JP2002014528A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize a whole device without causing unevenness in concentration of developer in a developing device of a vertical type agitating system provided with a first agitating and carrying means and a second agitating and carrying means in the top and the bottom. SOLUTION: In the device, a developer scooping up means 82 and a developer dropping means 200 are respectively provided outside an effective developing range D of a developer feeding means 146, and a sealing means 210 to seal the developer is provided in between the developer dropping means 200 and the first agitating and carrying means 68.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for supplying and developing a developer to a photosensitive drum in an image forming apparatus such as a copying machine or a printer, and more particularly to a two-component developer comprising a toner and a carrier. The present invention relates to a developing device having the following configuration.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus such as a copying machine or a laser printer uses a two-component developer composed of a toner and a carrier to develop an electrostatic latent image formed on a photosensitive drum. Is applied to the developing device. This electrostatic latent image developing apparatus is developed by a developing housing such as a developing housing that stores a developer, a developing sleeve that forms a magnetic brush that supplies the developer in the developing housing to the electrostatic latent image on the photosensitive drum, and the like. A developer supply means, a developer stirring / conveying means typified by a spiral or screw member which stirs and conveys a developer in a developing housing in a predetermined direction, and a toner storage tank typified by a toner hopper etc. in the developing housing. And toner supply means for supplying toner. The developer supply means supplies toner to the electrostatic latent image in a development area of the photosensitive drum,
The photosensitive drum is developed into a toner image. When the toner in the developing housing is consumed according to the supply of the toner to the electrostatic latent image, the toner is supplied by the toner supply unit. The developer stirring / conveying means stirs the developer in the developing housing to stir the toner and the carrier, mixes and frictionally charges the toner and the carrier, and conveys them in a predetermined direction. Japanese Patent Application Laid-Open No. H10-142942 discloses a developer supply device for supplying a developer to a photosensitive drum and a developer supply device for supplying the developer to the photosensitive drum. A first stirring / transporting means provided in the vicinity for stirring and transporting the developer in a first direction; and a developer provided below the first stirring / transporting means and moving the developer in a second direction opposite to the first direction. A second stirring / conveying unit for stirring the developer, and a developer provided coaxially with the developer supplying unit, driven by the driving of the developer supplying unit, and conveyed by the second stirring / conveying unit. And a feeding means for feeding the first stirring and conveying means to the first stirring and conveying means. This developing device can have a very compact structure by employing a so-called "vertical circulation system" in which a stirring and conveying means is vertically arranged separately as a stirring method for a two-component developer. For this reason, it is disclosed that the present invention is particularly effective in a color copying machine of a quadruple tandem development system.

Generally, in a developing device employing a "longitudinal circulation system" represented by the above-mentioned publication, the developer present in a vertically divided stirring / stirring / conveying path is dropped from top to bottom in the direction of gravity, and It is necessary to provide a feeding means (pumping means) for pumping up the developer against gravity from above.
For this reason, the developer moves horizontally in the divided stirring conveyance path, a region moving while falling in the direction of gravity,
There is a region that moves against gravity, and it is extremely difficult to smoothly carry and stir and transport without causing bias of the developer.

In order to solve such a technical problem, the above publication focuses on a feeding means for pumping the developer, and employs a specific feeding means to collect the developer in the pumping area (the developer is conveyed). (A portion that stagnates without being stopped) is prevented. Specifically, the agitated conveyance path divided into upper and lower portions is formed sufficiently longer than the developing sleeve having a built-in magnet roller for developing the electrostatic latent image formed on the surface of the photoreceptor, and is coaxial with the developing roller. A configuration is adopted in which a rotating shaft of a sleeve having a built-in magnet roller as a "feeding means" is provided.

[0005]

In the above-mentioned publication, a smooth circulation can be ensured without applying stress to the developer by employing a specific "feeding means". However, here the length 3
Since the "feeding means" containing a 70 mm magnet roll is coaxially arranged with respect to the developing sleeve containing a 08 mm magnet roller, the amount of protrusion in the longitudinal direction with respect to the development area is very large. . Although sufficient consideration has been given to the pumping of the developer from the bottom to the top, no consideration is given to the fall of the developer from the top to the bottom. For this reason, there is still room for improvement in ensuring smoother developer circulation and designing the developing device more compactly. In particular, in color image formation, even if slight unevenness in toner density occurs in the development area, the image is affected, and there is a problem that a desired color tone cannot be obtained.
Further improvement is desired.

According to the present invention, in a developing device of a vertical stirring type provided with a first stirring and conveying means and a second stirring and conveying means on the upper and lower sides, the developer is sufficiently stirred, and the toner concentration of the developer in a developing region is increased. It is an object of the present invention to effectively prevent unevenness and to reduce the size of the entire device, particularly to shorten the length in the axial direction.

