JP2012168432A - Developing device and image forming apparatus - Google Patents

Abstract

The present invention provides a developing device capable of suppressing the scattered toner trapped and deposited on a scattered toner capturing cover from adhering to the surface of a toner-carrying rotating body and developing.
A developer carrying rotator 130 on which a magnetic brush 194 is formed, and a toner carrying rotator 150 carrying a toner 192 supplied from the developer carrying rotator 130 and forming a toner layer 193 by the magnetic brush 194. And a voltage applying unit for applying a developing bias voltage between the toner carrying rotator 150 and the image carrying member 2a, and a tip 142 close to the developer carrying rotator 130, thereby allowing the developer carrying rotator 130 to A regulating member 140 that regulates the amount of developer 190 carried and a scattered toner capturing cover 141 are provided, and the rotation direction C of the toner carrying rotary body 150 is relative to the rotation direction B of the developer carrying rotary body 130. The forward rotation direction is set.
[Selection] Figure 3

Description

  The present invention relates to a developing device for developing an electrostatic latent image formed by an electrophotographic method, and an image forming apparatus including the developing device.

  In recent years, a two-component developer containing at least a carrier and a toner is supported on the surface of a developer-carrying rotator to form a magnetic brush, and toner supplied from the magnetic brush to the toner-carrying rotator A so-called touch-down method (also called a hybrid method) is developed in which an electrostatic latent image on the surface of the image carrier is developed as a toner image by forming a toner layer on the surface and causing the toner to fly from the toner layer to the image carrier. )) Is attracting attention.

  In a touch-down type developing device, generally, a regulating member that regulates the amount of developer carried on the developer-carrying rotator by bringing the tip portion close to the surface of the developer-carrying rotator, and a regulating member And a scattered toner capturing cover for capturing and depositing toner scattered outward from the developer carrying rotator. Therefore, when the development is continuously performed for a long time, the amount of toner trapped and deposited on the scattering toner trap cover gradually increases, and when the deposited toner amount increases beyond a certain level, The low-toner toner comes into contact with the magnetic brush on the surface of the developer-carrying rotating body and is pumped up by the magnetic brush. Then, a part of the low-chargeable toner pumped up by the magnetic brush is transferred (supplied) to the toner-carrying rotator, and then jumped to the electrostatic latent image on the surface of the image-carrying member and developed. Become. For this reason, at the time of development, a toner with low chargeability falls to the development region, and so-called toner drop tends to cause image defects.

  Conventionally, as a countermeasure against scattering of toner from a developer carrying rotator, a toner collecting roller having a magnetic member (magnet) disposed therein is disposed between the developer carrying rotator and the toner carrying rotator. There has been proposed a developing device that collects scattered toner floating in the vicinity of the developer carrying rotator and the toner carrying rotator by a collecting roller and returns the collected scattered toner to the inside of the developing device (for example, , See Patent Document 1).

JP 2008-185735 A

  However, even in the developing device described in Patent Document 1, it is not possible to collect all of the scattered toner by the toner recovery roller and return it to the inside of the developing device. The scattered toner accumulates on the surface, and the accumulated toner is pumped up by the developer carrying rotor. In the developing device described in Patent Document 1, the surface of the developer-carrying rotator and the surface of the toner-carrying rotator are rotated in a counter-rotation manner in which the surfaces of both the carrying rotators are rotated in opposite directions. It is configured. For this reason, the toner pumped up by the developer-carrying rotator does not pass between the gaps of both the supported rotators, but is affected by the magnetic field formed between the gaps of the two supported rotators, Adhere to the surface. As a result, the above-described image failure occurs due to toner dropping.

The present invention is a development that can suppress the occurrence of image defects such as toner dropping due to the scattered toner trapped and deposited on the scattered toner trapping cover adhering to the surface of the toner carrying rotor. An object is to provide an apparatus.
Another object of the present invention is to provide an image forming apparatus including the developing device.

  The present invention provides a developer-carrying rotator that carries a two-component developer containing at least a carrier and a toner, a magnetic brush formed of a carrier contained in the two-component developer is formed on the surface, and the developer-carrying rotator. A toner-carrying rotator that is arranged to face the upper side and carries toner supplied from the developer-carrying rotator and forms a toner layer by the magnetic brush; and the toner carried by the toner-carrying rotator and the image carrier A voltage applying unit for applying a developing bias voltage between the toner carrying rotator and the image carrying member in order to fly the electrostatic latent image on the surface of the toner and developing the electrostatic latent image as a toner image; The amount of the developer carried on the developer-carrying rotator is reduced by positioning the tip part close to the surface of the developer-carrying rotator, which is located below the horizontal plane passing through the rotation center of the developer-carrying rotator. Rule And a scattering toner capturing cover that is disposed above the restricting member and captures and deposits toner scattered outward from the developer-carrying rotator, and rotates the toner-carrying rotator. The present invention relates to a developing device in which a direction is set to a forward rotation direction with respect to a rotation direction of the developer carrying rotator.

  In addition, it is preferable that a second magnetic brush rotator is further provided at a position upstream of the two carrying rotators from the closest position where the toner carrying rotator and the developer carrying rotator are closest to each other.

  The rotation direction of the second magnetic brush rotator is preferably set to a forward rotation direction with respect to the rotation direction of the toner carrying rotator.

  In addition, it is preferable that the diameter of the second magnetic brush rotator is set to be equal to or less than half of the diameter of the developer carrying rotator.

  Further, it is preferable that the second magnetic brush rotator is configured to be capable of changing its rotation speed to a speed twice or more that of the developer carrying rotator.

  According to the present invention, an electrostatic latent image is formed on the surface of the developing device, and a toner image is formed on the electrostatic latent image by receiving toner from the toner layer of the developing device. A plurality of image carriers, a transfer unit that directly or indirectly transfers a toner image formed on the image carrier to a sheet-like transfer material, and the transferred toner image on a sheet-like transfer material The present invention relates to an image forming apparatus including a fixing unit for fixing.

According to the present invention, it is possible to suppress the occurrence of image defects such as toner dropping due to the scattered toner trapped and accumulated on the scattered toner capturing cover adhering to the surface of the toner carrying rotor. A developing device capable of being provided can be provided.
In addition, according to the present invention, an image forming apparatus including the developing device can be provided.

FIG. 3 is a diagram for explaining an arrangement of each component of the copier 1 according to the embodiment of the present invention. FIG. 3 is a cross-sectional view for explaining components of a developing device 16a and a photosensitive drum 2a in the copier according to the present embodiment. FIG. 3 is a partially enlarged view of FIG. 2. 4 is a partially enlarged view showing a state in which a toner layer 193 having a predetermined thickness is formed on the surface of the developing roller 150. FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
With reference to FIG. 1, the overall structure of a copier 1 as an image forming apparatus in the present embodiment will be described. FIG. 1 is a diagram for explaining the arrangement of each component of the copier 1.

As shown in FIG. 1, a copier 1 as an image forming apparatus is disposed on an upper side in the vertical direction Z of the copier 1 and on a lower side of the copier 1 in the vertical direction Z. An apparatus main body M that forms a toner image on a sheet T as a sheet-like image forming material based on image information read by the image reading apparatus 300.
In the description of the copying machine 1, the sub-scanning direction X is also referred to as “left-right direction” of the copying machine 1, and the main scanning direction Y (direction passing through FIG. 1) is also referred to as “front-back direction” of the copying machine 1. The vertical direction Z of the copier 1 is orthogonal to the sub-scanning direction X and the main scanning direction Y.

