Image forming apparatus

Abstract

An image forming apparatus is provided. The image forming apparatus rotates a developer carrier in a direction opposite to that during image formation and rotates an image carrier in the same direction as during image formation, thereby recovering flying toner that has fallen from a filter and adhered to an outer circumferential surface of the developer carrier. A stationary magnet of the developer carrier has a first pole disposed opposite the filter, and a second pole and a third pole downstream thereof. The first pole and the second pole are of opposite magnetic polarity, and the second pole and the third pole are of the same magnetic polarity. An opposing region of the developing sleeve and the second pole is narrower than a gap between the developing sleeve and the filter.

Description

TECHNICAL FIELD

[0001] The present application relates to an image forming apparatus. BACKGROUND

[0002] In an image forming apparatus of an electrophotographic system such as a copying machine or a printer, a device is widely used which forms a toner image on a paper by supplying toner to an electrostatic latent image formed on the outer circumferential surface of an image carrier such as a photosensitive drum, and developing the toner image. In order to continuously form a uniform image, the image forming apparatus conveys a developer containing toner, which is accommodated in a developing container, while stirring it in the developing container.

[0003] In the conventional image forming apparatus, there is a concern that toner scatters from the inside of the developing container to the outside, and the inside of the apparatus is contaminated by the scattered toner. SUMMARY

[0004] An object of the present application is to provide an image forming apparatus which can suppress scattering of toner in the apparatus by achieving a compact configuration.

[0005] The image forming apparatus of the first configuration of the present invention includes an image bearer, a charging section, a cleaning section, a developing device, a voltage application section, and a control section. The image bearer forms an electrostatic latent image on an outer circumferential surface. The charging section charges the outer circumferential surface of the image bearer. The cleaning section cleans the outer circumferential surface of the image bearer. The developing device includes a developing container, a developer conveying member, and a developer bearer. The developing container accommodates a developer including toner supplied to the image bearer. The developer conveying member is rotatably supported in a conveying chamber of the developing container, stirs and conveys the developer to circulate the developer. The developer bearer is opposed to the image bearer, is rotatably supported in the developing container, and supplies the toner in the conveying chamber to the image bearer. The voltage application section applies a developing voltage to the developer bearer. The control section controls the image bearer, the charging section, the cleaning section, the developing device, and the voltage application section. The developing device includes a toner trapping mechanism including a duct, a filter, an exhaust fan, and a vibration generation section. The duct is connected to the conveying chamber, and air in the conveying chamber flows through the duct. The filter is located at a connection portion of the duct and the conveying chamber, and is disposed above the developer bearer, and traps the toner flowing from the conveying chamber into the duct. The exhaust fan causes the air in the conveying chamber to flow out to the outside through the duct. The vibration generation section vibrates the filter. The control section can execute a flying toner recovery mode in which, at a non-image forming time, the filter is vibrated by the vibration generation section, the charging section and the voltage application section are controlled to generate a potential difference in a direction in which the toner moves from the developer bearer to the image bearer, and the developer bearer is rotated in a direction opposite to that at an image forming time, and the image bearer is rotated in the same direction as at the image forming time, whereby the flying toner falling from the filter and adhering to the outer circumferential surface of the developer bearer is recovered by the cleaning section via the image bearer. The developer bearer includes a developing sleeve and a stationary magnet. The developing sleeve is a hollow cylindrical body rotatable around an axis and carrying the developer on an outer circumferential surface. The stationary magnet is fixedly arranged inside the developing sleeve and has a plurality of magnetic poles arranged along a circumferential direction of the developing sleeve. The plurality of magnetic poles include a first pole arranged opposite to the filter, a second pole arranged continuously with the first pole at a position downstream of the filter in a vertical direction, and a third pole arranged continuously with the second pole at a position downstream of the second pole. The first pole and the second pole have opposite magnetic polarities. The second pole and the third pole have the same magnetic polarity. An area of the developing sleeve opposite to the second pole is arranged apart from the developing container by a gap. The gap is narrower than a gap between the developing sleeve and the filter.

[0006] According to the first configuration of the present application, a toner capturing mechanism for attracting and capturing flying toner is formed in the developing device, and the flying toner captured by the filter can be recovered via the image carrier by the cleaning section and the developer carrier. Further, according to the above configuration of the developing device, the flying toner falling from the filter can be inhibited from entering the toner conveying chamber in the developing device. Thus, the flying toner can be efficiently recovered via the image carrier. Therefore, the flying toner in the image forming apparatus can be inhibited by the configuration that realizes the miniaturization. BRIEF DESCRIPTION OF DRAWINGS

[0007] Figure 1 is a schematic cross-sectional front view of an image forming apparatus of one embodiment of the present application.

[0008] Figure 2 is a block diagram showing a configuration of the image forming apparatus of Figure 1

[0009] Figure 3 is a schematic cross-sectional front view of the image forming portion of Figure 1

[0010] Figure 4 is a vertical cross-sectional front view of the developing device of the image forming portion of Figure 3

[0011] Figure 5 is a horizontal cross-sectional plan view of the developing device of the image forming portion of Figure 3

[0012] Figure 6 is a vertical cross-sectional side view of the developing device of the image forming portion of Figure 3

[0013] Figure 7 is a partial enlarged vertical cross-sectional front view of the developing device of Figure 4

[0014] Figure 8 is a partial enlarged cross-sectional front view of the image forming portion of Figure 3 DETAILED DESCRIPTION

[0015] Hereinafter, an embodiment of the present application will be described with reference to the drawings. In addition, the present application is not limited to the following content.

