Image forming apparatus

Abstract

An image forming apparatus is provided. The image forming apparatus is capable of executing a flying toner recovery mode in which a filter is vibrated at a non-image forming time, control is performed to generate a potential difference in a direction in which toner moves from a developer carrier to an image carrier, and the developer carrier is rotated in a direction opposite to that at an image forming time and the image carrier is rotated in the same direction as at the image forming time, whereby flying toner that has fallen from the filter and adhered to the developer carrier is recovered by a cleaning portion via the image carrier. A stationary magnet of the developer carrier has a first pole opposite the image carrier, a second pole opposite the filter, and an intermediate pole therebetween.

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] An image forming apparatus of a 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 faces 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 outer circumferential surface on which the developer is carried. The stationary magnet is fixed non-rotatably inside the developing sleeve, and a plurality of magnetic poles are arranged along a circumferential direction of the developing sleeve. The plurality of magnetic poles include a first pole disposed in an opposite region to the image bearer in a rotation direction of the developing sleeve, a second pole disposed in an opposite region to the filter in the rotation direction of the developing sleeve, and at least one intermediate pole disposed between the first pole and the second pole in the rotation direction of the developing sleeve. The first pole and the second pole are the same magnetic polarity. The intermediate poles are disposed in an odd number such that the intermediate poles adjacent to the first pole and the second pole are of the opposite magnetic polarity to the first pole and the second pole, and the adjacent intermediate poles are of the opposite magnetic polarity to each other.

[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 stationary magnet of the developer carrier, the flying toner can be efficiently recovered via the image carrier. Therefore, the flying toner in the image forming apparatus can be suppressed 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 section of Figure 1

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

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

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

[0013] Figure 7 is a partial enlarged cross-sectional front view of the image forming section of Figure 3 DETAILED DESCRIPTION

[0014] 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.

[0015] 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 a schematic cross-sectional front view of the image forming section of 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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 in which the toner images formed by the four image forming sections 20 are sequentially superimposed and once transferred. Figure 1

[0022] 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.

[0023] The primary transfer sections 32 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 once transferred to the outer peripheral surface of the intermediate transfer belt 31 by the primary transfer sections 32Y, 32C, 32M, 32B of the respective colors. 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, and a color toner image obtained by superimposing the toner images of the four colors of yellow, cyan, magenta, and black is formed on the outer peripheral surface of the intermediate transfer belt 31.

[0024] ​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.

[0025] 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.

[0026] The paper sheet discharge 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 discharge section 7. The printed paper (print) is taken out from above in the paper sheet discharge section 7.

[0027] 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 shown). The CPU controls the operation of each of the constituent elements 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 constituted 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).

[0028] 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.

[0029] The voltage application section 12 includes, for example, a power supply section and a control circuit (none of which is shown). 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 of the developing voltage to the developing roller 44, the voltage value, the polarity, the application time, and the like, via the voltage application section 12.

[0030] 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.

[0031] Next, in addition to Figure 2 and Figure 3 , aFigure 4 , Figure 5 and Figure 6 The configuration of the developing device 40 will be described. Figure 4 , Figure 5 and Figure 6 are a vertical sectional front view, a horizontal sectional plan view, and a vertical sectional side view of the developing device 40 of the image forming portion 20 of Figure 3 . In addition, the developing devices 40 of various colors are the same in basic configuration, so the description and explanation of the identification marks of various colors are omitted for the constituent elements. In addition, in this description, the "axial direction" indicates the axial direction of the rotation of each of the photosensitive drum 21, the first conveying member 42, the second conveying member 43, and the developing roller 44, which extend in parallel to each other Figure 3 and Figure 4 the paper depth direction, Figure 5 and Figure 6 the lateral direction.

