JP7830188B2 - Image forming apparatus - Google Patents

Description

This invention relates to image forming apparatus such as photocopiers, printers, facsimile machines, and multifunction devices that have multiple functions of these.

In image forming apparatuses, an electrostatic latent image formed on an image carrier such as a photosensitive drum by a developer carrier such as a developing sleeve is developed with toner to form a toner image. Conventionally, in such image forming apparatuses, the density of the toner image formed on the image carrier is detected by a sensor (detection means) and the toner density is adjusted accordingly. Because this sensor is located opposite the image carrier and close to the developer carrier, the sensor's detection surface is prone to adhesion of developer containing toner scattered from the image carrier and developer carrier. Therefore, a configuration has been proposed (Patent Document 1) that uses a duct with an opening near the sensor to draw in air around the sensor and suppress developer adhesion to the sensor.

Japanese Patent Publication No. 2011-232680

However, in the configuration described in Patent Document 1, since the opening for air intake is located near the sensor, it is difficult to draw in air from areas far from this opening, and the effect of suppressing contamination by the developer in this area is small. In particular, in a developing apparatus, the developer is transported by a transport member within the developing container, and depending on the configuration of the developing apparatus, the amount of developer may increase downstream in the transport direction of this transport member. And in such areas where the amount of developer is high, there is a tendency for the amount of developer to scatter outside the developing apparatus to increase.

Furthermore, while some developing devices have end covers to conceal the ends of the developer carrier to prevent leakage from those ends, even with such a configuration, developer may still leak from the center of the end cover. In any case, if developer spills from the developing device and accumulates near the device, it may cause image defects.

The present invention aims to provide a configuration that allows for efficient aspiration of developer from areas distant from the detection means while suppressing the adhesion of developer to the detection means.

The present invention provides an image forming apparatus comprising: an image carrier that carries and rotates a toner image; a developing container that contains a developer containing toner; a transport member that transports the developer within the developing container; a developer carrier whose rotation axis direction is arranged substantially parallel to the direction of transport of the developer by the transport member, which carries the developer in the developing container and rotates to transport the developer to a developing region opposite the image carrier, and develops the electrostatic latent image formed on the image carrier with toner; and an end cover provided on the developing container so as to cover the surface of one end of the developer carrier that faces the image carrier with respect to the rotation axis direction of the developer carrier; and the image carrier The device comprises: a detection means positioned opposite the image carrier downstream of the development region with respect to the rotation direction of the body, for detecting the density of the toner image on the image carrier; a first opening for drawing in air from the space enclosed by the image carrier, the development device, and the detection means; and a second opening provided on one end side of the first opening with respect to the rotation axis direction of the developer carrier; and a duct for discharging the air drawn in from the first and second openings. The opening end on the other end side of the second opening is positioned on the other end side of the end cover with respect to the rotation axis direction of the developer carrier.

According to the present invention, it is possible to efficiently aspirate developer from an area distant from the detection means while suppressing the adhesion of developer to the detection means.

A schematic cross-sectional view of the image forming apparatus according to the first embodiment. A schematic side view of the image forming unit according to the first embodiment. A schematic longitudinal cross-sectional view of the developing apparatus according to the first embodiment. A perspective view of the developing apparatus according to the first embodiment, as seen from the developing sleeve side. An enlarged cross-sectional view of the area around the concentration sensor according to the first embodiment. A perspective view showing an enlarged view of the area around the concentration sensor and suction duct according to the first embodiment. A flowchart showing an example of controlling the setting of image formation conditions by density detection according to the first embodiment. A control block diagram of the main part of an image forming apparatus according to the first embodiment. A front view showing an enlarged view of the area around the concentration sensor and suction duct according to the first embodiment. An enlarged cross-sectional view of the area around the second opening according to the first embodiment. An enlarged cross-sectional view of the area around the second opening according to the second embodiment. A perspective view showing an enlarged view of the area around the concentration sensor and suction duct according to the third embodiment. An enlarged cross-sectional view of the area around the second opening according to the third embodiment.

<First Embodiment>
The first embodiment will be described with reference to Figures 1 to 10. First, the schematic configuration of the image forming apparatus of this embodiment will be described with reference to Figure 1.