[0016] Figure 1 is a schematic cross-sectional front view of the image forming apparatus 1 of the embodiment. Figure 2 is a block diagram showing a configuration of the image forming apparatus 1 of Figure 1 Figure 3 is​​​​​​​​Figure 1 A schematic cross-sectional front view of the periphery of the image forming unit 20 of the image forming apparatus 1. As an example of the image forming apparatus 1 in this embodiment, it is a serial color printer that uses an intermediate transfer belt 31 to transfer toner images onto paper S. The image forming apparatus 1 can, for example, be a so-called digital multifunction printer with functions such as printing, scanning (image reading), and fax transmission.

[0017] like Figure 1 , Figure 2 as well as Figure 3 As shown, the image forming apparatus 1 includes a paper feeding unit 3, a paper delivery unit 4, an exposure unit 5, an image forming unit 20, a transfer unit 30, a fixing unit 6, a paper output unit 7, and a control unit 8, which are provided on its main body 2.

[0018] The paper feed unit 3 is located at the bottom of the main body 2. The paper feed unit 3 holds multiple sheets of paper S before printing, and separates and feeds the sheets of paper S one by one during printing. The paper feed unit 4 extends vertically along the side wall of the main body 2. The paper feed unit 4 transports the sheets of paper S fed from the paper feed unit 3 to the secondary transfer unit 33 and the fixing unit 6, and then discharges the fixed sheets of paper S from the paper exit 4a to the paper exit 7. The exposure unit 5 is located above the paper feed unit 3. The exposure unit 5 irradiates the image forming unit 20 with a laser controlled based on image data.

[0019] The image forming unit 20 is positioned above the exposure unit 5 and below the intermediate transfer belt 31. The image forming unit 20 includes an image forming unit 20Y for yellow, an image forming unit 20C for cyan, an image forming unit 20M for magenta, and an image forming unit 20B for black. These four image forming units 20 have the same basic configuration. Therefore, in the following description, unless specifically defined, the identification marks “Y,” “C,” “M,” and “B” representing various colors will sometimes be omitted.

[0020] The image forming unit 20 is supported so that it can move in a predetermined direction ( Figure 1 as well as Figure 3 The image forming unit 20 includes a photosensitive drum (image carrier) 21 that rotates clockwise. Around the photosensitive drum 21, the image forming unit 20 also includes a charged section 22, a developing unit 40, and a drum cleaning section (cleaning section) 23 arranged in the direction of rotation. Additionally, a primary transfer section 32 is disposed between the developing unit 40 and the drum cleaning section 23.

[0021] The photosensitive drum 21 is formed in a cylindrical shape extending in the horizontal direction, and has a photosensitive layer formed of, for example, an amorphous silicon photosensitive body on the outer peripheral surface. The charging section 22 charges the surface (outer peripheral surface) of the photosensitive drum 21 to a prescribed potential. The exposure section 5 exposes the outer peripheral surface of the photosensitive drum 21 charged by the charging section 22, and forms an electrostatic latent image of the original image on the outer peripheral surface of the photosensitive drum 21. The developing device 40 supplies toner to this electrostatic latent image to develop it, and forms a toner image. The four image forming sections 20 form toner images of different colors, respectively. The drum cleaning section 23 removes toner and the like remaining on the outer peripheral surface of the photosensitive drum 21 after the toner image is once transferred to the outer peripheral surface of the intermediate transfer belt 31, and performs cleaning. In this way, the image (toner image) formed by the image forming section 20 is transferred to the paper sheet S.

[0022] The transfer section 30 is provided with the intermediate transfer belt 31, the primary transfer sections 32Y, 32C, 32M, 32B, the secondary transfer section 33, and the belt cleaning section 34. The intermediate transfer belt 31 is disposed above the four image forming sections 20. The intermediate transfer belt 31 is supported so as to be rotatable in a prescribed direction (counterclockwise direction in the drawing), and is a ring-shaped intermediate transfer body that sequentially superimposes and primary transfers the toner images formed by the four image forming sections 20, respectively. Figure 1

[0023] The primary transfer sections 32Y, 32C, 32M, 32B are disposed above the image forming sections 20Y, 20C, 20M, 20B of the respective colors, sandwiching the intermediate transfer belt 31. The secondary transfer section 33 is disposed at a position upstream of the fixing section 6 in the paper feeding direction of the paper feeding section 4, and downstream of the four image forming sections 20Y, 20C, 20M, 20B in the rotation direction of the intermediate transfer belt 31. The belt cleaning section 34 is disposed at a position downstream of the secondary transfer section 33 in the rotation direction of the intermediate transfer belt 31.

[0024] The primary transfer sections 32 primary transfer the toner images formed on the outer peripheral surface of the photosensitive drum 21 to the intermediate transfer belt 31. In other words, the toner images are primary transferred by the primary transfer sections 32Y, 32C, 32M, 32B of the respective colors to the outer peripheral surface of the intermediate transfer belt 31. Then, as the intermediate transfer belt 31 rotates, the toner images of the four image forming sections 20 are sequentially superimposed and transferred to the intermediate transfer belt 31 at prescribed timings, thereby forming a color toner image obtained by superimposing the toner images of the four colors of yellow, cyan, magenta, and black on the outer peripheral surface of the intermediate transfer belt 31.

