IMAGING SYSTEM WITH AIR PASSAGE FOR DEVELOPMENT CHAMBER

An imaging system includes a housing, a developer roller that transfers developer to an image carrier at a development region, a developer regulator to limit a thickness of the developer carried on the developer roller, and an air passage that extends outside a development chamber. The air passage has an inlet to draw an airflow, and an outlet located between the developer regulator and the development region. The air passage has a cross section orthogonal to a direction of the airflow from the inlet to the outlet. In the cross section taken at the narrowest position where the air passage is the narrowest, a width in a width direction parallel to a rotational axis of the developer roller is greater than a thickness that is perpendicular to the width direction.

BACKGROUND

Some imaging apparatuses have a developing device that is equipped with a developing roller and a flow passage member that extends longitudinally in a rotational direction of the developer roller, between the developer roller and an inner wall of a main body of the developing device so as to release pressure inside the developing device main body and to inhibit a toner from scattering outside the developing device main body.

DETAILED DESCRIPTION

Hereinafter, an example imaging system will be described with reference to the drawings. The imaging system may be an imaging apparatus such as printer, or may be a developing device to be used in an imaging apparatus or the like. In the following description, with reference to the drawings, the same reference numbers are assigned to the same components or to similar components having the same function, and overlapping description is omitted.

With reference toFIG.1, an example imaging apparatus1may form a color image using four colors such as magenta, yellow, cyan, and black. The example imaging apparatus1includes a transport device10, a developing device20, a transfer device30, an image carrier40, a fixing device50and an output device60. The transport device10transports a paper P which is a recording medium. The image carrier40has a surface (peripheral surface) on which an electrostatic latent image is formed. The developing device20develops the electrostatic latent image to generate a toner image. The transfer device30secondarily transfers the toner image onto the paper P. The fixing device50fixes the toner image onto the paper P. The output device60outputs the paper P.

The transport device10transports or conveys the paper P, which is a recording medium on which an image is to be formed, along a transport path R1. The papers (or sheets of paper) P are stacked and accommodated in a cassette K, and are picked up and transported by a paper feeding roller11. The transport device10causes the paper P to reach a transfer nip region R2via the transport path R1at the timing the toner image to be transferred onto the paper P reaches the transfer nip region R2.

Four developing devices20are provided, one for each of the colors. Each of the developing devices20includes a developer roller24that carries a toner to the image carrier40. As a developer, the developing device20uses a two-component developer containing a toner (e.g., toner particles) and a carrier (e.g., carrier particles). In some examples, in the developing device20, the developer is adjusted to have an optimal charge amount by adjusting amounts of the toner and the carrier to form a targeted mixing ratio, and by further mixing and stirring the toner and the carrier to uniformly disperse the toner in the developer. The developer is carried on the developer roller24which rotates. When the developer is transported to a development region R4(refer toFIG.2), which faces the image carrier40, via the rotation of the developer roller24, the toner in the developer that is carried on the developer roller24moves onto the electrostatic latent image formed on the peripheral surface of the image carrier40, so that the electrostatic latent image is developed.

The transfer device30transports the toner image, which has been formed by the developing device20, to the transfer nip region R2where the toner image is to be secondarily transferred onto the paper P. The transfer device30includes a transfer belt31, suspension rollers34,35,36, and37, primary transfer rollers32, and a secondary transfer roller33. The toner image is primarily transferred from the image carrier40onto the transfer belt31which is suspended (or supported) on the suspension rollers34,35,36, and37. The transfer belt is pinched (or sandwiched) between the primary transfer rollers32and the respective image carriers40of the developing devices20. The transfer belt31is further pinched between the secondary transfer roller33and the suspension roller37.

The transfer belt31is an endless belt which is circulated by the suspension rollers34,35,36, and37. The suspension rollers34,35,36, and37are rotatable about respective rotational axes. The suspension roller37may be a drive roller that rotates about its rotational axis, and the suspension rollers34,35, and36may be driven rollers that are driven to rotate by the rotation of the suspension roller37. The primary transfer roller32is pressed against the image carrier40from an inner peripheral side of the transfer belt31. The secondary transfer roller33extends parallel to the suspension roller37with the transfer belt31interposed therebetween, so as to press against the suspension roller37from an outer peripheral side of the transfer belt31.

Accordingly, the transfer nip region R2is formed between the secondary transfer roller33and the transfer belt31.

The image carrier40is also called an electrostatic latent image carrier, a photoconductor drum, or the like. Four image carriers40are provided, one for each of the colors. The image carriers40are provided along a movement direction of the transfer belt31. The developing device20, a charging roller41, an exposure unit42, and a cleaning unit43are provided adjacent (e.g., around) each image carrier40.

The charging roller41may charge the surface of the image carrier40with a predetermined potential. The charging roller41moves (rotates) following the rotation of the image carrier40. The exposure unit42exposes the surface of the image carrier40, which has been charged by the charging roller41, to a light according to the image to be formed on the paper P. Accordingly, the potential of a portion of the surface of the image carrier40, which has been exposed to light by the exposure unit42, is changed so that the electrostatic latent image is formed. The four developing devices20develop the electrostatic latent images, which are formed on the respective image carriers40, with the respective toners supplied from toner tanks N that faces the developing devices20, respectively, so that the toner images is generated. The toner tanks N are respectively filled with magenta, yellow, cyan, and black toners and carrier of the amount corresponding to toner filling amounts. The cleaning unit43recovers the toner which remains on the image carrier40after the toner image formed on the image carrier40is primarily transferred onto the transfer belt31.

After the toner image has been secondarily transferred onto the paper P from the transfer belt31, the paper P passes through fixing device50, having a fixing nip region where heat and pressure are applied to the paper P. The fixing device50attaches and fixes the toner image onto the paper P. The fixing device50includes a heating roller52that heats the paper P, and a pressure roller54that presses against and rotates the heating roller52. The heating roller52and the pressure roller54are formed into a cylindrical shape. The heating roller52includes a heat source such as a halogen lamp thereinside. The fixing nip region which is a contact area is provided between the heating roller52and the pressure roller54. When the paper P passes through the fixing nip region, the toner image is melted and fixed onto the paper P.

