Image forming apparatus

Abstract

The image forming apparatus according to the present application is configured to vibrate a filter during non-image forming, control a potential difference in a direction in which toner moves from a developer carrier to an image carrier, rotate the developer carrier in a direction opposite to that during image forming, and rotate the image carrier in the same direction as during image forming, thereby recovering the flying toner that has fallen from the filter and adhered to the outer circumferential surface of the developer carrier by the cleaning unit. The absolute value of the perpendicular magnetic force gradient of the relative position of the fixed magnet of the developer carrier with respect to the central portion of the filter in the rotation direction of the developing sleeve is 4.0 mT / ° or less.

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 and a printer, a device that supplies toner to an electrostatic latent image formed on the outer circumferential surface of a photoconductor or the like and develops the electrostatic latent image to form a toner image that is subsequently transferred onto a sheet is widely used. In order to continuously form a uniform image, the developer containing toner accommodated in a developing container is transported while being stirred in the developing container.

[0003] In the conventional image forming apparatus, there is a risk that toner scatters from the inside of the developing container to the outside, thereby contaminating the inside of the apparatus with the scattered toner. SUMMARY

[0004] An object of the present application is to provide an image forming apparatus that can suppress scattering of toner in the apparatus using a downsized configuration.

[0005] The image forming apparatus according to the first aspect 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 has a developing container, a developer conveying member, and a developer bearer. The developing container houses 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, and circulates the developer. The developer bearer is rotatably supported in the developing container opposite to the image bearer, 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 collection mechanism including an air passage, a filter, an exhaust fan, and a vibration generation section. The air passage is connected to the conveying chamber and allows air in the conveying chamber to flow. The filter is disposed above the developer bearer at a connection portion of the air passage and the conveying chamber, and collects the toner flowing from the conveying chamber into the air passage. The exhaust fan causes air in the conveying chamber to flow to the outside through the air passage. The vibration generation section vibrates the filter. The control section can execute a flying toner recovery mode in which, in a non-image forming period, the filter is vibrated by the vibration generation section, the charging section and the voltage application section are controlled in a manner that a potential difference in a direction in which the toner moves from the developer bearer to the image bearer is generated, the developer bearer is rotated in a direction opposite to a direction in which the developer bearer is rotated in an image forming period, and the image bearer is rotated in the same direction as the direction in which the image bearer is rotated in the image forming period, and flying toner that falls from the filter and adheres to an outer circumferential surface of the developer bearer is recovered by the cleaning section with the aid of the image bearer. The developer bearer has a developing sleeve and a stationary magnet. The developing sleeve is a rotatable hollow cylindrical member that carries the developer on an outer circumferential surface. The stationary magnet is fixed inside the developing sleeve so as to be non-rotatable, and a plurality of magnetic poles are arranged in a circumferential direction of the developing sleeve. An absolute value of a vertical magnetic gradient of a relative position of the stationary magnet with respect to a rotation direction of the developing sleeve from a central portion of the filter is 4.0 mT / ° or less.

[0006] According to the first aspect of the present invention, a toner collection mechanism for attracting and collecting flying toner can be formed in the developing device, and flying toner collected by the filter is recovered by the cleaning section with the aid of the developer bearer and the image bearer. Furthermore, according to the above-described configuration of the stationary magnet of the developer bearer, flying toner can be efficiently recovered with the aid of the image bearer. Thus, it is possible to suppress toner flying in the image forming apparatus with a downsized configuration. Attached Figure Description

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

[0008] Figure 2 It means Figure 1 A block diagram of the structure of an image forming apparatus.

[0009] Figure 3 yes Figure 1 A schematic cross-sectional front view of the area surrounding the image forming section of the image forming apparatus.

[0010] Figure 4 yes Figure 3 A vertical cross-sectional front view of the developing apparatus for the image forming section.

[0011] Figure 5 yes Figure 3 A horizontal cross-sectional top view of the developing apparatus for the image forming section.

[0012] Figure 6 yes Figure 3 A vertical cross-sectional side view of the developing apparatus for the image forming section.

[0013] Figure 7 yes Figure 3 The enlarged cross-sectional front view of the area surrounding the image forming section is an explanatory diagram of the toner recovery mode.

[0014] Figure 8 It means Figure 4 A graph showing the distribution of vertical magnetic force and the variation of vertical magnetic force gradient in the circumferential direction of the developing roller of the developing device.

[0015] Figure 9 It means Figure 8 A magnified view of the graph showing the distribution of vertical magnetic force and the variation of vertical magnetic force gradient in the circumferential direction of the developing roller. Detailed Implementation

[0016] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the following descriptions.

[0017] Figure 1 This is a schematic cross-sectional front view of the image forming apparatus 1 according to the embodiment. Figure 2 It means Figure 1 A block diagram of the configuration of the image forming apparatus 1. Figure 3 yes Figure 1Fig. 1 is a schematic cross-sectional front view of the image forming section 20 of the image forming apparatus 1 according to the present embodiment. The image forming apparatus 1 according to the present embodiment is a serial color printer that transfers toner images to a paper S using an intermediate transfer belt 31. The image forming apparatus 1 can be, for example, a so-called digital multifunction peripheral that has functions of printing, scanning (image reading), facsimile transmission, and the like.

