JP2021173808A - Image forming apparatus - Google Patents

Abstract

To provide a configuration that can sufficiently suck in a developer scattered from a developing sleeve 44a.SOLUTION: A developer container 41 has a projection 48 and end ribs 49a, 49b. The projection 48 is formed to project toward a photoconductor drum on a downstream of the closest approach position of a developing sleeve 44a and the photoconductor drum in a direction of rotation of the developing sleeve 44a. The end ribs 49a, 49b are formed at both ends in a longitudinal direction of the developer container 41 to project toward the photoconductor drum. The end rib 49a is formed with an inflow opening 50 through which an air flow can flow into an air flow space 52 from an outside of the developer container 41, on the further upstream of an upstream end of a portion of the developer container 41 facing the developing sleeve 44a on the downstream of the closest approach position. The end rib 49b is formed with a suction opening 51 that can suck in the air flow from the air flow space 52 with an air flow generated by the suction fan 60.SELECTED DRAWING: Figure 2

Description

The present invention relates to an image forming apparatus such as a copier, a printer, a facsimile, and a multifunction device having a plurality of these functions.

The image forming apparatus includes a developing apparatus that develops an electrostatic latent image formed on an image carrier such as a photosensitive drum with a developing agent. In such a developing apparatus, an image is formed by supporting a developing agent contained in a developing container on a developing sleeve and transporting the developer to a region facing the photosensitive drum. At this time, the developer scattered from the developing sleeve or the like into the space between the developing container and the photosensitive drum may leak from the inside of the developing container to the outside and contaminate the inside of the apparatus. Therefore, a flow path is formed between the developing container and the photosensitive drum along the axial direction of the photosensitive drum, and an air flow along the extension direction can flow, and is scattered through this flow path. A configuration has been proposed in which the developed developer is sucked (Patent Document 1).

Japanese Unexamined Patent Publication No. 2011-191522

In recent years, the speed of the image forming apparatus has been increasing, and as the speed of the apparatus has been increased, the developer is likely to be scattered from the developing sleeve (developer carrier). In the case of the configuration described in Patent Document 1, the path of the airflow flowing into the flow path from the outside is not clearly described, and the airflow is assumed to flow into the flow path through a slight gap between the developing container and the photosensitive drum. In this case, it is difficult to generate a sufficient air flow in the flow path. Therefore, when the amount of the developer scattered from the developer carrier increases, the scattered developer may not be sufficiently sucked through this flow path.

An object of the present invention is to provide a configuration capable of sufficiently sucking a developer scattered from a developer carrier.

The image forming apparatus of the present invention is arranged to face a rotating image carrier, a developing container capable of accommodating a developing agent, and the image carrier, and rotates to support the developing agent in the developing container. A developer having a developer carrier for transporting to a region facing the image carrier and developing an electrostatic latent image on the image carrier, and an airflow generating means for generating an airflow are provided. The developing container is located in the longitudinal direction of the developing container, which intersects the rotational direction of the developing agent carrier, downstream of the closest position between the developing agent carrier and the image carrier in the rotational direction of the developing agent carrier. At both ends of the developing container in the longitudinal direction, and a projecting portion formed so as to project toward the image carrier so as to have a gap between the image carrier and the image carrier. A first end that is arranged over the projecting portion from at least the closest position and is formed so as to project toward the image carrier so as to have a gap between the image carrier and the image carrier. It has a protruding portion and a second protruding portion, and has the image carrier, the developer carrier, the protruding portion, the first end protruding portion, and the second end. When the space surrounded by the protruding portion is an air flow space through which airflow can flow, at least the first end protruding portion of the first end protruding portion and the second end protruding portion. With respect to the direction of rotation of the developing agent carrier, the outside of the developing container is located downstream of the closest position in the developing container and further upstream of the upstream end of the portion facing the developing agent carrier. A first opening through which airflow can flow into the airflow space is formed, and the airflow generated by the airflow generating means can suck airflow from the airflow space at the second end protruding portion. It is characterized in that a second opening is formed.

According to the present invention, the developer scattered from the developer carrier can be sufficiently sucked.

The schematic block sectional view of the image forming apparatus which concerns on 1st Embodiment. The schematic configuration perspective view of the developing apparatus which concerns on 1st Embodiment. FIG. 2 is a cross-sectional view taken along the broken line A in FIG. (A) A cross-sectional view taken along the broken line C in FIG. 2 and (b) a cross-sectional view taken along the broken line D in FIG. FIG. 2 is a cross-sectional view taken along the broken line B in FIG. FIG. 2 is a cross-sectional view of the vicinity of the closest position between the developing sleeve and the photosensitive drum in the broken line A of FIG. FIG. 2 is a cross-sectional view of the vicinity of the closest position between the developing sleeve and the photosensitive drum in the broken line B of FIG. The perspective view which shows the flow of the air flow in the developing apparatus which concerns on 1st Embodiment. A cross-sectional view of the developing apparatus according to the second embodiment (a) corresponding to the broken line C in FIG. 2 and (b) a cross-sectional view corresponding to the broken line D in FIG. A cross-sectional view of the developing apparatus according to the third embodiment (a) corresponding to the broken line C in FIG. 2 and (b) a cross-sectional view corresponding to the broken line D in FIG.