The output device60includes output rollers62and64for outputting the paper P, onto which the toner image has been fixed by the fixing device50, outside the apparatus.

An example printing process performed by the example imaging apparatus1will be described. When an image signal for a recorded image is input into the imaging apparatus1, a control unit of the imaging apparatus1rotates the paper feeding roller11, so that the papers P stacked in the cassette K are picked up and transported. Then, the surface of the image carrier40is uniformly charged with the predetermined potential by the charging roller41(charging operation). Thereafter, based on the received image signal, the exposure unit42irradiates the surface of the image carrier40with laser beams, so that an electrostatic latent image is formed (exposure operation).

In the developing device20, the electrostatic latent image is developed to form a toner image (development operation). The toner image formed described above is primarily transferred onto the transfer belt31from the image carrier40at a region where the image carrier40faces the transfer belt31(transfer operation). The toner images formed on four image carriers40are sequentially layered on the transfer belt31to form a single composite toner image. Then, the composite toner image is secondarily transferred onto the paper P, which has been transported from the transport device10, at the transfer nip region R2where the suspension roller37faces the secondary transfer roller33.

The paper P, onto which the composite toner image has been secondarily transferred, is transported to the fixing device50. Then, when the paper P passes through the fixing nip region, the fixing device50melts and fixes the composite toner image onto the paper P by heating and pressing the paper P between the heating roller52and the pressure roller54(fixation operation). Thereafter, the paper P is output outside the imaging apparatus1by the output rollers62and64.

FIG.2is a schematic cross-sectional view of an example developing device20A that may be installed into the example imaging apparatus1illustrated inFIG.1. The example developing device20A illustrated inFIG.2includes an image carrier40that is rotatable, a housing21A, a stir portion (or stirring portion)22, a developer roller24that is rotatable, a developer regulator25, and an air passage (or air flow passage)100.

An electrostatic latent image may be formed on the surface of the image carrier40, as previously described. The image carrier40is rotatably supported on the housing21A, and is rotated by a drive source such as a motor. The image carrier40may have a columnar shape.

The housing21A is a container that houses the developing device20A, and has a development chamber H therein. The development chamber H of the housing21A accommodates developer containing a toner and a carrier. In addition, the development chamber H of the housing21A accommodates the stir portion22, the developer roller24, and the developer regulator25. The housing21A has an opening at a position where the developer roller24faces the image carrier40. The toner in the development chamber H is supplied from the opening to the image carrier40. The housing21A includes a filter26that allows air to pass therethrough, into and from the development chamber H, while preventing the developer from passing therethrough. The housing includes a developer output port through which aged developer is discharged from the development chamber H.

With reference toFIGS.2and3, the stir portion22stirs and supplies the developer to the developer roller24. The stir portion22includes a first stir and transport member27A and a second stir and transport member27B. The first stir and transport member27A and the second stir and transport member27B stir the carrier and the toner in the development chamber H, in order to charge, by friction, the carrier and the toner which form the developer. The carrier is a magnetic material and the toner is a non-magnetic material. In addition, the first stir and transport member27A and the second stir and transport member27B transport (or convey) the developer while stirring the developer in the development chamber H. The first stir and transport member27A is located in a first stir and transport path28A positioned at a bottom portion of the development chamber H. The second stir and transport member27B is located in a second stir and transport path28B positioned at an upper portion of the first stir and transport path28A, and faces the developer roller24. Accordingly, the second stir and transport path28B is located between the first stir and transport path28A and the developer roller24. The first stir and transport path28A and the second stir and transport path28B extend in a direction parallel to a rotational axis24A of the developer roller24. The first stir and transport path28A and the second stir and transport path28B are located adjacent to each other. A first supply port29A for supplying the developer from the first stir and transport path28A to the second stir and transport path28B is formed at a first end portion (e.g., in an end portion on one side) of the first stir and transport path28A and the second stir and transport path28B. A second supply port29B for supplying the developer from the second stir and transport path28B to the first stir and transport path28A is formed at a second end portion (e.g., in an end portion on the other side) of the first stir and transport path28A and the second stir and transport path28B. Namely, the first stir and transport path28A and the second stir and transport path28B are partitioned off from each other with a wall which is part of the housing21A. The first supply port29A and the second supply port29B are formed in the wall. Then, while stirring the developer, the first stir and transport member27A transports the developer on the first stir and transport path28A in a first direction to supply the developer from the first supply port29A to the second stir and transport path28B. While stirring the developer on the second stir and transport path28B, the second stir and transport member27B transports the developer in a second direction which is opposite to the first direction, to supply the developer from the second supply port29B to the first stir and transport path28A. Then, the developer which is transported on the second stir and transport path28B by the second stir and transport member27B is supplied to the developer roller24.

As illustrated inFIG.2, the developer roller24is positioned to face the image carrier40and so as to form a gap between the image carrier40and the developer roller24. The developer roller24rotates and has a surface that carries the developer, which is accommodated in the housing21A. The developer roller24is formed into, for example, a columnar shape. The developer roller24is located such that the rotational axis24A of the developer roller24is parallel to a rotational axis40A of the image carrier40and the gap between the developer roller24and the image carrier40is substantially uniform (or constant) in a longitudinal direction which is substantially parallel to the direction of the rotational axis24A and the direction of the rotational axis40A. The developer stirred by the first stir and transport member27A and the second stir and transport member27B are carried on the surface of the developer roller24. When the developer roller24transports the carried developer to the development region R4, the electrostatic latent image on the image carrier40is developed. The development region R4is located between the developer roller24and the image carrier40, where the developer roller24faces the image carrier40. The development region R4may be a region where the developer roller24is the closest to the image carrier40.