[0032] The developing device 40 supplies toner to the outer peripheral surface of the photosensitive drum 21. The developing device 40 is detachable with respect to the main body 2 of the image forming apparatus 1, for example. The developing device 40 includes a developing container 50, a first conveying member (developer conveying member) 42, a second conveying member (developer conveying member) 43, a developing roller (developer carrier) 44, and a restriction member 45.

[0033] The developing container 50 is in an elongated shape extending in the axial direction of the photosensitive drum 21, and is horizontally disposed in the longitudinal direction. That is, the longitudinal direction of the developing container 50 is parallel to the axial direction of the photosensitive drum 21. The developing container 50 accommodates, for example, a two-component developer including toner and a magnetic carrier, as a developer including toner to be supplied to the photosensitive drum 21. The developer can also be a magnetic one-component developer including a magnetic toner, a non-magnetic one-component developer, for example.

[0034] The developing container 50 includes a partition 51, a first conveying chamber 52, a second conveying chamber 53, a first communication portion 54, and a second communication portion 55.

[0035] The partition 51 is provided at a lower portion of the inside of the developing container 50. The partition 51 is disposed at a substantially central portion of the developing container 50 in a direction intersecting the longitudinal direction Figure 4 the lateral direction, Figure 5 the vertical direction). The partition 51 is formed in a substantially plate shape extending in the longitudinal direction and the vertical direction of the developing container 50. The partition 51 divides the inside of the developing container 50 in the direction intersecting the longitudinal direction.

[0036] The first and second conveying chambers 52 and 53 are provided inside the developing container 50. The first and second conveying chambers 52 and 53 are formed by dividing the inside of the developing container 50 by the partition 51. The first and second conveying chambers 52 and 53 are arranged side by side at substantially the same height as each other.

[0037] The second conveying chamber 53 is arranged below the arrangement region of the developing roller 44 inside the developing container 50. The first conveying chamber 52 is arranged at a region inside the developing container 50 farther from the developing roller 44 than the second conveying chamber 53. The first conveying chamber 52 is connected to a developer replenishing tube (not shown) via which developer is replenished. The first conveying chamber 52 conveys developer to the first direction fl by the first conveying member 42. The second conveying chamber 53 conveys developer to the second direction f2 opposite to the first direction fl by the second conveying member 43.

[0038] The first and second communication portions 54 and 55 are arranged outside both end portions in the longitudinal direction of the partition 51. The first and second communication portions 54 and 55 communicate the first and second conveying chambers 52 and 53 in the thickness direction of the partition 51 which is substantially plate-shaped, that is, the left-right lateral direction of the partition 51, the up-down direction of the partition 51, and the like. Figure 4 Figure 5 The first and second communication portions 54 and 55 communicate the first and second conveying chambers 52 and 53 to each other at both end portion sides in the longitudinal direction of the first and second conveying chambers 52 and 53.

[0039] The first communication portion 54 communicates the first direction fl downstream end of the first conveying chamber 52 and the second direction f2 upstream end of the second conveying chamber 53. The first communication portion 54 conveys developer from the first conveying chamber 52 side toward the second conveying chamber 53 side. The second communication portion 55 communicates the second direction f2 downstream end of the second conveying chamber 53 and the first direction fl upstream end of the first conveying chamber 52. The second communication portion 55 conveys developer from the second conveying chamber 53 side toward the first conveying chamber 52 side.

[0040] The first conveying member 42 is arranged inside the first conveying chamber 52. The second conveying member 43 is arranged inside the second conveying chamber 53. The second conveying member 43 extends in parallel close to the developing roller 44. The first and second conveying members 42 and 43 are rotatably supported to the developing container 50 about an axis extending in the horizontal direction in parallel to the developing roller 44. The first and second conveying members 42 and 43 are substantially constituted the same, and are in a form in which a spiral blade is provided to the outer peripheral portion of a rotation shaft extending in the longitudinal direction of the developing container 50.

[0041] ​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.