[0018] As shown in Figs. 1 and 2, the image forming apparatus 1 has a paper feeding section 3, a paper feeding section 4, an exposure section 5, an image forming section 20, a transfer section 30, a fixing section 6, a paper discharge section 7, and a control section 8 provided in a main body 2. Figure 1 Figure 2 Figure 3

[0019] The paper feeding section 3 is disposed at the bottom of the main body 2. The paper feeding section 3 accommodates a plurality of papers S before printing and feeds out the papers S one by one at the time of printing. The paper feeding section 4 extends in the vertical direction along the side wall of the main body 2. The paper feeding section 4 conveys the papers S fed out from the paper feeding section 3 to the second transfer section 33 and the fixing section 6, and discharges the papers S after fixing from a paper discharge port 4a to the paper discharge section 7. The exposure section 5 is disposed above the paper feeding section 3. The exposure section 5 irradiates the image forming section 20 with laser light controlled in accordance with image data.

[0020] The image forming section 20 is disposed above the exposure section 5 and below the intermediate transfer belt 31. The image forming section 20 includes a yellow image forming section 20Y, a cyan image forming section 20C, a magenta image forming section 20M, and a black image forming section 20B. The four image forming sections 20 have the same basic structure. Therefore, in the following description, the identification marks representing the colors "Y", "C", "M", and "B" are omitted except for cases where it is necessary to particularly specify.

[0021] The image forming section 20 has a photosensitive drum (image carrier) 21 supported so as to be rotatable in a predetermined direction (clockwise direction in Figs. 1 and 2). The image forming section 20 also has a charging section 22, a developing device 40, and a drum cleaning section (cleaning section) 23 disposed around the photosensitive drum 21 in the direction of rotation thereof. In addition, the developing device 40 and the drum cleaning section 23 are disposed with the first transfer section 32 therebetween. Figure 1 Figure 3

[0022] ​​​​​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 at 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 develops the electrostatic latent image by supplying toner thereto, and forms a toner image. The four image forming sections 20 form toner images of different colors, respectively. The drum cleaning section 23 cleans the outer peripheral surface of the photosensitive drum 21 by removing 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. In this way, the image forming section 20 forms an image (toner image) that is subsequently transferred to the paper S.

[0023] The transfer section 30 includes 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 a ring-shaped intermediate transfer body on which the toner images formed by the four image forming sections 20 are sequentially superimposed and once transferred in the direction of rotation (counterclockwise direction in the drawing) of the intermediate transfer belt 31. The four image forming sections 20 are arranged in a so-called tandem manner in a line from the upstream side to the downstream side in the direction of rotation of the intermediate transfer belt 31. Figure 1

[0024] The primary transfer sections 32Y, 32C, 32M, 32B sandwich the intermediate transfer belt 31, and are disposed above the respective color image forming sections 20Y, 20C, 20M, 20B. The secondary transfer section 33 is disposed on the upstream side relative to the paper conveying direction of the paper feed section 4, and on the downstream side relative to the direction of rotation of the intermediate transfer belt 31, compared to the four image forming sections 20Y, 20C, 20M, 20B. The belt cleaning section 34 is disposed on the downstream side relative to the direction of rotation of the intermediate transfer belt 31, compared to the secondary transfer section 33.

[0025] 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 by the respective color primary transfer sections 32Y, 32C, 32M, 32B to the outer peripheral surface of the intermediate transfer belt 31. Furthermore, the toner images of the four image forming sections 20 are continuously superimposed and transferred to the intermediate transfer belt 31 at a prescribed timing as the intermediate transfer belt 31 rotates, and thus a color toner image in which yellow, cyan, magenta, and black toner images are superimposed is formed on the outer peripheral surface of the intermediate transfer belt 31.

[0026] ​The color toner image of the outer circumferential surface of the intermediate transfer belt 31 is transferred to the paper S that is fed by the paper feed section 4, in the secondary transfer nip section formed in the second 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 S.

[0027] The fixing section 6 is disposed above the second transfer section 33. The fixing section 6 fixes the toner image on the paper S by heating and pressing the paper S on which the toner image is transferred.

[0028] The paper discharge section 7 is disposed above the transfer section 30. The paper S on which the toner image is fixed and printed is fed to the paper discharge section 7. The printed paper (print) is taken out from above in the paper discharge section 7.

[0029] The control section 8 includes a CPU, an image processing section, a storage section, and other electronic circuits and electronic parts (none of which is shown). 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 stored in the storage section. The paper feed section 3, the paper feed section 4, the exposure section 5, the image forming section 20, the transfer section 30, and the fixing section 6 each receive an instruction from the control section 8 individually, and perform printing on the paper S in cooperation. The storage section is composed of, for example, a nonvolatile storage device such as a program ROM (Read Only Memory), a data ROM, and a volatile storage device such as a RAM (Random Access Memory).