First, the image reading apparatus 300 will be described.
As shown in FIG. 1, the image reading apparatus 300 includes a lid member 70 and a reading unit 301 that reads an image of a document G.
The lid member 70 is connected to the reading unit 301 so as to be opened and closed by a connecting unit (not shown). The lid member 70 has a function of protecting a reading surface 302A described later.

  The reading unit 301 includes a housing 306 and a reading surface 302 </ b> A disposed on the upper side of the housing 306. The reading unit 301 includes an illumination unit 340 including a light source, a plurality of mirrors 321, 322, and 323, and a first frame 311 and a second frame that move in the sub-scanning direction X in an internal space 304 of the housing 306. A body 312, an imaging lens 357, a CCD 358 as a reading device, and a CCD substrate 361 that performs predetermined processing on image information read by the CCD 358 and outputs the image information to the apparatus body M side. Prepare. The illumination unit 340 and the first mirror 321 are accommodated in the first frame 311. The second mirror 322 and the third mirror 323 are accommodated in the second frame 312.

  The reading surface 302A extends in a direction perpendicular to the sub-scanning direction X and the main scanning direction Y, and extends over most of the sub-scanning direction X in the reading unit 301. The document G is placed on the reading surface 302A. Each of the first frame 311 and the second frame 312 moves in the sub-scanning direction X while keeping the length of an optical path H (optical path length) to be described later constant. Thereby, the image of the original G placed on the reading surface 302A is read.

  In the internal space 304 of the housing 306, the plurality of mirrors 321, 322, and 323 form an optical path H for allowing light from the original G to enter the imaging lens 357. In addition, the first frame 311 moves at a constant speed A in the sub-scanning direction X, and the second frame 312 moves at a constant speed A / 2 in the sub-scanning direction X. The length of H is kept constant. As a result, the image of the original G placed on the reading surface 302A is read on the reading surface 302A.

Next, the apparatus main body M will be described.
The main body M of the apparatus forms an image forming unit GK that forms a predetermined toner image on the paper T based on predetermined image information, and feeds the paper T to the image forming unit GK and discharges the paper T on which the toner image is formed. A paper supply / discharge unit KH for paper.
The outer shape of the apparatus main body M is configured by a case body BD as a casing.

  As shown in FIG. 1, the image forming unit GK includes photosensitive drums 2a, 2b, 2c, and 2d as image carriers (photosensitive members), charging units 10a, 10b, 10c, and 10d, and a laser as an exposure unit. Scanner units 4a, 4b, 4c, 4d, developing devices 16a, 16b, 16c, 16d, toner cartridges 5a, 5b, 5c, 5d, toner supply units 6a, 6b, 6c, 6d, drum cleaning unit 11a, 11b, 11c, 11d, static eliminators 12a, 12b, 12c, 12d, intermediate transfer belt 7, primary transfer rollers 37a, 37b, 37c, 37d, secondary transfer roller 8, counter roller 18, fixing Part 9.

  As shown in FIG. 1, the paper feed / discharge unit KH includes a paper feed cassette 52, a manual paper feed unit 64, a transport path L for paper T, a registration roller pair 80, a first paper discharge unit 50a, 2 paper discharge unit 50b. As will be described later, the transport path L includes a first transport path L1, a second transport path L2, a third transport path L3, a manual transport path La, a return transport path Lb, and a post-processing transport path Lc. Is a collection of

Hereinafter, each configuration of the image forming unit GK and the paper supply / discharge unit KH will be described in detail.
First, the image forming unit GK will be described.
In the image forming unit GK, charging by the charging units 10a, 10b, 10c, and 10d in order from the upstream side to the downstream side along the respective surfaces of the photosensitive drums 2a, 2b, 2c, and 2d, and the laser scanner units 4a, 4b, 4c, 4d exposure, development devices 16a, 16b, 16c, 16d development, intermediate transfer belt 7 and primary transfer rollers 37a, 37b, 37c, 37d primary transfer, static eliminators 12a, 12b, 12c, 12d And cleaning by the drum cleaning units 11a, 11b, 11c, and 11d.
Further, in the image forming unit GK, secondary transfer by the intermediate transfer belt 7, the secondary transfer roller 8 and the counter roller 18, and fixing by the fixing unit 9 are performed.

  Each of the photosensitive drums 2a, 2b, 2c, and 2d is formed of a cylindrical member and functions as a photosensitive member or an image carrier. Each of the photosensitive drums 2 a, 2 b, 2 c, and 2 d is disposed so as to be rotatable in the direction of an arrow about an axis that extends in a direction orthogonal to the traveling direction of the intermediate transfer belt 7. An electrostatic latent image can be formed on the surface of each of the photosensitive drums 2a, 2b, 2c, and 2d.

  Each of the charging units 10a, 10b, 10c, and 10d is disposed to face the surface of each of the photosensitive drums 2a, 2b, 2c, and 2d. Each of the charging units 10a, 10b, 10c, and 10d uniformly charges the surface of each of the photosensitive drums 2a, 2b, 2c, and 2d negatively (minus polarity) or positively (plus polarity).

  The laser scanner units 4a, 4b, 4c, and 4d function as exposure units, and are spaced apart from the surfaces of the photosensitive drums 2a, 2b, 2c, and 2d. Each of the laser scanner units 4a, 4b, 4c, and 4d includes a laser light source (not shown), a polygon mirror, a polygon mirror driving motor, and the like.

  Each of the laser scanner units 4a, 4b, 4c, and 4d scans and exposes the surface of each of the photosensitive drums 2a, 2b, 2c, and 2d based on image information related to the image read by the reading unit 301. The scanning exposure is performed by each of the laser scanner units 4a, 4b, 4c, and 4d, thereby removing the charges on the exposed portions of the surfaces of the photosensitive drums 2a, 2b, 2c, and 2d. Thereby, electrostatic latent images are formed on the respective surfaces of the photosensitive drums 2a, 2b, 2c, and 2d.

  The developing devices 16a, 16b, 16c, and 16d are provided corresponding to the photosensitive drums 2a, 2b, 2c, and 2d, respectively, and are disposed to face the surfaces of the photosensitive drums 2a, 2b, 2c, and 2d. Each of the developing devices 16a, 16b, 16c, and 16d attaches toner of each color to the electrostatic latent image formed on the surface of each of the photosensitive drums 2a, 2b, 2c, and 2d, and transfers a color toner image to the photosensitive drum. 2a, 2b, 2c and 2d are formed on the respective surfaces. Each of the developing devices 16a, 16b, 16c, and 16d corresponds to four colors of yellow, cyan, magenta, and black. Details of the developing devices 16a, 16b, 16c, and 16d will be described later.

  The toner cartridges 5a, 5b, 5c, and 5d are provided corresponding to the developing devices 16a, 16b, 16c, and 16d, respectively, and the toners of the respective colors supplied to the developing devices 16a, 16b, 16c, and 16d, respectively. To accommodate. Each of the toner cartridges 5a, 5b, 5c, and 5d accommodates yellow toner, cyan toner, magenta toner, and black toner.

