Patent Application
20190018345
This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2017-138299, filed Jul. 14, 2017, the entire contents of which are incorporated herein by reference.
Embodiments described herein relate generally to a developing device and an image forming apparatus.
Conventionally, there is an image forming apparatus such as a multi-function peripheral (hereinafter referred to as a “MFP”) and a printer. The image forming apparatus has a developing device accommodating a developer therein. The developing device includes a developing roller. If air enters the developing device due to rotation of the developing roller, the pressure in the developing device increases. As the pressure in the developing device increases, the air containing a toner in the developing device may spout from the developing device. If the air containing the toner spouts from the developing device, the toner scatters outside the developing device and there is a possibility that the functional components such as a charging device become contaminated with the toner.
In accordance with an embodiment, a developing device includes a housing having an opening in a wall thereof, a hollow developing roller arranged within the housing which is rotatable about an axis of rotation, a magnetic pole structure disposed within the developing roller and at least a portion thereof facing the opening in the housing, a gap forming member located within the housing at a location downstream the opening in the housing and forming a first gap with the developing roller and forming a second gap with the housing, and a blocking member arranged in the first gap. The housing and the gap forming member form a first opening and a second opening spaced from the first opening across the second gap between the gap forming member and the housing, such that the first opening is located farther from the opening in the wall of the housing than the second opening, and the width, in the axis of rotation direction of the developing roller, of the first opening is larger than that of the second opening. Hereinafter, an image forming apparatus of an embodiment is described with reference to the accompanying drawings. Further, in each figure, the same numerals are applied to the same components.
The image forming apparatus 1 is provided with a display section 110, an image reading section 120, an image forming section 130 and a sheet tray 140.
The display section 110 operates as an output interface to display characters and images. The display section 110 also operates as an input interface to receive an instruction from a user. For example, the display section 110 is a touch panel-type liquid crystal display.
For example, the image reading section 120 is a color scanner. In the color scanner, there is a CIS (Contact Image Sensor) and a CCD (Charge Coupled Device). The image reading section 120 reads the image formed on the sheet with a sensor to generate the digital data of the image file.
The image forming section 130 forms an image on the sheet with the toner. The image forming section 130 forms the image based on image data of the image file read by the image reading section 120 or image data received from an external device. For example, the image formed on the sheet is an output image referred to as hard copy, printout and the like.
The sheet tray 140 supplies the sheet used for image output to the image forming section 130.
As examples of the toner, there is a decolorable toner, a non-decolorable toner (normal toner) and a decorative toner. The decolorable toner has decolorable characteristics due to external stimulus. “Decolorable” refers to a processing of making an image formed with a color (containing not only chromatic colors but also achromatic colors such as white, black and the like) different from a base color of the sheet invisible visually. For example, the external stimulus includes temperature, light with a specific wavelength and pressure. In the present embodiment, the decolorable toner is decolored upon reaching a specific decolorable temperature or higher. The decolorable toner develops a color upon reaching a specific restoration temperature or lower after being decolored.
The decolorable toner may be optional toner as long as it has the foregoing characteristics. For example, a coloring agent of the decolorable toner may be leuco dye. The decolorable toner may be a proper combination of a developer or a decolorable agent, discoloration-temperature regulator and the like.
Further, a fixing temperature of the decolorable toner is lower than that of the non-decolorable toner. Here, the fixing temperature of the decolorable toner means a temperature of a heat roller 40 in a decolorable toner mode described later. The fixing temperature of the non-decolorable toner means a temperature of the heat roller 40 in a monochrome toner mode or a color toner mode described later.
The fixing temperature of the decolorable toner is lower than a temperature of a decoloring processing of the decolorable toner. Here, a temperature of the decoloring processing of the decolorable toner means the temperature of the heat roller 40 in the decoloring mode described later.
The image forming apparatus 1 is provided with a scanner section 2, an image processing section 3, an exposure section 4, an intermediate transfer body 10, a cleaning blade 11, image forming sections 12˜16, primary transfer rollers 17-1˜17-5, a sheet feed section 20, a secondary transfer section 30, a fixing device 32, a sheet discharge section 33 and a controller (not shown). Hereinafter, if all the primary transfer rollers are not distinguished, they are simply represented as a primary transfer roller 17.
In the following description, since the sheet is conveyed from the sheet feed section 20 to the sheet discharge section 33, the sheet feed section 20 side is set as an upstream side with respect to a sheet conveyance direction Vs and the sheet discharge section 33 side is set as a downstream side with respect to the sheet conveyance direction Vs.
Transfer processes in the image forming apparatus 1 include a first transfer process and a second transfer process. In the first transfer process, the primary transfer roller 17 transfers an image by the toner on a photoconductive drum of each image forming section onto the intermediate transfer body 10. In the second transfer process, the secondary transfer section 30 transfers the image by the toner of each color laminated on the intermediate transfer body 10 onto the sheet.
The scanner section 2 reads the image formed on the sheet which is a scanned object. For example, the scanner section 2 reads the image on the sheet to generate image data of three primary colors, i.e., red (R), green (G) and blue (B). The scanner section 2 outputs the generated image data to the image processing section 3.
The image processing section 3 converts the image data to color signals of respective colors. For example, the image processing section 3 converts the image data to image data (color signals) of four colors, i.e., yellow (Y), magenta (M), cyan (C) and black (K). The image processing section 3 controls the exposure section 4 based on the color signal of each color.
The exposure section 4 irradiates (exposes) the photoconductive drum of the image forming section with light. The exposure section 4 is provided with an exposure light source such as a laser, an LED and the like.