[Image forming apparatus]
The image forming apparatus 200 shown in Figure 1 is an electrophotographic full-color laser printer. The image forming apparatus 200 uses first, second, third, and fourth image forming units Py, Pm, Pc, and Pb, which are arranged side by side inside the apparatus, to form toner images of four different colors through the processes of charging, exposure, development, and transfer. As a control means, the control unit 19 consists of a CPU and memory such as ROM or RAM. When the control unit 19 receives a print command signal output from an external interface such as a host computer, it sequentially operates the image forming units Py, Pm, Pc, and Pb according to the image forming control sequence stored in the memory. The image forming apparatus 200 also includes an operation panel 22 as an operation unit. The operation panel 22 allows various settings of the image forming apparatus 200 and displays the status of the image forming apparatus 200.

In each image forming section Py, Pm, Pc, and Pb, the photosensitive drum 1, acting as the image carrier, is rotated at a predetermined peripheral speed (process speed). Furthermore, an intermediate transfer belt 7, acting as an intermediate transfer body, is positioned across the photosensitive drums 1 of each image forming section Py, Pm, Pc, and Pb. The intermediate transfer belt 7 is stretched across a drive roller 6a, a driven roller 6b, and a tension roller 6c, and is rotated by the drive roller 6a at a peripheral speed corresponding to the rotational peripheral speed of each photosensitive drum 1.

In the first color, yellow, image forming section Py, the outer surface (surface) of the photosensitive drum 1 is uniformly charged to a predetermined polarity and potential by the charger 2. Next, the exposure device 3 scans and exposes the charged surface of the photosensitive drum 1 with laser light generated based on image information from an external device. This forms an electrostatic latent image on the charged surface of the photosensitive drum 1 corresponding to the image information. This latent image is then developed by the developing device 4 using yellow toner (developer), forming a yellow toner image (developed) on the surface of the photosensitive drum 1. Similar charging, exposure, and development processes are performed in the second color, magenta, image forming section Pm, the third color, cyan, image forming section Pc, and the fourth color, black, image forming section Pb. Toner is supplied to each color's developing device 4 from toner bottles 20y, 20m, 20c, and 20b via toner supply devices 21y, 21m, 21c, and 21b.

In each image forming section Py, Pm, Pc, and Pb, the toner images of each color formed on the surface of the photosensitive drum 1 are sequentially transferred onto the outer surface (surface) of the intermediate transfer belt 7 by primary transfer rollers (transfer members) 8, which are positioned opposite the photosensitive drum 1 across the intermediate transfer belt 7. This forms a full-color toner image on the surface of the intermediate transfer belt 7. After the toner image transfer, any remaining toner residue on the surface of the photosensitive drum 1 is removed by the drum cleaner 5, and the drum is then used for the next image formation.

Meanwhile, the recording material P is transported from the feeding cassette 10 through the transport path 12a to the register roller 13 by the delivery roller 11. Next, the recording material P is transported by the register roller 13 to the secondary transfer nip section Tn between the intermediate transfer belt 7 and the secondary transfer roller 14. At this secondary transfer nip section Tn, the recording material P is gripped and transported, and during this transport process, the toner image on the surface of the intermediate transfer belt 7 is transferred onto the recording material P by the secondary transfer roller 14. After the toner image transfer, the intermediate transfer belt 7 is cleaned of any remaining toner residue on its surface by the belt cleaner 9 and then used for the next image formation.

The recording material P, which carries the unfixed toner image, is introduced into the nip section of the fixing device 15 with the image-bearing surface facing upwards. The recording material P is then clamped and transported by the nip section of the fixing device 15, thereby heating and fixing the toner image onto the recording material P. When forming an image on only one side of the recording material P, the recording material P discharged from the fixing device 15 is passed through the discharge roller 17 by the switching member 16 and discharged onto the discharge tray 18 located on the side of the image forming apparatus 200. An exhaust fan 213 is provided near the fixing device 15 to exhaust air from the vicinity of the fixing device 15 and inside the image forming apparatus 200.

