JP2016035516A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that controls an airflow generated by a behavior of a sheet conveyed to a transfer device through a guide part to prevent a deterioration in image quality such as generation of lateral stripes.SOLUTION: An image forming apparatus 1 has a guide part 6 that forms a conveyance path 26 for a sheet P to be conveyed from a paper feeding part 5 to an image carrier 11. A channel 35 is formed between a developing device 13 and the guide part 6. The channel 35 has an opening/closing member 40 that can open/close the channel 35 and is communicated to a paper feeding part-side space S3 of the conveyance path 26 and an image carrier-side space S1 of the conveyance path 26. When the tip of the sheet P contacts the surface of the image carrier 11, the opening/closing member 40 opens the channel 35 to cause an airflow generated in the image carrier-side space S1 to flow into the channel 35, and when the rear end of the sheet P leaves the paper feeding part 5, closes the channel 35 to prevent an airflow generated in the paper feeding part-side space S3 from passing through the channel 35.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an image forming apparatus for forming a toner image on an image carrier and transferring the toner image onto a sheet to form an image.

  In an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multifunction machine, a toner image is formed by developing an electrostatic latent image formed on an image carrier by a developing device with a toner, and a transfer device. Thus, the toner image is transferred from the image carrier to the sheet. If an air flow is generated in the space between the developing device and the transfer device due to the behavior of the paper, the image quality may deteriorate due to the air flow.

  The flow of air due to the behavior of the paper will be described with reference to FIGS. As shown in FIG. 6A, the sheet P passes through the registration roller pair 101 and is conveyed along the guide unit 102, and is formed between the image carrier 103 and the transfer roller 104. Then, the toner image is transferred onto the paper P at the transfer nip 105.

  The sheet P to which the toner image has been transferred is conveyed to the fixing device, but when the trailing edge of the sheet P leaves the exit of the registration roller pair 101 (see the two-dot chain line in FIG. 6A), elasticity is generated. Thus, it bounces to the left in FIG. 6A (see the solid line in FIG. 6A) and hits the guide plate forming the guide portion 102. Then, from the space S101 on the entrance side of the guide unit 102, through the space S102 between the guide unit 102 and the registration roller pair 101, and the space S103 between the guide unit 102 and the developing device 106, the image carrier 103 is moved. An airflow F101 directed in the direction is generated. The air flow F101 affects the toner image formation in the developing nip 107 between the image carrier 103 and the developing device 106, and deteriorates the image quality. Specifically, as shown in FIG. 6B, when the gray image G is printed, a horizontal stripe L is generated on the rear end side of the paper P.

  In order to prevent the generation of the air flow F101, as shown in FIG. 7, a method of closing the space S102 between the registration roller pair 101 and the guide portion 102 with a wind shielding member 110 is conceivable. By providing such a wind-shielding member 110, the air flow F101 toward the space S103 between the guide unit 102 and the developing device 106 is blocked, so that the occurrence of the horizontal stripe L on the rear end side of the gray image G is prevented. . However, when the wind shielding member 110 is provided in the space S102, there arises a problem that abnormal noise is generated or paper dust is accumulated.

  Alternatively, as shown in FIG. 8A, it is also conceivable to block the space S103 between the developing device 106 and the guide unit 102 with the wind shielding member 111. However, when the wind shielding member 111 is provided in the space S103, the following problem occurs. That is, when the leading edge of the sheet P conveyed through the guide unit 102 hits the surface of the image carrier 103, as shown in FIG. 8A, development is performed from the space S104 on the exit side of the guide unit 102. An air flow F102 is generated in the direction of the nip 107. The air flow F102 normally flows into the space S103 between the guide unit 102 and the developing device 106, but does not flow into the development nip 107. However, if the space S103 is closed by the wind shielding member 111, the escape space of the air flow F102 disappears, and the development is completed. It will flow into the nip 107. As a result, as shown in FIG. 8B, when the gray image G is printed, the image quality is deteriorated such that the horizontal stripe L is generated on the front end side of the paper P.

  As a measure for preventing deterioration of image quality due to the air flow in the vicinity of the image carrier, Patent Document 1 discloses an image forming apparatus that prevents scattering of toner due to an air flow along the surface of the image carrier caused by rotation of the image carrier. Has been proposed. In this image forming apparatus, an airflow passing between the guide portion and the paper feeding portion is formed, and a part of the airflow along the surface of the image carrier is joined to this airflow, whereby the airflow along the surface of the image carrier. Is directed away from the image carrier to suppress toner scattering.