The intermediate transfer body 10 is an endless belt. The intermediate transfer body 10 rotates in an arrow A direction shown in
The cleaning blade 11 removes the toner adhering to the intermediate transfer body 10 after the toner image is transferred to a sheet. For example, the cleaning blade 11 is a plate-like member. For example, the cleaning blade 11 is made from resin such as urethane resin.
The image forming sections 12˜16 form images with toner of respective colors (five colors in the example shown in
The primary transfer roller 17 (17-1˜17-5) is used at the time of transferring the image by the toner formed by each of the image forming sections 12˜16 onto the intermediate transfer body 10.
The sheet feed section 20 feeds the sheet.
The secondary transfer section 30 is provided with a secondary transfer roller 30a and an opposed secondary transfer roller 30b. The secondary transfer section 30 transfers the image, using the toner formed on the intermediate transfer body 10, onto the sheet.
In the secondary transfer section 30, the intermediate transfer body 10 contacts the secondary transfer roller 30a. From the viewpoint of improving a sheet jam, the intermediate transfer body 10 may be separated from the secondary transfer roller 30a.
The fixing device 32 fixes the image of the toner transferred onto the sheet by heating and pressurizing the toner image. The sheet on which the image is fixed by the fixing device 32 is discharged from the sheet discharge section 33 to the outside of the apparatus.
Next, the image forming sections 12˜16 are described. The image forming sections 12˜15 respectively house the toner of respective colors corresponding to four colors for color printing. The four colors for color printing include yellow (Y), magenta (M), cyan (C) and black (K). The toner of the four colors for color printing is the non-decolorable toner. The image forming section 16 houses the decolorable toner. The image forming sections 12˜15 and the image forming section 16 have the same constitution except that the toner housed therein is different. Thus, the image forming section 12 is described representing the image forming sections 12˜16, and the description of the other image forming sections 13˜16 is omitted as redundant.
The image forming section 12 is provided with a developing device 12a, formed for example as a replaceable cartridge, a photoconductive drum 12b, a charging device 12c and a cleaning blade 12d.
The developing device 12a houses a developer. The toner is included in the developer. The developing device 12a enables the toner to adhere to the photoconductive drum 12b. For example, the toner is used as a one-component developer or as a two-component developer in combination with a carrier. For example, an iron powder or a polymer ferrite particle having a particle diameter of several tens of μm is used as the carrier. In the embodiment, a two-component developer containing a non-magnetic toner and the iron powder or a polymer ferrite is used.
The photoconductive drum 12b is one of concrete examples of an image carrier (image carrying module). The photoconductive drum 12b includes a photoconductor (photoconductive area) on the outer peripheral surface thereof. For example, the photoconductor is an organic photoconductor (OPC).
The charging device 12c uniformly charges the surface of the photoconductive drum 12b.
The cleaning blade 12d removes the toner adhering to the photoconductive drum 12b.
Next, the schematic operations of the image forming section 12 are described.
The photoconductive drum 12b is charged to a predetermined potential by the charging device 12c. Next, light is emitted from the exposure section 4 to the photoconductive drum 12b. In this way, the electric potential at the area on the photoconductive drum 12b irradiated with the light changes. Through the change, an electrostatic latent image is formed on the surface of the photoconductive drum 12b. The electrostatic latent image on the surface of the photoconductive drum 12b is developed by the developer in the developing device 12a. In other words, an image (hereinafter, referred to as a “developed image”) developed by the toner is formed on the surface of the photoconductive drum 12b.
The developed image formed on the surface of the photoconductive drum 12b is transferred onto the intermediate transfer body 10 by the primary transfer roller 17-1 on the side thereof opposite from the photoconductive drum 12b (first transfer process).
Next, the first transfer process by the image forming apparatus 1 is described. Firstly, the primary transfer roller 17-1 opposite to the photoconductive drum 12b caused transfer of the developed image on the photoconductive drum 12b onto the intermediate transfer body 10. Next, the primary transfer roller 17-2 opposite to a photoconductive drum 13b causes transfer of the developed image on the photoconductive drum 13b onto the intermediate transfer body 10. Such a processing is also carried out for photoconductive drums 14b, 15b and 16b. At this time, the developed images on the photoconductive drums 12b˜16b are respectively transferred onto the intermediate transfer body 10 to overlap with each other. Thus, the developed images represented as the toner of respective colors are overlapped while being transferred onto the intermediate transfer body 10 after passing through the image forming section 16.
However, in a case in which image formation using only the non-decolorable toner is carried out, the image forming sections 12˜15 operate. Through such an operation, the developed images using only the non-decolorable toner are formed on the intermediate transfer body 10. Further, in a case in which image formation using only the decolorable toner is carried out, the image forming section 16 operates. Through such an operation, the developed image using only the decolorable toner is formed on the intermediate transfer body 10.
Next, the second image transfer process is described. A voltage (bias) is applied to the secondary transfer roller 30a opposite secondary transfer roller 30b. Thus, an electric field is generated between the secondary transfer roller 30b and the secondary transfer roller 30a. As a result of the electric field, the secondary transfer section 30 transfers the developed image formed on the intermediate transfer body 10 onto a sheet passing between the intermediate transfer body and the secondary transfer roller 30a.
The fixing device 32 is described below.
As shown in
Firstly, the heat roller 40 which is a heating unit is described.
The heat roller 40 is arranged at the downstream side of the image forming section 130 (specifically, the secondary transfer section 30 shown in
The fixing device 32 is further provided with a heat source (not shown) for heating the heat roller 40. For example, the heat source may be a resistance heat generating body such as a thermal head, a ceramic heater, a halogen lamp, an electromagnetic induction heating unit and the like. The heat source may be arranged inside the heat roller 40 or outside the heat roller 40.
The pressure unit 50 is described below.