When forming an image on both sides of the recording material P, the recording material P discharged from the fixing device 15 is guided by the switching member 16 to the lower inversion transport path 12b. In the inversion transport path 12b, when the rear end of the recording material P reaches the inversion point Rp, the recording material P is switched back and sent to the double-sided transport path 12c with the image-bearing surface facing upwards. In the double-sided transport path 12c, the recording material P is transported to the register roller 13 via the transport path 12a. This recording material P is then transported by the register roller 13 to the secondary transfer nip section Tn, where it is clamped and transported. During this transport process, the toner on the surface of the intermediate transfer belt 7 is transferred onto the recording material P by the secondary transfer roller 14. The recording material P carrying the unfixed toner image is introduced into the nip section of the fixing device 15 with the image-bearing surface facing upwards. Then, the recording material P is held and transported by the nip section of the fixing device 15, and the toner image is heated and fixed onto the recording material P. The recording material P discharged from the fixing device 15 is then discharged onto the discharge tray 18 via the discharge roller 17 by the switching member 16.

[Image Forming Unit]
Figure 2 shows a cross-sectional view of the schematic configuration of the image forming unit Py in this embodiment. Since the configuration of the image forming unit for each color is the same, the following description will only refer to the image forming unit Py, and the descriptions of the other image forming units will be omitted. The image forming unit Py consists of a charger 2, a developing device 4, a sensor unit 100, and a drum cleaner 5 arranged around the photosensitive drum 1. In this embodiment, the charger 2 is a corona charger positioned close to the surface of the photosensitive drum 1, and uniformly charges the surface of the photosensitive drum 1 as described above. The charger 2 may also be a charging roller positioned in contact with or close to the photosensitive drum 1. The drum cleaner 5 has a cleaning blade 51 that contacts the surface of the photosensitive drum 1, and the cleaning blade 51 removes toner remaining on the surface of the photosensitive drum 1 after transfer.

The developing apparatus 4 comprises a developing container 401, a first transport screw 404 and a second transport screw 406 as transport members, a developing sleeve 402 as a developer carrier, an end cover 411 (see Figure 4), and the like. The developing container 401 contains a developer including toner. In this embodiment, it contains a developer containing non-magnetic toner and a magnetic carrier. The first transport screw 404 and the second transport screw 406 transport the developer within the developing container 401. The developing sleeve 402 is positioned so that its rotational axis is approximately parallel to the direction of developer transport by the second transport screw 406. By carrying the developer in the developing container 401 and rotating, it transports the developer to the developing area facing the photosensitive drum 1, and develops the electrostatic latent image formed on the photosensitive drum 1 with the toner. The end cover 411 covers the surface of one end of the developing sleeve 402 that faces the photosensitive drum 1, with respect to the rotational axis direction. A detailed explanation follows.

The developing container 401, acting as a casing, has an opening positioned opposite the photosensitive drum 1, and rotatably supports the developing sleeve 402 near this opening. Furthermore, within the developing container 401, a first stirring chamber 403 and a second stirring chamber 405 are provided, positioned opposite the developing sleeve 402 and parallel to the rotation axis of the developing sleeve 402. A first transport screw 404 and a second transport screw 406, respectively, stir and transport the developer inside the developing container 401 in a direction parallel to the rotation axis of the developing sleeve 402. Additionally, an stirring screw 407 may be placed in the first stirring chamber 403 to assist in stirring the developer recovered from the developing sleeve 402.

Specifically, the developing container 401 has a second stirring chamber 405 as a supply chamber for supplying developer to the developing sleeve 402, a first stirring chamber 403 as a recovery chamber for recovering developer from the developing sleeve 402 by forming a developer circulation path between it and the second stirring chamber 405, and a partition wall 401a separating the second stirring chamber 405 and the first stirring chamber 403. Furthermore, the developing device 4 has a second transport screw 406 as a supply-side transport member for transporting developer in a first direction in the second stirring chamber 405, and a first transport screw 404 as a recovery-side transport member for transporting developer in a second direction opposite to the first direction in the first stirring chamber 403.

In this embodiment, the second stirring chamber 405 is positioned above the first stirring chamber 403 via a partition wall 401a. The partition wall 401a is positioned substantially horizontally along the rotation axis direction (longitudinal direction) of the developing sleeve 402. A first communication opening 408 and a second communication opening 409 are formed at both longitudinal ends of the partition wall 401a, allowing the developer to move between the first stirring chamber 403 and the second stirring chamber 405 (Figure 3).

Figure 3 schematically shows cross-sections of the first agitation chamber 403 and the second agitation chamber 405 of the developing apparatus 4 in a direction parallel to the developer transport direction. As shown in Figure 3, the first transport screw 404 and the second transport screw 406 transport the developer in opposite directions as indicated by the arrows, and the developer is circulated in the developing container 401 by transferring it through the first communication port 408 and the second communication port 409 provided near the ends of each agitation chamber.