The developer roller24includes a developer sleeve24aforming a surface layer of the developer roller24, and a magnet24blocated inside the developer sleeve24a. The developer sleeve24ais a cylindrical member made of non-magnetic metal. The developer sleeve24ais rotatable about the rotational axis24A. The magnet24bis, for example, fixed to a shaft on the rotational axis24A which is fixed to the housing21A, and has a plurality of magnetic poles. In some examples, the developer sleeve24ais rotatably supported on the shaft, to be rotated by a drive source such as a motor. The developer is carried on the surface of the developer sleeve24adue to a magnetic force of the magnet24b. As the developer sleeve24arotates, the developer roller24transports the developer in a rotational direction of the developer sleeve24a.

The developer forms bristles on the developer sleeve24aas a result of the magnetic force of the magnetic poles of the magnet24b. The bristles of the developer may also be referred to as magnetic brushes or developer bristles. The developer roller24brings the developer bristles, which are formed by the magnetic poles, into contact with or adjacent to the electrostatic latent image on the image carrier40in the development region R4. Accordingly, the toner in the developer carried on the developer roller24transfers onto the electrostatic latent image formed on the peripheral surface of the image carrier40, so that the electrostatic latent image is developed.

The developer regulator25limits the thickness of the developer carried on the developer roller24. For example, the developer regulator25limits the carrying amount of the developer carried on the developer roller24. The developer regulator25is located adjacent to the development region R4on an upstream side of the development region R4in the rotational direction of the developer sleeve24a. A predetermined gap is formed between the developer regulator25and the developer sleeve24a. Consequently, when the developer sleeve24arotates, the developer regulator25limits the thickness of a layer of the developer carried on the peripheral surface of the developer sleeve24a, so that the layer is leveled off to become a layer having a uniform layer thickness. The gap between the developer regulator25and the developer sleeve24amay be adjusted, to adjust the amount of the developer to be carried on the developer roller24and to be transported to the development region R4.

As illustrated inFIGS.2and4, the air passage100is a flow passage which extends outside the development chamber H and through which air flows. In some examples, the air passage100may be formed of a hole (air passage) formed within the housing21A. In other examples, the air passage100may be formed of a member (e.g., an external member) which is attached to the housing21A such as a duct extending outside the housing21A. In yet other examples, the air passage100may be formed of both a hole (air passage) formed within the housing21A and a member such as a duct which is attached to the housing21A. The air passage100has an inlet101to receive and to draw in an airflow, and an outlet102to discharge the airflow. The inlet101opens in the development chamber H, and the outlet102opens in a region between the developer regulator25and the development region R4. Namely, the outlet102opens in the region adjacent the developer roller24that extends from the developer regulator25to the development region R4, in the rotational direction of the developer roller24.

When the developer sleeve24aof the developer roller24rotates, air in the gap between the developer roller24and the image carrier40, namely, in the development region R4, is pushed forward in the rotational direction of the developer roller24by the developer bristles formed by the developer carried on the surface of the developer roller24. Accordingly, air is taken into the housing21A on a downstream side of the development region R4in the rotational direction of the developer roller24. Consequently, a positive pressure region104in which is formed in the development chamber H of the housing21A. The air pressure in the positive pressure region104is higher than the atmospheric pressure according to examples, or at least higher than another region in the development chamber H, such as a negative pressure region105which will be described further below. The opening in the housing21A where the developer roller24faces the image carrier40, extends from an upstream edge of the housing to a downstream edge of the housing in the rotational direction of the developer roller. The positive pressure region104is located between the developer roller24and the housing21A and may extend, for example, from the downstream edge of the opening of the housing21A, to the developer regulator25, in the rotational direction of the developer roller24. The developer regulator25limits air which enters a gap between the developer roller24and the developer regulator25on the upstream side of the development region R4in the rotational direction of the developer roller24. Consequently, the region adjacent the developer roller24that extends from the developer regulator25to the development region R4in the rotational direction of the developer roller24forms a negative pressure region105where an air pressure is lower than the atmospheric pressure (or at least lower relative to the positive pressure region104).

Then, the inlet101is located at the positive pressure region104, and the outlet102is located at the negative pressure region105. Accordingly, a pressure difference occurs between the inlet101and the outlet102, and thus air in the positive pressure region104is drawn into the air passage100from the inlet101, and the air drawn into the air passage100is discharged from the outlet102to the negative pressure region105. Accordingly, an airflow occurs in the air passage100to flow from the inlet101toward the outlet102.

The inlet101is, for example, located on an upstream side of the developer regulator25in the rotational direction of the developer roller24. The inlet101is, for example, located on an upstream side, in the rotational direction of the developer roller24, of supply region of the developer roller that is located at a position where the developer roller24faces the stir portion22(the second stir and transport member27B). The inlet101is, for example, located on an upstream side of the filter26, in the rotational direction of the developer roller24. The plurality of magnetic poles of the developer roller24include a pickoff pole (or release pole) where the developer carried on the developer roller24is detached from the developer roller24. The inlet101is, for example, located on an upstream side, in the rotational direction of the developer roller24, of a position corresponding to the pickoff pole (e.g, on an upstream side of the pickoff pole). The outlet102is, for example, located within the developer regulator25, to discharge the air flow between the developer regulator25and the housing21A, or according to examples, the outlet102is located within the housing21A.

As illustrated inFIGS.5and6, the air passage100is a flow passage having a cross section (FIG.6) that is substantially wide and flattened in the direction parallel to the rotational axis24A of the developer roller24. The air passage100has a width W in a width direction parallel to the rotational axis24A of the developer roller24(e.g., an axial direction or a longitudinal direction of the developer roller24), a length L corresponding to a distance to be travelled by the airflow from the inlet101to the outlet102, and a thickness (or depth, or height) T in a thickness direction orthogonal to the width W and the length L. The length L, which corresponds to the distance to be travelled by the airflow from the inlet101to the outlet102, may refer to a length of the air passage100from the inlet101to the outlet102if the air passage100deformed to extend linearly from the inlet101to the outlet102. In addition, a direction in which the airflow travels from the inlet101to the outlet102refers to a lengthwise direction, e.g., a direction along the length L of the air passage100.

