JP2006145921A - Developing device, process cartridge, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device capable of surely restraining toner scattering at the aperture of the developing device with comparatively simple constitution, and to provide a process cartridge and an image forming apparatus. <P>SOLUTION: In the case part 58 of the developing device, a gap A in the vicinity of an aperture part 60, formed between the case part 58 and a developer carrier which passes through the aperture 60, is formed to be equal at the center part in the width direction and at both ends in the width direction, and a gap, formed between the case part 58 and the developer carrier 51 at positions (H1 to H2) away from the vicinity of the aperture 60 in the rotating direction of the developer carrier 51, is formed to be larger in the center part in the width direction than at both ends in the width direction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

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 gap between a developer carrier (developing roller) and a case portion in an opening is used to reduce toner scattering from an opening of a developing device facing the image carrier. A technique for setting (casing gap) within a predetermined range is known (see, for example, Patent Document 1).

Specifically, an opening facing the image carrier (photosensitive drum) is provided in the case portion (casing member) of the developing device. In this opening, a part of the developer carrying member carrying the two-component developer (or one-component developer) is exposed. Then, the toner in the developer carried on the exposed developer carrying body adheres to the electrostatic latent image on the image carrying body, and a desired toner image is formed on the image carrying body. .
Here, in the case portion of the developing device, a gap (casing gap) formed between the developer carrier and the developer carrier after passing through the opening is within a predetermined range in order to limit the airflow generated in the vicinity of the opening. It is formed as follows.

On the other hand, in Patent Document 1 or the like, the case portion (casing member) is matched with the height of the developer carried on the developer carrying member for the purpose of reducing toner scattering at the opening of the developing device. A forming technique is disclosed.
Japanese Patent Application Laid-Open No. H11-228561 and the like disclose a technique for forming a concave structure at a position facing the auxiliary electrode of the developer carrier in the case portion (developer casing) for the purpose of reducing toner scattering at the opening of the developing device. Is disclosed.

JP-A-9-34265 JP 2004-20772 A

  The above-described conventional technology cannot sufficiently suppress toner scattering at the opening of the developing device. Such toner scattering was particularly prominent at both ends of the opening in the width direction.

Further, a developing device in which the rotation direction of the developer carrier is opposite to the conventional one (development so that the downstream side of the rotation direction of the developer carrier at the opening is the upper side of the gravity direction with respect to the upstream side of the rotation direction) In the developing device in which the developer carrying member is driven to rotate, an air flow is likely to be generated in the casing gap formed between the developer carrying member and the upper case, and the above-described toner scattering is a problem that cannot be particularly ignored. It was.
Furthermore, when a substantially spherical toner having a small particle diameter is used to improve the image quality of the output image, the toner itself is likely to be scattered, and the above-described toner scattering is a problem that cannot be particularly ignored.

  The present invention has been made in order to solve the above-described problems. A developing device, a process cartridge, and an image that can reliably reduce toner scattering at the opening of the developing device with a relatively simple configuration. It is to provide a forming apparatus.

The inventor of the present application has made researches to solve the above-described problems, and as a result, has come to know the following matters.
That is, the scattering of toner from the opening of the developing device is the direction and magnitude of an airflow (airflow generated at the position of the casing gap) generated between the case and the downstream side of the opening in the rotation direction due to the rotation of the developer carrier. This is largely due to the fact that the length varies depending on the position in the width direction. Specifically, the airflow generated at the casing gap position in the central portion in the width direction is a large suction airflow from the outside of the developing device to the inside of the developing device. On the other hand, the airflow generated at the casing gap position at both ends in the width direction is an ejected airflow (or a staying state in which no airflow occurs) from the inside of the developing device to the outside of the developing device. The toner in the developing device is scattered outside the developing device due to the jet airflow generated at both ends in the width direction of the opening.