The pressure unit 50 is provided with a plurality of rollers 51 and 52, a belt 53 (rotating body) and a pressure pad 54 (pressure member).
A plurality of the rollers 51 and 52 is arranged at the inside of the belt 53. In the embodiment, a plurality of the rollers 51 and 52 is composed of a first roller 51 and a second roller 52. A plurality of the rollers 51 and 52 may be the same roller or different rollers.
A plurality of the rollers 51 and 52 is rotatable respectively around a plurality of rotation axes 51a and 52a parallel to the first axis 40a. A plurality of the rollers 51 and 52 is arranged at positions contributing to formation of a nip 41.
The first roller 51 is arranged at the upstream side in the sheet conveyance direction Vs with respect to the second roller 52. The first roller 51 is formed into a cylindrical shape. For example, the first roller 51 is a roller made from metal such as iron. The first roller 51 is rotatable around the first rotation axis 51a parallel to the first axis 40a. The first rotation axis 51a refers to the central axis of the first roller 51.
The second roller 52 is arranged at the downstream side in the sheet conveyance direction Vs with respect to the first roller 51. The second roller 52 is formed into a cylindrical shape. For example, the second roller 52 is a roller made from metal such as iron. The second roller 52 is rotatable around the second rotation axis 52a parallel to the first axis 40a. The second rotation axis 52a refers to the central axis of the second roller 52.
The belt 53 faces the heat roller 40. The belt 53 is stretched over the first roller 51 and the second roller 52. The belt 53 is formed into an endless shape.
The belt 53 is provided with a base layer 53a and a release layer (not shown). For example, the base layer 53a is formed by polyimide resin (PI). For example, the release layer is formed by fluorine resin such as tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA). The layer structure of the belt 53 is not limited. A film-like member is included in the belt 53.
The pressure pad 54 is formed into a right-angled parallelepiped shape. For example, the pressure pad 54 is formed by a resin material such as heat-resistant PPS (Polyphenylene Sulfide Resin), LCP (Liquid Crystal Polymer), PF (Phenol Resin) and the like. The pressure pad 54 is arranged at a position opposite to the heat roller 40 across the belt 53. The pressure pad 54 is energized towards the heat roller 40 through an energization member such as a spring (not shown). The pressure pad 54 abuts against the inner peripheral surface of the belt 53 to push the belt 53 against the heat roller 40 to form the nip 41. In other words, the pressure pad 54 presses the inner peripheral surface of the belt 53 towards the heat roller 40 to form the nip 41 between the belt 53 and the heat roller 40.
The rotation direction of the heat roller 40 is described below.
The heat roller 40 rotates in an arrow R1 direction driven by a motor (not shown). The heat roller 40 rotates in the arrow R1 direction independently of the pressure unit 50.
The belt 53 is driven by the heat roller 40 to rotate in an arrow R2 direction. The belt 53 is driven to rotate by abutting against the outer peripheral surface of the heat roller 40 rotating in the arrow R1 direction.
The first roller 51 is driven by the belt 53 to rotate in an arrow R3 direction. The second roller 52 is driven by the belt 53 to rotate in an arrow R4 direction. The first roller 51 and the second roller 52 are driven to rotate by abutting against the inner peripheral surface of the belt 53 rotating in the arrow R2 direction.
Next, types of the image forming processing carried out by the image forming apparatus 1 (refer to
The kind of mode in which the image formation is carried out can be selected according to an operation of the user on the display section 110 of the image forming apparatus 1.
In the monochrome toner mode, the image forming section using the non-decolorable toner of black (K) operates to form an image. The monochrome toner mode is selected in a case in which the user wants to print a general monochrome image. For example, the monochrome toner mode is used in a case in which the user wants to keep a paper as important data without reusing the paper.
In the color toner mode, four image forming sections respectively using the non-decolorable toner of yellow (Y), magenta (M), cyan (C) and black (K) operate to form images. The color toner mode is selected in a case in which the user wants to print a color image.
In the decolorable toner mode, only the image forming section using the decolorable toner operates to form an image. The decolorable toner mode is selected in a case in which the user wants to reuse a paper on which an image is formed.
The fixing device 32 is controlled in a fixing mode and a decoloring mode. In the fixing mode, the toner image is fixed on the sheet. In the decoloring mode, the toner image is decolored from the sheet. In the decoloring mode, the temperature of the heat roller 40 is higher than that of the heat roller 40 in the fixing mode. The controller (not shown) operates the fixing device 32 at least two or more target temperatures. Specifically, two target temperatures of the fixing device 32 are stored in a memory (not shown). The controller calls out the target temperature from the memory according to the selected mode and operates the fixing device 32 at that temperature. The two target temperatures are a first temperature and a second temperature. Here, the first temperature is a temperature in the decoloring mode. The second temperature is a temperature in the fixing mode. The second temperature is lower than the first temperature. As shown in
Next, the developing device 12a is described.
As shown in
The housing 60 houses the developer. The developer is composed of a carrier which is a magnetic body and the toner which is the coloring material. At the inside of the housing 60, the first mixer 61 and the second mixer 62 are arranged. At a side facing the photoconductive drum 12b (refer to
As shown in
In the housing 60, a first chamber 60a in which the first mixer 61 is arranged is formed. In the housing 60, a second chamber 60b in which the second mixer 62 is arranged is formed. The housing 60 is provided with a partition wall 65 for partitioning the first chamber 60a and the second chamber 60b. The first chamber 60a and the second chamber 60b are adjacent to each other across the partition wall 65. Side openings 60c and 60d for circulating the developer between the first chamber 60a and the second chamber 60b are formed at the opposite ends, in a rotation axis direction Vg, of the developing roller 63 in the housing 60. That is, the length of the partition 65 is shorter than the internal space of the housing 60 in the rotation axis direction Vg. According to this configuration, side openings 60c and 60d are formed between ends of the partition 65 and internal surfaces of the housing 60. The developer contained in the housing 60 can circulate between the first chamber 60a and the second chamber 60b through the side openings 60c and 60d. Hereinafter, the rotation axis direction Vg of the developing roller 63 is also referred to as a “roller axial direction Vg”.
