JP5113683B2 - Developing device, process cartridge, and image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus using an electrophotographic system such as a copying machine, a printer, a facsimile machine, or a multifunction machine thereof, and a developing device and a process cartridge installed therein.

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a printer, a two-component developer composed of toner and a magnetic carrier (including the case where an external additive or the like is added), or a one-component developer composed only of toner ( In many cases, a developing device that contains a case where an external additive or the like is added and performs a developing process is housed.
In such a developing device, there is a known problem that the pressure inside the device rises and toner is scattered outside the device (for example, see Patent Document 1).

In Patent Document 1, etc., the developing device is composed of a developing roller (developer carrying member), two conveying screws (first developer conveying member, second developer conveying member), doctor blade (developer regulating member), and the like. A two-component developer is accommodated in the interior.
Then, according to toner consumption in the developing device, toner is appropriately supplied into the device from a toner supply port provided at one end of the developing device. The replenished toner is mixed with the developer in the developing device while being circulated in the longitudinal direction (the same direction as the longitudinal direction of the developing roller) by the two conveying screws. A part of the mixed developer is carried on a developing roller facing a first conveying screw (first developer conveying member). After the developer carried on the developing roller is regulated to an appropriate amount by the doctor blade, the toner in the developer adheres to the latent image on the photosensitive drum at a position facing the photosensitive drum (image carrier). .

  Here, the developing device in Patent Document 1 or the like is provided with an exhaust mechanism for reducing the pressure in the device. The exhaust mechanism includes an opening (exhaust port) that opens above the case, a filter that covers the opening, a wall that is provided integrally with the case so as to cover the side of the developing roller, and the like. . The exhaust mechanism is disposed above the first conveying screw (first developer conveying member) and in the vicinity of the facing region between the first conveying screw and the developing roller.

JP 2007-148335 A

  The above-described conventional developing device cannot efficiently exhaust (depressurize) the air in the developing device, and cannot sufficiently suppress toner scattering caused by an increase in internal pressure in the developing device.

  The present invention has been made in order to solve the above-described problems. A developing device, a process cartridge, and an image forming apparatus in which air in the developing device is efficiently exhausted and toner scattering is sufficiently reduced. To provide an apparatus.

  The inventor of the present application has conducted research to solve the above problems, and as a result, the first developer transport unit (the transport unit that supplies the developer to the developer carrying member) and the second developer transport unit. In the developing device that forms a circulation path in the longitudinal direction of the developer, the height of the ceiling portion on the upstream side in the transport direction of the second developer transport portion is set to be higher than the height of the ceiling portion on the downstream side in the transport direction. And forming a relay ceiling portion whose height gradually decreases from the ceiling portion on the upstream side in the transport direction toward the ceiling portion on the downstream side in the transport direction, and providing an exhaust port and a filter on the relay ceiling portion. It has been found that the air in the apparatus is efficiently exhausted and toner scattering is sufficiently reduced.

  The present invention is based on the matters described above. That is, the developing device according to the first aspect of the present invention accommodates the developer and develops the latent image formed on the image carrier. A developing device, which is opposed to the image carrier and carries a developer, and a developer on the developer carrier while conveying the developer in a longitudinal direction by a first developer carrying member. And a first developer transport section that is disposed so as to face the first developer transport section via a partition member, and is fed from the downstream side in the transport direction of the first developer transport section. A second developer conveying section that conveys the developer in the longitudinal direction by a second developer conveying member and sends the developer to the upstream side in the conveying direction of the first developer conveying section. The height of the ceiling on the upstream side in the conveyance direction is A relay ceiling portion that is formed to be higher than the height of the ceiling portion on the downstream side and gradually decreases in height from the ceiling portion on the upstream side in the transport direction toward the ceiling portion on the downstream side in the transport direction. The relay ceiling portion includes an exhaust port that opens to the inside and outside of the apparatus, and a filter that covers the exhaust port.

  The developing device according to a second aspect of the present invention is the developing device according to the first aspect, wherein the relay ceiling portion is directed from the ceiling portion on the upstream side in the transport direction toward the ceiling portion on the downstream side in the transport direction. It is formed so as to be inclined downward.

  According to a third aspect of the present invention, there is provided the developing device according to the first or second aspect, wherein the second developer transport unit detects the toner concentration of the transported developer. A detection means is provided on the downstream side in the transport direction with respect to the relay ceiling.

  A developing device according to a fourth aspect of the present invention is the developing device according to any one of the first to third aspects, wherein the developer carrying member is installed in the first developer conveying section, The ceiling portion on the upstream side in the transport direction of the second developer transport section is disposed at a position higher than the rotation center of the developer carrier, and is disposed at a position lower than the ceiling section of the first developer transport section. It was established.