The inlet will be described with reference toFIGS.5and7, with further reference toFIGS.8and9. As illustrated inFIGS.5and7, the inlet101extends parallel to the rotational axis24A of the developer roller24. For example, the width W of the inlet101may be substantially the same as the length of a developer carrying region24B of the developer roller24, or may be equal to or less than the length of the developer carrying region24B of the developer roller24. The developer carrying region24B of the developer roller24is a region that is accommodated in the housing21A and is capable of carrying the developer. The length of the developer carrying region24B is a length in the direction parallel to the rotational axis24A. As illustrated inFIGS.5and8, the outlet102extends parallel to the rotational axis24A of the developer roller24. For example, the width W of the outlet102may be substantially the same as the length of the developer carrying region24B of the developer roller24, or in some examples, may be equal to or less than the length of the developer carrying region24B of the developer roller24. The outlet102may be formed of one outlet as illustrated inFIG.8, or according to some examples, may be formed of a plurality of outlets as illustrated inFIG.9. The plurality of outlets102may be spaced apart to face the developer roller (e.g., the outlets102may be located at arbitrary positions facing the developer roller24).

As illustrated inFIGS.5and6, the air passage100has a cross section103that is orthogonal to the direction of the airflow from the inlet101to the outlet102. The width W is larger than the thickness T in the cross section103taken at a narrowest position where the air passage100is the narrowest other than at the inlet101and at the outlet102. Namely, the air passage100is substantially flat in the width direction. The narrowest position is a position where the cross-sectional area of the cross section103is the smallest except for the inlet101and the outlet102. In some examples, the width W may be four times or greater than the thickness T. The width W at the narrowest position may be substantially the same as the length of the developer carrying region24B of the developer roller24, or may be equal to or less than the developer carrying region24B of the developer roller24.

The air passage100may have a cross section from the inlet101to the outlet102. The cross section may be taken along a plane that is orthogonal to the rotational axis24A of the developer roller24, and that intersects the entire length L of the air passage100, from the inlet101to the outlet102, such that the plane intersects an entire travel distance of the airflow through the air passage. Accordingly, the air passage100may entirely extend from the inlet101to the outlet102along at least one plane.

With reference toFIGS.2and3, the air passage100may extend to surround at least part of the stir portion22. For example, the air passage100may be located so as to surround part of the stir portion22, namely, the second stir and transport member27B and the second stir and transport path28B. In addition, as in a developing device20A′ illustrated inFIG.10, the air passage100may extend so as to surround both the first stir and transport path28A and the second stir and transport path28B, or the entirety of the stir portion22.

In the case illustrated inFIGS.2and3, the air passage100may be located between the first stir and transport path28A and the second stir and transport path28B. Here, the first stir and transport path28A and the second stir and transport path28B are partitioned off from each other with the wall which is part of the housing21A. The first supply port29A and the second supply port29B are formed at both ends of the first stir and transport path28A and the second stir and transport path28B. The air passage100is formed in the wall that partitions the first stir and transport path28A off from the second stir and transport path28B, in order to widen the width W of the cross-section of the air passage100taken between the first stir and transport path28A and the second stir and transport path28B. In the case illustrated inFIG.10, the air passage100may be located adjacent an outer surface of the housing21A.

With reference toFIG.11, a guide portion107may be located in the air passage100to guide an airflow in the air passage100. The guide portion107is formed into, for example, a planar shape, and divides part of the air passage100into a plurality of regions. The toner may have a tendency to splash or scatter from both longitudinal ends (in the direction of the rotational axis24A) of the developer roller24at the opening of the housing21A. Accordingly, for example, the guide portion may be positioned so as to direct the airflow toward a center in the width direction of the air passage100, in order to reduce the amount of splashing or scattering of the toner from the opening of the housing21A.

With reference toFIG.12, the development chamber H may communicate with the air passage100via the filter26, such that the air passage100has two inlets, including the inlet101which is a first inlet and the filter26which is a second inlet. A guide portion108may be provided within the air passage adjacent the filter26(e.g., on a side of the filter26which faces the air passage100) such that air output from the filter26is guided in the direction of the airflow (e.g., toward the outlet102) of the air passage100. The guide portion108is formed into, for example, a planar shape or a film shape. Then, the guide portion108may be attached to a wall of the air passage adjacent the filter26at an upstream side of the filter26in the airflow direction of the air passage100so as to partially cover the filter26, and may extend away from the wall and the filter26toward a downstream side in the airflow direction of the air passage100. Consequently, after air output from the filter26to the air passage100is guided in the airflow direction of the air passage100by the guide portion108, the air merges with the airflow in the air passage100. Accordingly, it is possible to increase a flow of the airflow in the air passage100.

As described above, in the imaging apparatus1including the developing device20A illustrated inFIG.2, as the developer roller24rotates, a pressure difference occurs between the inlet101and the outlet102of the air passage100, and thus the airflow flowing from the inlet101toward the outlet102occurs. Accordingly, by inhibiting an increase in the pressure of the development chamber H, it is possible to inhibit the splashing or scattering of the toner caused by an increase in the pressure of the development chamber H. Incidentally, the scattering of the toner caused by an increase in the pressure of the development chamber H is, for example, the scattering of the toner which is output from the opening of the housing21A, or the scattering of the toner which is output along with an airflow ejected from the developer output port of the housing21A.