In the first stirring chamber 403, the developer recovered from the developing sleeve 402 and the developer newly supplied to the developing device 4 via the supply port 410 are stirred and transported by the first transport screw 404. Toner is supplied to the supply port 410 from the toner bottle 20y via the toner supply device 21y (Figure 1).

In the second stirring chamber 405, the developer received from the first stirring chamber 403 is supplied to the developing sleeve 402 by the second transport screw 406 while being transported. The transfer of developer from the first stirring chamber 403 to the second stirring chamber 405 occurs when the developer that hits the downstream end of the first stirring chamber in the direction of transport is pushed by the first transport screw 404, thereby sending the developer from the first stirring chamber 403 to the first communication port 408. Therefore, in the first stirring chamber 403, the amount of developer tends to be greater on the downstream side in the direction of transport of the first transport screw 404.

Furthermore, in the second stirring chamber 405, the developer is carried by the second transport screw 406 in the direction of the rotation axis of the developing sleeve 402. Since the developing sleeve 402 carries the developer on its surface and transports it in the direction of its rotation, the amount of developer in the second stirring chamber 405 decreases towards the downstream side in the transport direction of the second transport screw 406.

As a result, the amount of developer 414 circulating within the developing container 401 is not uniform in the longitudinal direction, and the distribution of the amount of developer 414 is as shown in Figure 4. Specifically, the amount of developer tends to be higher in the first stirring chamber 403 downstream of the first conveying screw 404, and higher in the second stirring chamber 405 upstream of the second conveying screw 406. In particular, the downstream side of the first stirring chamber 403 in the developer conveying direction has a higher amount of developer in the stirring chamber, and because it is downstream in the developer conveying direction, the conveying force from the first conveying screw increases the pressure of the developer in the stirring chamber. Therefore, the resistance when the developer carried on the surface of the developing sleeve 402 enters the first stirring chamber 403 is greater than on the upstream side, and the developer that does not enter the first stirring chamber 403 tends to scatter outside the developing device 4.

Figure 4 shows a perspective view of the developing apparatus 4 of this embodiment. Between the end of the developing sleeve 402 and the developing container 401, a sealing member (not shown) is placed along the surface of the end of the developing sleeve 402 to prevent the developer from leaking out. However, on the downstream side of the first conveying screw 404 in the first stirring chamber 403 in the developer conveying direction, the pressure of the developer inside increases, which may cause the developer to leak beyond the seal. Therefore, an end cover 411 is provided on the outside of the developing container 401 at the end of the developing sleeve 402 to suppress the leakage of the developer from the developing apparatus 4.

The end cover 411 is positioned to cover the area outside the developer-carrying region of the developing sleeve 402 with respect to the rotational axis direction of the developing sleeve 402. The developer-carrying region is, for example, an area on the surface of the developing sleeve 402 where irregularities are formed to carry the developer. These irregularities are formed, for example, by a blasting process. The end cover 411 is positioned on the end area of the surface of the developing sleeve 402 where such irregularities are not formed. Furthermore, the end cover 411 is provided on the developing container 401 so as to cover the surface of the end of the developing sleeve 402 that faces the photosensitive drum 1. In addition, the end cover 411 has a projection 411a that protrudes further toward the center in the rotational axis direction of the developing sleeve 402 than the portion covering the developing sleeve 402, on the downstream side of the developing sleeve 402 with respect to the rotational direction of the photosensitive drum 1. In this embodiment, end covers 411 are positioned at both ends of the developing sleeve 402. However, the end cover 411 located on the downstream end side (one end side with respect to the rotation axis direction of the developing sleeve 402) in the developer transport direction (second direction) of the first transport screw 404 is more effective in suppressing developer leakage.

The sensor unit 100 includes a density detection sensor 101 as a detection means. The density detection sensor 101 is positioned opposite the photosensitive drum 1 on the downstream side of the development area with respect to the rotation direction of the photosensitive drum 1, and detects the density of the toner image on the photosensitive drum 1 (on the image carrier). In this embodiment, the sensor unit 100 is positioned at the bottom of the development device 4 in the direction of gravity. The density detection sensor 101 of the sensor unit 100 has a detection unit 102 that emits and receives light, and the detection unit 102 faces the photosensitive drum 1. Such a density detection sensor 101 is an optical sensor that detects the density of the toner image by emitting light toward the toner image on the photosensitive drum 1 and receiving reflected light.