[0025] ​The color toner image of the outer circumferential surface of the intermediate transfer belt 31 is transferred to the paper sheet S that is transported in synchronization by the paper sheet feeding section 4, which is formed in the secondary transfer nip section of the secondary transfer section 33. The belt cleaning section 34 removes and cleans the toner and the like that remain on the outer circumferential surface of the intermediate transfer belt 31 after the secondary transfer. In this way, the transfer section 30 transfers (records) the toner image formed on the outer circumferential surface of the photosensitive drum 21 to the paper sheet S.

[0026] The fixing section 6 is disposed above the secondary transfer section 33. The fixing section 6 heats and presses the paper sheet S on which the toner image is transferred, so that the toner image is fixed to the paper sheet S.

[0027] The paper sheet ejection section 7 is disposed above the transfer section 30. The paper sheet S on which the toner image is fixed and on which the printing is completed is transported to the paper sheet ejection section 7. The printed paper (print) is ejected from above in the paper sheet ejection section 7.

[0028] The control section 8 includes a CPU, an image processing section, a storage section, and other electronic circuits and electronic components (none of which is illustrated). The CPU controls the operation of each of the components provided in the image forming apparatus 1 and performs processing related to the functions of the image forming apparatus 1, in accordance with a program and data for control that are stored in the storage section. The paper sheet feeding section 3, the paper sheet feeding section 4, the exposure section 5, the image forming section 20, the transfer section 30, and the fixing section 6 individually receive an instruction from the control section 8 and perform printing on the paper sheet S in cooperation. The storage section is configured by a combination of a nonvolatile storage device such as a program ROM (Read Only Memory) and a data ROM and a volatile storage device such as a RAM (Random Access Memory).

[0029] In addition, as shown in Figure 2 , the image forming apparatus 1 further includes a voltage application section 12 and a current detection section 13.

[0030] The voltage application section 12 includes, for example, a power supply section and a control circuit (none of which is illustrated). The voltage application section 12 is electrically connected to the developing roller (developer carrier) 44 of the developing device 40, which will be described later. The voltage application section 12 applies a developing voltage to the developing roller 44. The control section 8 controls the timing of application, the voltage value, the polarity, the application time, and the like of the developing voltage to the developing roller 44 via the voltage application section 12.

[0031] The current detection section 13 detects a current that flows between the photosensitive drum 21 and the developing roller 44 when the developing voltage is applied to the developing roller 44. The control section 8 receives information related to the current detected by the current detection section 13 from the current detection section 13.

[0032] Next, in addition to Figure 2 and Figure 3 , aFigure 4 , Figure 5 , Figure 6 as well as Figure 7 The configuration of the developing apparatus 40 will be explained. Figure 4 , Figure 5 as well as Figure 6 yes Figure 3 The image forming unit 20 includes a front view of the vertical cross-section, a top view of the horizontal cross-section, and a side view of the vertical cross-section of the developing apparatus 40. Figure 7 yes Figure 4 A partially enlarged vertical cross-sectional front view of the developing apparatus 40. Furthermore, since the basic structure of the developing apparatus 40 for various colors is the same, descriptions and explanations of the color identification marks for the constituent elements are omitted. In this description, "axial direction" refers to the direction of rotation of the photosensitive drum 21, the first transport member 42, the second transport member 43, and the developing roller 44, which extend parallel to each other. Figure 3 , Figure 4 as well as Figure 7 The paper depth direction, Figure 5 as well as Figure 6 (The left and right horizontal directions).

[0033] The developing apparatus 40 supplies toner to the outer peripheral surface of the photosensitive drum 21. The developing apparatus 40 can be detached from the main body 2 of the image forming apparatus 1, for example. The developing apparatus 40 includes a developing container 50, a first transport member (developer transport member) 42, a second transport member (developer transport member) 43, a developing roller (developer carrier) 44, and a limiting member 45.

[0034] The developing container 50 is an elongated shape extending along the axis of the photosensitive drum 21, with its long side arranged horizontally. That is, the long side of the developing container 50 is parallel to the axis of the photosensitive drum 21. The developing container 50 contains, for example, a two-component developer containing toner and a magnetic carrier, as a developer containing toner supplied to the photosensitive drum 21. The developer may also be, for example, a magnetic single-component developer containing magnetic toner or a non-magnetic single-component developer.

[0035] The developing container 50 includes a partition 51, a first transport chamber 52, a second transport chamber 53, a first connecting portion 54, and a second connecting portion 55.

[0036] A separator 51 is provided in the lower part of the interior of the developing container 50. The separator 51 is positioned in a direction intersecting the long side direction of the developing container 50. Figure 4 left and right horizontal Figure 5 The dividing portion 51 is approximately the central part of the developing container 50 in both the longitudinal and vertical directions. The dividing portion 51 is formed in a generally plate-like shape extending along both the longitudinal and vertical directions of the developing container 50. The dividing portion 51 divides the interior of the developing container 50 in a direction intersecting the longitudinal direction.

[0037] The first transport chamber 52 and the second transport chamber 53 are disposed inside the developing container 50. The first transport chamber 52 and the second transport chamber 53 are formed by dividing the interior of the developing container 50 by a partition 51. The first transport chamber 52 and the second transport chamber 53 are arranged side by side at approximately the same height.