  The developing device according to a fifth aspect of the present invention is the developing device according to any one of the first to fourth aspects, wherein the exhaust port has a center position in a short direction when viewed in the longitudinal direction. The second developer conveying member is disposed so as not to overlap a virtual vertical line passing through the rotation center of the second developer conveying member.

  According to a sixth aspect of the present invention, the developing device according to any one of the first to fifth aspects is configured to be detachably installed in the longitudinal direction with respect to the image forming apparatus main body. And the said exhaust port of the said relay ceiling part is arrange | positioned so that it may open toward the attachment / detachment direction back | inner side of an apparatus.

  According to a seventh aspect of the present invention, there is provided the developing device according to any one of the first to sixth aspects, wherein the amount of the developer carried on the developer carrying member is regulated. A member is provided below the developer carrying member, and the ceiling portion on the upstream side in the transport direction, the ceiling portion on the downstream side in the transport direction, and the relay ceiling portion of the second developer transport portion include the first developer. It is configured to be detachable from the apparatus as a case integrated with the ceiling portion of the transport section.

  A process cartridge according to an eighth aspect of the present invention is a process cartridge which is detachably installed on the main body of the image forming apparatus, and the development according to any one of the first to seventh aspects. The apparatus and the image carrier are integrated.

  An image forming apparatus according to a ninth aspect of the present invention includes the developing device according to any one of the first to seventh aspects and the image carrier.

  In the present application, the “process cartridge” refers to a charging unit that charges the image carrier, a developing unit (developing device) that develops a latent image formed on the image carrier, and a cleaning on the image carrier. At least one of the cleaning units and the image carrier are defined as a unit that is integrated and detachably installed on the image forming apparatus main body.

  The present invention is a development in which a circulation path in the longitudinal direction of a developer is formed by a first developer transport unit (a transport unit that supplies developer to a developer carrying member) and a second developer transport unit. In the apparatus, the height of the ceiling portion on the upstream side in the conveyance direction of the second developer conveyance portion is formed to be higher than the height of the ceiling portion on the downstream side in the conveyance direction, and the conveyance direction from the ceiling portion on the upstream side in the conveyance direction A relay ceiling part whose height gradually decreases toward the ceiling part on the downstream side is formed, and an exhaust port and a filter are provided in the relay ceiling part. Accordingly, it is possible to provide a developing device, a process cartridge, and an image forming apparatus in which air in the developing device is efficiently exhausted and toner scattering is sufficiently reduced.

Embodiment.
Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

First, the image forming apparatus will be described in detail with reference to FIGS.
FIG. 1 is a configuration diagram illustrating a laser printer as an image forming apparatus. FIG. 2 is a cross-sectional view showing the vicinity of the process cartridge 6 installed therein. FIG. 3 is a cross-sectional view of the developing device 5 and the photosensitive drum 1 as viewed from above in the longitudinal direction (the vertical direction in FIG. 2).

  As shown in FIG. 1, process cartridges 6Y, 6M, 6C, and 6K as image forming units corresponding to the respective colors (yellow, magenta, cyan, and black) are arranged so as to face the intermediate transfer belt 8 of the intermediate transfer unit 15. It is installed side by side. Since the four process cartridges 6Y, 6M, 6C, and 6K installed in the apparatus main body 100 have substantially the same structure except that the color of the toner used in the image forming process is different, in FIGS. The alphabets (Y, M, C, K) of the reference numerals for the cartridge 6, the photosensitive drum 1, and the primary transfer bias roller 9 are omitted.

  Referring to FIG. 2, a process cartridge 6 includes a photosensitive drum 1 as an image carrier, a charging unit 4 disposed around the photosensitive drum 1, a developing device 5 (developing unit), and a cleaning unit 2. Are integrated with each other and are detachable from the apparatus main body 100. Thus, the maintainability of the image forming unit is improved by integrating the components of the image forming unit. Then, an image forming process (charging process, exposure process, developing process, transfer process, cleaning process, charge eliminating process) is performed on the photosensitive drum 1 to form a desired toner image on the photosensitive drum 1. It will be.

  In the present embodiment, the photosensitive drum 1, the charging unit 4, the developing device 5, and the cleaning unit 2 are integrated to form the process cartridge 6. However, each component is formed as a single unit in the apparatus main body 100. It can also be installed detachably. Specifically, the developing device 5 can be configured to be detachable from the apparatus main body 100 as a single unit. Further, it can be configured to be detachable from the apparatus main body 100 as a unit in which at least one of the photosensitive drum 1, the charging unit 4, and the cleaning unit 2 and the developing device 5 are integrated.