<First Embodiment>
The first embodiment will be described with reference to FIGS. 1 to 8. First, the schematic configuration of the image forming apparatus of this embodiment will be described with reference to FIG.

[Image forming device]
The image forming apparatus 100 is a so-called tandem in which image forming portions Y, M, C, and K for forming toner images of four colors of yellow, magenta, cyan, and black are provided along the rotation direction of the intermediate transfer belt 62. This is the configuration of the method. The image forming apparatus 100 produces a toner image (image) according to an image signal from a document reading device (not shown) connected to the apparatus main body or a host device such as a personal computer communicatively connected to the apparatus main body. Form on recording material. Examples of the recording material include sheet materials such as paper, plastic film, and cloth.

The four image forming units Y, M, C, and K included in the image forming apparatus 100 have substantially the same configuration except that the developed colors are different. Therefore, the image forming unit Y will be described below as a representative, and the description of the other image forming units will be omitted.

A cylindrical photoconductor, that is, a photosensitive drum 1A, is arranged as an image carrier in the image forming portion Y. The photosensitive drum 1A is rotationally driven in the direction of the arrow in the figure. A charging roller 2A (charging device), a developing device 4A, a primary transfer roller 61A, and a cleaning device 8A are arranged around the photosensitive drum 1A. A laser scanner (exposure apparatus) 3A is arranged above the photosensitive drum 1A in the drawing.

Further, an intermediate transfer belt 62 as an intermediate transfer body is arranged so as to face the photosensitive drums 1A, 1B, 1C, and 1D. The intermediate transfer belt 62 is stretched by a plurality of tension rollers, and is rotated (rotated) in the direction of an arrow in the drawing by being driven by a drive roller among the plurality of tension rollers. The secondary transfer outer roller 64 is arranged at a position facing the secondary transfer inner roller 63 and the intermediate transfer belt 62 of the plurality of tension rollers with the intermediate transfer belt 62 interposed therebetween, and the toner image on the intermediate transfer belt 62 is used as a recording material. It constitutes a secondary transfer unit T2 to be transferred. A fixing device 7 is arranged downstream of the secondary transfer unit T2 in the recording material transport direction.

Image formation in the image forming apparatus 100 configured in this way is performed as follows. First, the surface of the photosensitive drum 1A is uniformly charged by the charging roller 2A. By exposing the charged surface with the laser scanner 3A, an electrostatic latent image is formed on the photosensitive drum 1A. By adhering toner from the developing device 4A to the electrostatic latent image thus obtained, the electrostatic latent image is developed as a toner image. This toner image is transferred onto the intermediate transfer belt 62 by the primary transfer roller 61A. Such operations are also sequentially performed in the image forming units M, C, and K, and the toner images of four colors are superimposed on the intermediate transfer belt 62.

Then, after the four-color toner images are superimposed and transferred on the intermediate transfer belt 62, the four-color toner images are transferred to the recording material conveyed from the feed cassette (not shown) to the secondary transfer unit T2. This recording material is heated and pressurized by the fixing device 7 to be fixed, and then discharged to the outside of the image forming device 100. The residual toner remaining on the photosensitive drum 1A after the transfer is removed by the cleaning device 8A.

[Developer]
Next, the developing apparatus 4A of the present embodiment will be described with reference to FIGS. 2 and 3. Since the other developing devices 4B, 4C, and 4D have the same configuration as the developing device 4A, description and illustration thereof will be omitted.

The developing apparatus 4A includes a developing container 41, a cylindrical developing sleeve 44a as a developing agent carrier, and a regulating member 42. The developing container 41 can contain a developing agent containing a non-magnetic toner and a magnetic carrier. The developing container 41 has an opening at a portion facing the photosensitive drum 1A (FIG. 1), and the developing sleeve 44 is rotatably arranged so as to partially expose the opening.

The developing sleeve 44a is arranged so as to face the photosensitive drum 1A, and by rotating, the developing agent in the developing container is supported and conveyed to the region facing the photosensitive drum 1A (development region), and is carried on the photosensitive drum 1A (image). Develop an electrostatic latent image (on the carrier). The developing sleeve 44a is arranged so that the direction of the rotation axis is substantially parallel to the direction of the rotation axis of the photosensitive drum 1A. Further, it is rotationally driven in the direction of arrow α in FIG. 3 by a motor (not shown). The rotation direction of the developing sleeve 44a is the same direction (forward direction) as the rotation direction of the photosensitive drum 1A (arrow β direction in FIG. 3) at a position facing the photosensitive drum 1A.

The developing sleeve 44a is provided with a magnet roll 44b as a magnetic field generating means in a non-rotating manner. The magnet roll 44b has a plurality of magnetic poles along the rotation direction of the developing sleeve 44a, and magnetically attracts the developer to the surface of the non-magnetic developing sleeve 44a. The regulating member 42 is arranged through a predetermined gap of the developing sleeve 44a, and regulates the height of the magnetic spikes of the developing agent (layer thickness of the developing agent) formed on the developing sleeve 44a. The magnetic spikes are supported on the developing sleeve 44a in a state in which carriers to which toner is attached are connected like spikes.