  The direction and magnitude of the airflow generated at the casing gap position is along the rotation direction of the developer carrier on the facing surface (the surface facing the developer carrier) of the case portion forming the casing gap. It can be varied by adjusting the length H in the other direction (the direction perpendicular to the width direction). That is, as the length H of the facing surface (casing gap) is increased, the direction of the airflow is the suction direction, and the size of the airflow is also increased. On the other hand, the smaller the length H of the facing surface (casing gap), the smaller the size of the suction airflow, and the airflow direction changes to the ejection direction when exceeding a certain range.

  The present invention is based on the matters described above, that is, the developing device according to the first aspect of the present invention is a developing device for developing a latent image formed on an image carrier, and A case portion provided with an opening at a position facing the image carrier, and a developer carrier disposed in the case portion so as to carry a developer and to be partially exposed from the opening, The case portion is formed such that a gap in the vicinity of the opening formed between the developer carrying body that has passed through the opening is equal in the width direction central portion and both ends in the width direction. A gap formed between the developer carrying member and the developer carrying member at a position away from the vicinity of the opening along the rotation direction of the developer carrying member is formed so as to be larger in the center portion in the width direction than at both ends in the width direction. It is a thing.

  The developing device according to a second aspect of the present invention is the developing device according to the first aspect, wherein the case portion includes a facing surface standing on the developer carrier side to form the gap, The facing surfaces are formed such that the length of the developer carrying member in the direction along the rotation direction is larger at both ends in the width direction than in the center portion in the width direction.

  A developing device according to a third aspect of the present invention is the developing device according to the second aspect, wherein the facing surface is formed in a concave shape in the width direction.

  According to a fourth aspect of the present invention, in the developing device according to the second aspect, the facing surface is formed in an arch shape in the width direction.

  According to a fifth aspect of the present invention, there is provided the developing device according to any one of the second to fourth aspects, wherein the opposing surface has the same gap with the developer carrier. It is formed.

  The developing device according to a sixth aspect of the present invention is the developing device according to any one of the first to fifth aspects, wherein the developer carrying member has a downstream side in the rotational direction of the opening on the upstream side in the rotational direction. On the other hand, it is rotationally driven so as to be on the upper side in the direction of gravity.

  A developing device according to a seventh aspect of the present invention is the developing device according to any one of the first to sixth aspects, wherein the developing device is located upstream of the developer carrying member at a position opposite to the developer carrier. A developer regulating member for regulating the amount of developer carried on the developer carrying member is provided on the side.

  The developing device according to an eighth aspect of the present invention is the developing device according to the sixth or seventh aspect, wherein the case portion is detachably provided with an upper case disposed on the upper side in the direction of gravity. The gap is formed between the upper case and the developer carrier.

  A developing device according to a ninth aspect of the present invention is the developing device according to any one of the first to eighth aspects, wherein the developer has an average circularity of 0.93 or more. Toner.

  A process cartridge according to a tenth aspect of the present invention is a process cartridge that is detachably attached to the apparatus main body of the image forming apparatus, and is according to any one of the first to ninth aspects. The developing device and the image carrier are integrated.

  The process cartridge according to an eleventh aspect of the present invention is the process cartridge according to the tenth aspect, wherein at least one of a charging unit that charges the image carrier and a cleaning unit that cleans the image carrier is provided. One is further integrated.

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

  According to a thirteenth aspect of the present invention, in the image forming apparatus according to the twelfth aspect of the present invention, a toner container that accommodates toner and is installed in a replaceable manner with respect to the main body of the image forming apparatus, and the toner container And a toner conveying section that conveys the toner contained in the toner to the developing device.

  In the present application, the “process cartridge” refers to a charging unit that charges the image carrier, a developing device (developing unit) that develops a latent image formed on the image carrier, and a cleaning on the image carrier. It is defined as a unit in which at least one of the cleaning units and the image carrier are integrated and configured to be detachable from the image forming apparatus main body.