Referring to FIG. 2, the photosensitive drum 1 is rotationally driven in a clockwise direction in FIG. 2 by a drive unit (not shown). Then, the surface of the photosensitive drum 1 is uniformly charged at the position of the charging unit 4 (a charging process).
Thereafter, the surface of the photosensitive drum 1 reaches the irradiation position of the laser beam L emitted from the exposure unit 7 (see FIG. 1), and an electrostatic latent image is formed by exposure scanning at this position. (It is an exposure process.)

Thereafter, the surface of the photosensitive drum 1 reaches a position facing the developing device 5, and the electrostatic latent image is developed at this position to form a desired toner image (developing process).
Specifically, a two-component developer G composed of toner and a carrier (magnetic carrier) is accommodated in the developing device 5. The developer G in the developing device 5 is adjusted so that the toner density (the ratio of the toner in the developer G) detected by the magnetic sensor 57 as the toner density detecting means is within a predetermined range. . That is, according to toner consumption in the developing device 5, toner is replenished from the toner transport pipe 43 (toner transport unit) into the second developer transport unit 54 (second transport path) through the toner supply port 44. The The magnetic sensor 57 is a sensor that detects a change in toner density from a change in magnetic permeability of the developer flowing around the magnetic sensor 57.

Referring to FIG. 1, the toner transport pipe 43 communicates with a corresponding toner bottle among the toner bottles 32 </ b> Y, 32 </ b> M, 32 </ b> C, and 32 </ b> K installed in the bottle housing portion 31 above the apparatus main body 100. Although not shown in the figure, the toner transport unit includes a drive unit that rotationally drives the toner bottles 32Y, 32M, 32C, and 32K, a toner transport pipe 43, an air pump connected to the toner transport pipe 43, and the like. The toner transport unit configured as described above transports the respective color toners from the toner bottles 32Y, 32M, 32C, and 32K containing the respective color toners to the respective developing devices 5 through the toner transport pipe 43. .
The toner conveying unit is not limited to the above-described configuration, and various configurations can be used. For example, a configuration in which toner is supplied from the toner bottle to the developing device 5 via the relay hopper without using the toner transport pipe can be used.

  Thereafter, the toner replenished in the second developer conveying section 54 is mixed and stirred together with the developer G by the second conveying screw 56 and the first conveying screw 55, and is separated by the partition member 58. It circulates through the agent transport unit 53 (first transport path) and the second developer transport unit 54 (circulation in the direction of the broken arrow in FIG. 3).

  In detail, referring to FIG. 3, the developer G in the first developer transport section 53 (first developer accommodating section) is left on the left side of the sheet by a first transport screw 55 serving as a first developer transport member. To the right side along the longitudinal direction of the developing roller 51. On the other hand, the developer G in the second developer conveying portion 54 (second developer accommodating portion) is firstly moved from the right side to the left side of the sheet by the second conveying screw 56 as the second developer conveying member. The developer is conveyed in the opposite direction to the developer conveying unit 53.

  Further, the first developer conveying portion 53 and the second developer conveying portion 54 are separated by a partition member 58 disposed in a region excluding both ends in the longitudinal direction, and both longitudinal ends where the partition member 58 is not interposed. (The first relay unit A and the second relay unit B) communicate with each other. That is, the developer transported to the downstream side of the first developer transport unit 53 by the first transport screw 55 (first developer transport member) is transferred to the second developer transport unit 54 via the first relay unit A. The fluid flows upstream and is then transported in the longitudinal direction by the second transport screw 56 (second developer transport member). The developer transported to the downstream side of the second developer transport section 54 by the second transport screw 56 flows to the upstream side of the first developer transport section 53 via the second relay section B, and thereafter It is conveyed in the longitudinal direction by one conveying screw 55. Thus, a circulation path in the longitudinal direction of the developer is formed between the two transport paths 53 and 54.

Thus, the toner in the developer G circulating in the circulation path is attracted to the carrier by frictional charging with the carrier, and is carried on the developing roller 51 together with the carrier by a plurality of magnetic poles formed on the developing roller 51. The
Here, referring to FIG. 3, the developing roller 51 includes a magnet 51b that is fixed inside and forms a plurality of magnetic poles on the peripheral surface of the roller, and a sleeve 51a that rotates around the magnet 23a1. . Then, when the sleeve 51a rotates around the magnet 51b in which a plurality of magnetic poles are formed, the developer G moves on the developing roller 51 (on the sleeve 51a) with the rotation.

The developer G carried on the developing roller 51 as the developer carrying member is conveyed along with the rotation of the developing roller 51 in the direction of the arrow, and a doctor blade 52 (below the developing roller 51 as the developer regulating member). To the position). Then, after the developer G on the developing roller 51 is regulated to an appropriate amount at this position, the developer G is conveyed to a position facing the photosensitive drum 1 (developing area). The toner is attracted to the latent image formed on the photosensitive drum 1 by the electric field (developing electric field) formed in the developing area.
In the present embodiment, as the developing bias applied to the developing roller 51, the AC component developing bias is not applied, and only the DC component developing bias is applied. This simplifies the configuration and control of the power supply unit that supplies the developing bias, and can reduce the occurrence of a blurred image with respect to a carrier having a low resistance.