[0007]

In order to solve the above-mentioned problems, a first aspect of the present invention is a developer supply means for supplying a developer to a latent image carrier to visualize the latent image carrier, and a developer supply means for supplying the developer to the latent image carrier. A first stirring and conveying means provided near the means for stirring and transporting the developer in a predetermined direction; and a first stirring and conveying means provided below the first stirring and conveying means for stirring the developer and opposed to the first stirring and conveying means. A second stirring / transporting means for conveying the developer in the first direction, a developer pumping means for supplying the developer in the second stirring / conveying means to the first stirring / conveying means, and a developer in the first stirring / conveying means. Developer dropping means for supplying to the stirring and conveying means of No. 2;
The developer pumping means and the developer dropping means are respectively provided outside the effective developing area of the developer supply means, and the developer is blocked between the developer dropping means and the first stirring and conveying means. It is characterized by having closing means for stopping.

According to this configuration, in a so-called vertical circulation type developing device, both the developer pumping means and the dropping means are provided outside the effective developing area of the developer supply means, and the developer dropping means and the first agitator are provided. By having a closing means for closing the developer between the conveying means and the conveying means, the second stirring / transporting means only allows horizontal conveying by stirring over the entire effective developing area of the developer supplying means. In addition, since the blocking means is provided between the dropping means and the first stirring and conveying means, the developer is sufficiently ensured at this portion. It is possible to stably supply the developer to the stirring and conveying means.

Further, as the developer pumping means, a rotating body having a plurality of magnetic poles in a circumferential direction provided at a substantially central portion in a height direction of the first stirring and conveying means and the second stirring and conveying means is used. (Claim 2). According to this configuration, it can be pumped up from the second stirring and conveying means and supplied to the upper first stirring and conveying means with a compact structure.

Further, the developer dropping means is provided on a partition wall which separates an upper chamber in which the first stirring and conveying means is stored and a lower chamber in which the second stirring and conveying means is stored. The opening is provided (claim 3). According to this configuration, the developer is supplied from the first stirring and conveying means to the second stirring and conveying means by its own weight. As a result, the developing device itself can be designed compact.

Further, the first and second stirring and conveying means have a structure in which a rotatable shaft peripheral surface has a blade member formed in a spiral shape in the longitudinal direction thereof. According to this configuration, the developer can be stirred and transported without applying excessive stress to the developer.

Further, the developer conveying speed of the second stirring and conveying means is set to be higher than that of the first stirring and conveying means (claim 5). Alternatively, an outer diameter of the second stirring and conveying means is smaller than an outer diameter of the first stirring and conveying means.

In the vertical circulation developing system as in the present invention, unless the transport amount of the developer by the vertically divided stirring transport mechanism is made substantially constant, the developer is accumulated somewhere, and the transported developer is generated. This causes a so-called pulsation. Therefore, the transport amount by the first and second stirring transport mechanisms is controlled so as to be substantially constant within a range in which no excessive bias occurs. By the way, the first stirring / conveying mechanism replenishes a developer having a toner concentration insufficient by a developing means pumped by a pumping means with new toner, and then mixes the toner so as to have a uniform toner concentration, and mixes the toner with the toner. It is desired to mix and agitate sufficiently with the carrier in order to impart sufficient charge.

On the other hand, the second stirring / conveying mechanism, which is provided adjacent to the developer supply mechanism, is a developer in which toner has been consumed in the developing area (a developer whose toner density is lower than the reference density). It is necessary to prevent an extreme shortage of the toner concentration by scraping the toner and mixing and stirring with the surrounding developer. That is, the second stirring / transporting device is promptly replaced with the developer having an appropriate toner concentration supplied from the first stirring / transporting device via the dropping means, not to mention mixing and stirring of the developer. Is desired. In this case, it is desirable that the first stirring / transporting means move the developer slowly over time, and conversely, the second stirring / transporting means quickly moves within a range that does not apply excessive stress to the developer.

Therefore, the developer conveying speed (moving speed) of the second stirring and conveying means is set higher than the developer conveying speed (moving speed) of the first stirring and conveying means, and the stirring and mixing speed is further increased. The replacement of the developer whose toner has been consumed and the developer having the reference toner concentration is promptly performed. Further, in this case, in order to increase the second transport speed while keeping the transport amounts of the first and second developers constant, the outer diameter of the second stirring and transporting means is set to the second diameter. 1
Is smaller than the outer diameter of the agitating / conveying means, and the size of the developing device in the width direction can be designed to be smaller.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a developing device according to the present invention will be described in detail with reference to the drawings. [Overview of Image Forming Apparatus] FIG. 1 is a schematic configuration diagram of a color printer as an image forming apparatus according to an embodiment of the present invention.