  In the present invention, the case portion is configured so that the direction and size of the air flow generated at the opening of the developing device is optimized in a range from the width direction both ends to the width direction center. Accordingly, it is possible to provide a developing device, a process cartridge, and an image forming apparatus in which toner scattering at the opening of the developing device is reliably reduced with a relatively simple configuration.

  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.

Embodiment 1 FIG.
A first embodiment of the present invention will be described in detail with reference to FIGS.
First, the configuration and operation of the entire image forming apparatus will be described with reference to FIGS.
FIG. 1 is a block diagram showing a laser printer as an image forming apparatus, and FIG. 2 is a cross-sectional view showing the vicinity of a process cartridge installed therein. 3 is a cross-sectional view of the developing device and the photosensitive drum of the process cartridge of FIG. 2 as viewed from above (in the direction perpendicular to the plane of 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, the process cartridges 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 first 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, the apparatus main body 100 includes each component as a single unit. 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 ratio (toner density) of the toner in the developer G detected by the toner density sensor 57 (magnetic sensor) is within a predetermined range. That is, according to the consumption of toner in the developing device 5, toner is replenished from the toner transport pipe 43 (toner transport unit) into the developer storage unit 54 via the toner supply port 44.

  The toner transport pipe 43 communicates with a corresponding toner bottle among the toner bottles 32Y, 32M, 32C, and 32K (toner containers) installed in the bottle container 31 above the apparatus main body 100 with reference to FIG. is doing. 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. .

  Thereafter, the toner replenished in the developer accommodating portion 54 is mixed and stirred together with the developer G by the second conveying screw 56 and the first conveying screw 55, and the two developer accommodating portions separated by the partition portion 59a are contained. It circulates through the parts 53 and 54 (circulation in the direction of broken arrows in FIG. 3). The toner in the developer G 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. Here, referring to FIG. 3, the developing roller 51 includes a magnet 51b that is fixed inside and forms a magnetic field on the peripheral surface of the roller, and a sleeve 51a that rotates around the magnet 23a1.

  The developer G carried on the developing roller 51 as the developer carrying member is conveyed as the developing roller 51 rotates in the direction of the arrow, and reaches the position of the doctor blade 52 as the developer regulating member. 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 formed in the development area.

  Here, in the first embodiment, the developing roller 51 is rotationally driven so that the downstream side in the rotational direction of the opening 60 is above the upstream side in the direction of gravity (rotation in the counterclockwise direction indicated by an arrow in FIG. 2). .) Further, in accordance with such a configuration, the doctor blade 52 is disposed at a position facing the developing roller 51 and upstream in the rotational direction to the opening 60 (below the developing roller 51). As a result, the image forming unit 6 can be compactly disposed below the intermediate transfer belt.

  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 transfer material P such as transfer paper conveyed to the position of the secondary transfer nip. At this time, the untransferred toner that has not been transferred to the transfer material 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 transfer material P transported to the position of the secondary transfer nip is transported from a paper feed unit 26 disposed below the apparatus main body 100 via a paper feed roller 27, a registration roller pair 28, and the like. It has been done.
Specifically, a plurality of transfer materials P such as transfer paper are stored in the paper supply unit 26 in a stacked manner. When the paper feed roller 27 is rotated in the counterclockwise direction in FIG. 1, the uppermost transfer material P is fed between the rollers of the registration roller pair 28.

  The transfer material P conveyed to the registration roller pair 28 is temporarily stopped at the position of the roller nip of the registration roller pair 28 that has stopped rotating. Then, the registration roller pair 28 is rotationally driven in synchronization with the color image on the intermediate transfer belt 8, and the transfer material P is conveyed toward the secondary transfer nip. In this way, a desired color image is transferred onto the transfer material P.

Thereafter, the transfer material P on which the color image has been 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 to the surface is fixed on the transfer material P by heat and pressure generated by the fixing roller and the pressure roller.
Thereafter, the transfer material P is discharged out of the apparatus through the rollers of the discharge roller pair 29. The transferred 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.