As shown in
The developing roller 63 includes a shaft 63a, a plurality of magnetic pole sections N1, S1, N2, N3 and S2, and a sleeve 63b.
The shaft 63a extends in the roller axial direction Vg (refer to
A plurality of the magnetic pole sections N1, S1, N2, N3 and S2 is fixed to the shaft 63a. A plurality of the magnetic pole sections N1, S1, N2, N3 and S2 is fixed at fixed positions at intervals in a circumferential direction of the shaft 63a. For example, the magnetic pole sections N1, S1, N2, N3 and S2 are magnets.
The magnetic pole sections N1, S1, N2, N3 and S2 are a development pole N1, a first conveyance pole S1, a peeling pole N2, a grip pole N3 and a second conveyance pole S2. The development pole N1 faces the photoconductive drum 12b across the sleeve 63b to enable the developer carried on the developing roller 63 to approach the photoconductive drum 12b (refer to
The first conveyance pole S1 is a magnetic pole section in the housing which is positioned inside the housing 60 at the most upstream side of the roller rotation direction J1. The first conveyance pole S1 is positioned at the most upstream side in the roller rotation direction J1 at the inside of the housing 60 which is on the downstream side of the roller rotation direction J1 with respect to the position where the developing roller 63 faces the photoconductive drum 12b (refer to
The sleeve 63b is formed into a cylindrical shape including the shaft 63a and the plurality of the magnetic pole sections N1, S1, N2, N3, and S2 therein. The sleeve 63b is rotatable with respect to the magnetic pole sections N1, S1, N2, N3, and S2 by a driving source (not shown). The sleeve 63b rotates counterclockwise (in arrow J1 direction). In
The developer moves, along with the developing roller 63, by the rotation of the sleeve 63b. The developer on the developing roller can be lifted from the developing roller by magnetic force at the time of passing over the magnetic pole sections N1, S1, N2, N3 and S2. By the lifting of the developer, the toner is separated from the developer and a toner cloud occurs. The toner cloud contributes to toner scattering.
Developer in the second chamber 60b becomes adhered to the developing roller 63 by virtue of the magnetic force of the grip pole N3. The developer attached to the developing roller 63 is conveyed to the development pole N1, after passing the second conveyance pole S2. The development pole N1 forms a developing area. In the developing area, the toner contained in the developer moves from the developing roller 63 to the photoconductive drum 12b (refer to
The spacing between a doctor blade 66 of the opening 60h in the housing 60 and the surface of the developing roller 63 regulates the layer thickness of the developer carried by the developing roller 63.
The shielding section 64 blocks the flow of the air from the developing device 12a to the photoconductive drum 12b (refer to
The gap forming member 71 forms a first gap G1 with the developing roller 63. The gap forming member 71 faces the developing roller 63 across the first gap G1. The gap forming member 71 is positioned at the opposite side of the developing roller 63 from the second mixer 62. The gap forming member 71 forms a second gap G2 between itself and the housing 60. The gap forming member 71 faces the housing 60 across the second gap G2. Hereinafter, a portion 73 of the housing 60 which faces the gap forming member 71 through the second gap G2 is also referred to as a “casing main body 73”. The gap forming member 71 extends in the roller axial direction Vg (refer to
As shown in
The casing main body 73 is formed into a plate shape extending in the roller axial direction Vg. The holding section 81 extends from the casing main body 73 towards the gap forming member 71 (refer to
As shown in
As shown in
The blocking member 72 is arranged at a position facing the first conveyance pole S1 which is the magnetic pole section at the most upstream side in the housing at the inside of the housing 60. The blocking member 72 is arranged at a position overlapping with the first conveyance pole S1 in a direction normal to the outer surface of the developing roller 63. The portion of the blocking member 72 closest to the first conveyance pole S1 is arranged over the far end of the first conveyance pole S1 in the roller rotation direction J1.
At a portion of the blocking member 72 which faces the developing roller 63 and is located at the upstream side in the roller rotation direction J1 from the portion of the blocking member 72 closest to the first conveyance pole S1, a surface 72a which is inclined towards a position where the blocking member 72 contacts with the developer layer (not shown) is arranged. For example, the inclined surface 72a forms an angle equal to or greater than 1 degree and equal to or smaller than 45 degrees with respect to a tangent of the developing roller 63 at the location where the blocking member 72 is closest to the first conveyance pole S1.
Between the casing main body 73 and the gap forming member 71, a first opening E1 and a second opening E2 are arranged.
The first opening E1 is formed at the downstream side, in the roller rotation direction J1, with respect to the gap forming member 71. The first opening E1 is positioned at the downstream side of the roller rotation direction J1 in the second gap G2.
The second opening E2 communicates with the first opening E1 through the second gap G2. The second opening E2 is formed at the upstream side, in the roller rotation direction J1, of the gap forming member 71. The second opening E2 is positioned at the upstream side, in the roller rotation direction J1, of the second gap G2.
At the downstream side in the roller rotation direction J1 of the blocking member 72 with respect to the second opening E2, a third opening E3 is formed. The third opening E3 communicates with the downstream side, in the roller rotation direction J1, of the first gap G1. The third opening E3 is positioned in the vicinity of the peeling pole N2.
At the upstream side in the roller rotation direction J1 of the blocking member 72, a fourth opening E4 is formed. The fourth opening E4 communicates with the upstream side, in the roller rotation direction J1, of the first gap G1.