A schematic configuration of a color printer to which the present invention is applied will be described with reference to FIG. The color printer 2 feeds a sheet member 3 as a transfer body one sheet at a time.
A transport unit 6 for transporting the sheet member 3 sent from the paper supply unit 4, an image forming unit 5 for forming a toner image to be transferred to the sheet member 3, and a toner image formed by the image forming unit 5. A transfer unit 7 for transferring the sheet member 3, a fixing unit 8 for fixing the toner image of the sheet member 3 transferred by the transfer unit 7, and a sheet discharging unit 10 for receiving the sheet member 3 discharged from the fixing unit 8. , An image forming unit 11.

The paper feed unit 4 includes a first paper feed unit 15 that feeds the sheet members 3 stacked on the first paper feed tray 12 to the downstream side one by one with a paper feed roller 13 and a retard roller 14.
And a second paper feed unit 18 that feeds the sheet members 3 from the manual feed tray 16 to the downstream side one by one by a paper feed roller 17.

The conveying section 6 includes a conveying path 20 for guiding the conveyance of the sheet member 3 sent from the first sheet feeding section 15 or the second sheet feeding section 18, and a conveying roller disposed in the middle of the conveying path 20. A registration roller pair 22 which receives the sheet member 3 from the conveying roller 21, temporarily stops the leading end of the sheet member 3, regulates (corrects) the oblique feeding, and sends it to the image forming unit 5 on the downstream side; And a manual feed path 23 connected to the feed path 20 upstream of the roller pair 22.

The image forming section 5 includes a first image forming section 24 having black toner, a second image forming section 25 having cyan toner, a third image forming section 26 having magenta toner, and a fourth image forming section having yellow toner. And a unit 27. The first to fourth image forming units 24, 25, 26, and 27 have a cylindrical photosensitive drum 28, a developing device 30 that forms a toner image on the photosensitive drum 28, and a residual image on the photosensitive drum 28. Fur brush 31 and cleaning blade 32 for removing toner
Cleaning device 33 including a photosensitive drum 28
And a charging device 34 for applying a charge thereon to uniformly charge the surface of the photosensitive drum 28.

The transfer section 7 is disposed at a position opposed to an endless transfer belt 37 made of a fluororesin material, a driving roller 38 and a tension roller 40 for driving the transfer belt 37, and each photosensitive drum 28. Transfer roller 4
1a, 41b, 41c, and 41d, and further has a function of transporting downstream. These transfer rollers 41a, 41b, 41c, 41d and each photosensitive drum 28
. Also, the transfer belt 37
Guide rollers 42 and 43 are provided at appropriate positions on the inner peripheral side. When forming only a black-and-white image, the transfer unit 7 uses only the black transfer roller 41a and transfers the other transfer rollers 41b, 41c for magenta, cyan, and yellow.
41d is separated from the photosensitive drum 28. The fixing unit 8 includes a heating roller 44 having a built-in heater, a fixing roller 45, a metal endless belt 46 wound around the heating roller 44 and the fixing roller 45, and a pressure applied to the fixing roller 45. And a roller 47.
An oil application roller 48 that applies silicone oil to the outer surface of the endless belt 46 and an oil application roller 4
An oil supply roller 50 for supplying oil to the oil supply 8 and a cleaning roller 51 for cleaning the surface of the oil supply roller 50 are arranged.

The sheet discharging section 10 receives the sheet member 3 discharged from the fixing section 8 and stacks the first sheet discharging section 52 with the image forming surface up and the sheet member 3 discharged from the fixing section 8. It has a second paper discharge unit 54 that is guided to the upper part of the image forming apparatus main body 36 via the discharge path 53 and is stacked with the image forming surface down. When the first paper discharge unit 52 is not used, it is accommodated in the image forming apparatus main body 36.

The optical unit 11 includes a polygon mirror 55
, Lenses 56, 57 and a mirror 58 are arranged corresponding to each photosensitive drum 28, and irradiate laser light toward each photosensitive drum 28 from a slit 61 formed in the optical unit support plate 60. It has become.

The color printer 2 having the above-described configuration is configured such that the first sheet feeding section 15 or the second sheet feeding section 18 feeds the sheet member 3.
Is transported, the sheet member 3 is transported by the transport unit 6 between the photosensitive drum 28 of the first image forming unit 24 and the transfer belt 37 of the transfer unit 7. The sheet member 3 includes the photosensitive drum 28 and the transfer rollers 41a, 41b, 4
While being conveyed by the transfer belt 37 between the photosensitive drums 1c and 41d, the toner images formed on the photosensitive drums 28 of black, magenta, cyan, and yellow are sequentially transferred to the sheet member 3. Then, the sheet member 3 on which the transfer of the color image has been completed is further conveyed by the transfer belt 37 and sent between the fixing roller 45 and the pressure roller 47 of the fixing unit 8, where the color image is fixed. After fixing, the sheet member 3
Is discharged to the first paper discharge unit 52 or the second paper discharge unit 54.