The developing roller 51 in the present embodiment is set to have an outer diameter of 18 mm and a length in the longitudinal direction of 326 mm. Further, the surface of the sleeve 51a of the developing roller 51 may be formed with V-shaped grooves at equal pitch intervals in the circumferential direction, or may be blasted.
The gap (development gap) between the developing roller 51 and the photosensitive drum 1 is set to 0.3 ± 0.05 mm, and the gap (doctor gap) between the developing roller 51 and the doctor blade 52 is 0.5 ± 0.00 mm. It is set to 04 mm. The doctor blade 52 is a plate-like member made of a stainless material.
Furthermore, each of the first conveying screw 55 and the second conveying screw 56 is formed by forming a screw portion (blade) having an outer diameter of 14 mm in a spiral shape at a pitch of 20 mm on a shaft portion having an outer diameter of 5 mm. is there.
The developing roller 51 and the doctor blade 52 are provided in the first developer conveying portion 53 together with the first conveying screw 55. Further, the second transport screw 56 and the magnetic sensor 57 are provided in the second developer transport section 54.

Although not shown, a plurality of magnetic poles are formed around the developing roller 51 (sleeve 51a) by the magnet 51b. The plurality of magnetic poles are a main magnetic pole formed at a position facing the photosensitive drum 1, a pumping magnetic pole (doctor facing magnetic pole) formed from a position facing the first conveying screw 55 to a position facing the doctor blade 52, It is composed of an agent separating magnetic pole formed above the first developer conveying portion 53, an conveying magnetic pole formed between the main magnetic pole and the agent separating magnetic pole, and the like.
First, the pumping magnetic pole acts on a carrier as a magnetic body, and a part of the developer G that moves in the first developer transport portion 53 is carried on the developing roller 51. A part of the developer G carried on the developing roller 51 is scraped off at the position of the doctor blade 52 (developer regulating member) and returned to the first developer conveying portion 53. On the other hand, the developer G carried on the developing roller 51 through the doctor gap between the doctor blade 52 and the developing roller 51 at the position of the doctor blade 52 where the magnetic force by the pumping magnetic pole acts is at the position of the main magnetic pole. It rises and becomes a magnetic brush in the developing area and comes into sliding contact with the photosensitive drum 1. Thus, the toner in the developer G carried on the developing roller 51 adheres to the latent image on the photosensitive drum 1. Thereafter, the developer G that has passed the position of the main magnetic pole is transported to the position of the agent separation magnetic pole by the transport magnetic pole. The repelling magnetic field acts on the carrier at the position of the agent separating magnetic pole, and the developer G after the developing process carried on the developing roller 51 is detached from the developing roller 51. The detached developer G is returned again to the first developer transport section 53 and transported toward the downstream side of the first developer transport section 53, and the second developer is passed through the first relay section A. It moves to the upstream side of the transport unit 54. Further, the developer that has moved to the upstream side of the second developer conveying portion 54 reaches the downstream side of the second developer conveying portion 54 together with the replenished toner replenished from the toner replenishing port 44, and the second relay portion B To the upstream side of the first developer conveying portion 53. Such a series of circulation of the developer G is repeated.

After the development process described above, the surface of the photosensitive drum 1 reaches a position facing the intermediate transfer belt 8 and the first transfer bias roller 9, and the toner image on the photosensitive drum 1 is transferred to the intermediate transfer belt 8 at this position. Transferred upward (this is a primary transfer step). At this time, a small amount of untransferred toner remains on the photosensitive drum 1.
Thereafter, the surface of the photoreceptor 1 reaches a position facing the cleaning unit 2, and untransferred toner remaining on the photoreceptor drum 1 at this position is collected by the cleaning blade 2a (cleaning process).
Finally, the surface of the photosensitive drum 1 reaches a position facing a neutralization unit (not shown), and the residual potential on the photosensitive drum 1 is removed at this position.
Thus, a series of image forming processes performed on the photosensitive drum 1 is completed.

  The image forming process described above is performed by each of the four process cartridges 6Y, 6M, 6C, and 6K. That is, referring to FIG. 1, laser light L based on image information is directed onto the photosensitive drums of the process cartridges 6Y, 6M, 6C, and 6K from the exposure unit 7 disposed below the process cartridge. Is irradiated. Specifically, the exposure unit 7 emits laser light L from a light source, and irradiates the photosensitive drum through a plurality of optical elements while scanning the laser light L with a polygon mirror that is rotationally driven. Thereafter, the toner images of the respective colors formed on the respective photosensitive drums through the developing process are transferred onto the intermediate transfer belt 8 in an overlapping manner. In this way, a color image is formed on the intermediate transfer belt 8.