A part of the airflow passing through the blocking member 72 flows from the third opening E3 to the first opening E1. The airflow flowing to the first opening E1 flows to the second opening E2, passes through the fourth opening E4, and then again passes through the blocking member 72 during the rotation of the developing roller 63 in the direction J1. Thus, a circulating airflow is formed around the gap forming member 71. The gap forming member 71 has a function of affecting the airflow direction which determines the flow of airflow. Here, in the roller axial direction Vg, the width of the first opening E1 is set as W1, the width of the second opening E2 is set as W2, and the width of the third opening E3 is set as W3. In order to circulate the airflow smoothly, it is desirable that the widths W1, W2, and W3 of the respective openings E1, E2 and E3 have a relationship of W3>W1>W2. It is desirable that the opening area of the flow path decreases from the third opening E3 to the second opening E2 to and through the first opening E1.
The casing main body 73 is arranged opposed to the developing roller 63 with the gap forming member 71 member in between them. The second gap G2 is formed between the casing main body 73 and the gap forming member 71. The second gap G2 generally extends in the roller rotation direction J1. The second gap G2 communicates with the first gap G1 via the first opening E1 and the third opening E3 or the second opening E2 and the fourth opening E4.
As shown in
The first opening E1 and the second opening E2 are continuous in the roller axial direction Vg, as considered just outwardly of the opposed ends of the ribs 82. In the embodiment, the width W1 of the first opening E1 is the same as the width of the developing roller 63 (refer to
In the roller axial direction Vg, the width W1 of the first opening E1 is larger than the width W2 of the second opening E2 (W1>W2). For example, a ratio W2/W1 of the width W1 of the first opening E1 to the width W2 of the second opening E2 is equal to or greater than 0.5. In addition, the ratio of W2 to Wt (width of the intermediate transfer body 10) is equal to or smaller than 0.76 (W2×0.76).
Hereinafter, a length Z1 of the first opening E1 in an extending direction (height direction) of the holding section 81 is referred to as a “height Z1 of the first opening E1”, and a length Z2 of the second opening E2 in the extending direction (height direction) of the holding section 81 is also referred to as a “height Z2 of the second opening E2”. In other words, the extending direction of the holding section 81 is a direction orthogonal to the roller axial direction Vg, and is the opposite direction of the gap forming member 71 and the casing main body 73. The height Z1 of the first opening E1 and the height Z2 of the second opening E2 are specified by the interval between the casing main body 73 and the gap forming member 71 facing each other.
For example, the height Z1 of the first opening E1 and the height Z2 of the second opening E2 are preferably equal to or greater than 0.5 mm and equal to or smaller than 5.0 mm. It is further preferable that the height Z1 of the first opening E1 and the height Z2 of the second opening E2 are 1.0 mm or more.
As shown in
As shown in
The guide section 74 guides the airflow discharged from the second gap G2 via the second opening E2 between the blocking member 72 and the developing roller 63. The guide section 74 guides the air discharged from the second gap G2 through the second opening E2 toward the first gap G1. The guide section 74 has a guide surface 74a facing the gap forming member 71 across the fourth opening E4. The guide surface 74a is the inner surface of the guide section 74 that contacts the airflow guided by the guide section 74. The guide section 74 extends from the end near the second opening E2 in the housing 60 towards the developing roller 63. The guide section 74 extends from the end of the casing main body 73 at the opening 60h side thereof toward the developing roller 63. For example, the guide section 74 is integrally formed with the casing main body 73. A tip of the guide section 74 is spaced from the developing roller 63. Between the tip of the guide section 74 and the developing roller 63, a gap 74h is formed.
As shown in
A direction in which the second virtual straight line L2 swings towards the upstream side of the roller rotation direction J1 with respect to the first virtual straight line L1 is set to plus. The angle D1 of the guide surface is an angle (plus angle) from the second virtual straight line L2 swung clockwise with respect to the first virtual straight line L1. The angle D1 of the guide surface is preferably equal to or greater than plus 30 degrees and equal to or smaller than 90 degrees. The angle D1 of the guide surface is further preferably plus 45 degrees or smaller than 90 degrees.
Next, the flow of the air around the developing device is described.
As shown in
As shown in
On an outer peripheral surface of the intermediate transfer body 10, at positions extending from the both edges of the intermediate transfer body 10 toward the center of the intermediate transfer body 10 in the roller axial direction Vg by 12% of entire width of the intermediate transfer body 10, airflows in a direction perpendicular to a rotational direction of the intermediate transfer body 10. For example, if the width of the intermediate transfer body 10 is set to 330 mm, the positions extend inwardly from both edges of intermediate transfer body 10 toward the center of the intermediate transfer body 10 by 40 mm. If the width of the developing roller 63 is set to 310 mm in the roller axial direction Vg, the widths of the center area AR1 is about 250 mm, and the widths of the end areas AR2 and AR3 are 30 mm.
In the space between the developing device 13a and the intermediate transfer body 10 (refer to
As shown in
Next, the flow of the air in the developing device 12a is described.
As shown in
The flow of the air in the arrow Q3 direction containing the toner separated from the developer in the housing 60 is guided to the gap 74h, and thus, in the second gap G2, a flow of the air towards an arrow Q4 direction and an arrow Q5 direction towards the fourth opening E4 is generated. If the air containing the toner flows in the arrow Q5 direction, it is guided towards the first gap G1 by the guide surface 74a, and thus, most of the air containing the toner flows into the first gap G1.