[0030] In addition, the image forming apparatus 1, as shown in Figure 2 , further includes a voltage application section 12 and a current detection section 13.

[0031] 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, the voltage value, the polarity, the application time, and the like of the developing voltage applied to the developing roller 44 by the voltage application section 12.

[0032] The current detection section 13 detects the current flowing 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 about the current detected by the current detection section 13 from the current detection section 13.

[0033] Next, on the basis of Figure 2 and Figure 3 , the following Figure 4 , Figure 5 and Figure 6The constitution 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 section 20 of Figure 3 . In addition, since the basic constitution of the developing device 40 of each color is the same, the description and explanation of the identification mark of each color are omitted. Further, in the description, the "axial direction" represents 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 face depth direction, Figure 5 and Figure 6 the left-right lateral direction.

[0034] The developing device 40 supplies toner to the outer peripheral surface of the photosensitive drum 21. The developing device 40 is, for example, attachable and detachable with respect to the main body 2 of the image forming apparatus 1. 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 limiting member 45.

[0035] The developing container 50 is an elongated shape extending in the axial direction of the photosensitive drum 21, and the long side direction of the developing container 50 is horizontally arranged. That is, the long side direction of the developing container 50 is parallel to the axial direction of the photosensitive drum 21. As a developer containing toner supplied to the photosensitive drum 21, the developing container 50 accommodates, for example, a two-component developer containing toner and a magnetic carrier. The developer can be, for example, a magnetic one-component developer containing a magnetic toner or a non-magnetic one-component developer.

[0036] The developing container 50 has a partition 51, a first conveying chamber 52, a second conveying chamber 53, a first communication portion 54, and a second communication portion 55.

[0037] The partition 51 is provided at a lower portion of the inside of the developing container 50. The partition 51 is arranged at a substantially central portion in a direction intersecting the long side direction of the developing container 50 Figure 4 the left-right lateral direction, Figure 5 the up-down direction) of the developing container 50. The partition 51 is formed in a substantially plate shape extending in the long side direction and the up-down direction of the developing container 50. The partition 51 divides the inside of the developing container 50 in a direction intersecting the long side direction.

[0038] The first conveying chamber 52 and the second conveying chamber 53 are provided in the inside of the developing container 50. The first conveying chamber 52 and the second conveying chamber 53 are formed by dividing the inside of the developing container 50 by the partition 51. The first conveying chamber 52 and the second conveying chamber 53 are arranged in parallel at substantially the same height as each other.

[0039] The second conveying chamber 53 is positioned below the position of the developing roller 44 arranged in the developing container 50. The first conveying chamber 52 is arranged in a position farther from the developing roller 44 than the second conveying chamber 53 in the developing container 50. The first conveying chamber 52 is connected to a developer replenishing tube (not shown) by which the developer is replenished. The developer is conveyed in the first direction fl by the first conveying member 42 in the first conveying chamber 52. The developer is conveyed in the second direction f2 opposite to the first direction fl by the second conveying member 43 in the second conveying chamber 53.

[0040] The first and second communication portions 54 and 55 are arranged outside both end portions in the longitudinal direction of the partition portion 51, respectively. 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 substantially plate-shaped partition portion 51, that is, in a direction (left-right direction, up-down direction) intersecting the longitudinal direction of the partition portion 51. Figure 4 Figure 5

[0041] The first communication portion 54 communicates the first direction fl downstream end of the first conveying chamber 52 with the second direction f2 upstream end of the second conveying chamber 53. The first communication portion 54 conveys the 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 with the first direction fl upstream end of the first conveying chamber 52. The second communication portion 55 conveys the developer from the second conveying chamber 53 side toward the first conveying chamber 52 side.

[0042] The first conveying member 42 is arranged in the first conveying chamber 52. The second conveying member 43 is arranged in the second conveying chamber 53. The second conveying member 43 extends in parallel to the developing roller 44. The first and second conveying members 42 and 43 are supported by the developing container 50 so as to be rotatable around an axis extending in parallel to the developing roller 44 in the horizontal direction. The first and second conveying members 42 and 43 have the same basic configuration, and are provided with helical blades on the outer peripheral portion of the rotating shaft extending in the longitudinal direction of the developing container 50.

[0043] ​​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 agitating the developer in the direction of the axis of rotation within the first conveying chamber 52. 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 agitating the developer in the direction of the axis of rotation within the second conveying chamber 53. That is, the first conveying member 42 and the second conveying member convey the developer while agitating the developer in opposite directions to each other, and circulate the developer in a prescribed circulation direction.