  Here, referring to FIG. 1, the intermediate transfer unit 15 includes an intermediate transfer belt 8, four primary transfer bias rollers 9Y, 9M, 9C, and 9K, a secondary transfer backup roller 12, a counter roller 13, and a tension roller 14. And the cleaning unit 10 and the like. The intermediate transfer belt 8 is stretched and supported by the three roller members 12 to 14 and is endlessly moved in the direction of the arrow in FIG.

The four primary transfer bias rollers 9Y, 9M, 9C, and 9K respectively sandwich the intermediate transfer belt 8 with the photosensitive drums 1Y, 1M, 1C, and 1K to form a primary transfer nip. A transfer bias having a polarity opposite to the polarity of the toner is applied to the primary transfer bias rollers 9Y, 9M, 9C, and 9K.
The intermediate transfer belt 8 travels in the direction of the arrow and sequentially passes through the primary transfer nips of the primary transfer bias rollers 9Y, 9M, 9C, and 9K. In this way, the toner images of the respective colors on the photosensitive drums 1Y, 1M, 1C, and 1K are primarily transferred while being superimposed on the intermediate transfer belt 8.

Thereafter, the intermediate transfer belt 8 on which the toner images of the respective colors are transferred in a superimposed manner reaches a position facing the secondary transfer roller 19. At this position, the secondary transfer backup roller 12 sandwiches the intermediate transfer belt 8 with the secondary transfer roller 19 to form a secondary transfer nip. The color toner image formed on the intermediate transfer belt 8 is transferred onto a recording medium P such as transfer paper conveyed to the position of the secondary transfer nip. At this time, untransferred toner that has not been transferred to the recording medium P remains on the intermediate transfer belt 8.
Thereafter, the intermediate transfer belt 8 reaches the position of the cleaning unit 10 for the intermediate transfer belt 8. At this position, the untransferred toner on the intermediate transfer belt 8 is collected.
Thus, a series of transfer processes performed on the intermediate transfer belt 8 is completed.

Here, the recording medium P transported to the position of the secondary transfer nip is transported from a paper feeding unit 26 disposed below the apparatus main body 100 via a paper feeding roller 27, a registration roller pair 28, and the like. It is a thing.
Specifically, a plurality of recording media P such as transfer paper are stored in the paper supply unit 26 in a stacked manner. When the paper feed roller 27 is driven to rotate counterclockwise in FIG. 1, the uppermost recording medium P is fed toward the rollers of the registration roller pair 28.

  The recording medium P transported to the registration roller pair 28 temporarily stops at the position of the roller nip of the registration roller pair 28 whose rotation drive has been stopped. Then, the registration roller pair 28 is rotationally driven in synchronization with the color image on the intermediate transfer belt 8, and the recording medium P is conveyed toward the secondary transfer nip. In this way, a desired color image is transferred onto the recording medium P.

Thereafter, the recording medium P on which the color image is transferred at the position of the secondary transfer nip is conveyed to the position of the fixing unit 20. At this position, the color image transferred on the surface is fixed on the recording medium P by heat and pressure generated by the fixing roller and the pressure roller.
Thereafter, the recording medium P is discharged to the outside of the apparatus through the rollers of the discharge roller pair 29. The recording medium P discharged from the apparatus main body 100 by the discharge roller pair 29 is sequentially stacked on the stack unit 30 as an output image.
Thus, a series of image forming processes in the image forming apparatus is completed.

Hereinafter, the configuration and operation of the developing device 5 which are characteristic in the present embodiment will be described in detail with reference to FIGS.
FIG. 4 is a longitudinal sectional view of the second developer conveying portion 54 of the developing device 5 as viewed from the side. FIG. 5 is an enlarged cross-sectional view showing the vicinity of the relay ceiling portion 54c (the region surrounded by the broken line in FIG. 4) in the second developer conveying portion 54 in FIG. FIG. 6 is a cross-sectional view showing the vicinity of the relay ceiling 54 c (exhaust port 60) of the developing device 5. FIG. 7 is a perspective view showing a state where the upper case 58 is separated from the developing device 5. 8A is a schematic top view showing a state in which the process cartridge is installed in the image forming apparatus main body 100, and FIG. 8B is a schematic side view thereof.