[0042] 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 FIG. 2, and a fixed magnet 442 fixed within the developing sleeve (see FIG. 3). Figure 3 Figure 4 The developing sleeve 441 and the fixed magnet 442 are disposed in the developing container 50. The developing sleeve 441 is disposed in the developing container 50 so as to be rotatable about an axis extending in parallel with the axis of the photosensitive drum 21. The fixed magnet 442 is fixed within the developing sleeve 441. The fixed magnet 442 is disposed so as to be opposed to the photosensitive drum 21. Figure 4

[0043] A portion of the outer peripheral surface of the developing roller 44 is exposed from the developing container 50, and is opposed to 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 in the opposed region to the photosensitive drum 21. The developing roller 44 carries the toner within the second conveying chamber 53 of the developing container 50, and supplies the toner 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.

[0044] The regulating member 45 is disposed on the upstream side in the rotation direction of the developing roller 44 of the opposed region of the developing roller 44 and the photosensitive drum 21. The regulating member 45 is disposed close to and opposed to 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 in 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.

[0045] ​​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.

[0046] Next, use Figure 4 , Figure 5 as well as Figure 6 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] [Table 1]

[0055] Pressure loss [mmAq] First filter 0.42 Second filter 4.50

[0056] 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.

[0057] According to the configuration of the filter 62 described above, it is possible to achieve 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.

[0058] 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.

[0059] 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.

[0060] 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 7 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.

[0061] In addition, in Figure 7 , 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, 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 in Figure 7 , but the actual toner is much smaller than the toner (black dot shape) depicted in Figure 7 .

[0062] 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 7 ), and rotates the photosensitive drum 21 in the same direction as at the time of image formation (the R11 direction of Figure 7direction of R11). Thus, in the scattered toner recovery mode, the scattered toner that has fallen from the first filter 621 and adhered 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 the 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.

[0063] In addition, as shown in FIG. 1, the developing roller 44 has a developing sleeve 441 and a stationary magnet 442. Figure 7

[0064] The developing sleeve 441 is a hollow cylindrical shape extending in the axial direction of the developing roller 44, and is rotatably supported by the developing container 50. The developing sleeve 441 carries the developer on the outer peripheral surface.

[0065] The stationary magnet 442 is a cylindrical shape extending in the axial direction of the developing roller 44, and is fixed non-rotatably inside the developing sleeve 441. The stationary magnet 442 extends in the axial direction over the entire region of the developing sleeve 441.

[0066] The stationary magnet 442 has a plurality of magnetic poles arranged in the circumferential direction of the developing sleeve 441. The stationary magnet 442 has a first pole 442a, a second pole 442b, and an intermediate 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 intermediate pole 442c in 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.

[0067] The first pole 442a is disposed in the opposite region to the photosensitive drum 21 in the direction of rotation R21 of the developing sleeve 441 at the time of image formation. For example, the first pole 442a generates a peak magnetic force in the region where the developing roller 44 is closest to the photosensitive drum 21. The first pole 442a causes the developer to be carried on the outer peripheral surface of the developing sleeve 441 by this magnetic force, and causes only the toner to fly toward the photosensitive drum 21 by applying a developing voltage, thereby developing the latent image on the outer peripheral surface of the photosensitive drum 21.

[0068] The second pole 442b is disposed in the opposite region to the first filter 621 in the direction of rotation R21 of the developing sleeve 441 at the time of image formation. In other words, the second pole 442b is disposed 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. 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.

[0069] In addition, the first pole 442a and the second pole 442b are the same polarity.

[0070] ​The intermediate pole 442c is disposed between the first pole 442a and the second pole 442b in the direction of rotation R21 of the developing sleeve 441 at the time of image formation. In detail, the intermediate pole 442c is disposed at a position downstream of the first pole 442a and upstream of the second pole 442b in the direction of rotation R21 of the developing sleeve 441 at the time of image formation. The developer is carried to the outer peripheral surface of the developing sleeve 441 by the magnetic force of the intermediate pole 442c, and is transported in the direction of rotation of the developing sleeve 441 as the developing sleeve 441 rotates.