Next, the developing device according to the present embodiment will be described in detail. "Outline of Developing Apparatus" FIGS. 2A and 2B are perspective views showing a developing apparatus constructed in accordance with the present invention. FIG. 2A is a perspective view seen from the developing roller side, and FIG. FIG. 2 shows a partially cutaway perspective view as seen. FIG. 3 is a diagram showing FIG.
4 is a sectional view taken along line AA in FIG. 2, and FIG. 4 is a sectional view taken along line BB in FIG. FIG. 5 is a schematic diagram for explaining the arrangement and driving of the stirring and conveying device. The description will be made with reference to FIGS.

The developing device 30 has a developing housing 144 formed of a synthetic resin material. As shown in FIGS. 2 and 3, the developing housing 144 includes a first side wall 134 extending substantially vertically upward from the bottom wall 132 in substantially the entire area, and a first side wall 134 adjacent to the first side wall 134 and a pumping area described later. A second side wall 136 forming a part thereof and a front wall 13
8 (FIG. 2A), a rear wall 140 (FIG. 2B), an upper wall 142 at the top of the developing housing 144,
It is mainly composed of

The developer housing 144 is provided with developer supply means 146, a part of which is exposed on the photosensitive drum side for forming a latent image. The developer supply means 146 includes a cylindrical developing sleeve 148 made of a nonmagnetic material such as aluminum and extending substantially over the entire developing area in the axial direction (the left-right direction in FIG. 2). It is composed of the disposed magnet material 150. The sleeve 148 is rotatably connected to a drive system described later. The magnet material 150 is fixed at a predetermined position in the developing sleeve 148. As shown in FIG. 5, the rotating shaft 151 to which the developing sleeve 148 is fixed projects through the rear wall 140, and an input gear 152 is fixed to the protruding end. The driving force transmitted from a driving source (not shown) described later is transmitted to the input gear 152 through the output gear 154 and the idle gear 156. It then rotates in the direction indicated by arrow 158 in FIG.

Above the developer supply means 146, a developer layer regulating means 160 is provided. Developer layer regulating means 1
Numeral 60 designates a cutting blade 62 and the cutting blade 62
And a holding unit 64 for holding the. The holding section 64 is fixedly supported on the upper part of the front surface of a partition 66 for accommodating a first stirring and conveying means 68 described later. The lower end edge of the ear cutting blade 62 of the developer layer regulating means 160 is disposed so as to extend from the uppermost portion of the developing sleeve 148 slightly downstream in the rotation direction of the developing sleeve 148 over substantially the entire area in the axial direction. The lower edge of the blade 62 is located substantially at the center of the north pole and south pole in the upper part of the magnet material 150. The developer 1 that has been separated by the blade 62 and separated from the peripheral surface of the developing sleeve 148
00 is stirred and mixed by a second stirring and conveying means 70 described later, is attracted to the surface of the developing sleeve 148 again by magnetic force, and is applied to the next development.

On the back surface of the developer supply means 146 in the development housing 144, two developer stirring / transporting means arranged in parallel in the vertical direction are provided. Specifically, a first stirring and conveying means 68 is provided on the upper side in the developing housing 144, and a second stirring and conveying means 70 is provided on the lower side in parallel with the developing sleeve 148, and The two developer stirring / transporting means are separated from each other by a partition wall integrally formed with the developing housing 144. On the front wall 138 side of the developing device, a developer pumping unit 86 is located at an intermediate position when viewed in the height direction of the first and second stirring and conveying means 68 and 70, and on the rear wall side of the developing device. A toner concentration detecting means is provided on the back side of the first stirring and conveying means 68 (on the side opposite to the developing sleeve 148).

"Developer stirring and conveying means" Next, the developer stirring and conveying means will be described in detail with reference to FIG. FIG. 5 is a schematic view for explaining the positional relationship in the longitudinal direction of the first and second stirring and conveying means, and is not a cross-sectional view of the developing device perspective view shown in FIG. The developer stirring / conveying means includes a first stirring / conveying means 68 and a second stirring / conveying means 70 provided immediately below the first stirring / conveying means 68.

The first stirring and conveying means 68 includes a rotating shaft 72 rotatably mounted between a front wall 138 of the developing housing 144 and an inner wall 141 provided inside (left side) of the rear wall 140. Except for a region A1 at the downstream end of the rotating shaft 72 in the conveying direction of the developer 100 as indicated by an arrow 108, the spiral blade 7 formed substantially over the entire area in the axial direction.
And 4. This rotation shaft 72 is a front wall 138
The gear 80 protrudes further outward, and a gear 80 is provided at the left end thereof. A gear 75 is provided on the rotation shaft 72 also on the left side of the rear wall 140 and between the inner walls 141.