  The toner supply units 6a, 6b, 6c, and 6d are provided corresponding to the toner cartridges 5a, 5b, 5c, and 5d and the developing devices 16a, 16b, 16c, and 16d, respectively. The toners of the respective colors accommodated in 5d are supplied to the developing devices 16a, 16b, 16c, and 16d, respectively. Each of the toner supply units 6a, 6b, 6c, and 6d is connected to each of the developing devices 16a, 16b, 16c, and 16d by a toner supply path (not shown).

  To the intermediate transfer belt 7, the toner images of the respective colors formed on the photosensitive drums 2a, 2b, 2c, and 2d are sequentially primary-transferred. The intermediate transfer belt 7 is stretched around a driven roller 35, a counter roller 18 including a driving roller, a tension roller 36, and the like. Since the tension roller 36 biases the intermediate transfer belt 7 from the inside to the outside, a predetermined tension is applied to the intermediate transfer belt 7.

  Primary transfer rollers 37a, 37b, 37c, and 37d are arranged to face each other on the side opposite to the photosensitive drums 2a, 2b, 2c, and 2d with the intermediate transfer belt 7 interposed therebetween.

  A predetermined portion of the intermediate transfer belt 7 is sandwiched between the primary transfer rollers 37a, 37b, 37c, and 37d and the photosensitive drums 2a, 2b, 2c, and 2d, respectively. The predetermined portion thus sandwiched is pressed against the surface of each of the photosensitive drums 2a, 2b, 2c, and 2d. Primary transfer nips N1a, N1b, N1c, and N1d are formed between the photosensitive drums 2a, 2b, 2c, and 2d and the primary transfer rollers 37a, 37b, 37c, and 37d, respectively. In each of the primary transfer nips N1a, N1b, N1c, and N1d, the toner images of the respective colors developed on the photosensitive drums 2a, 2b, 2c, and 2d are sequentially primary-transferred onto the intermediate transfer belt 7, respectively. As a result, a full-color toner image is formed on the intermediate transfer belt 7.

  To the primary transfer rollers 37a, 37b, 37c, and 37d, toner images of the respective colors formed on the photosensitive drums 2a, 2b, 2c, and 2d are respectively transferred to the intermediate transfer belt 7 by a primary transfer bias applying unit (not shown). A primary transfer bias for transferring the toner image is applied.

  The static eliminators 12a, 12b, 12c, and 12d are arranged to face the surfaces of the photosensitive drums 2a, 2b, 2c, and 2d, respectively. The static eliminators 12a, 12b, 12c, and 12d respectively irradiate the surfaces of the photosensitive drums 2a, 2b, 2c, and 2d to irradiate light, and the photosensitive drums 2a, 2b, and 2c after primary transfer is performed. 2d, each surface is neutralized (charge is removed).

  The drum cleaning units 11a, 11b, 11c, and 11d are disposed to face the surfaces of the photosensitive drums 2a, 2b, 2c, and 2d, respectively. Each of the drum cleaning units 11a, 11b, 11c, and 11d removes toner and adhering matter remaining on the surfaces of the photosensitive drums 2a, 2b, 2c, and 2d, and conveys the removed toner to a predetermined recovery mechanism. And collect it.

  The secondary transfer roller 8 secondarily transfers the full-color toner image primarily transferred to the intermediate transfer belt 7 onto the paper T. A secondary transfer bias for transferring the full color toner image formed on the intermediate transfer belt 7 to the paper T is applied to the secondary transfer roller 8 by a secondary transfer bias applying unit (not shown).

  The secondary transfer roller 8 contacts or separates from the intermediate transfer belt 7. Specifically, the secondary transfer roller 8 is configured to be movable between a contact position where the secondary transfer roller 8 is in contact with the intermediate transfer belt 7 and a spaced position where the secondary transfer roller 8 is separated from the intermediate transfer belt 7. Specifically, the secondary transfer roller 8 is disposed at the contact position when the full-color toner image primarily transferred onto the surface of the intermediate transfer belt 7 is secondarily transferred to the paper T, and in other cases. Are arranged at spaced positions.

  A counter roller 18 is disposed on the opposite side of the intermediate transfer belt 7 from the secondary transfer roller 8. A predetermined portion of the intermediate transfer belt 7 is sandwiched between the secondary transfer roller 8 and the opposing roller 18. Then, the paper T is pressed against the outer surface of the intermediate transfer belt 7 (the surface on which the toner image is primarily transferred). A secondary transfer nip N <b> 2 is formed between the intermediate transfer belt 7 and the secondary transfer roller 8. In the secondary transfer nip N2, the full-color toner image primarily transferred to the intermediate transfer belt 7 is secondarily transferred to the paper T.

  The fixing unit 9 melts and heats the toner of each color constituting the toner image secondarily transferred onto the paper T and fixes the toner on the paper T. The fixing unit 9 includes a heating rotator 9a heated by a heater and a pressure rotator 9b pressed against the heating rotator 9a. The heating rotator 9a and the pressure rotator 9b sandwich and pressurize the paper T onto which the toner image has been secondarily transferred, and convey the paper T. When the paper T is conveyed in a state of being sandwiched between the heating rotator 9a and the pressure rotator 9b, the toner transferred to the paper T is fixed to the paper T by being melted and pressed. Is done.

Next, the paper supply / discharge unit KH will be described.
As shown in FIG. 1, in the lower part of the apparatus main body M, two paper feed cassettes 52 that store paper T are arranged in an up-down direction. The paper feed cassette 52 is configured to be pulled out from the housing of the apparatus main body M in the horizontal direction. In the paper feed cassette 52, a placement plate 60 on which the paper T is placed is disposed. In the paper feed cassette 52, the paper T is stored in a state of being stacked on the placement plate 60. The paper T placed on the placement plate 60 is sent out to the transport path L by the cassette paper feed unit 51 arranged at the end of the paper feed cassette 52 on the paper feed side (the left end in FIG. 1). The cassette paper feed unit 51 includes a forward feed roller 61 for taking out the paper T on the placement plate 60 and a paper feed roller pair 63 for feeding the paper T one by one to the transport path L. Is provided.

  A manual paper feed unit 64 is provided on the right side surface (right side in FIG. 1) of the apparatus main body M. The manual paper feed unit 64 is provided mainly for supplying the apparatus main body M with a paper T of a size and type different from the paper T set in the paper feed cassette 52. The manual paper feed unit 64 includes a manual feed tray 65 that constitutes a part of the right side surface of the apparatus main body M in the closed state, and a paper feed roller 66 as a feed roller. The manual feed tray 65 functions as a placement portion on which one or a plurality of sheets T can be placed in the open state, and a lower end of the manual feed tray 65 is attached to the vicinity of the paper feed roller 66 so as to be rotatable (openable and closable). The paper feed roller 66 sends out (feeds) the paper T placed on the open manual feed tray 65 toward the manual feed path La inside the housing 306.

  A first paper discharge unit 50 a and a second paper discharge unit 50 b are provided on the upper side of the apparatus main body M. The first paper discharge unit 50a and the second paper discharge unit 50b discharge the paper T to the outside of the apparatus main body M. Details of the first paper discharge unit 50a and the second paper discharge unit 50b will be described later.