[0044] The developing roller 44 is disposed above the second conveying member 43 within the developing container 50 so as to oppose the photosensitive drum 21. The developing roller 44 is supported by the developing container 50 so as to be rotatable about an axis extending in parallel with the axis of the photosensitive drum 21. The developing roller 44 includes, for example, a cylindrical developing sleeve 441 that rotates counterclockwise in Figure 3 and Figure 4 , and a fixed magnet 442 that is fixed within the developing sleeve so as to be non-rotatable (see Figure 4 ).

[0045] A portion of the outer peripheral surface of the developing roller 44 is exposed from the developing container 50 so as to oppose and be close to the photosensitive drum 21. The developing roller 44 carries toner on the outer peripheral surface, and supplies the toner to the outer peripheral surface of the photosensitive drum 21 in the opposing region of the developing roller 44 and 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 on the outer peripheral surface of the photosensitive drum 21, and forms a toner image.

[0046] A regulating member 45 is disposed on the upstream side of the developing roller 44 in the direction of rotation of the developing roller 44 in the opposing region of the developing roller 44 and the photosensitive drum 21. The regulating member 45 opposes the developing roller 44 and is disposed so as to be close to the developing roller 44, and a prescribed gap is provided between the front end of the regulating member 45 and the outer peripheral surface of the developing roller 44. The regulating member 45 extends across the entire region in the direction of the axis of the developing roller 44. The regulating member 45 regulates the thickness of the layer of 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.

[0047] The developer in the developing container 50 is circulated between the first and second conveying chambers 52 and 53 in a prescribed circulation direction by rotation of the first and second conveying members 42 and 43 via the first and second communication portions 54 and 55. At this time, the toner in the developing container 50 is agitated and charged to be carried to the outer peripheral surface of the developing roller 44. The toner carried on the outer peripheral surface of the developing roller 44 is conveyed to the opposing region of the developing roller 44 and the photosensitive drum 21 after the layer thickness is regulated by the regulating member 45. If a prescribed developing voltage is applied to the developing roller 44, the toner carried on the outer peripheral surface of the developing roller 44 moves to the outer peripheral surface of the photosensitive drum 21 in the opposing region by the potential difference between the potential of the surface (outer peripheral surface) of the photosensitive drum 21 and the potential of the developing roller 44. In this way, the latent image on the outer peripheral surface of the photosensitive drum 21 is developed with the toner.

[0048] Next, the specific structure of the developing device 40 will be described with reference to Figure 4 , Figure 5 and Figure 6 . In addition, the arrow representing the air flow direction fd in the ventilation passage 61 is described in Figure 4 and Figure 6 .

[0049] The developing device 40 is provided with a toner collection mechanism 60. The toner collection mechanism 60 has a ventilation passage 61, a filter 62, an exhaust fan 63, and a vibration generation portion 64. The filter 62 includes a first filter 621 and a second filter 622.

[0050] The ventilation passage 61 is disposed in proximity to the second conveying chamber 53. The ventilation passage 61 opposes the photosensitive drum 21 across the region where the developing roller 44 is disposed in the developing container 50 in a direction (left-right direction of the drawing, paper depth direction of the drawing) that intersects the longitudinal direction of the developing container 50. Figure 4 Figure 6 The ventilation passage 61 is connected to the second conveying chamber 53 at the upstream end in the air flow direction. The air in the second conveying chamber 53 flows to the ventilation passage 61. The ventilation passage 61 has a suction port 611 and an exhaust port 612.

[0051] The suction port 611 is the connection portion of the ventilation passage 61 to the second conveying chamber 53 and is disposed above the developing roller 44. That is, the suction port 611 is located at the upstream end in the air flow direction of the ventilation passage 61. The suction port 611 is open across the entire region in the longitudinal direction of the second conveying chamber 53. The suction port 611 is formed, for example, in a rectangular shape extending in the longitudinal direction of the second conveying chamber 53 and opposes the developing roller 44. The suction port 611 communicates between the inside of the second conveying chamber 53 and the inside of the ventilation passage 61. The air in the second conveying chamber 53 flows into the inside of the ventilation passage 61 through the suction port 611.

[0052] ​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 ventilation passage 61. Air in the second conveying chamber 53 is discharged from the ventilation passage 61 through the exhaust port 612. In addition, the ventilation passage 61 can be connected to other exhaust paths provided with a fan in the main body 2 at the exhaust port 612.

[0053] The exhaust fan 63 is connected to the exhaust port 612. If the exhaust fan 63 is driven, air in the second conveying chamber 53 is forcibly discharged to the outside through the ventilation passage 61. In other words, the exhaust fan 63 causes air in the second conveying chamber 53 to flow to the outside through the ventilation passage 61.

[0054] The first filter 621 is provided at the position of the connection of the ventilation passage 61 and the second conveying chamber 53, that is, the air inlet port 611. The first filter 621 has the same shape as the air inlet port 611, for example, a rectangular shape extending in the long direction of the second conveying chamber 53. The first filter 621 covers the air inlet port 611. That is, the first filter 621 opposes the developing roller 44. The first filter 621 is, for example, made of nonwoven fabric, and collects toner contained in air flowing from the second conveying chamber 53 into the ventilation passage 61.