[0038] The second transport chamber 53 is disposed below and adjacent to the area where the developing roller 44 is positioned within the developing container 50. The first transport chamber 52 is disposed within the developing container 50 in a region further away from the developing roller 44 than the second transport chamber 53. The first transport chamber 52 is connected to a developer replenishment tube (not shown) and is replenished with developer via the developer replenishment tube. The first transport chamber 52 transports developer in a first direction f1 via a first transport member 42. The second transport chamber 53 transports developer in a second direction f2, opposite to the first direction f1, via a second transport member 43.

[0039] The first connecting portion 54 and the second connecting portion 55 are respectively disposed on the outer sides of the two ends in the long side direction of the partition portion 51. The first connecting portion 54 and the second connecting portion 55 are in the direction intersecting the long side direction of the partition portion 51. Figure 4 left and right horizontal Figure 5 The first conveying chamber 52 and the second conveying chamber 53 are connected in the thickness direction of the roughly plate-shaped partition 51 (vertical direction). In other words, the first connecting part 54 and the second connecting part 55 connect the first conveying chamber 52 and the second conveying chamber 53 to each other at both ends in the long side direction of the first conveying chamber 52 and the second conveying chamber 53.

[0040] The first connecting portion 54 connects the downstream end of the first transport chamber 52 in the first direction f1 to the upstream end of the second transport chamber 53 in the second direction f2. The first connecting portion 54 transports developer from the first transport chamber 52 side to the second transport chamber 53 side. The second connecting portion 55 connects the downstream end of the second transport chamber 53 in the second direction f2 to the upstream end of the first transport chamber 52 in the first direction f1. The second connecting portion 55 transports developer from the second transport chamber 53 side to the first transport chamber 52 side.

[0041] The first conveying member 42 is disposed within the first conveying chamber 52. The second conveying member 43 is disposed within the second conveying chamber 53. The second conveying member 43 extends close to and parallel to the developing roller 44. The first conveying member 42 and the second conveying member 43 are rotatably supported on the developing container 50 about an axis extending horizontally parallel to the developing roller 44. The first conveying member 42 and the second conveying member 43 have the same basic configuration, having a spiral blade provided on the outer periphery of a rotation axis extending along the long side of the developing container 50.

[0042] The first conveying member 42 conveys the developer in the first direction fl from the second communicating portion 55 side toward the first communicating portion 54 side while stirring the developer within the first conveying chamber 52 along the axis direction of rotation. The second conveying member 43 conveys the developer in the second direction f2 from the first communicating portion 54 side toward the second communicating portion 55 side while stirring the developer within the second conveying chamber 53 along the axis direction of rotation. That is, the first conveying member 42 and the second conveying member convey the developer in opposite directions to each other while stirring the developer, and circulate the developer in a prescribed circulation direction.

[0043] The developing roller 44 is disposed above the second conveying member 43 within the developing container 50, and is disposed opposite the photosensitive drum 21. The developing roller 44 is rotatably supported by the developing container 50 about an axis extending in parallel with the axis of the photosensitive drum 21. The developing roller 44 has, for example, a cylindrical shape of a developing sleeve 441 rotating in the counterclockwise direction in Figure 3 and Figure 4 and a fixed magnet 442 fixedly disposed within the developing sleeve 441 (refer to Figure 4 and Figure 7 ).

[0044] A portion of the outer peripheral surface of the developing roller 44 is exposed from the developing container 50, and is disposed opposite and close to the photosensitive drum 21. The developing roller 44 carries the toner supplied to the outer peripheral surface of the photosensitive drum 21 at the region opposite the photosensitive drum 21 at the outer peripheral surface thereof. The developing roller 44 carries the toner within the second conveying chamber 53 of the developing container 50 and supplies it to the photosensitive drum 21. In other words, the developing roller 44 causes the toner within the second conveying chamber 53 to adhere to the latent image of the outer peripheral surface of the photosensitive drum 21, and forms a toner image.

[0045] The regulating member 45 is disposed on the upstream side of the developing roller 44 in the rotation direction of the developing roller 44 at the region opposite the photosensitive drum 21. The regulating member 45 is disposed close to and opposite the developing roller 44, and is disposed with a prescribed gap between the front end thereof and the outer peripheral surface of the developing roller 44. The regulating member 45 extends over the entire region in the axis direction of the developing roller 44. The regulating member 45 regulates the layer thickness of the developer (toner) carried on the outer peripheral surface of the developing roller 44 through the gap between the front end of the regulating member 45 and the outer peripheral surface of the developing roller 44.

[0046] The developer in the developing container 50 circulates in a predetermined direction between the first conveying chamber 52 and the second conveying chamber 53 via the rotation of the first conveying member 42 and the second conveying member 43. During this time, the toner in the developing container 50 is agitated and charged, and carried onto the outer peripheral surface of the developing roller 44. After the toner carried onto the outer peripheral surface of the developing roller 44 is limited in thickness by the limiting member 45, it is transported to the opposing area between the developing roller 44 and the photosensitive drum 21 by the rotation of the developing roller 44. If a predetermined developing voltage is applied to the developing roller 44, the toner carried on the outer peripheral surface of the developing roller 44 moves towards the outer peripheral surface of the photosensitive drum 21 in the opposing area by utilizing the potential difference between the developing roller 44 and the surface (outer peripheral surface) of the photosensitive drum 21. Thus, the electrostatic latent image on the outer peripheral surface of the photosensitive drum 21 is developed by the toner.

[0047] Next, use Figure 4 , Figure 5 , Figure 6 as well as Figure 7 A more detailed description of the configuration of the developing apparatus 40 will be provided. Additionally, in Figure 4 as well as Figure 6 The document contains an arrow indicating the direction of airflow (fd) within pipe 61.