Here, the photosensitive drum 1 has a base tube made of aluminum as a base layer, and a CGL layer (charge generation layer), a CTL layer (charge transport layer), and the like are formed thereon.
The sleeve 51a of the developing roller 51 is made of a nonmagnetic material such as aluminum, and grooves are formed on the outer peripheral surface thereof at a predetermined pitch in the circumferential direction. A DC developing bias is applied to the developing roller 51 from a power supply unit (not shown).
The doctor blade 52 can be formed of a magnetic metal such as iron or stainless steel, or can be formed of a nonmagnetic material such as a resin material or aluminum, or a magnetic material can be formed on a part of the nonmagnetic material. It can also be formed by sticking.

  The developing gap (the gap between the photosensitive drum 1 and the developing roller 51 at the facing position) is set to be 0.2 to 0.5 mm. Furthermore, the doctor gap (the gap between the developing roller 51 and the doctor blade 52) is set to be 0.2 to 0.5 mm.

In the first embodiment, the average circularity of the toner contained in the developer accommodated in the developing device 5 and the toner accommodated in the toner bottles 32Y, 32M, 32C, and 32K is 0.93 or more. The substantially spherical toner formed in the above is used. As a result, it is possible to obtain a fine output image with less dust and good transferability and high image density reproducibility.
Here, the circularity of the toner particles is defined by the following equation.
Circularity = (perimeter of a circle having the same area as the projected area of the particle) / (perimeter of the projected particle image)
Therefore, when the circularity is 1.00, the toner particles have a true spherical shape. The average circularity of the toner can be typically measured using a flow type particle image measuring device “FPIA-2100” (manufactured by Toa Medical Electronics Co., Ltd.).

Further, the toner in the developer G in the developing device 5 and the toner in the toner bottles 32Y, 32M, 32C, and 32K are formed so that the weight average particle diameter is in the range of 3.5 to 7.5 μm. Has been.
As a measuring device for measuring the weight average particle diameter of the toner particles, “Coulter Counter TA-II” (manufactured by Coulter Inc.) or “Coulter Multisizer II” (manufactured by Coulter Inc.) can be used.

  Further, the toner according to the first embodiment is manufactured through the following steps. First, at least a compound having an active hydrogen group in an organic solvent, a reactive modified polyester resin, a colorant, and a release agent are dissolved or dispersed to form a solution or dispersion. Then, the dissolved or dispersed material is dispersed in an aqueous medium containing resin fine particles. The organic solvent is removed from the dispersion obtained by reacting this with at least one of a crosslinking agent and an extender. Finally, the resin fine particles adhering to the surface are washed, and a part or all of the fine particles are detached to form a toner. The toner thus formed has a small particle diameter and is substantially spherical, and is a necessary condition for achieving high image quality.

The carrier in the developer G in the developing device 5 has a weight average particle diameter of 20 to 60 μm, a static resistance of 10 ¹⁰ to 10 ¹⁶ Ω · cm, and a saturation magnetization of 40 to 40. It is formed to be 90 emu / g.
Here, the static resistance (volume resistivity) of the carrier is the resistance value 30 seconds after DC1000V is applied between the two electrodes after the carrier is put between the parallel electrodes having a gap of 2 mm and tapped. This is a value obtained by converting a value measured with a high resist meter into a volume resistivity.
The saturation magnetization of the carrier is measured by the following measurement method using “VSM-P7-15” (manufactured by Toei Kogyo Co., Ltd.). That is, about 0.15 g of a sample was weighed, and the sample was filled in a cell (with an inner diameter of 2.4 mm and a height of 8.5 mm), and then measured under a magnetic field of 1000 oerste (Oe). It is a thing.