On the other hand, the second agitating / conveying means 70 includes a rotating shaft 76 rotatably mounted between the front wall 138 and the rear wall 140 of the developing housing 144, and a developing shaft indicated by an arrow 110 of the rotating shaft 76. A spiral blade 78 is formed substantially in the entire axial direction except for a region A2 at the downstream end of the agent 100 in the transport direction. An output gear 154 is fixed to the right end of the rotating shaft 76, and the rotating shaft 76 is attached to an inner wall 141 between the front wall 138 and the rear wall 140.
The gear 81 is mounted on the gear 75 and is drivingly connected to the gear 75. Then, the first and second stirring and conveying means 68,
The number of rotations of the gear 70 is controlled by the gear ratio between the gears 75 and 81, and the rotation of the gear 70 can be performed by a driving force from the same driving source (not shown) so as to convey the developer in the opposite direction.

The first and second stirring / conveying means having the above-described structure basically achieves a smooth stirring / conveying circulation of the developer.
Are set so that the developer transport force of the spiral blades 74 and 78 is substantially equal. The size and shape (twist direction) of the spiral blades 74 and 78, the pitch and the turning direction (right-handed or left-handed) of the spiral, and the number of revolutions of the spiral are Exactly the same,
Only the rotation directions of the spiral blades 74 and 78 can be made different, and the transport directions can be opposite to each other.

However, in this embodiment, while the developer transport amounts of the first stirring and transporting means 68 and the second stirring and transporting means 70 are substantially equal, the size of the spiral blades 74 and 78 (in this embodiment, the outer Diameter) and the blades 74, 7
The number of rotations of 8 is set different, and the developer transport speed (V2) of the second stirring and transporting unit 78 is set to be faster than the developer transporting speed (V1) of the first stirring and transporting unit 68. Specifically, the outer diameter of the spiral blade 74 of the first stirring and conveying means 68 is φ20 mm, and the number of rotations is 161 rpm.
m, the outer diameter of the spiral blade 78 of the second stirring and conveying means 70 is φ16 mm, the number of revolutions is 225 rpm, and the spiral pitch is both 15 mm.

As a result, the first toner replenishment is performed.
The stirring and conveying means is conveyed from left to right in the figure while stirring slowly, and the toner and the carrier are mixed and stirred for a sufficient time to ensure an appropriate and uniform toner concentration,
As a developer having sufficient charge, the second toner is used.
It can be supplied to the stirring and conveying means. On the other hand, in the second stirring and conveying means, by increasing the developer conveying speed, the developer on the surface of the sleeve 148, whose toner concentration has been reduced by the development, is combined with the other developer present in the second stirring and conveying means. While mixing and stirring quickly, the second stirring and conveying means is moved to the pumping area provided at the short part of the second stirring and conveying means. As a result, the first
The developer can be promptly replaced with a developer having an appropriate toner concentration supplied from the stirring and conveying means.

More specifically, the size of the spiral blade formed in the second stirring and conveying means is made smaller than that of the first stirring and conveying means, and conversely, the second stirring and conveying means 68
By setting the rotation speed of the stirring and conveying means 70 to be high (setting the gear ratio of the gears 75 and 81 described above), the conveyance speed can be changed without changing the conveyance amount of the developer. At this time, the size of the spiral blade and the number of rotations of the stirring and conveying means are limited as long as the function is achieved as described above.
Can be set arbitrarily. However, if the rotation speed of the second stirring and conveying means is set to an excessively high number, the stress is applied to the developer, so that the first stirring and conveying means is 1.1 to 2 times, preferably 1.1 to 1.times. It is desirable to set the speed higher in the speed range of about five times.

[Developer Scavenging Means, Dropping Means, and Arrangement Thereof] Next, the developer scavenging means, falling means, and their arrangement will be described. First, the developer pumping means 82 will be described in detail. As described above, the developer pumping means 82
The first stirring / transporting means 68 and the second stirring / transporting means 70 are disposed on the side of the front wall 138 of the developing housing at substantially the center in the vertical direction of the stirring / transporting means 68 and the second stirring / transporting means 70.

More specifically, referring to FIG.
Reference numeral 2 denotes a magnetic roller (pumping roller 86) disposed on the front side (left side in FIG. 5) of the developing housing 144, as shown in FIG. 5, which is outside the region of the developing sleeve 148, that is, in the axial direction. It is arranged outside the development area that effectively contributes to development. The pumping means 82 is rotatably mounted on a front wall 138 and a second rear wall 83 of the developing housing 144 by a rotation shaft 84. The rotation shaft 84 projects to the left of the front wall 138, and the gear 88 is fixed to this projection. The gear 88 is screwed with the gear 80 attached to the rotating shaft of the first stirring and conveying means. A pumping roller 86 is fixed to the rotating shaft 84. The pumping roller 86 is formed in a solid cylindrical shape from iron as a magnetic material over substantially the entire area in the axial direction, and N poles and S poles having a magnetic force of, for example, 800 G gauss are alternately arranged in the circumferential direction so that a total of four poles are provided. Eight poles are magnetized over the entire area in the axial direction.