In addition, the developer drawn into the air passage100from the inlet101is output to the upstream side of the development region R4in the rotational direction of the developer roller24between the developer regulator25and the development region R4, such that the developer is transported back and recovered into the development chamber H while being carried on the developer roller24, so as to inhibit the scattering of the toner output from the air passage100.

In addition, the width W is larger than the thickness T in the cross section103of the air passage100at the narrowest position, to secure a sufficient cross-sectional area of the air passage100. Accordingly, a pressure loss of the airflow flowing through the air passage100decreases, to improve the flow of the airflow through the air passage100.

In addition, the air passage100may extend between the first stir and transport path28A and the second stir and transport path28B, to further shorten the length L of the air passage100as compared to a case where the air passage100is located so as to surround the entirety of the stir portion22. Accordingly, a pressure loss of the airflow flowing through the air passage100decreases, in order to improve the flow of the airflow through the air passage100. Moreover, some of the developer may fall out of the airflow and accumulates in the air passage100such that the air passage100becomes narrow. Accordingly, a shorter length L of the air passage100reduces the amount of the developer that may accumulate in the air passage100, to inhibit the air passage100from becoming narrow.

In addition, some of air in the development chamber H may be drawn into the air passage100from the filter26, to further inhibit an increase in the pressure of the development chamber H.

FIG.13is a schematic cross-sectional view of another example developing device. The example developing device20B may be installed in the imaging apparatus1illustrated inFIG.1. The developing device20B illustrated inFIG.13is similar to the developing device20A illustrated inFIG.2, and includes an image carrier40that is rotatable, a housing21B, a stir portion22; a developer roller24that is rotatable, a developer regulator25, an air passage100B; and a branch air passage111.

The air passage100B and the branch air passage111are formed in the housing21B which may include other configurations similar to the housing21A of the developing device20A illustrated inFIG.2. The air passage100B includes an output port112, and other configurations similar to the air passage100of the developing device20A illustrated inFIG.2.

The output port112is a hole formed in the air passage100B, between the inlet101and the outlet102, in a lower portion of the air passage100B.

The branch air passage111is a flow passage through which air flows. According to some examples, the branch air passage111may be formed of a hole (air passage) formed within the housing21B. In other examples, the branch air passage111may be formed of a member (e.g., an external member) which is attached to the housing21B such as a duct extending outside the housing21B. In yet other examples, the branch air passage111may be formed of both a hole (air passage) formed in the housing21B and a member such as a duct which is attached to the housing21B. One end portion (or first end) of the branch air passage111is connected to the output port112of the air passage100B. Namely, the branch air passage111communicates with the air passage100B via the output port112. The branch air passage111extends downward from the output port112. The other end portion (or second end) of the branch air passage111is connected to the stir portion22. The second end portion of the branch air passage111may be connected to a transport path of the developer in the stir portion22, including any one of the first stir and transport path28A, the second stir and transport path28B, the first supply port29A, and the second supply port29B. As an example, the second end portion of the branch air passage111may be connected to the first stir and transport path28A.

The cross-sectional area of the air passage100B is enlarged at the output port112(e.g., at a position of the air passage100B where the output port112of the air passage100B is formed), to decrease the flow speed of the airflow flowing through the air passage100B at the position of the output port112. Accordingly, the developer scattered in the airflow is caused to fall out of the airflow, to intensively fall downwardly to the output port112, in order to reduce an accumulation of the developer in the air passage100B.

The branch air passage111extends downwardly from the output port112, to guide the developer which has fallen down to the output port112along the branch air passage111. The branch air passage111is connected to the stir portion22, to supply the developer which has fallen down to the output port112, to the stir portion22. Accordingly, it is possible to inhibit a deficiency of the developer in the stir portion22, and to inhibit the occurrence of an image defect.

As illustrated inFIG.14, a check valve113may be located at the second end portion of the branch air passage111which is connected to the stir portion22. The check valve113allows air and the developer to move from the branch air passage111into the stir portion22, and inhibits the developer from flowing backward from the stir portion22to the branch air passage111. The check valve113may be formed of, for example, a film-like member that is elastically deformable, to block the branch air passage111from the stir portion22. When a threshold amount (e.g., a predetermined amount) of the developer accumulates on the check valve113, the check valve113opens the branch air passage111. The check valve113may be bent by, for example, a load from the accumulated developer, in order to open the branch air passage111. The threshold load that opens the branch air passage111by the check valve113can be suitably set according to, for example, the thickness, rigidity, and material of the check valve113. Accordingly, the check valve113maintains the branch air passage111in a closed state until the predetermined amount of the developer accumulates on the check valve113, to inhibit the developer from flowing backward from the stir portion22to the branch air passage111. When the predetermined amount of the developer accumulates on the check valve113, since the check valve113opens the branch air passage111, the developer which has accumulated on the check valve113can be supplied to the stir portion22.

Accordingly to examples, the branch air passage111and the output port112illustrated inFIG.13and the check valve113illustrated inFIG.14can be applied to the developing device20A illustrated inFIG.10. For example, in the developing device20B illustrated inFIG.13, as in the developing device20A′ illustrated inFIG.10, the air passage100B may be located so as to surround the entirety of the stir portion22.

FIG.15is a schematic cross-sectional view of another example developing device. The example developing device20C may be installed in the imaging apparatus1illustrated inFIG.1. The developing device20C illustrated inFIG.15is similar to the developing device20B illustrated inFIG.13, and includes an image carrier40that is rotatable; a housing21C; a stir portion22; a developer roller24that is rotatable; a developer regulator25; an air passage120; and a branch air passage125.

The air passage120and the branch air passage125are formed in the housing21C which may include other configurations similar to the housing21B of the developing device20B illustrated inFIG.13. The air passage120has a different shape between the inlet and the outlet, in comparison to the air passage100B of the developing device20B illustrated inFIG.13.