Figure 5 shows a cross-sectional view of the vicinity of the sensor unit 100, and Figure 6 shows a perspective view of the vicinity of the sensor unit 100. The sensor unit 100 consists of a density detection sensor 101 and a sensor holder 105 formed by an upper cover 103 and a lower cover 104 that cover the density detection sensor 101. The sensor unit 100 is positioned so that the detection unit 102 of the density detection sensor 101 faces the photosensitive drum 1 through a detection window 106 provided in the sensor holder 105, in order to detect the density of the patch image, which is a control toner image formed on the photosensitive drum 1.

Figure 7 shows a flowchart of the density detection process in this embodiment, and Figure 8 shows a block diagram. When the timing for density detection of the patch image is reached (YES in S1), the control unit 19 forms a patch image on the photosensitive drum 1 (S2). Next, the density detection sensor 101 reads the patch image (S3). That is, it detects the density of the patch image. Then, the control unit 19 sets the image formation conditions based on the detected density (S4). For example, it changes the conditions of at least one of the following: the charger 2, the exposure device 3, the developing device 4, etc.

These components have similar arrangements in each image forming unit (Py, Pm, Pc, Pb). Each developing device 4 forms patch images of each color on the photosensitive drum 1. These are detected by density detection sensors 101 located at each station, and based on these detection results, optimal image forming conditions are set for each image forming unit (Py, Pm, Pc, Pb).

During the density detection process described above, if the detection unit 102 becomes contaminated with developer, the detection unit 102 may mistakenly recognize the developer adhering to it as part of the patch image on the photosensitive drum 1, potentially preventing accurate density detection. Therefore, in this embodiment, a duct 110 is provided for suctioning scattered developer, and as shown in Figure 7, a first suction port (first opening) 107 is positioned near the density detection sensor 101 to reduce the amount of developer scattered onto the detection unit 102 and suppress contamination of the detection unit 102.

[Air intake configuration]
Figure 9 shows a view of the vicinity of the suction port of the air suction configuration in this embodiment, as seen from the central axis side of the photosensitive drum 1. The duct 110 has a first suction port 107 as a first opening for drawing in air from the space surrounded by the photosensitive drum 1, the developing device 4, and the density detection sensor 101, and a second suction port 111 as a second opening provided at one end (right side in Figure 9) of the developing sleeve 402 with respect to the rotation axis direction, and discharges the air drawn in from the first suction port 107 and the second suction port 111.

Specifically, as shown in Figure 9, a first suction port 107 is located on the longitudinal rear side of the photosensitive drum 1 of the sensor holder 105 (one end side with respect to the rotation axis direction of the developing sleeve 402). The first suction port 107 is positioned at approximately the same height as the sensor holder 105 and primarily draws in air from the upper surface of the sensor holder 105. The airflow drawn in from the first suction port 107 is guided to the duct 110 and passes through the duct 110 in the direction of the airflow 124.

A second suction port 111 is provided on the upper surface of the duct 110 near the end of the developing sleeve 402, in the region downstream of the airflow from the first suction port 107 where a relatively large amount of developer is scattered in the developing apparatus 4. This region is located downstream of the first transport screw 404 in the transport direction (to the right in Figure 9, towards one end with respect to the rotation axis direction of the developing sleeve 402).

The second suction port 111 is positioned in the duct 110 downstream of the first suction port 107 in the direction of airflow. Therefore, its opening area is set to be smaller than that of the first suction port 107. That is, the opening area of the first suction port 107 is larger than that of the second suction port 111. This configuration allows for suction of areas where a relatively large amount of developer is scattered by the second suction port 111, without impairing the function of the first suction port 107 in maintaining the detection accuracy of the concentration detection sensor 101.

Regarding the rotational axis direction of the developing sleeve 402, the positions of the opening ends 114 and 115 of the second suction port 111 are set as follows. First, regarding the rotational axis direction of the developing sleeve 402, the opening end 115 located on one end side (right side in Figure 9) of the second suction port 111 is set to approximately the same position as the end 412 located on the center side (other end side, left side in Figure 9) of the developing sleeve 402 in the rotational axis direction of the end cover 411 that covers the end of the developing sleeve 402 on one end side. This end 412 is the central end of the protruding portion 411a, which is also the part of the end cover 411 closest to the duct 110.