[0071] The intermediate pole 442c can be one or a plurality of poles. In the case where the intermediate pole 442c is a plurality of poles, the intermediate poles 442c adjacent to the first pole 442a and the second pole 442b, respectively, need to be of opposite magnetic polarity to the first pole 442a and the second pole 442b. Also, an odd number of intermediate poles 442c are disposed so that adjacent intermediate poles 442c are of opposite magnetic polarity to each other. In the present embodiment, the intermediate pole 442c is one, and is of opposite magnetic polarity to the first pole 442a and the second pole 442b.

[0072] [Embodiment]

[0073] Next, evaluation related to the recovery of the flying toner in the image forming apparatus 1 will be described. In this evaluation, 100,000 sheets of an image equivalent to a print rate of 20% with respect to the paper S were printed, and the recovery efficiency of the flying toner in the image forming apparatus 1 was confirmed. Also, printing was performed in a normal temperature and humidity environment (24°C / 40%) from the first sheet to the 70,000th sheet, and in a high temperature and humidity environment (28°C / 80%) from the 70,001st sheet to the 100,000th sheet.

[0074] Also, in the present evaluation, the flying toner recovery mode was executed every 4,000 sheets. In detail, the developing roller 44 was counter-rotated by the operation of the vibration generation portion 64 every 4,000 sheets, the developing voltage at this time was 150 V, and the surface potential of the photosensitive drum 21 was 20 V.

[0075] The pole configurations of the stationary magnet 442 are shown in Table 2. As shown in Table 2, in the present evaluation, the image forming apparatus 1 of the embodiment of the present application and the image forming apparatuses of the comparative examples, which differ from each other in the pole configuration of the stationary magnet 442, were prepared.

[0076] [Table 2]

[0077]

[0078] With regard to Table 2, the peak position of the magnetic force of the first pole 442a (N pole) of the stationary magnet 442 disposed at the opposite region of the photosensitive drum 21 is the position of angle 0 deg (reference position) in the embodiments, comparative example. In contrast, the position of the peak magnetic force of the middle pole 442c (S pole) in the stationary magnet 442 of the embodiment is the position of angle 46 deg along the rotation direction R21 of the developing sleeve 441 at the time of image formation. On the other hand, the stationary magnet of the comparative example does not have a middle pole. In addition, the position of the peak magnetic force of the second pole 442b (N pole) in the stationary magnet 442 of the embodiment is the position of angle 82 deg along the rotation direction R21 of the developing sleeve 441 at the time of image formation. The position of the peak magnetic force of the second pole (S pole) of the stationary magnet of the comparative example is the position of angle 80 deg along the rotation direction of the developing sleeve at the time of image formation. The evaluation results are shown in Table 3.

[0079] [Table 3]

[0080] Example Comparative example First filter toner trapping amount [g] 0.98 1.02 Drum toner adhesion amount [g] 0.88 0.63 Flying toner recovery efficiency 0.90 0.62

[0081] With regard to Table 3, for the "first filter toner capture amount", the weight of the first filter 621 was measured before and after the first filter 621 was vibrated by the vibration generation portion 64 after toner adhered to the first filter 621, and the amount of toner that fell from the first filter 62 was calculated. For the "drum-on toner adhesion amount", the amount of toner adhered to the outer circumferential surface of the photosensitive drum 21 was measured after the developing roller 44 was counter-rotated. Then, the "flying toner recovery efficiency" obtained as the ratio of the "drum-on toner adhesion amount" to the "first filter toner capture amount" was calculated, and evaluation was performed.

[0082] According to Table 3, the flying toner recovery efficiency of the image forming apparatus of the comparative example was 62%. In contrast, the flying toner recovery efficiency of the image forming apparatus 1 of the embodiment of the present application was 90%. That is, it was found that the image forming apparatus 1 of the embodiment of the present application was able to recover flying toner with an efficiency that was about 30% better than the image forming apparatus of the comparative example.