Furthermore, the carrier in the first embodiment has a resin coating layer on the surface of the core material. The resin coating layer of the carrier contains conductive particles in which a conductive coating layer comprising a tin dioxide layer and an indium oxide layer containing tin dioxide provided on the tin dioxide layer is provided on the surface of the substrate particles. ing. The conductive particles contained in the resin coating layer are formed so that the oil absorption is 10 to 300 ml / 100 g.
As the base particles of the conductive particles, at least one of aluminum oxide, titanium dioxide, zinc oxide, silicon dioxide, barium sulfide, and zirconium oxide can be used. The oil absorption amount of the conductive particles can be measured in accordance with “21 oil absorption amount” in JIS-K5101 “Pigment Test Method”.
The carrier thus formed has excellent durability.

Hereinafter, the case portion of the developing device 5 that is characteristic of the first embodiment will be described in detail.
FIG. 4A is a partially enlarged view showing the vicinity of the opening 60 of the developing device 5 at the center in the width direction. On the other hand, FIG. 4B is a partially enlarged view showing the vicinity of the opening 60 of the developing device 5 at both ends in the width direction. FIG. 5 is a bottom view of the upper case 58 installed in the developing device 5 as viewed from below.

  Members such as a developing roller 51, a doctor blade 52, and conveying screws 55 and 56 are disposed inside the case portions 58 and 59 that cover the periphery of the developing device 5. Referring to FIGS. 2 and 4, the case portion is composed of a separable upper case 58 and a lower case 59, and an opening 60 is provided at a position facing the photosensitive drum 1. Part of the developing roller 51 held in the case portion is exposed from the opening 60 of the developing device 5. As described above, the toner in the developer G carried on the exposed developing roller 51 adheres to the electrostatic latent image on the photosensitive drum 1, and a desired toner image is formed on the photosensitive drum 1. Will be formed.

  4A and 4B, the upper case 58 (case portion) is formed with a gap formed between the developing roller 51 that has passed through the opening 60 (hereinafter referred to as “casing gap A” as appropriate). Is formed in the vicinity of the opening 60 (on the inlet side) so as to be the same in the width direction central portion and the width direction both ends.

Further, the upper case 58 is a position away from the vicinity of the opening along the rotation direction of the developing roller 51 in the arrow direction (counterclockwise direction) (a position away from the opening 60 by the distance H1 to H2 inside the developing device 5). ), The gap formed between the developing roller 51 and the developing roller 51 is formed so as to be larger at the center portion in the width direction than at both ends in the width direction.
That is, with reference to FIGS. 4 and 5, the opposing surfaces 58 a and 58 b of the upper case 58 (surfaces that stand on the developing roller 51 side to form the casing gap A) are the rotation directions of the developing roller 51. The lengths H <b> 1 and H <b> 2 in the direction along the direction (the direction orthogonal to the width direction) are formed to be larger at both ends in the width direction than in the center portion in the width direction. Specifically, the length H1 of the facing surface 58a at the center portion in the width direction is smaller than the length H2 of the facing surface 58b at both ends in the width direction. Referring to FIG. 5, when the upper case 58 is viewed from below, the facing surfaces 58 a and 58 b are formed in a concave shape in the width direction.

  In addition, the casing gap A formed in the opposing surfaces 58a and 58b of the upper case 58 is substantially equal within the surface. That is, the facing surfaces 58 a and 58 b are formed in an R shape in accordance with the curvature of the developing roller 51. In other words, the casing gap A is formed by the length H1 at the center in the width direction, and the casing gap A is formed by the length H2 (> H1) at both ends in the width direction.