  The conveyance path L for conveying the paper T includes a first conveyance path L1 from the cassette paper feeding unit 51 to the secondary transfer nip N2, a second conveyance path L2 from the secondary transfer nip N2 to the fixing unit 9, and a fixing unit. 9 to the first paper discharge section 50a, the manual conveyance path La for joining the paper supplied from the manual paper feed section 64 to the first conveyance path L1, and the third conveyance path L3 on the upstream side. The paper transported from the upstream side to the downstream side is reversed and returned to the first transport path L1, and the paper transporting the third transport path L3 from the upstream side to the downstream side is connected to the second paper discharge unit 50b. And a post-processing transport path Lc for transporting to a post-processing device (not shown).

Moreover, the 1st junction part P1 and the 2nd junction part P2 are provided in the middle of the 1st conveyance path L1. A first branch portion Q1 is provided in the middle of the third transport path L3.
The first joining part P1 is a joining part where the manual feed path La joins the first transport path L1. The second junction P2 is a junction where the return conveyance path Lb merges with the first conveyance path L1.
The first branch portion Q1 is a branch portion where the post-processing transport path Lc branches from the third transport path L3. A rectifying member 58 is provided in the first branch portion Q1. The rectifying member 58 rectifies the transport direction of the paper T carried out from the fixing unit 9 to the third transport path L3 toward the first paper discharge section 50a or the post-processing transport path Lc toward the second paper discharge section 50b ( Switch).

  In the middle of the first transport path L1 (specifically, between the second joining portion P2 and the secondary transfer roller 8), a sensor for detecting the paper T and correction of the skew (oblique paper feeding) of the paper T In addition, a registration roller pair 80 is arranged for matching the timing with the formation of the toner image in the image forming unit GK. The sensor is disposed immediately before the registration roller pair 80 in the transport direction of the paper T (upstream in the transport direction). The registration roller pair 80 conveys the paper T by performing the above-described correction and timing adjustment based on detection signal information from the sensor.

  The return conveyance path Lb is a conveyance path that is provided to make the opposite surface (unprinted surface) opposite to the already printed surface to the intermediate transfer belt 7 when performing duplex printing on the paper T. According to the return conveyance path Lb, the sheet T conveyed from the first branching section Q1 to the first sheet discharge section 50a is turned upside down and returned to the first conveyance path L1 to the upstream side of the secondary transfer roller 8. It can be conveyed upstream of the registered registration roller pair 80. A predetermined toner image is transferred onto the unprinted surface in the secondary transfer nip N2 on the paper T that is reversed upside down by the return conveyance path Lb.

  A first paper discharge unit 50a is formed at the end of the third transport path L3. The first paper discharge unit 50 a is disposed on the upper side of the apparatus main body M. The first paper discharge unit 50a is open toward the right side surface of the apparatus main body M (the right side in FIG. 1, the manual paper feed unit 64 side). The first paper discharge unit 50a discharges the paper T transported through the third transport path L3 to the outside of the apparatus main body M.

  On the opening side of the first paper discharge section 50a, a paper discharge stacking section M1 is formed. The paper discharge stacking unit M1 is formed on the upper surface (outer surface) of the apparatus main body M. The paper discharge stacking unit M1 is a part formed by the upper surface of the apparatus main body M being depressed downward. The bottom surface of the paper discharge stacking unit M1 constitutes a part of the top surface of the apparatus main body M. In the paper discharge stacking unit M1, sheets T formed with a predetermined toner image and discharged from the first paper discharge unit 50a are stacked and stacked.

A second paper discharge unit 50b is formed at the end of the post-processing conveyance path Lc. The second paper discharge unit 50b is disposed on the upper side of the apparatus main body M. The second paper discharge section 50b opens toward the left side of the apparatus main body M (left side in FIG. 1, the side to which the post-processing apparatus is connected). The second paper discharge unit 50b discharges the paper T conveyed through the post-processing conveyance path Lc to the outside of the apparatus main body M.
A post-processing device (not shown) is connected to the opening side of the second paper discharge unit 50b. The post-processing device performs post-processing (stapling, punching, etc.) of paper ejected from the image forming apparatus (copy machine 1).
A paper detection sensor is disposed at a predetermined position on each conveyance path.

Next, a paper jam (JAM) in the main transport path L1 to L3 (the first transport path L1, the second transport path L2, and the third transport path L3 are collectively referred to as “main transport path” hereinafter) and the return transport path Lb. A structure for eliminating the problem will be briefly described.
As shown in FIG. 1, on the left side surface of the apparatus main body M (left side in FIG. 1), main conveyance paths L1 to L3 and a return conveyance path Lb are arranged in parallel so as to mainly extend in the vertical direction. A cover body 40 is provided on the left side of the apparatus body M (left side in FIG. 1) so as to form a part of the side surface of the apparatus body M. The cover body 40 is connected to the apparatus main body M via a fulcrum shaft 43 at the lower end thereof. The fulcrum shaft 43 is disposed along the direction in which the axial direction crosses the main transport paths L1 to L3 and the return transport path Lb. The cover body 40 is configured to be rotatable between a closed position (position shown in FIG. 1) and an open position (not shown) with the fulcrum shaft 43 as a center.

  The cover body 40 includes a first cover portion 41 that is rotatably connected to the apparatus main body M by a fulcrum shaft 43, and a second cover portion 42 that is rotatably connected to the apparatus main body M by the same fulcrum shaft 43. It consists of and. The first cover portion 41 is located on the outer side (side surface side) of the apparatus main body M than the second cover portion 42. In FIG. 1, the hatched portion with the left-down dashed line is the first cover portion 41, and the hatched portion with the right-down dashed line is the second cover portion 42.

In the state where the cover body 40 is located at the closed position, the outer surface side of the first cover portion 41 forms a part of the outer surface (side surface) of the apparatus main body M.
In the state where the cover body 40 is located at the closed position, the inner surface side (the apparatus main body M side) of the second cover portion 42 forms part of the main transport paths L1 to L3.
Further, in a state where the cover body 40 is located at the closed position, the inner surface side of the first cover portion 41 and the outer surface side of the second cover portion 42 form at least a part of the return conveyance path Lb. That is, the return conveyance path Lb is formed between the first cover part 41 and the second cover part 42.

  The copying machine 1 of the present embodiment includes the cover body 40 having such a configuration, so that when a paper jam (JAM) occurs in the main transport paths L1 to L3, the cover body 40 is closed as shown in FIG. By rotating from the position to an open position (not shown) to open the main transport paths L1 to L3, it is possible to process paper jammed in the main transport paths L1 to L3. On the other hand, when a paper jam occurs in the return conveyance path Lb, the cover body 40 is rotated to the open position, and then the second cover portion 42 is moved to the apparatus main body M side (right side in FIG. ) To open the return conveyance path Lb, the paper jammed in the return conveyance path Lb can be processed.

Next, with reference to FIGS. 2 to 4, a configuration related to the developing devices 16 a, 16 b, 16 c, and 16 d, which is a characteristic part of the copier 1 of the present embodiment, will be described. As described above, the copying machine 1 includes the four developing devices 16a, 16b, 16c, and 16d. Since the copier 1 has the same configuration, the developing device 16a is described as a representative here. To do.
FIG. 2 is a cross-sectional view for explaining the components of the developing device 16a and the photosensitive drum 2a in the copier of the present embodiment. FIG. 3 is a partially enlarged view of FIG. FIG. 4 is a partially enlarged view showing a state in which a toner layer 193 having a predetermined thickness is formed on the surface of the developing roller 150.