[0048] The developing apparatus 40 includes a toner collection mechanism 60. The toner collection mechanism 60 includes a conduit 61, a filter 62, an exhaust fan 63, and a vibration generating unit 64. The filter 62 includes a first filter 621 and a second filter 622.

[0049] The conduit 61 is arranged adjacent to the second transport chamber 53. The conduit 61 is positioned in a direction intersecting the long side of the developing container 50. Figure 4 left and right horizontal Figure 6 The developing roller 44, located in the developing container 50, is positioned opposite the photosensitive drum 21 in the paper depth direction. The duct 61 is connected to the second transport chamber 53 at its upstream end in the airflow direction. Air from the second transport chamber 53 flows through the duct 61. The duct 61 has an air inlet 611 and an exhaust outlet 612.

[0050] The air inlet 611 is the connection between the conduit 61 and the second transport chamber 53, and is positioned above the developing roller 44. That is, the air inlet 611 is located upstream of the conduit 61 in the airflow direction. The air inlet 611 is open over the entire area along the long side of the second transport chamber 53. The air inlet 611 is, for example, formed in a rectangular shape extending along the long side of the second transport chamber 53, and is positioned opposite the developing roller 44. The air inlet 611 connects the second transport chamber 53 with the conduit 61. Air from the second transport chamber 53 flows into the conduit 61 through the air inlet 611.

[0051] The exhaust port 612 is provided, for example, at the back of the developing container 50. The exhaust port 612 is located at the downstream end in the air flow direction of the duct 61. Air in the second conveying chamber 53 is discharged from the duct 61 through the exhaust port 612. In addition, the duct 61 can also be connected to other exhaust paths provided with a fan in the main body 2 at the exhaust port 612.

[0052] The exhaust fan 63 is connected to the exhaust port 612. When the exhaust fan 63 is driven, air in the second conveying chamber 53 is forcibly discharged to the outside through the duct 61. In other words, the exhaust fan 63 causes air in the second conveying chamber 53 to flow to the outside through the duct 61.

[0053] The first filter 621 is provided at the portion of the air inlet 611 that is the connection portion of the duct 61 and the second conveying chamber 53. The first filter 621 is the same shape as the air inlet 611, for example, rectangular in shape extending in the long direction of the second conveying chamber 53. The first filter 621 covers the air inlet 611. That is, the first filter 621 opposes the developing roller 44. The first filter 621 is composed of, for example, a non-woven fabric, and traps toner contained in air flowing from the second conveying chamber 53 into the duct 61.

[0054] The second filter 622 is provided downstream in the air flow direction in the duct 61 from the first filter 621. The second filter 622 is the same shape as the cross section in the direction intersecting the air flow direction in the duct 61, for example, rectangular in shape extending in the long direction of the second conveying chamber 53. The second filter 622 covers the air flow cross section in the duct 61. The second filter 622 is composed of, for example, a non-woven fabric, and traps toner contained in air flowing in the duct 61 after passing through the first filter 621.

[0055] [Table 1]

[0056] Pressure loss [mm Aq] First filter 0.42 Second filter 4.50

[0057] An example of the performance of the first filter 621 and the second filter 622 is shown in Table 1. The pressure loss when measuring the upstream static pressure and the downstream static pressure at an air flow rate of 10 cm / s is 0.42 mmAq for the first filter 621 and 4.50 mmAq for the second filter 622. Also, for example, the 0.3 μm trapping rate and the 8 μm trapping rate are both higher for the second filter 622 than for the first filter 621.

[0058] According to the configuration of the filter 62 described above, it is possible to become a configuration in which the first filter 621 does not trap toner in the second conveying chamber 53 in large quantities and is difficult to clog. Furthermore, it is possible to prevent toner from leaking to the outside of the developing container 50 by the second filter 622.

[0059] The vibration generating portion 64 is disposed, for example, adjacently to the back surface of the developing container 50. The vibration generating portion 64 includes, for example, a vibration motor, a control substrate, and other electronic circuits and electronic components (all not shown). A weight for vibration excitation, whose center of gravity is eccentric from the rotation axis of the output shaft, is installed to the output shaft of the vibration motor.

[0060] The vibration generating portion 64 is connected to the first filter 621. When the vibration motor is driven, the vibration generating portion 64 vibrates the first filter 621. By vibrating the first filter 621 by the vibration generating portion 64, the toner captured by the first filter 621 and adhered to the first filter 621 falls down. Therefore, the performance of the first filter 621 can be recovered, and the toner scattering in the image forming apparatus 1 can be continuously suppressed.

[0061] Further, the control portion 8 of the image forming apparatus 1 can execute a scattered toner recovery mode of recovering the toner captured by the first filter 621 by the drum cleaning portion 23. Figure 8 is Figure 3 is a partial enlarged sectional front view of the periphery of the image forming portion 20 and is an explanatory view of the scattered toner recovery mode.

[0062] In addition, in Figure 8 , the rotation direction R11 of the photosensitive drum 21 at the time of image formation, the rotation direction R21 of the developing roller 44 at the time of image formation, and the rotation direction R22 of the developing roller 44 at the time of the scattered toner recovery mode are depicted with arrows. The rotation direction R21 of the developing roller 44 and the rotation direction R22 are directions opposite to each other. In addition, for convenience of explanation, in Figure 8 , the toner (black dot shape) falling down from the first filter 621 is depicted below the first filter 621, the outer peripheral surface of the developing roller 44, and the outer peripheral surface of the photosensitive drum 21, but the actual toner is much smaller than the toner (black dot shape) depicted in Figure 8 .