On the other hand, the developer dropping means is positioned at the right end of the first stirring and conveying means 68 and the second stirring and conveying means 70 in the drawing, and the first and second stirring and conveying means integrally formed with the developing housing. Rear wall 14 of partition 66 isolating means
The opening provided in the partition wall 66 located on the 0 side, more specifically, on the rear wall 140 side end of the first stirring and conveying means 70. The opening position is located on the right side (outside the effective development area) of the developer supply means 146 (development sleeve 148) with respect to the effective development area D described above.

On the left side of the opening 200 in the drawing, that is, on the side where the developer is carried by the first stirring and conveying means 68, a rib as a closing means for closing the developer 100 from the partition wall 66. 210 are provided. As shown in FIG. 2 (b), the rib 210 is formed above the rotating shaft 72 of the first stirring and conveying means 68, and in this embodiment, the spiral of the first stirring and conveying means 68 The height is approximately 80% of the outer diameter of the blade 74. Due to the presence of the rib 210, the developer 100 conveyed by the first stirring / conveying means 68 is temporarily blocked, and the ribs 210 are centered on the cutout portion 205 formed on the rotation shaft portion of the first stirring / conveying means 68. The developer 100 invades the opening 200 so as to get over the 210,
As a result, the developer 100 is efficiently dropped on the spiral blade 78 about the rotation shaft 76 of the second stirring and conveying means 70.

As described above, since both the developer pumping means 82 and the developer dropping means 200 are disposed outside the effective development area D, the developer 100 stays at both ends of the effective development area D of the developer supply means 146. Can be reliably prevented. That is,
The developer 100 is partially blocked by a rib 210 at the downstream end of the first stirring / conveying means 68, and the overflowed developer 100 is supplied to the dropping means 200. The developer 100 is supplied in a state where the pulsation of the developer 100 conveyed in the first stirring and conveying means 68 is eliminated. As a result, the developer 100 can be quickly conveyed to the left in the drawing without staying in the second stirring and conveying means 70 immediately below the dropping means 200. As a result, in the second stirring and conveying means 70,
At the right end in FIG. 5 of the effective development area D, the developer 100 in a state where the stirring and conveying is smoothly progressing is positioned. Scattering can be effectively prevented.

[Driving Connection Mechanism and Developer Circulation Path by Longitudinal Circulation] FIG. 6 shows the driving connection of gears on the rear surface of the developing device, and FIG. 7 shows the driving connection of gears on the front surface of the developing device. The description will be continued with reference to FIGS. Drive from a drive source (not shown) is output gear 1
54, the gears 81, 7
5 is transmitted. The driving force transmitted to the gear 75 is transmitted to the gears 80 and 88 through the rotation shaft 72. On the other hand, when the drive from the drive source is transmitted to the output gear 154, it is also transmitted to the idle gear 156 and the input gear 152. As a result, the first stirring and conveying means 68 is rotated in the direction indicated by the arrow 90 in FIGS. 3 and 4, and the second stirring and conveying means 70 is rotated in the direction indicated by the arrow 92 in FIG. Further, the pumping means 82 is rotated in a direction indicated by an arrow 94.

As shown in FIG. 3, the developing housing 14
4 stores a developer 100 including a toner and a carrier. More specifically, the first developer 100 is regulated by the partition wall 66 and the first stirring / transporting means 68 is provided.
Of the stirring area 102, and the lower side of the partition wall 66, and
The developing means 146 and the second
Second stirring area 10 in which stirring and conveying means 70 is provided.
4, and a third stirring / transporting means 68, a second stirring / transporting means 70 and a pumping means 82 as shown in FIG.
Are dispersed and accommodated in a stirring area (pumping area) 106.

The rotating shaft 72 of the first stirring and conveying means 68 is rotated in the direction shown by the arrow 90, and the developer 100 is stirred and mixed in the first stirring area 102 in FIG. It is conveyed in the direction indicated by 108.

The rotation shaft 76 of the second stirring and conveying means 70 is rotated in the direction shown by the arrow 92, and the developer 100 is stirred and mixed in the second stirring area 104 as shown by the arrow 110 in FIG. Transported from upstream to downstream in the direction. At this time, a part of the developer 100 is supplied from the second stirring / conveying means 70 to the developer supply means 146, and further from the developer supply means 146 to the developing area of the photosensitive drum 28 which rotates in the direction indicated by the arrow 147. Is supplied to form a toner image.