JP2011-2594A

  However, in the image forming apparatus described in Patent Document 1, the direction of the airflow that passes between the guide unit and the paper feed unit is a direction that intersects the paper conveyance direction, and therefore the guide is provided from the paper feed unit. There is a risk of affecting the conveyance of the paper to the section, and fine control is required to form the airflow so as not to interfere with the conveyance of the paper. Further, while the sheet is being conveyed from the sheet feeding unit to the guide unit, an air flow cannot be formed between the sheet feeding unit and the guide unit, and thus occurs when the leading edge of the sheet hits the image carrier. It is impossible to control the airflow or the airflow generated when the trailing edge of the paper is separated from the paper feed unit. Therefore, it is not possible to suppress image quality deterioration such as horizontal stripes caused by these airflows.

  In view of the above-described circumstances, the present invention provides an image forming apparatus that prevents an image quality deterioration such as the occurrence of horizontal stripes by controlling the airflow generated by the behavior of a sheet passing through a guide unit toward a transfer device. Objective.

  In order to solve the above problems, an image forming apparatus of the present invention includes a developing device that develops an electrostatic latent image formed on an image carrier into a toner image, and the toner image on a sheet supplied from a paper feeding unit. A transfer unit that transfers, a guide unit that forms a conveyance path of the sheet from the sheet feeding unit to the transfer unit along the surface of the image carrier between the developing unit and the transfer unit; Formed between the developing device and the guide unit, and communicates with a paper feed unit side space where the transport path faces the paper feed unit and an image carrier side space where the transport path faces the image carrier. And an opening / closing member capable of opening and closing the flow path, and the opening / closing member is configured to contact the front surface of the image carrier with the opening / closing member. The air flow generated in the space on the image carrier side by opening the flow channel flows into the flow channel. When the rear end of the paper leaves the paper feed unit, the flow path is closed to prevent the air flow generated in the paper feed unit side space from passing through the flow path. It is characterized by.

  By adopting such a configuration, the airflow generated when the leading edge of the paper comes into contact with the surface of the image carrier from the guide portion flows into the flow path without being directed toward the developing device, and the trailing edge of the paper However, the airflow generated when the paper leaves the paper feed section cannot pass through the flow path and therefore does not go in the direction of the developing device. Accordingly, since the toner image can be formed in the developing device without being affected by the airflow generated by the behavior of the paper conveyed to the transfer device, it is possible to prevent image quality deterioration such as the occurrence of horizontal stripes.

  In the image forming apparatus of the present invention, the opening / closing member is a shutter member that can rotate between an open position that opens the flow path and a close position that closes the flow path, and the shutter member is a leading edge of the sheet. Is rotated to the open position when contacting the surface of the image carrier, and is rotated to the closed position when the rear end of the sheet is detached from the sheet feeding unit. It may be driven based on the position of the paper along the line.

  By adopting such a configuration, the air flow can be controlled by opening and closing the flow path at an accurate timing, so that it is possible to reliably prevent deterioration in image quality such as the occurrence of horizontal stripes.

  In the image forming apparatus of the present invention, the opening / closing member is opened by an airflow flowing from the image carrier side space into the flow path, and is closed by an airflow flowing from the paper feed unit side space into the flow path. It is good also as a feature.

  By adopting such a configuration, the drive mechanism for the opening / closing member is not required, and the configuration of the image forming apparatus can be simplified.

  In the image forming apparatus according to the aspect of the invention, the developing device includes a supporting member that supports a developing roller that supplies toner to the image carrier, and the guide portions are disposed on the developing device side and the transfer device side. The total area of the openings of the support member and the image carrier is smaller than the total area of the openings of the developing device side guide plate and the image carrier. good.

  By adopting such a configuration, the air generated by the contact between the front end of the sheet and the surface of the photosensitive drum can be prevented from entering between the image carrier and the developing device. Can be less affected by airflow.

  In the image forming apparatus according to the aspect of the invention, a cross-sectional area of the flow path may be larger than a total area of openings of the support member and the image carrier.