[0063] In the scattered toner recovery mode, the control portion 8 vibrates the first filter 621 by the vibration generating portion 64 at the time of non-image formation. Further, the control portion 8 controls the charging portion 22 and the voltage applying portion 12 to generate a potential difference in the direction of moving the toner from the developing roller 44 to the photosensitive drum 21, and rotates the developing roller 44 in the direction opposite to the direction at the time of image formation (the R22 direction of Figure 8 ), and rotates the photosensitive drum 21 in the same direction as at the time of image formation (the R11 direction of Figure 8rotates. Thus, in the scattered toner recovery mode, scattered toner that has fallen from the first filter 621 and adheres to the outer peripheral surface of the developing roller 44 is recovered by the drum cleaning portion 23 via the photosensitive drum 21. In addition, in the scattered toner recovery mode, no transfer bias is applied to the primary transfer portion 32, and toner adhering to the outer peripheral surface of the photosensitive drum 21 is not moved from the photosensitive drum 21 to the intermediate transfer belt 31.

[0064] In addition, as shown in Figure 7 and Figure 8 The developing roller 44 has a developing sleeve 441 and a stationary magnet 442.

[0065] The developing sleeve 441 is a hollow cylindrical shape extending along the axial direction of the developing roller 44, and is rotatably supported by the developing container 50. The developing sleeve 441 carries a developer on the outer peripheral surface.

[0066] The stationary magnet 442 is a cylindrical shape extending along the axial direction of the developing roller 44, and is fixed non-rotatably inside the developing sleeve 441. The stationary magnet 442 extends along the axial direction over the entire area of the developing sleeve 441.

[0067] The stationary magnet 442 has a plurality of magnetic poles arranged along the circumferential direction of the developing sleeve 441. The stationary magnet 442 has a first pole 442a, a second pole 442b, and a third pole 442c as the plurality of magnetic poles. These magnetic poles are arranged in the order of the first pole 442a, the second pole 442b, and the third pole 442c along the direction of rotation R21 of the developing sleeve 441 at the time of image formation. In addition, the stationary magnet 442 can have other magnetic poles.

[0068] The first pole 442a is arranged opposite to the first filter 621. In other words, the first pole 442a is located vertically below the first filter 621. The developer is carried on the outer peripheral surface of the developing sleeve 441 by the magnetic force of the first pole 442a, and is transported in the direction of rotation of the developing sleeve 441 as the developing sleeve 441 rotates.

[0069] The second pole 442b is arranged at a position downstream of the first pole 442a in the direction of rotation R21 of the developing sleeve 441 at the time of image formation. In detail, the second pole 442b is arranged continuously with the first pole 442a at a position downstream of the vertically lower end of the first filter 621 in the direction of rotation R21 of the developing sleeve 441 at the time of image formation. The developer is carried on the outer peripheral surface of the developing sleeve 441 by the magnetic force of the second pole 442b, and is transported in the direction of rotation of the developing sleeve 441 as the developing sleeve 441 rotates.

[0070] In addition, the first pole 442a and the second pole 442b are magnetic poles of opposite polarity.

[0071] The third pole 442c is disposed continuously with the second pole 442b on the downstream side of the second pole 442b in the direction of rotation R21 of the image forming of the developing sleeve 441. The developer is carried to the outer peripheral surface of the developing sleeve 441 by the magnetic force of the third pole 442c, and is transported in the direction of rotation of the developing sleeve 441 as the developing sleeve 441 rotates.

[0072] Further, the second pole 442b and the third pole 442c are the same polarity magnetic.

[0073] The region of the developing sleeve 441 opposite the second pole 442b is disposed apart from the developing container 50 by a gap 56. In other words, the developing sleeve 441 is disposed apart from the developing container 50 by the gap 56 in the region opposite the second pole 442b in the radial direction. As shown in FIG. 6, the gap 56 is disposed in the region of the developing sleeve 441 opposite the second pole 442b. Figure 7 As shown, the gap Ll of the gap 56 is narrower than the gap L2 of the developing sleeve 441 and the first filter 621.

[0074] [Embodiments]

[0075] Next, an evaluation of the toner scattering in the image forming apparatus 1 will be described. In this evaluation, 600,000 sheets of an image equivalent to a print rate of 20% with respect to the paper S were printed, and the toner scattering into the image forming apparatus 1 was confirmed. Further, this evaluation was performed in a normal temperature and humidity environment (23°C, 50%) and a high temperature and humidity environment (28°C, 80%) respectively.

[0076] Further, in this evaluation, the scattered toner recovery mode was executed every 4,000 sheets printed. In detail, every 4,000 sheets printed, the developing roller 44 was reversed by the operation of the vibration generating portion 64, the developing voltage at this time was 150 V, and the surface potential of the photosensitive drum 21 was 20 V.

[0077] The pole configurations of the stationary magnet 442 are shown in Table 2. As shown in Table 2, in this evaluation, the image forming apparatus 1 of Embodiments 1 and 2 of the present application, in which the pole configurations of the stationary magnet 442 are different from each other, and the image forming apparatus of the comparative example were prepared.

