removed from the apparatus body 3, the toner T accumulated on the upper guide member 81 may fall through the gap G between the upper guide member 81 and the developing device 51.

[0057] However, in the present embodiment, when the processing unit P is rotated when being removed from the apparatus main body 3, as shown in FIG. Figure 6 As shown, the tip end of the plate 95 of the sealing member 91 contacts the upper guide member 81, so the toner T accumulated on the upper guide member 81 is blocked by the plate 95. Therefore, the toner accumulated on the upper guide member 81 can be prevented from falling.

[0058] In addition, since the sealing member 91 rotates by its own weight between a posture in which the space between the upper guide member 81 and the developing device 51 is opened and a posture in which the plate 95 contacts the upper guide member 81 as the processing unit P rotates, a structure for rotating the sealing member 91 is no longer required.

[0059] Although the present invention describes specific embodiments, the present invention is not limited to the above-described embodiments, and those skilled in the art can modify the above-described embodiments without departing from the scope and spirit of the present invention.

Claims

1. An image forming apparatus comprising a processing unit, wherein the processing unit is configured to be detached from the apparatus body after rotating upward around a rotation axis, It is characterized in that The processing unit comprises a photosensitive drum, a developing device, a guide component and a sealing component, wherein: The photosensitive drum rotates along a specified rotation direction; The developing device faces the surface of the photosensitive drum to form a developing nip; The guide member guides the sheet to a position downstream of the developing nip in the rotation direction by contacting the upper surface of the sheet; The sealing member is rotatably supported between the developing device and the guide member. The sealing member opens a gap between the developing device and the guide member when the processing unit is installed in the device body, and rotates to close the gap between the developing device and the guide member when the processing unit is removed from the device body and rotated upward.

2. The image forming apparatus according to claim 1, It is characterized in that The sealing component comprises a shaft component, a hammer portion and a plate, wherein: The shaft member is rotatably supported by the developing device; The hammer is arranged to extend downward from the shaft member; The plate is supported by the shaft member. When the processing unit is mounted on the device body, the plate is supported by the hammer portion in a posture away from the guide member. When the process unit is removed from the apparatus main body and rotated upward, the shaft member rotates relative to the developing device, causing the plate member to come into contact with the guide member.

3. The image forming apparatus according to claim 1, It is characterized in that The lower surface of the guide member is formed in a flat surface shape that is curved in an upward arc shape along the conveying direction of the sheet.

4. The image forming apparatus according to claim 2, It is characterized in that In a state where the processing unit is mounted on the apparatus main body, the plate member of the sealing member is supported in a substantially horizontal posture.

5. The image forming apparatus according to claim 1, It is characterized in that The developing device is arranged at a position farther from the rotating shaft than the photosensitive drum.

Images