  By adopting such a configuration, the air generated by the contact between the front end of the sheet and the surface of the photosensitive drum is difficult to enter between the image carrier and the developing device, and can easily enter the flow path. Thus, the generated airflow can be more smoothly introduced into the flow path, and the toner image forming operation in the developing device can be hardly affected by the airflow.

  According to the present invention, there is no influence of the airflow generated when the leading edge of the paper comes into contact with the surface of the image carrier from the guide section or the airflow generated when the trailing edge of the paper leaves the paper feeding section. Since the toner image can be formed in the developing device, it is possible to prevent image quality deterioration such as the occurrence of horizontal stripes.

1 is a schematic diagram illustrating an outline of a printer according to an embodiment of the present invention. 1 is a front view illustrating an outline of an image forming unit in a printer according to an embodiment of the present disclosure. In the printer which concerns on one Embodiment of this invention, it is a front view which shows the structure of a guide part. 4A and 4B are front views showing the operation of the opening / closing member in the printer according to the embodiment of the present invention. FIG. 4A shows a state where the leading edge of the paper reaches the photosensitive drum, and FIG. The rear end is separated from the exit of the registration roller pair. FIG. 5A is a front view illustrating the operation of another example of the opening / closing member in the printer according to the embodiment of the present invention. FIG. 5A illustrates a state in which the leading edge of the sheet reaches the photosensitive drum, and FIG. ) Shows a state in which the trailing edge of the paper is separated from the exit of the registration roller pair. FIG. 6A is a front view for explaining the air flow generated when the trailing edge of the paper is separated from the exit of the registration roller pair in the conventional printer, and FIG. 6B is an image quality of the image generated by this air flow. It is a top view of the paper which shows deterioration. In the conventional printer, it is a front view which shows the state which provided the wind-shielding member between the guide part and the registration roller pair. FIG. 8A is a front view for explaining the airflow generated when the leading edge of the paper comes into contact with the photosensitive drum when a wind shielding member is provided between the guide unit and the developing device in the conventional printer. FIG. 8B is a plan view of the paper showing image quality degradation caused by the airflow.

  Hereinafter, an image forming apparatus according to an embodiment of the present disclosure will be described with reference to the drawings.

  First, an overall main configuration of the printer 1 (image forming apparatus) will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic diagram illustrating an outline of a printer according to an embodiment of the present invention, and FIG. 2 is a diagram illustrating a configuration of an image forming unit. Hereinafter, the front side of the paper in FIG. 1 will be described as the front side (front side) of the printer 1, and the left and right directions will be described with reference to the direction viewed from the front of the printer 1.

  The printer 1 includes a box-shaped printer main body 2, and a paper feeding device 4 that feeds recording paper from a paper feeding cassette 3 containing paper (not shown) is provided at the lower portion of the printer main body 2. It has been. A registration roller pair 5 (paper feeding unit) including a pair of left and right rollers 5L and 5R is provided on the upper right side of the paper feeding device 4, and a guide unit 6 is provided above the registration roller pair 5. A paper discharge tray 7 is formed on the upper part of the printer main body 2. Inside the printer main body 2, an exposure device 8 composed of a laser scanning unit (LSU) is arranged on the left side, and a toner container 9 for containing toner is arranged in the center. An image forming unit 10 is provided on the right side of the toner container 9.

  The image forming unit 10 will be described with reference to FIG. The image forming unit 10 is rotatably provided with a photosensitive drum 11 as an image carrier. Around the photosensitive drum 11, a charging device 12, a developing device 13, a transfer roller 14 (transfer device), a static eliminating device 15, and a cleaning device 16 are disposed in the rotation direction of the photosensitive drum 11 (see FIG. 1). Arranged in order along the arrow X).

  The charging device 12 includes a charging roller 12a that contacts and charges the photosensitive drum 11, and a charging cleaning roller 12b, and is supported by a support member 12c.

  The developing device 13 is a jumping developing type developing device having a developing roller 13a that supplies toner to the photosensitive drum 11, a magnetic roller, and a stirring member (both not shown). A developing bias having the same polarity is applied to cause the toner to fly on the surface of the photosensitive drum 11. The developing roller 13a, the magnetic roller, and the stirring member are accommodated in the support member 13b. An opening is formed in the support member 13b on the surface facing the photosensitive drum 11, and a developing nip 17 is formed between the developing roller 13a and the photosensitive drum 11 through this opening.

  The transfer roller 14 forms a transfer nip 19 between the photosensitive drum 11 and a predetermined transfer bias is applied.