[0078] [Table 2]

[0079]

[0080] With regard to Table 2, the first pole 442a of the stationary magnet 442 disposed opposite the first filter 621 is an N pole in Embodiments 1 and 2 and the Comparative Example, and the magnetic force is 65 mT. The second pole 442b of the stationary magnet 442 is an S pole in Embodiment 1 and the Comparative Example, and the magnetic force is 35 mT, and is an S pole in Embodiment 2, and the magnetic force is 60 mT. The third pole 442c of the stationary magnet 442 is an N pole in the Comparative Example, and the magnetic force is 60 mT, and is an S pole in Embodiments 1 and 2, and the magnetic force is 60 mT.

[0081] Also, in this evaluation, the interval LI of the opposing region of the developing sleeve 441 and the second pole 442b to the gap 56 of the developing container 50 opposite in the radial direction of the developing roller 44 was 10 mm. The evaluation results are shown in Table 3.

[0082] [Table 3]

[0083]

[0084] With regard to Table 3, for the toner scattering confirmation, confirmation of the toner scattering state in the image forming apparatus was performed by visual observation. With regard to the judgment criteria for the "toner scattering confirmation", the case where toner scattering was not confirmed and the inside of the apparatus remained clean was set to "good", and the case where toner scattering was confirmed and the inside of the apparatus was contaminated with scattered toner was set to "not good".

[0085] From Table 3, it is known that in the image forming apparatus of the Comparative Example, toner scattering occurred in the inside of the apparatus under the high-temperature high-humidity environment. In contrast, it is known that in the image forming apparatuses 1 of Embodiments 1 and 2 of the present application, toner scattering did not occur in the inside of the apparatus under each of the normal-temperature normal-humidity environment and the high-temperature high-humidity environment.

[0086] In this way, according to the configuration of the embodiments, the toner trapping mechanism 60 for attracting and trapping scattered toner is formed in the developing device 40, and the scattered toner trapped by the filter 62 can be recovered by the drum cleaning portion 23 via the developing roller 44 and the photosensitive drum 21.

[0087] Here, under a high-temperature high-humidity environment, there is a tendency that the toner charge amount easily decreases and the amount of scattered toner increases. For the image forming apparatus of the Comparative Example, it is considered that the scattered toner that fell from the first filter 621 and adhered to the outer peripheral surface of the developing roller 44 entered the second conveying chamber 53 in the developing container 50, whereby more toner scattered, and the inside of the apparatus was contaminated with the scattered toner.

[0088] Therefore, according to the constitution of the embodiments of Examples 1 and 2, the second pole 442b and the third pole 442c of the stationary magnet 442 are the same poles, and become repulsive magnetic fields. In addition, the gap LI of the gap 56 in the developing container 50 is narrower than the gap L2 of the developing sleeve 441 and the first filter 621.

[0089] Thus, the toner that has accumulated due to the occurrence of toner stagnation at the portion of the gap 56 in the developing container 50 can be suppressed from entering the second conveying chamber 53 in the developing container 50 from the flying toner that has fallen from the first filter 621. Therefore, the image forming apparatus 1 of the embodiments can cause a large amount of flying toner that has fallen from the first filter 621 to adhere to the outer peripheral surface of the developing roller 44, and can be efficiently recovered via the photosensitive drum 21. Therefore, the flying toner in the image forming apparatus 1 can be suppressed by the constitution that has been miniaturized.

[0090] In addition, it is preferable that the gap 56 of the developing sleeve 441 and the developing container 50 have a gap of twice or less the toner accumulation height on the outer peripheral surface of the opposing region of the second pole 442b of the developing sleeve 441. According to this constitution, toner accumulation can easily occur at the portion of the gap 56 in the developing container 50. Thus, the effect of suppressing the flying toner that has fallen from the first filter 621 from entering the second conveying chamber 53 can be improved. Therefore, the flying toner can be efficiently recovered.

[0091] In addition, it is preferable that the gap 56 of the developing sleeve 441 and the developing container 50 have a gap of twice or less the toner accumulation height on the outer peripheral surface of the opposing region of the second pole 442b of the developing sleeve 441. According to this constitution, toner accumulation can easily occur at the portion of the gap 56 in the developing container 50. Thus, the effect of suppressing the flying toner that has fallen from the first filter 621 from entering the second conveying chamber 53 can be improved. Therefore, the flying toner can be efficiently recovered.

[0092] In addition, the second pole 442b and the third pole 442c of the stationary magnet 442 are disposed at an angle interval of 150 degrees or less of the central angle with respect to the rotation direction of the developing sleeve 441. According to this constitution, the effect of the repulsive magnetic field between the second pole 442b and the third pole 442c can be improved. Thus, toner accumulation can easily occur at the portion of the gap 56 in the developing container 50. That is, the effect of suppressing the flying toner that has fallen from the first filter 621 from entering the second conveying chamber 53 can be improved. Therefore, the flying toner can be efficiently recovered.

[0093] In addition, it is more preferable that the second pole 442b have a larger magnetic force than the first pole 442a. According to this constitution, the effect of the repulsive magnetic field between the second pole 442b and the third pole 442c can be improved. Thus, toner accumulation can easily occur at the portion of the gap 56 in the developing container 50. That is, the effect of suppressing the flying toner that has fallen from the first filter 621 from entering the second conveying chamber 53 can be improved. Therefore, the flying toner can be efficiently recovered.

[0094] Also, the control section 8 executes the flying toner recovery mode every prescribed number of printed sheets. For example, in the image forming apparatus 1 of the above-described embodiment, the control section 8 executes the flying toner recovery mode every 4000 printed sheets. According to this configuration, the flying toner captured by the filter 62 can be periodically recovered by the drum cleaning section 23 via the developing roller 44 and the photosensitive drum 21. Therefore, the suppression effect of the flying toner in the image forming apparatus 1 can be improved.