With reference to FIGS. 4 to 8, the second developer transport section 54 of the developing device 5 (process cartridge 6) in the present embodiment is higher than the ceiling section 54 a (upstream ceiling section) on the upstream side in the transport direction. Is formed to be higher than the height of the ceiling portion 54b (downstream ceiling portion) on the downstream side in the transport direction. Further, the second developer transport section 54 is provided with a relay ceiling section 54c whose height gradually decreases from the upstream ceiling section 54a toward the downstream ceiling section 54b. Specifically, the relay ceiling part 54c is formed so as to incline downward from the upstream ceiling part 54a toward the downstream ceiling part 54b.
The relay ceiling 54 c is provided with an exhaust port 60 that opens to the inside and outside of the developing device 5, and is further provided with a filter 61 (toner filter) that covers the exhaust port 60. The filter 61 is formed so that the eyes thereof are smaller than the particle size of the toner, and the toner can be collected and only air can pass therethrough. Further, the filter 61 is attached via a double-sided tape so as to cover the exhaust port 60 from the outside of the relay ceiling part 54c (inclined ceiling part) so that the developing device 5 can be replaced without being disassembled.

With such a configuration, even if the internal pressure of the developing device 5 is likely to increase due to the rotation of the developing roller 51 and the conveying screws 55 and 56, the air in the developing device 5 is trapped in the air by the filter 61. While being collected, the air is efficiently exhausted from the exhaust port 60 to the outside of the developing device 5.
Specifically, in the second developer transport section 54, the airflow generated as the developer G is transported is from a wide space (the range of the upstream ceiling portion 54a) to a narrow space (the range of the downstream ceiling portion 54b). .) Through the relay ceiling 54c (air flow in the direction of the arrow in FIG. 4). Therefore, the density of the airflow generated in the second developer conveying portion 54 is the highest in the vicinity of the relay ceiling portion 54c, and is efficiently exhausted (degassed) from the exhaust port 60 installed at this position. In this way, an increase in the internal pressure of the developing device 5 is suppressed, and toner scattering from the developing device 5 is reliably reduced. In particular, by providing the above-described ceiling portions 54a to 54c in the second developer conveying portion 54 instead of the first developer conveying portion 53, side effects due to changes in the air flow density in the developer conveying portion (eg, first development) If a large fluctuation in the airflow density occurs in the agent transport unit 53, the developer supply to the developing roller 51 may be affected. ) Can be performed.

Here, with reference to FIGS. 3 and 4, in the present embodiment, a magnetic sensor 57 (installed at the bottom of the second developer conveying section 54) as a toner concentration detecting means is provided on the relay ceiling section 54c. Is disposed downstream in the transport direction.
As a result, the developer that reaches the position of the magnetic sensor 57 is in a state where the surrounding air is decompressed at the position of the relay ceiling portion 54c (exhaust port 60) and flows stably with little bulk fluctuation. become. Therefore, the detection accuracy of the toner density of the developer by the magnetic sensor 57 is improved, and the toner density control in the developing device 5 is stabilized.

Referring to FIG. 2, in the present embodiment, the upstream ceiling portion 54 a of the second developer transport unit 54 is disposed at a position higher than the rotation center of the developing roller 51, and the first developer transport unit 53 is disposed at a position lower than the ceiling portion. That is, the upstream ceiling portion 54a is disposed so that its height falls within the range indicated by the broken-line double arrow in FIG.
If the height of the upstream ceiling portion 54a is too high, the airflow is not collected in a certain direction at the position of the relay ceiling portion 54c, and efficient exhaust from the exhaust port 60 becomes impossible. If the height of the upstream ceiling portion 54a is too low, the airflow density cannot be sufficiently changed at the position of the relay ceiling portion 54c, and efficient exhaust from the exhaust port 60 cannot be performed. End up. Therefore, it is preferable to set the height of the upstream side ceiling portion 54a within the above-described range.

Referring to FIG. 6, in the present embodiment, the exhaust port 60 of the second developer conveying portion 54 has the center position in the short direction when viewed in the longitudinal direction, and the rotation center of the second conveying screw 56. Is arranged so as not to overlap with a virtual vertical line segment passing through. That is, as shown in FIG. 6, the center position of the exhaust port 60 (the center position in the short direction when viewed in the longitudinal direction) is relative to the virtual vertical line segment passing through the rotation center of the second transport screw 56. Thus, it is shifted (offset) by a predetermined distance δ.
When the second developer transport section 54 is viewed in a cross section perpendicular to the longitudinal direction, the position directly above the second transport screw 56 (the position of a virtual vertical line passing through the rotation center of the second transport screw 56). This is the region where the toner is most floating. Therefore, by shifting the center position of the exhaust port 60 in the short direction so as to remove the region, it is possible to reduce the problem that the filter 61 is clogged early. That is, the replacement cycle of the filter 61 can be extended.