  The cleaning device 16 includes a cleaning blade 16a that contacts the surface of the photosensitive drum 11, a cleaning roller 16b that applies toner to the surface of the photosensitive drum 11, and a recovery spiral 16c that recovers toner scraped off from the cleaning roller 16b. These are accommodated in the support member 16d. The support member 16d is provided with a static eliminator 15, a peeling claw 21, and a conveyance auxiliary member 22 on the side surface on the transfer nip 19 side.

  A description will be given with reference to FIG. 1 again. A fixing device 24 is provided above the image forming unit 10, and a paper discharge unit 25 facing the paper discharge tray 7 is provided at the upper left of the fixing device 24.

  Further, inside the printer main body 2, a paper conveyance path 26 from the paper feeding device 4 through the registration roller pair 5, the guide unit 6, the transfer nip 19, and the fixing device 24 to the paper discharge unit 25. Is formed.

  Next, an image forming operation of the printer 1 having such a configuration will be described. When image data is input from a computer or the like connected to the printer 1, an image forming operation is executed as follows.

  First, after the surface of the photosensitive drum 11 is charged by the charging device 12, exposure corresponding to image data is performed on the photosensitive drum 11 by laser light from the exposure device 8 (see the two-dot chain line p in FIG. 1). The electrostatic latent image is formed on the surface of the photosensitive drum 11. This electrostatic latent image is developed into a toner image by the developing device 13.

  On the other hand, the sheet taken out from the sheet feeding cassette 3 by the sheet feeding device 4 is conveyed to the transfer nip 19 through the guide unit 6 after being matched with the above-described image forming operation by the registration roller pair 5. Then, at the transfer nip 19, a predetermined electrostatic bias is applied to the transfer roller 14, and the toner image on the photosensitive drum 11 is transferred to the paper. The sheet on which the toner image has been transferred is transported downstream in the transport path 26. Then, the toner image enters the fixing device 24 and the toner image is fixed on the paper. The sheet on which the toner image is fixed is discharged from the sheet discharge unit 25 to the discharge tray 7. The potential remaining on the photosensitive drum 11 is neutralized by the neutralizing device 15, and the toner remaining on the photosensitive drum 11 is collected by the cleaning device 16.

  Next, referring to FIG. 3, the guide unit 6 that guides the paper P from the registration roller pair 5 to the transfer nip 19 will be described.

  In the space between the developing device 13 and the transfer nip 19, the guide unit 6 forms a sheet conveyance path 26 that extends in the vertical direction from the exit 5 a of the registration roller pair 5 toward the photosensitive drum 11. The guide unit 6 includes an upper guide plate 31 disposed on the developing device 13 side and a lower guide plate 32 disposed on the transfer nip 19 side with the exit 5a of the registration roller pair 5 interposed therebetween.

  The upper guide plate 31 includes a registration roller facing portion 31a facing above the left registration roller 5L via a gap, a lower guide portion 31b extending obliquely leftward from the right end of the registration roller facing portion 31a, and a lower guide portion 31b. A middle guide portion 31c extending substantially vertically from the upper end of the first guide portion 31c, and an upper guide portion 31d extending obliquely upward to the right from the upper end of the middle guide portion 31c toward the surface of the photosensitive drum 11.

  A corner 31 e between the registration roller facing portion 31 a and the lower guide portion 31 b is formed as an acute angle, and this corner 31 e is formed so as to be closest to the outlet 5 a of the registration roller pair 5. However, the corner 31e is provided slightly to the left of the outlet 5a so as not to interfere with the leading edge of the paper P that has passed through the outlet 5a of the registration roller pair 5.

  The upper guide plate 31 has a total area in the opening D1 between the tip 31e of the upper guide portion 31d on the photosensitive drum 11 side and the surface of the photosensitive drum 11 such that the surface of the supporting member 13b of the developing device 13 and the surface of the photosensitive drum 11 is. The opening D2 is provided so as to be wider than the total area of the openings.

  The lower guide plate 32 includes a registration roller facing portion 32a that is opposed to the right side of the registration roller 5R via a gap, a lower guide portion 32b that extends diagonally upward to the left from the left end of the registration roller facing portion 32a, and a lower guide portion 32b. An upper guide portion 32c extending substantially vertically from the upper end of the upper guide portion 32c, and a photosensitive drum facing portion 32d extending from the upper end of the upper guide portion 32c so as to face the photosensitive drum 11 via a gap.