  As shown in FIGS. 2 and 3, the developing device 16 a of this embodiment includes a developing container 110 that contains a two-component developer including at least a magnetic carrier and toner, and an agitation roller 120 a that is disposed inside the developing container 110. 120b, a magnetic roller 130 as a developer carrier disposed above the one stirring roller 120a in the vertical direction, and a layer thickness regulating blade (regulating member) 140 disposed in the vicinity of the magnetic roller 130, A scattering toner capturing cover 141 disposed above the layer thickness regulating blade 140 in the vertical direction, a developing roller 150 serving as a toner carrier disposed opposite to the magnetic roller 130, and a second magnetic brush rotating body 250 A rotation drive unit 260 for rotating the second magnetic brush rotating body 250, and a second magnetic brush rotation by the rotation drive unit 260. It includes a rotation control section 261 for changing the rotational speed of the body 250.

To the developing container 110, the toner 192 is supplied from the toner cartridge 5a (see FIG. 1) via the toner supply unit 6a (see FIG. 1).
The stirring rollers 120a and 120b stir the two-component developer 190 stored in the developing container 110. In the stirred two-component developer 190, static electricity is generated due to friction, the magnetic carrier (carrier) 191 is negatively charged, and the toner 192 is positively charged. Further, the toner 192 adheres to the magnetic carrier 191 due to electrostatic force.

The magnetic roller 130 is rotatable in a predetermined direction around the rotation center 130C and forms the surface of the magnetic roller 130, and a plurality of magnetic roller magnetic pole members 132 to 136 disposed inside the magnetic sleeve 131. .
The magnetic sleeve 131 has a cylindrical shape and is made of a nonmagnetic member. The magnetic sleeve 131 is rotationally driven in the direction of arrow B shown in FIGS. A first bias voltage is applied to the magnetic sleeve 131 by a voltage application unit (not shown).

As shown in FIGS. 2 and 3, the plurality of magnetic roller magnetic pole members 132 to 136 are fixed inside the magnetic sleeve 131 along the rotational direction of the magnetic roller 130 at a predetermined interval.
The first magnetic roller magnetic pole member 132 is fixedly disposed at a position closest to the developing roller 150 in the magnetic roller 130. The first magnetic roller magnetic pole member 132 is arranged so that the N pole is located on the outer side (the peripheral surface side of the magnetic sleeve 131).

  The other magnetic roller magnetic pole members 133 to 136 are fixed inside the magnetic sleeve 131 at a predetermined interval upstream of the first magnetic roller magnetic pole member 132 in the rotational direction B. The magnetic roller magnetic pole members 133, 134, and 136 are arranged so that the S pole is located on the outer side (the peripheral surface side of the magnetic sleeve 131). The magnetic roller magnetic pole member 135 is arranged so that the N pole is located on the outer side (the peripheral surface side of the magnetic sleeve 131).

  As shown in FIGS. 3 and 4, a part of the two-component developer 190 accommodated in the developing container 110 is held on the surface of the magnetic sleeve 131 by the magnetic force of the magnetic roller magnetic pole members 132 to 136. The two-component developer 190 held on the surface of the magnetic roller 130 forms a developer layer (magnetic brush) 194.

  The layer thickness regulating blade 140 is positioned below a horizontal plane 130H passing through the rotation center 130C of the magnetic roller 130. The layer thickness regulating blade 140 is a layer of the developer layer 194 formed by the two-component developer 190 held on the surface of the magnetic roller 130 by causing the tip portion 142 to face and approach the surface of the magnetic roller 130. The thickness (height) is regulated, and the layer thickness of the developer layer 194 that has passed through the layer thickness regulating blade 140 is kept constant. The layer thickness regulating blade 140 is made of a plate-like member. A predetermined gap (gap) is formed between the tip 142 of the layer thickness regulating blade 140 and the surface of the magnetic sleeve 131.

  The scattered toner capturing cover 141 is a member constituting a part of the case body of the developing device 16a. The scattered toner capturing cover 141 is disposed on the upper side in the vertical direction of the layer thickness regulating blade 140 (left side in FIG. 2), and suppresses the toner 192 from being scattered outside the developing device 16a.

  The developing roller 150 is disposed to face the magnetic roller 130. A toner layer 193 is formed on the surface of the developing roller 150 by the toner 192 moved from the magnetic roller 130. Specifically, the toner 192 is moved from the developer layer (magnetic brush) 194 whose layer thickness is regulated by the layer thickness regulating blade 140 to the surface of the developing roller 150, and the toner layer 193 is formed. The developing roller 150 includes a developing sleeve 151 that constitutes the surface of the developing roller 150, and a first developing roller magnetic pole member 152 and a second developing roller magnetic pole member 153 that are disposed inside the developing sleeve 151.

The developing sleeve 151 has a cylindrical shape and is made of a nonmagnetic member. The developing sleeve 151 is rotationally driven at a position facing the magnetic sleeve 131 so as to be in the same direction as the moving direction of the magnetic sleeve 131 (the direction of the arrow C shown in FIGS. 2 and 3). That is, the rotation direction C of the developing roller 150 is set to the forward direction (trailing direction) with respect to the rotation direction B of the magnetic roller 130.
A second bias voltage is applied to the developing sleeve 151 of the developing roller 150 by the voltage applying unit 262.

  The first developing roller magnetic pole member 152 is fixedly disposed in the developing sleeve 151 so as to face the first magnetic roller magnetic pole member 132. The first developing roller magnetic pole member 152 is disposed at a predetermined interval with respect to the region where the magnetic roller 130 and the developing roller 150 are closest to each other. In other words, the first developing roller magnetic pole member 152 and the first magnetic roller magnetic pole member 132 are arranged to face each other across the region where the developing sleeve 151 and the magnetic sleeve 131 are closest to each other.

  The first developing roller magnetic pole member 152 has a polarity different from the outer polarity of the first magnetic roller magnetic pole member 132 at the end on the side facing the first magnetic roller magnetic pole member 132. That is, the first developing roller magnetic pole member 152 is disposed so that the S pole is located on the outer side (the peripheral surface side of the developing sleeve 151). Further, the second developing roller magnetic pole member 153 is arranged so that the N pole is located on the outer side (the peripheral surface side of the developing sleeve 151).

A first magnetic field 171 is formed between the first magnetic roller magnetic pole member 132 arranged inside the magnetic roller 130 and the first developing roller magnetic pole member 152 arranged inside the developing roller 150. The In the region where the magnetic field 171 is formed between the magnetic roller 130 and the developing roller 150, the developer layer 194 rises from the surface of the magnetic roller 130 under the influence of the first magnetic field 171 to form a magnetic brush. In contact with the developing roller 150.
Here, as will be described later, when the magnetic roller 130 pumps up and transfers the scattered toner accumulated on the scattered toner capturing cover 141, the scattered magnetic toner that is pumped up and transferred as described later. Is set to such a size that the magnetic brush including can easily pass through the gap between the magnetic roller 130 and the developing roller 150.