Further, the developing container 41 is divided into a first developer transport path (first chamber) 45a and a second developer transport path (second chamber) 45b by a partition wall 43 extending in the horizontal direction. .. The first developer transport path 45a has a first screw 46a as a first transport member, and the second developer transport path 45b has a second screw 46b as a second transport member. Each is arranged.

The first screw 46a agitates and conveys the toner replenished to the developing container 41 from the toner replenishing device (not shown) and the developer in the first developing agent conveying path 45a to make the toner concentration uniform. .. The second screw 46b agitates and conveys the developer in the second developer transfer path 45b. Communication ports for communicating the first developer transport path 45a and the second developer transport path 45b are formed at both ends of the partition wall 43 in the width direction (direction of the rotation axis of the developing sleeve 44a), respectively. As a result, the first developer transport path 45a and the second developer transport path 45b form a circulation path in which the developer circulates.

In the present embodiment, the developer housed in the developing container 41 is a two-component developing agent in which a negatively charged non-magnetic toner and a magnetic carrier are mixed. The non-magnetic toner is a resin such as polyester or styrene containing a colorant, a wax component, or the like and pulverized or polymerized to form a powder. In this embodiment, one having an average particle size of 5 μm was used. The magnetic carrier is obtained by applying a resin coating to the surface layer of a core made of resin particles obtained by kneading ferrite particles or magnetic powder.

The process of developing the toner on the photosensitive drum 1A in the developing region will be described. As shown in FIG. 1, the photosensitive drum 1A is uniformly charged to the charging potential Vd [V] by the charging roller 2A, and then the image portion on which the image on the photosensitive drum 1A is formed is formed by the laser scanner 3A. It is exposed and has an exposure potential of Vl [V]. A DC voltage or a voltage obtained by superimposing an AC voltage on the DC voltage is applied to the developing sleeve 44a. When the voltage of the DC component of the developing sleeve 44a is Vdc, the absolute value | Vdc-Vl | of the difference from the exposure potential is called Vcont, which creates an electric field that carries the toner to the image unit.

Further, the absolute value | Vdc-Vd | of the difference between the DC voltage Vdc and the charging potential Vd is called Vback, and creates an electric field for the toner to be pulled back from the photosensitive drum 1A in the direction of the developing sleeve 44a. This is provided to suppress the so-called fog phenomenon in which the toner adheres to the non-image portion.

The developing sleeve 44a rotates in the direction of the arrow α in FIG. 3, attracts the developing agent by the magnetic field of the magnet roll 44b inside, and conveys the developing agent in the direction of the regulating member 42. The layer thickness of the spiked developer is regulated by the regulating member 42, and when it passes through the gap between the developing sleeve 44a and the regulating member 42, a developer layer having a predetermined layer thickness is formed on the developing sleeve 44a. The developer layer is then supported and transported to the developing region facing the photosensitive drum 1A as the developing sleeve 44a rotates, and develops an electrostatic latent image formed on the surface of the photosensitive drum 1A with magnetic spikes formed. do. During development, the developer comes into contact with the photosensitive drum 1 and develops a latent image at the time of contact. Therefore, the space between the photosensitive drum 1 and the developing sleeve 44a is filled with the developing agent. The developer after being subjected to development is peeled from the developing sleeve 44a at the peeling region as the developing sleeve 44a rotates, and returns to the inside of the developing container 41.

In the case of the developing apparatus 4A of the present embodiment as described above, the developing agent is supplied from the second developer transport path (first chamber) 45b to the developing sleeve 44a, and the first developer transport path (second chamber) 45a is supplied. The developer is recovered from the developing sleeve 44a. Further, the developing device 4A is a so-called vertical stirring type developing device in which the second developer transport path 45b is arranged above the first developer transport path 45a, and the developing sleeve 44a is the photosensitive drum 1A. At the position facing the above, it rotates so as to go downward in the direction of gravity.

[Shape of developing container]
Next, the shape of the developing container 41 will be further described with reference to FIGS. 2 and 3. The developing container 41 has a protruding portion 48 formed so as to protrude from the lower end portion toward the photosensitive drum 1A. Further, the developing container 41 has end ribs 49a and 49b formed so as to project toward the photosensitive drum 1A at both ends in the longitudinal direction intersecting the rotation direction (arrow α direction) of the developing sleeve 44a, respectively.

The protrusion 48 is arranged downstream of the closest position P between the developing sleeve 44a and the photosensitive drum 1A in the rotational direction of the developing sleeve 44a. In the present embodiment, it is provided below the closest position P in the direction of gravity, and in the illustrated example, it is provided at the lower end of the developing container 41. The developing container 41 has a wall portion 41b that forms a first developer transport path 45a. The wall portion 41b is provided on the photosensitive drum 1A side of the first developer transport path 45a, and the upper end portion faces the developing sleeve 44a. The projecting portion 48 is formed so as to project from the lower end portion of the wall portion 41b toward the photosensitive drum 1A.

Such a protrusion 48 is arranged along the longitudinal direction of the developing container 41 (the direction of the rotation axis of the developing sleeve 44a) that intersects the rotating direction of the developing sleeve 44a, and has a gap between the protruding portion 48 and the photosensitive drum 1A. It is formed to have. In the present embodiment, the protruding portion 48 is provided over the entire area between the end ribs 49a and 49b. The gap between the protruding portion 48 and the photosensitive drum 1A is, for example, 2 mm.