The air passage120is a flow passage which extends outside the development chamber H and through which air flows. In some examples, the air passage120may be formed of a hole (air passage) formed within the housing21C. According to other examples, the air passage120may be formed of a member (e.g., an external member) which is attached to the housing21C such as a duct which extends outside the housing21C. According to yet other examples, the air passage120may be formed of both a hole (air passage) formed within the housing21C and a member such as a duct which is attached to the housing21C. The air passage120has an inlet121to receive and to draw in an airflow, and an outlet122to discharge the airflow. The inlet121and the outlet122are similar to the inlet101and the outlet102of the developing device20A illustrated inFIG.2. The inlet121and the outlet122have similar shapes and are located at similar positions as those of the inlet101and the outlet102of the developing device20A illustrated inFIG.2.

As illustrated inFIGS.15and16, the air passage120includes a section that is formed into a pipe shape between the inlet121and the outlet122of the air passage120. Namely, the air passage120has a shape where the inlet121which is wide is connected, via the section in the air passage120having a pipe shape, to the outlet122which is wide. The air passage120is positioned so as to extend around an outside the stir portion22, so as to be offset from the stir portion22in a direction parallel to the rotational axis24A of the developer roller24.

As illustrated inFIG.15, an output port126is formed in the air passage120. The output port126is a hole formed in the air passage120, and is formed between the inlet121and the outlet122. The output port126is formed in a lower portion of the air passage120.

The branch air passage125is a flow passage through which air flows. In some examples, the branch air passage125may be formed of a hole (air passage) formed in the housing21C. According to other examples, the branch air passage125may be formed of a member (e.g., an external member) which is attached to the housing21C such as a duct that extends outside the housing21C. In yet other examples, the branch air passage125may be formed of both a hole (air passage) formed in the housing21C and a member such as a duct which is attached to the housing21C. One end portion (a first end) of the branch air passage125is connected to the output port126of the air passage120. Namely, the branch air passage125communicates with the air passage120via the output port126. The branch air passage125extends downward from the output port126. The other end portion (a second end) of the branch air passage125is connected to the stir portion22. The second end portion of the branch air passage125may be connected to a transport path of the developer in the stir portion22, including any one of the first stir and transport path28A, the second stir and transport path28B, the first supply port29A, and the second supply port29B. The second end portion of the branch air passage125is connected to, for example, the first stir and transport path28A.

The cross-sectional area of the air passage120is enlarged at a position of the air passage120adjacent the output port126(e.g., a position where the output port126of the air passage120is formed), to decrease the flow speed of the airflow flowing through the air passage120at the position of the output port126, which causes the developer to fall out of the airflow, so that the developer contained in the airflow may intensively fall down to the output port126, in order to to reduce an accumulation of developer in the air passage120.

In addition, the branch air passage125extends downward from the output port126, to guide the developer which has fallen down to the output port126along the branch air passage125. The branch air passage125is connected to the stir portion22, to supply the developer which has fallen down to the output port126, to the stir portion22so as to inhibit the deficiency of the developer in the stir portion22, in order to inhibit the occurrence of an image defect.

According to examples, in the developing device20C, a check valve similar to the check valve113illustrated inFIG.14may be provided at the second end portion of the branch air passage125which is connected to the stir portion22. The check valve may operate in a similar manner as the check valve113illustrated inFIG.14.

FIG.17is a schematic cross-sectional view of another example developing device. The example developing device20E may be installed on the imaging apparatus1illustrated inFIG.1. The developing device20E illustrated inFIG.17is similar to the developing device20A illustrated inFIG.2, and includes an image carrier40that is rotatable; a housing21E; a stir portion22; a developer roller24that is rotatable; a developer regulator25; and an air passage130.

The air passage130is formed in the housing21E which may include other configurations similar to the housing21A of the developing device20A illustrated inFIG.2. The air passage130includes an inlet at a different position, in comparison to the air passage100of the developing device20A illustrated inFIG.2.

As illustrated inFIGS.17and19, the air passage130is a flow passage which extends outside the development chamber H and through which air flows. In some examples, the air passage130may be formed of a hole (air passage) formed in the housing21E. According to other examples, the air passage130may be formed of a member (e.g., an external member) which is attached to the housing21E such as a duct extending outside the housing21E. According to yet other examples, the air passage130may be formed of both a hole (air passage) formed in the housing21E and a member such as a duct which is attached to the housing21E. The air passage130has an inlet131to receive and draw in an airflow, and an outlet132to discharge the airflow. The outlet132may be similar to the outlet102of the developing device20A illustrated inFIG.2. For example, the outlet132may have a similar shape and may be located at a similar position as those of the outlet102of the developing device20A illustrated inFIG.2. In addition, the shape of a cross section133of the air passage130, taken orthogonally to an airflow direction from the inlet131to the outlet132is the same as the shape of the cross section103(refer toFIG.6) of the developing device20A illustrated inFIG.2. Namely, the air passage130is substantially wide and flattened in a width direction, and the width W is larger than the thickness T in the cross section133at a narrowest position where the air passage130is the narrowest, other than the inlet131and the outlet132.

A gap134is formed between the housing21E and the image carrier40on the downstream side of the development region R4in the rotational direction of the developer roller24. The inlet131of the air passage130is located adjacent to the gap134. The inlet131may be located at a region where the housing21E faces the image carrier40. In addition, the inlet131may be located to communicate at least in part with an outside of the developing device20E, for example, on a side which is opposite to the development region R4with respect to the region where the housing21E faces the image carrier40.

The gap134opens to an outside the developing device20E, the gap134forms an atmospheric pressure region having a pressure that substantially corresponds to the atmospheric pressure. Consequently, a pressure difference occurs between the inlet131located in the gap134which is an atmospheric pressure region and the outlet132located in the negative pressure region105, and thus air in the gap134is drawn into the air passage130from the inlet131, and the air drawn into the air passage130is discharged from the outlet132to the negative pressure region105. As a result of the pressure difference, an airflow occurs in the air passage130to flow from the inlet131toward the outlet132.