Next, the path through which the developer 100 is stirred, mixed, conveyed and circulated will be described in detail. First, in the first stirring area 102, the developer 100 is conveyed while being stirred and mixed in the direction indicated by an arrow 108 in FIG. You. At this time, the first stirring area 102
A rib 210 is provided at the downstream end of the developer, where the developer is partially blocked. As a result, a sufficient amount of developer is always secured at this end, and the toner concentration of the developer 100 is monitored by the toner concentration detecting means provided at this position. An opening 200 is provided in the partition wall 66 in an area A1 formed on the downstream side of the rib 210, and constitutes a dropping unit 200. Therefore, the developer 100 stirred and conveyed by the spiral blades 74 of the first stirring and conveying means 68 climbs over the gap between the rib 210 and the rotating shaft 72 (about 1 mm in this embodiment) and the rib 210 and moves downward by its own weight. To fall. Dropped developer 100
5, while being stirred and mixed in the second stirring area 104 by the action of the second stirring and conveying means 70, the arrow 1 in FIG.
It is conveyed in the direction shown by 10, and is conveyed to the downstream end part, ie, the area | region A2 of the left end part in FIG. Left end (Area A2)
Since the spiral blade 78 of the second stirring / conveying means 70 is not provided, it is not further conveyed to the downstream side, and is then pumped in the pumping area 106 by the action of the developer pumping means 82. The roller 86 attracts the developer 100 to the peripheral surface by magnetic force and is pumped up.

On the other hand, in the pumping area 106, the partition wall 6 extends across the entire width of the pumping roller 86 in the vertical center of the first stirring and conveying means 68 and the second stirring and conveying means 70.
6 is provided with an opening, and the developer 100 is transferred from the second stirring and conveying means 70 to the pumping roller 86 and the first stirring and conveying means 68.
Is allowed to flow. The partition wall 66 between the first stirring / transporting means 68 and the second stirring / conveying means 70 serves as an isolation wall 112 which blocks the flow of the developer in the vertical direction of the two stirring / transporting means. The distal end 113 of the isolation wall 112 is formed in an acute angle shape,
The gap with the surface of the pumping roller 86 is set to 1.0 mm. Further, the developer 1 adhering to the surface of the suction roller 86
At 00, a magnetic brush is formed as shown in FIG. More specifically, the developer 1 is applied to the magnetized regions of the N pole and the S pole.
The ears formed by 00 are long and the ears are formed low in the central region between the N pole and the S pole. In the present embodiment, N
Since the pole and the S pole are provided alternately and four poles each,
There is no zero Gaussian area, and therefore the developer pumping means 82
, The pumping force (conveying force) of the developer 100 can be increased.

The rotation of the pumping roller 86 in the direction indicated by the arrow 94 causes the magnetic brush to rotate in the same direction.
Is separated from the surface of the pumping roller 86 at the tip of the separating wall 112. The peeled developer 100 is moved onto the separating wall 112, and is stirred and conveyed in the direction indicated by the arrow 108 in FIG. 5 by the rotation of the spiral blade 74 of the first stirring and conveying means 68. Thereafter, the developer 100 is stirred, mixed, transported, and circulated repeatedly as described above.

In this example, a resin-coated ferrite carrier having a center particle size of 60 μm and a center particle size of 8.
From a toner containing a color pigment and various additives in a polyester resin of 5 μm, a two-component developer is prepared by using a toner having a toner concentration of 4 to 5
By using the above-described spirals having different diameters and controlling the rotation speeds of the two, the first and second stirring / conveying means 68 and 70 have a developer conveying force of 1120.
The developer conveying force of the pumping means 82 (length 27 mm) is set to 1350 g / min. That is, the developer conveying force of the developer pumping means 82 is set to be larger than the conveying force of the first and second stirring and conveying means. In this way, the developer transported to the pumping area by the second stirring / transporting means 68 can be pumped to the first stirring / transporting means 70 without staying. Note that the conveying force of the pumping means 82 is equivalent to the first and second stirring and conveying means 6.
It is sufficient if it is large with respect to the conveying force of the first and second stirring and conveying means 68 and 70.
Can be used up to a range.

In this way, while being stirred and mixed in the second stirring area 104 by the action of the second stirring and conveying means 70, the sheet is conveyed in the direction indicated by the arrow 110 in FIG.
The developer 100 conveyed to the downstream end, that is, the left end area A2 in FIG. , And can be reliably and quickly supplied to the left end of the first stirring and transporting means 68 located above. Therefore, stagnation and solidification of the developer 100 are prevented, and reliable and favorable stirring and conveying are repeated.

On the other hand, at the downstream end of the first stirring / conveying means 68, the toner concentration detector 230 for detecting the toner concentration in the developer 100 is provided as described above. The toner concentration detector detects the toner concentration by detecting, for example, the magnetic permeability in the developer 100. Then, the toner concentration detector 230 detects that the developer 10
When it is determined that the toner density of 0 is low, the toner supply means (not shown) automatically supplies the toner upstream of the first stirring and conveying means, in a shaded area C in FIG. When the predetermined value is reached, the supply of the toner is stopped. As a result, the toner density in the developing housing 30 can be maintained within a required range, and the development with a predetermined density can be performed.