Further, at the tip of the protruding portion 48, a bent portion 48a that is bent upward is formed so that the toner that has fallen from the developing sleeve 44a can be held. The bent portion 48a is curved or inclined along the curvature of the surface of the photosensitive drum 1A. The gap between the tip of the protruding portion 48 including the bent portion 48a and the photosensitive drum 1A is set to, for example, 2 mm. The bent portion 48a may be omitted.

The end rib 49a as the first end protrusion is provided at one end in the longitudinal direction of the developing container 41. In the present embodiment, the front side of the image forming apparatus, that is, the end portion on the side where the apparatus is operated is defined as one end portion in the longitudinal direction. On the other hand, the end rib 49b as the second end protrusion is provided at the other end of the developing container 41 in the longitudinal direction. The other end in the longitudinal direction is the end on the rear side (back side) of the image forming apparatus.

Such end ribs 49a and 49b are arranged so as to extend from at least the closest position P to the protruding portion 48 and to have a gap between the end ribs 49a and 49b and the photosensitive drum 1A. In the present embodiment, as shown in FIGS. 7A and 7B described later, the end ribs 49a and 49b are in the range from the position above the closest position in the direction of gravity to the lower end of the developing container 41. It is provided and faces the photosensitive drum 1A via a gap. The end ribs 49a and 49b are the range in which the developer supported on the developing sleeve 44a comes into contact with the photosensitive drum 1A and this range when viewed from the longitudinal direction of the developing container 41 intersecting the rotation direction of the developing sleeve 44a. It is preferable that the film is arranged so as to overlap the range below the direction of gravity. The gap between the end ribs 49a and 49b and the photosensitive drum 1A is, for example, 2 mm.

[Airflow space]
In the present embodiment, as described above, the airflow space (airflow space) 52 is formed by forming the projecting portions 48 and the end ribs 49a and 49b in the developing container 41. That is, the space surrounded by the photosensitive drum 1A, the developing sleeve 44a, the protruding portion 48, and the end ribs 49 and 49b is used as the airflow space 52 through which the air flow can flow. The airflow space 52 is a satin-finished portion excluding the portion showing the developer t in FIG.

Here, FIG. 3 is a cross-sectional shape at the position of the broken line A portion of FIG. 2, which is the central portion of the developing apparatus 4A in the longitudinal direction. The developing agent t is supported on the developing sleeve 44a as shown by the satin finish, and the gap between the developing sleeve 44a and the photosensitive drum 1A is closed by the developing agent t.

As described above, as the speed of the apparatus increases, the developer tends to scatter from the developing sleeve 44a. In the present embodiment, the developer scattered from the developing sleeve 44a is sucked through the airflow space 52 to prevent the developing agent from scattering to the outside of the developing apparatus 4A. Therefore, as shown in FIGS. 2 and 4 (a) and 4 (b), of the end ribs 49a and 49b, the front end rib 49a has an inflow opening 50 as an airflow inflow portion at the back. A suction opening 51 as an airflow suction portion is opened in the side end rib 49b. Then, the airflow is circulated in the airflow space 52 by using the entrances and exits of these two airflows. FIG. 4A is a cross-sectional shape at the position of the broken line C portion of FIG. 2, which is one end portion in the longitudinal direction of the developing apparatus 4A, and FIG. 4B is a diagram showing the other end portion in the longitudinal direction of the developing apparatus 4A. It is a cross-sectional shape at the position of the broken line D portion of 2.

This will be described more specifically. The inflow opening 50 as the first opening is formed in the end rib 49a so as to penetrate the end rib 49a in the longitudinal direction, and an opening through which airflow can flow into the airflow space 52 from the outside of the developing container 41. Is. The suction opening 51 as the second opening is formed in the end rib 49b so as to penetrate the end rib 49b in the longitudinal direction, and is an opening capable of sucking airflow from the airflow space 52.

The inflow opening 50 is further upstream than the upstream end 41a (FIGS. 6 and 7) of the portion of the developing container 41 facing the developing sleeve 44a downstream of the closest position P in the direction of rotation of the developing sleeve 44a. It is formed. Further, the inflow opening 50 is formed so as to open to the upstream side of the portion (development nip portion) where the developer supported on the developing sleeve 44a comes into contact with the photosensitive drum 1A in the rotation direction of the developing sleeve 44a. ..

In the present embodiment, the inflow opening 50 is formed in a range including the closest position P with respect to the rotation direction of the developing sleeve 44a. In other words, the inflow opening 50 is formed upstream of the upstream end 41a so as to include the upstream of the developing nip portion, which is a portion where the developer supported on the developing sleeve 44a comes into contact with the photosensitive drum 1A.

Specifically, as shown in FIG. 7, which will be described later, the upper end in the gravity direction of the wall portion 41b of the developing container 41 facing the developing sleeve 44a is the upstream end 41a described above. An inflow opening 50 is formed above the horizontal line L passing through the upstream end 41a. That is, the lower end of the inflow opening 50 in the gravity direction is above the horizontal line L passing through the upstream end 41a. On the other hand, the upper end of the inflow opening 50 in the gravity direction is preferably located below the upper end of the developing sleeve 44a in the gravity direction.