The upper case 58 configured in this manner optimizes the direction and magnitude of the airflow generated at the opening 60 of the developing device 5 in a range from the width direction both ends to the width direction center.
That is, a relatively weak suction airflow is generated by reducing the length H1 of the facing surface 58a (casing gap A) at the central portion in the width direction where a large suction airflow is likely to occur at the casing gap position. As a result, the suction airflow at the central portion in the width direction becomes too large, and the internal pressure of the developing device 5 is increased, so that the problem that the toner is scattered from both ends in the width direction where the airflow is weak can be suppressed. On the other hand, the suction airflow is generated by increasing the length H2 of the opposing surface 58b (casing gap A) at both ends in the width direction where the airflow is likely to be generated at the casing gap position. As a result, it is possible to suppress a problem in which an air flow is generated at both ends in the width direction of the opening 60 and toner is scattered therefrom. That is, by forming the opposing surfaces 58a and 58b of the upper case 58 in a concave shape, a suction air flow that is balanced over the entire range from both ends in the width direction to the center in the width direction without increasing the internal pressure of the developing device 5. Can be generated.

  As described above, in the first embodiment, the direction and the magnitude of the air flow generated at the opening 60 of the developing device 5 are optimized so as to be optimized in the range from the width direction both ends to the width direction center. A case 58 is configured. This reliably reduces toner scattering at the opening 60 of the developing device 5 with a relatively simple configuration.

Embodiment 2. FIG.
A second embodiment of the present invention will be described in detail with reference to FIG.
FIG. 6 is a perspective view showing an upper case installed in the developing device according to the second embodiment. In the upper case 58 of the second embodiment, the facing surfaces 58a and 58b facing the developing roller 51 are formed in an arch shape in the width direction, and the facing surfaces 58a and 58b are formed in a concave shape in the width direction. This is different from that of the first embodiment.

In the second embodiment, similarly to the first embodiment, the case portion of the developing device 5 is provided with an upper case 58 that can be separated. A casing gap A is formed between the opposing surfaces 58 a and 58 b of the upper case 58 and the developing roller 51.
As shown in FIG. 6, in the second embodiment, the opposing surfaces 58a and 58b of the upper case 58 are formed in an arch shape in the width direction.

That is, the opposing surfaces 58a and 58b of the upper case 58 are formed such that the length (H) in the direction along the rotation direction of the developing roller 51 gradually increases from the center in the width direction to both ends in the width direction. Further, the facing surfaces 58 a and 58 b are formed in an R shape in accordance with the curvature of the developing roller 51.
The upper case 58 configured in this manner optimizes the direction and magnitude of the airflow generated at the opening 60 of the developing device 5 in a range from the width direction both ends to the width direction center. In other words, by forming the facing surfaces 58a and 58b of the upper case 58 in an arch shape, the suction is balanced over the entire range from both ends in the width direction to the center in the width direction without increasing the internal pressure of the developing device 5. An air flow can be generated.

As described above, in the second embodiment as well, in the same way as in the first embodiment, the direction and magnitude of the airflow generated in the opening 60 of the developing device 5 ranges from the widthwise both ends to the widthwise center. The upper case 58 is configured so as to be optimized. This reliably reduces toner scattering at the opening 60 of the developing device 5 with a relatively simple configuration.
In addition, the arch shape of the opposing surfaces 58a and 58b of the upper case 58 can be one with a step-like straight line in addition to the one with the curve in the second embodiment.

  In each of the above embodiments, a two-component developer is used as the developer G accommodated in the developing device 5, but the developing device uses a one-component developer (a developer that does not contain a carrier). The present invention can also be applied to this. That is, by forming the facing surfaces 58a and 58b of the upper case 58 facing the developing roller 51 of the one-component developing system in a concave shape or the like, it is possible to obtain the same effects as in the above embodiments.

  In each of the above embodiments, the developing roller 51 is rotationally driven so that the downstream side in the rotational direction of the opening 60 is above the upstream side in the gravitational direction. On the other hand, the present invention can be applied even when the developing roller 51 is configured to be rotationally driven so that the downstream side in the rotational direction of the opening 60 is below the upstream side in the direction of gravity. That is, by forming the facing surface of the case portion (in this case, the lower case) facing the developing roller 51 in a concave shape or the like in the width direction, it is possible to obtain the same effects as in the above embodiments.