  By the upper and lower guide plates 31 and 32 having such a shape, the conveyance path 26 is formed so that the width is narrowed from the registration roller pair 5 toward the photosensitive drum 11 and is slightly curved in the right direction. The sheet P hits the photosensitive drum 11 from the substantially tangential direction of the photosensitive drum 11 at a position downstream of the transfer nip 19 in the rotation direction of the photosensitive drum 11 along the conveying path 26 and is conveyed to the transfer nip 19. It has become so.

  Between the upper guide plate 31 of the guide portion 6 and the support member 13b of the developing device 13, a flow path 35 extending in the vertical direction is formed. The upper end opening of the flow path 35 communicates with the space S1 (image carrier side space) on the photosensitive drum 11 side of the transport path 26. The lower end opening of the flow path 35 communicates with the space below the developing device 13 and also passes through the space S2 between the registration roller facing portion 31a of the upper guide plate 31 of the guide portion 6 and the left registration roller 5L. Thus, the space S3 (paper feeding unit side space) on the registration roller pair 5 side of the conveyance path 26 communicates.

  Furthermore, the flow path 35 is formed so that the cross-sectional area is larger than the total area in the opening D2 between the support member 13b of the developing device 13 and the surface of the photosensitive drum 11.

  An opening / closing member 40 that opens and closes the flow path 35 is provided in the middle of the flow path 35. The opening / closing member 40 includes a shutter plate 41 (shutter member) and a rotation shaft 42, and the rotation shaft 42 is rotatably supported on the outer surface of the support member 13 b of the developing device 13. However, it rotates between a closed position (indicated by a two-dot chain line in FIG. 3) that closes the flow path 35 and an open position that opens the flow path 35. In the closed position, the tip of the shutter plate 41 rotates until it contacts the outer surface of the middle guide portion 31c of the upper guide plate 31 to close the flow path 35. In the open position, the shutter plate 41 is supported by the support member 13b. The flow path 35 is opened by rotating until it comes into contact with the outer surface.

  In the printer 1 having the above configuration, an operation of transporting the paper P to the transfer nip 19 will be described with reference to FIG. 4A shows a state where the leading edge of the paper has reached the photosensitive drum, and FIG. 4B shows a state where the trailing edge of the paper is separated from the exit of the registration roller pair.

  In the state where the image forming operation is not performed, in the opening / closing member 40, the shutter plate 41 is rotated to the open position, and the toner scattered around the photosensitive drum 11 passes through the flow path 35. It is removed from the photosensitive drum 11. The sheet P sent out from the sheet cassette 3 by the sheet feeding device 4 after the image forming operation is started is detected by a sensor (not shown) at the leading end in the transport direction in the registration roller pair 5, and the sheet P After the leading end position and the position of the toner image formed on the surface of the photosensitive drum 11 are synchronized, the toner is discharged from the registration roller pair 5.

  The sheet P discharged from the exit 5a of the registration roller pair 5 is transported along the transport path 26 of the guide unit 6 and contacts the surface of the photosensitive drum 11. By this contact, as shown in FIG. 4A, an air flow F1 is generated in the photosensitive drum side space S1. Here, the opening / closing member 40 is rotated to the open position, and the flow path 35 is opened. The total area in the opening D1 between the tip 31e of the upper guide plate 31 and the surface of the photosensitive drum 11 is wider than the total area in the opening D2 between the support member 13b of the developing device 13 and the surface of the photosensitive drum 11. Since the cross-sectional area of the flow path 35 is wider than the total area at the opening D2 between the support member 13b of the developing device 13 and the surface of the photosensitive drum 11, the air flow F1 is as indicated by the arrow in FIG. It flows into the flow path 35 instead of the development nip 17. That is, the airflow F1 is less likely to affect the development nip 17.