Further, the inflow opening 50 is formed so as to open on the photosensitive drum 1A side (image carrier side). As a result, when the developing sleeve 44a is assembled to the developing container 41, the rotating shaft 44c of the developing sleeve 44a can pass through the inflow opening 50. The rotary shaft 44c that has passed through the inflow opening 50 is rotatably supported by a rotary support portion (not shown).

It is preferable that the end portion of the inflow opening 50 opposite to the photosensitive drum 1A does not enter the first developer transport path 45a and the second developer transport path 45b. In other words, the inflow opening 50 is preferably formed within a range that overlaps with the developing sleeve 44a when viewed from the longitudinal direction. This is because if the inflow opening 50 is also open in the first developer transport path 45a or the second developer transport path 45b, the developer is likely to leak to the outside from the developer transport path through the opening. This is to become.

The suction opening 51 is formed downstream of the developing nip in the rotational direction of the developing sleeve 44a. In the present embodiment, the suction opening 51 is formed so as to open within the range of the airflow space 52 when viewed from the longitudinal direction. The opening shape of the suction opening 51 is substantially similar to the cross-sectional shape orthogonal to the longitudinal direction of the airflow space 52, and is substantially triangular in the present embodiment.

Further, as shown in FIG. 2, the suction opening 51 is connected to the suction fan 60 via a duct 53. The suction fan 60 as an airflow generating means for generating an airflow is installed, for example, on the device main body side of the image forming apparatus, and is connected to the duct 53 when the developing device 4A is attached to the apparatus main body. The suction opening 51 is an opening capable of sucking airflow from the airflow space 52 by the airflow generated by the suction fan 60.

Here, as shown in FIG. 2, the developing sleeve 44a is formed so as not to support the developer and the first region M whose surface is formed so as to support the developer in the longitudinal direction (rotational axis direction). It has a second region N and the like. The first region M is a region formed in the intermediate portion in the longitudinal direction of the developing sleeve 44a and corresponding to the maximum image region on which an image can be formed on the photosensitive drum 1A (on the image carrier). That is, with respect to the longitudinal direction (rotational axis direction) of the photosensitive drum 1A, the maximum region in which an electrostatic latent image can be formed is the maximum image region, and the developing sleeve 44a carries a developer so that the electrostatic latent image can be developed. The area is the first area.

In the first region of the developing sleeve 44a, for example, irregularities and grooves are formed on the surface of the developing sleeve 44a to facilitate carrying the developing agent. Specifically, the first region is a region where the surface is blasted, a plurality of grooves along the longitudinal direction are formed in the circumferential direction, and recesses called digging are formed at a plurality of locations on the surface. The area.

On the other hand, the second region is a region existing at both ends of the first region with respect to the longitudinal direction of the developing sleeve 44a, and is a region corresponding to a region deviating from the maximum image region. In the second region of the developing sleeve 44a, irregularities and the like are not formed as in the first region, and the surface is a smooth cylindrical surface. The magnet roll 44b arranged in the developing sleeve 44a exists at least in the entire longitudinal direction of the first region, and can support the developer in the first region. Normally, the end portion of the magnet roll 44b is arranged so as to enter a part of the second region, but the end portion of the magnet roll 44b has a ripple in the magnetic flux density, and the developer is placed on the developing sleeve 44a. It is difficult to form a magnetic field that supports the magnet.

As described above, since it is difficult for the developer to be supported in the second regions at both ends of the developing sleeve 44a, as shown in FIG. 5, the airflow easily passes around the developing sleeve 44a. FIG. 5 is a cross-sectional shape at the position of the broken line B portion of FIG. 2, which is a portion closer to the end portion in the longitudinal direction of the developing apparatus 4A. In the second region of the developing sleeve 44a, the developing agent in the developing container is not supplied, and the developing agent is almost absent on the surface. Therefore, in the second region, there is no developer in the gap between the developing sleeve 44a and the photosensitive drum 1A. Therefore, in the second region, airflow can flow upstream and downstream of the closest position P with respect to the rotation direction of the developing sleeve 44a.

On the other hand, in the first region of the developing sleeve 44a, as shown in FIG. 3, the developing agent is supported on the surface, and the gap between the developing sleeve 44a and the photosensitive drum 1A is closed by the developing agent. Therefore, in the first region, it is difficult for airflow to flow upstream and downstream of the closest position P with respect to the rotation direction of the developing sleeve 44a.

From the above, the airflow flowing in from the inflow opening 50 opened so as to face one end in the longitudinal direction of the developing sleeve 44a flows around the second region and into the airflow space 52. At this time, due to the rotation of the developing sleeve 44a, the airflow flowing in from the inflow opening 50 is easily carried to the airflow space 52 located downstream of the inflow opening 50 in the rotation direction of the developing sleeve 44a.

[Toner scattering]
Next, the state of air flow and toner scattering between the developing device 4A and the photosensitive drum 1A when the developing device 4A and the photosensitive drum 1A are driven will be described with reference to FIGS. 6 and 7. FIG. 6 shows the air flow and the toner flow in the cross section of the central portion in the longitudinal direction (the portion A of the broken line in FIG. 2) between the developing device 4A and the photosensitive drum 1A. The solid arrow indicates the direction of toner scattering.