As the developer sleeve24aof the developer roller24rotates, air in a region surrounded by the developer roller24, the image carrier40, and the housing21E is delivered to the gap134by the bristles of the developer carried on the surface of the developer roller24. Accordingly, the air delivered to the gap134may contain toner, and the toner contained in the air may tend to splash or scatter outside the developing device20E from the gap134.

Accordingly, the inlet131of the air passage130is located adjacent to the gap134, to draw the air and the toner delivered to the gap134into the air passage130, in order to inhibit the air and the toner from splashing or scattering outside the developing device20E from the gap134.

The developing device20E may include a guide portion similar to the guide portion107illustrated inFIG.11, adjacent the inlet131and/or the outlet132. The guide portion may operate in a similar manner as the guide portion107illustrated inFIG.11.

In some examples, a guide portion similar to the guide portion108illustrated inFIG.12may be provided on or adjacent a side of the filter26which faces the air passage130. The guide portion operates in a similar manner as the guide portion108illustrated inFIG.12.

In some examples, the air passage130may be located so as to surround the entirety of the stir portion22similarly to the developing device20A′ illustrated inFIG.10.

As described above, as the developer sleeve24aof the developer roller24rotates, air is taken into the development chamber H by the bristles of the developer carried on the surface of the developer roller24, which increases an air pressure in the development chamber H (internal pressure of the housing21E). The developing device20E outputs an aged developer from a developer output port formed in the housing21E. However, if the air pressure in the development chamber H becomes too high, since the air in the development chamber H is ejected from the developer output port, an excess of the developer may be ejected, along with a flow of the air, from the developer output port.

With reference toFIGS.20and21, a pressure increase inhibition portion109may be provided adjacent to an opening of the housing21E so as to be positioned on a downstream side of the development region R4in the rotational direction of the developer roller24, and so as to come into contact with the bristles of the developer carried on the surface of the developer roller24. When the pressure increase inhibition portion109comes into contact with the bristles of the developer, the pressure increase inhibition portion109compresses the bristles of the developer to reduce the amount of air which is taken into the development chamber H by the bristles of the developer. The pressure increase inhibition portion109illustrated inFIG.20includes an elastic sheet member109A such as a PET sheet which is elastically deformable. The elastic sheet member109A may be attached to the housing21E, and the bristles of the developer may be compressed by an elastic force of the elastic sheet member109A. The pressure increase inhibition portion109illustrated inFIG.21may include a film-like member109B such as an urethane film which has suitable shape followability, and an elastic flexible member109C such as sponge. The film-like member109B and the elastic flexible member109C are attached to the housing21E such that the film-like member109B is located between the elastic flexible member109C and the developer roller24. The bristles of the developer may be compressed by an elastic force of the elastic flexible member109C.

FIG.22is a schematic cross-sectional view of another example developing device. The example developing device20F may be installed in the imaging apparatus1illustrated inFIG.1. The developing device20F illustrated inFIG.22is similar to the developing device20E illustrated inFIG.17, and includes an image carrier40that is rotatable; a housing21F; a stir portion22; a developer roller24that is rotatable; a developer regulator25; an air passage130F; and a branch air passage135.

The air passage130F and the branch air passage135are formed in the housing21F which may include similar features as the housing21E of the developing device20E illustrated inFIG.17. The air passage130F is similar to the air passage130of the developing device20E illustrated inFIG.17, and further includes an output port136.

The output port136is a hole formed in the air passage130F, between the inlet131and the outlet132, in a lower portion of the air passage130F.

The branch air passage135is a flow passage through which air flows. According to some examples, the branch air passage135may be formed of a hole (air passage) formed in the housing21F. In other examples, the branch air passage135may be formed of a member (e.g., an external member) which is attached to the housing21F such as a duct extending outside the housing21F. In yet other examples, the branch air passage135may be formed of both a hole (air passage) formed in the housing21F and a member such as a duct which is attached to the housing21F. One end portion (a first end) of the branch air passage135is connected to the output port136of the air passage130F. Namely, the branch air passage135communicates with the air passage130F via the output port136. The branch air passage135extends downward from the output port136. The other end portion (a second end) of the branch air passage135is connected to the stir portion22. The second end portion of the branch air passage135may be connected to a transport path of the developer in the stir portion22, including any one of the first stir and transport path28A, the second stir and transport path28B, the first supply port29A, and the second supply port29B. The second end portion of the branch air passage135is connected to, for example, the first stir and transport path28A.

The cross-sectional area of the air passage130F is enlarged at a position where the output port136of the air passage130F is formed, to decrease the flow speed of an airflow flowing through the air passage130F at the position of the output port136, such that the developer tends to fall out of the airflow, to cause the developer contained in the airflow to intensively fall down to the output port136, so as to reduce an accumulation of the developer in the air passage130F.

The branch air passage135extends downward from the output port136, to guide the developer which has fallen down to the output port136along the branch air passage135. The branch air passage135is connected to the stir portion22, to supply the developer which has fallen down to the output port136, to the stir portion22, so as to inhibit the deficiency of the developer in the stir portion22, and to inhibit the occurrence of an image defect.

In some examples, in the developing device20F, a check valve similar to the check valve113illustrated inFIG.14may be provided at the second end portion of the branch air passage135which is connected to the stir portion22. The check valve may operate similarly to the check valve113illustrated inFIG.14.

In some examples, the air passage130F may be located so as to surround the entirety of the stir portion22, similarly to the developing device20A′ illustrated inFIG.10.

FIG.23is a schematic cross-sectional view of another example developing device. The example developing device20G illustrated inFIG.23may be installed in the imaging apparatus1illustrated inFIG.1. The developing device20G illustrated inFIG.23is similar to the developing device20E illustrated inFIG.17, and includes an image carrier40that is rotatable; a housing21G; a stir portion22; a developer roller24that is rotatable; a developer regulator25; and an air passage140.