On the other hand, with respect to the rotational axis direction of the developing sleeve 402, the opening end 114 on the other end side (left side in Figure 9) of the second suction port 111 is located closer to the other end than the other end 412 of the end cover 411. That is, the opening end 114 is located closer to the axial center of the developing sleeve 402 than the end 412 of the end cover 411. In this embodiment, the distance between the end 412 of the end cover 411 and the opening end 114 on the other end side of the second suction port 111 is set to 8 mm. However, the distance is not limited to this; a distance of about 10 mm is acceptable. That is, with respect to the rotational axis direction of the developing sleeve 402, it is preferable that the opening end 114 on the other end side of the second suction port 111 is located within 10 mm of the other end of the end cover 411.

Next, the position of the opening end of the second suction port 111 in a direction perpendicular to the rotation axis direction of the developing sleeve 402 will be described. Figure 10 shows a cross-section of the second suction port 111 perpendicular to the rotation axis direction of the developing sleeve 402. The opening end of the second suction port 111 in a direction perpendicular to the rotation axis direction of the developing sleeve 402 is set so that it is included within the projection plane obtained by projecting the developing sleeve 402 toward the direction of the second suction port 111, i.e., the direction of gravity. That is, the second suction port 111 is positioned below the developing sleeve 402 in the direction of gravity and opens so as to face the developing sleeve 402, and at least a part of the second suction port 111 is included within the projection plane obtained by projecting the developing sleeve 402 toward the direction of gravity. In this embodiment, the second suction port 111 is formed so that the entirety of the second suction port 111 is included within this projection plane.

As described above, by setting the first suction port 107 and the second suction port 111, the air in the space formed in the direction of the rotation axis of the photosensitive drum 1 between the developing device 4, the sensor holder 105, and the photosensitive drum 1 is drawn into the duct 110 by airflows 120 and 121 drawn from the first suction port 107 and airflows 122 and 123 drawn from the second suction port 111, as shown in Figure 9.

Furthermore, as described above, the open end 114 on the other end of the second suction port 111 is located on the other end side (towards the center in the rotational axis direction of the developing sleeve 402) than the end 412 of the end cover 411 on the one end side, and opens toward the developing sleeve 402. At least a portion of this opening is included in the projection plane obtained by projecting the developing sleeve 402 toward the opening of the second suction port 111. This allows the second suction port 111 to suck up the developer even if it leaks from the end of the developing sleeve 402 beyond the end cover 411 and spills out of the developing device 4, scattering as it falls.

As a result, it is possible to efficiently aspirate developer from areas away from the density detection sensor 101 while suppressing the adhesion of developer to the density detection sensor 101. In other words, it is possible to suppress contamination of the density detection sensor 101 and the amount of developer passing between the photosensitive drum 1 and the density detection sensor 101 during density detection, thereby preventing a loss of detection accuracy of the density detection sensor 101. Furthermore, it is possible to suppress contamination of the developing device 4 and its surroundings by scattered and fallen developer on the downstream side of the rotation direction of the photosensitive drum 1 of the developing device 4.

<Second Embodiment>
A second embodiment will be described using Figure 11. In this embodiment, the position of the second suction port 111A is restricted in relation to the recovery roller 413. Since the other configurations and operations are the same as in the first embodiment, the same reference numerals are used for similar components, and their descriptions and illustrations are omitted or simplified. The following description will focus on the differences from the first embodiment.

Figure 11 shows a cross-sectional view of the second suction port 111A in this embodiment. The developing apparatus 4A in this embodiment is positioned adjacent to the developing sleeve 402 on the density detection sensor 101 side (detection means side) of the developing sleeve 402. It includes a recovery roller 413 as a recovery member for collecting the developer on the developing sleeve 402 (on the developer carrier) into the developing container 401, downstream of the developing area in the rotational direction of the developing sleeve 402. The recovery roller 413 is positioned below the developing sleeve 402 in the developing apparatus 4, adhering the developer scattered from the developing sleeve 402 to its surface and collecting it into the developing container 401. In this embodiment, the recovery roller 413 reduces the amount of developer scattered from the developing sleeve 402. By arranging it in conjunction with the air suction configuration using the duct 110, contamination by scattered developer can be further reduced.