[0055] The second filter 622 is provided at the downstream side in the air flow direction in the ventilation passage 61 than the first filter 621. The second filter 622 has the same shape as the cross section of the ventilation passage 61 in the direction intersecting the air flow direction, for example, a rectangular shape extending in the long direction of the second conveying chamber 53. The second filter 622 covers the air flow cross section in the ventilation passage 61. The second filter 622 is, for example, made of nonwoven fabric, and collects toner contained in air flowing in the ventilation passage 61 through the first filter 621.

[0056] (Table 1)

[0057] Pressure loss [mm Aq] First filter 0.42 Second filter 4.50

[0058] Table 1 shows an example of the performance of the first filter 621 and the second filter 622. The pressure loss at the time of measuring the upstream side static pressure and the downstream side static pressure with an air flow 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 collection efficiency and the 8 μm collection efficiency are both higher for the second filter 622 than for the first filter 621.

[0059] According to the configuration of the filter 62 described above, the first filter 621 can be configured so as not to collect toner in the second conveying chamber 53 in large amounts, and so as not to be easily clogged. Also, toner leakage to the outside of the developing container 50 can be prevented by the second filter 622.

[0060] The vibration generating portion 64 is disposed, for example, in contact with the back surface of the developing container 50. The vibration generating portion 64 includes, for example, a vibration motor, a control board, and other electronic circuits and electronic parts (all not shown). A weight is attached to the output shaft of the vibration motor so that the center of gravity of the weight is offset from the rotational axis of the output shaft.

[0061] 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 with the vibration generating portion 64, toner collected by the first filter 621 and adhered to the first filter 621 can be caused to fall off. Thus, the performance of the first filter 621 can be restored, and toner scattering within the image forming apparatus 1 can be continuously suppressed.

[0062] Further, the control portion 8 of the image forming apparatus 1 can execute a scattered toner recovery mode for recovering toner collected by the first filter 621 by the drum cleaning portion 23. Figure 7 is Figure 3 is a partial enlarged cross-sectional front view of the periphery of the image forming portion 20, and is a diagram for explaining the scattered toner recovery mode.

[0063] In addition, Figure 7 In the drawing, the direction of rotation R11 of the photosensitive drum 21 at the time of image formation, the direction of rotation R21 of the developing roller 44 at the time of image formation, and the direction of rotation R22 of the developing roller 44 at the time of the scattered toner recovery mode are illustrated by arrows. The direction of rotation R21 of the developing roller 44 and the direction of rotation R22 are in opposite directions to each other. Further, in order to facilitate explanation, Figure 7 In the drawing, toner (black spherical shape) that has fallen off from the first filter 621 is illustrated on the outer peripheral surface of the developing roller 44 and the outer peripheral surface of the photosensitive drum 21 below the first filter 621, but the actual toner is much smaller than Figure 7 toner (black spherical shape) illustrated in the drawing.

[0064] 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 in such a manner that a potential difference in the direction in which toner moves from the developing roller 44 to the photosensitive drum 21 is generated, and rotates the developing roller 44 in the direction opposite to the direction of rotation R22 at the time of image formation (the direction of rotation R22 of the developing roller 44 at the time of the scattered toner recovery mode), and rotates the photosensitive drum 21 in the same direction as the direction of rotation R11 at the time of image formation (the direction of rotation R11 of the photosensitive drum 21 at the time of the scattered toner recovery mode). Figure 7 Figure 7 ​rotates. Thus, in the scattered toner recovery mode, the scattered toner that falls 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 with the aid of the photosensitive drum 21. In addition, in the scattered toner recovery mode, no transfer bias is applied in the primary transfer portion 32, and the toner adhering to the outer peripheral surface of the photosensitive drum 21 does not move from the photosensitive drum 21 to the intermediate transfer belt 31.

[0065] Further, as shown in Figure 7 , the developing roller 44 has a developing sleeve 441 and a stationary magnet 442.

[0066] The developing sleeve 441 is hollow-cylindrical in shape extending in the axial direction of the developing roller 44, and is rotatably supported by the developing container 50. The outer peripheral surface of the developing sleeve 441 carries the developer.

[0067] The stationary magnet 442 is cylindrical in shape extending in the axial direction of the developing roller 44, and is fixed inside the developing sleeve 441 so as not to rotate. The stationary magnet 442 extends in the axial direction over the entire region of the developing sleeve 441.

[0068] The plurality of magnetic poles of the stationary magnet 442 are arranged in the circumferential direction of the developing sleeve 441. As the plurality of magnetic poles, the stationary magnet 442 has, for example, a suction pole, a restriction pole, a developing pole, a conveyance pole, and a peeling pole (all not shown).

[0069] The suction pole is disposed in the opposite region of the second conveyance chamber 53 (refer to Figure 4 ). The suction pole sucks up the developer conveyed in the second conveyance chamber 53 onto the outer peripheral surface of the developing sleeve 441. The suction pole can also be constituted by a magnetic pole common to the restriction pole.