Referring to FIG. 7, in the present embodiment, the ceiling of second developer transport section 54 (upstream ceiling 54a, downstream ceiling 54b, and relay ceiling 54c) is the second. An upper case 58 (case) integrated with a ceiling portion of one developer conveying portion 54 is configured to be detachable from the developing device 5.
Specifically, the developing device 5 is configured to be divided into an upper case 58 and a lower case 59. The lower case 59 holds the developing roller 51 and the two conveying screws 55 and 56 rotatably, and a doctor blade 52 is held so as to face the developing roller 51 with a predetermined doctor gap. The upper case 58 is configured to cover an upper portion of the lower case 59 (the main part of the developing device 5) configured as described above, and includes a first developer transport unit 53 and a second developer transport unit. A ceiling portion 54, a toner supply port 44, and the like are formed.
Then, the shaft portions 58 a provided at both ends in the longitudinal direction of the upper case 58 are engaged with the engaging portions 59 a provided at both ends in the longitudinal direction of the lower case 59. Then, the upper case 58 is rotated with respect to the lower case 59 around the engaging portion 59a (shaft portion 58a), so that five claw members 59b (snap fit claws) provided in the longitudinal direction of the lower case 59 are provided. By assembling the holes 58b (snap fit) provided at five locations in the longitudinal direction of the upper case 58, the assembly of the upper case 58 and the lower case 59 (assembly of the developing device 5) is completed. It should be noted that when the upper case 58 and the lower case 59 are separated, the work of the procedure opposite to the procedure described above is performed.

In this way, by configuring the upper case 58 to be detachable from the main part of the developing device 5, the maintenance workability of the developing device 5 by a serviceman is improved. In particular, when replacing the filter 61 installed on the relay ceiling 54c, the entire upper case 58 can be replaced with a new one, so that the time required for maintenance can be shortened. However, the degree of engagement between the claw member 59b of the lower case 59 and the hole 58b of the upper case 58 is set to be tight (tight), and furthermore, they are provided at five locations in the longitudinal direction. The user who replaces the developing device 5 (process cartridge 6) cannot easily separate the upper case 58.
In this embodiment, the doctor blade 52 (developer regulating member) is disposed below the developing roller 51 and is held by the lower case 59. Accordingly, even when the upper case 58 is attached or detached, the doctor gap between the developing roller 51 and the doctor blade 52 may fluctuate, or the developing roller 51 and the doctor blade 52 may come into contact with each other with a strong force and may be damaged. The failure to do is suppressed.

Referring to FIG. 8, in the present embodiment, developing device 5 (process cartridges 6Y, 6M, 6C, 6K) is detachably installed in the longitudinal direction with respect to image forming apparatus main body 100. And the exhaust port 60 of the relay ceiling part 54c is arrange | positioned so that it may open toward the attachment / detachment direction back side of the image development apparatus 5 (process cartridge 6).
Specifically, the developing device 5 (process cartridge 6) is configured to be detachably installed in the longitudinal direction (in the white arrow direction in FIG. 8) with respect to the image forming apparatus main body 100, and the exhaust port 60 is provided. It arrange | positions so that it may open toward the attachment / detachment direction back side (left side of FIG. 8) of the developing apparatus 5.
Thereby, even when the process cartridge 6 is replaced or when a normal image is formed, even if the toner passes through the filter 61, a problem that the toner is scattered to people is suppressed. Specifically, only the end portion in the longitudinal direction of the developing device 5 (the region R in FIG. 8) is contaminated with toner, and an unexpected place (an output image of the output image) of the developing device 5 or the image forming apparatus main body 100 is obtained. The problem that the toner adheres to the place that affects the image quality and the operation of the apparatus, the handle 6a touched by the user when replacing the process cartridge 6, the front side in the longitudinal direction of the process cartridge 6, etc.) is reduced.

  As described above, in the present embodiment, in the developing device 5 in which the first developer transport portion 53 and the second developer transport portion 54 form a circulation path in the longitudinal direction of the developer G, the second developer The height of the ceiling part 54a on the upstream side in the conveyance direction of the conveyance part 54 is formed so as to be higher than the height of the ceiling part 54b on the downstream side in the conveyance direction, and the downstream side in the conveyance direction from the ceiling part 54a on the upstream side in the conveyance direction. A relay ceiling part 54c whose height gradually decreases toward the ceiling part 54b is formed, and an exhaust port 60 and a filter 61 are provided in the relay ceiling part 54c. Thereby, the air in the developing device 5 is efficiently exhausted, and the occurrence of toner scattering can be sufficiently reduced.

In the present embodiment, the present invention is applied to a developing device containing a two-component developer. However, the present invention can also be applied to a developing device containing a one-component developer. . Even in that case, the same effect as that of the present embodiment can be obtained by using the second developer conveying portion 54 configured similarly to the present embodiment.
In the present embodiment, the relay ceiling portion 54c of the second developer conveying portion 54 is configured to gradually decrease in height from the upstream side toward the downstream side. However, the shape of the relay ceiling portion 54c is Without being limited thereto, for example, the relay ceiling portion 54c can be configured to gradually decrease in a curve from the upstream side toward the downstream side.