  The second magnetic brush rotator 250 is disposed at a position upstream of the rotational directions B and C of the rollers 150 and 130 from the closest position 161 where the surface of the developing roller 150 and the surface of the magnetic roller 130 are closest to each other. Is done. The second magnetic brush rotator 250 receives a part of the developer layer (magnetic brush) 194 formed on the surface of the magnetic roller 130, forms a second magnetic brush 195 on the surface, and applies it to the developing roller 150. Contact.

  The second magnetic brush rotator 250 includes a rotation drive unit 260 and a rotation control unit 261 that changes the rotation speed of the second magnetic brush rotator 250 by the rotation drive unit 260. The rotation control unit 261 controls the rotation driving unit 260 so that the linear velocity of the second magnetic brush rotator 250 is the same as the linear velocity of the magnetic roller 130 during normal printing for printing on the paper T. In addition, the rotation control unit 261 has a linear velocity of the second magnetic brush rotor 250 of, for example, 1.5 times or more, preferably 2 or more times the linear velocity of the magnetic roller 130 when printing is not performed on the paper T. Thus, the rotation drive unit 260 is controlled so that the rotation speed of the second magnetic brush rotor 250 is changed (switched) in two stages.

The second magnetic brush rotator 250 is rotatable in a predetermined direction and has a second magnetic sleeve 251 that forms the surface of the second magnetic brush rotator 250, and a plurality of rotations arranged inside the magnetic sleeve 25. Body magnetic pole members 252 to 257.
The diameter D2 of the second magnetic brush rotating body 250 is set to, for example, one half or less of the diameter D1 of the magnetic roller 130, and preferably one third or less of the diameter D1 of the magnetic roller 130. .

  The second magnetic sleeve 251 has a cylindrical shape and is made of a nonmagnetic member. The second magnetic sleeve 251 is rotationally driven (trail rotationally driven) in the forward direction with respect to the direction of the arrow A shown in FIGS. 2 and 3, that is, the rotational direction C of the developing roller 150. A third bias voltage is applied to the second magnetic sleeve 251 by a voltage application unit (not shown).

As shown in FIGS. 2 and 3, the plurality of rotating body magnetic pole members 252 to 257 are fixed inside the second magnetic sleeve 251 at a predetermined interval along the rotation direction of the second magnetic brush rotating body 250. Is done.
Of the plurality of rotating body magnetic pole members 252 to 257, the first rotating body magnetic pole member 252 is fixedly disposed at a position closest to the developing roller 150 in the second magnetic brush rotating body 250. The first magnetic roller magnetic pole member 252 is disposed so that the S pole is located on the outer side (the peripheral surface side of the second magnetic sleeve 251).

  The other rotating body magnetic pole members 253 to 257 are fixed inside the second magnetic sleeve 251 with a predetermined interval on the upstream side in the rotational direction A from the first rotating body magnetic pole member 252.

  As shown in FIG. 4, a part of the two-component developer 190 accommodated in the developing container 110 is separated from the surface of the magnetic sleeve 131 by the magnetic force of the plurality of rotating body magnetic pole members 252 to 257 from the surface of the magnetic sleeve 131. It is taken up by 250 and held on the surface of the second magnetic sleeve 251. The two-component developer 190 held on the surface of the second magnetic sleeve 251 forms a developer layer (magnetic brush) 195.

  The first magnetic pole member 252 of the second magnetic brush rotor 250 has a developing roller sandwiching a region where the developing sleeve 151 and the second magnetic sleeve 251 are closest to each other inside the second magnetic sleeve 251. The second developing roller magnetic pole member 153 on the 150 side is disposed opposite to the first developing roller magnetic pole member 153.

  In the first rotator magnetic pole member 252, the end of the developing roller 150 on the side facing the second developing roller magnetic pole member 153 has a polarity different from the outer polarity of the second developing roller magnetic pole member 153. That is, the first rotor magnetic pole member 252 is disposed so that the S pole is located on the outer side (the peripheral surface side of the second magnetic sleeve 251). As a result, the second rotating magnetic pole member 252 disposed inside the second magnetic brush rotating body 250 and the second developing roller magnetic pole member 153 disposed inside the developing roller 150 have a second gap. The magnetic field 172 is formed. In the region where the second magnetic field 172 is formed between the second magnetic brush rotating body 250 and the developing roller 150, the developer layer 195 is affected by the second magnetic field 172, and the second magnetic brush It rises from the surface of the rotator 250, forms a magnetic brush, and contacts the developing roller 150.

Next, the operation of the developing device 16a of this embodiment will be described with reference to FIGS.
In the developing device 16a of this embodiment, the two-component developer 190 supplied from the toner cartridge 5a (see FIG. 1) is first stirred by the stirring rollers 120a and 120b and circulates in the developing container 110. Thereby, static electricity due to friction is generated in the stirred two-component developer 190, the magnetic carrier 191 is negatively charged, and the toner 192 is positively charged. Further, the toner 192 adheres to the magnetic carrier 191 due to electrostatic force.

The two-component developer 190 charged in the developing container 110 is held on the surface of the magnetic roller 130 rotating in the rotation direction B by the magnetic force of the magnetic roller magnetic pole members 132 to 136 disposed in the magnetic sleeve 131. . A developer layer (magnetic carrier) 194 is formed on the surface of the magnetic roller 130 by the magnetic force of the magnetic roller magnetic pole members 134 and 135.
The developer layer 194 formed on the surface of the magnetic roller 130 is rotated and moved with the rotation of the magnetic sleeve 131 and is brought into contact with the layer thickness regulating blade 140 and regulated to a predetermined layer thickness.

  The developer layer 194 regulated to a predetermined layer thickness by the layer thickness regulating blade 140 is rotated and moved to the vicinity of the position facing the second magnetic brush rotating body 250 as the magnetic roller 130 rotates. In this region, a part of the developer layer 194 is rotated by the second magnetic brush rotated in the rotation direction A by the magnetic force of the rotating body magnetic pole members 252 to 257 disposed inside the second magnetic brush rotating body 250. A developer layer (magnetic brush) 195 is formed on the surface of the body 250.

  Further, the remainder of the developer layer 194 formed on the surface of the magnetic roller 130 and regulated to a predetermined layer thickness is composed of the first magnetic roller magnetic pole member 132 of the magnetic roller 130 and the first developing roller magnetic pole member 152 of the developing roller 150. Is moved to the vicinity of the opposite position, and reaches the region where the first magnetic field 171 is formed. In this region, the developer layer 194 rises under the influence of the first magnetic field 171 and contacts the developing roller 150.

  Further, the developer layer 195 held on the surface of the second magnetic brush rotator 250 is moved in the vicinity of the position where the second magnetic brush rotator 250 and the developing roller 150 face each other, and the second magnetic field 172 is moved. Pass through the formed area. In this region, the developer layer 195 rises under the influence of the second magnetic field 172 having a strong magnetic binding force and contacts the developing roller 150.

  The toner 192 that is positively charged in the developer layer 195 held on the surface of the second magnetic brush rotator 250 is applied to the third bias voltage applied to the second magnetic brush rotator 250 and the developing roller 150. The first toner layer 196 is formed on the surface of the developing roller 150 by being transferred to the developing roller 150 side in accordance with the potential difference with the applied second bias voltage.