[0070] The restriction pole is disposed in the opposite position of the limiting member 45 on the downstream side from the suction pole with respect to the rotation direction R21 of the developing sleeve 441 at the time of image formation. The restriction pole generates a peak magnetic force in the opposite position of the limiting member 45. The layer thickness of the developer carried on the outer peripheral surface of the developing sleeve 441 is limited by the magnetic force of the restriction pole and the limiting member 45.

[0071] The developing pole is disposed in the opposite region of the photosensitive drum 21 on the downstream side from the restriction pole with respect to the rotation direction R21 of the developing sleeve 441 at the time of image formation. For example, the developing pole generates a peak magnetic force in the region where the developing roller 44 is closest to the photosensitive drum 21. The developing pole causes only the toner to fly toward the photosensitive drum 21 by being applied with a developing voltage, and develops the latent image on the outer peripheral surface of the photosensitive drum 21.

[0072] The transport pole is disposed on the downstream side of the developing pole with respect to the direction of rotation R21 of the developing sleeve 441 during image formation. The developer is carried on the outer circumferential surface of the developing sleeve 441 by the magnetic force of the transport pole, and is transported in the direction of rotation of the developing sleeve 441 together with the rotation of the developing sleeve 441.

[0073] The peeling pole is disposed on the downstream side of the transport pole and on the upstream side of the suction pole with respect to the direction of rotation R21 of the developing sleeve 441 during image formation. The developer that reaches the region opposite the peeling pole is peeled off the outer circumferential surface of the developing sleeve 411 and falls into the second transport chamber 53.

[0074] Figure 8 is a graph showing the distribution of the vertical magnetic force and the change in the vertical magnetic force gradient in the circumferential direction of the developing roller 44 of the developing device 40 of Figure 4 Figure 9 is a partial enlarged view of the graph showing the distribution of the vertical magnetic force and the change in the vertical magnetic force gradient in the circumferential direction of the developing roller 44 of Figure 8

[0075] Figure 8 The horizontal axis of the graph of Figure 9 linearly represents the position of the circumferential direction on the developing roller 44 with the central angle. The position of the angle 0° is generally the developing pole, which is the region opposite the photosensitive drum 21 of the developing roller 44. Figure 8 Figure 9 The angle of the horizontal axis of the graph of Figure 9 is an enlarged view of the angle range of 40° to 120° of Figure 8

[0076] Figure 8 The left vertical axis of the graph of Figure 9 is the vertical magnetic force [mT], which corresponds to the data line of the solid line in the graph. The vertical magnetic force is the magnetic force with respect to the normal direction of the surface of the outer circumferential surface of the developing roller 44, and can be measured, for example, by a magnetic force measuring device. Figure 8 Figure 9 The right vertical axis of the graph of

[0077] ​​​​​In this embodiment, a magnetic force measuring device (GAUSS METER Model GX-100, manufactured by Japan Electromagnetic Measuring Instrument Co., Ltd.) is used. The developing roller 44 is mounted on an angle adjustment fixture, and the vertical magnetic force is measured while rotating at a certain angle. When the measurement accuracy is very high, the vertical magnetic force gradient can be obtained by dividing the difference in vertical magnetic force measured at different angles by the difference in measurement angle. However, when the measurement accuracy is low, the vertical magnetic force gradient cannot be obtained with high precision. Here, in this embodiment, the vertical magnetic force is measured by changing the measurement angle by 0.02° each time, and (the difference in vertical magnetic force of 0.08° / 0.08°) is used as "gradient 1" at the midpoint within this 0.08°. Furthermore, the average gradient of the data (2° / 0.02° = 100) within a 2° angle range of "gradient 1" is used as the vertical magnetic force gradient. The calculation of the vertical magnetic force gradient is shown in Table 2.

[0078] (Table 2)

[0079]

[0080] Table 2 shows that... Figure 8 The data for the angle range of 10.00° to 10.16° is used as an example. In Table 2, for example, gradient 1 (-5.00 mT / °) at angle 10.08° is obtained by dividing the difference (-0.40 mT) between the vertical magnetic force of 73.3 mT at angle 10.04° and the vertical magnetic force of 72.9 mT at angle 10.12° by 0.08°. In addition, the average gradient (-4.70 mT / °) at angle 10.08° is the average of the gradient 1 data (100 data points) for the 2° angle range of 9.08° to 11.08°, which is called the "vertical magnetic gradient".

[0081] Furthermore, the rotation direction of the fixed magnet 442 relative to the developing sleeve 441, and its relative position 442c with respect to the central portion 621c of the first filter 621 (see reference) Figure 4 and Figure 7 The absolute value of the vertical magnetic gradient is below 4.0 mT / °. In other words, the vertical magnetic gradient at position 442c, which is vertically below the center portion 621c of the first filter 621, relative to the rotation direction of the fixed magnet 442 relative to the developing sleeve 441, is in the range of -4.0 mT / ° to +4.0 mT / °.