If a recovery roller 413 is positioned in the developing device 4, and developer leaks from the end of the developing sleeve 402, some of it will adhere to the surface of the recovery roller 413 and be collected in the developing container 41. However, some may not be collected and may leak out of the developing device 4. In this case, it will fall along the surface of the recovery roller 413.

Therefore, in this embodiment, the opening end 116 of the second suction port 111A on the photosensitive drum 1 side (image carrier side) is positioned closer to the photosensitive drum 1 than the closest contact position of the recovery roller 413 with respect to the photosensitive drum 1. That is, in this embodiment as well, at least a portion of the second suction port 111A is set to be included within the projection plane obtained by projecting the development sleeve 402 in the direction perpendicular to the rotation axis direction of the development sleeve 402. In addition, in this embodiment, the opening end 116 of the second suction port 111A on the photosensitive drum 1 side is positioned closer to the photosensitive drum 1 than the surface of the recovery roller 413 that is closest to the photosensitive drum 1.

In this embodiment, the opening end 116 of the second suction port 111A on the photosensitive drum 1 side is positioned 2 mm toward the photosensitive drum 1 side relative to the surface of the recovery roller 413. However, the distance is not limited to this; the opening end 116 of the second suction port 111A on the photosensitive drum 1 side only needs to be on the photosensitive drum 1 side relative to the surface of the recovery roller 413.

In this embodiment, by making the second suction port 111A such an opening shape, the developer that has dripped down the surface of the recovery roller 413 can be directly collected by the opening of the second suction port 111A. This suppresses contamination of the developing device 4 and its surroundings by scattered and dripped developer.

<Third Embodiment>
A third embodiment will be described with reference to Figures 12 and 13. In this embodiment, a rib 112 is provided on the duct 110 so as to separate the second suction port 111B from the photosensitive drum 1. The other configurations and operations are the same as in the second embodiment, so the same components are denoted by the same reference numerals, and their description and illustration are omitted or simplified. The following description will focus on the differences from the second embodiment. The developing apparatus 4A of this embodiment also includes a recovery roller 413, similar to the second embodiment. Note that the configuration of this embodiment can also be applied to the configuration of the first embodiment, which does not include a recovery roller 413.

Figure 12 shows a perspective view of the vicinity of the second suction port 111B in this embodiment, and Figure 13 shows a cross-sectional view of the second suction port 111B. A feature of this embodiment is that a rib 112 is positioned between the opening end 116 on the photosensitive drum 1 side of the opening of the second suction port 111B in a direction perpendicular to the rotation axis direction of the developing sleeve 402, and the photosensitive drum 1. That is, the duct 110 has a rib 112 as a protruding portion that extends upward from the photosensitive drum 1 side of the opening end 116 on the photosensitive drum 1 side of the second suction port 111B, thereby separating the second suction port 111B from the photosensitive drum 1. In this embodiment, as shown in Figure 12, the rib 112 is provided to cover the area from the other end of the opening of the second suction port 111B to below the end cover 411, with respect to the rotation axis direction of the developing sleeve 402.

By arranging the ribs 112 in this manner, if the direction of fall of the developer leaking from the developing device 4 has a velocity component in the direction of the photosensitive drum, the falling developer will come into contact with the ribs 112, canceling out the velocity in the direction of the photosensitive drum and allowing it to fall towards the vicinity of the second suction port 111B.

Furthermore, in this embodiment, as shown in Figure 13, a portion of the rib 112 on the developing sleeve 402 side (developer carrier side) is an inclined surface 113 that slopes downward as it moves away from the photosensitive drum 1. That is, the tip of the rib 112 is provided with an inclined surface 113 that slopes toward the second suction port 111B. In this embodiment, the tip surface of the rib 112 is the inclined surface 113. By providing this inclined surface 113, the developer that falls near the tip of the rib 112 is prevented from accumulating on the tip of the rib 112, allowing it to be guided toward the second suction port 111B, making it easier to collect at the second suction port 111B.