[0095] In addition, the developer used for the formation of the toner image is a two-component developer containing a magnetic carrier and toner. It is known that in the case of the two-component developer, the flying toner from the developing container 50 easily occurs. Therefore, by executing the above-described flying toner recovery mode in the image forming apparatus 1 using the two-component developer, the flying toner in the image forming apparatus 1 can be further efficiently suppressed.

[0096] In addition, the photosensitive drum 21 has a photosensitive layer formed of an amorphous silicon photoreceptor on the outer peripheral surface. It is known that the photosensitive layer formed of the amorphous silicon photoreceptor has a high dielectric constant and a low toner charge amount. If the toner charge amount is low, the flying toner from the developing container 50 easily occurs. Therefore, by executing the above-described flying toner recovery mode in the image forming apparatus 1 using the photosensitive drum 21 having the amorphous silicon photoreceptor, the flying toner in the image forming apparatus 1 can be further efficiently suppressed.

[0097] The above-described embodiment of the present application has been described, but the scope of the present application is not limited to this, and various modifications can be applied to implement within the scope of the gist of the present application.

[0098] For example, in the above-described embodiment, the image forming apparatus 1 is a so-called tandem type color printing image forming apparatus in which images of a plurality of colors are sequentially superimposed and formed, but is not limited to such a model. The image forming apparatus can not be a color printing image forming apparatus, a monochrome printing image forming apparatus, or a tandem type image forming apparatus.

Claims

1. An image forming apparatus, characterized in that, include: Like a carrier, it forms an electrostatic latent image on the outer peripheral surface; The charged part causes the outer peripheral surface of the image carrier to become charged; The cleaning section cleans the outer peripheral surface of the image carrier; A developing apparatus comprising: a developing container holding a developer containing a toner supplied to the image carrier; a developer delivery member rotatably supported in a delivery chamber of the developing container, which circulates the developer by agitating it while delivering it; and a developer carrier opposite the image carrier, rotatably supported in the developing container, which supplies the toner in the delivery chamber to the image carrier. The voltage application section applies a developing voltage to the developer carrier; as well as The control unit controls the image carrier, the charged part, the cleaning part, the developing apparatus, and the voltage application part. The developing apparatus includes a toner collection mechanism. The toner collection mechanism has: A pipe is connected to the conveying chamber, through which air circulates within the conveying chamber; A filter, located at the connection between the pipe and the delivery chamber and disposed above the developer carrier, captures the toner flowing from the delivery chamber into the pipe; An exhaust fan, through the duct, directs air from the delivery chamber to the outside; and The vibration generator causes the filter to vibrate. The control unit is capable of performing the following toner spillage recovery mode: During non-image formation, the vibration generating unit vibrates the filter, controls the charged unit and the voltage applying unit to generate a potential difference in the direction in which the toner moves from the developer carrier to the image carrier, and causes the developer carrier to rotate in the opposite direction to image formation and the image carrier to rotate in the same direction as image formation. This allows the cleaning unit to recover, via the image carrier, the toner spillage that has fallen from the filter and adhered to the outer periphery of the developer carrier. The developer carrier has: A rotatable hollow cylindrical developing sleeve, with the developing agent carried on its outer circumferential surface; and A fixed magnet is fixed inside the developing sleeve without rotation, and multiple magnetic poles are arranged along the circumference of the developing sleeve. The plurality of magnetic poles have: The first pole is configured opposite to the filter; The second electrode is disposed in the direction of rotation of the developing sleeve at a position that is vertically below and further downstream of the downstream end of the filter. as well as The third electrode is disposed downstream of the second electrode, continuously connected to the second electrode. The first pole and the second pole are opposite magnetic poles. The second pole and the third pole are of the same magnetic polarity. The region of the developing sleeve opposite the second pole is configured with a gap relative to the developing container. The gap is narrower than the distance between the developing sleeve and the filter.

2. The image forming apparatus according to claim 1, characterized in that, The gap between the developing sleeve and the developing container is less than twice the height of the developer buildup on the outer circumferential surface of the opposing region of the developing sleeve.

3. The image forming apparatus according to claim 2, characterized in that, The gap between the developing sleeve and the developing container is less than 10 mm.

4. The image forming apparatus according to claim 1, characterized in that, The second electrode and the third electrode are arranged such that the angle between their central angles in the rotational direction of the developing sleeve is less than 150 degrees.

5. The image forming apparatus according to claim 1, characterized in that, The second pole has a magnetic force greater than that of the first pole.

6. The image forming apparatus according to claim 1, characterized in that, The control unit executes the scattered toner recovery mode every specified number of printed sheets.

7. The image forming apparatus according to claim 1, characterized in that, The developer is a two-component developer comprising a magnetic carrier and the toner.

8. The image forming apparatus according to claim 1, characterized in that, The image carrier has a photosensitive layer formed of amorphous silicon photoreceptor on its outer peripheral surface.

9. The image forming apparatus according to any one of claims 1 to 8, characterized in that, The filter includes: A first filter covers the air inlet, which is open over the entire area along the long side of the delivery chamber, allowing the delivery chamber to communicate with the pipeline; and The second filter is disposed downstream of the first filter in the airflow direction within the duct, and covers the airflow profile within the duct.

Images