  On the other hand, the developer layer 194 held on the surface of the magnetic roller 130 is moved in the vicinity of the position where the magnetic roller 130 and the developing roller 150 face each other, and passes through the region where the first magnetic field 171 is formed. In this region, the developer layer 194 rises under the influence of the first magnetic field 171 having a strong magnetic binding force, contacts the surface of the developing roller 150, and is positively charged in the developer layer 194. Is transferred to the developing roller 150 side according to the potential difference between the first bias voltage applied to the magnetic roller 130 and the second bias voltage applied to the developing roller 150. As a result, the second toner layer 197 is formed on the surface of the first toner layer 196 formed on the surface of the developing roller 150. The first toner layer 196 and the second toner layer 197 form a toner layer 193 having a predetermined thickness on the surface of the developing roller 150.

  Thereafter, the surface of the developing roller 150 on which the toner layer 193 having a predetermined thickness is formed faces the surface of the photosensitive drum 2a (see FIG. 1) on the downstream side in the rotation direction C. In the developing area, the electrostatic latent image is developed by the potential difference between the developing roller 150 and the photosensitive drum 2a. That is, on the photosensitive drum 2a, an electrostatic latent image is formed on the surface, and toner is supplied from the toner layer 193 of the developing device 16a to form a toner image on the electrostatic latent image.

As shown in FIG. 1, the toner images developed on the photosensitive drum 2 a are sequentially primary transferred onto the intermediate transfer belt 7. The toner image primarily transferred to the intermediate transfer belt 7 is secondarily transferred to the paper T by the secondary transfer roller 8. The toner image secondarily transferred to the paper T is conveyed to the fixing unit 9, and the toner is fixed to the paper T by the fixing unit 9.
Thereafter, the paper T is transported to the first paper discharge unit 50a through the third transport path L3, and is discharged from the first paper discharge unit 50a to the paper discharge stacking unit M1. In this way, printing of the paper T by the copying machine 1 is completed.

  During the developing operation by the developing device 16a as described above, the scattered toner 198 scattered outward from the magnetic roller 130 is captured by the scattered toner capturing cover 141 and gradually accumulated. When the amount of the scattered toner 198 captured and deposited by the scattered toner capturing cover 141 reaches a certain level or more, the deposited scattered toner 198 is pumped up by the magnetic roller 130. The scattered toner 198 pumped up by the magnetic roller 130 is moved to the vicinity of the position where the magnetic roller 130 and the developing roller 150 face each other as the magnetic roller 130 rotates.

  Here, since the magnetic roller 130 and the developing roller 150 are rotating in the forward direction (trail rotation), the scattered toner pumped up by the magnetic roller 130 and moved to the vicinity of the position where the magnetic roller 130 and the developing roller 150 face each other. 198 passes through the gap between the magnetic roller 130 and the developing roller 150. As the scattered toner 198 passes through the gap between the magnetic roller 130 and the developing roller 150, the scattered toner 198 is loosened under the influence of the first magnetic field 171.

Most of the loosened toner 198 loosened in this way is dropped and collected inside the developing container 110, and the developer 190 containing the dropped collected toner is stirred and charged by the stirring rollers 120a and 120b. It will be.
On the other hand, part of the scattered toner 198 that has passed through the gap between the magnetic roller 130 and the developing roller 150 adheres to the surface of the developing roller 150, but passes through the gap between the magnetic roller 130 and the developing roller 150. At this time, since it is loosened under the influence of the first magnetic field 171, it is possible to suppress the occurrence of image defects due to toner dropping due to adhering to the toner layer 193 on the surface of the developing roller 150.

  In addition, the second magnetic brush rotator 250 rotates at the same speed as the linear velocity of the magnetic roller 130 during normal printing in which the rotation control unit 261 performs printing on the paper T. Although not controlled, when printing is not performed on the paper T, rotation (switching) is controlled so that the linear velocity of the second magnetic brush rotor 250 is at least twice the linear velocity of the magnetic roller 130. Thereby, the supply performance (development ghost performance) of the developer 190 from the second magnetic brush rotator 250 to the development roller 150 is sufficiently maintained during non-printing.

According to the developing device 16a in the copier 1 of the present embodiment, for example, the following effects are exhibited.
In the present embodiment, the tip portion 142 is brought close to the surface of the magnetic roller 130, so that the layer thickness regulating blade 140 that regulates the amount of the developer 190 carried on the magnetic roller 130 and the magnetic roller 130 scatter outward. A scattering toner capturing cover 141 that captures and deposits toner, and the rotation direction C of the developing roller 150 is set to the forward rotation direction with respect to the rotation direction B of the magnetic roller 130.

  Therefore, when the scattered toner 198 deposited on the scattered toner capturing cover 141 that captures the toner scattered outward from the magnetic roller 130 is pumped up by the magnetic roller 130, the pumped-up scattered toner 198 is magnetized. The gap between the roller 130 and the developing roller 150 can be passed through and loosened. Thereby, it is possible to suppress the occurrence of image defects due to toner dropping due to the scattered toner 198 pumped up by the magnetic roller 130 being attached to the toner layer 193 on the surface of the developing roller 150.

In the present embodiment, the second magnetic brush rotating body 250 is provided at a position upstream of both rollers 150 and 130 from the closest position 161 where the developing roller 150 and the magnetic roller 130 are closest to each other. .
Therefore, the supply performance (development ghost performance) of the toner layer 193 from the magnetic roller 130 to the development roller 150 that decreases as the development roller 150 and the magnetic roller 130 rotate with respect to the trail rotates. Can be compensated by. As a result, it is possible to suppress the occurrence of image defects due to toner dropping while sufficiently maintaining the ghost performance of the toner layer 193 on the developing roller 150.

In the present embodiment, the diameter D2 of the second magnetic brush rotor 250 is set to be less than or equal to one half of the diameter D1 of the magnetic roller 130.
Therefore, it is easy to install the second magnetic brush rotor 250 without providing a special installation space inside the developing device 16a. For example, the space above the scattered toner capturing cover 141 is used. Thus, the second magnetic brush rotating body 250 can be installed. Thereby, the ghost performance as described above can be ensured while the entire developing device 16a is made compact and compact.

Further, in the present embodiment, the rotation speed of the second magnetic brush rotor 250 can be changed to a speed that is at least twice the rotation speed of the magnetic roller 130.
Therefore, when continuous printing is performed over a long period of time by changing the rotation speed of the second magnetic brush rotor 250 to at least twice the rotation speed of the magnetic roller 130 during non-printing. Further, it is possible to suppress the problem of image defects caused by the scattered toner adhering to the developing roller 150.

As mentioned above, although preferred embodiment of this invention was described, this invention can be implemented with a various form, without being limited to embodiment mentioned above.
For example, in the above-described embodiment, the case where the toner 192 is positively charged has been described. However, the present invention is not limited to this. The toner 192 may be negatively charged. Specifically, in the above-described embodiment, the case where the positively charged toner 192 is used has been described. As described above, when the positively charged toner 192 is used, the difference between the first bias voltage and the second bias voltage is increased.

On the other hand, when the negatively charged toner 192 is used, the difference between the first bias voltage and the second bias voltage is reduced. Accordingly, even when the negatively charged toner 192 is used, the same effect as that of the above-described embodiment can be obtained.
Except for this point, the configuration, operation, and effect when the negatively charged toner 192 is used are the same as those when the positively charged toner 192 is used.