  It should be noted that the present invention is not limited to the above-described embodiments, and within the scope of the technical idea of the present invention, the embodiments can be modified as appropriate in addition to those suggested in the embodiments. Is clear. In addition, the number, position, shape, and the like of the constituent members are not limited to the above embodiments, and can be set to a number, position, shape, and the like that are suitable for carrying out the present invention.

1 is an overall configuration diagram illustrating an image forming apparatus according to Embodiment 1 of the present invention. 2 is a side sectional view showing the vicinity of a process cartridge in the image forming apparatus. FIG. FIG. 3 is a cross-sectional view of a part of the process cartridge of FIG. 2 as viewed from above. (A) A partially enlarged view showing the vicinity of the opening of the developing device at the center in the width direction, and (B) a partially enlarged view showing the vicinity of the opening of the developing device at both ends in the width direction. It is the bottom view which looked at the upper case installed in a developing device from the lower part. It is a perspective view which shows the upper case installed in the developing device in Embodiment 2 of this invention.

Explanation of symbols

1, 1Y, 1M, 1C, 1K photosensitive drum (image carrier),
2 cleaning section, 4 charging section,
5 Development device (development unit),
6, 6Y, 6M, 6C, 6K process cartridge (imaging part),
32Y, 32M, 32C, 32K toner bottle (toner container),
43 Toner transport pipe (toner transport section),
51 Development roller (developer carrier),
52 Doctor blade (developer regulating member),
58 Upper case (case part),
58a center facing surface, 58b end facing surface,
59 Lower case (case part), 60 opening,
100 Image forming apparatus main body (apparatus main body).

Claims (13)

A developing device for developing a latent image formed on an image carrier,
A case portion having an opening at a position facing the image carrier;
A developer carrying member disposed in the case portion so as to carry a developer and to be partially exposed from the opening;
The case portion is formed so that a gap in the vicinity of the opening formed between the developer carrying body that has passed through the opening is equal in the width direction center portion and both width direction end portions, A gap formed between the developer carrying member and the developer carrying member at a position away from the vicinity of the opening along the rotation direction of the developer carrying member is formed so as to be larger in the central portion in the width direction than at both ends in the width direction. A developing device. The case portion includes a facing surface standing on the developer carrier side to form the gap,
2. The facing surface is formed so that a length in a direction along a rotation direction of the developer carrying member is larger at both end portions in the width direction than at a center portion in the width direction. Development device. The developing device according to claim 2, wherein the facing surface is formed in a concave shape in the width direction. The developing device according to claim 2, wherein the facing surface is formed in an arch shape in the width direction. The developing device according to claim 2, wherein the facing surface is formed so that a gap with the developer carrying member is equal. 6. The developer carrying member according to claim 1, wherein the developer carrying member is rotationally driven such that a downstream side in the rotational direction of the opening is an upper side in the gravitational direction with respect to an upstream side in the rotational direction. Development device. A developer regulating member that regulates the amount of developer carried on the developer carrying member at a position facing the developer carrying member and upstream in the rotation direction to the opening. The developing device according to claim 1. The case portion is provided with a separable upper case disposed on the upper side in the direction of gravity,
The developing device according to claim 6, wherein the gap is formed between the upper case and the developer carrying member. The developing device according to any one of claims 1 to 8, wherein the developer contains a toner formed so that an average circularity is 0.93 or more. A process cartridge that is detachably installed on the main body of the image forming apparatus,
10. A process cartridge in which the developing device according to claim 1 and the image carrier are integrated. The process cartridge according to claim 10, wherein at least one of a charging unit that charges the image carrier and a cleaning unit that cleans the image carrier is further integrated. An image forming apparatus comprising the developing device according to claim 1 and the image carrier. A toner container that contains toner and is installed in a replaceable manner with respect to the image forming apparatus main body;
A toner transport unit that transports the toner contained in the toner container to the developing device;
The image forming apparatus according to claim 12, further comprising:

Images