The air passage140is formed in the housing21G which may include similar features as the housing21E of the developing device20E illustrated inFIG.17. The air passage140has shape between an inlet and an outlet that is different from the air passage130of the developing device20E illustrated inFIG.17.

The air passage140is a flow passage which extends outside the development chamber H and through which air flows. In some examples, the air passage140may be formed of a hole (air passage) formed within the housing21G. In some examples, the air passage140may be formed of a member (e.g., an external member) which is attached to the housing21G such as a duct extending outside the housing21G. In some examples, the air passage140may be formed of both a hole (air passage) formed in the housing21G and a member such as a duct which is attached to the housing21G. The air passage140has an inlet141to receive and draw in an airflow, and an outlet142to discharge the airflow. The inlet141and the outlet142are similar to the inlet131and the outlet132of the developing device20E illustrated inFIG.17. For example, the inlet141and the outlet142have similar shapes and are located at similar positions to those of the inlet131and the outlet132of the developing device20E illustrated inFIG.17.

As illustrated inFIGS.23and24, the air passage140includes a section that is formed into a pipe shape between the inlet141and the outlet142of the air passage140. Namely, the air passage140has a shape where the inlet141which is wide is connected, via the air passage140including a section having a pipe shape, to the outlet142which is wide. The air passage140extends so as to go around outside the stir portion22, to be offset from the stir portion22in the direction parallel to the rotational axis24A of the developer roller24.

In some examples, the developing device20G may include a guide portion similar to the guide portion107illustrated inFIG.11, that is located adjacent to the inlet141or the outlet142. The guide portion may operate in a similar manner as the guide portion107illustrated inFIG.11.

In addition, the development chamber H may communicate with the air passage140via a filter26, and a guide portion similar to the guide portion108illustrated inFIG.12may be provided on a wall of the air passage140(e.g., a side of the filter26which faces the air passage140). The guide portion may operate in in a similar manner as the guide portion108illustrated inFIG.12.

In addition, a pressure increase inhibition portion similar to the pressure increase inhibition portion109illustrated inFIGS.20and21may be provided adjacent to an opening of the housing21G so as to be positioned on the downstream side of the development region R4in the rotational direction of the developer roller24. The pressure increase inhibition portion may operate in a similar manner as the pressure increase inhibition portion109illustrated inFIGS.20and21.

FIG.25is a schematic cross-sectional view of another example developing device. The example developing device20H may be installed in the imaging apparatus1illustrated inFIG.1. The developing device20H illustrated inFIG.25is similar to the developing device20G illustrated inFIG.23, and includes an image carrier40that is rotatable; a housing21H; a stir portion22; a developer roller24that is rotatable; a developer regulator25; an air passage140H; and a branch air passage145.

The air passage140H and the branch air passage145are formed in the housing21H which may include other configurations similar to the housing21G of the developing device20G illustrated inFIG.23. The air passage includes an output port146and may include other configurations similar to the air passage140of the developing device20G illustrated inFIG.23.

The output port146is a hole formed in the air passage140H, between the inlet141and the outlet142and in a lower portion of the air passage140H.

The branch air passage145is a flow passage through which air flows. According to examples, the branch air passage145may be formed of a hole (air passage) formed in the housing21H. In other examples, the branch air passage145may be formed of a member (e.g., an external member) which is attached to the housing21H such as a duct extending outside the housing21H. In yet other examples, the branch air passage145may be formed of both a hole (air passage) formed in the housing21H and a member such as a duct which is attached to the housing21H. One end portion (a first end) of the branch air passage145is connected to the output port146of the air passage140H. Accordingly, the branch air passage145communicates with the air passage140H via the output port146. The branch air passage145extends downward from the output port146. The other end portion (a second end) of the branch air passage145is connected to the stir portion22. The second end portion of the branch air passage145is connected to a transport path of the developer in the stir portion22, including any one of the first stir and transport path28A, the second stir and transport path28B, the first supply port29A, and the second supply port29B. The second end portion of the branch air passage145is connected to, for example, the first stir and transport path28A.

The cross-sectional area of the air passage140H is enlarged at a position of the air passage, where the output port146of the air passage140H is formed, to decrease the flow speed of an airflow flowing through the air passage140H at the position of the output port146. Accordingly, the developer is likely to fall out of the airflow at the position of the output port, and the developer contained in the airflow may intensively fall down to the output port146, so as to reduce the amount of the developer to accumulate in the air passage140H.

In addition, the branch air passage145extends downward from the output port146, to guide the developer which has fallen down to the output port146along the branch air passage145. The branch air passage145is connected to the stir portion22, the developer which has fallen down to the output port146can be supplied to the stir portion22, so as to inhibit the deficiency of the developer in the stir portion22, and to inhibit the occurrence of an image defect.

In some examples, the developing device20H may include a check valve similar to the check valve113illustrated inFIG.14at the second end portion of the branch air passage145which is connected to the stir portion22. The check valve may operate similarly to the check valve113illustrated inFIG.14.

For example, the air passage may be formed of a single air hole, or may be formed of a plurality of air holes. The plurality of air holes may each have a width and a cross-sectional area, and the width W (or cross-sectional area) of the air passage at the narrowest position may correspond to a sum of widths (or sum of cross-sectional areas) of the plurality of air holes, taken where the sum of widths is the lowest or where the sum of the cross-sectional areas is the smallest. In addition, in examples in which the air passage is located between the first stir and transport path and the second stir and transport path and the air passage is formed of a plurality of air holes, part of the air holes may be located between the first supply port and the second supply port, and the remaining air holes may be located outside the first supply port and the second supply port (e.g., excluding the region between the first supply port and the second supply port).

In addition, for example, in the developing devices illustrated inFIGS.15,23, and25, the air passage having a pipe shape has been described as an example; however, various shapes of air passages may be applied to the developing devices.