The air containing the toner flowing into the first gap G1 flows in the housing 60 in the order of the arrow Q1 direction, the arrow Q2 direction, the arrow Q3 direction, the arrow Q4 direction, and the arrow Q5 direction. In other words, a circulation path of flow of the air containing the toner is formed in the housing 60 by the first gap G1, the second gap G2, the first opening E1, the second opening E2, the third opening E3 and the fourth opening E4.
According to the embodiment, the developing device 12a has the housing 60, the developing roller 63, the gap forming member 71, and the blocking member 72. The developing roller 63 is rotatably arranged at the inside of the housing 60. The developing roller 63 has the development pole N1. The developing roller 63 executes the development by the developer carried by the magnetic force of the development pole N1. The gap forming member 71 forms the first gap G1 with the developing roller 63. The gap forming member 71 forms the second gap G2 with the housing 60. The gap forming member 71 is arranged in the housing 60. The gap forming member 71 is arranged at the downstream side of the roller rotation direction J1 with respect to the development pole N1. The blocking member 72 is arranged in the first gap G1. Between the housing 60 and the gap forming member 71, the first opening E1 and the second opening E2 are arranged. The first opening E1 is formed at the downstream side of the roller rotation direction J1 with respect to the gap forming member 71. The second opening E2 communicates with the first opening E1 through the second gap G2. The second opening E2 is formed at the upstream side of the roller rotation direction J1 with respect to the gap forming member 71. In the roller axial direction Vg, the width W1 of the first opening E1 is larger than the width W2 of the second opening E2 (W1>W2). With the above constitution, the following effects are achieved. The first gap G1, the second gap G2, the first opening E1 and the second opening E2 form the circulation path of the flow of the air containing the toner in the housing 60, and thus, the air containing the toner can be prevented from spouting to the exterior of the developing device 12a. Therefore, scattering of the toner towards the exterior of the developing device 12a can be suppressed. In addition, compared with a case in which the width W1 of the first opening E1 is equal to or smaller than the width W2 of the second opening E2 (W1≤W2), the flow of the air containing the toner easily concentrates on the center area AR1. In other words, it is possible to prevent the flow of the air containing the toner from moving towards the end areas AR2 and AR3. Even if the air containing the toner leaks out of the developing device 13a in the center area AR1, as the toner there is easily conveyed to the intermediate transfer body 10, the possibility of soiling the functional components such as the charging device 12c is low. Therefore, it is possible to suppress contamination of functional components such as the charging device 12c.
Meanwhile, in order to reduce the scattering of the toner to the exterior of the developing device, there is a constitution to arrange a filter, a fan, and the like for recovering the scattered toner. However, there is a possibility that the number of times the filter capturing the toner clogs increases before the end of a product life. The provision of a fan and a duct is necessary for arrangement of the filter, and thus, there is a possibility of increasing the size of the apparatus. According to the embodiment, there is no need to arrange a filter, so that it is preferable for improving maintainability and avoiding enlargement of the apparatus.
Since the ratio W2/W1 of the width W1 of the first opening E1 to the width W2 of the second opening E2 is equal to or greater than 0.5 and equal to or smaller than 0.8, the following effects are achieved. If W2/W1 is less than 0.5, there is a high possibility that the flow of the air containing the toner is directed to the end areas AR2 and AR3. If W2/W1 is less than 0.5, the width W2 of the second opening E2 is too narrow, and the discharge of the air in the developing device 12a is insufficient, which is presumed to result in excessive increase in the pressure in the developing device 12a. On the other hand, if W2/W1 exceeds 0.8, the width W2 of the second opening E2 is too wide, making it difficult to concentrate the flow of the air containing the toner in the center area AR1. According to the embodiment, since W2/W1 is equal to or greater than 0.5 and equal to or less than 0.8, the flow of the air containing the toner is concentrated in the center area AR1, it is preferable for suppressing contamination of functional components such as the charging device 12c.
By arranging the guide section 74 guiding the airflow discharged from the second gap G2 via the second opening E2 between the blocking member 72 and the developing roller 63, the following effects are achieved. Since the air containing the toner is guided to the first gap G1 by the guide section 74, it is possible to prevent the air containing the toner from spouting to the outside of the developing device 12a. Therefore, scattering of the toner to the exterior of the developing device 12a can be suppressed.
The casing main body 73 has the holding section 81 extending towards the gap forming member 71 to hold the gap forming member 71, and thus, the following effects are achieved. It is possible to reduce the number of components and to simplify the apparatus constitution compared with a case in which the holding member is separately arranged for holding the gap forming member 71.
The holding section 81 includes a plurality of ribs 82 arranged at intervals in the roller axial direction Vg and extending linearly in the direction orthogonal to the roller axial direction Vg as seen from the gap forming member 71 side, and thus, the following effects are achieved. Since the plurality of ribs 82 form the plurality of spaces G2a communicating the first opening E1 and the second opening E2, it is possible to smoothly pass the air containing the toner through the plurality of spaces G2a. If the air containing the toner smoothly flows in the plurality of spaces G2a, the air containing the toner can flow smoothly in the circulation path including a plurality of spaces G2a. Therefore, it is possible to more effectively suppress the air containing the toner from spouting to the outside of the developing device 12a.
The rib 82 is provided with the notch 82h opening in the direction parallel to the roller axial direction Vg, and thus, the following effects are achieved. Since the plurality of spaces G2a adjacent to each other across the ribs 82 communicates with each other by the notch 82h, it is preferable because the air containing the toner can flow more smoothly in the circulation path including the plurality of spaces G2a.
The inclined surface 72a forms the angle of 45 degrees or less with respect to the tangent of the developing roller 63, and thus, the following effects are achieved. If the inclined surface 72a forms an angle greater than 45 degrees with respect to the tangent of the developing roller 63, there is a possibility that the developer on the developing roller 63 collides with the blocking member 72 and a toner cloud occurs. Since the inclined surface 72a forms an angle of 45 degrees or less with respect to the tangent of the developing roller 63, it is preferable as the possibility of occurrence of the toner cloud can be reduced.