[0082] (Example)

[0083] Next, the evaluation of toner dispersion within the image forming apparatus 1 will be explained. In this evaluation, an image equivalent to a 20% print rate was printed on paper S, and 100,000 sheets were printed, confirming toner dispersion within the image forming apparatus 1. Furthermore, this evaluation was conducted by printing sheets 1 to 70,000 at normal temperature and humidity (24°C / 40%), and sheets 70,001 to 100,000 at high temperature and humidity (28.5°C / 80%).

[0084] Furthermore, in this evaluation, a toner recirculation mode is implemented every 4000 prints. Specifically, every 4000 prints, the vibration generating unit 64 is activated, causing the developing roller 44 to reverse. At this time, the developing voltage is 150V, and the surface potential of the photosensitive drum 21 is 20V.

[0085] The magnetic pole configuration of the fixed magnet 442 is shown in Table 3. As shown in Table 3, in this evaluation, an image forming apparatus 1 of the embodiments of the present invention with different magnetic pole configurations of the fixed magnet 442, as well as image forming apparatuses of Comparative Examples 1 and 2, were prepared.

[0086] (Table 3)

[0087]

[0088] Here, in Figure 9 In the case of fixed magnet 442, the vertical magnetic gradient is greater than +4.0 mT / ° in the range A of angle 52.14° to 68.32°, greater than -4.0 mT / ° and less than +4.0 mT / ° in the range B of angle 68.34° to 91.34°, and less than -4.0 mT / ° in the range C of angle 91.36° to 100.56°.

[0089] Furthermore, regarding Table 3, in the image forming apparatus 1 of the embodiment, the vertical magnetic gradient of the relative position 442c of the fixed magnet 442 and the central portion 621c of the first filter 621 is -4.0 mT / ° or more and +4.0 mT / ° or less. Figure 9 Range B). In the image forming apparatus of Comparative Example 1, the vertical magnetic gradient of the relative position 442c of the fixed magnet 442 with respect to the central portion 621c of the first filter 621 is greater than +4.0 mT / °. Figure 9 Range A). In the image forming apparatus of Comparative Example 2, the vertical magnetic gradient of the relative position 442c of the fixed magnet 442 and the central portion 621c of the first filter 621 is less than -4.0 mT / °. Figure 9 The range is C). The evaluation results are shown in Table 4.

[0090] (Table 4)

[0091]

[0092] Regarding Table 4, the toner scattering confirmation was visually verified to assess the toner scattering status within the image forming apparatus. The criteria for "toner scattering confirmation" are: "Good" if no toner scattering is detected and the apparatus remains clean; and "Bad" if toner scattering is detected and the apparatus is contaminated by scattered toner.

[0093] As shown in Table 4, the image forming apparatuses of Comparative Examples 1 and 2 exhibit toner dispersion in high-temperature and high-humidity environments. In contrast, the image forming apparatus 1 according to an embodiment of the present invention does not exhibit toner dispersion in both normal-temperature and normal-humidity environments and high-temperature and high-humidity environments.

[0094] Thus, according to the configuration of the embodiment, a toner collection mechanism 60 for attracting and collecting scattered toner is formed in the developing apparatus 40, and the scattered toner collected by the filter 62 can be recovered by means of the developing roller 44 and the photosensitive drum 21 using the drum cleaning section 23.

[0095] Here, under high temperature and high humidity conditions, the charge of the toner tends to decrease easily, and the amount of toner scattering increases. Furthermore, the perpendicular magnetic gradient of the relative position 442c between the fixed magnet 442 and the central portion 621c of the first filter 621 is greater than +4.0 mT / °. Figure 9 Range A) and in cases where it is less than -4.0 mT / ° ( Figure 9 Within range C), the magnetic brushes of the developer formed on the outer peripheral surface of the developing roller 44 opposite to the first filter 621 are in a tilted state, for example, towards the circumference of the developing roller 44. There are no gaps between the tilted magnetic brushes.

[0096] In the image forming apparatus of Comparative Examples 1 and 2, toner that has fallen from the first filter 621 and adhered to the outer peripheral surface of the developing roller 44 falls onto the tilted magnetic brush. As a result, the toner cannot be drawn into the gap between the magnetic brushes, and a large amount of toner will scatter, contaminating the apparatus.

[0097] Here, according to the configuration of the embodiment, the absolute value of the vertical magnetic gradient of the fixed magnet 442 relative to the central portion 621c of the first filter 621 is less than or equal to 4.0 mT / ° (more than -4.0 mT / ° and less than +4.0 mT / °). Figure 9 Figure 9 (range B). At this time, the magnetic brushes of the developer formed on the outer peripheral surface of the developing roller 44 opposite to the first filter 621 are in a state of being upright along the normal direction relative to the outer peripheral surface of the developing roller 44. A gap is generated between the upright magnetic brushes.