  It should be noted that the present invention is not limited to the present embodiment, and it is obvious that each embodiment can be modified as appropriate within the scope of the technical idea of the present invention, other than suggested in the present embodiment. is there. In addition, the number, position, shape, and the like of the constituent members are not limited to the present embodiment, and the number, position, shape, and the like suitable for implementing the present invention can be achieved.

1 is an overall configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention. It is a block diagram which shows a process cartridge. FIG. 4 is a cross-sectional view of the developing device and the photosensitive drum as viewed from above. It is sectional drawing which shows the 2nd developer conveyance part of a developing device in a longitudinal direction. FIG. 5 is an enlarged cross-sectional view showing the vicinity of a relay ceiling portion in a second developer conveyance portion of FIG. 4. It is sectional drawing which shows the vicinity of the relay ceiling part of a developing device. It is a perspective view which shows the state which isolate | separated the upper case from the image development apparatus. FIG. 3 is a schematic diagram illustrating a state where a process cartridge is installed in the image forming apparatus main body.

Explanation of symbols

1, 1Y, 1M, 1C, 1K photosensitive drum (image carrier),
5 Development device (development unit),
6, 6Y, 6M, 6C, 6K process cartridge (imaging part),
51 Development roller (developer carrier),
52 Doctor blade (developer regulating member),
53 first developer transport section,
54 second developer transport section,
54a upstream ceiling, 54b downstream ceiling, 54c relay ceiling,
55 1st conveyance screw (1st developer conveyance member),
56 second conveying screw (second developer conveying member),
57 Magnetic sensor (toner concentration detection means),
60 exhaust vent,
61 filters,
100 Image forming apparatus main body (apparatus main body), G developer.

Claims (9)

A developing device for containing a developer and developing a latent image formed on an image carrier,
A developer carrying body facing the image carrying body and carrying a developer;
A first developer conveying section for supplying the developer to the developer carrying member while conveying the developer in the longitudinal direction by a first developer conveying member;
The developer is disposed so as to face the first developer conveying portion via a partition member, and the developer fed from the downstream side in the conveying direction of the first developer conveying portion is caused by the second developer conveying member. A second developer transport unit transported in the longitudinal direction and sent upstream in the transport direction of the first developer transport unit;
With
The second developer transport unit is formed such that the height of the ceiling portion on the upstream side in the transport direction is higher than the height of the ceiling portion on the downstream side in the transport direction, and from the ceiling portion on the upstream side in the transport direction. Comprising a relay ceiling portion whose height gradually decreases toward the ceiling portion on the downstream side in the conveying direction;
The developing device, wherein the relay ceiling portion includes an exhaust port that opens inside and outside the device, and a filter that covers the exhaust port.   The developing device according to claim 1, wherein the relay ceiling portion is formed to be inclined downward from a ceiling portion on the upstream side in the transport direction toward a ceiling portion on the downstream side in the transport direction.   2. The second developer transporting section includes a toner density detecting unit that detects a toner density of the transported developer on the downstream side in the transporting direction with respect to the relay ceiling part. 2. The developing device according to 2. The developer carrier is installed in the first developer transport unit,
The ceiling portion on the upstream side in the transport direction of the second developer transport section is disposed at a position higher than the rotation center of the developer carrier, and is disposed at a position lower than the ceiling section of the first developer transport section. The developing device according to claim 1, wherein the developing device is provided.   The exhaust port is disposed so that a center position in a short side direction does not overlap a virtual vertical line passing through a rotation center of the second developer conveying member when viewed in the longitudinal direction. The developing device according to claim 1. It is configured to be detachably installed in the longitudinal direction with respect to the image forming apparatus main body,
The developing device according to any one of claims 1 to 5, wherein the exhaust port of the relay ceiling portion is disposed so as to open toward a depth side in an attaching / detaching direction of the device. A developer regulating member for regulating the amount of developer carried on the developer carrying body is provided below the developer carrying body,
As the case where the ceiling portion on the upstream side in the transport direction, the ceiling portion on the downstream side in the transport direction, and the relay ceiling portion of the second developer transport portion are integrated with the ceiling portion of the first developer transport portion. The developing device according to claim 1, wherein the developing device is configured to be detachable from the device. A process cartridge that is detachably attached to the image forming apparatus main body,
8. A process cartridge, wherein the developing device according to claim 1 and the image carrier are integrated.   An image forming apparatus comprising the developing device according to claim 1 and the image carrier.

Images