The developing sleeve 44a and the photosensitive drum 1A are driven to generate an air flow on the surface. At this time, the airflow on the surface of the developing sleeve 44a is defined as the sleeve flow 410 and 420, and the airflow on the surface of the photosensitive drum 1A is defined as the drum flow 110 and 120. Since the sleeve flow 420 flows into the developing container 41, the pressure rises, an air flow 430 from the inside of the developing container 41 to the outside is generated, and the developer (here, toner) in the developing container 41 rides on the air flow 430. It flows out of the developing container 41. Then, the outflowing toner scatters along the drum flow 120 through the air flow 440 and becomes scattered toner.

Further, as described above, an airflow space 52 closed by a developing container 41, a developing sleeve 44a, a photosensitive drum 1A, a protruding portion 48, and end ribs 49a and 49b is formed on the downstream side of the developing nip portion. .. Therefore, the return flow 130 of the drum flow is generated, and a part of the scattered toner is collected by the return flow 130 to the developing sleeve 44a.

Most of the scattered toner is received by the protrusion 48 and stays there. However, if the amount of this scattered toner is large, it accumulates on the protruding portion 48 while the image formation is continued, and if the capacity of the protruding portion 48 is exceeded, it spreads to the outside, causing stains in the apparatus and stains on the roller that conveys the recording material. It becomes. When toner adheres to the rollers, the toner also adheres to the recording material conveyed to the rollers, leading to image defects.

The sleeve flow 450 and the drum flow 150 are also generated on the upstream side of the developing nip portion, but since the developer is present in the developing nip portion in the first region, the sleeve flow 450 and the drum flow 150 are the developing nip portions. It does not enter the downstream side of the, and becomes a return flow as shown by the arrow.

Next, FIG. 7 shows the air flow and the toner flow in the cross section of the second region (broken line B portion in FIG. 2) at the end in the longitudinal direction between the developing device 4A and the photosensitive drum 1A. The solid arrow indicates the direction of toner scattering, and the dotted arrow indicates the combined airflow of each airflow. In FIG. 7, unlike FIG. 6 described above, the amount of toner contained in the airflow is very small because there is no developer on the developing sleeve 44a. On the other hand, since there is no developer in the developing nip, the airflow passes through and the airflow from the upstream of the developing nip flows downstream as it is. Therefore, the synthetic airflow 500 as shown by the dotted line is generated, the air pressure is low on the upstream side of the developing nip portion, and the air pressure is high on the downstream side.

From the above, by providing the inflow opening 50 at the end upstream of the developing sleeve 44a in the rotational direction with respect to the developing nip as in the front end of the developing container 41, a negative pressure is obtained from the inflow opening 50. Air easily flows into the area on the upstream side of the developing nip. Then, the air that has flowed in is sent into the airflow space 52 along the synthetic airflow 500.

[Airflow of scattered toner suction]
Next, the air flow of the scattered toner suction will be specifically described with reference to FIG. At the front end of the developing device 4A in the longitudinal direction, the airflow flows in from the inflow opening 50 by the sleeve flow and the drum flow described above, and the airflow is pushed into the airflow space 52. The pushed airflow moves in the airflow space 52 from the front side to the back side. At this time, the above-mentioned scattered toner is involved and collected.
Then, the airflow containing the scattered toner on the back side is sucked into the suction opening 51. The sucked airflow is sucked into the duct 53 connected to the suction fan 60 (FIG. 2), the toner is removed by a filter (not shown), and then the airflow is discharged to the outside of the image forming apparatus 100.

As described above, in the case of the present embodiment, since the inflow opening 50 for allowing the airflow to flow into the airflow space 52 is formed at the longitudinal end of the developing device 4A, a sufficient airflow is generated in the airflow space 52. Easy to make. Therefore, the scattered toner can be sufficiently sucked. As described with reference to FIG. 7, since the synthetic airflow 500 is generated at the longitudinal end of the developing container 41, the inflow opening 50 is formed at the end of the developing container 41 to allow the airflow to enter the developing container 41. Easy to flow into. In particular, in the present embodiment, since the inflow opening 50 is formed so as to open even upstream of the developing nip, the combined airflow 500 makes it easier for the airflow to flow in.

Further, in the present embodiment, the inflow opening 50 is formed in the rotation direction of the developing sleeve 44a in the downstream of the closest position P and further upstream of the upstream end 41a of the wall portion 41b. As described with reference to FIGS. The toner inside flows out of the developing container 41. Therefore, if the inflow opening 50 is opened to the downstream side of the upstream end 41a, the toner on the airflow 430 may be scattered from the inflow opening 50 to the outside. On the other hand, in the present embodiment, since the inflow opening 50 is formed upstream of the upstream end 41a, such toner scattering is unlikely to occur.

[Example 1]
Next, in order to confirm the effect of this embodiment, the following experiment was conducted. Four developing devices were placed at the mounting positions of the developing devices 4A to 4D in the image forming device 100, and 40,000 images having an image ratio of 50% were formed on A4 size paper. In the experiment, as a comparative example, a developing device having no inflow opening 50 of the present embodiment as described in Patent Document 1 is attached, and as a first embodiment, the developing device of the above-described embodiment is attached. It was done in each case. Then, in Comparative Example and Example 1, it was confirmed whether or not roller stain, which is an image stain causing scattering, occurs in the output image. Roller stain is a phenomenon in which scattered toner adheres to a roller that conveys a recording material, leaving a roller mark on the recording material and causing stain on the output image. The environment was carried out in a laboratory with a temperature and humidity of 30 degrees and 80%. The results are shown in Table 1 below.