In the housing 60, the side openings 60c and 60d for circulating the developer between the first chamber 60a and the second chamber 60b are formed at both sides of the roller axial direction Vg, and thus, the following effects are achieved. The air at the second chamber 60b side easily enters the first chamber 60a via the side openings 60c and 60d. On the other hand, if the pressure in the developing device 12a increases, the air containing the toner easily leaks out of both ends in the roller axial direction Vg of the developing device 12a. According to the embodiment, the flow of the air including the toner easily concentrates in the center area AR1 compared with a case in which the width W1 of the first opening E1 is equal to or smaller than the width W2 of the second opening E2 (W1≤W2). Therefore, even if the side openings 60c and 60d are formed at both sides of the roller axial direction Vg in the housing 60, it is possible to suppress contamination of functional components such as the charging device 12c.
The blocking member 72 is arranged at the opposite position facing the first conveyance pole S1 which is magnetic pole section at the most upstream side in the housing in the housing 60, and thus, the following effects are achieved. Since the toner cloud generated in the first conveyance pole S1 can be retained in the developing device 12a, it is preferable for suppressing the scattering of the toner to the outside of the developing device 12a.
Since the angle D1 of the guide surface is plus 30 degrees or more, the following effects are achieved. If the angle D1 of the guide surface is less than plus 30 degrees, the effect of bending the air discharged from the second gap G2 towards the first gap G1 is small. According to the embodiment, since the angle D1 of the guide surface is plus 30 degrees or more, the air discharged from the second gap G2 can be sufficiently bent towards the first gap G1, and thus, it is preferable for suppressing the scattering of the toner to the outside of the developing device 12a. Further, since the angle D1 of the guide surface is plus 45 degrees or more, the air discharged from the second gap G2 can be more effectively bent towards the first gap G1, so that it is preferable for suppressing the scattering of the toner to the outside of the developing device 12a.
The guiding surface 74a is the inner surface of the guide section 74 contacting with the airflow guided by the guide section 74, and thus, the following effects are achieved. Since the air discharged from the second gap G2 can be bent more effectively towards the first gap G1 by the guide surface 74a, it is more preferable for suppressing the scattering of the toner to the outside of the developing device 12a.
The guide section 74 extends from the end near the second opening E2 in the housing 60 towards the developing roller 63, and thus, the following effects are achieved. In a case in which the guide section 74 is integrally formed with the casing main body 73 by using the same member, since there is no need to separately arrange the guide member, the number of components can be reduced and the apparatus constitution can be simplified.
The height Z1 of the first opening E1 and the height Z2 of the second opening E2 are specified by a distance between the casing main body 73 and the gap forming member 71 facing each other, and are 0.5 mm or more, and thus, the following effects are achieved. If the height Z1 of the first opening E1 and the height Z2 of the second opening E2 are less than 0.5 mm, there is a high possibility that the flow of the air in the second gap G2 becomes unsmooth and the efficiency of discharging the air in the developing device 12a decreases. According to the embodiment, the height Z1 of the first opening E1 and the height Z2 of the second opening E2 are 0.5 mm or more, so that the flow of the air in the second gap G2 can be smoothed. If the air containing the toner flows smoothly in the second gap G2, the air containing the toner can flow smoothly in the circulation path including the second gap G2. Therefore, it is preferable because it is possible to effectively suppress the air containing the toner from spouting to the outside of the developing device 12a. Furthermore, since the height Z1 of the first opening E1 and the height Z2 of the second opening E2 are 1.0 mm or more, the flow of the air in the second gap G2 can be further smoothed, so that it is preferable for effectively preventing the air containing the toner from spouting to the outside of the developing device 12a.
A modification is described below.
The holding section 81 is not limited to including a plurality of ribs 82 arranged at intervals in the roller axial direction Vg and extending linearly in the direction orthogonal to the roller axial direction Vg as seen from the gap forming member 71 side. For example, the holding section 81 may have a plurality of ribs 82 extending linearly in a direction intersecting the roller axial direction Vg as seen from the gap forming member 71 side.
As shown in
According to the present modification, a plurality of ribs 182 forms a plurality of spaces G2a communicating the first opening E1 and the second opening E2, so that the air containing the toner can flow smoothly in the plurality of spaces G2a. If the air containing the toner flows smoothly in the plurality of spaces G2a, a circulation path of the flow of the air including the toner is easily formed in the housing 60. Therefore, it is possible to more effectively prevent the air containing the toner from spouting to the outside of the developing device 12a.
The guide section 74 is not limited to being integrally formed with the casing main body 73 by using the same member. For example, the guide section 74 may be formed separately from the casing main body 73.
As shown in
The guide section 174 guides the direction of the airflow discharged from the second gap G2 through the second opening E2 between the blocking member 72 and the developing roller 63 toward the first gap G1. The guide section 174 has a guide surface 174a facing a gap forming member 171 across the fourth opening E4. The guide surface 174a is the inner surface of the guide section 174 that makes contact with the airflow guided by the guide section 174. For example, the tip of the guide section 174 is spaced from the developing roller 63. A gap 174h is formed between the tip of the guide section 174 and the developing roller 63.
As shown in
The guide plate 276 is formed separately from, i.e., formed non integrally with, the casing main body 273. The guide plate 276 is attached to the tip of the extending portion 275. The guide plate 276 is formed into a plate shape extending from the tip of the extending portion 275 towards the first gap G1. For example, the guide plate 276 is a sheet material such as polyethylene terephthalate (PET).