In this embodiment, by providing a rib 112 on the duct 110 and creating an inclined surface 113 near its tip, it becomes easier to collect the developer leaking from the developing device 4A. This makes it possible to suppress contamination by scattered and fallen developer in the developing device 4A and its surroundings on the downstream side of the photosensitive drum 1 in the direction of rotation.

[Other embodiments]
Furthermore, the present invention is not limited to the image forming apparatus of the above embodiment. The image forming apparatus can be a tandem type or a single-drum type, an intermediate transfer type or a direct transfer type, without distinction. In addition, the present invention is not limited to the developing apparatus of the above embodiment, and can be implemented in a developing apparatus equipped with, for example, two developer carriers.

1... Photosensitive drum (image carrier)
4, 4A... Developing device 101... Density detection sensor (detection means)
107... First suction port (first opening)
110... Duct 111, 111A, 111B... Second suction port (second opening)
112... Rib (protruding part)
113... Inclined surface 114... Open end 116... Open end 200... Image forming apparatus 401... Developing container 402... Developing sleeve (developer carrier)
403...First stirring chamber (recovery chamber)
404...First conveying screw (conveying member, recovery side conveying member)
405...Second stirring chamber (supply chamber)
406... Second conveying screw (supply-side conveying member)
411... End cover 412... End 413... Recovery roller (recovery member)

Claims (8)

An image carrier that holds the toner image and rotates,
A developing apparatus comprising: a developing container for containing a developer containing toner; a transport member for transporting the developer within the developing container; a developer carrier whose rotation axis direction is arranged substantially parallel to the direction of transport of the developer by the transport member, which carries the developer in the developing container and rotates to transport the developer to a developing region facing the image carrier, and develops the electrostatic latent image formed on the image carrier with toner; and an end cover provided on the developing container so as to cover the surface of one end of the developer carrier that faces the image carrier with respect to the rotation axis direction,
A detection means is positioned opposite the image carrier downstream of the developing region with respect to the rotation direction of the image carrier, and detects the density of the toner image on the image carrier.
The device has a first opening for drawing in air from the space enclosed by the image carrier, the developing apparatus, and the detection means, and a second opening provided on one end side of the first opening with respect to the rotation axis direction of the developer carrier, and a duct for discharging the air drawn in from the first opening and the second opening.
An image forming apparatus characterized in that, with respect to the rotation axis direction of the developer carrier, the other end of the second opening is located on the other end side of the other end of the end cover. The image forming apparatus according to claim 1, characterized in that the opening area of the first opening is larger than the opening area of the second opening. The image forming apparatus according to claim 1 or 2, characterized in that the second opening is positioned below the developer carrier in the direction of gravity, opens so as to face the developer carrier, and at least a portion of the second opening is included in the projection plane obtained by projecting the developer carrier in the direction of gravity. A recovery member is provided adjacent to the developer carrier on the detection means side of the developer carrier, and is located downstream of the developing region with respect to the rotational direction of the developer carrier, for recovering the developer on the developer carrier into the developing container.
The image forming apparatus according to any one of claims 1 to 3, characterized in that the opening end of the second opening on the image carrier side is located closer to the image carrier than the nearest position of the recovery member with respect to the image carrier. The second opening is positioned below the developer carrier in the direction of gravity and is open so as to face the developer carrier.
The image forming apparatus according to any one of claims 1 to 4, characterized in that the duct has a protruding portion that protrudes upward from the image carrier side of the opening end of the second opening on the image carrier side, so as to partition the space between the second opening and the image carrier. The image forming apparatus according to claim 5, characterized in that a portion of the protruding part on the developer carrier side is an inclined surface that slopes downward as it moves away from the image carrier. The image forming apparatus according to any one of claims 1 to 6, characterized in that, with respect to the rotation axis direction of the developer carrier, the other end of the second opening is located within 10 mm of the other end of the end cover. The developing container has a supply chamber for supplying developer to the developer carrier, a recovery chamber for recovering developer from the developer carrier by forming a developer circulation path between it and the supply chamber, and a partition wall separating the supply chamber and the recovery chamber.
The developing apparatus includes a supply-side transport member that transports the developer in a first direction in the supply chamber, and a recovery-side transport member that transports the developer in a second direction opposite to the first direction in the recovery chamber.
The image forming apparatus according to any one of claims 1 to 7, characterized in that the transporting member is the recovery-side transporting member, and one end of the developer carrier in the direction of the rotation axis is the downstream end in the second direction.