As is clear from Table 1, image stains due to roller traces were confirmed in Comparative Example, but were hardly confirmed in Example 1. From the above, it was found that toner scattering can be suppressed by using the configuration of this embodiment.

<Second embodiment>
The second embodiment will be described with reference to FIGS. 9A and 9B. In the first embodiment described above, a gap is provided between the end ribs 49a and 49b and the photosensitive drum 1A. On the other hand, in the present embodiment, this gap is eliminated. Since other configurations and operations are the same as those of the first embodiment described above, the same reference numerals are given to the same configurations, and the description and illustration are omitted or simplified. I will explain mainly.

In the present embodiment, the end rib 49a as the first end protrusion and the end rib 49b as the second end protrusion are provided so as to elastically contact the photosensitive drum 1A, respectively. Elastic members 54a and 54b are provided. The elastic members 54a and 54b are formed so as to be curved along the outer peripheral surface of the photosensitive drum 1A. Examples of the elastic members 54a and 54b include a porous body such as a sponge made of urethane or the like, a non-woven fabric, a sheet-like member, and the like. Examples of the sheet-shaped member include a PET (polyethylene terephthalate) sheet and a urethane sheet.

As shown in FIG. 9A, the elastic member 54a is provided on the side surface of the front end rib 49a in the longitudinal direction on the photosensitive drum 1A side so as to elastically contact the surface of the photosensitive drum 1A. .. The elastic member 54a is provided downstream of the inflow opening 50 in the rotational direction of the developing sleeve 44a. In the illustrated example, the elastic member 54a is provided in the range from the lower end of the inflow opening 50 to the lower end of the end rib 49a, and the elastic member 54a is brought into contact with the outer peripheral surface of the photosensitive drum 1A in this range.

As shown in FIG. 9B, the elastic member 54b is provided on the side surface of the end rib 49b on the back side in the longitudinal direction on the photosensitive drum 1A side so as to elastically contact the surface of the photosensitive drum 1A. There is. Since the inflow opening 50 is not formed in the end rib 49b, the elastic member 54b is provided over the entire side surface facing the photosensitive drum 1A of the end rib 49b via a predetermined gap (for example, 2 mm). There is. In the illustrated example, the elastic member 54b is provided in the range from the upstream position of the developing nip portion to the lower end of the end rib 49b, and the elastic member 54b is brought into contact with the outer peripheral surface of the photosensitive drum 1A in this range. ..

As described above, in the present embodiment, the elastic members 54a and 54b are provided on the end ribs 49a and 49b, respectively, so that the gap between the end ribs 49a and 49b and the photosensitive drum 1A is substantially zero. As a result, it is possible to suppress the scattering of toner from between the end ribs 49a and 49b and the photosensitive drum 1A, enhance the effect of recovering the toner by the air flow flowing through the air flow space 52, and further suppress the scattered toner.

[Example 2]
Next, in order to confirm the effect of this embodiment, the same experiment as in Example 1 was carried out. In this experiment, in addition to the above-mentioned Comparative Example and Example 1, as Example 2, the presence or absence of roller stains was confirmed using the developing apparatus of the second embodiment. The results are shown in Table 2 below.

As is clear from Table 2, in Example 2, the roller stain was even lighter than in Example 1. From the above, it was found that the toner scattering can be further suppressed by making the gap between the photosensitive drum 1A and the end ribs 49a and 49b substantially zero.

<Third embodiment>
The third embodiment will be described with reference to FIGS. 10 (a) and 10 (b). In the first embodiment described above, the inflow opening 50 is formed only on the end rib 49a side. On the other hand, in the present embodiment, the inflow opening 50 is also formed in the end rib 49b. Since other configurations and operations are the same as those of the first embodiment described above, the same reference numerals are given to the same configurations, and the description and illustration are omitted or simplified. I will explain mainly.

In the present embodiment, as shown in FIG. 10A, an inflow opening 50 similar to that in the first embodiment is formed in the end rib 49a on the front side in the longitudinal direction. Further, as shown in FIG. 10B, an inflow opening 50 is also formed in the end rib 49b on the back side in the longitudinal direction. That is, the inflow opening 50 is formed in both the end ribs 49a and 49b, respectively. The inflow opening 50 formed in the end rib 49b has the same position and shape in the rotational direction as the inflow opening 50 formed in the end rib 49a. That is, the same inflow opening 50 as in the first embodiment is also formed on the end rib 49b.

The inflow openings 50 on both sides are open to the photosensitive drum 1A side, respectively. Therefore, when the developing sleeve 44a is assembled to the developing container 41, the rotating shaft 44c of the developing sleeve 44a can pass through the inflow opening 50. The end rib 49b is formed with a suction opening 51 as in the first embodiment.

In the case of the present embodiment, the end rib 49b acts as an inflow portion of the airflow into the airflow space 52, and a new airflow is generated. Therefore, even in the configuration of the present embodiment, the toner scattered from the developing sleeve 44a can be sufficiently sucked.