  Immediately before the sheet P is further conveyed and the rear end is discharged from the exit 5a of the registration roller pair 5, the shutter plate 41 is driven to rotate to the closed position in the opening / closing member 40, and the flow path 35 is closed. Is done. When the paper P is discharged from the registration roller pair 5, the rear end of the paper P hits the corner 31 e of the upper guide plate 31 in the transport path 26 of the guide unit 6, and the registration of the upper guide plate 31 from the paper supply unit side space S 3. An air flow F2 is generated toward the space S2 between the roller facing portion 31a and the left registration roller 5L. As shown in FIG. 4 (B), a part of this air flow F2 (see the dotted line in FIG. 4 (B)) flows into the flow path 35, but the flow path 35 rises up because the flow path 35 is closed. This does not reach the surface of the photosensitive drum 11 or the development nip 17. That is, the air flow F2 is less likely to affect the toner image formed on the photosensitive drum 11. When the rear end of the paper P enters the guide portion 6, the shutter plate 41 is driven to rotate to the open position in the opening / closing member 40.

  As described above, in the printer 1 according to this embodiment, the leading edge of the paper P discharged from the registration roller pair 5 is photosensitive by opening and closing the flow path 35 by the opening / closing member 40 in accordance with the transport position of the paper P. It is possible to flow an air flow generated when it hits the body drum 11 and an air flow generated when the rear end of the paper P is separated from the exit of the registration roller pair 5 in a direction away from the developing nip 17. Accordingly, the influence of the behavior of the paper P on the development work in the development nip 17 can be reduced, and image quality deterioration such as the occurrence of horizontal stripes can be prevented.

  Further, the total area at the opening D2 between the support member 13b of the developing device 13 and the surface of the photosensitive drum 11 is the total area at the opening D1 between the tip 31e of the upper guide plate 31 of the guide portion 6 and the surface of the photosensitive drum 11. The cross-sectional area of the flow path 35 is wider than the total area in the opening D <b> 2 between the support member 13 b of the developing device 13 and the surface of the photosensitive drum 11. With such a structure, the airflow generated in the photosensitive drum side space S1 when the leading edge of the paper P hits the surface of the photosensitive drum 11 is difficult to enter the developing device nip 17 and easily enters the flow path 35. Yes. Therefore, the generated airflow can be more smoothly introduced into the flow path 35, and the development nip 17 can be less affected.

  The rotation of the shutter plate 41 of the opening / closing member 40 can be easily controlled based on, for example, the size of the paper P, the timing at which the paper P is discharged from the registration roller pair 5, and the like.

  With reference to FIG. 5, another example of the opening and closing member 40 will be described. 5A and 5B are diagrams for explaining the operation of transporting the paper to the transfer nip. FIG. 5A shows a state where the leading edge of the paper has reached the photosensitive drum, and FIG. 5B shows the trailing edge of the paper. Shows a state away from the exit of the registration roller pair.

  As the opening / closing member 40, a valve member that is opened by an airflow flowing into the flow path 35 from the photosensitive drum side space S1 and closed by an airflow flowing into the flow path 35 from the paper feeding unit side space S3 can be used. The valve member is composed of a pair of rectangular film members 45 and 46 (valve members). As a material of the film members 45 and 46, a silicon film can be used. One film member 45 has an upper end fixed to the outer surface below the opening edge 13 d in the support member 13 b of the developing device 13, and hangs downward in the flow path 35. The other film-like member 46 has an upper end fixed to the outer surface below the tip of the upper guide plate 31 of the guide portion 6 and hangs downward in the flow path 35. The lower ends of the film members 45 and 46 are loosely in contact with each other due to the elasticity or friction of the film members.

  In the opening / closing member 40, when the air flow F2 generated in the photosensitive drum side space S1 due to the contact between the front end of the sheet P and the surface of the photosensitive drum 11 reaches the upper end of the flow path 35, the developing device as described above. Since it is difficult to enter the side 13, it enters the flow path 35. Then, an air current enters from between the upper ends of the film members 45 and 46 of the opening / closing member 40, and pressure is applied in a direction to open the lower ends of the film members 45 and 46 that are in contact with each other. The space opens. The generated airflow passes between the film members 45 and 46 and flows downward in the flow path 35.

  On the other hand, when the trailing edge of the paper P hits a corner of the upper guide plate 31 and an air flow F2 is generated in the paper feeding unit side space S3, the air flow is generated between the registration roller facing portion 31a of the upper guide plate 31 and the left registration roller 5L. Into the flow path 35 through the space S2. However, in the opening / closing member 40, no force is generated to separate the lower ends of the film-like members 45 and 46, so the flow path 35 remains closed. That is, the generated air flow F <b> 2 does not enter the flow path 35, and no air flow toward the surface of the photosensitive drum 11 is generated.