[0083] Thus, according to the configuration of the embodiment, the toner capture mechanism 60 for attracting and capturing flying toner is formed within the developing device 40, and the flying toner captured by the filter 62 can be recovered by the drum cleaning portion 23 via the developing roller 44 and the photosensitive drum 21.

[0084] In this case, in a case where the flying toner falls on the magnetic brush of the developer formed on the outer peripheral surface of the developing roller 44 and the wheat is erected, although it is sufficient to adhere to the vicinity of the front end of the magnetic brush, sometimes it adheres to the outer peripheral surface of the developing roller 44 by entering the gap of the magnetic brush. In this state, the flying toner becomes difficult to move to the photosensitive drum 21, and the recovery efficiency of the flying toner decreases. It is preferable that the flying toner adhere to the vicinity of the front end of the magnetic brush when moving to the opposing region of the photosensitive drum 21 along with the reverse rotation of the developing roller 44.

[0085] Therefore, according to the configuration of the embodiment, one intermediate pole 442c (S pole) is arranged between the first pole 442a (for example, N pole) of the stationary magnet 442 of the developing roller 44 which opposes the photosensitive drum 21 and the second pole 442b (N pole) which opposes the first filter 621.

[0086] Thus, when the developing roller 44 is reversely rotated, the magnetic pole on the outer peripheral surface of the developing roller 44 changes from the second pole 442b (N pole) which opposes the first filter 621 to the first pole 442a (N pole) which opposes the photosensitive drum 21 via the intermediate pole 442c (S pole). The magnetic brush rotates on the outer peripheral surface of the developing roller 44 while maintaining the state where the wheat is formed while moving to the circumferentially adjacent magnetic pole. That is, the flying toner which falls on the magnetic brush in the vicinity of the second pole 442b (N pole) can be carried to the vicinity of the front end of the magnetic brush by the rotation of the magnetic brush when moving to the first pole 442a (N pole) via the intermediate pole 442c (S pole) even if it adheres to the outer peripheral surface of the developing roller 44 by entering the gap of the magnetic brush.

[0087] As a result, the flying toner approaches the outer peripheral surface of the photosensitive drum 21 when moving to the opposing region of the photosensitive drum 21 along with the reverse rotation of the developing roller 44, and easily moves to the photosensitive drum 21. That is, the flying toner can be efficiently recovered via the photosensitive drum 21. Therefore, the toner flying in the image forming apparatus 1 can be suppressed by the configuration which realizes the downsizing.

[0088] In addition, as described above, one intermediate pole 442c is arranged. Therefore, by the simple configuration, the flying toner can easily approach the outer peripheral surface of the photosensitive drum 21 when moving to the opposing region of the photosensitive drum 21 along with the reverse rotation of the developing roller 44. That is, the flying toner can be further efficiently recovered.

[0089] Further, the control section 8 executes the flying toner recovery mode every predetermined 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 toner flying in the image forming apparatus 1 can be improved.

[0090] In addition, the developing agent for forming a toner image is a two-component developing agent containing a magnetic carrier and a toner. It is known that toner scattering from the developing container 50 easily occurs in the case of a two-component developing agent. Therefore, by executing the above scattered toner recovery mode in the image forming apparatus 1 using a two-component developing agent, toner scattering within the image forming apparatus 1 can be further efficiently suppressed.

[0091] In addition, the photosensitive drum 21 has a photosensitive layer formed of an amorphous silicon photosensitive body on the outer peripheral surface. It is known that the dielectric constant of the photosensitive layer formed of an amorphous silicon photosensitive body is high, and the toner charge amount is low. If the toner charge amount is low, toner scattering from the developing container 50 easily occurs. Therefore, by executing the above scattered toner recovery mode in the image forming apparatus 1 using a photosensitive drum 21 having an amorphous silicon photosensitive body, toner scattering within the image forming apparatus 1 can be further efficiently suppressed.