[Example 3]
Next, in order to confirm the effect of this embodiment, the same experiment as in Example 1 was carried out. In this experiment, in addition to the above-mentioned Comparative Examples and Examples 1 and 2, the presence or absence of roller stains was confirmed as Example 3 using the developing apparatus of the third embodiment. The results are shown in Table 3 below.

As is clear from Table 3, in Example 3, the roller stain was as slight as in Example 1. From the above, it was found that the scattered toner can be suppressed even if the inflow opening 50 is also provided in the end rib 49b.

<Other embodiments>
In the third embodiment described above, similarly to the second embodiment, elastic members may be provided on the end ribs 49a and 49b so that the elastic members are brought into contact with the photosensitive drum 1A.

In each of the above-described embodiments, as a developing apparatus, a developer is supplied from the second developer transport path (first chamber) 45b to the developing sleeve (developer carrier) 44a, and the first developer transport path (first room). The configuration for recovering the developer from the developing sleeve 44a in the two chambers) 45a has been described. However, the developer may be supplied from the first chamber to the developer carrier, and the developer may be recovered from the developer carrier in the first chamber. In addition to the configuration in which the first chamber and the second chamber are arranged vertically, the developing apparatus has a configuration in which the first chamber and the second chamber are arranged so as to be adjacent in the horizontal direction or in a direction inclined in the horizontal direction. There may be.

The image forming apparatus of the present invention can be applied to a copying machine, a printer, a facsimile, a multifunction device having a plurality of these functions, and the like.

1A, 1B, 1C, 1D ... Photosensitive drum (image carrier) / 4A, 4B, 4C, 4D ... Developing device / 41 ... Developing container / 41a ... Upstream end / 44a ... Development sleeve (developer carrier) / 48 ... projecting portion / 49a ... end rib (first end protruding portion) / 49b ... end rib (second end protruding portion) / 50 ... Inflow opening (first opening) / 51 ... Suction opening (second opening) / 53 ... Duct / 54a, 54b ... Elastic member / 60 ... Suction Fan (airflow generating means) / 100 ... image forming apparatus / M ... first region / N ... second region / P ... closest position

Claims (10)

With a rotating image carrier,
The developing container capable of accommodating the developing agent and the developing container are arranged so as to face the image carrier, and by rotating, the developing agent in the developing container is supported and conveyed to the region facing the image carrier, and the image is conveyed. A developing apparatus having a developer carrier for developing an electrostatic latent image on the carrier, and
Equipped with an airflow generating means to generate an airflow,
The developing container is
Arranged in the longitudinal direction of the developing container intersecting the rotation direction of the developing agent carrier, downstream of the closest position between the developing agent carrier and the image supporting body in the rotation direction of the developing agent carrier. And a protruding portion formed so as to project toward the image carrier so as to have a gap between the image carrier and the image carrier.
It is arranged at both ends of the developing container in the longitudinal direction from at least the closest position to the projecting portion, and projects toward the image carrier so as to have a gap between the developing container and the image carrier. It has a first end protrusion and a second end protrusion, which are formed so as to:
An airflow space in which airflow can flow in a space surrounded by the image carrier, the developer carrier, the protrusion, the first end protrusion, and the second end protrusion. When
At least the first end protrusion of the first end protrusion and the second end protrusion is in close contact with the developing container in the direction of rotation of the developer carrier. A first opening is formed downstream of the position and further upstream of the upstream end of the portion facing the developer carrier so that airflow can flow into the airflow space from the outside of the developing container.
A second opening capable of sucking airflow from the airflow space by the airflow generated by the airflow generating means is formed in the second end protruding portion.
An image forming apparatus characterized in that. The developer carrier has a first region corresponding to a maximum image region on which an image can be formed on the image carrier in the longitudinal direction, and a region deviated from the maximum image region at both ends of the first region. Has a second region corresponding to
The image forming apparatus according to claim 1, wherein the image forming apparatus is characterized in that. The first opening is formed so that the developer supported on the developer carrier opens to the upstream side of the portion in contact with the image carrier in the rotation direction of the developer carrier.
The image forming apparatus according to claim 1 or 2, wherein the image forming apparatus is characterized in that. The second opening is formed so as to open within the range of the airflow space when viewed from the longitudinal direction.
The image forming apparatus according to any one of claims 1 to 3, wherein the image forming apparatus is characterized in that. A duct for connecting the airflow generating means and the second opening is provided.
The image forming apparatus according to any one of claims 1 to 4, wherein the image forming apparatus is characterized in that. The first opening is formed so as to open toward the image carrier side.
The image forming apparatus according to any one of claims 1 to 5, wherein the image forming apparatus is characterized in that. The first opening is formed in both the first end protrusion and the second end protrusion, respectively.
The image forming apparatus according to any one of claims 1 to 6, wherein the image forming apparatus is characterized in that. Each of the first end protrusion and the second end protrusion is provided with an elastic member provided so as to be in elastic contact with the image carrier.
The image forming apparatus according to any one of claims 1 to 7, wherein the image forming apparatus is characterized in that. The elastic member is provided downstream of the first opening in the rotational direction of the developer carrier.
The image forming apparatus according to claim 8. The protrusion is provided below the closest position in the direction of gravity.
The image forming apparatus according to any one of claims 1 to 9, wherein the image forming apparatus is characterized in that.

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