It should be noted that the toner supply is replenished in the area C because the length of the first stirring and conveying means 68 is effectively used, and sufficient replenished toner is given sufficient mixing and stirring time to reduce the triboelectric charge. This is for giving sufficient. In addition, by providing the area C at the right end in FIG. 5 of the pumping unit 82 (downstream of the pumping unit 82 when viewed in the transport direction of the developer 100), the first stirring and transporting unit 68 moves rightward in FIG. Since new toner can be replenished to the developer 100 that has started to move, the mixing with the developer is extremely smoothly performed. The spiral blade 74 of the first stirring and conveying means located in the toner replenishing area C is provided with a rib 220 over one pitch to promote mixing and stirring of the replenished toner and developer. ing.

In the above embodiment, the developer pumping means 82 is composed of the first stirring and conveying means 68 and the second stirring and conveying means 70.
Although the arrangement on the right side in the front view (see FIG. 4) is exemplified, it is also possible to arrange the arrangement on the left side in the front view. In this case, the area where the developing sleeve does not exist in the axial direction area is effectively used. It can be used, and the length in the width direction (left-right direction in FIG. 4) can be further reduced. In this way, when the developing device of the present invention is applied to a color printer having a four-tandem developing device as the image forming device, the width of the color printer body as the image forming device can be reduced. Become.

In the above embodiment, the developer scooping means 82 does not have a sleeve around the scooping roller 84, and the length in the width direction as viewed from the front as the developer scavenging means 82 is reduced as much as possible. Although the width is slightly widened, a configuration in which a sleeve is provided is also possible.

[0055]

As described above, according to the present invention, the first and second stirring and conveying means can be effectively used by disposing both the developer pumping means and the dropping means outside the effective developing area of the developer supply means. It can be used for agitation and transport over the entire development area. Moreover, a rib as a closing means is provided at the downstream end of the first stirring and conveying means and at a boundary portion with the dropping means, and a part of the developer is closed, so that the size of the developing means can be reduced without increasing the size of the developing device. Can be arranged outside the effective development area.

[0056]

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an image forming apparatus according to the present invention.

2A and 2B are diagrams illustrating an internal mechanism of the developing device, wherein FIG. 2A is a perspective view as viewed from a developer supply device side, and FIG.
FIG. 2 is a partially cutaway perspective view seen from the back side of the figure.

FIG. 3 is a sectional view taken along line AA in FIG. 2 (b).

FIG. 4 is a sectional view taken along line BB in FIG. 2 (b).

FIG. 5 is a schematic diagram showing a positional relationship between components.

FIG. 6 is a diagram illustrating a drive connection of a gear on a rear surface of the developing device.

FIG. 7 is a diagram illustrating a drive connection of a gear on a front surface of the developing device.

[Explanation of symbols]

 28 photosensitive drum 30 developing device 68 first stirring and conveying means 70 second stirring and conveying means 74 and 78 spiral blades 82 developer scavenging means 86 scooping roller (rotating body) 100 developer 146 Developer supply means 200: developer drop means 210: blocking means D: effective development area

Claims (6)

[Claims] A developer supply means for supplying a developer to the latent image carrier to visualize the developer; and a first means provided near the developer supply means for stirring the developer and transporting the developer in a predetermined direction. A stirring / conveying means, a second stirring / conveying means provided below the first stirring / conveying means for stirring the developer and conveying the developer in a direction opposite to the first stirring / conveying means; The developing device includes a developer pumping unit that supplies a certain developer to the first stirring and conveying unit, and a developer dropping unit that supplies the developer in the first stirring and conveying unit to the second stirring and conveying unit. The developer pumping means and the developer dropping means are provided outside the effective developing area of the developer supply means, respectively, and are provided between the developer dropping means and the first stirring and conveying means for closing the developer. A developing device having a stopping means. 2. The developer pumping means is a rotating body having a plurality of magnetic poles in a circumferential direction provided at a substantially central portion in a height direction of the first stirring and conveying means and the second stirring and conveying means. The developing device according to claim 1. 3. The developer dropping means is provided on a partition wall which divides an upper chamber accommodating the first stirring / conveying means and a lower chamber accommodating the second stirring / conveying means. The developing device according to claim 1, wherein the opening is provided. 4. The developing apparatus according to claim 1, wherein said first and second stirring and conveying means have a blade member formed in a spiral shape in a longitudinal direction on a rotatable shaft peripheral surface. 5. The developing device according to claim 4, wherein the developer conveying speed of said second stirring and conveying means is set higher than that of said first stirring and conveying means. 6. The developing device according to claim 7, wherein the outer diameter of the blade member of the second stirring and conveying means is smaller than the outer diameter of the blade member of the first stirring and conveying means. .