[0098] In the image forming apparatus 1 of the embodiment, the flying toner that falls from the first filter 621 and adheres to the outer peripheral surface of the developing roller 44 falls onto the magnetic brush in the erected state. In this way, the flying toner can be taken into the gap between the magnetic brushes, and the flying of the toner can be suppressed. That is, the image forming apparatus 1 of the embodiment can cause a large amount of the flying toner that falls from the first filter 621 to adhere to the outer peripheral surface of the developing roller 44, and can efficiently recover the flying toner with the photosensitive drum 21. Therefore, a small-sized configuration is realized, and the flying of the toner in the image forming apparatus 1 can be suppressed.

[0099] In addition, it is preferable that the absolute value of the perpendicular magnetic force gradient of the relative position of the entire first filter 621 with respect to the rotation direction of the developing sleeve 441 be 4.0 mT / ° or less. According to the configuration, the magnetic brush of the developer can be brought into the erected state over a wide range of the relative area of the first filter 621 on the outer peripheral surface of the developing roller 44. In this way, the effect of taking the flying toner that falls from the first filter 621 into the gap between the magnetic brushes can be improved. Therefore, the flying toner can be efficiently recovered.

[0100] 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 the configuration, the flying toner collected by the filter 62 can be periodically recovered by the drum cleaning section 23 with the developing roller 44 and the photosensitive drum 21. Therefore, the suppression effect of the flying of the toner in the image forming apparatus 1 can be improved.

[0101] In addition, the developer for the formation of the toner image is a two-component developer including a magnetic carrier and toner. It has been known that, in the case of the two-component developer, the flying of the toner is easily generated from the developing container 50. Therefore, by executing the above-described flying toner recovery mode in the image forming apparatus 1 using the two-component developer, the flying of the toner in the image forming apparatus 1 can be further effectively suppressed.

[0102] In addition, the photosensitive drum 21 has a photosensitive layer formed of an amorphous silicon photosensitive body on the outer peripheral surface. It has been known that the photosensitive layer formed of the amorphous silicon photosensitive body has a high dielectric constant and a low toner charge amount. If the toner charge amount is low, the flying of the toner is easily generated from the developing container 50. 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 photosensitive body, the flying of the toner in the image forming apparatus 1 can be further effectively suppressed.

[0103] The above describes the embodiment of the present application, but the scope of the present application is not limited thereto, and various modifications can be added within the scope of the idea of the present application.

[0104] For example, according to the above-described embodiment, the image forming apparatus 1 is a so-called tandem type image forming apparatus for color printing that sequentially superimposes multicolor images, but is not limited to this type. The image forming apparatus can be a non-tandem type image forming apparatus for color printing or an image forming apparatus for black-and-white printing.

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 containing a developer, the developer including a toner supplied to the image carrier; a developer delivery member rotatably supported in a delivery chamber of the developing container, which delivers and circulates the developer while agitating it; and a developer carrier rotatably supported in the developing container opposite to the image carrier, 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 unit. The developing apparatus includes a toner collection mechanism, which comprises: A ventilation duct, connected to the conveying chamber, allows air circulation within the conveying chamber; A filter, disposed at the connection between the ventilation duct and the delivery chamber and above the developer carrier, is used to collect the toner flowing from the delivery chamber into the ventilation duct; An exhaust fan, through the ventilation duct, directs air from the delivery chamber to the outside; and The vibration generator causes the filter to vibrate. The control unit can execute a scattered toner recovery mode. When not forming an image, the vibration generating unit vibrates the filter to generate a potential difference that moves the toner from the developer carrier to the image carrier. This controls the charged unit and the voltage applying unit, and causes the developer carrier to rotate in the opposite direction to image formation and the image carrier to rotate in the same direction. Scattered toner that has fallen from the filter and adhered to the outer periphery of the developer carrier is recovered by the cleaning unit via the image carrier. The developer carrier includes: A developing sleeve, a rotatable hollow cylindrical developing sleeve that carries the developer on its outer peripheral surface; and A fixed magnet is fixed inside the developing sleeve and cannot rotate; multiple magnetic poles are arranged circumferentially along the developing sleeve. The absolute value of the vertical magnetic gradient of the fixed magnet relative to the rotation direction of the developing sleeve and its position relative to the center of the filter is less than 4.0 mT / °.

2. The image forming apparatus according to claim 1, characterized in that, The absolute value of the vertical magnetic gradient of the fixed magnet relative to the direction of rotation of the developing sleeve and its relative position to the entire area of ​​the filter is less than 4.0 mT / °.

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

4. 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.

5. 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.

6. The image forming apparatus according to any one of claims 1 to 5, characterized in that, The filter includes: A first filter covers the air intake, which is an opening covering the entire length of the conveying chamber and connects the conveying chamber to the ventilation duct; and The second filter is disposed downstream of the first filter in the airflow direction within the ventilation duct, and covers the airflow profile within the ventilation duct.

Images