[0092] The above describes an embodiment of the present application, but the scope of the present application is not limited thereto, and various modifications can be applied to implement within the scope of the gist of the present application.

[0093] For example, in the above-described embodiment, the image forming apparatus 1 is a so-called tandem type color printing image forming apparatus that sequentially superimposes and forms images of multiple colors, but is not limited to such a model. The image forming apparatus can not be a tandem type color printing image forming apparatus, but can be a monochrome printing image forming apparatus.

Claims

1. An image forming apparatus characterized by comprising: Including: an image carrier on which an electrostatic latent image is formed on an outer peripheral surface; a charging section that charges the outer peripheral surface of the image carrier; a cleaning section that cleans the outer peripheral surface of the image carrier; a developing device that has a developing container that accommodates a developer containing toner supplied to the image carrier, a developer conveying member that is rotatably supported in a conveying chamber of the developing container, conveys the developer while stirring to circulate the developer, and a developer carrier that is opposed to the image carrier, is rotatably supported to the developing container, and supplies the toner in the conveying chamber to the image carrier; a voltage application section that applies a developing voltage to the developer carrier; and a control section that controls the image carrier, the charging section, the cleaning section, the developing device, and the voltage application section, the developing device is provided with a toner trapping mechanism, the toner trapping mechanism has: a duct that is connected to the conveying chamber, in which air in the conveying chamber flows; a filter that is located at a connection portion of the duct and the conveying chamber and is disposed above the developer carrier, traps the toner flowing from the conveying chamber into the duct; an exhaust fan that causes air in the conveying chamber to flow out to the outside via the duct; and a vibration generation section that vibrates the filter, the control section can execute a scattered 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 carrier to the image carrier, and the developer carrier is rotated in a direction opposite to that at an image forming time and the image carrier is rotated in the same direction as at the image forming time, whereby scattered toner that has fallen from the filter and adheres to an outer peripheral surface of the developer carrier is recovered by the cleaning section via the image carrier, the developer carrier has: a rotatable hollow cylindrical developing sleeve that carries the developer on an outer peripheral surface; and a fixed magnet that is fixedly arranged inside the developing sleeve, and a plurality of magnetic poles are arranged along a circumferential direction of the developing sleeve, the plurality of magnetic poles have: a first pole that is disposed in an opposed region to the image carrier in a rotation direction of the developing sleeve; a second pole that is disposed in an opposed region to the filter in the rotation direction of the developing sleeve; and at least one intermediate pole that is disposed between the first pole and the second pole in the rotation direction of the developing sleeve, the first pole and the second pole are the same magnetic polarity, the intermediate poles are disposed in an odd number such that the intermediate poles adjacent to the first pole and the second pole are of the opposite magnetic polarity to the first pole and the second pole, and the intermediate poles adjacent to each other are of the opposite magnetic polarity to each other.

2. The image forming apparatus according to claim 1, wherein the intermediate poles are disposed in one.

3. The image forming apparatus according to claim 1, wherein the control section executes the scattered toner recovery mode every predetermined number of printed sheets. ​ ​ ​ 4. The image forming apparatus according to claim 1, characterized in that the developer is a two-component developer including a magnetic carrier and the toner.

5. The image forming apparatus according to claim 1, characterized in that the image carrier has a photosensitive layer formed of an amorphous silicon photosensitive body on an outer peripheral surface.

6. The image forming apparatus according to any one of claims 1 to 5, characterized in that the filter includes: a first filter covering an air inlet opening to the entire area in a longitudinal direction of the conveying chamber to communicate the inside of the conveying chamber with the inside of the duct; and a second filter disposed on a downstream side in an air flow direction inside the duct than the first filter to cover an air flow cross section inside the duct.

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