  In the opening / closing member 40 of this example, since the valve member is automatically opened by the air flow generated in the photosensitive drum side space S1, a mechanism for driving the opening / closing member 40 is not necessary, and the number of parts is reduced. Cost can be reduced.

  A single sheet-like member can be used as the valve member. In this case, one end of the sheet shape is rotatably supported on one outer surface of the support member 13b of the developing device 13 or the upper guide plate 31 of the guide unit 6. Then, the other end of the sheet-like member is movable to the lower side of the flow path 35 and is locked to the other outer surface of the developing device 13 or the guide unit 6 so that the upward movement is restricted. As a result, when the airflow enters from the upper side of the flow path 35 (the photosensitive drum side space S1 side), pressure is applied to the upper surface of the film-like member to release the locking, and the film-like member rotates downward. The flow path 35 is opened. On the other hand, when the airflow enters from the lower side of the flow path 35 (the side of the sheet feeding unit side space S3), pressure is applied to the lower surface of the sheet member, but the other end of the sheet-like member is restricted from moving upward. Therefore, it does not rotate upward and the flow path 35 is not opened.

  Further, in the embodiment of the present invention, the case where the configuration of the present invention is applied to the printer 1 has been described. However, in another different embodiment, the present invention is applied to an image forming apparatus other than the printer 1 such as a copying machine, a facsimile machine, and a multifunction machine. You may apply the structure of invention.

  Furthermore, since the above description of the embodiment of the present invention describes a preferred embodiment of the image forming apparatus according to the present invention, there may be various technically preferable limitations. The technical scope of the present invention is not limited to these embodiments unless specifically described to limit the present invention. That is, the above-described components in the embodiment of the present invention can be appropriately replaced with existing components and the like, and various variations including combinations with other existing components are possible. The description of the embodiment of the present invention described above does not limit the contents of the invention described in the claims.

1 Printer (image forming device)
5 Registration roller pair (paper feed unit)
11 Photosensitive drum (image carrier)
13 Developing device 13a Developing roller 13b Support member 14 Transfer roller (transfer device)
26 Transport path 31 Upper guide plate (developing device side guide plate)
32 Lower guide plate (transfer device side guide plate)
35 Flow path 40 Opening / closing member 41 Shutter plate (shutter member)
45, 46 Film member (valve member)
S1 Photosensitive drum side space (image carrier side space)
S3 Paper source side space

Claims (5)

A developing device for developing the electrostatic latent image formed on the image carrier into a toner image;
A transfer device for transferring the toner image to a sheet supplied from a sheet feeding unit;
A guide unit that forms a conveyance path of the sheet from the paper feeding unit to the transfer device along the surface of the image carrier between the developing device and the transfer device;
Formed between the developing device and the guide unit, and a paper feed unit side space where the transport path faces the paper feed unit, and an image carrier side space where the transport path faces the image carrier. A communication channel,
An image forming apparatus comprising:
An open / close member capable of opening and closing the flow path;
The opening / closing member is
When the leading edge of the paper comes into contact with the surface of the image carrier, the flow path is opened to flow an air flow generated in the image carrier side space into the flow path,
When the trailing edge of the paper leaves the paper feed unit, the flow path is closed to prevent an air flow generated in the paper feed unit side space from passing through the flow path. An image forming apparatus. The opening / closing member is a shutter member that is rotatable between an open position that opens the flow path and a close position that closes the flow path,
The shutter member rotates to the open position when the leading edge of the sheet contacts the surface of the image carrier, and to the closed position when the trailing edge of the sheet separates from the sheet feeding unit. The image forming apparatus according to claim 1, wherein the image forming apparatus is driven based on a position of the sheet along the transport path so as to rotate.   The opening / closing member is a valve member that is opened by an airflow flowing into the flow path from the image carrier side space and is closed by an airflow flowing into the flow path from the space on the paper feed unit side. The image forming apparatus according to claim 1. The developing device includes a support member that supports a developing roller that supplies toner to the image carrier.
The guide unit has a pair of guide plates disposed on the developing device side and the transfer device side,
The total area of the openings of the support member and the image carrier is narrower than the total area of the openings of the developing device side guide plate and the image carrier. The image forming apparatus described in the item.   The image forming apparatus according to claim 4, wherein a cross-sectional area of the flow path is larger than a total area of openings of the support member and the image carrier.

Images