  The above-described embodiment is a color indirect transfer type image forming apparatus that transfers a plurality of color toner images onto the paper T using the intermediate transfer belt 7, but the type of the image forming apparatus is not limited to this, The image forming apparatus may be a direct transfer type that does not use an intermediate transfer belt, or an image forming apparatus for monochrome printing.

The type of the image forming apparatus of the present invention is not particularly limited, and may be a color copier, a printer, a facsimile, or a complex machine thereof.
The sheet-shaped transfer material is not limited to the paper T, and may be a film sheet, for example.

Next, experimental examples performed using Examples 1 to 3 of the present invention and a comparative example will be described. However, the present invention is not limited only to the following experimental examples.
Example 1: The magnetic roller 130 and the developing roller 150 rotate in the trail (rotate in the forward direction).
Example 2: The magnetic roller 130 and the developing roller 150 rotate in the trail, and include a second magnetic brush rotating body 250.
Embodiment 3 The magnetic roller 130 and the developing roller 150 are rotated in the trail, and the second magnetic brush rotating body 250 is provided. The linear velocity of the second magnetic brush rotating body 250 is set to the linear velocity of the magnetic roller 130 during non-printing. Rotation control to change to more than 2 times is performed.
Comparative example: The magnetic roller 130 and the developing roller 150 are counter-rotated (rotated in the reverse direction).

The specifications of the image forming apparatuses of Examples 1 to 3 and the comparative example used in the experiment are as follows.
Photosensitive drum 2a
Diameter: 30 mm, peripheral speed: 200 mm / sec, surface potential: 250 V
Development roller 150
Diameter: 20 mm, peripheral speed: 300 mm / sec, applied voltage: Vdc = 100 V, Vpp 1.8 kV, frequency f = 4.5 kHz, duty ratio = 70%
Magnetic roller 130
Diameter: 20 mm, peripheral speed: 450 mm / sec, applied voltage: Vdc = variable, Vpp = 1.8 kV, frequency f = 4.5 kHz, duty ratio = 70%
Second magnetic brush rotor 250
Diameter: 20 mm, peripheral speed: 450 mm / sec, applied voltage: Vdc = variable, Vpp = 1.8 kV, frequency f = 4.5 kHz, duty ratio = 70%
Distance between rollers Distance between magnetic roller 130 and developing roller 150 = 320 mm
Distance between second magnetic brush rotor 250 and developing roller 150 = 320 mm
Distance between developing roller 150 and photosensitive drum 2a = 100 mm

  As the two-component developer 190, a toner having an average particle diameter of 6 μm, an average particle diameter of carrier: 35 μm, and a charge amount of toner: 15 μC / g was used.

  Using the image forming apparatus manufactured according to the above specifications, a durability test is performed for the number of printed sheets from 1000 (10K) to 3000 (30K), and the number of occurrences of toner drop at that time is counted, and the developing roller 150 The transition of the supply performance (development ghost performance) level of the toner layer 193 on the surface of the toner and the adhesion level of scattered toner to the development roller 150 were measured, and each item was evaluated.

Table 1 is a table showing the results of the number of occurrences of toner drop when the above-described durability test is performed. Table 2 is a table showing the transition result of the development ghost performance level. Table 3 is a table showing the transition result of the adhesion level of the scattered toner.
The evaluation criteria in Table 2 are as follows.
○: Ghost performance is high level Δ: Ghost performance is medium level ×: Ghost performance is low level The evaluation criteria in Table 3 are as follows.
○: Small amount of scattered toner attached △: Medium amount of scattered toner attached ×: Large amount of scattered toner attached

From the above experimental results, in Examples 1 and 2 in which the magnetic roller 130 and the developing roller 150 are rotated by the trail, the number of occurrences of toner drop when performing continuous printing is significantly reduced compared to the comparative example. Was confirmed. In Example 2 in which the second magnetic brush rotator 250 was provided, the development ghost performance was superior to that in Example 1 in which the second magnetic brush rotator 250 was not provided.
Further, the rotational speed of the second magnetic brush rotor 250 is changed and controlled so that the linear velocity of the second magnetic brush rotor 250 is at least twice the linear velocity of the magnetic roller 130 during non-printing. In Example 3, it was confirmed that the scattered toner adhered to the developing roller 150 was superior to Examples 1 and 2 having the same linear velocity.

DESCRIPTION OF SYMBOLS 1 ... Copy machine (image forming apparatus), 2a, 2b, 2c, 2d ... Photosensitive drum (image carrier), 16a, 16b, 16c, 16d ... Developing device, 130 ... Magnetic roller (Developer carrying) Body), 131C ... rotation center, 131H ... horizontal surface, 140 ... layer thickness regulating blade (regulating member), 141 ... scattered toner capturing cover, 142 ... tip, 150 ... developing roller (toner carrier) 161 ... closest position, 190 ... two-component developer, 191 ... magnetic carrier, 192 ... toner, 193 ... toner layer, 194 ... developer layer (magnetic brush), 250 ... second Magnetic brush rotator, 261... Voltage application unit, D1... Diameter of magnetic roller (developer carrier), D2... Diameter of second magnetic brush rotator, A. Direction of rotation, B ... La rotation direction of the rotating direction of the (developer carrying member), C ...... developing roller (toner carrier), T ...... paper (transfer material)

Claims (6)

A developer carrying rotor that carries a two-component developer containing at least a carrier and a toner, and a magnetic brush formed of a carrier contained in the two-component developer is formed on the surface;
A toner-carrying rotator that is disposed oppositely over the developer-carrying rotator and that carries toner supplied from the developer-carrying rotator and forms a toner layer with the magnetic brush;
In order to develop the electrostatic latent image as a toner image by causing the toner carried on the toner carrying rotator to fly to the electrostatic latent image on the surface of the image carrier, the toner carrying rotator and the image carrier A voltage application unit for applying a development bias voltage therebetween,
The amount of developer carried on the developer-carrying rotator is positioned below a horizontal plane passing through the rotation center of the developer-carrying rotator and the front end is brought close to the surface of the developer-carrying rotator. A regulating member that regulates,
A scattering toner capturing cover that is disposed above the regulating member and captures and deposits toner scattered outward from the developer carrying rotor,
A developing device in which a rotation direction of the toner carrying rotator is set to a forward rotation direction with respect to a rotation direction of the developer carrying rotator. 2. The second magnetic brush rotator is further provided at a position upstream of both of the carrying rotators from a closest position where the toner carrying rotator and the developer carrying rotator are closest to each other. Development device. The developing device according to claim 2, wherein a rotation direction of the second magnetic brush rotating body is set to a forward rotation direction with respect to a rotation direction of the toner carrying rotating body. 4. The developing device according to claim 2, wherein a diameter of the second magnetic brush rotator is set to a half or less of a diameter of the developer carrying rotator. 5. 5. The structure according to claim 2, wherein the second magnetic brush rotator is configured to be capable of changing its rotation speed to a speed that is at least twice that of the developer carrying rotator. The developing device described. A developing device according to any one of claims 1 to 5;
One or more image carriers on which an electrostatic latent image is formed and a toner image is formed on the electrostatic latent image upon receipt of toner from the toner layer of the developing device;
A transfer unit that directly or indirectly transfers the toner image formed on the image carrier to a sheet-like transfer material;
An image forming apparatus comprising: a fixing unit that fixes a transferred toner image to a sheet-like transfer material.

Images