The guide plate 276 guides the air discharged from the second gap G2 through the second opening E2 toward the first gap G1. The guide plate 276 has a guide surface 276a facing the fourth opening E4. The guide surface 276a is an inner surface of the guide plate 276 which makes contact with the airflow guided by the guide plate 276. The guide plate 276 is spaced from the developing roller 63. A gap 274h is formed between the guide plate 276 and the developing roller 63.
The blocking member 72 of the present modification is arranged in the vicinity of the opposite position facing the first conveyance pole S1 which is the magnetic pole section at the most upstream side in the housing at the inside of the housing 60. Additionally, the blocking member 72 of the present modification is arranged such that the furthest extension thereof from the gap forming member is located between the first conveyance pole S1 and the peeling pole N2 adjacent to the outer surface of the developing roller 63. The blocking member 72 is arranged between the first conveyance pole S1 and the peeling pole N2 in the roller rotation direction J1.
A height H1 of the second opening E2 is larger than a projecting height H2 of the guide plate 276 (H1>H2) from the guide surface 74a (
According to the present modification, the guide section 274 includes the extending portion 275 and the guide plate 276. The extending portion 275 extends from the end near the second opening E2 in the housing towards the developing roller 63. The guide plate 276 extends from the tip of the extending portion 275 towards the first gap G1. With the above constitution, the following effects are achieved. If the extending portion 275 is integrally formed with the casing main body 273 as an integral part of the same member, since it is unnecessary to separately arrange an extending member, the number of components can be reduced and the apparatus constitution can be simplified. In addition, if the guide plate 276 is formed separately from the casing main body 273, the orientation of the guide plate 276 is easily optimized.
The difference (H1−H2) of the height H1 of the second opening E2 and the projecting height H2 of the guide plate 276 is equal to or greater than 0.5 mm and equal to or smaller than 2.0 mm, and thus, the following effects are achieved. If the difference (H1−H2) is less than 0.5 mm, there is a high possibility that the flow of the air in the second opening E2 becomes unsmooth and the efficiency of discharging the air from the developing device 12a decreases. On the other hand, if the difference (H1−H2) exceeds 2.0 mm, the effect of bending the air discharged from the second gap G2 towards the first gap G1 is reduced. According to the embodiment, the difference (H1−H2) is equal to or greater than 0.5 mm and equal to or smaller than 2.0 mm, and thus, it is possible to smooth the flow of the air in the second opening E2 and to sufficiently bend the air discharged from the second gap G2 towards the gap G1. Therefore, it is preferable for suppressing the scattering of the toner to the outside of the developing device 12a.
The blocking member 72 is arranged between the first conveyance pole S1 and the peeling pole N2 in the roller rotation direction J1, and thus, the following effects are achieved. It is preferable for arranging the second opening E2 and the blocking member 72 at an appropriate distance in the developing device 12a. For example, it is easy to optimize the orientation of the guide plate 276. In particular, if the developing roller 63 having a small diameter of 18 mm or less is used, it is preferable because it is easy to ensure the arrangement space of the blocking member 72 and the guide plate 276.
The first opening E1 and the second opening E2 are not limited to be continuous in the roller axial direction Vg. For example, at least one of the first opening E1 and the second opening E2 may be divided in the roller axial direction Vg. The height Z1 of the first opening E1 and the height Z2 of the second opening E2 are 0.5 mm or more even if at least one of the first opening E1 and the second opening E2 is divided in the roller axial direction Vg.
As shown in
A direction in which the fourth virtual straight line L4 swings clockwise with respect to the third virtual straight line L3 is set to plus. The angle D2 of the guide surface is an angle (plus angle) where the fourth virtual straight line swings clockwise with respect to the third virtual straight line L3. The angle D2 of the guide surface is preferably plus 30 degrees or more. The angle D2 of the guide surface is more preferably plus 45 degrees or more. In the present modification, the angle D2 of the guide surface is about 90 degrees.
According to the present modification, since the angle D2 of the guide surface is plus 90 degrees, the air discharged from the second gap G2 can be sufficiently bent towards the first gap G1, which is effective for suppressing the scattering of the toner to the exterior of the developing device 12a.
As shown in
As shown in
The inventor of the present invention confirms the relationship between the ratio W2/W1 of the width W1 of the first opening to the width W2 of the second opening and the number of defective printed sheets.
Table 1 shows the relationship between the ratio W2/W1 of the width W1 of the first opening to the width W2 of the second opening and the number of printed sheets before a defect occurs. As shown in Table 1, if the ratio W2/W1 is equal to or greater than 0.52 and equal to or smaller than 0.81, it is confirmed that the number of defective printed sheets is 120,000 or more.
According to the developing device of at least one embodiment described above, the scattering of the toner to the exterior of the developing device can be suppressed.
The functions of the image forming apparatus according to the foregoing embodiment may be realized by a computer. In this case, the functions may be realized by recording programs for realizing the functions in a computer-readable recording medium and reading the programs recorded in the recording medium into a computer system to execute it. Further, it is assumed that the “computer system” described herein contains an OS or hardware such as peripheral devices. Further, the “computer-readable recording medium” refers to a portable medium such as a flexible disk, a magneto-optical disk, a ROM, a CD-ROM and the like or a storage device such as a hard disk built in the computer system. Furthermore, the “computer-readable recording medium” refers to a medium for dynamically holding the programs for a short time like a communication wire in a case in which the programs are sent via a communication line such as a network like the Internet or a telephone line or a medium for holding the programs for a certain time like a volatile memory in the computer system serving as a server and a client. The foregoing programs may realize a part of the above-mentioned functions or realize the functions described above by the combination with the programs already recorded in the computer system.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the invention. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the invention. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-138299 | Jul 2017 | JP | national |
